EPA-600/3-78-008
January 1978
Ecological Research Series
*" ''"*' ~4> f' - < % •»'
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U S Environmental
Protection Agency, have been grouped into nine series These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields
The nine series are
1. Environmental Health Effects Research
2 Environmental Protection Technology
3 Ecological Research
4 Environmental Monitoring
5. Socioeconomic Environmental Studies
6 Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8 "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ECOLOGICAL RESEARCH series This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-78-008
January 1978
SUMMARY ANALYSIS OF THE NORTH AMERICAN (US PORTION)
OECD EUTROPHICATION PROJECT: NUTRIENT LOADING - LAKE RESPONSE
RELATIONSHIPS AND TROPHIC STATE INDICES
by
Walter Rast
and
G. Fred Lee
Center for Environmental Studies
The University of Texas at Dallas
Richardson, Texas 75080
Contracts No. R-803356-01-0
and No. R-803356-01-3
Project Officers
Norbert Jaworski and Jack H. Gakstatter
Corvallis Environmental Research Laboratory
Corvallis, Oregon 97330
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
US ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
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DISCLAIMER
This report has been reviewed by the Corvallis Environmental
Research Laboratory, U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the con-
tents necessarily reflect the views and policies of the U.S. En-
vironmental Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or recommendation
for use.
'7
ii
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FOREWORD
Effective regulatory and enforcement actions by the Environ-
mental Protection Agency would be virtually impossible without
sound scientific data on pollutants and their impact on environ-
% mental stability and human health. Responsibility for building
' this data base has been assigned to EPA's Office of Research
and Development and its 15 major field installations, one of
» which is the Corvallis Environmental Research Laboratory (CERL).
The primary mission of the Corvallis Laboratory is research
^ on the effects of environmental pollutants on terrestrial, fresh-
water, and marine ecosystems; the behavior, effects and control
, of pollutants in lake systems; and the development of predictive
'v" models on the movement of pollutants in the biosphere.
<-o
^ This report provides an extensive examination of relation-
fx. ships between nutrient inputs and lake responses and, therefore,
» should be extremely valuable to those people concerned with lake
management and controlling accelerated lake eutrophication.
A.F. Bartsch
Director, CERL
111
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PREFACE
Several years ago the Organization for Economic Cooperation
and Development (OECD) member countries, including the USA, ini-
tiated a eutrophication study with the primary objective of formu-
lating the relationships between aquatic plant nutrient loadings
to lakes and impoundments and the response of these water bodies
to these loadings. Emphasis was on the development of relation-
ships that could be used to identify critical aquatic plant
nutrient (i.e. nitrogen and phosphorus) loadings in order to avoid
or minimize water quality problems caused by excessive fertiliza-
tion (eutrophication). In the majority of the participating
countries, the OECD eutrophication study caused the initiation of
field studies, using the same or similar sampling techniques and
analytical methods, to assess aquatic plant nutrient loadings
to a water body and its response to these loadings. In the US,
however, the lack of funds to initiate comparable studies of US
water bodies limited the United States' participation in the
overall study. The US EPA did, however, provide small grants to
enable investigators who had already conducted nutrient load-
response studies in US water bodies to develop a report of their
studies which emphasized nutrient load-lake response relationships
in accord with overall OECD Eutrophication Program objectives and
format. Funds were also provided by the US EPA to prepare this
summary report. This report represents an initial analysis of
the results of the US portion of the North American Project of
the OECD eutrophication study.
The goal of the OECD eutrophication study is the quantifica-
tion of the relationships between nutrient loading and trophic
response in lakes and impoundments. Attention in this initial
analysis has been focused mainly on evaluation of the nutrient
loading portion of this relationship, especially as these nutrient
loadings are related to the critical nutrient loading levels
and the trophic response of the US OECD water bodies, using the
Vollenweider phosphorus and nitrogen loading diagrams. This re-
port also evaluates the nutrient sources, nutrient budget calcula-
tion methodologies, and nutrient loading estimates reported by
the US OECD investigators for their respective water bodies.
The US OECD water body nutrient loadings have been evaluated
several ways, including: (1) several relationships developed by
Vollenweider, (2) comparison with calculated nutrient loadings
based on watershed nutrient export coefficients and land usage
patterns within the watershed, and (3) other nutrient loading-
IV
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lake response relationships developed by Vollenweider, Dillon,
and Larsen and Mercier. In addition, an attempt was made in this
summary report to formulate some of the relationships between
nutrient load-lake and impoundment water quality responses,
based on the data available for the US OECD water bodies.
This report also presents a discussion of the application
of the US OECD eutrophication study results for predicting the
changes in water quality that will arise from altering the phos-
phorus input to lakes and impoundments. The US OECD water bodies
are ranked in accord with various previously proposed trophic
status index systems. A new trophic status index system based
on a modification of the Vollenweider phosphorus loading relation-
ships is presented. A modified Vollenweider phosphorus loading
relationship has been developed which enables individuals con-
cerned with water quality management to select the appropriate
phosphorus loadings for achieving a desired level of chlorophyll,
water clarity, and hypolimnetic oxygen depletion rate.
Upon completion of this study a copy of those sections of
the report pertinent to each investigator's water bodies was sent
to the investigators and a request was made for them to review
and comment on these sections. Approximately half of the US
OECD eutrophication study investigators responded to this request,
In the two years from the time that the US OECD eutrophication
investigators had provided the data which served as the basis
of this report and the completion of this report, several in-
vestigators have done additional work on their respective water
bodies. The new data was brought to the authors' attention as
part of the review process. In most cases the changes in the
data were relatively minor and did not change the conclusions
of the report. In others, major changes in the nutrient loads
for their water body were reported, under conditions where the
investigator indicated that the new data more reliably
estimated the nutrient loads and should be used instead of the
ones reported previously.
All suggested changes of the investigators have been
noted in this report and in the appendices. Major changes have
been used as a basis for rewriting sections of this report.
This situation will cause differences between the data presented
in the investigator's report published as a companion volume,
and the data presented in this report.
v
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ABSTRACT
The US participation in the OECD Eutrophication Program
consisted of having 20 investigators prepare reports on the
nutrient load-lake and impoundment response relationships for
their respective water bodies. This report presents a critical
review of these overall relationships with particular emphasis
given to evaluation of the Vollenweider nutrient load-trophic
state formulations. This review includes consideration of the
nutrient load response relationships for 38 water bodies, or
parts of water bodies, located throughout the US, with the pre-
ponderance located in the northern half of the US. It has been
found that the Vollenweider nutrient load relationship involving
water body mean depth, hydraulic residence time and phosphorus
load correlates well with the trophic states assigned by the US
OECD eutrophication study investigators.
A good correlation has also been found between phosphorus
loading, normalized as to hydraulic residence time and mean
depth, and the average chlorophyll and water clarity (as measured
by Secchi depth) for the US OECD water bodies. In general,
phosphorus and nitrogen loads to US OECD water bodies were within
a factor of + two of the loads predicted on the basis of average
nutrient concentrations within the water bodies and on the land
use patterns within the water body watersheds. Generalized
nutrient export coefficients have been developed in this study,
enabling estimates of nutrient loads to be made on the basis
of land use patterns within the watershed.
The relationships developed in this study can be used to pre-
dict the improvement in water quality that will result from a
change in the phosphorus load to a water body for which phos-
phorus is the key chemical element limiting planktonic algal
growth. The US OECD water bodies all show approximately the
same trophic status when evaluated by several recently-proposed
trophic state index systems. A new trophic state index system
has been developed in this study which is based on the relation-
ship between the actual phosphorus loading and permissible phos-
phorus loading as defined in the Vollenweider phosphorus loading
and mean depth/hydraulic residence time relationship. This
relationship has been modified to enable water quality managers
to determine the appropriate phosphorus load for a particular
water body in order to yield a certain chlorophyll content from
planktonic algae and its corresponding water clarity. It is
recommended that these relationships be used as a basis for
vi
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establishing critical phosphorus loads to lakes and impoundments.
This report was submitted in fulfillment of Contract No.
R-803356-01-0 and Contract No. R-803356-01-3 under the sponsor-
ship of the U.S. Environmental Protection Agency. Work was
completed as of August, 1977.
VII
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CONTENTS
Foreword iii
Preface iv
Abstract vi
Figures xii
Tables xviii
Acknowledgment xxi
I. Introduction i
II. Conclusions 3
III. Recommendations 6
IV. Organization for Economic Cooperation and
Development 8
Water Management Sector Group 10
OECD International Cooperative Program
for Monitoring of Inland Waters 12
Objectives of Study 12
Common Measurement System 13
Regional Approach 13
V. US OECD Eutrophication Study 18
General Characteristics of US OECD Water
Bodies 23
Data Reporting Methodology 30
US OECD Eutrophication Study and Other
US Eutrophication Control Programs 31
National Eutrophication Survey 31
Public Law 92-500 31
Use of N:P Ratios in Determining the Aquatic
Plant Growth Limiting Nutrient in Natural Waters... 32
The Limiting Nutrient Concept 32
Nitrogen and Phosphorus as Limiting Nutrients .. 33
Interaction Between Biotic and Abiotic
Factors in Determining Limiting Nutrient
and Algal Nutrient Stoichiometry 36
The Limiting Nutrient Concept as Applied in
The US OECD Eutrophication Study 39
Aquatic Plant Limitation in US OECD Water
Bodies 47
Approaches Used in US OECD Eutrophication
Study 50
Initial Vollenweider Phosphorus and
Nitrogen Loading Diagrams 50
Vollenweider Phosphorus Loading and
Nitrogen Loading and Mean Depth/Hydraulic
Residence Time Relationships 55
viii
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Emphasis on Phosphorus Loading
Relationship 63
Vollenweider Critical Phosphorus Loading
Equations 63
Vollenweider Phosphorus Loading Characteristics
and Mean Epilimnetic Chlorophyll a Relationship.. 67
Dillon Phosphorus Loading-Phosphorus
Retention and Mean Depth Relationship 70
Larsen and Mercier Influent Phosphorus
and Phosphorus Retention Relationship 74
VI. Results of the Initial Analysis of US OECD
Eutrophication Study Data 79
Sampling and Measurement Methodologies 79
Nutrient Load Calculation Methodologies 80
Methods for Evaluation of Estimate of US
OECD Water Body Nutrient Loadings Ill
Vollenweider Mean Phosphorus/Influent
Phosphorus and Hydaulic Residence
Time Relationship 118
Watershed Land Use Nutrient Export
Coefficients 125
Comparison of Phosphorus Loadings Derived
From Vollenweider Relationship with
Loadings Derived From Watershed Phos-
phorus Export Coefficient 139
VII. US OECD Eutrophication Study Phosphorus Data: 147
As Applied in Initial Vollenweider Phosphorus
Loading and Mean Depth/Hydraulic Residence
Time Relationship; ' 147
As Applied in Modified Vollenweider
Phosphorus Loading Mean Depth/Hydraulic Residence
Time Relationship; 153
As Applied in Phosphorus Residence Time
Model; 160
As Applied in Vollenweider Equation for
Critical Phosphorus Loading 169
Comparison of Results : 170
Discrepancies Between Vollenweider
Phosphorus Loading Diagram and
Vollenweider Mean Phosphorus/Influent
Phosphorus and Hydraulic Residence
Time Diagram 175
Lake Waldo .- 175
Lake Weir 177
Lower Lake Minnetonka 178
Twin Lakes - 1973 and 1974 179
Potomac Estuary and Lake of the Isles 180
Lake Stewart, Lake Virginia and
Twin Valley Lake 181
Kerr Reservoir 183
Discrepancies Between Vollenweider
Phosphorus Loading Diagram and Watershed
Phosphorus Export Coefficient Calculations 184
ix
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Dogfish Lake, Lamb Lake and
Meander Lake 134
Lake Tahoe 185
Lake Sallie 186
VIII. US OECD Eutrophication Study Nitrogen Data: 187
As Applied in Vollenweider Nitrogen Loading
and Mean Depth/Hydraulic Residence Time
Relationship 187
Comparison of Results :
Discrepancies Between Investigator-
Indicated Nitrogen Loadings and Water-
shed Nitrogen Export Coefficient
Calculations 190
Lake Sallie 191
Lake Tahoe , 191
Lake Sammamish, Lake Cayuga and '
Twin Lakes 192
IX. US OECD Data Applied in Other Nutrient
Relationships 193
US OECD Phosphorus Data Applied in
Vollenweider's Phosphorus Loading Character-
istics and Mean Chlorophyll Relationship 193
US OECD Phosphorus Data Applied in
Phosphorus Loading and Secchi Depth
Relationship 201
US OECD Phosphorus Data Applied in Dillon's
Phosphorus Loading-Phosphorus Retention
and Mean Depth Relationship 202
US OECD Phosphorus Data Applied in Larsen
and Mercier's Influent Phosphorus and
Phosphorus Retention Relationship 211
X. Correlations Between Nutrient Loadings and
Eutrophication Response Parameters 217
Phosphorus Loadings 221
Nitrogen Loadings 232
Mean Total and Dissolved Phosphorus
Concentrations 244
Mean Inorganic Nitrogen Concentrations 262
Other Correlations Between Eutrophication
Response Parameters 267
XI. Application of US OECD Results for Predicting
Changes in Water Quality as a Result of Altering
Nutrient Inputs 281
Application of Results for Assessing Water
Quality in the Great Lakes and Impoundments 297
Application of Results to Implementation of
Section 314-A of PL 92-500 311
An Approach for the Use of the Vollenweider
Nutrient Load-Water Quality Program 314
XII. Trophic Status Index Study 320
General Considerations ^20
Requirements for a Trophic Status
Classification Index 323
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Current Trophic Status Classification
Indices 324
US EPA Trophic Status Index System 324
Carlson Trophic Status Index System 326
Piwoni and Lee Trophic Status Index System 328
Rast and Lee Trophic Status Index Systems 330
Trophic Status Indices as Applied to the
US OECD Water Bodies 335
US EPA Trophic Status Index System 335
Carlson Trophic Status Index System 342
Piwoni and Lee Trophic Status Index System 348
Rast and Lee Trophic Status Index Systems 348
XIII . Discussion 368
References 380
Appendices
I. US OECD Final Report Outline 400
II. Data Summary Sheets for US OECD
Water Bodies 403
Glossary 453
XI
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FIGURES
Number Page
1 Organizational Structure of OECD ..................... 9
2 Organizational Structure of OECD Environment
Committee ............................................ 11
3 Organizational Outline of OECD Eutrophication Study . . 16
4 Locations of US OECD Water Bodies .................... 22
5 Vollenweider ' s Total Phosphorus Loading and Mean
Depth Relationship ................................... 52
6 Vollenweider ' s Total Nitrogen Loading and Mean
Depth Relationship ................................... 53
7 Initial Vollenweider Total Phosphorus Loading and
Mean Depth/Hydraulic Residence Time Relationship ..... 58
8 Modified Vollenweider Total Phosphorus Loading and
Mean Depth/Hydraulic Residence Time Relationship ..... 62
9 Vollenweider Critical Phosphorus Loading and Mean
Depth Relationship ............... • .................... 68
10 Vollenweider Critical Phosphorus Loading and
Hydraulic Loading Relationship ..................... . . 69
11 Vollenweider Phosphorus Loading Characteristics and
Mean Chlorophyll a Relationship ...................... 71
12 Dillon Phosphorus Loading-Phosphorus Retention and
Mean Depth Relationship
13 Larsen and Mercier Influent Phosphorus and
Phosphorus Retention Relationship .................... 78
14 Evaluation of Estimates of US OECD Water Body Nutrient
Loadings: Vollenweider Mean Phosphorus/Influent
Phosphorus and Hydraulic Residence Time Relationship.. 124
xii
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Number Page
15 Evaluation of Estimates of US OECD Water Body
Nutrient Loadings: Watershed Land Use Phosphorus
Export Coefficient Calculations 140
16 Evaluation of Estimates of US OECD Water Body
Nutrient Loadings: Watershed Land Use Nitrogen
Export Coefficient Calculations 141
17 Comparison of Phosphorus Loadings Derived from
Watershed Export Coefficients with Loadings Derived
From Vollenweider Mean Phosphorus/Influent
Phosphorus and Hydraulic Residence Time Relationship ... 145
18 US OECD Data Applied to Initial Vollenweider
Phosphorus Loading and Mean Depth/Hydraulic
Residence Time Relationship 148
19 US OECD Data Applied to Modified Vollenweider
Phosphorus Loading and Mean Depth/Hydraulic Residence
Time Relationship 154
20 Comparison of Permissible and Excessive Loading Lines
in Initial and Modified Vollenweider Phosphorus Loading
Diagram 155
21 US OECD Data Applied to Vollenweider Nitrogen 'Loading
and Mean Depth/Hydraulic Residence Time Relationship..... 189
22 US OECD Data Applied to Vollenweider Phosphorus Loading
Characteristics and Mean Chlorophyll a Relationship 199
23 US OECD Data Applied to Phosphorus Loading and Secchi
Depth Relationship (Log-Log Scale) 203
24 US OECD Data Applied to Phosphorus Loading and Secchi
Depth Relationship (Semilog Scale) 204
25 US OECD Data Applied to Dillon Phosphorus Loading-
Phosphorus Retention and Mean Depth Relationship 206
26 US OECD Data Applied to Larsen and Mercier Influent
Phosphorus and Phosphorus Retention Relationship 212
27 Phosphorus Loading and Mean Chlorophyll a Relationship
in US OECD Water Bodies 7. ' 222
28 Phosphorus Loading and Mean Secchi Depth Relationship
in US OECD Water Bodies 223
29 Phosphorus Loading and Mean Total Phosphorus Relationship
in US OECD Water Bodies 225
xiii
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Number
30 Phosphorus Loading and Mean Dissolved Phosphorus
Relationship 226
31 Phosphorus Loading and Primary Productivity
Relationship 227
32 Phosphorus Loading and Total Primary Production
Relationship 228
33 Phosphorus Loading and Growing Season Epilimnetic
Chlorophyll a Relationship 229
34 Phosphorus Loading and Growing Season Epilimnetic
Total Phosphorus Relationship 230
35 Phosphorus Loading and Growing Season Epilimnetic
Dissolved Phosphorus Relationship 231
36 Phosphorus Loading and Growing Season Epilimnetic
Primary Productivity Relationship 233
37 Phosphorus Loading and Spring Overturn Total
Phosphorus Relationship 234
38 Nitrogen Loading and Mean Chlorophyll a Relationship.... 235
39 Nitrogen Loading and Mean Secchi Depth Relationship 236
4-0 Nitrogen Loading and Mean Inorganic Nitrogen
Relationship 237
41 Nitrogen Loading and Primary Productivity Relation-
ship 239
42 Nitrogen Loading and Total Primary Production
Relationship 240
43 Nitrogen Loading and Growing Season Epilimnetic
Chlorophyll a Relationship 241
44 Nitrogen Loading and Growing Season Epilimnetic
Inorganic Nitrogen Relationship 242
45 Nitrogen Loading and Growing Season Epilimnetic
Primary Productivity Relationship 243
46 Nitrogen Loading and Spring Overturn Inorganic
Nitrogen Relationship 245
47 Mean Total Phosphorus and Mean Chlorophyll a
Relationship 7 246
xiv
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Number Page
4-8 Mean Total Phosphorus and Mean Secchi Depth
Relationship 247
49 Mean Total Phosphorus and Mean Dissolved Phosphorus
Relationship 249
50 Mean Total Phosphorus and Primary Productivity
Relationship 249
51 Mean Total Phosphorus and Growing Season Epilimnetic
Chlorophyll a Relationship 250
52 Mean Total Phosphorus and Growing Season Epilimnetic
Primary Productivity Relationship 251
53 Mean Total Phosphorus and Spring Overturn Total
Phosphorus 252
54 Growing Season Epilimnetic Total Phosphorus and
Growing Season Epilimnetic Chlorophyll a Relationship... 253
55 Growing Season Epilimnetic Total Phosphorus and
Growing Season Epilimnetic Primary Productivity
Relationship 255
56 Spring Overturn Total Phosphorus and Growing Season
Epilimnetic Chlorophyll a Relationship 256
57 Spring Overturn Total Phosphorus and Growing Season
Epilimnetic Total Phosphorus Relationship 257
58 Spring OVerturn Total Phosphorus and Growing Season
Epilimnetic Dissolved Phosphorus Relationship 258
59 Mean Dissolved Phosphorus and Mean Chlorophyll a
Relationship 7 259
60 Mean Dissolved Phosphorus and Primary Productivity
Relationship 260
61 Mean Dissolved Phosphorus and Spring Overturn
Dissolved Phosphorus Relationship 261
62 Growing Season Epilimnetic Dissolved Phosphorus and
Growing Season Epilimnetic Chlorophyll a Relationship... 263
63 Spring Overturn Dissolved Phosphorus and Growing Season
Epilimnetic Chlorophyll a. Relationship 264
64 Spring Overturn Dissolved Phosphorus and Growing Season
Epilimnetic Dissolved Phosphorus Relationship 265
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Number Page
65 Mean Inorganic Nitrogen and Mean Chlorophyll a
Relationship 266
66 Mean Inorganic Nitrogen and Mean Secchi Depth
Relationship 268
67 Mean Inorganic Nitrogen and Primary Productivity
Relationship 269
68 Mean Inorganic Nitrogen and Growing Season Epilmnetic
Chlorophyll a Relationship 270
69 Mean Inorganic Nitrogen and Growing Season Epilmnetic
Primary Productivity Relationship 271
70 Growing Season Epilimnetic Inorganic Nitrogen and
Growing Season Epilmnetic Chlorophyll a Relationship.... 272
71 Growing Season Epilimnetic Inorganic Nitrogen and
Growing Season Epilimnetic Primary Productivity
Relationship 273
72 Primary Productivity and Mean Chlorophyll a
Relationship 7 274
73 Primary Productivity and Mean Secchi Depth
Relationship 276
74 Growing Season Primary Productivity and Growing
Season Mean Chlorophyll a Relationship 277
75 Mean Daily Productivity and Mean Chlorophyll a
Relationship 278
76 Mean Daily Primary Productivity and Mean Areal
Chlorophyll a Relationship 279
77 Secchi Depth and Chlorophyll a_ Relationship in
Natural Waters (Linear Scale)" 289
78 Secchi Depth and Chlorophyll a Relationship in
Natural Waters (Log-Log Scale! 291
79 Phosphorus Loading Characteristics and Secchi
Depth Relationship in Natural Waters 292
80 Phosphorus Loading Characteristics and Hypolimnetic
Oxygen Depletion Relationship in Natural Waters 298
81 Phosphorus Loading and Mean Depth/Hydraulic Residence
Time Relationship as Applied to Hypothetical Water Body
Under Several Phosphorus Loading Scenarios 301
xvi
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Number Page
82 Phosphorus Loading Characteristics and Mean Chlorophyll
a_ Relationship as Applied to Hypothetical Water Body
Under Several Phosphorus Loading Scenarios 303
83 Secchi Depth and Mean Chlorophyll a_ Relationship as
Applied to Hypothetical Water Body Under Several
Phosphorus Loading Scenarios 304
84 Phosphorus Loading Characteristics and Secchi Depth
Relationship as Applied to Hypothetical Water Body
Under Several Phosphorus Loading Scenarios 305
85 Phosphorus Loading Characteristics and Hypolimnetic
Oxygen Depletion Relationship as Applied to Hypothetical
Water Body Under Several Phosphorus Loading Scenarios ... 306
86 Relationship Between Excessive Phosphorus Loads and
Chlorophyll a in US OECD Water Bodies 363
87 Relationship Between Excessive Phosphorus Loads and
Excessive Chlorophyll a in US OECD Water Bodies 364
88 Relationship Between Vollenweider Phosphorus Loading
Diagram, Summer Mean Chlorophyll a and Secchi Depth 366
xvn
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TABLES
Number Page
1 OECD Member Countries .................................. 8
2 Summary of Essential and Desirable Parameters in
OECD Eutrophication Study .............................. 14
3 List of Water Bodies in OECD North American
Project (US Portion) ................................... 19
4 Characteristics of US OECD Water Bodies ................ 24
5 Summary of Aquatic Plant Micronutrient Requirements ..... 33
6 Demand : Supply Ratios for the Major Aquatic Plant
Nutrients ............................................... 35
7 Atomic Ratios of C, N and P Present in Plankton ........ 37
8 Chemical Composition of Some Algae Erom Ponds and
Lakes in the Southeastern US ........................... 38
9 Summary of Limiting Aquatic Plant Nutrients in
US OECD Water Bodies ................................... 41
10 Mass Ratios of Inorganic Nitrogen to Soluble
Orthophosphate in US OECD Water Bodies ................. 43
11 Analytical Procedures for Major Response Parameters
Examined in US OECD Eutrophication Study ............... 81
12 Summary of Methods Used to Calculate Nutrient Loadings
for US OECD Water Bodies ............................... 90
13 Summary of Nutrient Sources Considered in US OECD
Water Body Nutrient Loading Estimates .................. 112
14 Identification Key for US OECD Water Bodies ............ 115
15 US OECD Data for Vollenweider ' s Mean Phosphorus/
Influent Phosphorus and Hydraulic Residence Time
Relationship ........................................... 12°
xviii
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Number Page
16 Typical Values of Watershed Nutrient Export
Coefficients 127
17 Watershed Nutrient Export Coefficients Used to Check
US OECD Nutrient Loadings 128
18 US OECD Nutrient Loadings Calculated Using Watershed
Nutrient Export Coefficients 130
19 Comparison of Phosphorus Loadings Derived from
Watershed Export Coefficients with Loadings Predicted
by Vollenweider's Mean Phosphorus/Influent Phosphorus
and Hydraulic Residence Time Relationship 142
20 Phosphorus and Nitrogen Loadings, Mean Depths (z) and
Hydraulic Residence Times (T ) for US OECD Water
Bodies " 149
21 Phosphorus and Nitrogen Residence Times of US OECD
Water Bodies 164
22 US OECD Data Used in Vollenweider's Critical Phosphorus
Loading Equation 171
23 US OECD Data Applied to Vollenweider's Phosphorus
Loading and Mean Chlorophyll a Concentration Relation-
ship 7 194
24 US OECD Data Applied to Dillon's Phosphorus Loading-
Phosphorus Retention and Mean Depth Relationship 207
25 US OECD Data Applied 'to Larsen and Mercier's Influent
Phosphorus Concentration and Phosphorus Retention
Relationship 213
26 List of Correlations Examined In US OECD Water
Bodies 218
27 Data for Chlorophyll a and Secchi Depth Relationship.... 286
28 Summary of Data for Hypothetical Water Body Under
Several Phosphorus Load Reduction Scenarios 300
29 Summary of Phosphorus Loading Characteristics,
Chlorophyll a and Secchi Depth of Hypothetical
Water Body Under Several Phosphorus Load
Reduction Scenarios 309
xix
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Number Page
30 General Characteristics Frequently Used to Classify
Water Bodies 321
31 US EPA Trophic State Index Parameters 325
32 The Carlson Trophic State Index and Its Associated
Parameters 327
33 Piwoni and Lee Trophic State Index Parameters 329
34 Ranking of US OECD Water Bodies Using Modified
US EPA Trophic State Index System 336
35 Relative Trophic Status Ranking of US OECD Water
Bodies Using Modified US EPA Trophic Status Index
System 340
36 Ranking of US OECD Water Bodies Using Carlson Trophic
Status Index System 343
37 Relative Trophic Status Ranking of US OECD Water
Bodies Using Carlson Trophic Status Index System 346
38 Ranking of US OECD Water Bodies Using Piwoni and Lee
Modified Trophic Status Index System 349
39 Relative Trophic Status Rankings of US OECD Water
Bodies Using Piwoni and Lee Modified Trophic Status
Index System 353
40 Ranking of US OECD Water Bodies Using Secchi Depth,
Chlorophyll a, Excess Chlorophyll a and Excess Phosphorus
Loading as Ranking Parameters .... 7 355
41 Relative Trophic Status Ranking of US OECD Water Bodies
Using Secchi Depth, Chlorophyll a, Excess Chlorophyll a_
and Excess Phosphorus Loading . .7 359
xx
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ACKNOWLEDGEMENTS
This study was supported by contract numbers R-803356-01-0
and R-803356-01-3 from the US EPA National Research Laboratory,
Corvallis, Oregon. N. Jaworski, formerly of that laboratory,
served as contract officer during the majority of the study
period. J. Gakstatter served as contract officer during the
final phase of this study. We wish to acknowledge their assis-
tance in this study. We also wish to acknowledge the assistance
given this study by all of the US investigators in the OECD
Eutrophication Program.
Special recognition is due R. Vollenweider of the Canada
Centre for Inland Waters who provided the stimulus for the OECD
eutrophication studies, as well as many of the basic ideas
utilized in this study for data examination and formulation into
nutrient load-lake response relationships which can be utilized
for water quality management.
Several individuals at the University of Texas at Dallas
contributed significantly to the completion of this .report.
Special recognition should be given to D. Canham, J. Hale,E. Meckel,
M. Jaye, A. Jones, L. Lawhorn, G. Max and P. Wernsing. Substantial
support was given the completion of this report by the Uni-
versity of Texas at Dallas and EnviroQual Consultants £ Lab-
oratories of Piano, Texas.
This report is essentially the same as the Ph.D. dissertation
of Walter Rast for The University of Texas at Dallas.
xxi
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SECTION I
INTRODUCTION
The excessive fertilization (eutrophication) of natural
waters is one of the most significant causes of water quality
deterioration in the US and in many other countries. This in-
creasing eutrophication, resulting principally from the cultur-
al activities of man, is occurring because of the excessive in-
put of aquatic plant nutrients into water bodies. Some water
bodies are naturally eutrophic in that they receive sufficient
supplies of aquatic plant nutrients, mainly phosphorus and ni-
trogen, from natural sources to produce excessive growths of
algae and macrophytes. However, many of man's activities which
accelerate this transport of aquatic plant nutrients into water
bodies can greatly accelerate the eutrophication process. While
eutrophication may be desirable in some water bodies to increase
productivity, in general the eutrophication process is associ-
ated with water quality deterioration. Excessive algal or macro-
phyte growths can result in a significant deterioration of water
quality, which can greatly hinder the waters' use for domestic
and industrial water supplies, for irrigation and for recreation.
Today eutrophication ranks as one of the most significant causes
of water quality problems in the US, and it will probably become
of greater concern as other water pollution problems are allevi-
ated (Lee, 1971).
While other elements have occasionally been proposed (Goldman,
1964; Provasoli, 1969; Kerr et_aJ., 1970; Schelske and Stoermer,
1972), phosphorus and nitrogen are generally considered to be
the. major nutrients controlling or limiting the productivity of
water bodies, and hence the eutrophication process. Of these
two nutrients , the key element most often found limiting aquatic
plant populations is phosphorus (Vollenweider, 1968; Lee, 1971;
^1973; Vollenweider and Dillon, 1974). Furthermore, in many
instances , phosphorus inputs to water bodies are from point
sources such as domestic wastewaters. By contrast, large inputs
of nitrogen are frequently from non-point (diffuse) sources such
as agricultural runoff, precipitation, dry fallout and nitrogen
fixation. These diffuse sources are usually more difficult to
control. In general, phosphorus inputs are often more amenable
to control measures than are nitrogen inputs (Vollenweider and
Dillon, 1974). Water bodies which are normally nitrogen-limited
can possibly be made phosphorus-limited if the phosphorus in-
puts are reduced sufficiently.
1
-------
Eutrophication control is frequently based on limiting
aquatic plant nutrient inputs, usually phosphorus. Attempting
to control the eutrophication process by controlling phosphorus
inputs to natural waters is both technically sound and economi-
cally feasible for many water bodies (Lee, 1973; OECD, 1974-a;
Vollenweider and Dillon, 1974). However, such a strategy re-
quires that the relationships between the phosphorus inputs and
the trophic responses of the aquatic plant populations of a
given water body be understood on a quantitative basis. Develop-
ment of such an understanding has always been an extremely
difficult problem because the eutrophication process is a complex
physical, chemical and biological phenomenon (Sawyer, 1966;
Fruh et_ a_l. , 1966; Fruh, 1967; Stewart and Rohlich, 1967; Vollen-
weider, 1968; Federal Water Quality Administration, 1969;
National Academy of Science, 1969; Lee, 1971; 1973; Likens,
1972a; US EPA, 1973a).
It flfas not been possible in the past to quantitatively re-
late the phosphorus loading of a given water body to the result-
ant aquatic plant related trophic response, as reflected in its
relative degree of eutrophication. Consequently, the management
of water systems subjected to cultural eutrophication has been
largely subjective. Extensive, and often expensive, programs
of aquatic plant nutrient removal from domestic wastewaters or
diversion of point source inputs of nutrients have been initiated
in an attempt to alleviate eutrophication problems in lakes and
impoundments. These programs have no quantitative data on the
expected effects of these programs on trophic response and water
quality in these water bodies. Clearly, a quantitative method-
ology is required to initiate effective water quality management
with some assurance that the desired results will be attained.
In an attempt to alleviate this situation, the Organization
for Economic Cooperation and Development (OECD) member countries
initiated the Cooperative Programme for the Monitoring of Inland
Waters, which was designed to provide quantitative data on the
aquatic plant nutrient load-lake and impoundment response re-
lationships, with particular emphasis on water quality and the
development of approaches to be used for water quality management
of excessive fertility problems.
-------
SECTION II
CONCLUSIONS
1. Based on the initial analysis of the US OECD eutrophication
study data, the approach developed and modified by Vollen-
weider, relating the phosphorus loading of a phosphorus-
limited water body to its morphological and hydrological
characteristics, has considerable validity as a method for
determining critical phosphorus loading levels and associated
overall degree of fertility for US lakes and impoundments.
2. The findings of this initial analysis give considerable sup-
port to the recent adoption of the Vollenweider nutrient
loading-water body fertility response relationship by the
US EPA as a basis for establishing phosphorus loading water
quality criteria.
3. Initial analysis of the US OECD data indicates the Vollen-
weider phosphorus critical loading criteria, developed for
water bodies located in northern temperate climates, also
appears to be applicable to warm climate water bodies such
as those found in the southern and southwestern US. Addi-
tional study needs to be done on water bodies in this
region to confirm this preliminary conclusion.
4. The Vollenweider phosphorus critical loading criteria, devel-
oped for planktonic algal responses to phosphorus loadings,
will likely have to be modified in order to be applicable to
water bodies whose primary productivity and aquatic plant nui-
sance problems are manifested mainly in macrophyte and attached
algal growth. Modifications of the critical phosphorus load-
ings will likely be required where the primary problem arising
from the excessive fertility is domestic water supply water
quality. Further, it is possible that the Vollenweider ap-
proach will not be applicable to impoundments with hydraulic
residence times in the order of a month or less, and especially
for those impoundments that show marked stratification of
inflowing waters during critical growing seasons.
5. The results of this study indicate the feasibility of using
the Vollenweider approach for determining critical nitrogen
loading levels and trophic state associations for nitrogen-
limited water bodies.
6. The similar relative positioning of the US OECD water bodies
3
-------
on both the phosphorus loading and nitrogen loading versus
mean depth/hydraulic residence time diagrams illustrates the
relatively constant ratio of nitrogen to phosphorus loading
to water bodies.
7. The relationship developed by Vollenweider, between a water
body's phosphorus loadings and its mean influent phosphorus
concentration and hydraulic loading, as well as the use of
watershed land use nutrient export coefficients, appear to
be effective means for determining the reasonableness of the
phosphorus and nitrogen loading estimates to a water body.
8. The trophic relationships developed by Vollenweider, between a
water body's phosphorus loading characteristics and its
mean chlorophyll concentration; by Dillon, between phosphorus
loading and phosphorus retention coefficient and mean depth;
and by Larsen and Mercier, between mean influent phosphorus
concentration and phosphorus retention coefficient, also
appear to be potential tools for estimating phosphorus loads,
average phosphorus content and associated overall degree of
fertility for many US lakes and impoundments.
9. Because of the lack of uniform analytical and sampling method-
ologies, direct comparisons of eutrophication data between
the US OECD water bodies must be made with caution. In
general, the correlations between phosphorus loading-concen-
trations and eutrophication response data are better than
those observed between nitrogen loading-concentration and the
same response parameters, and support the observations of
phosphorus-limitation of most of the US OECD water bodies.
10. The water quality models derived from the relationships be-
tween phosphorus loading and chlorophyll a_, phosphorus load-
ing and Secchi depth and phosphorus loading and hypolimnetic
oxygen depletion offer simple, practical and quantitative
methodologies for assessing the expected effects of eutroph-
ication control programs based on phosphorus removal from
domestic wastewaters and other phosphorus control programs,
on water quality in the affected water bodies.
11. The recently proposed trophic status index systems of the
US EPA, Carlson, and Piwoni and Lee produce'relatively similar
trophic rankings for the US OECD water bodies, suggesting
that their common ranking parameters may equate their trophic
ranking abilities.
12. The trophic status index system based on excess phosphorus
loading and excess chlorophyll a, derived in this report, offers
promise as a trophic ranking system based on the phosphorus
loading and expected water quality responses in water bodies.
13. The Vollenweider phosphorus loading and mean depth/hydraulic
4
-------
residence time diagram can be related to the common water
quality parameters of chlorophyll a_, Secchi depth and hypo-
limnetic oxygen depletion, based on the relationships between
total phosphorus, chlorophyll a, Secchi depth and hypo-
limnetic oxygen depletion in natural waters.
-------
SECTION III
RECOMMENDATIONS
1. The US EPA and the states should adopt the modified Vollen-
weider phosphorus load and mean depth/hydraulic residence
time relationship for determining the permissible phosphorus
loading for phosphorus-limited lakes and impoundments where
the primary concern is the impairment of water quality for
recreational use. The recently proposed US EPA Quality
Criteria for Water (US EPA, 1975b) should be modified to
include this recent modification of Vollenweider's model,
as well as the approaches presented by Dillon, and Larsen
and Mercier.
2. The US should continue to actively participate in the inter-
national OECD Eutrophication Program data review, synthesis
and report preparation. Such participation is likely to
result in a much better understanding of the types of water
bodies that obey the modified Vollenweider nutrient loading
relationship.
3. Research funds should be made available at the federal and
state levels to further investigate the applicability of the
Vollenweider nutrient loading relationships for lakes and
impoundments located in the southern half of the US as well
as for water bodies with high levels of inorganic turbidity,
color, attached algae and macrophyte, and floating macro-
phyte water quality problems. Also, special consideration
should be given to water bodies with short hydraulic resi-
dence times and shallow depths and to impoundments which show
high degrees of stratified inter or underflow waters.
4. Studies should be conducted to further refine the permissible
versus excessive loading criteria, giving particular atten-
tion to differences in water quality problems associated with
recreational use in various regions of the US, especially the
southern half of the US, and the critical nutrient loadings
for impairment of domestic water supply water quality.
5. Further work should be done to establish a relationship be-
tween the critical phosphorus loading relationship as defined
by Vollenweider, the actual phosphorus loading for a given
water body, and its associated water quality. The ultimate
-------
objective of these studies should be the development of
quantitative relationships which can be used to further
predict a change in the water body's water quality as a
function of an altered nutrient load. Particular attention
should be given to assessment of water quality in terms of
planktonic algal growth, attached algae and macrophyte
growth, chlorophyll concentration, water clarity and hypolim-
netic oxygen depletion.
6. Studies should be conducted to develop similar nitrogen re-
lationships and information as described above for phosphorus
7. Studies need to be conducted to examine the significance of
utilizing total phosphorus and total nitrogen as a basis
for establishing loading criteria versus using the available
forms of these nutrients for establishing loading criteria.
-------
SECTION IV
ORGANIZATION FOR ECONOMIC COOPERATION
AND DEVELOPMENT
The Organization for Economic Cooperation and Development
(OECD) is an independent, international organization headquartered
in Paris. It is concerned primarily with the economic growth of
its twenty-four member nations. These comprise the more highly
developed countries of the world, excluding the Communist-bloc
nations. As a group, they produce more than 60 percent of the
world's wealth and enjoy the world's highest per capita incomes
(OECD, 1973a; 1974b). The member nations are presented in Table 1
Table 1. OECD MEMBER COUNTRIES
Australia Greece Norway
Austria Iceland Portugal
Belgium Ireland Spain
Canada Italy Sweden
Denmark Japan Switzerland
Finland Luxembourg Turkey
France Netherlands United Kingdom
Germany New Zealand United States
Special Status Country: Yugoslavia
(From OECD, 1973a)
Because economic development of the member nations is its
organizational focus, OECD contains a number of committees asso-
ciated with the various aspects of economic development and growth
These committees and the OECD organizational structure are
presented in Figure 1. Recognizing that economic productivity
frequently gives rise to environmental problems, the OECD has
concerned itself with both the quantitative and qualitative
aspects of economic development. In 1970 it transformed its
Committee for Research Cooperation into the more comprehensive
Environment Committee, which is responsible for:
1. investigating the problems of preserving or improving
man's environment, with particular reference to
economic and trade implications;
-------
DEVELOPMENT
ASSISTANCE
COMMITTEE
TECHNICAL
COOPERATION
COMMITTEE
^ENVIRONMENT
COMMITTEE
COMMITTEE FOR
SCIENTIFIC AND
TECHNOLOGICAL
POLICY
ECONOMIC POLICY
ECONOMIC AND
DEVELOPMENT
REVIEW COMMITTEE
COMMITTEE FOR
MONETARY a FOREIGN
EXCHANGE MATTERS
COUNCIL
EXECUTIVE
COMMITTEE
1 NTERNATIONAL
SECRETARIAT
(divided mto Directorates cover-
ing all the issues treated by
the Committees)
CENTRE FOR
EDUCATIONAL
RESEARCH AND
INNOVATION
SPECIAL
PROGRAMMES
'Formerly the Committee for Research Cooperation
( From OECD, I973o)
Figure 1. Organizational Structure of OECD.
-------
2. reviewing and confronting actions taken or
proposed in member nations in the field of
environment, together with their economic
trade implications;
3. proposing solutions for environmental problems
that would, as far as possible, take into
account all relevant factors including cost
effectiveness; and
4. insuring that the results of environmental
investigations can be effectively utilized in
the wider framework of the Organization's work
on economic policy and social development.
The Environment Committee is assisted by various delegate
groups concerned with the development of policy in specific
areas of overall environmental problems. These delegate groups
are presently concerned with the environmental problems of
water and air pollution, automobile and aircraft noise, traffic
congestion and urban transport and hazardous chemicals (OECD,
1973a; 1974a). The Environmental Committee and its associated
delegate groups are outlined in Figure 2.
WATER MANAGEMENT SECTOR GROUP
Concern over the problems of decreased water quality caused
by eutrophication had been expressed by OECD even before the
formation of the Environment Committee. Eutrophication of vari-
ous degrees of severity had been observed in lakes, flowing
waters and impoundments in most of the world's highly developed
nations for many years (Vollenweider, 1968). An ad hoc group of
the OECD Committee for Research Cooperation, chaired by 0. Jaag
(EAWAG, Zurich), recommended that a study be made of the existing
literature on eutrophication, with particular reference to the
roles of phosphorus and nitrogen in the eutrophication process.
This study, completed by R.A. Vollenweider, resulted in the 1968
report, "Scientific Fundamentals of the Eutrophication of Lakes
and Flowing Waters With Particular Reference to Nitrogen and
Phosphorus as Factors in Eutrophication" (Vollenweider, 1968).
This report noted the lack of "sufficient relevant measurement
data" for producing precise guidelines for eutrophication control.
In 1967, the Water Management Research Group was formed. In
May, 1968, this group held a symposium in Skokloster, Uppsala,
Sweden on large lakes and impoundments. A report of this symposium
was published by OECD in 1970 (OECD, 1970). The Water Management
Research Group became the Water Management Sector Group (WMSG)
after formation of the Environment Committee in 1970 (OECD, 1975).
In 1971, after the formation of the Environment Committee,
the WMSG established a Steering Group on Eutrophication Control.
In 1973 and 1974, this group produced a series of reports con-
cerning the effects of detergents, fertilizers and agricultural
wastes, and phosphorus and nitrogen wastewater treatment processes
10
-------
OECD COUNCIL
ENVIRONMENT COMMITTEE —
f"
SECTOR
GROUP
ON AIR
MANAGEMENT
I
SECTOR GROUP
ON UNINTENDED
OCCURRENCE
OF CHEMICALS
IN THE
ENVIRONMENT
I
SUB-COMMITTEE OF ECONOMIC EXPERTS
(ANALYSIS 8 EVALUATION )
JOINT AD HOC
POLICIES ISSUES
GROUP ON
WASTE DISPOSAL
( From OECD, I973a )
Figure 2. Organizational Structure of
OECD Environment Committee.
11
-------
on water quality. It also produced the Report of the Water
Management Sector Group on Eutrophication in 1974. More sig-
nificant, however, was the 1973 report entitled "Summary Report
of the Agreed Monitoring Projects on Eutrophication of Waters"
(OECD, 1973b). This report was prepared by a WMSG planning group
on measurement and monitoring. It is this report which outlines
the working plan for the international cooperative eutrophication
study undertaken by OECD. The OECD North American Project is
part of this cooperative effort.
OECD INTERNATIONAL COOPERATIVE PROGRAM FOR MONITORING OF INLAND
WATERS
Objectives of Study
In order to better quantitatively define the eutrophication
process and the factors which cause and control it, upon recommen-
dation of the above-mentioned planning group, the WMSG established
a program among the OECD member nations of measurement and monitor-
ing of inland waters. This international effort was to coordinate
measurements of
-------
Common Measurement System
Previous attempts to quantitatively categorize freshwater
bodies in terms of tolerance to nutrient inputs, as manifested in
their biological productivity, nutrient budgets and trophic levels,
have been difficult because of the lack of comparable data for
interrelating water bodies. Such lack of comparable data has
greatly hindered development of criteria for predicting changes in
water quality resulting from changes in nutrient loadings.
Consequently a common system of measurements was established
early in the study. In addition to aiding in the choice of eutrophica-
tion control measures in a water body, the common system will also
permit measurement of the effectiveness of a given control measure and
the response of the water body to changing hydrological conditions.
The system of measurements recommended was divided into
three categories: physical, chemical and biological. These
categories were, in turn, divided into "essential" and "desirable"
measurements. In addition, guidelines were established for the
range of background data considered necessary for providing ade-
quate geographical, morphometric, hydrological and ecological
descriptions of a given water body.
The essential parameters were those considered necessary
for establishing an accurate representation of trophic conditions
in a given water body. These parameters would also allow a com-
parison of eutrophication data between water bodies. In addition,
they would allow the assessment of the effectiveness of control
measures initiated in an attempt to alleviate eutrophication
problems.
Those parameters which were appropriate for large capacity
laboratories or certain specialized laboratories were considered
"desirable". In general, the desirable parameters were used to
supplement the "essential" data (OECD, 1973b). A summary of these
essential and desirable parameters is given in Table 2.
Recommended analytical methods were taken from FWPCA (1969),
APHA et al. (1971) and Golterman (1971). Recommendations on
sampling techniques included locations, depths and frequencies of
sampling (OECD, 1973b).
Regional Approach
Recognizing that geographical, ecological, geological and
morphometric factors are of major importance in the eutrophica-
tion process, the WMSG chose to employ a regional approach. Con-
sequently the WMSG established four voluntary regional projects,
each embracing a family of specified types of water bodies.
Eighteen member nations agreed to participate in these
projects. There were three regionally-based projects and one
13
-------
Table 2. SUMMARY OF ESSENTIAL AND DESIRABLE PARAMETERS
IN OECD EUTROPHICATION STUDY
Category
Parameters
Physical
Essential
Desirable
Chemical
Essential
Desirable
Biological
Essential
Desirable
Temperature, electrical con-
ductivity, light penetration,
color, total solar radiation.
Turbidity.
pH, dissolved oxygen, phos-
phorus, nitrogen, silica,
alkalinity, acidity, calcium,
magnesium, sodium, potassium,
sulfate, chloride, total iron,
Other trace elements and
other micro-pollutants (e.g.
pesticides), hydrogen sulfide,
Phytoplankton (chlorophyll a)
primary productivity, organic
carbon.
Phytoplankton identification
14
(by genera and counting); C
uptake, zooplankton identifi-
cation (by genera and count-
ing) .
(From OECD, 1973b)
-------
functionally-based project in the overall eutrophication study
(OECD, 1973b). The regional organization and participating
countries are illustrated in Figure 3. The coordination centers
were to coordinate the activities within a given project and to
act as vehicles of exchange of information between the four
projects. Each individual project's groups of laboratories,
assisted by its coordination center, was responsible for design-
ing and establishing the necessary measurement procedures and
data evaluation methods (OECD, 1973b).
Each project had a coordinator who was a senior scientist
from one of the institutions or laboratories involved. Initially,
the Coordinating Group was established as a link between the
Technical Bureau and the WMSG. However, it was demonstrated that
the Technical Bureau could adequately perform both the technical
and managerial roles (OECD, 1975). The overall assessment and
coordination of the four projects was the responsibility of a
group of nationally nominated delegates from those countries par-
ticipating in the study. This group was to synthesize the reports
of the four projects into an optimal eutrophication control strat-
egy and report to the WMSG, in principle once a year.
The program was planned to run four years, from the beginning
of 1973 to the end of 1976. An overall analysis of the study is
planned for 1977. Upon completion of the four-year period of
measurements and study, it is expected that a symposium on the
overall interpretation of the results will be convened in order
to establish the extent to which nutrient loadings determine the
rate of development of eutrophication (OECD, 1973b; 1975).
The four regional projects are characterized as follows:
1. Nordic Project - Reasonably comparable conditions exist
in this project. These include the cool climate zone of
the Baltic and North Sea areas; lakes resulting from
retreat of the great Quaternary glaciers; comparable
ecological conditions and equivalent level of economic
development and pollution, and close political, cul-
tural and scientific links.
2. Alpine Project - The Alpine regions are the source
of many European waters. The Alpine waters are of
great social and economic significance because they
represent a great natural amenity and a source of con-
siderable tourism. Their ecology is characterized
by an abundant variety of species which are vulner-
able to man's interventions. The Alpine zones repre-
sent similar hydrological conditions due to comparable
geography, geology and ecology. The Alpine zones
share certain river basins and commissions.
3. Reservoir and Shallow Lakes Project - This project
includes man-made lakes and reservoirs and other
15
-------
ENVIRONMENT COMMITTEE
WATER MANAGEMENT SECTOR GROUP
ALPINE PROJECT
AUSTRIA
FRANCE
GERMANY
ITALY
SWITZERLAND
COORDINATION
CENTER-
ZURICH,
SWITZERLAND
NORDIC PROJECT
DENMARK
PIN LAND
NORWAY
SWEDEN
COORDINATION
CENTER.
HELSINKI,
Fl NLAND
RESERVOIR
PROJECT
COORDINATING
GROUP
DATA PROCESSING
8 ANALYSIS
AUSTRALIA
BELGIUM
GERMANY
IRELAND
JAPAN
NETHERLANDS
SPAIN
UNITED KINGDOM
COORDINATION
CENTER
SIEGBURG,
GERMANY
NORTH AMERICAN
PROJECT
CANADA
UNITED STATES
COORDINATION
CENTER:
BURLINGTON,
ONTARIO
Figure 3
Organizational
Eutrophication
Outline
Study.
of OECD
16
-------
comparable water bodies (i.e., shallow lakes,
lagoons and estuarine waters). All are relatively
shallow and have great economic and social values
(e.g., water supply reserves, water sports, fishing,
navigation, etc.). Water quality control by
manipulation of hydrological or other factors is
more feasible for these water bodies than for
larger water bodies.
North American Project - In contrast to the other
projects, this project is not restricted to study-
ing specific types of water bodies. Rather, the
trophic states of the involved water bodies span the
trophic spectrum from oligotrophic to eutrophic (OECD,
1973b).
17
-------
SECTION V
US OECD EUTROPHICATION STUDY
The major goal of the North American Project is similar to
that of the other projects; namely, to determine the quantita-
tive relationship between the nutrient loading and the result-
ant trophic state (i.e., degree of fertility) of a given water body,
Its specific objectives are as follows:
1. develop detailed nutrient budgets (phosphorus and
nitrogen) for a selected group of water bodies;
2. assess the physical, chemical and biological char-
acteristics of these selected water bodies;
3. relate the trophic states of the water bodies to
their nutrient budgets and to their limnological
and environmental characteristics; and
4. synthesize an optimal strategy, based on data from
all four projects, for controlling eutrophication.
The North Ameridan Project consists of studying thirty-four
water bodies in the United States and a larger number of water
bodies in Canada. The director of the North American Project
is R. Vollenweider of the Canada Centre for Inland Waters
(CCIW) in Burlington, Ontario, Canada. The United States
Environmental Protection Agency (US EPA) is the lead organiza-
tion for the US portion of the North American Project. The US
OECD study directors were N. Jaworski and J. Gakstatter
(US EPA, 1973b). The 34 water bodies in the US OECD study
are presented in Table 3 and their locations are illustrated
in Figure 4.
The water bodies in the US OECD study differ considerably
in their limnological characteristics and trophic states. It
is the responsibility of the principal investigator for each
water body to conduct the necessary measurements and to prepare
the necessary reports for his water body. Nearly all of the
water bodies selected for the US OECD study have been studied
extensively in the past. Because of these factors and a lack of
funds, no new sampling programs were initiated in the US OECD
study. Some of the water bodies were also included in the US
EPA's National Eutrophication Survey (NES), thereby providing a
link between the US OECD studies and the NES studies.
18
-------
Table 3.
LIST OF WATER BODIES IN OECD NORTH AMERICAN PROJECT
(US PORTION)
Water Body
Location
Tropic Status
Principal Investigator
Rlackhawk, Camelot-Sher- Wisconsin
wood, Cox Hollow, Dutch
Hollow, Redstone, Stewart,
Twin Valley and Virginia
Brownie, Calhoun, Cedar, Minnesota
Harriet and Isles
Mew York
New York
Minnesota
New York
N. Carolina.
Virginia
Wisconsin
Cayuga
Dogfish, Lamb and
Meander
heorge
Kerr Reservoir'
Mendota
Eutrophic
Eutrophic
Eutrophic
Mesotrophic
Oligotrophic
Old gotrophic-
Mesotrophic
Eutrophic-
Mesotrophic
Eutrophic
(Changing)
G. Fred Lee, Center
for Environmental Stu-
dies, Univ. Texas at
Dallas
J. Shapiro, Limnology
Research Center, Univ.
Minnesota
L. Hetling, Dept. Env.
Conscrv., State of New
York
R. Oglesby, Cornell
Univ.
S. Tarapchak, NOAA
Great Lakes Env. Res.
Lab, Ann Arbor, Mich.
M. Clesceri, Rensselaer
Polytechnic Inst.
C. Weiss, Univ. North
Carolina.
G. Fred Lee, Center
for Environmental Stu-
dies, Univ. Texas at
Dallas
-------
Table 3 (continued).
LIST OF WATER BODIES IN OECD NORTH AMERICAN PROJECT
(US PORTION)
ro
o
Water Body
Michigan
Open waters
Nearshore Waters
Minnetonka
Potomac Estuary
Sal lie
Sammamish
Shagawa
Tahoe
Twin Lakes
Wa]do
Location
Wisconsin,
Michigan,
Illinois £
Indiana
Minnesota
Maryland,
Virginia
Minnesota
Washington
Minnesota
California ,
Nevada
Ohio
Oregon
Trophic Status
Oligotrophic
Mesotrophic
Eutrophic
(Changing)
Ultra-Eutrophic
Eutrophic
Mesotrophic
Eutrophic
Ultra-Oligo-
trophic
Eutrophic
(Changing)
U] tra-Oligo-
trophic
Principal Investigator
G. Fred Lee, Center
for Environmental Stu-
dies, Univ. Texas at
Dallas
and
C. Schelske, Great
Lakes Research Division,
Univ. Michigan
R. Megard, Limnology
Research Center, Univ.
Minnesota
N. Jaworski, US EPA,
Corvallis, Oregon
J. Neel, Univ. North
Dakota
E. Welch, Univ.
Washington
K, Malueg, US EPA,
Corvallis , Oregon
C. Goldman, Univ.
California at Davis
D. Cooke , Kent State
Univ.
C. Powers, US EPA,
Corvallis, Oregon
-------
Table 3 (continued). LIST OF WATER BODIES IN OECD NORTH AMERICAN PROJECT
(US PORT EON)
Wa tor Body
Wash: ngton
Weir
Wingra
Location
Washington
Florida
Wisconsin
Trophic Status
Meos trophic
Meso trophic
Eutrophic
Principal Investigator
W.T. Edmondson , Univ.
Washington
P. Brezonik, Univ.
Florida
G. Fred Lee, Center
for Environmental Stu-
dies, Univ. Texas at
Dallas
Trophic Status Index Study J. Shapiro, Limnology
Research Center, Univ.
Minnesota
Summarization Report - G. Fred Lee and W.
US OECD Project Rast, Center for Environ-
mental Studies, Univ.
Texas at Dallas
-------
WASHINGTON
SAMMAMISH
BROWNIE 1
CALHOUN I
CEDAR )
HARRIET f
ISLESJ
"\
CAYUGA
/EAST TWIN
[WEST TWIN
CAMELOT-SHERWOOD |
DUTCH HOLLOW V
REDSTONE /
VIRGINIAj
POTOMAC
ESTUARY
IMENDOTA
[WINGRA
BLACKHAWK
COX HOLLOW \
TWIN VALLEY /
STEWART I
KERR '•
RESERVOIR
IOO 2OO 300
MILES
Figure 4. Locations of US OECD Water Bodies.
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GENERAL CHARACTERISTICS OF US OECD WATER BODIES
The general characteristics of the water bodies in the
US OECD study are presented in Table 4- , which indicates that
the 34 water bodies of the US OECD study include 24 lakes, nine
impoundments and one estuary. Thus, 71 percent of the water
bodies in the US OECD study are lakes and 26 percent are im-
poundments. However, several of these water bodies are divided
into separate arms or regions (e.g., Kerr Reservoir and the
Potomac Estuary). When these separate regions are considered,
there are 38 US water bodies in the US OECD eutrophication study.
Furthermore, several of the US OECD water bodies have been pre-
viously examined and have subsequently undergone remedial treat-
ment for eutrophication (e.g., Minnetonka, Twin Lakes, Washing-
ton). Thus, although 38 water bodies are included in the US
OECD study, a total of 47 individual nutrient loading-trophic
response relationships were examined.
The principal investigators classified 24 of the water
bodies as eutrophic (63 percent), seven as mesotrophic (18 percent)
and seven as oligotrophic (18 percent) at the time of the US OECD
study. These percentages reflect the investigator-indicated
trophic states at the time of submission of final reports.
Twenty-eight (74 percent) of the water bodies have mean
depths less than ten meters while ten (26 percent) have mean
depths greater than ten meters. The mean depths range from 1.7
meters (Lake Virginia) to 313 meters (Lake Tahoe). The water-
shed areas range from 47 hectares (Brownie Lake) to 1.76 x 10
hectares (Lake Michigan). Sixteen (42 percent) of the water
bodies have surface areas greater than 1000 hectares. Twenty-
three (61 percent) of the water bodies have hydraulic residence
times (i.e., water body volume/annual inflow volume) of greater
than one year. The hydraulic residence times range from 0.08 yr
(Lake Stewart) to 700 yr (Lake Tahoe). Twenty-four (63 percent)
have mean specific conductances of 200 ymhos/cm (25°C) or greater.
Of the 24 water bodies with mean specific conductances
greater than 200 ymhos/cm, 21 were classified eutrophic, two
mesotrophic and one oligotrophic. As expected, the single
estuary studied had the highest mean specific conductance ,
ranging from 200-500 ymhos/cm (25°C) at the fresh water input
to 26,000 ymhos/cm at the saline end of the estuary.
Of the 13 water bodies with less than 200 ymhos/cm mean
specific conductance, seven were oligotrophic, four mesotrophic,
and two eutrophic. Ultra-oligotrophic Lake Waldo exhibited the
lowest reading, 3 ymhos/cm (25°C).
The mean alkalinities ranged from 2 mg/1 as CaCO« (Lake
Waldo) to 248 mg/1 (Canadarago Lake). The distribution was
relatively even, with 18 (47 percent) having mean alkalinities
greater than 100 mg/1 as CaCOQ.
O
23
-------
Table 4. CHARACTERISTICS OF US OECD WATER BODIES
Water Watershed
WATER BODY Trophic Body Area3 ~
(location) Status" Type0 (xlO m )
LAKE BLACKHAWK E I 36.3
(Wise. )
BROWNIE LAKE E L 0.47
(Minn. )
LAKE CALHOUN E L 7.61
(Minn. )
CAMELOT-SHERWOOD E I 90.6
COMPLEX (Wise. )
CANADARAGO LAKE E L 182
( N . Y . )
CAYUGA LAKE M L 2030
(N.Y. )
CEDAR LAKE E L ] . 63
(Minn. )
COX HOLLOW LAKE E I 16.1
(Wise.)
DOGFISH LAKE ° I, 0.88
(Minn. )
DUTCH HOLLOW E I 12.b
LAKE (Wise. )
Water
Body
Surface
Area r ?
(xlO m
8. 90
0.73
17.0
28.3
75. 9
1720
6. 90
3. 88
2.91
8.50
Mean
Hydraulic
Mean Residence
Depth6 Timef
) (m) (yr)
4.9 0.5
6.8 -2.0
10.6 3.6
3.0 0.09-0.14
7.7 0.6
54.5 8.6
6.1 3.3
3.8 0 .5-0 .7
4.0 3.5
3.0 1.8
Mean Mean Con-
Secchi ductivity
Depth (pmhos/cm
(m) @ 25°C)
3-6 471
1.5 400-475
2.1 400-500
2.0 311
1.8 223
2.3 575
1. 8 400
1 .5 440
2.5-2.7 16-17
0.8 252
Mean Alka-
linity
(mg/1
as CaC03)
227
123-136
80-123
125
248
102
71-109
205
8-10
133
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TnMe 'I (rcm I i lined ) . CHARACTERISTICS OF US OECD WATER BODIES'1
"
WATLR BODY Trophicb
(Location) Status
LAKE GEORGE 0-M
LAKE HARRIET E
(Minn. )
LAKE OE THE E
ISLES (Minn. )
to
en KERR RESERVOIR E-M
(N. Carol ina-Vir . )
Roanoke Arm
Nutbush Arm
LAMB LAKE 0
(Minn. )
MEANDER LAKE 0
(Minn. )
LAKE MENDOTA E
(Wise. )
LAKE MICHIGAN 0-M
Wa tcr
Body
Water Watershed Surface
Body Area$ „ Area^ „
Type0 (xlO rn ) (xlO ni )
I, 606 11 UO
L 't. 80 14.3
L 2.85 4.20
I 20,200 1754
1250
504
L 1.96 3.97
L 1.69 3.60
L 686 39U
L 176,000 580,000
Mean
Depth6
(m)
18.0
8. 8
?. 7
-
10. 3
8.2
4 .0
5.0
12.0
8U
Mean
Hydraulic Mean Mean Con-
Residence Secchi ductivity
Timef Depth (vimhos/cm
(yr) (m) @ 25 C)
8.0 8.5 86
2.4 2.4 360-425
0.6 ].0 380-470
_ _
0.2 1.4 100
5.1 1.2 123
2.3 1.8-2.2 U7
2.7 3.0-3.1 17-20
4.5 3.0 300
30-100h
Mean Alka-
linity
(mg/1
as CaCO,)
21
92-124
68-131
-
28
22
30-36
8
160
-
(Wise., Mich.,
111. , Ind. )
-------
Table 4 (continued). CHARACTERISTICS OF US OECD WATER BODIES0
WATER BODY Trophic.
(Location) Status
LAKE MICHIGAN
(cont'd)
Nearshore
Waters
Offshore
Waters
Open Lake
Waters
LAKE MINNETONKA
M
M
0
(Minn.)
Pre-sewage E
Treatment (1969)
Post-sewage E-*M
Treatment (1973)
POTOMAC ESTUARY
(Maryland, Vir. )
Upper Reach
Middle Reach
Lower Reach
LAKE REDSTONE
(Wise. )
U-E
E
Water
Body
Water Watershed Surface
Body AreaSJ , Area, „
Typec (x!0b rn ) (xlO m
_
_
_
L 371g 262
L 371g 262
L 371g 262
E 38,000 9644
574
2120
6950
I 76.7 25.2
Mean
Hydraulic Mean
Mean Residence Secchi
Depth6 Timef Depth
) (m) (yr) (m)
_
-
_
8.3
8. 3
8.3
4.8
5.1
7.2
4. 3
2.3
7.0
_
6.3g
1.5
1.8
0.04 0.4-0.8
0.18 0.5-1.3
0.85 1.0-2.3
0.7-1.0 1.6
Mean Con- Mean Alka-
ductivity linity
(vmhos/cm (mg/1
@ 25°C) as CaC03)
265
260
255
^
317
200-500
600-17,000
17,000-26,000
260
107
106
113
,_
250
250
70-110
60- 85
65- 85
125
-------
Table 4 (continued). CHARACTERISTICS OF US OECD WATER BODIES0
WATER BODY Trophic,
(Location) Status
LAKE SALLIE
(Minn. )
LAKE SAMMAMISH
(Wash. )
SHAGAWA LAKE
(Minn. )
LAKE STEWART
(Wise. )
E
M
E
E
LAKE TAHOE U-0
(Calif. ,Nev. )
TWIN LAKES
(Ohio)
EAST TWIN LAKE
Pre-sewage
Treatment(1972
Post-sewage
Treatment(1974
WEST TWIN LAKE
Pre-sewage
_
_
E
)
E
)
_
E
Water Mean
Body Hydraulic
Water Watershed Surface Mean Residence
Body Aread Area,. Depth6 Timef
Type0 (xlO m ) (xlO ni ) (m) (yr)
L 1540
L 273
L 269
I 2.07
L 1310
L 3. 34
L
L
L
L
L
53.0
198
92. 0
0.25
4990
_
2.G9
2.69
2 .69
3.40
3.40
6.4 1.1-1.8
17.7 1.8
5.7 0.8
1.9 0.08
313 700
_ _
5.0
5.0 0.80
5.0 0.50
4.3
4.3 1.6
Mean Mean Con- Mean Alka-
Secchi ductivity linity
Depth (ymhos/cm (mg/1
(m) @ 25 C) as CaCOj)
280-360 162
3.3 94 33
2.3 60 22
1.4 540 213
28 92 43
- — -
_ _ _
1.6 374
1.9 366 105
— — _
2.2 411
Treatment(1972)
Post-sewage
E
L
3.40
4.3 1.0
2.3 380 106
Treatment(1974)
-------
Table 4 (continued). CHARACTERISTICS OF US OECD WATER BODIES3
WATER BODY
(Location)
Trophic.
Status
TWIN VALLEY LAKE E
(Wise. )
LAKE VIRGINIA
(Wise. )
WALDO LAKE
ro (Ore.)
00
E
U-0
LAKE WASHINGTON
(Wash. )
Pre- sewage
Diversion
Post-sewage
Diversion
LAKE WEIR
(Fla. )
LAKE WINGRA
(Wise. )
E
(1964)
M
(1974)
M
E
Water
Body
Type
I
I
L
L
L
L
L
L
Water
Body
Watershed Surface
Aread
(xlO6 m2
31.1
6.48
79
1590
1590
1590
46.0
14.0
Area,
) (x!0b in ]
6.07
1.82
270
876
876
876
240
13.7
Mean
Hydraulic Mean Mean Con-
Mean Residence Secchi ductivity
Depth Timef Depth (pmhos/cm
I (m) (yr) (m) @ 25°C)
3.8
1.7
36
33
33
33
6.3
2.4
0.4-0.5 1.5 370
0.9-2.8 1.2 230
21 28 3
2.4
2.4 1.2 80
2.4 3.8 81
4.2 1.9 133
0.4 1.3
Mean Alka-
linity
(mg/1
as CaCOg)
175
64
2
-
2S
45
12
153
aAs reported by \JS OECD investigators. See Summary Sheets (Appendix II)
Investigator-indicated trophic status: (U-E) = Ultra-Eutrophic
(E) = Eutrophic
(M) = Mesotrophic
(0) = Oligotrophic
(U-0) = Ultra-Oligotrophic
-------
Table '4 (continued). CHARACTERISTICS OF US OECD WATER BODIES3
EXPLANATION: (continued)
Water body type : E = Estuary
I = Impoundment
L = Lake
Includes lake surface area
e 32
Mean depth = water body volume (m ) /water body surface area (m )
Hydraulic residence time = water body volume (m )/annual inflow volume (m /yr)
a
Values for whole lake. All other data is only for Lower Lake Minnetonka
Range of values as reported in the literature; most accurate range is assumed to
be 70-100 years. See Piwoni et al. (1976) for discussion of Lake Michigan
hydraulic residence time.
Dash (-) indicates data not available.
-------
Twenty-eight (74 percent) had mean Secchi depths less than
three meters. No Secchi data were available for two water bod-
ies. Of the 28 water bodies with Secchi depths less than three
meters, 22 were classified by their respective investigators as
eutrophic, five mesotrophic and one oligotrophic (Dogfish Lake).
Within the eight water bodies of three meters or greater Secchi
depths, five were classified oligotrophic, one mesotrophic and
two eutrophic (Lakes Blackhawk and Mendota). The mean Secchi
depths ranged from 0.6 meters in the Upper Reach of the Potomac
Estuary to greater than 28 meters (Lakes Tahoe and Waldo).
DATA REPORTING METHODOLOGY
The general approach involved in the US OECD study is pre-
sented in the Final Report Outline (Appendix I). This Final
Report Outline was prepared by the North American Project parti-
cipants and served both as a guide to the types of information
and studies needed in the North American Project and as an out-
line for the presentation of the data generated in the North
American Project in standardized Final Reports. Part of the in-
formation in the Final Report Outline was suggested by the WMSG
as necessary "background data" (OECD, 1973b).
The Final Report Outline begins with a short introductory
section, followed by a brief geographical description of the
water body. This includes its latitude, longitude and altitude,
the watershed area, general climate data, general geological
description, vegetation, watershed population, land usage and
wastewater discharges into the water body. Next is a. brief
morphometric and hydrologic description of the water body, in-
cluding its surface area, volume, mean and maximum depths,
ratio of epilimnion to hypolimnion, duration of stratification,
lake sediment'.types , seasonal precipitation variation, water
budget, water currents"and hydraulic residence time. This is
followed by a limnological characterization of the water body,
including a physical, chemical and biological summary. A
nutrient budget summary, including phosphorus and nitrogen
inputs, follows the limnological characterization. Finally,
there is a discussion section which includes a delineation of
water body trophic status and discussion of the general lim-
nological characteristics. In addition, the degree of correla-
tion between the water body nutrient loading and trophic re-
sponse is discussed in detail. These two parameters are also
to be discussed in relation to the water body's general lim-
nological characteristics.
The US OECD study "Summary Sheets" (Appendix II) were de-
vised to summarize the important loading and response parameters
of the US OECD water bodies. They include the water body name
and type, watershed and water body surface area, mean depth,
water residence time, important trophic response parameters
(e.g., nutrient and chlorophyll a concentrations, primary
30
-------
productivity) and nutrient loadings. The Summary Sheets and the
Final Report Outline were prepared to allow the presentation of
data in a standardized form.
US OECD EUTROPHICATION STUDY AND OTHER US EUTROPHICATION
CONTROL PROGRAMS
National Eutrophication Survey
Several years ago, the US EPA (1975a) initiated the National
Eutrophication Survey. This Survey was designed to study approx-
imately 800 water bodies throughout the US for which estimated
nutrient load-response relationships would be ascertained.
Because of funding limitations, sampling of tributaries and water
bodies was limited to one year and was not intensive. The US
OECD eutrophication study provides similar information for a
smaller number of water bodies and was generally based on a much
more intense sampling program. For the water bodies common to both
programs, a comparison of the two approaches will aid the US EPA
and other water pollution regulatory agencies in assessing the
validity of the results and conclusions from the National Eutro-
phication Survey.
Public Law 92-500
Section 314-A of Public Law 92-500 requires all the states
in the US to classify their publicly-owned water bodies as to
trophic status. It further requires the states to initiate
eutrophication control measures in water bodies deemed excessively
fertile. Thus, the overall aims of the US OECD eutrophication
study, the US EPA's NES study and the intent of Public Law
92-500, Section 314-A, are generally identical. They are to
ascertain what trophic classification or index system should be
used, what parameters should be measured, how a given set of
conditions in a water body can be related to its trophic status,
how one predicts response of a water body to a change in a
chemical, biological or physical parameter and what the aquatic
plant trophic response will be to a given water body's nutrient
input. By attempting to answer questions of this type, the US
OECD eutrophication study can be used by the states to help them
fulfill the mandate of Section 314-A of Public Law 92-500.
Public Law 92-500 also requires the US EPA to develop water
quality criteria. In October, 1973 the US EPA released draft
proposed criteria for public comment (US EPA, 1973c). In
November, 1975 the US EPA released revised draft Quality Criteria
for Water (US EPA, 1975b) and again asked for comment. While
no criteria were proposed for phosphorus as an aquatic plant
nutrient, the US EPA suggested in the November 1975 criteria that
a nutrient loading-response relationship similar to those being
investigated in the US OECD eutrophication study be adopted.
31
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USE OF N:P RATIOS IN DETERMINING THE AQUATIC PLANT GROWTH
LIMITING NUTRIENT IN NATURAL WATERS
The role of phosphorus and nitrogen as aquatic plant (i.e.,
algae and macrophytes) nutrients in the primary productivity and,
hence , in the eutrophication of natural waters has been well-
documented (Sawyer, 1947; American Water Works Association, 1966;
Vollenweider, 1968; Edmondson, 1970b; Lee, 1971; Ryther and Dunstan.
1971; Maloney et_ al_. , 1972; Powers et al. , 1972; Martin and Goff,
1972; Shannon and Brezonik, 1972; Brezonik, 1973; Lee, 1973;
Vallentyne, 1974; United States Environmental Protection Agency,
1974a; Schindler and Fee, 1974; Vollenweider, 1975a; and Jones
and Bachmann, 1975, to cite but a few). The effects of man-
induced nutrient inputs , as opposed to natural nutrient inputs,
in accelerating the eutrophication process has also been studied
in detail (Sawyer, 1952; Curry and Wilson, 1955; Shapiro and
Ribeiro, 1965; Maloney, 1966; Vollenweider, 1968; Bartsch, 1970;
Stumm and Morgan, 1970; Bartsch, 1972; Edmondson, 1972; Beeton and
Edmondson, 1972; and Vallentyne, 1974). Various other elements
or compounds have been suggested as affecting or limiting the
eutrophication process, including iron, molybdenum, nitrate and
sulfate, vitamins and other organic growth factors, carbon and
silicon (Goldman, 1960; Menzel and Ryther, 1961; Goldman and
Wetzel, 1963; Goldman, 1964; Lange, 1967; Kuentzel, 1969; Pro-
vasoli, 1969; Kerr et_ al_. , 1970; Schelske and Stoermer, 1972).
However, most of these effects are either site-specific, or else
are temporal in nature and do not persist over the annual cycle.
Today, it is generally accepted that the phosphorus and nitrogen
in a water body, rather than the above-mentioned compounds, control
or limit the eutrophication process through their roles as aquatic
plant nutrients in the primary productivity of the water body.
However, not only are the absolute quantities of phosphorus and
nitrogen in a water body of importance in the eutrophication
process, but also their relative quantities seem to be a key
factor in determining which of these two elements will limit the
overall process.
The Limiting Nutrient Concept
A nutrient will be consumed or assimilated by an organism in
proportion to the organism's need for that nutrient. However,
it was noted as early as 1840 by Justus Liebig that growth of a
crop was not generally limited by the nutrients needed in large
quantities, which were often abundant in the environment, but
rather by the nutrients needed in minute quantities , which were
often scarce. This observation forms the basis of one of the
oldest laws of plant nutrition, LiebigTs "Law of the Minimum"
(Odum, 1971). Simply stated, Liebig's law states'that growth
of an organism is limited by the substance or foodstuff which
is available to it in the minimal quantity relative to its needs
for growth or reproduction. This principle has also been applied
to factors other than nutrients, including light and temperature.
32
-------
However, for the purposes of this discussion, the limiting nutrient
concept, as Liebig's Law of the Minimum has come to be called, will
be restricted to aquatic plant nutrients.
Nitrogen and Phosphorus as Limiting Nutrients
The nutrients (i.e., elements or compounds) needed in relative-
ly large quantities by aquatic plants include carbon, hydrogen,
oxygen, sulfur, potassium, calcium, magnesium, nitrogen and phos-
phorus (Fruh, 1967). In addition, there is a requirement for
traces of micronutrients as listed in Table 5.
TABLE 5. SUMMARY OF AQUATIC PLANT MICRONUTRIENT
REQUIREMENTS
Process Trace Element Required
Photosynthesis Manganese, iron, chloride,
zinc and vanadium
Nitrogen Fixation Iron, boron, molybdenum and
cobalt
Other Functions Manganese, boron, cobalt,
copper and silicon
(After Shannon, 1965, as cited in Fruh, 1967)
Among these macro- and micronutrient requirements, nitrogen
and phosphorus are generally considered to be the aquatic plant
nutrients of major importance in the eutrophication process.
Recently, the possible role of carbon as a limiting nutrient
has been proposed (Lange, 1967', Kuentzel, 1969; Kerr et al. , 1970).
However, the work underlying the so-called "Lange-Kuentzel-Kerr
thesis" has been questioned on several grounds (Shapiro, 1970;
Schindler, 1971; 1977; Fuhs ejt a 1. , 1972; Goldman et_ al. , 1972).
Goldman et: al. (1972) have reported that the results of Kerr ejt al.
(1970), indicating C02 to be the limiting nutrient in their
experiments, were due primarily to faulty experimental design.
The conclusions of Kerr et_ al. (1970) were supported mainly by
laboratory data with samples which contained surplus phosphorus
and a limited C02 content. Consequently, carbon was limiting
almost from the beginning of their experiments. A similar situa-
tion is frequently seen in wastewater stabilization ponds where,
because of the excessive quantities of phosphorus and nitrogen
relative to carbon, total algal productivity is known to be
limited by carbon (Goldman e_t al. , 1972). Such a situation
generally does not appear to occur in natural waters. Maloney
et al. (1972), in laboratory assays on water from nine Oregon
33
-------
lakes, and Powers et aj^. (1972), in field experiments on lakes in
Oregon and Minnesota, demonstrated that carbon addition to the
waters had no effect on algal growth rates. Further, there
appeared to be no correlation between algal rates and carbon con-
centration in the water bodies. Schindler (1977) reported that
the bottle bioassay experiments used to test the carbon limita-
tion theory were faulty in that they eliminated the turbulence
of water and its interaction with the overlying atmosphere and
because no attempt was made in the experiments to simulate the
proportion of alkalinity supplied by hydroxyl ions in natural
waters which affects the rate at which carbon is taken into the
aquatic ecosystem.
Shapiro (1973) has demonstrated that a shift from blue-green
algae to green algae resulted when C02 was added to their water.
Presumably, a shift from green algae to blue-green algae would
occur in natural waters as the CC>2 content of the water was
depleted. Shapiro concluded that this shift to blue-green algae
would likely occur because they appear to be more efficient in
utilizing C02 in waters of low C02 content. This shift in algal
types, rather than a general reduction in algal biomass, implies
that the total algal content remains relatively unaffected in
waters low in COy- Rather, there is a shift to blue-green algal
types because of their nutrient uptake kinetics in low CC>2 waters.
Thus, a low CC>2 content in natural waters will not necessarily
limit algal growth, but rather can shift the dominant algal types
from green to blue-green algae without significantly affecting
the overall primary productivity and algal biomass.
Recently James and Lee (1974) have shown similar results in
examination of inorganic carbon limitation in natural waters.
According to their model, inorganic carbon limitation could con-
ceivably occur inflow alkalinity waters. However, they also
indicate that the types, rather than quantities, of algae present
in a water body could be significantly affected by the amounts
and forms of inorganic carbon present. Under such conditions,
there may be no noticeable change in total algal biomass, even
though the inorganic carbon content of the water may drop to
apparently growth-limiting levels.
As a result of these above-mentioned studies, it is generally
accepted today among investigators that carbon will not usually
be a limiting nutrient in natural waters, except under certain
well-defined conditions. These special conditions would include
sewage lagoons, already eutrophic water bodies, laboratory flasks
with artificial media or special situations affecting the amounts
of available inorganic carbon, such as very low alkalinity lakes
or extremely hard water bodies (Goldman et al., 1972; James and
Lee, 1974). As such conditions occur infrequently in nature,
carbon limitation of total algal growth would be rare in most
natural waters.
In addition to the many works reported on the role of nitrogen
and phosphorus in the eutrophication of natural waters (Sawyer,
34
-------
1947; Hutchinson, 1957; Vollenweider, 1968; Lee, 1971; Vallentyne,
1974; Vollenweider and Dillon, 1974), it has also been observed
that these two nutrients are usually present only in small quan-
tities in natural waters during periods of excessive algal growths
(Mackenthun e_t aJL. , 1964, as cited in Fruh, 1967). Vallentyne
(1974) has indicated the special significance of nitrogen and
phosphorus among the 15 to 20 elements commonly needed for the
growth of aquatic plants by calculating the demand:supply ratios
of these essential elements. According to Vallentyne (1974),
aquatic plants have a certain demand for nutrients, for their growth
and reproduction, in proportion to the quantities of the nutrients
in their cells. When one or more of these nutrients is present
in short supply relative to the others, then the overall primary
productivity of the aquatic plant population will be limited by
the rates of supply of these nutrients. Thus, a "demand:supply"
ratio can reveal the nutrient most likely to limit productivity.
The higher this demand:supply ratio, the more a particular nutrient
will limit growth. The demand:supply ratios, based on a "world
average", were calculated by determination of the chemical composi-
tion of an average aquatic plant community and dividing this
composition by the mean chemical composition of the river waters
of the world. These demand:supply ratios are presented in Table 6.
The dominant role of phosphorus and nitrogen is clearly illus-
trated in Table 6 by their very high demand: supply ratios,
relative to all the other elements normally needed by aquatic
plants. This is especially prominent during the midsummer (i.e.,
during the growing season).
TABLE 6. DEMAND:SUPPLY RATIOS FOR THE MAJOR
AQUATIC PLANT NUTRIENTS
Demand:Supply
Element Late Winter Midsummer
Phosphorus 80,000 up to 800,000
Nitrogen 30,000 up to 300,000
Carbon 5,000 up to 6,000
Iron, Silicon Variable, but generally low
All other elements < 1,000
Prior to spring bloom
At algal maximum growth period
(Taken from Vallentyne, 1974)
35
-------
Thus, nitrogen and phosphorus are the two elements most often
found to be limiting aquatic plant growths. There have been a
few instances in which other elements have been found to have a
cause-effect role in limiting growth, including silicon (Schelske
and Stoermer, 1972) and iron (Welch et al . , 1975). However, the
overall importance of these exceptions is not comparable to the
dominant roles played by phosphorus and nitrogen in the eutrophica-
tion process.
Interaction Between Biotic and Abiotic Factors in Determining
Limiting Nutrients and Algae Nutrient Stoichiometry
It is a long-recognized principle in ecology that inter-
actions between organisms and their environment are reciprocal
(Redfield, 1958; Odum, 1971). The environment determines the
conditions under which an organism lives. Organisms respond to
changes in their physical environment by altering their metabolism
or growth requirements. Algae can directly influence their environ-
ment by changing the concentration of nutrients and other sub-
stances in the water by metabolic uptake, transformation, storage
and release. This is usually related to reciprocal changes in
algal biomass. This exchange between algal biomass and nutrient
concentration in natural waters is a cyclic process, which must
always be considered in any attempt to understand the chemistry
in aquatic environments (Redfield et al . , 1963; Stumm and Morgan,
1970).
This cyclical exchange is a two-phase process, including
synthesis and regeneration. With algae, the synthesis phase
consists of withdrawal of nutrients, especially nitrogen and
phosphorus, from the water during photosynthesis. These nutrients
are withdrawn from the water in the proportions required for
growth of the algae. The regeneration phase occurs when the
elements are returned to the water as decomposition products and
excretions of the algae, the higher trophic level species which
feed upon them and the microorganisms which decompose their
organic debris (Redfield et al . , 1963).
The proportions in which algal nutrients in natural waters
enter into the cyclical process described above is determined by
the elementary composition of the algal biomass. It is generally
accepted that algae need a relatively fixed atomic ratio of
carbon to nitrogen to phosphorus of 106 to 16 to 1 (i.e.,
(106C:16N:1P) (Redfield, 1958; Redfield et_ al . , 1963; Vollen-
weider, 1968; Ketchum, 1969; Lee, 1973). ThTs observation has
a basis in the simple Stoichiometry of the photosynthesis-
respiration reaction as it occurs in nature, as illustrated in
the following equation:
106 C02 + 16 N0~ + HPO* + 122 H20 + 18 H+ + trace elements
{c H 0 * p } + 138 0
< respiration --- 106 263 110 16 l
algal protoplasm
(Taken from Stumm and Morgan, 1970)
36
-------
The 106C:16N:1P atomic ratio was obtained from the early
work of Redfield (1934) and Fleming (1940), as cited in Redfield
et_ al. (1963), who examined the organic matter in plankton samples
obtained in sea water for the relative quantities of the principal
elements present in the plankton. The C:N:P atomic ratio values
represent an average of the carbon, nitrogen and phosphorus con-
tent present in phytoplankton and zooplankton, as illustrated in
Table 7.
TABLE 7. ATOMIC RATIOS OF C, N AND P PRESENT
IN PLANKTON
C N P
Zooplankton 103 16.5 1
Phytoplankton 108 15.5 1
Average Value 106 16 1
(Taken from Redfield et al., 1963)
In this discussion, attention is centered on nitrogen and
phosphorus since it is the relative quantities of these two
elements, rather than carbon, that is likely to limit or control
algal growth, and thereby the eutrophication process, presuming
all other physical and chemical factors are optimal for algal
growth.
The N:P ratios listed above may change as a function of the
aquatic environment. Harris and Riley (1956, as cited in
Redfield et al., 1963), studying plankton from Long Island Sound,
reported that while the average N:P atomic ratio in phytoplankton
in their study was 16:1, the average zooplankton N:P ratio was
24:1. Further, differences during the annual cycle varied as
much as 25 percent, with zooplankton having the highest N:P
ratios in winter and spring. Ketchum and Redfield (1949, as
cited In Redfield et al., 1963), using mass cultures of the
freshwater algae Chlorella pyrenoidosa, demonstrated that a wide
variation in the N:P~ ratio can occur under extremes of nitrogen
and phosphorus concentrations in the growth medium. In their
experiments, normal algal culture cells contained an N:P ratio of
about 6:1. By contrast, phosphorus deficient cells exhibited an
N:P ratio as high as 31:1, while nitrogen deficient cells would
show an N:P ratio of 3:1 or less.
Fuhs et al. (1972), using Cyc_lotella nana in laboratory
cultures, have shown that under severe phosphorus limitation,
the N:P ratio can rise to 35:1. It can drop to very low levels
37
-------
when nitrogen is limiting as a result of "luxury consumption" of
phosphorus. Fitzgerald (1969) has also demonstrated, with the
use of enzymatic and tissue assay procedures, that the N:P ratio
in algae and aquatic weeds can vary widely, depending on whether
nitrogen or phosphorus is present in excess in the growth medium.
However, while laboratory studies have demonstrated a
marked variation in algal N:P ratios because of the relative
quantities of nitrogen and phosphorus in the growth medium, field
studies have shown that rarely do such variations occur in natural
waters. Generally, neither phosphorus nor nitrogen are present
in natural waters in excessive quantities relative to the other.
Consequently, algae in natural waters do not usually contain
nitrogen and phosphorus in the ratios induced by the artificial
conditions of severe phosphorus or nitrogen limitation in the
laboratory studies. This is illustrated in examination of the
nitrogen and phosphorus content of algae from natural waters in
the southeastern US (Table 8).
TABLE 8. CHEMICAL COMPOSITION OF SOME ALGAE
FROM PONDS AND LAKES IN THE SOUTHEASTERN US
Algae N:P Atomic Ratio
Chara
Pithophora
Spirogyra
Giant Spirogyra
Rhizoclonium
Oedogonium
Mougeotis
Anabaena
Cladophora
Euglena
Hydrodictyon
Microcystis
Lyngbya
Nitella
22:1
20:1
33 :1
22 :1
18:1
73:1
16:1
27:1
9 :1
27:1
36:1
27:1
36 :1
27 :1
Amphizomenon 16:1
(Based on Federal Water Pollution Control Administration, 1968, as
cited in Goldman et al., 1972)
38
-------
Examination of Table 8 shows, with few exceptions, that in
general the N:P ratio of the algae varies between 16:1 to 27:1.
This ratio is smaller than the 35:1 ratio shown with Cyclotella
nana under severe phosphorus limitation in laboratory cultures
(Fuhs et al., 1972) and higher than that shown with Chlorella
pyrenoidosa under severe nitrogen limitation (Ketchum and
Redfield, 1949, as cited in Redfield et al., 1963). If the
minimum and maximum values are omitted, the mean N:P atomic ratio
of the algae is 24:1 (standard deviation = 8). Even if all
values are included, the mean N:P atomic ratio in Table 8 is
27:1 (standard deviation = 15). Thus, generally, algal popula-
tions in natural waters do not exhibit the extremes in cellular
N:P ratios seen in algal laboratory cultures.
Thus, even in spite of some variation, it is generally
accepted that the N:P atomic ratio in natural algal populations
remains constant enough to be used in making reasonable pre-
dictions as to which of these two elements is likely to limit
algal growths in natural waters.
The Limiting Nutrient Concept As Applied In The US OECD
Eutrophication Study
Presumably, as a result of the photosynthesis reaction,
algae will assimilate nitrogen and phosphorus from their aquatic
environment in a stoichiometric atomic ratio of approximately
16N:1P until one of these two nutrients becomes depleted in
the water body. At that time, the nutrient present in the water
body in the lowest concentration, relative to the stoichiometric
needs of the algae, will limit subsequent growth of the algae.
An examination of the water body at that time for its content of
nitrogen and phosphorus would indicate which of these nutrients
had been depleted by the algae (i.e., which nutrient was the
limiting nutrient). If the N:P atomic ratio in the water body
fell below 16, this would mean there were less than 16 nitrogen
atoms per each phosphorus atom in the water. Since this is
below the 16N:1P stoichiometric needs of the algae, the algal
biomass in the water body at that time would be controlled or
limited by the quantity of nitrogen present in the water body.
The amount of phosphorus present in the water body at that time
would have no influence, in terms of limiting algal growth, since
it would be present in excess quantities relative to the stoi-
chiometric requirements of the algae. The opposite would be true
if the N:P atomic ratio were greater than 16. Thus, an examin-
ation of the relative quantities of nitrogen and phosphorus in
a water body at a given time, especially during the growing season,
will indicate which of the two nutrients is "left over" after
the other has been depleted by the algae. Clearly, the nutrient
which is present in large quantities (i.e., left over) during
periods of excessive algal growths is not limiting growth of the
algae. Rather, the depleted nutrient is the one which would be
controlling or limiting the algal growth. Other algal metabolic
processes may also be occurring at the same time, such as luxury
39
-------
consumption of phosphorus in nitrogen-limited waters (Fitzgerald,
1969; Lee, 1973), but in general growth will be controlled by the
nutrient in the water body which has been depleted, relative to
the stoichiometric requirements of the algae.
Attention must be given to the forms of the nutrients avail-
able for algal and macrophyte growth, rather than to the total
nitrogen or phosphorus content of the water body. Cowen and Lee
(1976a) demonstrated that up to 30 percent of the particulate
phosphorus in urban runoff can be converted to algal-available
phosphorus (i.e., soluble orthophosphate) in about 20 days. In
addition, Cowen et al., (1976a) showed that up to 70 percent of
the organic nitrogen in urban runoff can be converted to in-
organic forms (i.e., NHn+NOo+NO^ as N) available for algal growth
in 35 to 50 days. Similar findings were shown with river waters
tributary to Lake Ontario (Cowen et al., 1976b). However, since
algal blooms are rapidly-occurring short-term events, it is the
quantity of the algal-available forms of nitrogen and phosphorus
present at any given time in a water body, rather than the
organic fraction, or the quantities of the total phosphorus or
nitrogen, that will determine which will be Limiting algal growths.
The available form of phosphorus in natural waters consists of
the soluble orthophosphate fraction. The available nitrogen
forms consist of ammonia, nitrate and nitrite.
The limiting nutrient concept, as illustrated in the N:P
ratio, has been applied to the US OECD water bodies. A summary
of the limiting nutrients in the US OECD water bodies, as
indicated by their respective principal investigators, is pre-
sented in Table 9. In addition, the US OECD water bodies were
examined for their content of available nitrogen and phosphorus
and the mass ratios of inorganic nitrogen:soluble orthophosphate
(as N:P) were determined. The mass ratios of N:P, rather than
the atomic ratios, were computed because of ease of directly using
the inorganic nitrogen and soluble orthophosphate concentrations
reported by the US OECD investigators. Since the concentration
volumes were the same, the inorganic nitrogen:soluble ortho-
phosphate mass ratio was the quotient of the inorganic nitrogen
concentration over the soluble orthophosphate phosphorus con-
centration. Incorporating the atomic weights of nitrogen and
phosphorus, an N:P atomic ratio of 16:1 corresponds to an N:P
mass ratio of 7.2:1. Using Selenastrum algal assays, Chiaudani
and Viglis (1974) have shown that at N:P mass rat-ios below 5:1,
nitrogen was limiting, while at N:P ratios of 10:1 or greater
phosphorus was limiting. Between N:P mass ratios of 5-10 either
could be limiting algal growth. In this discussion, the critical
N:P mass ratio was taken as 7-8:1. A similar N:P ratio was also
used by Schindler (1977) to define the limiting nutrient in his
whole-lake studies in the Canadian Experimental Lakes Area. The
N:P mass ratios of the US OECD water bodies are presented in
Table 10.
40
-------
TABLE 9. SUMMARY OF LIMITING AQUATIC PLANT NUTRIENTS
IN US OECD WATER BODIES
Water Body
Limiting Aquatic
Plant Nutrient3-
Blackhawk (E)u
Brownie (E)
Calhoun (E)
Camelot-Sherwood Complex (E)
Canadarago (E)
Cayuga (M)
Cedar (E)
Cox Hollow (E)
Dogfish (0)
Dutch Hollow (E)
George (0-M)
Harriet (E)
Isles (E)
Kerr Reservoir (E-M)
Lamb (0)
Meander (0)
Mendota (E)
Michigan (0-M)
Lower Lake Minnetonka (E+M)
Potomac Estuary (U-E)
Redstone (E)
Sallie (E)
P
P
P (summer)'
P
N-upper ends of both arms;
shifting to P-limitation as one
moves to lower ends of both arms
P-open waters;
most nearshore waters
N-some nearshore waters
with restricted circula-
tion
P (summer)
N-in upper £ middle
portions (summer)
P-in lower portion,
and in upper and middle
portions rest of year
("P appears not to be
limiting above a certain
level")
-------
TABLE 9. (continued) SUMMARY OF LIMITING AQUATIC PLANT
NUTRIENTS IN US OECD WATER BODIES
Water Body
Limiting Aquatic
Plant Nutrient3
Sammamish (M)
Shagawa (E)
Stewart (E)
Tahoe (U-0)
Twin Lakes (E)
Twin Valley (E)
Virginia (E)
Waldo (U-0)
Washington (E)
(M)
Weir (M)
Wingra (E)
P
P
P
N
P
P
P
P
N-
P-
P
P
(summer)
or other?
•(in mid-1960's)
.(prior to 1960's and in
recent years)
EXPLANATION:
aBased on investigators' estimates:
P=phosphorus-limited
N=nitrogen-limited
Investigator-indicated trophic state:
E^eutrophic
M=mesotrophic
0=oligotrophic
U=ultra
°Period during which nutrient was specified by investigator
to be limiting aquatic plant growth in water body,
Dash (-) = data not available.
-------
Table 10. MASS RATIOS OF INORGANIC NITROGEN TO
DISSOLVED PHOSPHORUS IN US OECD WATER
BODIES
Mass Ratios
(Inorganic Nitrogen : Dissolved Phosphorus)
Growing
Water Body Season Annual Other
Blackhawk (E)a 36C — 26e
(NH*+NO~+NO~ as N)
Brownie (E) < 5.5
(NK*+NO~ as N)
Calhoun (E)
-------
Table 10(continued). MASS RATIOS OF INORGANIC
NITROGEN TO DISSOLVED PHOSPHORUS IN US
OECD WATER BODIES
Water Body
Mass Ratios
(Inorganic Nitrogen:Dissolved Phosphorus)
Growing
Season Annual Other
Harriet (E)
(NH4+NO~ as N)
Isles (E)
(NH*+NO~ as N)
Kerr Reservoir (E-M)
(NH*+NO~+NO~ as N)
Roanoke Arm
Nutbush Arm
22
14
Lamb (0)
(NH4+N03+N02 as N)
Meander CO)
+
N)
Mer.dota (E)
(NH4+N00+NO~ as N)
28
11
20
Michigan
(NH*+NO~+NO~ as N)
Near shore (M) -- >100
Open waters (0) — 170
Minnetonka (E-*-M) Nitrogen Concentrations Not Determined
Potomac Estuary (U-E)
(NH*+NO:+NOT as N)
H o L.
Upper Reach 2-16
Middle Reach 1- 4
Lower Reach 1-15
Redstone (E)
(NH%NO"+NO~ as N) 38° -- 100€
4 ' o <-
(June-
Sept)
-------
Table 10 (continued). MASS RATIOS OF INORGANIC
NITROGEN TO DISSOLVED PHOSPHORUS IN US
OECD WATER BODIES
Mass Ratios
(Inorganic Nitrogen :Dissolved
Growing
Water Body Season Annual
Sallie (E)
(NH*+NO~+NO~ as N)
432
1972 4 3
1973 1
Sammamish (M)
(NO'+NO^ as N) 60 30
Shagawa (E)
(NH*+NO~+NO~ as N) 8 8
Stewart
(NH.+ +NO~+NOr as N) 108°
432
Tahoe (U-0)
(NHjt+NOl + NO" as N)
432
1973 > 2 > 4
1974 > 1
East Twin
(NH*+NOr+NO: as N)
432
1971 (E) -- 27
1972 (E) -- 19
1973 (E) — 21
West Twin
(NH. +N0~+N0l as N)
432
1971 (E) -- 28
1972 (E) -- 13
1973 (E) -- 14
Twin Valley (E)
(NH*+NO~+NO~ as N) 23C
Virginia (E)
(>,-H^NO-+NO- as II) 7C
Phosphorus)
Other
3f
—
--
8f
205e
—
—
—
—
—
—
—
--
27e
55e
-------
Table lO(continued). MASS RATIOS OF INORGANIC
NITROGEN TO DISSOLVED PHOSPHORUS IN US
OECD WATER BODIES
Mass Ratios
(Inorganic Nitrogen:Dissolved Phosphorus)
Growing
Water Body Season Annual Other
Waldo (U-0)
(NH*+NO~+NO~ as N) __ < 2
Washington
(NH*+NO~+NO~ as N)
1933 (E) 37 2
1957 (E) 21 60
1964 (E) 11 8
1971 (M) 13 30
Weir (M)
(NH*+NC~+NO~ as N) 2 3
Wingra (E)
(NH*+NO~ as N) 1? 16
EXPLANATION
Investigator-indicated trophic state :
E = ecutrophic
M = mesotrophic
0 = oligotrophic
U = ultra
(NH4+NO~+NO~as N)-nitrogen fractions considered in N:P
mass ratio calculations.
Summer epilimnetic concentration.
"Summer surface concentration.
el!ean winter concentration.
£
ASpring overturn concentration.
Dash (-) indicates no data available.
-------
Aquatic Plant Limitation in US OECD Water Bodies
Using algal assay procedures in most cases, the majority
of the US OECD investigators characterized their respective
water bodies as being phosphorus-limited (Table 9). The excep-
tions to this were ultra-oligotrophic Lake Tahoe (nitrogen-
limited) and the ultra-eutrophic Potomac Estuary (nitrogen-
limited in the upper and middle portions of the estuary, at
least in the summer months). In addition, Lake Washington was
considered nitrogen-limited in the mid-1960Ts, prior to diver-
sion of domestic wastewaters; it now appears to be phosphorus-
limited. Ultra-oligotrophic Lake Waldo has been shown to be
phosphorus-limited in in situ primary productivity experiments
(Powers e_t al. , 1972). However, Miller e_t al. (1974) were
unable to increase algal productivity in laboratory algal assays
with either phosphorus additions alone or phosphorus plus
nitrogen additions. Lake Michigan is believed to be nitrogen-
limited in some nearshore areas with restricted circulation,
such as southern Green Bay (Lee, 1974a). The Kerr Reservoir is
reported as being nitrogen-limited in its two upper arms, but
shifting to phosphorus limitation as one moves toward the lower
ends of both arms. Data for computing the N:P ratios were
unavailable for some water bodies (e.g., Brownie, Calhoun,
Cedar, Dogfish, George, Harriet, Isles, Lamb, Meander and
Sallie). However, with the exception of Lakes George and
Sallie, the nitrogen budgets of the above-listed water bodies
were not determined by their respective US OECD investigators,
implying these water bodies are phosphorus-limited. This
implication may or may not be true and may reflect the biases
of the investigators for these water bodies.
The inorganic nitrogen:soluble orthophosphate mass ratios
of the US OECD water bodies, on both an annual and growing
season basis, were presented in Table 10. Examination of this
table shows that, in general, the limiting nutrient designated
by the US OECD investigators for their respective water bodies
was substantiated by the inorganic nitrogen:soluble ortho-
phosphate mass ratio in the water bodies.
-------
There were, however, a few exceptions to this observation.
For example, Lakes Shagawa and Weir have both annual and growing
season inorganic nitrogen:soluble orthophosphate mass ratios of
8 or less. Yet both these water bodies are phosphorus-limited,
according to their respective investigators (Table 9). These
discrepancies can be explained to some degree by noting when the
ratios were determined. The period during which the ratio is
measured clearly will influence the results obtained. This is
best exemplified with the mass ratios for Lake Mendota. Its
annual inorganic nitrogen: soluble orthophosphate mass ratio of
5 indicates that the lake should be nitrogen-limited. Yet,
algal assay studies during the summer months clearly show Lake
Mendota to be phosphorus-limited during that period. Inorganic
nitrogen:soluble orthophosphate mass ratios determined during
the summer months would also have indicated a phosphorus-limited
water body.
Ultra-eutrophic Lake Sallie has an inorganic nitrogen:soluble
orthophosphate mass ratio of 3 or less during all times of the
year, indicating nitrogen limitation. According to Neel (1975),
phosphorus did not seem to limit algal growth "beyond a certain
point," in Lake Sallie, implying nitrogen limitation. Vollen-
weider (1975a; 1976a) has also reported that, even though phos-
phorus may initially be limiting algal growth, nitrogen may become
limiting beyond a certain advanced level of eutrophication.
Miller et al. (1974), studying primary productivity in 49 water
bodies,~reported that, in general, phosphorus limitation decreas-
ed in the water bodies as the primary productivity index increas-
ed. Vollenweider (1975a) has presented evidence that this shift
to nitrogen-limitation may be due to increasing denitrification
in highly eutrophic water bodies. According to Vollenweider
(1975a; 1976a), this point is reached when the nitrogen residence
time:phosphorus residence time ratio in the water body drops be-
low a value of one. The nitrogen residence time:phosphorus resi-
dence time ratio , therefore, also offers a simple method for de-
dermining the aquatic plant growth limiting nutrient in a water
body. With specific reference to Lake Sallie, another factor
which should be considered in determination of its limiting
nutrient is that its excessive aquatic plant growths are manifested
mainly in macrophyte growths. The application of the N:P ratio
concept to Lake Sallie is likely not valid because it would
not account for that portion of the nutrients obtained through
macrophyte root systems in the sediments. The mean inorganic
48
-------
nitrogen:soluble orthophosphate mass ratios in Table 10 indicate
the Kerr Reservoir to be phosphorus-limited during all times of
the year. However, Weiss and Moore (1975) reported that the Kerr
Reservoir is initially nitrogen-limited in the upper ends of
both arms, and shifts to phosphorus-limitation as one moves
toward the lower ends of the two arms (Table 9). This inconsis-
tency may be due to the fact that the upper ends of both arms of
the Kerr Reservoir receive heavy sediment loads. Weiss (1977)
has indicated that there may be a considerable degree of adsorption
of phosphate on the clays of the heavy sediment load, producing
low phosphate concentrations in the upper ends of the two arms
and resulting in nitrogen-limitation. According to Weiss, this
may illustrate a problem of assessing limiting nutrients in
waters which have frequent incursions of Fe- and Al-rich sediments.
In summary, the use of the N:P ratio approach to estimate
potential algal growth limitation by nitrogen or phosphorus re-
quires examination of this ratio over the annual cycle. Particu-
lar attention should be given to those periods of the year when
excessive planktonic algal growth causes significant water dete-
rioration. For many water bodies this usually corresponds to
the summer months, when the water body is being extensively used
for recreational purposes. It is not the limiting nutrient over
the annual cycle that is of importance in determining what nutri-
ent should be considered in remedial treatment of the nutrient
loading to a water body. Rather, the growing season is the
period of primary concern, since algal growths during the non-
growing season are seldom of consequence in terms of eutrophica-
tion control in natural waters. Also, algal growths may be
limited by one nutrient during the summer months, or the growing
season, and another nutrient over the annual cycle. As mention-
ed earlier, Lake Mendota exhibited such a trend.
Attention should be given to the forms of the nutrients
available for algal growth rather than the total element content ,
since the algal growth in a water body at any given time is
limited by the algal-available ni^rogen and phosphorus forms in
the water body rather than the total nutrient content. Caution
should be used in estimating nitrogen or phosphorus limitation in
situations where the inorganic nitrogen:soluble orthophosphate
ratio in the water body is near the normal stoichiometric ratio of
algae (atomic N:P ratio of 16:1 or mass ratio of 7.2:1) because
both nitrogen and phosphorus concentrations are in a constant
state of change. A particular ratio that exists at one time may
be markedly altered by the different rates of supply of the
available forms of these elements from both internal and external
sources and their utilization or transformation to available
forms.
-------
Even with the above-mentioned limitations, the use of the
inorganic nitrogen:soluble orthophosphate ratio represents a
reasonably accurate method for determining the limiting nutrient
in a water body. This chemical approach for determining the limit-
ing nutrient in natural waters is likely to be less expensive
than bioassay procedures and will yield equally meaningful re-
sults in predicting algal growth potential when interpreted
properly. Further, bioassay procedures do not take into account
many of the factors that would influence the availability of
nitrogen and phosphorus in a water body. In addition to the re-
sults of the US OECD water bodies in promoting this approach,
Lee (1973) has reported that the use of the inorganic nitrogen:
soluble orthophosphate ratio in determining the limiting nutrient
has also worked reasonably well in Lake Superior and the lower
Madison, Wisconsin, lakes. When proper precautions are exercised
in determination of this ratio, it represents a relatively simple
method for making reasonable predictions as to what nutrient
(i.e., nitrogen or phosphorus) is likely to limit algal growth
in most natural waters.
APPROACHES USED IN US OECD EUTROPHICATION STUDY
Initial Vollenweider Phosphorus And Nitrogen Loading Diagrams
Although nutrient loading and nutrient concentration are
related, it is recognized that the nutrient concentration actual-
ly controls the al'gal and, -to some extent, macrophyte standing
crops in a given water body, and thereby the eutrophication
process. However, many factors directly and indirectly affect
the relationship between nutrient loading and the resultant
nutrient concentration (Vollenweider, 1968). Furthermore, from
the point of view of eutrophication control, the nutrient load-
ing to a water body is more easily managed than the nutrient
concentration within a water body. It was the loading approach
that was adopted for the US OECD eutrophication study.
Sawyer (1947) was among the first to use the concept of
nutrient loading in his studies of the effects of agricultural
50
-------
and urban drainage and wastewaters on the fertility of the Madi-
son, Wisconsin, lakes. He made the observation that the lake
which received the greatest quantity of phosphorus and nitrogen
on an areal basis experienced the most frequent and most severe
algal blooms.
Rawson (1955) and Edmondson (1961) emphasized the importance
of mean depth (a measure of the volume related to unit surface
area) to the productivity of water bodies. In any evaluation of
areal loading, this parameter took into account the degree of
dilution and its effect on the nutrient concentrations in deeper
bodies of water. Inclusion of mean depth in the evaluation of
productivity also allowed for the role of the thermocline in in-
fluencing nutrient recycling from sediments (Stauffer and Lee,
1973).
Vollenweider (1968) quantitatively defined the relationship
between nutrient loading and planktonic algal trophic response and
devised a loading relationship based on these components. When
Vollenweider plotted the surface area total phosphorus loading
(g P/m2/yr) or total nitrogen loading (g N/m^/yr) versus the
mean depth (m) on a log-log scale, he found that water bodies of
similar trophic states appeared in the same general areas of the
diagram (Figure 5). This same relationship was also derived for
nitrogen loadings (Figure 6), assuming algal nitrogen require-
ments were related to phosphorus requirements in the ratio of
15:1 by weight. According to Vollenweider (1977), while this is
about twice the mass ratio generally accepted, he felt this high
N:P ratio applied to loading (not concentration) appeared to be
more appropriate, and probably included effects of denitrification
which reduces the available nitrogen (in terms of concentration)
relative to phosphorus. Boundary loading conditions, theoretically
based on Sawyer's spring overturn critical nutrient concentrations
(Vollenweider, 1968; Vollenweider and Dillon, 1974), were incor-
porated into the diagrams, which grouped the lakes into the three
standard trophic states (i.e., oligotrophic, mesotrophic and eu-
trophic). The lower bounary line ("permissible") designated the
maximum phosphorus or nitrogen loading levels, as a function of
mean depth, that a given water body could tolerate and still retain
its oligotrophic character. The upper boundary line ("excessive")
represented the phosphorus or nitrogen loading level, as a function
of mean depth, above which a given water body would be characterized
as eutrophic. The zone separating the oligotrophic and eutrophic
categories represented the mesotrophic category. This was consid-
ered a transition zone between the oligotrophic and eutrophic cate-
gories .
The approximation for the permissible loading boundary
condition was empirically determined to be
LC(P) = 25 z°'6 (1)
51
-------
10
a
o
z
o
s
CO
D
tr
o
i
a.
to
o
i
a.
p
0.01
EUTROPHIC ZONE
NO
MESOTROPHIC ZONE
X
X
E» W Z
MA«
• /»AN X
• T X X
X X
EXCESSIVE LOADING
V
X
X
LOADING
TA
OLIGOTROPHIC ZONE
(FROM VOLLENWEIDER.I968)
10
100
1000
KEY TO LAKES
TA-TAHOE
A- AEGERISEE
V - VANERN
L -LE.MAN
0-ONTARIO
BO-CONSTANCE
AN-ANNECY
MEAN DEPTH (m)
MA-MALAREN
T-TURLERSEE
F-FURES
S- SEBASTICOOK
H-HALLWILERSEE
MO-MOSES
MO- NORRVIKEN
E - ERI E
P- PFAFFIKERSEE
G- GRIEFENSEE
B-BALDEGGERSEE
W- WASHINGTON
2- ZURICHSEE
Figure 5. Vollenweider's Total Phosphorus Loading
and Mean Depth Relationship.
52
-------
1000
o«IOO
o
z
Q
LJ
O
O
o:
10
I-
o
EUTROPHIC
ZONE
I FROM VOLLENWEIDER.I968)
> MAL
WA
L- N
PERMISSIBLE
LOADING
^MESOTROPHIC
ZONE
OLIGOTROPHIC
ZONE
TA
10
KEY TO LAKES
P- PFAFFIKERSEE
Z- ZUR1CHSEE.UNTERSEE
H- HALLWILERSEE
B-BODEN-OBERSEE
MEAN DEPTH (m)
ZE-ZELLERSEE
MAL-MALERN
N- NORRVIKEN
L-N LOUGH NEAGH
100 1000
MEN - MENDOTA
TA -TAHOE
WA - WASHINGTON ( 1957)
Figure 6. Vol1enweider's Total Nitrogen Loading and
Mean Depth Relationship.
53
-------
where L (P) = areal permissible total phosphorus
c loading (mg P/m2/yr); and
z = mean depth (m).
The excessive loading boundary condition was considered to be
approximately twice the permissible loading (Sakamoto, 1966;
Vollenweider, 1968; 1976a; Dillon, 1974a; Dillon and Rigler,
1974a) as follows : '
L(P) = 50 z0>6 (2)
where L(P) = areal excessive phosphorus loading
(mg P/m2/yr)
Assuming an N:P loading ratio of 15:1 by weight (Vollenweider,
1968), then the permissible and excessive loading lines, respect-
ively, for nitrogen are determined by similar reasoning as:
L(N) = (15) (25 or 50) z°'6 (3)
2
where L(N) = areal nitrogen loading (mgN/m /yr).
The slope of the boundary lines indicated the greater dilution
capacity of deeper water bodies, which influences their ability to
assimilate more nutrients than shallower lakes without increasing
their degree of fertility. A water body's relative degree of
eutrophy or oligotrophy on either loading diagram was proportionate
to its vertical displacement above or below the "permissible"
loading line. Thus, in Figure 5, Lake Moses is relatively four
times more eutrophic than Lake Sebasticook in terms of phosphorus
loadings. Likewise, Lake Aegerisee is relatively more oligotrophic
than Lake Vanern, based on their respective phosphorus loading and
mean depth characteristics (Vollenweider and Dillon, 1974).
This model marked a significant advance in eutrophication
studies and became widely accepted as a guide to the degree of
eutrophy of a given water body. It was the first credible quan-
titative guide to "permissible" and "excessive" phosphorus and
nitrogen loading levels for lakes and impoundments. That is,
for most of the water bodies for which sufficient phosphorus
loading data were available, the trophic state predicted by the
Vollenweider loading diagram agreed with the trophic state in-
dicated by the standard, but arbitrary, indicators available at
the time (e.g., nutrient concentrations, chlorophyll concentra-
tions, primary productivity, Secchi depth, hypolimnetic oxygen
depletion, etc.).
The Vollenweider phosphorus loading diagram was subsequently
used in a number of studies to describe or predict the degree of
eutrophy in various waters as a function of phosphorus loadings.
For example, the International Joint Commission (1969) and
Patalas (1972) used it to describe the trophic conditions of the
54
-------
Great Lakes. Schindler and Nighswander (1970) used it to describe
Experimental Lake 227 in their nutrient enrichment studies in north-
western Ontario. In fact, it still appears in the literature in
this form even today.
However, Vollenweider (1968; 1975a) stated that his initial
phosphorus and nitrogen loading diagrams were only approximate
relationships and that other parameters would also have to be
considered in establishing a water body's trophic status. These
factors included the extent of shoreline and littoral zone, degree
of nutrient mixing in the water column, internal loading from
the sediments, and especially water renewal time (Vollenweider
and Dillon, 1974). Vollenweider (1975a) noted that his initial
model, though it worked reasonably well for hydraulic residence
times of several months, did not account for the situation that
two water bodies could have identical mean depths , but different
hydraulic residence times. Water bodies with shorter hydraulic
residence times (i.e., faster flushing rates) would also have fast-
er cycling of water through the systems. A water body with a fast-
er flushing rate could assimilate a larger nutrient loading, with
no adverse eutrophication responses , than a slower flushing lake
because of a generally faster nutrient washout which could result
in a "short-circuiting" of input nutrients before they have had
sufficient time to interact with the algal populations in the fast-
er water body. Edmondson (1961; 1970a) pointed out that a lake
receiving nutrients supplied in a diluted form (such as land runoff)
would be affected differently than one receiving its nutrients in
a concentrated form (such as domestic sewage inputs).
Dillon (1974a, 1975) was the first to report water bodies
which did not fit Vollenweider's original phosphorus loading dia-
gram scheme. In his study of the phosphorus budgets of nineteen
southern Ontario lakes, he found a number of them had phosphorus
loadings and mean depth characteristics which would place them
in Vollenweider's eutrophic category on his loading diagram
(Figure 5); yet they also had large Secchi depths, low chlorophyll
concentrations and no significant hypolimnetic oxygen depletion.
Dillon attributed this discrepancy to the fact that the ratios
of their drainage areas to surface areas were very large. This
factor and their low mean depths gave them very high flushing
rates. Dillon concluded the anomalous fit of these water bodies
on the Vollenweider phosphorus loading diagram was a result of
their rapid flushing rates.
Vollenweider Phosphorus Loading and Nitrogen Loading
Versus Mean Depth/Hydraulic Resjdence 'Time Relationships
In an attempt to allow for the effects of fast or slow flush-
ing rates on the nutrient loading-trophic response relationships
in natural waters, Vollenweider (1975a; 1976a; Vollenweider and
Dillon, 1974) modified his phosphorus loading diagram to include
the hydraulic residence time (i.e., water body volume/annual
55
-------
inflow volume). This modification was based on an input-output
model involving the behavior of non-conservative substances in
water bodies (Vollenweider, 1975a, Dillon, 1974b). This modifica-
tion allowed the effects of hydraulic loading (as contrasted to
nutrient loading) to be included along with the nutrient loading
and morphometry parameters of his initial loading diagram.
Vollenweider focused his attention on modifying only the phos-
phorus loading diagram. He singled out phosphorus for attention
because it is generally believed to be the aquatic plant nutrient
most frequently controlling eutrophication in natural waters
(Sawyer, 1966; Fruh et al., 1966; American Water Works Association,
1966; 1967; Vollenweider, 1968; 1975a; 1976a; Lee, 1971; 1973;
Likens, 1972a; Vallentyne, 1974; Vollenweider and Dillon, 1974; US
EPA, 1976a; 1976b). Furthermore, the phosphorus input to a water
body is usually technologically easier to control than the nitrogen
input. Much of the phosphorus supplied to water bodies is intro-
duced by way of point sources, such as in domestic or industrial
sewage. Nitrogen, while supplied from point sources, is often also
introduced in large quantities from non-point (diffuse) sources,
such as land runoff, precipitation, dry fallout and nitrogen fixa-
tion. These diffuse sources are usually far more difficult and
expensive to control. In general, then, it is believed that the
control of phosphorus loading' to a water body is technically and
economically more feasible than control of nitrogen loading. Con-
sequently, Vollenweider focused on modifying his phosphorus load-
ing diagram. Vollenweider's approach of concentrating on the phos-
phorus loadings to water bodies was recently given support by the
general assemblies of both the International Limnological Congress
and the International Ecology Congress, both of which unanimously
passed resolutions recommending widespread phosphorus control as a
solution to eutrophication (Schindler, 1977).
Vollenweider (1975a; 1976a) modified his relationship to in-
clude the hydraulic residence time. In this report, the hydraulic
residence time is defined as the ratio of the water body volume
(m^) to the annual inflow volume (m^/yr) and represents the lake
filling time. The hydraulic residence time could also have been
defined as water body volume divided by annual outflow volume
since the majority of the US OECD water bodies are in the north-
central and northeastern US. It is generally held that precipitation
and evaporation are approximately equal over the annual cycle in
these areas. Thus, the hydraulic residence times, computed using the
inflow volumes would presumably not be significantly different from
those obtained using the outflow volumes (the importance of this par-
ameter was recently illustrated by Piwoni et al. (1976) in their
evaluation of the trophic state of Lake Michigan. Two different hy-
draulic residence times were computed, depending on whether outflow
alone or outflow plus deep return flow during stratification were
considered in the computations. The reader is referred to Piwoni
et al. (1976) for a detailed discussion of this problem). Vollen-
weider Ts modification was to plot a water body's areal total phos-
phorus loading (g P/m^yr) versus its ratio of mean depth (m) to
56
-------
hydraulic residence time (yr) . This ratio was represented as
Z/TW. With this relationship, the critical phosphorus loading of
comparable lakes is directly proportional to their mean depths, and
indirectly proportional to their hydraulic residence times. The
direct proportionality of the critical phosphorus loading to the
mean depth relates to the dilution of the phosphorus input by the
water body volume. The reciprocal proportionality of the critical
phosphorus loading to the hydraulic residence time relates to the
likely residence time of the input phosphorus in the water body.
It was apparently Vollenweider ' s intent that the variables of mean
depth and flushing rate be considered in this modification. However,
Z/TW equals the hydraulic load, qs (m/yr) , per unit water body
surface area. Thus, it appears that mean depth, as an independent
parameter, is lost in part. Vollenweider ' s phosphorus loading versus
mean depth/hydraulic residence time relationship is presented
graphically in Figure 7. As with Vollenweider ' s original phosphorus
loading diagram (Figure 5) phosphorus boundary loading lines based
on Sawyer's (1947) critical nutrient concentrations, and represent-
ing the permissible and excessive phosphorus loading levels , have
been drawn into Vollenweider ' s modified phosphorus loading diagram.
According to Vollenweider (1976a), from a simple inspection of lakes
plotted using this modified approach, the phosphorus loading criteria
for separating oligotrophic from eutrophic lakes was as follows :
L (P) = (100) (Z/T )°'5 (U)
C CO
where L (P) = areal permissible total phosphorus
loading (mg
z = mean depth (m) , and
T = hydraulic residence time = water body
volume (irr) /annual inflow volume (m^/yr).
As before, the excessive phosphorus loading was assumed to be
equal to twice the permissible loading (Sakamoto, 1966; Vollen-
weider, 1975a, 1976a; Dillon, 197"4a). Thus water bodies
plotting above the excessive loading line are generally eutrophic
while those plotting below the permissible loading line are
generally oligotrophic, based on their phosphorus loadings and
mean depth/hydraulic residence time characteristics. A detailed
derivation of this approach is presented in Vollenweider (1975a).
It is this version of Vollenweider ' s model which was proposed
by the US EPA (1975b, 1976a) as a basis for determining critical
phosphorus loadings for US lakes and impoundments . A further
modification of Vollenweider ' s model involves the position of
the permissible and excessive loading lines in his loading dia-
gram. This new modification, in the opinion of these reviewers, .
57
-------
10
EUTROPHIC
ZONE
EXCESSIVE
LOADING
e
•x.
QL
•PERMISSIBLE
LOADING
en
CO
ID
2
O
<
O
cr
o
CO
O
X
0.
0.
0.01
0.
OLIGOTROPHIC
ZONE
(FROM VOLLENWEIDER, I975a)
I
I
I _ 10 100
MEAN DEPTH,Z/HYDRAULIC RESIDENCE TIME,TO, (m/yr)
Figure 7.
Initial Vollenweider Total Phosphorus Loading and
Mean Depth/Hydraulic Residence Time Relationship.
1000
-------
marks a further refinement of Vollenweider's approach for deter-
mination of critical phosphorus loadings for lakes and impound-
ments. The derivation of this new modification is presented in
the following section.
Based on earlier work by Biffi (1963) and Piontelli and
Tonolli (196^), Vollenweider (1975a; Dillon, 197i+b) developed a
mass balance model for total phosphorus in natural waters. As
such, it was an accountability model concerned with the balance
of phosphorus between its sources and sinks. In addition to the
initial mean depth parameter, this model included terms for the
hydraulic residence time and a sedimentation parameter. Vollen-
weider 's model indicated that the phosphorus dynamics of a water
body can be expressed as:
d[P]/dt r Phosphorus Load minus Outflow Loss minus
Sedimentation Loss
= (Zu.[P]./V) -a[P]-pw[P] (5)
_3
where [P] = lake total phosphorus concentration (ML ) ,
u. = flow rate of the jth tributary (L3?'1),
[P]. = phosphorus concentration in j tribu-
tary (M L~3),
3
V = lake volume (L ),
p = hydraulic flushing rate (= annual inflow
volume/lake volume) (T ), and
_]_
a = phosphorus sedimentation coefficient (T ).
P
Vollenweider assumed a completely mixed reactor model of constant
volume in which the outflow phosphorus concentration was equal to
the in-lake phosphorus concentration. He further assumed the
water body had equivalent inflow and outflow rates and that there
was no internal loading of phosphorus to the water column from
the sediments. He also assumed that phosphorus sedimentation
was proportional to the phosphorus concentration in the water
body, rather than to the phosphorus loading.
59
-------
The time-dependent solution to this model is:
[PL ~- CPL e-(pw%)(t-to) + (£(P)/(p +a ))(l-e-(pa)+ap)(t-to)
T- "-o to p
(6)
The steady state solution (i.e., t->») to this model (Vollen-
weider, 1975a; 1976a) is
(pw + ap) (7)
where [P]^ = steady state total phosphorus concentration
(M L~3) , and
HP) = volumnar phosphorus loading
(M L~3 T'1) = SU.[P]./V
Now, £(P) = L(P)/z, where L(P) = areal total phosphorus loading
and z = mean depth. Therefore, Equation 7 above becomes
[P] = L(P)/(z(p + a ))
00 ti) p
Equation 8 can then be arranged as
UP) = [P]w • i(pu + ap). (9)
can be taken for simplicity as Sawyer's (1947) ^
critical spring overturn phosphorus concentration of 10 mg/m .
The hydraulic flushing rate, pw , is equal to I/hydraulic
residence time (= I/TW) . The phosphorus sedimentation rate
coefficient, ap, cannot easily be measured directly. However,
Vollenweider (1975a; 1976a) has indicated as a general rule
that c?p can be approximated by
a = 10/z. (10)
P
Thus, Equation 9 becomes
60
-------
Lc(P) =
ap)
= (10 mg/m3)(z/Tw + z (10/z))
= 100 +(10 (Z/T ))
to
(11)
where L (P)
c
OJ
areal permissible total phos-
phorus loading (mg P/m?/yr),
z = mean depth (m),
hydraulic residence time (yr) = lake
volume (m^) /annual inflow volume (rn^/yr) , 2nd
] = critical concentration of total phosphorus at
spring overturn = 10 mg/rn^.
As with the earlier model, the excessive phosphorus loading
boundary condition was considered to be approximately twice the
permissible loading (Sakamoto, 1966; Vollenweider, 1968; 1976a;
Dillon, 1974a; Dillon and Rigler; 1974a). Thus, the equation for
the excessive loading line becomes
L(P) = 200 + (20
(12)
where L(P) = excessive phosphorus loading (mg P/m^/yr).
These equations, theoretically based on Sawyer's (1947) critical
spring overturn phosphorus concentration, serve as the basis for
the modified phosphorus loading and mean depth/hydraulic
residence time diagram presented in Figure 8. Vollenweider's
modified phosphorus loading diagram (Figure 8) indicates that
below a certain combination of mean depth and flushing, the
phosphorus loading tolerance of a given water body becomes con-
stant in spite of the fact that, based on mean depth alone,
water bodies may appear to have a higher assimilation capacity.
This is not indicated in his previously reported loading diagram
(Figure 7). In this new modified phosphorus loading diagram,
the boundary lines flatten out at Z/TW values of <2. In addi-
tion, at Z/T^ values >80, the tolerable loading capacity becomes
proportional to Z/T^, which is contrary to what was found with
his original model (Figure 7).
61
-------
10
CD
ro
E
CL
a>
O
z
Q
<
o
(T
O
I
o
I
Q.
0.01
EUTROPHIC
ZONE
/ LOADING
/ /PERMISSIBLE
/ / LOADING
X
X
( FROM VOLLENWEIDER, I975o )
I I I I I 1 I I I
OLIGOTROPHIC
ZONE
Mil
I I I I
0.1
10
MEAN DEPTH,Z/HYDRAULIC RESIDENCE TIME,TW
100
( m/yr)
1000
Figure 8. Modified Vollenweider Total Phosphorus Loading and
Mean Depth/Hydraulic Residence Time Relationship.
-------
— -
A total nitrogen loading (i.e., NHt+N0,.+N0? + organic
nitrogen) and mean depth/hydraulic residence time diagram
has also been prepared for analysis of the US OECD eutrophica-
tion study data. The nitrogen loading diagram is identical in
form to the phosphorus loading diagram except that it contains
no permissible or excessive loading lines. The criteria for
the positioning of the permissible and excessive boundary lines
are currently being derived for water bodies which are nitrogen-
limited, or which can be made nitrogen-limited with respect to
aquatic plant nutrient requirements. The development of the
permissible and excessive loading boundary conditions is neces-
sary so that the type of relationship developed by Vollenweider
for examining the trophic conditions of water bodies based on
their phosphorus loadings and mean depth/hydraulic residence
time characteristics can be applied to water bodies which are
nitrogen-limited.
Emphasis on Phosphorus Loading Relationships
Vollenweider has continued to modify and improve his phos-
phorus loading relationships during the past several years.
Moreover, others (Dillon, 1975; Larsen and Mercier, 1976) have
proposed additional parameters to be considered in any evalua-
tion of a water body's productivity and general trophic condi-
tion. These new models, to be used later in this report, are
discussed in the following sections.
In all subsequent loading diagrams in this section, at-
tention is given mainly to phosphorus loading relationships.
Relationships between nutrient loadings and water body trophic
response and water quality parameters are explored in later sec-
tions of this report. However, all the loading diagrams in this
section relate phosphorus loadings to either influent phosphorus
concentrations, chlorophyll concentrations or retention coeffi-
cients. The originators of the various loading diagrams them-
selves derived their loading-response relationships only for
phosphorus loadings. Vollenweider (1975a) reported his concen-
tration on phosphorus loadings stemmed from "...the relatively
scant knowledge we have about other factors, e.g., nitrogen."
In addition, the majority of the US OECD water bodies were
characterized as being phosphorus-limited with respect to
aquatic plant requirements. Consequently, all the subsequent
loading diagrams refer to phosphorus loadings. It is assumed
that the same relationships could be derived for nitrogen load-
ings. However, the originators of the subsequent loading dia-
grams made no attempt to do so.
Vollenweider Critical Phosphorus Loading Equations
Concurrent with his phosphorus loading diagrams, Vollen-
weider derived additional methods for calculating critical
63
-------
phosphorus loadings to water bodies. The first approximations
(Vollenweider, 1976a) of the critical phosphorus loading range
were given earlier in Equations 1, U- and 11. Water bodies re-
ceiving a phosphorus loading below this permissible phosphorus
loading estimate (Figures 5, 7 and 8) would be considered oligo-
trophic, while water bodies receiving at least twice this per-
missible loading would be considered eutrophic (Vollenweider,
1976a; Vollenweider and Dillon, 1974-).
Vollenweider (1976a) has derived a more general relation-
ship from Equation 9. Vollenweider (1976a; Sonzogni et al. ,
1976) has incorporated the concept of phosphorus residence" time
as a reference parameter for determining critical phosphorus
loads. Vollenweider has included this parameter in this refine-
ment of his critical phosphorus loading equation in an attempt to
compensate for the loss of mean depth as an independent criterion
for assessing the effects of phosphorus loading on a water body.
According to Vollenweider (1976a), the concept of phosphorus
residence time can be approximated in the same manner as the
hydraulic residence time, or theoretical filling time, of a water
body (i.e., T = water body volume/annual inflow volume).
Determination of the residence time of any substance entering
a water body requires only -the knowledge of the loading of that
substance to the water body and the mean concentration of that
substance in the water body during the same time interval. Thus,
for phosphorus
T =[p]./£(P) (13)
P *
where T = phosphorus residence time (T),
[PL= mean in-lake phosphorus concentration (M L~ ) and
-3 -1
£(P) = volumnar phosphorus loading (ML T ).
Equation 13 defines the hypothetical time necessary to bring the
phosphorus concentration of a water body to its present level
starting from a zero phosphorus concentration in the same manner
that the hydraulic residence time, as used in this report, de-
fines the theoretical "filling time" of a water body. This same
approach was used by Sonzogni et al. (1976) in development of a
phosphorus residence time recovery model. This model will be
discussed in a later section of this report.
However, Vollenweider (1976a) has noted that the phosphorus
loading is not independent from the hydraulic loading. The only
exception to this observation would be instances where the phos-
phorus loading is a direct input(s) of high concentration, and
64
-------
thus only marginally accounts for the total hydraulic loading.
Therefore, Vollenweider concluded that it would be more meaning-
ful to consider the phosphorus residence time relative to that
of water.
Therefore,
TT = T /T = ( [PL /£(P))/(V/Q) (14)
r p to A
-- [PL/[P].
where TT = phosphorus residence time relative to
hydraulic residence time (T T"-'-),
T = hydraulic residence time (T);
3
V = lake volume (L )?
3 —1
Q = inflow volume (L T ),
_ Q
[P].= mean inflow phosphorus concentration (ML ) and
_ 2
[P] = mean in-lake phosphorus concentration (M L ).
A
In analyzing the dependence of tp on T^ for a wide range of water
bodies, Vollenweider (1976a) has noted that Tp/Tw is neither in-
dependent nor inversely proportional to TW. Rather, Tp/Tw
tends to decrease as TW increases. He has determined that the
relative phosphorus residence time depends on the hydraulic resi-
dence time by a statistical relationship which results in the
following equation,
TT =T/T =p/(p +a) (15 )
r p co to to p
where p = hydraulic flushing rate (T ) = 1/t , and
a = phosphorus sedimentation coefficient (T )
However, Vollenweider (1976a) has also noted that for lakes of
less than 20 m mean depth and/or rapid flushing rates this rela-
tionship between T-p/T^ and T^ cannot be linearly extrapolated
below T <1 .
65
-------
An approximation which takes care of this problem is
T /T(o = 1/C1 + 7z/qs)
(16)
Equations 15 and 16 can then be combined as follows,
T /T = P /(p + a ) = 1/(1 + /T~). (17)
p co w co p v co
Equation 17 can then be solved for the sedimentation rate coef-
ficient , a , as follows,
' p'
a = JT~/T = /z/q /T (18)
p Y co to * Hs to
If this estimate of ap is inserted into Equation 9, a more
generalized relationship is obtained for determining critical
phosphorus loads which holds over the entire spectrum of combina-
tions of mean depth and hydraulic loadings. This relationship
is derived as follows,
= 10 • q (1 + /z/q ) (19)
J
where [P] ^ - Sawyer's (1947) critical spring overturn
phosphorus concentration = 10 mg/m^,
z = mean depth (m),
T = hydraulic residence time (yr) , and
q = hydraulic loading (m/yr) = Z/T .
66
-------
This equation expresses the phosphorus loading tolerance in terms
of the morphometry of the water body (condensed into the term of
mean depth, z) , and the hydrologic properties of the water body
(expressed as hydraulic loading, qs). Thus, in principle, the
phosphorus loading tolerance of a water body can be considered
as a function of its mean depth and hydraulic loading (Vollen-
weider, 1976a).
This relationship has been developed by Vollenweider into
the form of two equivalent diagrams (Figures 9 and 10). In
Figure 9, the permissible phosphorus loading, LC(P), is plotted
against mean depth and parameterized as a function of the hy-
draulic loading, qs. In Figure 10, LC(P) is plotted against the
hydraulic load and parameterized as a function of mean depth, z.
Vollenweider PhosphorusLoading Characteristics and Mean Epilimnetic
Chlorophyll a Re la t Ton ship" ~~
Equations 8 or 19 can be rewritten in terms of the relation-
ship between the phosphorus loading and the resultant phosphorus
concentration in the water body, rather than in terms of critical
phosphorus loading levels.
Recalling that p = I/T , a = JT 7r and T = z/q , Equation 8
& co co' p V co co to Hs'H
can be rearranged as follows:
[P] = (L(P)/q ) (1/(1 + /z/q )) (20)
^^ o o
Equation 20, therefore, relates the predicted in-lake phosphorus
concentration (assuming a steady-state condition) to an equiva-
lent expression involving the phosphorus loading as modified by
the hydraulic load. According to Vollenweider (1975a; I976a)
L(P)/qs represents the average inflow phosphorus concentration.
This useful relationship will be used in a later portion of this
report to check the phosphorus loads reported for the US OECD
eutrophication study water bodies.
Several authors (Sawyer, 1947; Sakamoto, 1966; Dillon, 1974a;
Dillon and Rigler, 1974a; Bachmann and Jones, 1974; Jones and Bachmann,
1976) have shown that a relationship exists between the phosphorus
concentration at spring overturn and the mean chlorophyll con-
centrations in a water body during the following summer growing
season. Since a positive correlation has been shown to exist be-
tween spring overturn phosphorus concentration and average summer
chlorophyll concentration in a water body, it is logical to assume
a positive correlation may exist between phosphorus loading and
average chlorophyll concentrations. Vollenweider demonstrated
such a correlation between phosphorus loadings and chlorophyll
concentrations at the 1975 North American Project Meeting in
Minneapolis. He plotted the phosphorus loadings of a water body,
67
-------
10000
CD
oo
-------
10000
en
to
E
\
Q.
o>
E
o
z
o
<
o
<
o
o:
o
1000
100
Vollenweider
- (l975°2)oo
10
O.I
HYDRAULIC RESIDENCE TIME
T
(FROM VOLLENWEIDER,I976o)
I I I I I I I I I I I
10
HYDRAULIC LOAD, qfi ( m/yr)
100
1000
Figure 10. Vollenweider Critical Phosphorus Loading and
Hydraulic Loading Relationship.
-------
as manifested in the_pJao.sphorus loading characteristics term
(L(P)/qs) (1/(1 + vz/q )) in Equation 20, and the mean epi-
limnetic chlorophyll a_ concentration of the water body. Even
though the chlorophyll a_ concentrations consist of a mixture of
annual and summer average values, Vollenweider showed a definite
relationship (r = 0.87) between the phosphorus loading character-
istics of a water body and its average epilimnetic chlorophyll a_
concentration. Vollenweider's resulting loading diagram is pre-
sented in Figure 11. This diagram includes confidence intervals
for prediction of chlorophyll concentrations in a water body as
a function of its phosphorus loading, as modified by its hydraulic
loading. The reader is reminded that since the phosphorus load-
ing characteristic term is equivalent to the predicted mean in-
lake phosphorus concentration (Equation 20), assuming a steady
state condition, Vollenweider is, in effect, relating chlorophyll
a concentrations to total phosphorus concentrations in the same
manner as other researchers (Sakamoto, 1966; Dillon, 1974a; Jones
and Bachmann, 1976). However, Vollenweiderrs contribution was
to provide a phosphorus loading term, modified by hydraulic load-
ing, which was equivalent to the predicted in-lake phosphorus
concentration (Equation 20). Thus, Figure 11 indicates the re-
lationship between predicted in-lake phosphorus concentration,
as well as the phosphorus loading characteristics, and the mean
epilimnetic chlorophyll a concentrations in a water body. In this
manner, chlorophyll a_ concentrations can be related to phosphorus
loadings, as well as to mean phosphorus concentrations. Larsen and
Mercier (1976) used the same phosphorus loading relationship in
shifting emphasis from phosphorus loadings to influent phosphorus
concentrations. This will be considered in a later section of
this report.
It should be noted that the response of a water body to a
reduction in phosphorus loading will not be an immediate accom-
panying reduction in the chlorophyll concentration of the water
body. Rather, there will be a "lag period" during which the phos-
phorus concentrations, and hence, chlorophyll a concentrations, in
the water body are adjusting to the new phosphorus loadings. When
the water body has reached a new equilibrium condition with
respect to its phosphorus concentrations, then the loading dia-
gram (Figure 11) can validly be used to predict the expected chloro-
phyll biomass in the water body. Vollenweider (1976a) has demon-
strated this lag phenomenon with data from Lake Washington. This
concept is examined by Sonzogni et al. (1976) in their phosphorus
residence time model, and will be explored further in a later
section of this report.
Dillon Phosphorus Loading-Phosphorus Retention and Mean_Depth
Relationship
Dillon (Vollenweider and Dillon, 1974; Dillon, 1975) was one
of the first to point out one of the omissions of Vollenweider's
70
-------
100
z
o
tr
H
§ 10
z
o
o
01
OL
O
cr
3
o
p I
UJ
UJ
UJ
O
<
OL
UJ
O.I
( FROM VOLLENWEIDER, 19760 )
X
X
X / /
x / /
x
//
99%
99 %
/
11
/
-LOADING CHARACTERISTICS
WITHIN
TOLERANCE
EXCEED
TOLERANCE-
i _ i i i i i I
O.I
10
100
1000
Figure 11.
(mg/m3)
Vol 1 enwei der Phosphorus Loading Ctiaracteri sti cs
and Mean Chlorophyll a^ Relationship
-------
original phosphorus loading diagram (Figure 5). Because flushing
rate and hydraulic residence time, as well as phosphorus loading
and mean depth, play a part in determining the relative degree
of fertility of a water body, Dillon attempted to include these
parameters in a formulation of his own,
Dillon derived his model from Vollenweider ' s original phos-
phorus mass balance model, as indicated in Equation 5. The
steady state solution to Vollenweider ' s model (Equation 8) was
shown to be [P]OT = L(P)/(z/TW + z/a ) . However, as mentioned
earlier, measurement of 0p is very difficult and only indirectly
obtainable. Consequently, using the same assumptions as were
used to derive the model, Dillon (1975; Dillon and Rigler, 1974a)
derived an alternate parameter, the phosphorus retention coeffi-
cient, R(P) , which can be shown to have a functional relationship
to Vollenweider ' s phosphorus sedimentation rate coefficient, ap .
Dillon (1975; Dillon and Rigler, 1974a) has indicated that R(P1
can be approximated, assuming a steady state condition, as
R(P) = 1 - (ZqQ [P]Q / Iqi [P]i) (21)
3
where q = outflow volume (m /yr) ,
o
3
q. = inflow volume (m /yr),
3
[P] = outflow concentration (mg/m ) , and
3
[P].= inflow concentration (mg/m ).
Thus R(P) represents the fraction of the phosphorus input which
is retained in the sediments of the water body (i.e., the frac-
tion of the inflowing phosphorus which sediments annually) .
Conversely, l-R(P) is the fraction of inflowing phosphorus not
retained in the water body (i.e., it is lost by way of outflow).
Kirchner and Dillon (1975) have demonstrated that R(P) was highly
correlated with the areal water loading. Using multiple regres-
sion analysis they have produced a regression equation for predict-
ing R(P) which is very similar to the value predicted on theoret-
ical grounds (Snodgrass, 1974; Snodgrass and O'Melia, 1975). Chapra
(1975) has presented an interpretation of the high correlation
found between R(P) and the areal water loading and derived an al-
ternate method of determining R(P) as follows,
72
-------
R(P) = v/(q + v) (22)
s
u = apparent settling velocity of total phos-
phorus = a u ' ,
q = areal water load = Q/A,
o
<* - fraction of total phosphorus represented by
settleable particulate phosphorus ,
u' = settling velocity of settleable particulate
phosphorus,
Q = lake discharge volume, and
A = water body surface area.
Regardless of how it is determined, Dillon (1975; Dillon and
Rigler, 1974a; 1974b; 1975) has shown that when R(P) is calculated
and substituted into Equation 8, the equation can be rewritten as
[P] =(L(P) (l-R(P)))/z P (23)
This equation attempts to consider the effects of phosphorus
retention, as well as flushing rate and phosphorus loading, on
the degree of fertility of a water body. It should be noted that
the external loading, L(P), is in effect lost as an independent
parameter since, by definition, L(P) (l-R(P)) is that part of the
external phosphorus loading which is lost through the outlet.
Thus, L(P) (l-R(P)) can be defined as the average outflow con-
centration. Therefore, in the strictest sense, Dillon's model
cannot be used for defining loading tolerances as long as there
is no valid model available for determining R(P). Dillon
(Kirchner and Dillon, 1975) and Chapra (1975) have attempted to
derive an independent and valid model for R(P), as was mentioned
earlier. The effect of mean depth as an independent parameter
is again partially lost since pw = l/tw = Q/V = Q/(A • z), where
A - surface area of water body. Therefore, z pw = z (Q/(A • z))
= Q/A. As indicated earlier, Q/A is the areal water loading. Thus,
Equation 23 defines the steady state phosphorus concentration of
a water body as directly proportional to the product of the phos-
phorus loading and outflow phosphorus loss (i.e., "average out-
flow concentration"), and inversely proportional to the areal
73
-------
water loading. The areal water loading is equivalent to the
hydraulic loading, q (i.e., q = Q/A = Q/(V/z) = z(V/Q) =
z pw = Z/T^) . s s
Inclusion of the factor (l-R(P), therefore, accounts for one
more source of variation in determining a water body's trophic
status. Dillon (1975; Vollenweider and Dillon, 1974) prepared
a loading diagram upon which is plotted (L(P) (l-R(P) ) )/p versus z
(Figure 12). Boundary lines representing phosphorus concentra-
tions of 0.01 mg/1 and 0.02 mg/1 (Sawyer, 1947; Sakamoto, 1966;
Dillon, 1975) can be drawn on the diagram. These boundary lines
correspond to Vollenweider ' s "permissible" and "excessive" bound-
ary conditions (Figures 7 and 8). Water bodies below the 0.01
mg/1 phosphorus concentration line are considered oligotrophic and
those above the 0.02 mg/1 phosphorus concentration line are consid-
ered eutrophic. The transition zone between the 0.01 and 0.02
mg/1 phosphorus concentration lines is considered the mesotrophic
zone .
In Dillon's model, the trophic categorization of a water
body is based on measurement of the water body's phosphorus con-
centration, rather than its phosphorus loading. This line of
reasoning is consistent with the view mentioned earlier that the
nutrient concentration, rather than nutrient loading, determines
a water body's degree of eutrophicat ion .
Dillon's model has its quantitative basis in the same simple
nutrient budget model as does Vollenweider ' s model (Vollenweider,
1975a). In addition, it is a simple method for predicting phos-
phorus concentrations in water bodies . If these concentrations
can, in turn, be related to water quality parameters that re-
flect a water body's trophic condition (e.g., chlorophyll con-
centrations, productivity,- Secchi depth, etc.), then measurement
of phosphorus concentration becomes a very convenient way to
define or predict trophic status. As mentioned earlier, Dillon
(1974a; Dillon and Rigler, 1974a) and other workers (Sakamoto,
1966; Jones and Bachmann , 1976) found such a correlation between
phosphorus concentration at spring overturn and predicted
average summer chlorophyll a concentration.
Larsen and Mercier Influent Phosphorus And Phosphorus Retention
~~
Larsen and Mercier (1976) shifted emphasis from phosphorus
loadings to average influent phosphorus concentrations as a
measure of trophic state. They described the average phosphorus
concentration in a water body as a function of the relationship
between the mean influent phosphorus concentration and the water
body's ability to assimilate the influent phosphorus. Their
model, like Dillon's model, was derived from the steady state
solution of a simple phosphorus mass balance model such as
74
-------
10
en
EUTROPHIC ZONE
-------
presented by Vollenweider (Equation 8) (1975a). Recalling that
0)
= 1/T and Z/T = qs, Equation 23 can be rewritten as
= L(P) (l-R(P))
= (L(P)/q ) (l-R(P))
O
(l-R(P))
(24)
where [P] = influent phosphorus concentration (mg/m )
= L(P)/q. and
o
l-R(P) = fraction of phosphorus input not retained
by sediments.
This relationship is identical to that of Dillon (Equation 23)
since L(P)/z p^ = L(P)/qs = [P]. Thus Larsen and Mercier's
relationship relates the steady state phosphorus concentration
of a water body to the product of the influent phosphorus con-
centration and the fraction of the phosphorus input which is not
sedimented.
Larsen and Mercier's (1976) relationship (Equation 24-) be-
tween water body steady state in-lake phosphorus concentration
and phosphorus retention is identical to that relationship im-
plicitly indicated earlier in Vollenweider's equation for deter-
mining the critical phosphorus loading for a water body, based
on its mean depth and hydraulic load (Equation 19). According
to Vollenweider (1975) and Larsen and Mercier (1976), R(P) =
1/(1 + 4P )• Therefore, Equation 19 can be shown to be equiva-
lent to Equation 24 as follows:
L (P) =
c
from Equation 19
10 -q (1
s
from Equation 24
Rearranging,
10 = (L (P)/q
/z7q~))
= [P] (l-R(P))
Taking, for simplicity, Sawyer's
(1947) spring overturn critical
phosphorus concentration of 10
mg/m3 as [?]«,, and recalling
R(P) =!/(!
Since
= [P], and
' co
then
10 = [P] (i-d/a +
10 = [P]
The same results are obtained using either equation.
76
-------
Larsen and Mercier (1976) prepared a phosphorus diagram to
show the relationship between a water body's influent phosphorus
concentration and its phosphorus retention capacity, as illus-
trated in Figure 13,, Curves delineating trophic states can be
drawn on Larsen and Mercier's diagram in a manner analogous to
the method in which they have been plotted on the previous load-
ing diagrams. Thus, this diagram can be used to determine the
reduction of a water body's influent phosphorus concentration
necessary to improve its trophic condition. Since Larsen and
Mercier's diagram attempts to relate trophic state and in-lake
phosphorus concentrations, it can also be related to other para-
meters of water quality (e.g., chlorophyll concentrations, pro-
ductivity, Secchi depth, etc.). For the same values of L(P),
pw z, and R(P), the relative positions of lakes plotted on Dil-
lon's loading diagram (Figure 12) would be identical to those on
Larsen and Mercier's diagram (Figure 13) because both diagrams
estimate the same property, namely in-lake steady state phos-
phorus concentration, from the same variables.
77
-------
.-- 1000
X.
o>
O
h-
<
oi
o
z
O
o
V)
3
cr
o
x
a.
CO
O
UJ
ID
100
20
10
EUTROPHIC ZONE
(FROM LARSEN 8. MERCIER, 1976)
I I I I
'PERMISSIBLE
MESOTROPHIC
- ZONE
OLIGOTROPHIC ZONE
I
I
I
I
0.2 0.4 0.6 0.8
PHOSPHORUS RETENTION COEFFICIENT, R
1.0
Figure 13. Larsen and Mercier Influent Phosphorus and
Phosphorus Retention Relationship.
-------
SECTION VI
RESULTS OF THE INITIAL ANALYSIS OF THE US
OECD EUTROPHICATION STUDY DATA
The overall approach utilized in the US OECD eutrophication
study involved giving each of the US investigators a small amount
of funds to develop a report covering the topics listed in
Appendix I. Each investigator prepared a preliminary draft re-
port which was made available to all the other US OECD investi-
gators in the spring of 1974. During the remainder of 1974 and
early 1975 each investigator revised his report so that it con-
formed to the form outlined in Appendix I. The US EPA limited
each report to approximately 20 typewritten pages. These reports
were submitted to the US EPA on or about July 1, 1975. At that
time they were made available to the authors of this report for
examination.
This section of this report involves a detailed examination
of the information provided on sampling, analytical and other
methodology used by the US OECD investigators to generate the
summary data sheet for their respective water bodies as presented
in Appendix II. This section also examines the various methods
used by the US OECD investigators to estimate nutrient load-lake
or impoundment trophic response relationships. Particular
attention was given to the nutrient loading estimates as they
are applied in the loading diagrams developed by Vollenweider
and others for establishing critical phosphorus loadings
and trophic state associations for lakes and impoundments.
SAMPLING AND MEASUREMENT METHODOLOGIES
The US OECD water bodies were examined both for nutrient
flux and trophic response. A water body's trophic response was
measured by a variety of physical, chemical and biological par-
ameters, as outlined in the Final Report Outline (Appendix I)
and summarized in the investigators' Summary Sheets (Appendix II).
The various response parameters deemed essential or desirable in
the OECD eutrophication study (Table 2) had been agreed upon
prior to the initiation of the study. However, most of the US
OECD water bodies had been extensively studied prior to initiation
of the US OECD eutrophication study. In most cases the goals of the
79
-------
prior studies were often different from those of the US OECD
eutrophication study. Also, the sampling and analytical method-
ologies employed in the earlier studies were often different from
those suggested and outlined by the OECD Water Management Sector
Group prior to initiation of the OECD eutrophication study. A
summary of the analytical methodologies used by the US OECD inves-
tigators in determining the major response parameters is presented
in Table 11, while the sampling methodologies are presented on the
Summary Sheets (Appendix II). Examination of Table 11 indicates
that while the US EPA (US EPA, 1971; 1973d; 1974b) and Standard
Methods (APHA ejt al. , 1971) served as the major sources of analyt-
ical methodology,"There was still a wide variety of methods used
by the US OECD investigators to determine various parameters. In
addition, the sampling regimes, including sampling depths, fre-
quencies, and durations, varied widely among investigators. For
example, the "mean" value for a given parameter was biased both
by the period of sampling and the frequency with which the water
body was sampled. Some water bodies were sampled at regular in-
tervals, while others were sampled only during the ice-free period
or during a specific month of the year. Also, some water bodies
were sampled at many depths while others were sampled only at a
few depths. Any sampling and/or analytical errors were also in-
corporated into determination of the mean values . The result of
these variations is that direct comparison of values between water
bodies is often not valid. Standardization of all sampling method-
ologies and analytical procedures is necessary before such direct
comparison of trophic response parameters between US OECD water
bodies is valid.
NUTRIENT LOAD CALCULATION METHODOLOGIES
The usefulness of the various Vollenweider phosphorus load-
ing relationships, as well as the relationships developed by
Dillon (1975) and Larsen and Mercier (1976), for establishing
critical phosphorus loading rates and trophic state associations
is dependent upon the accuracy of the water body's phosphorus
loading estimates. Consequently, before reviewing the nutrient
load-trophic response relationships found in the US OECD eutrophi-
cation study, it is appropriate to review the various methods
used by the US OECD investigators to calculate the parameters nec-
essary for the various nutrient loading diagrams derived in
the previous section.
A summary of the methods used to estimate the nutrient load-
ings to the US OECD water bodies is presented in Table 12. Exami-
nation of this table indicates a variety of different methods
were employed by the US OECD investigators to estimate the nutri-
ent loadings. An attempt was made to clarify and standardize
these various methodologies. Such standardization is necessary
so that the loading estimates may be directly comparable between
water bodies in the US OECD eutrophication study. However, the
80
-------
Table lla. ANALYTICAL PROCEDURES FOR MAJOR RESPONSE PARAMETERS EXAMINED
IN US OECD EUTROPHICAT30N STUDY - PHOSPHORUS AND NITROGEN
CONCENTRATIONS11
Water Body
Blackhawk
Brownie
Calhoun
Came lot -Sherwood
Complex
Dissolved
Phosphorus
Ascorbic Acid
Method (APHA
e_t al. , 1971)
-
-
Ascorbic Acid
Method (APHA
et al. , 1971)
Total
Phosphorus
Persulfate digestion
followed by Ascorbic
Acid Method (APHA
et al. , 1971)
-
-
Persulfate digestion
followed by Ascorbic
Acid Method (APHA
Ammonia Nitrate
Phenate Method
(APHA et al. ,
1971)
-
-
Phenate Method
(APHA et al. ,
1971)
Nitrite
-
-
-
"
Canadarago
Cayuga
Cedar
Dogfish
Murphy and Riley
Method (1962)
Not determined
Concentrated Sulfuric
Acid S Potassium Per-
sulfate digestion,
followed by Murphy 6
Riley Method (1962)
Potassium Persulfate
digestion, followed
by Phosphomolybdate/
Stannous Chloride
Reduction (APHA
et al., 1971)
Direct Nessleri-
zation (APHA et_
al. , 1971)
APHA et al.
(19711
Mullin and Riley AutoAnalyzer
Procedure (1955) or APHA et
if < 30 ug/1; al.(19717~
AutoAnalyzer
if > 30 ug/1
Cadmium Reduc-
tion Method
(APHA et al_. ,
1971)
APHA et al.
(197lT~
-------
Table lla (continued). ANALYTICAL PROCEDURES FOR MAJOR RESPONSE PARAMETERS
EXAMINED IN US OECD EUTFOPHICATION STUDY - PHOSPHORUS AND NITROGEN
CONCENTRATIONS3 '
Water Body
Dutch Hollow
Dissolved
Phosphorus
Ascorbic Acid
Method (APHA
et a^. , 1971)
Total
Phosphorus
Persulfate digestion,
followed by Ascorbic
Acid Method (APHA
et 'al. , 1971)
Ammonia Nitrate
Phenate Method
(APHA et al. ,
1971)
Nitrite
-
oo
r-o
George
Harriet
Isles
Kerr Reservoir
Lamb
Automated Phos-
phomolybdate/
Stannous Chlo-
ride Reduction
(APHA et^ al. ,
1971X Ascorbic
Acid Reduction
Method used af-
ter July, 1975
(APHA et_ aJL. ,
1971)
Not determined
Potassium PersulfateS Automated Pheno- Automated Hydrazine Reduction
Sulfuric Acid diges-
tion, followed by
Ascorbic Acid reduc-
tion Method (APHA
et al., 1971)
late Method with
Technicon Auto-
Analyzer I (US
EPA, 1971)
with Technicon AutoAnalyzer I
(US EPA, 1971) from 1966-
1975; Cu/Cd Reduction (US
EPA,1974b) after July, 1975
Potassium Persulfate
digestion, followed
by Phosphomolybdate/
Stannous Chloride
Reduction (APHA
et al., 1971)
APHA et aJU
(1971F"
Cadmium Reduc-
tion Method
(APHA et_ al.
1971)
APHA et al.
(1971"5
-------
Table lla (continued). ANALYTICAL PROCEDURES FOR MAJOR RESPONSE PARAMETERS
EXAMINED IN US OECD EUTROPHICATION STUDY - PHOSPHORUS AND NITROGEN
CONCENTRATIONSa
Dissolved Total
Water Body Phosphorus Phosphorus
Meander Not determined Potassium Persulfate
digestion, followed
by Phosphomolybdate/
Stannous Chloride
Reduction (APHA
et al. , 1971)
Mendota Analytical procedures outlined
Michigan Analytical procedures outlined
00
MinT~lf^1~OnK^ PVir-itrriV-n-imnTwHH^-l-tj/ P/^v^c-iilfja-f-cs Hirrdo-f-T^T-i
Ammonia
APHA et al.
(1971F"
in Lee (1966)
in Rousar (1973)
Mnf dp tprrrn npd
Nitrate Nitrite
Cadmium Reduc- APHA et al .
tion Method (197lT~
APHA et al .
1971)
Not determined Not deter-
Potomac Estuary
Redstone
Sallie
Sammamish
Phosph
Ascorbic Acid
Reduction (APHA
e_t a_l. , 1971 )
US EPA 91971)
Ascorbic Acid
Method (APHA
et al. , 1971)
followed by Phospho-
molybdate/Ascorbic Acid
Reduction (APHA et_ al. ,
1971)
US EPA (1971)
Persulfate digestion,
followed by Ascorbic
Acid Method (APHA
et al., 1971)
US EPA (1971)
Phenate Method
(APHA et aJ.,
1971)
US EPA (1971)
mined
US EPA 0971)
"As outlined in APHA et aJU , 1971"
Molybdate Complexing Reaction
(Strickland and Parsons, 1968)
Cadmium-Copper
Column (Strick-
land and Par-
sons , 1968)
-------
Table lla (continued). ANALYTICAL PROCEDURES FOR MAJOR RESPONSE PARAMETERS
EXAMINED IN US OECD EUTROPHICATION STUDY - PHOSPHORUS AND NITROGEN
CONCENTRATIONS3
Water Body
Dissolved
Phosphorus
Total
Phosphorus
Ammonia
Nitrate
Nitrite
cx>
-P
Shagawa
Stewart
Tahoe
East Twin
West Twin
Twin Valley
Murphy-Riley As- Persulfate digestion,
corbie Acid Meth- followed by Murphy-
od (US EPA, 1971) Riley Ascorbic Acid
Method (US EPA, 1971)
Ascorbic Acid
Method (APHA
et al. , 1971)
Persulfate digestion,
followed by Ascorbic
Acid Method (APHA
et al. , 1971)
Phosphomolybdate/ Persulfate Sulfuric
Ascorbic Acid
Reduction (APHA
et al., 1971)
Acid digestion,
followed by Phos-
phomolybdate /Ascorbic
Acid Reduction (APHA
et al. , 1971)
Phosphomolybdate/ Persulfate Sulfuric
Ascorbic Acid
Reduction (APHA
et al. , 1971)
Ascorbic Acid
Method (APHA
et al. , 1971)
Acid digestion,
followed by Phos-
phomolybdate /As corbie
Acid Reduction (APHA
et al_. , 1971)
Persulfate digestion,
followed by Ascorbic
Acid Method (APHA
et al. , 1971)
Automated Indo- Automated Cadmium Reduction
phenol Blue Meth- followed by Diazotization
od (US EPA, 1971) (US EPA, 1971)
Phenate Method
(APHA et al.,
1971)
Direct Nessleri- Cadmium Reduc-
zation (APHA et^ tion (APHA et
al. , 1971) aJL. , 1971)
Direct Nessleri-
zation (APHA et
al. , 1971)
Phenate Method
(APHA et al.,
1971)
Cadmium Reduc-
tion (APHA et_
al. , 1971)
-------
Table ]la (continued). ANALYTICAL PROCEDURES FOR MAJOR RESPONSE PARAMETERS
EXAMINED IN US OECD EUTROPHICATION STUDY - PHOSPHORUS AND NITROGEN
CONCENTRATIONS3
Water Body
Dissolved
Phosphorus
Total
Phosphorus
Ammonia
Nitrate
Nitrite
oo
en
Virginia
Waldo
Washington
Weir
Wingra
Ascorbic Acid
Method (APHA
et al., 1971)
US EPA (1973d)
Persulfate digestion,
followed by Ascorbic
Acid Method (APHA
ejt al. , 1971)
US EPA (1973d )
Phenate Method
(APHA et al.,
1971)
US EPA (1973d) US EPA (1973d) US EPA (1973d)
(Note: Many different methods have been used over the years by different
investigators. The methods reported here are those of more recent years'
studies (Edmondson, 1975b))
Phosphomolybdate/ Perchloric Acid diges- Direct Nessleri- "Strychnidine
Stannous Chloride tion, followed by zation (APHA et Method until
Reduction (APHA Phosphomolybdate/ al., 1971)
e_t^ al_. , 1971) Stannous Chloride
Reduction (APHA
ejt aJU , 1971)
August, 1967,
then Brucine
Method (APHA
et al. , 1971)
US EPA (1971)
Murphy and Riley
Method (1962)
US EPA (1971)
Persulfate digestion;
followed by Murphy
and Riley Method
(1962)
Automated Al-
kaline Phenol
Procedure (US
EPA, 1971)
Alkaline phenol
procedure
adopted for
AutoAnalyzer
Automated Hydra- Not deter-
zine Reduction mined
Procedure,
Henrikaen (1965)
Initially Hydra- Not deter-
zine Reduction mined
Procedure. Later
the Brucine Method
of Kahn 6 Brezenski
(1967)
aAs indicated by the US OECD investigators.
Dash (-) indicates no data available.
-------
Table lib. ANALYTICAL PROCEDURES FOR MAJOR RESPONSE PARAMETERS EXAMINED IN
US OECD EUTROPHICATION STUDY - TRANSPARENCY, PRIMARY PRODUCTIVITY
AND CHLOROPHYLL a AND DISSOLVED OXYGEN CONCENTRATIONS3
Water Body
Water
Transparency
Dissolved
Oxygen
Chlorophyll a
Primary
Produc civity
Blackhawk
Secchi disc
co
en
Brownie
Calhoun
Camelot-Sherwood Secchi disc
Complex
Canadarago 30 cm white
Secchi disc
Cayuga
Cedar
Dogfish Secchi disc
YSI Model 54 D.O.
Meter
YSI Model 54 D.O.
Meter
Weston and Stack D.O.
Meter; some surveys
made using Winkler
Method with Azide
Modification (APHA
et al., 1971)
Dutch Hollow
Secchi disc
YSI Model 54 D.O.
Meter
Strickland and Parsons
(1965)
Strickland and Parsons
(1965)
Strickland and Parsons
(1965) See Hetling et_
al. (1975) for varia-
tions between 1968 and
subsequent determina-
tions
Strickland and Parsons
(1968) until May, 1972;
Turner Fluorometer after
May, 1972
Strickland and Parsons
(1965)
Not determined
Not determined
Method developed
by principal in-
vestigators (see
Hetling et a^.,
1975 for~details)
Not determined
Not determined
Not determined
Not determined
-------
Table lib (continued). ANALYTICAL PROCEDURES FOR MAJOR RESPONSE PARAMETERS
EXAMINED IN US OECD EUTROPHICATION STUDY - TRANSPARENCY, PRIMARY
PRODUCTIVITY AND CHLOROPHYLL a AND DISSOLVED OXYGEN CONCENTRATIONS'5
Water Body
Water
Transparency
Dissolved
Oxygen
Chlorophyll a
Primary
Productivity
George
Harriet
Isles
Kerr Reservoir
Lamb
Meander
Mendota
Michigan
Minnetonka
Not determined
8 inch diameter
White Secchi
disc
Secchi disc
Secchi disc
Hydrolab Surveyor £
Azide Modification
of Winkler Method
Turner Fluorometer
Strickland and Parsons
(1968) until May, 1972;
Turner Fluorometer after
May, 1972
Strickland and Parsons
(1968) until May, 1972;
Turner Fluorometer after
May, 1972
Analytical procedures outlined in Lee (1966)
Analytical procedures outlined in Rousar (1973)
Secchi disc and
attenuation
coefficients
Strickland and Parsons
(1968)
1 14
C uptake
(Steeman-Nielsen,
1952)
Not determined
Not determined
Oxygen Production
under standard
laboratory con-
ditions (i.e. ,
24°C, 400 foot
candles)
Not determined
Not determined
Not determined
Not determined
-------
Table lib (continued). ANALYTICAL PROCEDURES FOR MAJOR RESPONSE PARAMETERS
EXAMINED IN US OECD EUTROPHICATION STUDY - TRANSPARENCY, PRIMARY
PRODUCTIVITY AND CHLOROPHYLL a AND DISSOLVED OXYGEN CONCENTRATIONS3
Water Body
Potomac
Estuary
Redstone
Sallie
Sammamish
Shagawa
CO
CO
Water Dissolved
Transparency Oxygen
Secchi disc Winkler Method; Azide
Modification (APHA et al
Secchi disc YSI Model 54 D.O.
Meter
"As outlined in APHA et al . , 1971"
Secchi disc Winkler Method; Azide
Modification (APHA
et al. , 1971)
Secchi disc Winkler Method; Azide
Modification (EPA,
1971)
Chlorophyll a
90% Acetone extraction
., 1971)
Strickland and Parsons
(1965)
90% Acetone extraction
(Strickland and Parsons,
1968)
90% Acetone extraction
(UNESCO, 1966)
Primary
Productivity
Not determined
Not determined
Not determined
14
C uptake
(Strickland and
Parsons, 1968)
Oxygen production;
light and dark
bottle procedure
Stewart
Tahoe
East Twin
West Twin
Secchi disc
20 cm dia.
Secchi disc;
alternating
black g white
quadrants
•20 cm dia.
Secchi disc ;
alternating
black £ white
quadrants
YSI Model 54 D.O.
Meter
Strickland and Parsons
(1965)
Strickland and Parsons
(1968), with trichromatic
equations (APHA et al.,
1971)
Strickland and Parsons
(1968), with trichromatic
equations (APHA et_ al . ,
1971)
Not determined
pH method in light
and dark bottles
after 4 hours of
incubation
pH method in light
and dark bottles
after 4 hours of
incubation
-------
Jit' (continued). ANALYTICAL PROCEDURES FOR MAJOR RESPONSE PARAMETERS
EXAMINED IN US OECD EUTROPH1CAT TON STUDY - TRANSPARENCY, PRIMARY
PRODUCTIVITY AND CHLOROPHYLL a AND DISSOLVED OXYGEN CONCENTRATIONS'3
CO
CD
Water Body
Twin Valley
Virginia
Waldo
Washington
Water
Transparency
Secchi disc
Secchi disc
20 cm white
Secchi disc
(Note : Many
Dissolved
Oxygen
YSI Model 5U D.O.
Meter
YST Model 5't D.O.
Meter
-
different methods have
Chlorophyll a
Strickland and Parsons
(1965)
Strickland and Parsons
(1965)
"Strickland and Parsons
been used over the years by-
Primary
Productivity
Not determined
Not determined
" C uptake
different
investigators. The methods reported here are those of more recent years'
studies (Edmondson, 1975b).
Secchi disc - Strickland and Parsons
(1968) Prior to 1968,
used acetone extraction
and Klett colorimeter
Oxygen production
in light and dark
bottles.14C uptake
done for several
years
Weir
Wingra
Secchi disc
Secchi disc YSI D.O. Meter
Trichromatic Method
(US EPA, 1973d )
Not determined
14C uptake (APHA
et aJL. , 1971)
See Huff et al .
(1972)
As indicated by the US OECD investigators.
Dash (-) indicates no data available.
-------
Table 32. SUMMARY Of METHODS UCFD TO CALCULATE
NUTRIENT LOADINGS TOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator1 in Mutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Blackhawk, Camelot-
Sherwood, Cox Hollow,
Dutch Hollow, Redstone,
Stewart, Twin Valley
and Virginia
A) Phosphorus Loading:
1) Base Flow
7) Woodland
3) Rural Runoff
U) Urban Runoff
5) Manured Lands
6) Precipitation
7) Dry Fallout
8) Domestic Wastewaters
9) Septic Tanks
10) Drained Marshes
11) Groundwater
•Phosphorus loadings estimated
from watershed land usage
phosphorus export coefficients
derived for the Lake Mendota
(Wisconsin) watershed and
presented in Sonzogni and
Lee (1974).
CD
O
B) Nitrogen Loading:
-Same sources and methods as
for phosphorus loadings.
Watershed nitrogen export co-
efficients were used to cal-
culate the nitrogen loadings.
Brownie, Calhoun,
Cedar, Harriet and
Isles
A) Phosphorus Loading:
1) Waste Discharges
(includes city water
and air conditioning
water)
2) Land Runoff (via storm
drain and direct)
3) Estimated Precipitation
4) Estimated Groundwater
Input
B) Nitrogen Loading:
-No information available.
-Not Determined.
-------
Table 12(continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Canadarago
A) Phosphorus Loading:
T~5 Wastewater Discharges
2) Septic Tanks
3) Gaged Tributaries
-Estimates were made by direct
measurement of the primary
wastewater treatment plant to
Ocquionos Creek (one of maior
tributaries to lake), and the
difference between upstream and
and downstream samples from
Ocquionos Creek, and calculations
from published per capita contri-
butions .
- Estimate made by calculations
involving total population of
lakeside residences, lakeside
residence population having
septic tank failures, average
residence time of lakeshore
facilities and per capita phos-
phorus input value of 2.9 g
P/capita/day. It was assumed
any phosphorus entering a septic
tank leaching field was re-
tained in the field, unless the
tank discharged directly into the
lake.
-Estimated as product of measured
daily flows and phosphorus con-
centrations .
-------
Table 12 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Canadarago
(continued)
4) Non-gaged Tribu-
taries
5) Rainfall and Dry
Fallout
6) Groundwater
B) Nitrogen Loading:
Cayuga
A) Phosphorus Loading:
1) Waste Discharge
-Assumed runoff for non-gaged
area was equal to the average
of the area drained by the
gaged tributaries, not count-
ing the wastewater treatment
plant effluents.
-Estimated from literature
values; mainly Weibel (1969).
-Considered negligible.
-Same sources and methods as
for phosphorus loadings. For
the septic tank nitrogen load-
ings, 10.3 g N/capita/day
was used in the calculations.
It was assumed that no nitro-
gen was retained in the septic
tank leaching fields; there-
fore, it was assumed the entire
lakeshore population with
septic tanks contributed nitro-
gen to the lake. Nitrogen fix-
ation was not considered in the
nitrogen loading estimates.
-Determined using estimates of
per capita discharge of phos-
phorus to tributaries and
phosphorus in waste discharged
directly to lake.
-------
Table I? (continued). SUMMARY Of METHODS USED TO CALCULATE
NUTPIENT LOADINGS EOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Cayuga
(continued)
2) Land Runoff
3) Precipitation
t) Groundwater
-Estimated per capita discharge
of phosphorus to tributaries minus
phosphorus in waste discharged
directly to lake.
-Phosphorus in precipitation
monitored in one year study.
-Information not available.
to
CO
NOTE: 1) Total phosphorus input and molybdate reactive
(unfiItered) phosphorus input taken from Likens
(1972b; 1974a; 1974b).
2) Phosphorus in precipitation and in 25 tribu-
taries (draining 78% of watershed) was moni-
tored in a one year study.
3) "Biologically reactive phosphorus" determined
using nutrient export coefficients; forest =_
8.3 mg/m /yr; agricultural/rural = 13.2 mg/m /yr;
urban = 100 mg/m /yr.
B) Nitrogen Loading:
-Same general methods as for
phosphorus loadings.
-t.U4 kg N/yr used as per capita
N discharge. (Olsson, Kargren and
Tullander, 1968) .
-Sewage treatment efficiency (all
types of disposal systems) of 50
percent for N removal was assumed.
-------
Table 1 2 (con tinned). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OCCF) WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Dogfish, Lamb and
Meander
CO
-p
George
A) Phosphorus Loadings :
1) Atmosphere
(wet and dry)
2) SurFace Flow
(sheet flow +
Flow through
soils)
3) Tributary Flow
4) Groundwater
-Determined by measurement of
samples of water collectors
placed throughout drainage
basin. Snow samples also
analyzed.
-Measured at two-week inter-
vals during April-October.
-Measured at two-week inter-
vals during April-October.
Tributaries monitored by
grab sample, and flows de-
termined manually on day of
sampling.
-Assumed zero.
Details of 1972 nutrient budgets available in
Wright (1974) and Bradbury e_t_ al. (1974)
B) Nitrogen Loading:
A) Phosphorus Loading:
1) Runoff
2) Precipitation
3) Sewage Plant Effluents
4) Septic Tank Effluents
5) Lawn Fertilizer
-Not determined.
-Taken from Gibble (1974).
(Precipitation based on "normal
precipitation of basin").
B) Nitrogen Loading:
-Not Determined
-------
Table 12 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Kerr Reservoir
A) Phosphorus Loading:
1) Point Sources
CD
en
2) Gaged Tributary
Sources
3) Non-gaged Tributary
Sources
U) Rainfall
-Virginia data assembled from
tabulation prepared by Hayes,
Seay and Mattern for the
Roanoke River Basin Study and
provided by the Wilmington
District, US Army Corps of
Engineers. North Carolina
data is from Division of En-
vironmental Management, De-
partment of Economic and
Natural Resources.
-Information not available.
-Equal to total discharge minus
gaged stream discharge. Phos-
phorus and nitrogen concentration
estimates from five non-polluted
feeder streams were applied to
the volume to obtain input from
non-gaged sources.
-Taken from nutrient coefficient
data of Uttormark et al., (1974)
and Gambell and Fisher (1966).
Also, total phosphorus was deter-
mined on rainfall samples collect-
ed at Chapel Hill, North Carolina
on April 13 and April 25, 1972.
5) Groundwater Seepage
-Considered insignificant.
-------
Table 12 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Kerr Reservoir
(continued)
Hendota
to
CD
Michigan
Open Waters
B) Nitrogen Loading:
A) Phosphorus Loading:
1) Wastewater Discharges
2) Urban Runoff
3) Rural Runoff
4) Precipitation
5) Dry Fallout
6) Groundwater Seepage
7) Base Flow
8) Marsh Drainage
B) Nitrogen Loading:
A) Phosphorus Loading:
-Same sources and methods
as for phosphorus loadings.
In addition, dry fallout and
nitrogen fixation loadings
considered insignificant.
All nutrient loading data
taken from Sonzogni and
Lee (1974).
-Same sources and methods as
for phosphorus loadings. In
addition, nitrogen fixation
was included in the nitrogen
loading estimate.
-1971 phosphorus loadings were
taken from Lee (1974a)
and included phosphorus loadings
from:
]) direct wastewater,
2) indirect wastewater,
3) erosion and other diffuse
sources,
4) combined sewer overflow, and
5) precipitation and dry fall-
out onto lake surface.
-------
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Michigan
(Open Waters)
(cont inued)
-1974 phosphorus loadings were
taken from Lee (197Ua).
to
-J
Michigan
Nearshore Waters
Offshore Waters
Lower La. •* Minnetonka
B) Nitrogen Loading
--Nutrient Loadings Not Determined
--Information Not Available
A) Phosphorus Loading:
1) Sewage Effluents
2) Tributary Streams
3) Overland Runoff
4) Rainfall on Lake
5) Septic Tank Drainage
-Taken from Bartsch (1968)
-All nutrient loading data taken
from compilations made by
Harza Engineering Company ("A
Program Eor Preserving The
Quality Of Lake Minnetonka").
State of Minnesota Pollution
Control Agency, Minneapolis,
Minnesota. 1971. (Megard, 1975).
-Overland runoff was estimated
as 130 Ibs/mi /yr for2rural
runoff and 510 Ibs/mi /yr for
urban runoff.
-Phosphorus concentration in .
rainfall assumed to be 20 mg/m .
B) Nitrogen Loading:
-Not Determined.
-------
Table J2 (continued). SUMMARY OF I'L'TIIODG USED TO CALCULATE;
NUTRTFNT LOADINGS FOR US OFCD WATFR BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to V/ater Body
Potomac Estuary
CJD
oo
Sallie
A) Phosphorus Loading:
1) Upper Basin Runoff
(Note: Upper basin
runoff includes both
land runoff and waste-
water discharges in
upper basin)
2) Estuarine Wastewater
Discharges
3) Precipitation
U) Groundwater
B) Nitrogen Loading:
A) Phosphorus Loading:
1) Waste Discharge
-Based on two years of weekly
sampling of upper basin
runoff.
-Based on two years of weekly
samplings of point sources.
-Considered insignificant. Dry
fallout not considered in
phosphorus loading estimate.
-Same sources and methods as
for phosphorus loadings. Ni-
trogen fixation and dry fall-
out not considered in nitrogen
loading estimate.
-Waste discharged from City of
Detroit Lakes into Pelican
River which discharges into
lake. Concentrations of phos-
phorus in ditch to river was
monitored and converted to
weight.
-------
Table 12 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Sallie
(continued)
co
CO
Sammamish
2) Land Runoff
3) Precipitation
4) Groundwater
B) Nitrogen Loading:
A) Phosphorus Loading:
1) Waste Discharge
2) Land Runoff
-Estimated as total in Pelican
River minus waste load total
in other surface inlets.
-Phosphorus concentration in pre-
cipitation was monitored and
converted to weight as product
of lake area and total precipi-
tation .
-Collected with investigator-
designed sampler as it entered
lake. Phosphorus weight was
calculated for discharge in-
crease over surface inflow.
-Same sources and methods for
phosphorus loadings.
-Several independent methods.
-Equal to total phosphorus load-
ing plus precipitation phosphorus
loading.
-Total phosphorus loading equal
to sum of measurement of 13
streams and pipes entering lake
plus waste contributions by
several independent methods.
-------
Table 12 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Sammamish
(continued)
3) Precipitation
U) Groundwater
B) Nitrogen Loading:
o
o
Shagawa
A) Phosphorus Loading:
1) Waste Discharges
-Atmospheric phosphorus input
to lake surface determined
from limited rainwater analysis
during 1971 water year.
-Determined as insignificant
because water balance was
explainable from consideration
of surface inputs and outputs.
-Same sources and methods for
phosphorus. In addition, dry
fallout nitrogen input was not
considered in nutrient loading
estimate. Nitrogen fixation
was considered insignificant.
-In 1971 and earlier years, waste
discharges determined from single
daily grab samples and some four
and six hour-nonweighted composites
obtained. In 1972, waste dis-
charges computed phosphorus con-
centrations in the wastewater ob-
tained from 24 hour flow-weighted
composite samples. Loadings were
the product of composite concen-
trations and the total daily flows.
-------
Table 1? (continues!) . SUMMARY OF" METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BOD FES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Shagawa
(continued)
?) Land Runoff
Tribu taries
3) Precipitation
Other (= direct
runoff + excess
drinking water)
B) Nitrogen Loading:
-Weekly, nonflow-weighted phos-
phorus concentrations were in-
tegrated to obtain daily values
for creeks. Daily loads were
product of concentration and
daily flow. Prior to 1972, month-
ly loading was product of monthly
mean phosphorus concentration and
total stream flow for month. Non-
gaged tributaries estimated as
ratio of non-gaged to gaged area,
and multiplying the loading by the
factor.
-Estimated using average phospho-
rusconcentration collected at Ely,
Minnesota, and multiplying by the
monthly precipitation falling on
the lake.
-An average load/unit area/month
was calculated based on the load/
unit area/month for the gaged
basins.
-Same sources and methods as for
phosphorus loadings. Nitrogen
inputs from wastewater treat-
ment plants were calculated in
a manner similar to that used
to determine the phosphorus loadings.
-------
Table ]2 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS EOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading "to Water Body
Tahoe
A) Phosphorus Loading:
NOTE: According to state and federal regulations
no wastewater is supposed to be discharged
within the drainage basin.
1)
Land Runoff
(1969 data)
o
rv>
2) Precipitation
-Total monthly discharge of
nine major tributaries cal-
culated from daily USGS
flow measurements. Total
monthly discharge of other
54 creeks and tributaries esti-
mated as in McGauhey et al.(1963).
Phosphorus concentration data col-
lected on nine major tributaries
by the Tahoe Research Group of
the Univ. of California at Davis,
the California-Nevada Federal
Joint Water Quality Investigation,
Lake Tahoe Area Council and the
Water Resources Information Series
of the State of Nevada. Total
phosphorus mass calculated as
product of total flow and mean
concentration.
-Only traces of phosphorus were
assumed to be present in rain-
fall.
-------
Table 12 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Tahoe
(continued)
Twin Lakes
o
CO
3) Groundwater
B) Nitrogen Loading:
A) Phosphorus Loading:
1) Waste Discharges
2) Land Runoff
("sheet" runoff)
3) Precipitation
-Assumed insignificant input.
-The same sources and methods
as for phosphorus loading.
In+addition, the average
NHl(-N and NO^-N were measured
in the precipitation to esti-
mate the total nitrogen input
from rainfall.
-Assumed zero.
-Computed from lake level in-
creases, as recorded by limno-
graphs, in excess of that
from direct precipitation and
stream inflows.
-Measured with a recording
Leupold-Stevens type Q6
weighing bucket located at West
Twin Lake. Rain and snow sam-
ples (which included dry fall-
out) were collected at Kent
State University, Kent, Ohio,
for nutrient analysis.
-------
Table 12 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
Twin Lakes
(continued)
4) Groundwater
H
CD
-P
5) Surface Streams
Waldo
B) Nitrogen Loading:
A) Phosphorus Loading:
NOTE: Dry fallout was not
considered in phos-
phorus loading esti-
mate. Marsh drain-
age considered in-
significant .
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
-Twenty-eight shallow wells were
installed around lake perimeter
and a flow net constructed.
Specific discharge determined
from hydraulic gradient and field
measurement of permeability.
Wells were sampled monthly for
nutrient content.
-Measured daily or continuously
depending on station, mainly
with either 90° V notch weir
and stilling well or bucket or
culvert discharge and current
meter. Dollar Lake Stream
Station was measured daily
with either culvert discharge
and bucket or 60 or 90 V
notch weir and stilling basin
or well.
-Same sources and methods as for
phosphorus loadings. Nitrogen
fixation was not included in
the nitrogen loading estimates.
-Estimated using four indirect
methods as follows:
1) Using information from Vollen-
weider (197Sa) assume phosphorus
loading = three times measured lake
concentration = three times mean
outflow concentration;
-------
Table!? (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR UG OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Waldo
(continued)
o
01
2) Using watershed phosphorus
export coefficients derived for
undisturbed forest land in Upper
Klamath Lake, Oregon (Miller,
unpublished data in Powers et al.,
1975).
3) Using average precipitation
data for the lake and snow
analyses of Malueg ejt al. (197?)
and assuming
a) all precipitation into
watershed eventually enters
lake, or
b) only the precipitation equal to
measured outflow plus estimated
evaporation actually enters
lake; and
U) Using total phosphorus soil
export factors of Vollenweider and
Dillon (1974), and assuming remainder
of loading is direct precipitation
onto the lake surface. The mean of
the four estimated values was reported
as the annual phosphorus loading.
B) Nitrogen Loading:
(NOTE: Dry fallout was not
considered in nitro-
gen loading estimate;
marsh drainage and
nitrogen fixation con-
sidered insignificant)
Estimated using methods 2, 3a
and 3b above. (Method 1 not used
because estimates of nitrogen
retention in lake unknown. Method
4 not used because of lack of in-
formation on soil loading of
nitrogen to lake).
-------
Table 12 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Nutrient Sources Considered by General Methodology Indicated by
US OECD Investigator in Nutrient Investigator to Determine the
Water Body Loading Estimates Nutrient Loading to Water Body
Washington A) Phosphorus Loading:
(NOTE: Several sampling regimes and analytical
methodologies were used by different
investigators over the years, making a
concise summary difficult)
1957 -All sewage plants and many tribu-
taries to the lake sampled twice
per week by the Seattle Engineer-
ing Department. Nutrient concen-
trations, including total phos-
phorus, phosphate and particulate
phosphorus were determined using
methods listed in APHA ejt al.
(1971), and earlier editions.
-METRO analyzed fewer tributaries
(10) for fewer parameters (i.e.,
total phosphorus, Kjeldahl nitro-
gen and nitrate plus nitrite nitro-
i gen) approximately weekly.
-The two major inlets and one minor
inlet sampled biweekly by the US
OECD investigator for total phos-
phorus and phosphate (in 1957,
these two major inlets supplied
86% of total phosphorus loading.
The total phosphorus loading is
approximated by proportion).
-------
Table 12 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Washington
(continued)
Two sources of water flow data were used. The major source
was gage data published by USGS. In 1957, the USGS was
gaging the two major inlets + two smaller inlets. The rest
of the tributaries were determined by proportion with the
watershed area. A hydrological model was developed later for METRO
and used until 1972 to estimate the Sammamish input. Since
1972, a regression equation that relates total Sammamish flow to
stations that are gaged in the watershed has been used to determine
the water flow.
B) Nitrogen Loading:
o
Weir
A) Phosphorus Loading:
1) Rainfall
-Same sources and methods as
for phosphorus loading. In 1957,
the Seattle Engineering Depart-
ment analyzed the input water
for "several nitrogen components".
In 1964, METRO analyzed the samples
for Kjeldahl nitrogen and nitrate plus
nitrate nitrogen. In 1970's the
US OECD investigator has been ana-
lyzing for nitrate, nitrite,
ammonia and Kjeldahl nitrogen.
The sources of flow data are the
same as for the phosphorus loading.
-Taken from Brezonik et al. (1969)
for rainfall at GainesvTTle, 60
miles north of lake.
-------
Table 12 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Weir
(continued)
2) Urban
3) Pasture
4) Forest
o
CO
5) Agriculture
-Urban; runoff values taken from
Weibel (1969) and represents
averages for residential-light
commercial areas found in study
area.
-Pasture and forest runoff values
taken from Uttormark ejt aJL. (1974).
In order to account for low nutrient
binding capacity of sandy acid soils
in study area, the "average" and
"high" areal yield rates of Uttor-
mark et al. (1974) were averaged
for these two land-use classifica-
tions .
-Taken from estimates of Brezonik
and Shannon (1971) based on the
average fertilizer composition and
application rate to citrus groves.
6) Septic Tank
-Estimated using methods of Brezonik
and Shannon (1971) .
Average septic tank daily effluent
flow of 475 1 , with total phos-
phorus concentration of 8 mg/1, was
assumed. For lakeshore houses, it
was assumed 10 percent of the phos-
phorus was transported to the lake.
For non-lakeshore houses, it was
assumed one percent of the phos-
phorus was transported to the lake.
-------
Table 12 (continued). SUMMARY 0! METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Weir
(continued)
7) Wetlands
B) Nitrogen Loading:
Wingra
A) Phosphorus Loading:
1) Precipitation
2) Dry Fallout
3) Springflow
-Net phosphorus contribution
assumed zero.
-Same sources and methods as above.
For the septic tank nitrogen
loadings, a total nitrogen concen-
tration in the septic tank effluent
of 35 mg/1 was assumed (Brezonik
and Shannon, 1971).
It was assumed 25 percent of the
lakeshore homes nitrogen loading and
10 percent of the non-lakeshore homes
nitrogen loading were transported
to the lake.
-Rain and snow were collected in
open bucket type containers which
were put out when precipitation
seemed imminent.
-Estimated by exposing container to
atmosphere for several days.
During winter, bulk precipitation
was measured rather than dry fall-
out .
-Monitored continuously by USGS
where possible. Samples collected
every two weeks for phosphorus
determinations.
-------
Table 12 (continued). SUMMARY OF METHODS USED TO CALCULATE
NUTRIENT LOADINGS FOR US OECD WATER BODIES
Water Body
Nutrient Sources Considered by
US OECD Investigator in Nutrient
Loading Estimates
General Methodology Indicated by
Investigator to Determine the
Nutrient Loading to Water Body
Wingra
(continued)
4) Urban Runoff
5) Groundwater
6) Marsh
B) Nitrogen Loading:
-Determined by measurements taken
from the Manitou Way Basin,
especially during storm periods
(Kluesener, 1972).
-Considered insignificant
(Kluesener, 1972).
-Assumed marsh input loads roughly
equal to marsh output loads.
Therefore, marsh net phosphorus
contribution is zero.
-Same sources and methods as for
phosphorus loadings.
-------
results are far from complete. While all investigators reported
the nutrient sources they considered in their nutrient budget
estimates, in some instances sufficient detail was not given as
to exactly how the nutrient loadings were estimated. For example,
if watershed land use nutrient export coefficients were used,
what was the distribution of land use types in the watershed?
How was the percentage of different watershed land use types cal-
culated? How were the export coefficients calculated or estimat-
ed? If nutrient inputs were measured directly, what analytical
methods were used? What nutrients were measured? What was the
sampling frequency? How were the tributaries sampled? How
many of the tributaries were sampled? What percent of the tribu-
tary area was sampled? These are major questions that must be
answered before the usefulness of US OECD eutrophication study
data, as applied in the Vollenweider phosphorus loading diagrams
and other loading diagrams, can be fully determined.
The major nutrient input sources, according to most US
OECD investigators, were wastewater discharges, land runoff and
precipitation. Most US OECD investigators also considered
groundwater inputs in their nutrient budget calculations, although
these inputs were generally considered insignificant nutrient
sources. A summary of the various nutrient sources considered
in the nutrient loading calculations, as indicated by the US OECD
investigators, is presented in Table 13.
METHODS FOR EVALUATION OF ESTIMATES OF US OECD WATER BODY NUTRIENT
LOADINGS
Suffiently detailed information concerning the methodology
used in estimating the nutrient budgets for the US OECD eutro-
phication study water bodies was not available in most cases.
As a result, several independent methods were employed by these
reviewers in an attempt to check the reasonableness of the nutri-
ent loadings reported by the US OECD investigators. These methods
include the use of several relationships developed by Vollen-
weider (which relate phosphorus loadings to mean water body phos-
phorus concentrations) and the use of watershed nutrient export
coefficients and land usage patterns within the watershed of a
water body to predict phosphorus and nitrogen loadings. These
methods were not developed as an absolute guide for evaluating
the accuracy of the US OECD investigators' nutrient loadings, but
rather are meant to serve as a basis for checking on the reason-
ableness of these loadings, with the goal of detecting any pos-
sible major errors or unusual water body situations. An identifi-
cation key for the US OECD water bodies is presented in Table 14.
This key will be used in all subsequent figures to identify the
US OECD water bodies.
Ill
-------
Table 13 SUMMARY OF NUTRIENT SOURCES CONSIDERED
IN US OECD WATER BODY NUTRIENT LOADING ESTIMATES
M
Water Body
Blackhawk
Brownie
Calhoun
Came lot -Sherwood
Complexb
Canadarago
Cayuga
Cedar
Cox Hollowb
Dogfish
Dutch Hollowb
George
Harriet
Isles
Kerr Reservoir
Lamb
Urban Precipi-
and/or Ration Dry Fallout
T , . Waste Rural onto pnto
P Water Land Water Body Water Body
State Discharges Runoff Surface Surface
E + + + +
E + + +
E + + +
E + + + +
E + + + +
M + + + +
E + + +
E + + + +
0 + + + +
E + + + +
0-M + + + +
E + + +
E + + +
E-M + + + 0
0 + + + +
Ground
Water Woodland
Seepage Runoff
ft +
+ +
+ +
+
0 0
ft +
+ +
+ +
0 +
0 +
+ +
+ +
0 +
0 +
Marsh Nitrogen
Drainage Fixation
+
+ ft ft
+ ft ft
+
0
-
+ ft ft
+
0 **
-
+ ft ft
+ ft ft
+ 0
0 ft ft
-------
Table 13 (Continued). SUMMARY OF NUTRIENT SOURCES
CONSIDERED IN US OECD WATER BODY NUTRIENT LOADING ESTIMATES
Water Body
Meander
Mendota
Michigan
Minnetonka
Potomac
Estuary
Redstone
Sallie
Sammamish
Shagawa
Stewart5
Tahoe
Twin Lakes
Twin Valley5
Virginia
Trophic
State3
0
E
0-M
E--M
U-E
E
E
M
E
E
U-0
E
E
E
Waste
Water
Discharges
4
4
4
+
+
+
+
4
4
+
4
4
4
4
Urban Precipi-
and/or tation Dry Fallout
Rural onto onto
Land Water Body Water Body
Runoff Surface Surface
44 +
4 + +
44 +
44
40
44 4
44- -
44 _
+ 4- 4
44 4
44
44 A
44 4
44 4-
Ground
Water
Seepage
0
4
4
-
0
4-
4
0
-
4
0
4
4
4
Woodland
Runoff
4
0
4
-
4
4
4-
4-
4-
4
4
4
4-
4-
Marsh
Drainage
0
0
4
4
-
4
4
4
0
4
4
0
+
4-
Nitrogen
Fixation
z *
4
-
* f:
-
-
-
-
_
-
-
*
_
_
-------
Table 13(Continued). SUMMARY OF NUTRIENT SOURCES
CONSIDERED IN US OECD WATER BODY NUTRIENT LOADING ESTIMATES
Water Body
Waldo
Washington
(1974)
Weir
Wingra
Urban Preoipi-
and/or tation Dry Fallout
^ , . Waste Rural onto onto
.ropnic Water Land Water Body Water Body
State Discharges Runoff Surface Surface
U-0 + + +
M + +
M + + +
E + + + +
Ground
Water Woodland Marsh Nitrogen
Seepage Runoff Drainage Fixation
+ + o -
+ + + -
+ + 0
+ + +
EXPLANATION:
+ = considered in nutrient budget calculations
- = not considered in nutrient budget calculations
0 = considered to be insignificant in nutrient budget
* = considered in nutrient budget calculation, but significance unknown
* * = nitrogen budget not calculated
Investigator indicated trophic state:
E - eutrophic
M = mesotrophic
0 = oligotrophic
U = ultra
Nutrient budget calculated from watershed land use nutrient export coefficients.
-------
Table 14.
IDENTIFICATION KEY FOR
US OECD WATER BODIES
Water Body Identification Investigator-
Number Indicated
Trophic Status
Blackhawk
Brownie
Calhoun
Came lot -Sherwood
Canadarago
-1968
-1369
Cayuga
-1972
-1973
Cedar
Cox Hollow
Dogfish
-1971
-1972
Dutch Hollow
George
Harriet
Isles
Kerr Reservoir
Whole Reservoir
-Roanoke Arm
-Nutbush Arm
Lamb
-1971
-1972
1
2
3
4
5 -A
5-B
6 -A
6-B
7
8
9
10
11
12
13
14
15
16
17
18
19
Eutrophic
Eutrophic
Eutrophic
Eutrophic
Eutrophic
Mesotrophic
Eutrophic
Eutrophic
Oligotrophic
Oligotrophic
Eutrophic
Oligotro ohic-
Mesotropnic
Eutrophic
Eutrophic
Eutrophic-
Mesotrophic
Oligotrophic
Oligotrophic
Location
Wisconsin
Minnesota
Minnesota
Wisconsin
New York
New York
Minnesota
Wisconsin
Minnesota
Wisconsin
New York
Minnesota
Minnesota
North
Carolina,
Virginia
Minnesota
115
-------
Table 14
(Continued) IDENTIFICATION KEY FOR
US OECD WATER BODIES
Water Body Identification Investigator-
Number Indicated
Trophic Status
Meander
-1971
-1972
Mendota
Michigan (open waters)
-1971 , T = 30 yrs
-1974 ' U
-1971
-1974 } TU = 10° yrs
20
21
22
2 3 -A
24-A
23-B
24-B
Oligotrophic
Oligotrophic
Eutrophic
(changing)
Oligotrophic
Oligotrophic
Location
Minnesota
Wisconsin
Michigan,
Wisconsin
Michigan (nearshore waters)
-1971
-1974
Lower Lake Minnetonka
-1969
-1973
Potomac Estuary
Whole Estuary
-Up'per Reach
-Middle Reach
-Lower Reach
Redstone
Sallie
Sammamish
Shagawa
Stewart
Tahoe
23-C
24-C
25
26
27
28
29
30
31
32
33
34
35
36
Eutrophic
Eutrophic
(changing)
Ultra -Eutrophic
Eutrophic
Eutrophic
Mesotrophic
Eutrophic
Eutrophic
Ultra-
Oligotrophic
Minnesota
Maryland ,
Virginia
Wisconsin
Minnesota
Washington
Minnesota
Wisconsin
California,
Nevada
116
-------
Table 14 (Continued) IDENTIFICATION KEY
FOR US OECD WATER BODIES
Water Body Identification Investigator-
Number Indicated
Trophic Status
Twin Lakes
East Twin Lake
-1972
-1973
-1974
West Twin Lake
-1972
-1973
-1974
Twin Valley
Virginia
Waldo
Washington
-1957
-1964
-1971
-1974
Weir
Wingra
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Eutrophic
(changing)
Eutrophic
Eutrophic
Eutrophic
Eutrophic
Eutrophic
Eutrophic
Eutrophic
Eutrophic
Ultra-
Oligotrophic
Eutrophic
Eutrophic
Mesotrophic
Mesotrophic
Mesotrophic
Eutrophic
Location
Ohio
Wisconsin
Wisconsin
Oregon
Washington
Florida
Wisconsin
117
-------
Vollenweider Mean Phosphorus/Influent Phosphorus And Hydraulic
Residence Time Relationship
The first method used by these reviewers to check the reason-
ableness of the US OECD eutrophication study phosphorus loading
estimates involved the use of the relationship between the average
influent phosphorus concentration and the mean phosphorus concen-
tration in the water body. Equation 20 may be rearranged as
follows:
CP]oo/(L(P)/qs) = 1/(1 + /zTq^) (25)
Recalling L(P)/q = [P] and z/q = T , then Equation 25 becomes
S S CO
[p]/rp] = i/d +~T) (26)
ra
According to Vollenweider (1975b; 1976a), the average influ-
ent phosphorus concentrations are generally higher than the mean
water body phosphorus concentrations because of the continuous
loss of phosphorus to the sediments. In a highly flushed water
body (i.e., hydraulic residence time, T , < 0.5 yr) , which would
exhibit very little relative sedimentation of phosphorus because
of the rapid flow of phosphorus through the water body, the ratio
of the mean phosphorus concentration to the influent phosphorus
concentration approaches unity. With less rapidly flushed water
bodies, there is an increasing involvement of the input phos-
phorus with the water body metabolism and a resultant deviation
of this ratio from unity. This deviation can become positive or
negative, depending on whether phosphorus accumulates in the
water phase or the sediment phase of the water body. In actual-
ity, the ratio of the water body mean phosphorus concentration
to the average influent phosphorus concentration defines the
ratio of the re'sidence time of phosphorus to the residence time
of water (i.e., ^p/Tto::'1Tr ) •> though in principle this definition
applies to any substance flowing into a water body. It can also
be used to check on the phosphorus sedimentation rate (Vollen-
weider, 1976a). The derivation and implications of the relative
phosphorus residence time, TT^ , have been discussed in an earlier
section of this report (See Equations 13-16).
The reasonableness of the US OECD eutrophication study phos-
phorus loading estimates can be checked with the use of Equation
26. A water body's influent phosphorus concentration, [p] , can
be calculated as L(p) /qs . The ratio of its mean phosphorus to in-
fluent phosphorus concentration, [P]/[pJ, can then be compared
to its hydraulic residence time expression, 1/(1 + /T^) • The
relationship expressed above in Equation 26 can be used as a
check on the phosphorus loading estimates since the influent
phosphorus concentration is a function of the phosphorus loading.
Any major deviations of [P]/[P] from 1/(1 +>|rT^p would make the
reported phosphorus loading data suspect. Vollenweider has used
this relationship successfully to trace loading errors in the
phosphorus budgets for Lakes Constance (Vollenweider, 1975c) and
Lunzer See (Vollenweider, 1975d). The use of Equation 26 to check
118
-------
on the accuracy of a water body's phosphorus loading estimate
requires that the water body mean phosphorus concentration be
accurately known. No equivalent relationship has been derived
by Vollenweider for checking nitrogen loading estimates, al-
though a similar approach would likely be applicable.
The relationship expressed in Equation 26 has been applied
to the US OECD eutrophication study phosphorus loading estimates.
The pertinent data are presented in Table 15. A missing water
body identification number indicates that necessary data for
the relationship expressed in Equation 26 were not available for
a given water body for a particular time period. For example,
there is insufficient data for Dogfish Lake-1971 (Identification
Number 9). Consequently, it was not included in Table 15.
Similar reasoning holds for any missing water body identification
numbers in any of the tables in this report. Refer to Table 14
for identification of any water bodies and/or time periods not
included in a given table or figure in this report. A plot
(Figure 14-) has been prepared which graphically illustrates the
relationship indicated in Equation 26. The US OECD data, as
reported by the US OECD investigators, are also presented in
Figure 14-. If a data range was reported for a water body, the
mean value was used in all calculations. The solid line in
Figure 14 signifies a perfect agreement between [P]/[P] and
!/(!+ /"r^") . According to the Vollenweider relationship
(Equation 26), if the phosphorus loading was overestimated (i.e.,
the phosphorus loading L(P) is actually smaller than that re-
ported by the US OECD investigator), then the water body would
plot below the solid line. Conversely, if the phosphorus load-
ing were underestimated (i.e., the phosphorus loadings are actu-
ally higher than those reported by the investigator), the water
body would plot above the solid line. The broken lines indicate
the degree of possible over- or underestimation of the US OECD
investigator-indicated phosphorus loadings relative to that
predicted by the hydraulic residence time expression in Equation
26. The "+2x" broken line below the solid line indicates the
US OECD investigator-indicated phosphorus loading estimate may
have been overestimated (i.e., +) a factor of 2 (i.e., 2x) . Con-
versely, the "-3x" broken line above the solid line indicates
the phosphorus loading estimates may have been underestimated (-)
by a factor of 3 (3x). The shaded zone between ± 2x indicates the
range within which the phosphorus loadings were considered to be
reasonable by these reviewers. The basis for the choice of this
range of acceptable deviation will be discussed further in a follow-
ing section.
As can be seen in Figure 14, almost no water bodies fall
directly on the solid line. However, many of the water bodies
fall within the shaded area between the broken lines representing
a + two-fold possible phosphorus loading estimate error. This indi-
cates the US OECD phosphorus loading estimates generally appear to
119
-------
Table 15. US OECD DATA FOR VOLLENWEIDER'S MEAN PHOSPHORUS/
INFLUENT PHOSPHORUS AND HYDRAULIC RESIDENCE TIME
RELATIONSHIP
Trophic
Water Body State3
Blackhawk (l)e
Brownie (2)
CaLhoun (3)
r-o Camelot-Sherwood(4
o
Canadarago ( 5 )
Cayuga (6)
Cedar (7)
Cox Hollow (8)
Dogfir.h (10)
Dutch hollow (11)
George ( ] 2 )
Harriet (13)
Isles (14)
Kerr Reservoir
ivoanoke Arm (16)
flutbush Arm (17)
E
E
E
) E
E
M
E
E
0
E
0-M
E
E
E-M
-
_
Phosphorus
Loading
(mg P/m /yr)
2220
1180
860
2350-2680
800
800
350
1620-2080
20
950-1010
70
710
2030
5200
700
Hydraulic
Loading, q
b (m/yr)c
9
3
2
21.4
12
6
1
5.4
1
1
2
3
4
51
1
.8
.4
.94
-33.3
.8
.3
.8
-7 .6
.14
.67
. 25
.67
.5
.5
.6
Influent
Phosphorus
Concentration
[P]
(mg/m3)d
227
347
292
70 .6-125
62 .4
127
189
213-385
17.5
569-605
31.1
194
451
101
435
Mean
Phosphorus
Concentration ,
[P] CP]
(mg/m3)b
50-120
_
106f
30-40
40-50
20
55f
60-100
10
120-400
8 .5
62f
110f
30
30
[P]
0.22-0.52
_
0 .36
0 .24-0.57
0.64-0 .80
0 .15
0 .29
0 .16-0.47
0 .57
0 .20-0 .70
0.27
0. 32
0 .24
0 .30
0 .07
1
" + V\?
0 .58
0.41
0 .34
0 .73-0 .77
0 .56
0 .25
0 .36
0.54-0.58
0 .48
0 .43
0.26
0.39
0 .56
0 .69
0 .31
-------
IS (continued). US OFCD DATA FOR VOLLKNWF: JDER ' 5 MEAN
PHOSPHORUS/INFLUENT piio.srnoRus AND HYDRAULIC
RESIDENCE TIMI: RELATIONSHIP
Trophic
Water Body Statea
Lamb (19)
Meander (21)
Mendota (72)
Michigan
Open Waters(23-A)
(23-B)
0
0
E
0
Phosphorus Hydraulic
Loading Loading, q
(mg P/m2/yr)b (m/yr)c
30
30
1200
140
140
1 .74
1 .85
2.67
2 .8
0 .84
Influent
Phosphorus
Concentration
^\
(mg/ni )d
17 .2
16 .2
450
50
367
Mean
Phosphorus
Concentratior
[P]
(mg/m3)b
12-13
9-12
ISO
13
13
i ,
[P]
m
0.69-0.76
0 .56-0 .74
0.33
0.26
0.08
1
-------
Table 15 (continued). US OECD DATA FOR VOLLENWEIDCR'S MEAN
PHOSPHORUS/INFLUENT PHOSPHORUS AND HYDRAULIC
RESIDENCE TIME RELATIONSHIP
Trophic
Water Body State3
Tahoe (36)
East Twin
1972 (39)
1973 (40)
1974 (41)
West Twin
1972 (43)
1973 (44)
1974 (45)
Twin Valley (46)
Virginia (47)
Waldo (48)
Washington
1957 (49)
1964 (50)
1971 (51)
U-0
E
E
E
E
E
E
E
E
U-0
E
E
M
Phosphorus
Loading
(mg P/m2/yr)b
50
700(672)^
500(472)
700(816)
400(419)
300(181)
300(316)
1740-2050
1150-1480
17
1200
2300
430
Influent
Phosphorus
Hydraulic Concentration
Loading, qg fjTj
(m/yr) (mg/m )
0 .45
6.25(7.40)3
5 .56(7.19)
10.0(9.31)
2.71(0.79)
2.41(0.64)
4.34(1.03)
7.6-9.5
0.61-1.89
1.71
13.8
13.8
13.8
112
112 (91) 3
89.9(66)
70(76)
148(123)
124(65)
69.1(75)
183-270
608-2426
9.9
87 .0
167
31.3
Mean
Phosphorus
Concentration
[P]
(mg/m3)b
3
80 (83)1
80 (78)
80(77)
120(122)
110(107)
100(97)
60-70
20-150
<5h
24
66
18
[P]
[Pi
0 .03
0.71 (0.91^
0.89(1.81)
1.14(1.01)
0 .81(0.99)
0.89(1.65)
1.45(1.29)
0.22-0.38 0
0.01-0.25 0
< 0 .5
0.28
0.40
0.58
1
;i +/rj)
0 .04
0 .53 (0.54)
0.51(0.54)
0.59 (0.58)
0 .44 (0.47)
0.43(0.45)
0 .50
.58-0 .61
.37-0.51
0 .18
0 .39
0.39
0 .39
-------
Table 15 (continued). US OECD DATA FOR VOLLENWEIDER'S MEAN
PHOSPHORUS/INFLUENT PHOSPHORUS AND HYDRAULIC
RESIDENCE TIME RELATIONSHIP
Water Body
Weir (53)
Wingra (54)
Trophic
State3
M
E
Phosphorus
Loading
(mg P/m2/yr)b
140
900
Hydraulic
Loading, q
(m/yr)c
1.5
6.0
Influent
Phosphorus
Mean
Phosphorus
Concentration Concentration,
[P]
-------
o
tr
i-
z
LJ
O
Z
O
O
co
:D
cr
o
o.
CO
O
X
Q.
V-
z
-20X
-iox
cr
h-
z
LL)
O
Z
O
o
CO
z>
cr
o
a.
CO
O
X
a.
LJ
2
2.4
2.2
2.0
O.8
0.6
0.4
0.2
-6X
INVESTIGATOR-INDICATED
TROPHIC STATg:
- EUTROPHIC/
/A - MESOTROPHIC
O - OLIGOTROPHIC
I - LESS THAN7
-3X
UNDERESTIMATION -
il////V*-bS^ I»^—'
W/-Q?^.^^~\7
-2X
+ 2X
-I-ZX
4X
+ &X.
+ \ox
42OX
Figure 14. Evaluation of Estimates of US OECD Water Body
Nutrient Loadings: Vo 11 enwei de'r Mean Phosphorus/
Influent Phosphorus and Hydraulic Residence
Time Relationship
124
-------
be of a reasonable nature, based on the Vollenweider relation-
ship (Equation 26). Considering the multitude of methods used
in estimation of the phosphorus loadings (Table 12),this initial
agreement between the phosphorus loadings as indicated by the
US OECD investigators and the phosphorus loadings as indicated
by the Vollenweider relationship (Equation 26) is reassuring and
provides some affirmation of the Vollenweider loading diagram ap-
proach to establishing the critical phosphorus loading levels
and relative trophic conditions of water bodies. Equation 26
will be discussed in greater detail in relation to the Vollen-
weider phosphorus loading diagrams presented in subsequent sec-
tions of this report.
Watershed Land^ Use Nutrient Export Coefficients
The other principal method used by these reviewers for
checking the reasonableness of the phosphorus loading estimates,
as well as the nitrogen loading estimates, reported by the US
OECD investigators was to compare the reported loadings with
those computed using watershed nutrient export coefficients.
The nutrient export coefficients used to estimate the nutrient
loadings from a given watershed would depend on the land usage
pattern within the watershed. Because no relationship equivalent
to Equation 26 has been derived for nitrogen loadings , the use
of watershed nitrogen export coefficients represents the only
independent method available to these reviewers for checking the
accuracy of the nitrogen loadings reported by the US OECD inves-
tigators .
This procedure involves utilization of the information
available on land usage within a lake's or impoundment's water-
shed and the nutrient coefficients which are applicable to the
various land uses within that watershed. For example , a hectare
of corn or a suburban subdivision are known to yield a relatively
constant amount of aquatic plant nutrients over the annual cycle
(see Sonzogni and Lee (1974), for further discussion of this ap-
proach) . The use of this approach for computing nutrient load-
ings to a water body requires an accurate estimation of the water
body's watershed area and the land usage pattern within the
watershed. The US OECD investigators reported watershed land
usage in varying degrees, with some investigators producing only
sparse watershed land usage data, while others went into great
detail concerning land usage within the watershed.
Uttormark et al_. (1974), based on the results of their exten-
sive survey, have reported there is little justification for
the delineation of land usage within direct drainage basins be-
yond four categories: urban, forest, agriculture and wetlands.
Available data are too fragmentary and variable to warrant fur-
ther subdivision of land usage categories, according to Uttor-
mark et_ al. (1974). The US EPA has taken the same general
approach in categorizing watershed land usage types as urban,
125
-------
agriculture, mostly agriculture, forest, mostly forest and mixed
(US EPA, 1974c; 1975c). Vollenweider (1977) has recently indi-
cated, based on studies of German watershed land usage, that a
distinction between arable land and pastures and meadows may be
useful because these two classes of land use types export dis-
tinctly different quantities of phosphorus and nitrogen from the
watershed. However, it is noted that the values reported by
Vollenweider are considerably above the North American values
reported by Uttormark et_ al. (1974). Typical values of water-
shed nutrient export coe"f fTcients are presented in Table 16.
It is noted that while wetlands can act as sinks or sources of
nutrients, depending on the season of the year, in general the
net nutrient contribution from wetlands is considered to be zero
(Sonzogni and Lee, 1974; Uttormark et_ al. , 1974, Lee e_t al_. , 1975).
Table 16 indicates that several different nutrient export
coefficients, varying widely in several cases, were available
for each watershed land use category (i.e., 0.1 g/m^/yr (Sonzogni
and Lee, 1974) vs. 0.03 g/m2/yr (US EPA, 1974c) for urban phos-
phorus export coefficient). As a result, the coefficients chosen
to check the reported US OECD nutrient loadings are based largely
on the experience of these reviewers and also on the regional
nature of several of these values. For example, it was felt by
these reviewers that the urban phosphorus and nitrogen export co-
efficients of Sonzogni and Lee (1974) represent a reasonable
average of the values reported by Uttormark et al. (1974) and by
the US EPA (1974c). The US EPA urban phosphorus~and nitrogen ex-
port coefficients were based on studies done in 473 subdrainage
areas in the eastern US. The coefficient of Sonzogni and Lee
(1974) is also regional in that it was derived for the Lake Men-
dota, Wisconsin, watershed. However, it is more in agreement with
that reported by Uttormark et al. (1974) than is the US EPA (1974c)
value. While the, coefficients of Uttormark et al. are also
derived from studies confined mainly to the nortTTeastern and upper
midwestern US, they are also based on several studies done in the
southern and western US and, therefore, represent more of a
'national average' than do the values of Sonzogni and Lee or the
US EPA. Consequently, a certain bias was given to the values of
Uttormark et al. (1974) as a reference national average value,
even' though~the~y were based on studies confined largely to the
upper midwestern and northeastern US.
2
A rural/agriculture phosphorus value of 0.05 g/m /yr was
taken as an average of the values of Sonzogni and Lee (1974) and
both Uttormark ejt al. (1974) and the US EPA (1974c). A rural/
agriculture nitrogen export coefficient of 0.05 g/m2/yr was used
because of the agreement between the value of Sonzogni and Lee
and that of Uttormark et al, The forest phosphorus export
coefficient of Uttormark" et" al. was thought to be too high, based
on the experience of these reviewers and on the "mostly forest"
value reported by the US EPA. Consequently, the US EPA (1974c)
forest phosphorus export coefficient of 0.01 g/m2/yr was used by
these reviewers. A forest nitrogen export coefficient of
126
-------
Table 16 TYPICAL VALUES OF WATERSHED NUTRIENT EXPORT
COEFFICIENTS
Watershed
Land Usage
Source :
and Lee
Sonzogni
(1974)
Source :
et_ al_.
: Uttormark
(1974)a
Source : US
Cl974c)
EPA
A. Total Phosphorus (g P/m /yr)
Urban 0.1 0.15 0.03 ,
Rural/Agriculture 0.07 0.03 0.03 (0.02)D
Forest - 0.02 0.01 (0.02)
Wetlands Net nutrient contribution is considered tc be zero.
Other:
Rainfall onto
water body surface 0.02
Dry fallout onto
water body surface 0.08 - ,
.mixed = 0.02
B. Total Nitrogen (g N/m /yr)
Urban 0.5 0.5 0.8
Rural/Agriculture 0.5 0.5 1.0(0.6)D
Forest - 0.25 0.4(0.4)°
Wetlands Net nutrient contribution is considered to be zero.
Other:
Rainfall onto
water body surface 0.8
Dry fallout onto
water body surface 1.6 - -
mixed - 0.6
a"Average" value indicated by Uttormark e_t al. (1974).
Mostly agriculture; other types present.
Q
Mostly forest ; other types present.
Does not fit into any of the other watershed land use categories.
127
-------
2
0.3 g/m /yr was taken as an average of the values reported by
Uttormark et al. and the US EPA. The one exception to these
values is that the "low" nitrogen export coefficients reported
by Uttormark et al. (1974) were used as a check on the reported
nitrogen loadTngsr~of the US OECD water bodies located in the
western US. These low values were used because most water bodies
in the western US tend to be nitrogen-limited with respect to
aquatic plant nutrient requirements. It was felt by these re-
viewers that the low nitrogen values were more accurate than the
"average" values reported by Uttormark et al. (1974). These low
nitrogen values were used for calculating' tTTe nitrogen loadings
for Lakes Tahoe, Waldo, Sammamish and Washington.
The values for the nutrient contributions to the US OECD
water bodies from precipitation and dry fallout directly onto
the water body surface, if not indicated by the investigator,
were taken from Sonzogni and Lee (1974). While precipitation
and dry fallout nutrient contributions likely vary from location
to location, the portion of nutrients contributed by precipitation
or dry fallout onto a water body's surface was usually small,
compared to the magnitude of the other input sources. Conse-
quently, it was not considered a serious source of error to use
the values reported by Sonzogni and Lee (1974) .
A summary of the watershed land use nutrient export coef-
ficients used by these reviewers as a check on the reported US
OECD water body nutrient loadings is presented in Table 17.
Table 17. WATERSHED NUTRIENT EXPORT COEFFICIENTS USED TO CHECK
US OECD NUTRIENT LOADINGS
Watershed Watershed Export Coefficient
Land Use (g/m^/yr)
A. Total Phosphorus
Urban 0.1
Rural/Agriculture 0.05
Forest 0.01
Other:
Rainfall 0.02
Dry Falout 0.08
B. Total Nitrogen
Urban 0.5 (0.25)a
Rural/Agriculture 0.5 (0.2)a
Forest 0.3 (0.1)a
Other:
Rainfall 0.8
Dry Fallout 1.6
aExport coefficients used in calculating nitrogen loadings for
US OECD water bodies in western US (i.e., Lakes Tahoe, Waldo,
Sammamish and Washington).
128
-------
In order to use these watershed land use and atmospheric
nutrient export coefficients, the percentage of each of the four
land use types in the watershed was determined from the data
provided by the US OECD investigators. In some cases, an inter-
pretation of a given watershed land usage type was used for this
report if the US OECD investigator's description did not fit
into any of the four watershed land use categories reported by
Uttormark et al. (1974) (i.e., "residential," "commercial,"
"industrial,"""public, semipublic transportation" and "mining"
all being placed in the 'urban' category; "outdoor recreation"
put into the 'forest' category, etc.). In general, the effect
of the occasional liberal usage of watershed land use categories
by these reviewers have tended to overestimate the nutrient load-
ings to the US OECD water bodies to some extent. In most cases,
the investigator's reported watershed land usages conformed to
the general categories defined by Uttormark et al. (1974). How-
ever, the methods employed in determining the watershed land usage
patterns, or the sources of the watershed land usage data, if it
was not directly determined, were usually not indicated by the
US OECD investigators. Any other nutrient contribution values used
in this portion of the report were those supplied by the US OECD
investigators for their particular water bodies. These included
wastewater discharges, groundwater inputs, spring inputs, nitrogen
fixation (for nitrogen loading estimates) and marsh drainage.
The total phosphorus and total nitrogen loadings , as calcu-
lated using watershed land use nutrient runoff coefficients, are
presented in Table 18. The US OECD investigator-indicated total
phosphorus and total nitrogen loadings are included in Table 18
for comparison with the loadings derived from watershed land use
nutrient export coefficients. The ratio of the export coefficient-
derived nutrient loadings to the investigator-indicated loadings
is also presented in Table 18. A ratio of one indicates agreement
between the investigator-indicated nutrient loadings and the nu-
trient loadings calculated from watershed nutrient export coef-
ficients . A ratio greater than one indicates the investigator-
indicated nutrient loadings may have been underestimated, rela-
tive to the nutrient loading estimates obtained from the water-
shed land usage calculations. That is, the investigator-indicated
nutrient loading is lower than the loading based on the watershed
nutrient export coefficients listed in Table 17. Conversely, for a
ratio less than one, the possibility of a nutrient loading over-
estimation is indicated.
According to Piwoni and Lee (1975) the nutrient loadings
for Lakes Blackhawk, Camelot-Sherwood, Cox Hollow, Dutch Hollow,
Redstone, Stewart, Twin Valley and Virginia were calculated using
nutrient export coefficients derived by Sonzogni and Lee (1974).
Since the nutrient export coefficients derived by Sonzogni and
Lee (1974) are different for some land use types than those used
by these reviewers, comparing the reported nutrient loadings for
129
-------
Table 18. US OECD NUTRIENT LOADINGS CALCULATED USING
WATERSHED NUTRIENT EXPORT COEFFICIENTS
Ratio of Export
Loadings Coefficient
b Calculated Investigator- Loadings to
Point-Source Non-Point Source Loading via Export Indicated Investigator-
Loading3 (g/yr) Coefficients Loadings Indicated
Water Body (g/yr) Urban Rural Forest Other (g/»2yr) (g/™ /yr)a Loadings
A. PHOSPHORUS LOADINGS:
Brownie Watershed land usage data not available
(2)d
h- '
co
CD
Calhoun Watershed
(3)
Canadarago 2.8x10
Cayuga 6.39x10
(6)
land usage data not' available
6.02xl05
7.32xl06
(Includes
commercial
4.3xl06 6.02xl05 7.6xl05 1.2 0.8
5.95xl07 0 1.7xl07 0.9 0.8
(Includes
, active £
1.5
1.1
Cedar
(7)
Dogfish
(10)
George
(12)
Harriet
(13)
industrial inactive
mining,pub- agriculture)
lie and
transportation)
Watershed land usage data not available
0 00 5.9xlOc
Watershed land usage data not available
Watershed land usage data not available
2.9x10
0.1
0.02
-------
Table 18 (continued). US OECD NUTRIENT LOADINGS CALCULATED
USING WATERSHED NUTRIENT EXPORT COEFFICIENTS
Water Body
Isles
(14)
Kerr Reser-
voir (Whole
reservoir )
(15)
Lamb
(19)
Meander
(21)
Mendota
(22)
Point-Source
Loading3
(g/yr)
Non-Point
Urban Rural
Watershed land usage data not
7
2. 34x10
0
0
0
R ft
2x10 3x10
0 0
0 0
7.81xl06 2.7x10
Source Loading
(g/yr)
Forest
available
a
1. 2x10
1.6xlOU
1. 34xl04
7 6.51xl04
b
Other0
7
3.2x10
4xl04
3.6X104
1.09xl07
( Includes
Loadings
Calculated
via Export
Coefficients
(g/nryr)
4.0
0.1U
0. 14
1.2
Investigator-
Indicated
Loadings
(g/m2/yr)a
4.0
0.03
0.03
1.2
Ratio of Export
Coefficient
Loadings to
Investigator-
Indicated
Loadings
1. 0
4.7
4.7
1.0
grouridwater,
Michigan
Lower Lake
Minnelonka
Potom.ic
EL. tuary
Watershed lar
id usage data not
Watershed land usage data not
H x 109
(Median flow
available
available
1.86xl08 7.46xl08 2.05xl08
regime)
baseflow,
storm
drainage )
9.67xl07
E
5.4
5. 0
1.1
(entire <;b tuary)
(27)
-------
Table 18 (continued). US OECD NUTRIENT LOADINGS CALCULATED
USING WATERSHED NUTRIENT EXPORT COEFFICIENTS
Water Body
Sallie
(32)
Sanunamish
( following
diversion of
sewage )
(33)
Shagawa
(34)
Tahoe
(36)
Twin Lakes
(East Twin £
West Twin
combined)
1972
(39 £ 43)
1973
(40 £ 44)
1974
(41 £ 45)
Ratio of Export
Loadings Coefficient
b Calculated Investigator- Loadings to
Point-Source Non-Point Source Loading via Export Indicated Investigator-
Loading3 (g/yr) Coefficients Loadings Indicated
(g/yr) Urban Rural Forest Other0 (g/m yr) (g/m2/yr)a Loadings
2!oixlo7 4.5xl06 3.38xlO? 3.45xl06 1.15xl06 9.4-12.1 1.5-4.2 2.2-8.1
5xl05 2.75xl06 3.75xl05 2.15xl06 2.6xl06 0.4 0.7 0.6
5.18xl06 1.7xl06 1.31xl05 2xl06 8.86xl05 1.1 0.7 1.6
7 67
0 2.88x10 0 4.72x10 5x10 0.17 0.05 3.4
r o r _
0 1.0x10 0 8.02x10 2.4x10 0.57 0.5l(0.53)K i.id.lp
r Q C
0 1.0x10 0 8.02x10 2.4x10 0.57 0.40(0.31) 1.4(1.8)
r . T r
0 1.0x10 0 8.02x10 2.4x10 0.57 0.45(0.54) 1.3(1.1)
-------
Table 18 (continued). US OECD NUTRIENT LOADINGS CALCULATED
USING WATERSHED NUTRIENT EXPORT COEFFICIENTS
Water Body
Waldo
(48)
Washington
(assumed 90
forest and
10 percent
1957
(49)
1964
(50)
1971
(51)
1974
(52)
Weir
(53)
Wingra
(54)
Point- Source
Loading3
(g/yr)
0
percent
urban )
7
5. 7x10
1. 04xl08
0
0
0
0
Non-Point
Urban Rural
0 0
7
1.61x10 0
l.GlxlO7 0
1.61xl07 0
i.eixio7 o
3.68xl05 1.7xl06
l.OSxlO6 0
K
Source Loading"
(g/yr)
Forest
5. 2xl05
7
1.45x10
1.45xlO?
1. 45xl07
1.45xlO?
8.74xlOM
3.13xl04
Other0
2.88xl06
c
8.8x10
8.8xl06
8.8xl06
8.8xl06
3.5xl06
( includes
Loadings
Calculated
via Export
Coefficients
(g/m yr)
0.12
1.09
1.63
0.45
0.45
0. 24
Ratio of Expon
Coefficient
Investigator- Loadings to
Indicated
Loadings
(g/m2/yr)a
0.02
1. 2
2.3
0.43
0.47
0.14
Investigator-
Indicated
Loadings
6. 3
0.9
0.7
1.0
1.0
1.7
septic tanks)
2. 19xl05
( includes
0.93
0. 9
1.0
spring flow)
-------
Table 18 (continued). US OECD NUTRIENT LOADINGS CALCULATED
USING WATERSHED NUTRIENT EXPORT COEFFICIENTS
Water Body
Ratio ol Export
Loadings ^ Coefficient
k Calculated Investigator- Loadings to
Point-Source Non-Point Source Loading via Export Indicated Investigator-
Loading3 (g/yr) Coefficients Loadings Indicated
(g/yr) Urban Rural Forest Other (g/m2yr) (g/m2/yr)a Loadings
B. NITROGEN LOADINGS
M
CO
-P
Brownie
(2)
Calhoun
(3)
Canadarago
(5)
Cayuga
Cedar
(7)
Dogfish
George
(12)
Harriet
(13)
Nitrogen
Nitrogen
7.8xl06
B
1.68x10
Nitrogen
Nitrogen
Watershed
Nitrogen
_e
loadings not
loadings not
3-OlxlO6
7
3.66x10
loadings not
loadings not
land usage
loadings not
determined
determined
4.3xl07 l.SlxlO7 1.79xl07 11.8 18.0 0.7
R R R
5.95x10 1.76x10 4.01x10 8.1 14.3 0.6
(does not
include organic
nitrogen)
determined
determined
data not available
determined
-------
Table 18 (continued). US OECD NUTRIENT LOADINGS CALCULATED
USING WATERSHED NUTRIENT EXPORT COEFFICIENTS
Water Body
Isles
(14)
Kerr Reser-
voir (Whole
reservoir)
(15)
Lamb
(19)
Meander
(21)
Mendota
(22)
Michigan
Lower Lake
Minnetonka
Potomac
Es tuary
Point-Source Non-Point
Loading3
(g/yr) Urban Rural
Watershed
7
2 . 34x10
0
0
0
Watershed
Watershed
4 x 109
land usage data not
R a
2x10 3x]0
0 0
0 0
p.
7.81x10 2.7x10
land usage data not
land usage data not
Source Loading
(g/yr)
Forest
available
8
1. 2x10
,
1. 6x10
h
1. 34x10
7 U
6.51x10
available
available
1.86xl08 7.46xl08 2.05xlQ8
Loadings
b Calculated
via Export
Coefficients
Other (g/m yr)
7
3.2x10 4.0
u
4x10 0.14
M
3.6x10 0.14
7
1.09x10 1.2
( Includes
groundwater,
baseflow, £
storm
drainage )
9.67xl07 5.4
Investigator-
Indica ted
Loadings
(g/m^/yr )
4. 0
0. 03
0.03
1. 2
5. 0
Ratio of Export
Coefficient
Loadings to
Inves tigator-
Indicated
Loadings
1. 0
4.7
4. 7
1. 0
1.1
(Median flow regime)
(entire estuary)
(27)
-------
Table 18 (continued). US OECD NUTRIENT LOADINGS CALCULATED
USING WATERSHED NUTRIENT EXPORT COEFFICIENTS
Water Body
Sallie
(32)
Sammamish
( following
sewage
diversion )
(33)
Shagawa
£ "4)
cn f
Tahoe
(36) f
Twin Lakes
(East Twin
& West Twin
Combined)
1972
(39 g 43)
1973
(40 £ 44)
Point-Source
Loading3
(g/yr)
5. 59x10-
1. 14xl07
Unknown
1.93xl07
0
Lake
Lake
0
0
b
Non-Point Source Loading
(g/yr)
Urban Rural Forest Other
2.25xlO? 3.38xl08 1.04xl08 1.
2.
6.88xl06 l.SxlO6 2.15xl07 4.
8.48xl06 1.3xl06 6.03xl07 1.
2 .
7.2xl07 0 4.72xl07 9.
5.01xl05 0 8.02xl04 5.
r h
5.01x10 0 8.02x10 5.
59x10^
13x10
72xlO?
84xl07-
37x10
04xl08
27xl06
R
02x10
Loadings
Calculated
via Export
Investigator-
Indicated
Coefficients Loadings
(g/m yr) (g/n)2/yr)a
91.6-93.8
-
11.7-12.3
2 . 0
9.6
9.2
2. R-3-0
13. 0
7.8
0. 52
22.6
16.8
(does not
Ratio of Expor
Coefficient
Loadings to
Investigator-
Indicated
Loadings
30-34
-
1.5-1.6
3 .8
0.4
0. 5
include organic
nitrogen)
-------
Table 18 (continued). US OECD NUTRIENT LOADINGS CALCULATED
USING WATERSHED IJUTRIENT EXPORT COEFFICIENTS
Ratio of Exporl
Loadings Coefficient
, Calculated Investigator- Loadings to
Point-Source Non-Point Source Loading via Export Indicated Investigator-
Loading9 (g/yr) _ Coefficients Loadings _ Indicated
Water Body
Waldof
(48)
Washington
(assumed 10
urban and 90
forest )
1957
(49)
1964
(50)
1971
(51)
1974
(52)
Weir
(53)
(g/yr)
0
percent
percent
2.01xl08
2. 71xl08
0
0
0
Urban Rural Forest
0 0 5.2xl06
4.02xl07 0 1.45xl08
4.02xl07 0 1.45xl08
4.02x10'' 0 1.45xl08
4.02xl07 0 1.45xl08
1.84xl06 1.68xl07 2.64xl06
( includes
pasture)
Other (g/mzyr)
5.4xl07 2.2
2.07xl08 6.7
2.07xl08 7.5
2.07xl08 4.4
2.07xl08 4.4
5.3xl07 3.1
( includes
septic tanks)
(g/m'/yr) Loadings
0.33 6.6
19. 2 0.3
7.8 1.0
4.6 1.0
4.4 1.0
2.6 1.2
-------
Table 18 (continued). US OECD NUTRIENT LOADINGS CALCULATED
USING WATERSHED NUTRIENT EXPORT COEFFICIENTS
h- >
co
Point-Source
Loading3
Non-Point Source Loading
(g/yr)
Ratio of Export
Loadings Coefficient
Calculated Investigator-Loadings to
via Export Indicated Investigator-
Coefficients Loadings Indicated
Water Body
Wingra
( 54)
(g/yr)
0
Urban Rural Forest Other (g/m yr)
5.24xlOR 0 9.38x10° V.SVxlQ6 9.8
(includes
spring flow)
(g/m2/yr)'
5.1
Loadings
1.9
Based on investigator's estimates.
b
Watershed land usage as defined by Uttormark et al. (1974) and indicated by the investigator.
cAs indicated by the investigator. Precipitation and dry fallout nutrient inputs,
if not indicated by the investigator, were calculated using the nutrient coefficients
given in Sonzogni and Lee (1974). Other loadings are as indicated in the table.
d '
Identification number for Figures 15 and 16 (see Table 14 ).
eNitrogen loadings are comprised of inorganic nitrogen (i.e., NHL +N0~+N0~ as N) plus
organic nitrogen, unless otherwise indicated.
"low" nitrogen export coefficient of Uttormark e_t al . (1974) used to determine
the nitrogen loading estimate.
CT
6Data in parentheses represent data received by these investigators from the principal investigator
subsequent to the completion of this report. Figures 15 and 16 are based on the original
data reported by the investigator and do not reflect the changes indicated above. Examination
of this subsequent data indicates the phosphorus loads were originally underestimated; however,
there were no significant changes in the overall conclusions concerning the Twin Lakes
as a result of these altered loads.
-------
these water bodies with those calculated using the nutrient ex-
port coefficients in Table 17 would obviously indicate an error
in the reported nutrient loadings. Further, it was also felt
by these reviewers that land use export coefficients calculated
for a specific watershed are likely more accurate than the average
values used in these calculations. Consequently, these water
bodies were not included in Table 18 as it would be incorrect
to check their nutrient loadings in this manner. Lake Waldo's
reported nutrient loadings are based on an average of several in-
direct methods, including land use export coefficients derived
for the Upper Klamath (Powers et al., 1975). However, since more
than one method was used by Powers et al. to calculate Lake Waldo's
nutrient loading and because the value obtained using the export
coefficient was similar to the value obtained with the other in-
direct methods, this water body was retained in Table 18.
The watershed land use-derived loading estimates for phos-
phorus and nitrogen are compared with the US OECD investigator-
indicated loadings in Figures 15 and 16, respectively. The
various lines and the shaded zone in Figures 15 and 16 have the
same meaning as those in Figure 14. Figures 15 and 16 will be
discussed in connection with the Vollenweider loadings diagrams
presented in following sections of this report.
Comparison of Phosphorus Loadings Derived From Vollenwider
Relationship With Loading^ Derived From Watershed Phosphorus
Export Coefficients.
The phosphorus loadings predicted by Vollenweider's relation-
ship in Equation 26 may be compared with the loadings predicted
with the use of watershed land use phosphorus export coefficients.
If they are similar, one can have some degree of confidence that
their use for determining the correct value for the phosphorus
loadings was somewhat justified. If they disagree to any major
extent, then one would have to question the use of one or both
of these approaches for predicting the 'correct' phosphorus load-
ings to the US OECD water bodies. Such a comparison was made
with the US OECD eutrophication study data. The predicted phos-
phorus loadings, using the Vollenweider relationship expressed
in Equation 26 and the watershed land use phosphorus export co-
efficients, as well as the ratio of the former to the latter, is
presented in Table 19. The results are presented graphically in
Figure 17. The various lines and the shaded zone in Figure 17
have the same meaning as in Figure 14. If a data range was re-
ported for a water body, the mean value was used in all calcula-
tions .
Examination of Figure 17 shows reasonably good agreement
between the phosphorus loadings predicted for the US OECD water
bodies using the Vollenweider relationship (Equation 26) and
those predicted using watershed phosphorus export coefficients.
Most of the phosphorus loadings predicted using Equation 26 are
139
-------
I 5.0
o
UJ
o
o
-20X -IOX -6X
-4X
-3X
-2X
£L
X
UJ
o
Q.
4.0
INVESTIGATOR-INDICATED
TROPHIC STATE:
• - EUTROPHIC
A - MESOTROPHIC
O - OLIGOTROPHIC
0 1.0 2.0 3.0
INVESTIGATOR-INDICATED PHOSPHORUS LOADINGS
(gP/m2/yr )
+3X
+ 6X
+ IOX
+ 20X
Figure 15.
Evaluation of Estimates of US OECD
Water Body Nutrient Loadings:
Watershed Land Use Phosphorus
Coefficient Calculations
140
-------
CO
H
50
40
UJ
a
u.
u.
LJ
O
a
X
LU
2
LL)
O
O
CC
> 30
Q *Z
U >.
5«
^ E
-20X -IOX -6X
-4X
-3X
-2X
20
to
C5
z
a
<
O
LJ
O
O
cc
O
10
0
/
CALCULATED: 92-94 )
IN VEST I GATOR'-INDICATED
TROPIC STATE:/
• - EUTROPHIC/
A - MESOTROPHIC
O- OLIGOTROPHIC
*
/
Ix
•f3X
44X
+6X
+ IOX
+20X
5 10 15 20 25 30 35
INVESTIGATOR-INDICATED TOTAL NITROGEN LOADINGS
(gN/m2/yr)
Figure 16.
Evaluation of Estimates of US OECD
Water Body Nutrient Loadings:
Watershed Land Use Nitrogen Export
Coefficient Calculations
-------
jr
ro
Table I1'. COMPARISON OF PHOSPHORUS LOADINGS DERIVED FROM WATER-
SHED EXPORT COrrFICLENTS WJTII LOADINGS PREDICTED BY
VOLLENWEIDER'S MEAN PHOSPHORUS/INFLUENT PHOSPHORUS
AND HYDRAULIT RESIDENCE TLMK RELATIONSHIP
Phosphorus Loadings Phosphorus Loadings
Predicted with Vollen- Predicted with Water- Ratio of Vollen-
weider's Relationship shed Phosphorus Ex- weider-Derivcd to
Trophic (Equation 2b)b port Coefficients0 Export Coefficient-
Water Body State3 (g/m^/yr) (g/m2/yr) Derived Loadings
Calhoun ( 3 )d
Canadarago (5)
Cayuga (G)
Cedar (7)
Dogfish (10)
George (12)
Harriet (13)
Isles (14)
Kerr Reservoir (15)
Lamb (19)
Meander (21)
Mendota (22)
Michigan
Open Waters
(23A 6 B)
Lower Lake ~
Minnetonka
Potomac Estuary
(27)
Sal lie (32)
E
E
M
E
0
0-M
E
E
E-M
0
0
E
0
E->M
U-E
E
0.9e
0-9-1.1 1.2 0.8-0.9
0.50 0.9 0.6
0.3e
0 . 0 2S 0.1 o.2
0.07
0.66
0.9e
-
0.05-0.06 0.14 0.4
0.04-0.06 0.14 0.3-0.4
1.2 1.2 !.0
0.1-0.2
~
_ __
5.4
2 .6-4,7 9.4-12.1 U .2-0.5
-------
Table 19 (continued). COMPARISON OF PHOSPHORUS LOADINGS DERIVED FROM WATER-
SHED EXPORT COEFFICIENTS WITH LOADINGS PREDICTED BY VOLLENWEIDER'S
MEAN PHOSPHORUS/INFLUENT PHOSPHORUS AND HYDRAULIC RESIDENCE TIME
RELATIONSHIP
-P
CO
Water Body
Sammamish (33)
Shagawa (34)
Tahoe (36)
Twin Lakes
(East Twin £ West
1972 (39 g 43)
1973 (40 F, 44)
1974 (41 £ 145)
Waldo (48)
Washington
1957 (49)
1964 (50)
1971 (51)
Weir (53)
Wingra (54)
Phosphorus Loadings Phosphorus Loadings
Predicted with Vollen- Predicted with Water- Ratio of Vollen-
weider's Relationship shed Phosphorus Ex- weider-Derived to
Trophic (Equation 25)b port Coefficients0 Export Coefficient-
State3 (g/m^/yr) (g/m^/yr) Derived Loadings
M
E
U-0
Twin)
E
E
E
U-0
E
E
M
M
E
0
0
0
0.7
0. G
0.9
<0
0
2
0
0
0
.4
. 8
.03
-0.9 (0.6)h
-0.9 (0.5)
-1-4 (0.6)
-05g
. 8
. 3
.6
.12
. 7
0
1
0
0
0
0
0
1
1
0
0
0
. 7
.1
.2
. 6 ( 0 . 6 )h
.6(0.6)
•6(0.6)
.12
.1
.6
.45
.24
. 9
0
0
0
1.2
1 .0
1 .5
<0
0
1
1
0
0
.6
.7
. 2
-1.5(1.
-1.5 (0.
-2.3(1.
.4
.7
.4
.3
.5
.8
o)h
8)
0)
EXPLANATION:
'Investigator-indicated trophic state:
E = eutrophic 0 = oligotrophic
M = mesotrophic U - ultra
-------
Table 19 (continued). COMPARISON OF PHOSPHORUS LOADINGS DERIVED FROM WATER-
SHED EXPORT COEFFICIENTS WITH LOADINGS PREDICTED BY VOLLENWEIDER1S
MEAN PHOSPHORUS/INFLUENT PHOSPHORUS AND HYDRAULIC RESIDENCE TIME
RELATIONSHIP
Phosphorus loadings calculated using the investigator-indicated mean phosphorus concentrations
and hydraulic loading (Z/T ) data, as applied in Equation 25.
°Phosphorus loadings calculated using the watershed nutrient export coefficients cited in
Table 17. Point sources and any other additional nutrient input sources used in the calcula-
tions were those supplied by the US OECD investigators for their respective water bodies.
Identification number for Figure 17 (see Table 14).
e «
The mean phosphorus concentrations used in Equation 25 were the average summer surface values.
Mean phosphorus concentrations were reported for the arms or sub-basins of these water bodies,
while the watershed land usage patterns were reported for the entire watershed. Because of
mixing of nutrients added to the water body as a whole, as well as morphological and hydro-
logical differences between the sub-basins, it is not possible to calculate phosphorus loadings
based on watershed land use nutrient export coefficients for these water bodies.
rj
&The mean phosphorus concentrations used in Equation 25 were derived from annual August average
values.
Y.
Data in parentheses represent calculations based on data received by these reviewers from
the principal investigator subsequent to the completion of this report. Figure 17 is
based on the original data reported by the investigator and does not reflect the changes
indicated above. However, examination of this subsequent data indicated there were no
significant changes in the overall conclusions concerning the Twin Lakes as a result of
these altered values.
Dash (-) indicates data not available.
-------
-IPX -6X -4X -3X -2X
' ' /
UNDERESTIMATION
VOLLENWEiDER LOAD)SO s3,4
EXPORT COEFFICIENT LOADlNS' 10,8
INVESTIGATOR / INDICATED
TROPHIC/STATE:
• - EUTROPIC
A - MESOTROPHIC
+ IOX
2.0
3.0
PHOSPHORUS LOADINGS CALCULATED VIA WATERSHED
PHOSPHORUS EXPORT COEFFICIENTS
Figure 17.
(g P/mz/yr)
Comparison of Phosphorus Loadings
Derived from Watershed Export Co-
efficients with Loadings Derived
from Vollenweider Mean Phosphorus/
Influent Phosphorus and Hydraulic
Residence Time Relationship
145
-------
within two-fold of the loadings predicted with nutrient export
coefficients Given the different components considered in these
two approaches, a phosphorus loading discrepancy of two-fold or
less between these two methods was considered by these reviewers
to be a reasonably good agreement for the water bodies for which
adequate data were available. The results of Figure 17 and Table
19 will also be discussed in connection with the Vollenweider
loading diagrams presented in subsequent sections of this report,
146
-------
SECTION VII
US OECD EUTROPHICATION STUDY PHOSPHORUS DATA:
AS APPLIED IN INITIAL VOLLENWEIDER PHOSPHORUS LOADING AND MEAN
DEPTH/HYDRAULIC RESIDENCE TIME RELATIONSHIP
With the possible phosphorus loading discrepancies indicated
in the relationships discussed in the previous section (i.e.,
Figures 14-16), it is now appropriate to return to the major
focus of the US OECD eutrophication study and examine the phos-
phorus loading-trophic response relationships in the US OECD
water bodies, as expressed by the Vollenweider phosphorus loading
criteria and other models.
The Vollenweider diagram of total phosphorus loading and
the ratio of mean depth to hydraulic residence time, as original-
ly developed (Vollenweider, 1975a), containing the US OECD water
bodies for the years for which data were available is presented
in Figure 18. This is the phosphorus loading diagram which
serves as the basis of the US EPA's Quality Criteria for Water
(US EPA, 1976a) for determining critical phosphorus loads for US
lakes and impoundments. The pertinent US OECD data are presented
in Table 20. If a data range was reported for a water body, the
mean value was used in all calculations. Data were not available
for all water bodies for all time periods. An example is Dogfish
Lake. Nutrient data were available only for 1972. Consequently,
in Figure 18, only Dogfish Lake - 1972 (Identification Number 10)
is presented. Refer to Table 1M- for identification of any water
bodies and/or time periods not included in a given table or
figure in this report.
Examination of Figure 18 shows good agreement between the
trophic states of the US OECD eutrophication study water bodies,
as indicated by their position on the Vollenweider phosphorus
loading diagram (based on their reported phosphorus loadings and
mean depth/hydraulic residence time characteristics), and the
trophic states indicated by their principal investigators. Only
a few water bodies show anomalies between the predicted and re-
ported trophic states. These anomalies will be discussed shortly.
The small number of US OECD water bodies showing disagreement
between the Vollenweider phosphorus loading diagram-indicated
trophic state associations and the investigator-indicated trophic
states support the validity of the Vollenweider phosphorus load-
147
-------
IV
*-^
N
e
Q.
01
O
Z
Q
O
tn
ir
O O.I
(L
to
O
Q.
0.01
1 ' ' ' ' 1 I 1 1 1 1 1 1 1 1 1 1 1 1 II 1 i (85)l 1 1 1 1 1
I 35 »29 4>
- EUTROPHIC • 128
• 16 w
• 8 •* XX"
m * •' • 5° ^EXCESSIVE
47 l4 *«6 ^^
_ •' *2 54 * * ^^ ^'PERMISSIBLE
~- »I7 • 39», *^ .x--^
I 2^ 3 03£-33 52 ^.-^
^ ^5 ^,^» Af\ Z^l ^^
7 ^ j^^ ^L/ at
-------
Table 20. PHOSPHORUS AND NITROGEN LOADINGS, MEAN DEPTHS (z)
AND HYDRAULIC RESIDENCE TIMES (T ) EOR US OECD
WATER BODIES "'
-P
CO
Water Body
Blackhawk
Brownie
Calhoun
(l)f
(2)
(3)
Trophic
State*
E
E
E
Mean
Depth ,5
(m)b
4
6
10
.9
.8
.6
Hydraulic
Residence
Time ,T
U)
(yr)°
0
2
3
.5
.0
.6
Total Total
Phosphorus Nitrogen
Loadings Loadings
(£ P/m2
2 .1
1
0
/yr)d (RN/m2/yr)e
-2.3 23.4
.18
.86
Came lot -Sherwood
Complex
Canadarago
Cayuga
Cedar
Cox Hollow
Dogfish
(4)
(5)
(6)
(7)
(8)
(10)
Dutch Hollow(ll)
George
Harriet
Isles
(12)
(13)
(14)
Kerr Reservoir
E
E
M
E
E
0
E
0-M
E
E
E-M
Roanoke Arm(16)
Nutbush Arm(17)
Lamb
(IP)
0
3
7
54
6
3
4
3
18
8
2
10
8
4
0.09-0.14
. 7
.1
.8
.0
.8
.7
.3
.2
0
8
3
.6
.6
.3
0 .5-0.7
3
1
8
2
0
0
5
2
.5
.8
.0
.4
.6
.2
.1
. 3
2.4
0
0
0
1.6
0
1
0
0
2
5
0
0
-2.7 34.6
.8 18
.8 14. 3g
.35
-2.1 19.1
.02
.0 10.4
.07 1.8
.71
.03
.2 36.2
.7 2.4
.03
-------
Table 20 (continued). PHOSPHORUS AND NITROGEN LOADINGS, MEAN
DEPTHS (z) AND HYDRAULIC RESIDENCE TIMES (T ) FOR
US OECD WATER BODIES. "*
Water Body
Meander
Mendota
Trophic
State3
(21)
(22)
Michigan (open waters
1971 (23 A f,
1974
p Lower Lake
(j-, Minnetonka
o 1969
1973
Potomac
Upper
Middle
Lower
Redstone
Sallie
Sammamish
Shagawa
(24 A g
(25)
(26)
(28)
(29)
(30)
(31)
(32)
(33)
(34)
0
E
)
B)0
B)0
E
E-+M
U-E
-
-
E
E
M
E
Mean
Depth, z
(m)b
S.O
12
84
84
8.3
8.3
4.8
5.1
7.2
4.3
6.4
18
5.7
Hydraulic
Residence
Time ,T
CM
(yr)c
2 . 7
4.5
30-100
30-100
6.3
6.3
0.04
0.18
0.85
0.7-1.0
1.1-1.8
1.8
0.8
Total Total
Phosphorus Nitrogen
Loadings Loadings
(g P/m2/yr)d (g N/m2/yr)e
0.03
1.2 13
0.14
0.10 1.3
0.5
O.l(0.2)h
85 288
8 32
1.2 2.5
1.4-1.7 18.1
1.5-4.2 2.8-3.0
0.7 13
0.7 7.8
-------
Table 20 (continued). PHOSPHORUS AND NITROGEN LOADINGS, MEAN
DEPTHS (z) AND HYDRAULIC RESIDENCE TIMES (T ) FOR
US OECD WATER BODIES. w
Water Body
Stewart
Tahoe
East Twin
197?
1973
1974
West Twin
1972
1973
197it
Twin Valley
Virginia
Waldo
Washington
1957
1961)
1971
1974
(35)
(36)
(39)
(40)
(41)
(42)
(43)
(44)
(46)
(47)
(48)
(49)
(50)
(51)
(52)
Trophic
State3
E
U-0
E
E
E
E
E
E
E
E
U-0
E
E
M
M
Mean
Depth , z
< ib
(m)
1
.9
313
5
5
5
4
4
4
3
1
.0
.0
.0
.34
.34
.34
. 0
.7
36
33
33
33
33
Hydraulic
Residence
Time ,T
M
r-
(yr)C
0
.1
700
0
0
0
1
1
1
0 .4
0.9
.8
.9
.5
.6
.8
.0
-0 .5
-2 .8
21
2
2
2
2
.4
.4
.4
.4
Total
Phosphorus
Loadings
(g P/m
4.8
0
0
0
0
0
0
0
1.7
1.2
0
1
2
0
0
2/yr)d (g
-8.
.05
.7
.5
.7
.4
. 3
. 3
-2 .
-1.
0
V.
(0.7)h
(0.5)
(0.8)
V,
(0.4)h
(0.2)
(0.3)
0
5
.017
.2
.3
.43
.47
Total
Nitrogen
Loadings
N/m
73
0
31
19
16
15
17
18
0
19
7
4
4
2/yr)e
.6
.52
.48
.38
-
g
g
-
.4
.3
.33
.2
.8
.6
.4
-------
Table 70 (continued). PHOSPHORUS AND NITROGEN LOADINGS, MEAN
DEPTHS (z) AND HYDRAULIC RESIDENCE TIMES (T ) FOR
US OECD WATER BODIES. W
en
Trophic
Water Body State3
Weir (53) M
Wingra (54) E
EXPLANATION:
Mean
Depth, z
(m)b
6. 3
2.4
Hydraulic
Residence
Time ,T
cu
(yr)c
4 .2
O.U
Total
Phosphorus
Loadings
(g P/m2/yr)d
0.14
0.9
Total
Nitrogen
Loadings
(g •N/m2/yr)e
2.6
5.14
M = mesotrophic
0 = oligotrophic
U - ultra
Mean depth (?) = water body volume (m )/water body surface area (m ).
c 3 3
Hydraulic residence time (f ) = water body vo]ume (m )/annual inflow volume (m /yr).
Based on investigator's estimates.
eBased on investigator's estimates. Total nitrogen loading consists of inorganic
nitrogen (i.e. , NH^+NO^+NO^-N) + organic nitrogen, unless otherwise indicated.
f 4 J /
Identification number for Figures 18, 19 and 21 (See Table 14)
g
"Does not include organic nitrogen.
1 Data in parentheses represents data received by these reviewers subsequent to the completion
of this report. Figures 18 and 19 are based on the original data supplied by the investi-
gators and do not reflect these revised values. Examination of the data indicated no
significant changes in the overall conclusions concerning these water bodies.
Dash (-) indicates data not available.
-------
ing relationship in establishing trophic state associations and
critical phosphorus loading levels for US lakes and impoundments
(i.e., a level which could produce problem algal blooms in water
bodies).
For the purposes of this section of the report, agreement
or lack of agreement with the Vollenweider relationship is based
on whether the investigator-indicated trophic state is appropriate,
compared with the trophic conditions that Vollenweider and other
US OECD investigators have reported for other water bodies with
similar phosphorus loadings and hydrologic and morphologic
characteristics, (i.e., does a lake designated as eutrophic by
the US OECD investigator hold a position on the Vollenweider load-
ing curve similar to those held by other eutrophic lakes?).
No attempt is being made at this time to further refine this re-
lationship. If it is completely valid, then lakes with the greater
displacement from the permissible phosphorus loading line should
be more highly eutrophic. In general, this seems to be the case
for many of the US OECD eutrophication study water bodies. This
point will be discussed further in a subsequent section of this
report.
AS APPLIED IN MODIFIED VOLLENWEIDER PHOSPHORUS LOADING AND
MEAN DEPTH/HYDRAULIC RESIDENCE TIME RELATIONSHIP
Vollenweider's modified phosphorus loading and mean
depth/hydraulic residence time diagram is presented with the US
OECD eutrophication study data in Figure 19. As mentioned in an
earlier section, this modified Vollenweider phosphorus loading
diagram is identical to his original phosphorus loading and mean
depth/hydraulic residence time diagram (Figure 18) except that the
boundary conditions have been altered. According to Vollenweider
(1975a), these modified boundary conditions are more indicative
of the true phosphorus assimilative capacity of water bodies
than were his original boundary conditions (Figure 18). These
altered permissible and excessive loading lines (Figure 19) make
a difference in the trophic zone designation of the loading
diagram, lowering the permissible and excessive phosphorus load-
ing limits for some range of Z/TW values and raising them for other
values of Z/TW. The original and modified Vollenweider phosphorus
load and mean depth/hydraulic residence time loading diagrams are
superimposed in Figure 20 to illustrate the differences in
trophic zone designations.
Examination of Figure 20 shows the effect of the modified
boundary conditions is to indicate a lower apparent phosphorus
assimilative capacity (i.e., a lower permissible and excessive
loading line) on the modified loading diagram (Figure 19) for
water bodies with a Z/T^ value of between approximately 2 to 50,
relative to the original Vollenweider phosphorus loading diagram
(Figure 18). Below a Z/TW value of 2, the phosphorus assimila-
tive capacity becomes constant in the modified Vollenweider phos-
phorus loading diagram. The excessive and permissible loading
boundary conditions increase in the modified Vollenweider phos-
phorus loading diagram above a z/T^value of about 50. This
153
-------
I (J pww. j_ _—--y| ..-_..-. yr--j- | f™^^^™"' V \ 1 1 IT I M |T«——^MM^^Yn^^^^^HB^HH^Tw^*^l|—p
EUTROPHIC * " • ^/EXCESSIVE -
a.
31 l
o
z
o
o
o o.i
o
X
CL
O.OI
>50 / /PERMISSIBLE
47 22 » 30 49
" * *
43
/
24-A
/ INVESTIGATOR-INDICATED -
^y'' TROPHIC STATE '.
3-B ^^ •-EUTROPHIC
£>-•** A -MESOTROPHIC
O24-B O-OLIGOTROPHIC
^ 012
O
36
I9oo2,
1§ 48 OLIGOTROPHIC
i i i i i i 111 i i i i i 11 ii i i iii
O.I I 10 IOO IOOO
MEAN DEPTH Z/HYDRAULIC RESIDENCE TIME , Tw
( m/yr )
Figure 19. US OECD Data Applied to Modified Vollenweider
Phosphorus Loading and Mean Depth/Hydraulic
Residence Time Relationship
154
-------
10
(M
E
* .
en '
O
Z
O
o
_i
to
or
OQ.I
OL
O
X
Q.
.01
III I 1 | I I II II I
EXCESSIVE
/
PERMISSIBLE
EXCESSIVE
.^
• ^PERMISSIBLE
BOUNDARY CONDITION
IN INITIAL DIAGRAM.
(Figure 18)
BOUNDARY CONDITION"
IN MODIFIED DIAGRAMl
(Figure 19)
ml
O.I
I
10
100
1000
MEAN DEPTH. Z/HYDRAULIC RESIDENCE TIME,
( m/yr )
Figure 20.
Comparison of Permissible and Excessive Loading
Lines in Initial and Modified Vol1enweider
Phosphorus Loading Diagram.
155
-------
increase in phosphorus loading tolerance illustrates the effects
of either a great depth or a very rapid hydraulic flushing time
on increasing the relative phosphorus assimilative capacity of a
water body. A great depth in a water body usually indicates a
large volume of water, with a likely high degree of dilution of
input nutrients and reduced phosphorus return from the sediments,
and gives the water body a high phosphorus assimilative capacity.
Conversely, a very rapid flushing rate usually indicates that the
nutrients are being washed out of the water body approximately as
rapidly as they are being added to it, giving the water body a
higher phosphorus assimilative capacity than water bodies with a
lower Z/T value.
w
Figure 19 represents one of the major thrusts of the US
OECD eutrophication study. It demonstrates the relationship
between the phosphorus loadings and trophic conditions of the US
OECD water bodies, as modified by their hydraulic loading, qs.
This is based on their associations on the loading diagram with
water bodies of similar Z/T^ (=qs) characteristics and phosphorus
loads. It also establishes the permissible and excessive phos-
phorus loading levels for these water bodies. Figure 19 indicates
that only Lakes Cayuga (6), Lower Minnetonka (26), and Sammamish
(33) have predicted trophic states which are in disagreement with
the trophic state reported by the respective US OECD investigator
(Appendix II). The results in Figure 19 also provide an indirect
check on the effectiveness of the independent methods (i.e.,
Equation 26 and watershed land use nutrient export coefficients)
used by these reviewers to check on the reasonableness of the
reported US OECD water body phosphorus loadings. The .anomalies
seen in both the investigator-indicated and phosphorus loading
diagram-derived trophic states in Figure 19, and those seen in
Figures 14 and 15 as related to the results in Figure 19, are dis-
cussed on a water body-by-water body basis in the following sections
Based on the agreement of the investigator-indicated trophic
states of the US OECD water bodies with the results indicated on
the Vollenweider phosphorus loading diagram (Figure 19), and on
the results of the methods used to check on the reasonableness
of the reported phosphorus loadings (Figures 14 and 15), the
investigator-indicated phosphorus loadings and trophic states of
a majority of the US OECD water bodies appear to be reasonable.
In general, they are indicative of the present trophic condi-
tions of these water bodies. For the purposes of this report
these reviewers defined a reasonable phosphorus loading to a US
OECD water body as one which is within a factor of two (i.e., +_
two-fold) above or below the phosphorus loadings predicted in
Figures 14 and 15. There was no technical basis for choosing a
156
-------
factor of +_ two to define a reliable phosphorus loading. A
different value may be as appropriate. However, Vollenweider
(1977) has indicated that the standard deviation of the relative
error, considering 1/(1 + /r^) as the reference value, corresponds
very well with the +_ 2x assumption. A lack of agreement between
the calculated and reported phosphorus loads in Figures 14 and
15 could be due either to errors on the part of the investigator
in estimating nutrient loads for the lake, or to different phos-
phorus transport and cycling behavior in the lake's watershed and
in the lake itself than is typically found for most other lakes.
It should be noted that the implementation of these approaches
(Figures 14 and 15) to check the reported US OECD data has
caused some US OECD eutrophication study investigators to crit-
ically reexamine their nutrient load estimates, resulting in
their finding errors in their original loading estimates. The
methods presented in this report have been used by these reviewers to
correct for these types of errors.
The failure of a particular lake or impoundment to fit the
Vollenweider nutrient load-trophic state relationship may also
be due to several other factors in addition to errors in phos-
phorus loading estimates. Particularly important would be errors
in estimating hydraulic residence times, as well as personal
biases of the investigators in assigning a particular trophic
state classification to their water body.
It is very important to also note that a lack of fit of a
particular lake to the Vollenweider total phosphorus load and
mean depth/hydraulic residence time trophic state relationship does
not mean that there have been errors on the part of the investi-
gator in estimating any of these parameters. It is quite prob-
able that even though Vollenweider and this study have found good
agreement of this relationship for a wide variety of lakes and
impoundments, there will be some water bodies which do not fit this
relationship. This non-fitting group of lakes and impoundments
would be of particular interest and significance since they would
demonstrate apparently unusual phosphorus utilization. From the
point of view of water quality management, it is important to
clearly identify water bodies of this type so that appropriate
modifications of the Vollenweider nutrient loading relationship
can be made to any water quality standards that are developed by
water pollution control agencies based on this relationship for
these water bodies. It is important to note that the Vollenweider
loading diagram is a log-log relationship. Therefore, small errors
in estimating any of the parameters will not change the position of
a particular water body on the diagram to any large extent. This
also indicates that a large change in phosphorus loading to a
water body is necessary before a significant change in trophic
state can be expected.
For example, consider the possibility that the investigator-
indicated phosphorus loadings to Dutch Hollow (11) were overestimated
157
-------
three-fold in Figure 19. If one corrected the reported phos-
phorus loading for this error, Dutch Hollow would still be in the
eutrophic zone of the Vollenweider loading diagram. Using the
same reasoning, the phosphorus loadings to Dogfish (10) could be
increased four-fold, and yet Dogfish would remain in the oligo-
trophic zone of the Vollenweider phosphorus loading diagram.
Therefore, these reviewers examined the investigator-indicated
phosphorus loadings and trophic states for the possibility of an
error if the reported and predicted trophic states of a given water
body were not in agreement in Figure 19 and its reported and pre-
dicted phosphorus loadings were not in agreement in Figures 14-
and 15.
There were only a few water bodies which showed a disagreement
in one or more parameters. Lake Cayuga (6) and Sammamish (33)
plot with water bodies in the eutrophic zone of the Vollenweider
phosphorus loading diagram (Figure 19). Yet these two water bodies
were classified as mesotrophic by Oglesby (1975) and Welch et al.
(1975), respectively, on the basis of the structure and pro-
ductivity of their biological communities. These investigators
felt those factors were more indicative of the true trophic states
of these two water bodies than were their positions on the Vollen-
weider phosphorus loading diagram. If the investigator-indicated
trophic states of Lakes Cayuga and Sammamish are accurate, then
their positions on the Vollenweider phosphorus loading diagram
(Figure 19) indicate that the Vollenweider relationship between
phosphorus loadings and Z/T^ characteristics does not hold for
Lakes Cayuga and Sammamish, or that the phosphorus loadings in-
dicated by Oglesby (1975) and Welch et_ al. (1975), respectively,
for these two water bodies may have been overestimated.
It should be mentioned here that a water body does not abrupt-
ly change in character as soon as it crosses one of the boundary
lines (i.e., permissible or excessive) in the Vollenweider phos-
phorus loading diagram. These boundary lines were established
on the basis of a subjective determination between nutrient con-
centration and water quality. As mentioned in an earlier section
of this report, it would generally be expected that those water
bodies, with a given mean depth/hydraulic residence time relation-
ship, which have the greater vertical displacement under the per-
missible boundary line on the Vollenweider phosphorus loading dia-
gram (Figure 19) would have the best water quality. Conversely,
those water bodies of the greater vertical displacement above the
permissible loading line would have the poorer water quality.
There is a continual gradient of water quality between these two
extremes, with the permissible boundary line defining a general
water quality condition acceptable to the population.
The possibility of overestimation of the reported phosphorus
loadings for Cayuga (6) and Sammamish (33) is consistent with the
results of Figure 14 for Lake Cayuga, and with Figure 15 for Lake
Sammamish. The results of Figure 14 indicate that the reported
phosphorus loadings for Lake Cayuga may have been overestimated
158
-------
almost two-fold. Likewise, the results of Figure 15 indicate the
reported phosphorus loadings for Lake Sammamish may also have been
slightly overestimated. A reduction of the phosphorus loading
estimates for these two water bodies to the extent indicated in
Figures 14 and 15 would place them closer to the mesotrophic zone
of the Vollenweider loading diagram (Figure 19), more in agree-
ment with their investigator-indicated trophic states.
One other factor that should be considered in examination of
the US OECD investigator-indicated trophic states for these two
water bodies is that they were established by interpretation of
classical response parameters, specifically their biological
characteristics. Such interpretation is subjective in nature.
When, for example, does a lake change in character from mesotrophic
to eutrophic? Thus, the lack of agreement between the predicted
and reported trophic states for these two water bodies could be
attributed to a small error in phosphorus loading estimates, Z/T^
values or the still subjective nature of trophic state classifi-
cation of water bodies. Oglesby (1977) has also indicated
that, in the case of Lake Cayuga, about 75 percent of the tri-
butary total phosphorus load is adsorbed to soil particles in
the tributary waters. Only about 5 percent of this adsorbed
phosphorus becomes desorbable in phosphorus free aqueous solution.
Thus, according to Oglesby, a significant portion of the tri-
butary phosphorus load becomes unavailable for phytoplankton
assimilation. This interpretation is consistent with Lake
Cayuga's lower biological productivity in spite of a phosphorus
load which places it in the eutrophic zone of the Vollenweider
diagram.
Lower Lake Minnetonka-1973 (26) plots just inside the oligo-
trophic zone on the Vollenweider phosphorus loading diagram
(Figure 19). However, Megard (1975) classified Lower Lake Minne-
tonka as eutrophic, changing to mesotrophic, suggesting a phosphorus
loading underestimation for this water body. Sewage effluents,
which was approximately 80 percent of the total phosphorus input,
were diverted from Lower Lake Minnetonka in late 1971-early 1972.
Yet, the eutrophic condition reported for this water body was in-
dicative of Lower Lake Minnetonka in 1973. This situation is
explainable by the fact that while the phosphorus loadings to
this water body have decreased approximately 80 percent, the
water body has not yet had sufficient time to shift to a new equi-
librium phosphorus concentration.
Megard (1975) has indicated that Lower Lake Minnetonka appears
to be slowly shifting to a mesotrophic condition, based on its
mean chlorophyll concentrations and Secchi depth measurements.
It is possible, unless other unusual circumstances are present,
the trophic state indicated by its 1973 position in the oligo-
trophic-early mesotrophic zone of the Vollenweider phosphorus
loading diagram (Figure 19) will be indicative of its trophic
state when it has reached a new phosphorus equilibrium condition.
159
-------
It is also possible that the reported 1973 phosphorus
loadings for Lower Lake Minnetonka may actually have been under-
estimated, (note: This predicted underestimation was subse-
quently substantiated by Megard (1977).) Such a possibility is
suggested in Figure 14 based on the reported mean phosphorus
concentrations for this water body. One of the necessary para-
meters needed for Equation 26, which serves as the basis for
Figure 14, is an accurate knowledge of the mean phosphorus con-
centration in the water body. If the current mean phosphorus
concentration in Lower Lake Minnetonka is in a non-equilibrium
condition, with respect to its phosphorus loading, because of
its recent remedial treatment, the mean phosphorus concentration
in Equation 26 is not justified. Its mean phosphorus concen-
tration, and any predicted phosphorus loading based on its
mean phosphorus concentration, will change with time until a new
steady state condition is reached in Lower Lake Minnetonka.
No watershed land usage data was available for Lower Lake
Minnetonka. Consequently, Figure 15 could not be used to check
on the reasonableness of its 1973 phosphorus loading estimate.
Both Lower Lake Minnetonka and Lake Washington have under-
gone partial or total sewage diversion from the watershed basin.
In the past, it has been common practice to relate the response of
a water body which has undergone nutrient input reduction to the
hydraulic residence time, or filling time (i.e., water body volume
(nr)/annual inflow volume (m^/yr)) of the water body. However, in
the case of phosphorus, such an approach does not take into con-
sideration the aqueous chemistry of phosphorus in its role of
limiting aquatic plant growth. It is more realistic to relate the
rate of recovery of a water body, following nutrient input re-
duction, to the chemical residence time of the critical aquatic
plant limiting nutrient for that water body, rather than to its
hydraulic residence time. This approach in evaluating the re-
covery of Lake Washington and Lower Lake Minnetonka will be dis-
cussed in a following section.
AS APPLIED IN THE PHOSPHORUS RESIDENCE TIME MODEL
It is generally accepted that steady state conditions in a
water body are approached exponentially in accordance with the
hydraulic residence time of the water body. Assuming a lake is a
completely mixed reactor subjected to continual and constant
chemical influx, which only occurs through the^outlet, the dynamics
of a conservative substance can be described as:
V dc/dt = Qci - Qc (27)
160
-------
3
where V = lake volume (L ),
3 -1
Q = volumetric flow rate (L T )
-3
c. = influent concentration of substance c (ML ), and
_ 3
c = lake concentration of substance c (ML ).
Integrating and applying the boundary condition that c=c at t = o,
,r
c = c. + (c -c.)e~T/ W (28)
i o i
where T = V/Q = hydraulic residence time.
This latter equation shows that after a change (increase or de-
crease) in the incoming flux of substance c, steady state condi-
tions are approached exponentially in accordance with the basin's
hydraulic residence time. According to Rainey (1967) and Vollen-
weider (1969), three hydraulic residence times are required to
reach 95 percent of the new steady state concentrations of sub-
stance c, following a change in the rate of supply of that sub-
stance .
However, in the case of phosphorus this approach does not
consider the aqueous chemistry of phosphorus as it relates to
limiting aquatic plant growth. Phosphorus is a non-conservative
substance which undergoes transformations in natural waters.
Accordingly, the recovery of a water body to remedial phosphorus
treatment, whether it involves sewage treatment or diversion, is
more accurately related to the phosphorus chemical residence time
than to the hydraulic residence time. Once the residence time of
the aquatic plant limiting nutrient (phosphorus or nitrogen) to
a given water body is known, the rate of the water body's response
to remedial treatment can be predicted if an adequate model is
available.
One of the frequently-asked questions in eutrophication
control programs is the rate at which the lake will come to a
new equilibrium condition of water quality after altering the
nutrient input. There are several deficiencies in Rainey's
approach when it is applied to non-conservative substances, such
as phosphorus. First, the steady-state lake concentration of phos-
phorus is assumed identical to the influent concentration. In
reality, annual mean phosphorus concentrations are often lower
than the annual input concentration of phosphorus. Second,
the lake losses are assumed to occur only through the outlet.
In fact, the major loss of phosphorus in lakes usually occurs as
a result of sedimentation, not outflow discharge.
161
-------
Accordingly, the initial equation (Equation 27) can be mod-
ified to account for these deficiencies. To account for internal
losses, the expression for phosphorus (P) dynamics becomes
V dP/dt = QP. - QP - kPV
(29)
where K = internal loss rate constant, T
An assumption in this model is that the sedimentation loss is
directly proportional to the mean lake phosphorus content , rather
than to the phosphorus supply. One other factor that must be con-
sidered is that in stratified lakes, different water layers may
contain different amounts of phosphorus due to biological, chem-
ical and/or physical processes. An example is the summer growth
period where the phosphorus concentration may only be a fraction of
the whole lake concentration due to algal uptake. Thus, the out-
wash concentrations may be different during the summer time than
during periods of lesser productivity. Accordingly, the above
equation may be modified as:
V dP/dt = QP. - Q oc p _
(30)
where
dimensionless proportionality factor relat-
ing annual mean outwash or surface water
phosphorus concentration to the mean annual
concentration over the whole lake.
Sonzogni et al . (1976) have modified this model to predict
changes in the phosphorus concentration as a response to nutrient
input reductions based on the concept of a phosphorus residence
time in natural waters. Equation 30 can be rearranged as:
dP + ((Q
+ kV)/V) Pdt = (Q/V) Pidt (31)
Since V/Q = T , Equation 31 can be simplified as
to
dP + (1/R ) Pdt = (1/T ,) P.dt (32)
p to i
where R = V/(Q ^ + kV) = phosphorus residence
^ time in lake
If P = P at t = 0, Equation 32 can be integrated to produce
P = P.(R /T )-(P.(R /T )-Pn) e t/Rp
i p to iptoO ^
(33)
The steady state phosphorus concentration is not equal to the in-
put phosphorus concentration, but rather differs by the ratio of
the phosphorus and hydraulic residence times, as
162
-------
p * = pi(w (34>
Thus, the time dependent solution to Equation 33 becomes
(P(t)-P
-------
Table 21. PHOSPHORUS AND NITROGEN RESIDENCE TIMES OF US OECD WATER BODIES
Phosphorus
Mass in
Trophic Water Body
Water Body State* (mg P)
Blackhawk
Brownie
Calhoun
Came ] ot-Sherwood
Canadarago
Cayuga
Cedar
Cox Hollow
Dogfish
Dutch Hollow
George
Harriet
Is]es
Kerr Reservoir
Roanoke Arm
Nutbush Arm
Lamb
Meander
E
E
E
E
E
M
E
E
0
E
0-M
E
E
E-M
_
_
0
0
3
1
2
.71xl08
_
.91xl09
.94xl08
Q
2 .34-2.93x10"
1
2
1
1
6
1
7
1
3
1
1
1
1 1
.84x10
.32xl08
.19xl08
.IGxlO7
.63xl08
.68xl010
.64xl08
.25xl08
-| r\
.71xl010
.23xl010
.92xl07
.62xl07
Phosphorus
Phosphorus Residence
Loading , Time, R
(mg P/yr)D (yr)e p
1.
8
1
6.
6
1
2
6.
5
8.
7
9
8
G
3
1
1
9-2. IxlO9
.59xl07
.46xl09
6-7.5xl09
Q
.0x10
1 1
.36x10
.41xl08
3-8. IxlO8
.8xl06
l-8.6x!08
.7xl09
.94xl08
.53xl08
T -|
.24x10
.5x]010
.21xl07
.OSxlO7
0
1
0
0
1
1
0
2
0
2
0
0
0
0
1
1
.2
_
.3
.04
.4
.4
.0
.2
.0
.8
.2
.8
.1
.06
.4
.6
.5
Inorganic Inorganic
; Hydraulic Nitrogen Inorganic Nitrogen
Residence Mass in Nitrogen Residence
Time , T
(yr)<3 "
0.
2.
3.
0 .09-0
0.
8.
3 .
0.5-0
3 .
1.
8
2.
0 .
0 .
5.
2.
2.
5
0
6
.14
6
6
3
.7
5
8
4
6
2
1
3
7
Water Body Loading Time. R
J (mg N)e (mg N/yr)e (yr)f n
3 .
< 2 .
< 9.
6 .
2.22
3.4
< 2.
8 .
4 .
1.
9 .
< 6.
< 6.
3 .
9.
8.
8.
40xl09
73xl07
91xl08
97xl09
10 11
-2.57x10 1.37x10 0.2
12 12
-4.68x10 2.46x10 1.6
31xl08
89xl08
52xl08
IxlO9
9xl010
78xl08
24xlO?
1 -i
46x10
02xl010
16xl08
IxlO8
-------
Table 21 (continued). PHOSPHORUS AND NITROGEN RESIDENCE TIKES OF US OECD WATER BODIES
cn
en
Phosphorus
Mass in
Trophic Water Body
Water Body State3
Mendota
Michigan (Open
Water-1974)
Lower Lake
Mirine tonka
1969
1973
Potomac Estuary
Upper Level
Middle Reach
Lower Reach
Redstone
Sallie
Sammamish
Shagawa
Stewart
E
0
E
E-»M
-
_
_
E
E
M
E
E
(mg P)
7.02xlOi0
1 3
6 .33x10
1.30xl010
1.09xl010
i n
8.21x10,"
-3.28x10
1.07x10^
-8.03X1011
l.SlxlO11
-3.02X1011
7.52xl08
1.19xl010
l.OSxlO10
3.15xl09
2.85xl06
Phosphorus
Loading
(mg P/yr)
4 .65x10
5.8x10
1.31x10
2 .62x10
4 .84x10
1.68x10
8 .4x10
10
12
10
9
1 o
-L i
12
11
3 .6-4 .2xl09
7.95x10
-2.23x10
1.4x10
6.44x10
1.2-2x10
9
i n
J-U
10
9
8
Phosphorus
Residence
Time, R
Inorganic Inorganic
Hydraulic Nitrogen Inorganic Nitrogen
Residence Mass in Nitrogen Residence
Time. T Water Body Loading Time. R
/ \ /•* P / \/1LO
(yr)c (yr)a
1
1
4
0
0
0
0
0
0
0
0
. 5
11
.0
.2 (7.0) ^
.04
.2
.3
.2
.8
.8
.5
.02
4
30-
6
6
0
0
0
0 .7
1.1
1
0
0
.5
100
.38
.38
.04
.18
.85
-1.0
-1.8
.8
.8
.08
3
8 .
4
-8
1
-3
2
-7
5
1
6
8
7
(mg N)e li>g«/yrJ=(>
.OxlO11 3.48X1011
(NHj+NOJ-N)
1 U 1 1
28x10 7.54x10
_ _
_
i -i
.92X10,,
.76X1011
.60x10:4
.53X1011
.52xlo}}
.56.10
.97xl09
.49xl010
.48xl010 2.6X1011
.39xl09
.41xl07
\ L
0.9
11
_
_
-
_
_
_
0.2
.
_
-------
Table 21 (continued). PHOSPHORUS AND NITROGEN RESIDENCE TIMES OF US OECD WATER BODIES
Phosphorus
Mass in
Trophic Water Body
Water Body
Tahoe
East Twin
1972
1973
1974
West Twin
1972
1973
M 1974
CD
cn Twin Valley
Virginia
Waldo
Washington
1957
1964
1971
1974
Weir
Wi ngra
Stated
U-0
E
E
E
E
E
E
E
E
U-0
E
E
M
M
M
E
(mg P)
4 .
1.
1.
1.
1.
1.
1.
1.
2.
4 .
6.
1.
5.
1.
2.
70X1011
OSxlO8
OSxlO8
OSxlO8
77xl08
62xl08
47xl08
0
51xlOB
eoxio7
86xl091
97xl010
92X1011
23X1010
_
21xl010
35xl08
Phosphorus
Loading .
(mg P/yr)D
2 .
1.
1.
1.
1.
1.
1.
1.06
2.07
4 ,
1.
2 .
3 .
4 .
3.
1.
SOxlO10
89xl08
35xl08
89xl08
36xl08
02xl08
02xl08
_
-1 . 25x10
-2.66xl08
59X108
06xlOU
02X1011
76xl010
13X1010
29xl09
2Gxl09
Phosphorus
Residence
Time, R
liydraul ic
Residence
Time, T
(yr)c P (yr)d •»
19
0.
0 .
0.
1.
1.
1.
0.
0.
10
0 .
1.
1.
„
3.
0.
6
8
6
3
6
4
1
1
6 (0.7)3
0 (1.0)
4 (1.3)
(1.4)
7 (24.9)
2
700
0 .8
0.9
0.5
1.6
1.8
1.0
0.4-0.5
0.9-2.8h
21
2 .4
2.4
2 .4
2.4
4.2
0.4
Inorganic Inorganic
Nitrogen Inorganic Nitrogen
Mass in Nitrogen Residence
Water Body Loadinr Time, R^
(mg N)e
3 .13xl012
7.83xl08
1.13xl09
-
1.17xl09
1.22xl09
_
Q
8.58xlOB
6.12xl07
9.72xl091
3.48xlOU
6 .97X1011
5 .23X1011
„
1.06xl010
1.04xl09
(mg N/yr)c (
_
8 .48xl09
5.21xl09
_
5.44X109
S.lOxlO9
_
_
_
2.73X1011
5.65X1011
5.60X1011
_
_
7.20xl09
_
0.1
0.2
-
0.2
0.2
_
-
_
-
1.3 (1.1)
1.2 (0.3)
0.9 (0.3)
- (0.5
- (0.2)
0.1
-------
Table 21 (continued). PHOSPHORUS AND NITROGEN RESIDENCE TIMES OF US OECD WATER BODIES
Phosphorus
Mass in
Trophic Water Body
Water Body State3 (mg P),
EXPLANATION:
a ...
Phosphorus
Loading
(mg P/yr)
Phosphorus
Residence
Time, R
(yr)c p
Inorganic
Hydraulic Nitrogen Inorganic
Residence Mass in Nitrogen
Time, T Water Body Loading
(yr)d u (mg N) (mg N/yr)e
Inorganic
Nitrogen
Residence
Time . R
(yr)f n
= water body volume (m )/annual inflow volume (m /yr).
E = eutrophic, M = mesotrophic, 0 = oligotrophic , U = ultra
Based on investigator's estimates.
°Phosphorus residence time, R = annual mean total phosphorus content (mg)/annual total
phosphorus input (mg/yr).
^Hydraulic residence time,
eBased on investigator's estimates; includes NH^ + N03 + NQ^ as N, unless otherwise indicated.
Inorganic residence time, R = annual mean inorganic nitrogen content (mg)Xannual inorganic
nitrogen input (mg/yr).
"Hydraulic residence time of whole lake,
Possible error in hydraulic residence time.
Mean August value.
Data in parentheses represents data received by these reviewers from the principal investigator
subsequent to completion of this report. Examination of this data indicated no significant
changes in the overall conclusions concerning these water bodies.
l)rir,h (-) indicates data riot available.
-------
Lake Michigan has a hydraulic residence time ranging from
30-100 years (Piwoni et al., 1976). If it is assumed that phos-
phorus behaves as a con'servative element in Lake Michigan it
should require approximately 100-300 years for Lake Michigan to
reach a new phosphorus equilibrium state following reduction of
its phosphorus loading. However, the phosphorus residence time,
based on the US OECD data, is approximately 10 years. Thus, the
phosphorus residence time model of Sonzogni et al. (1976) predicts
that it would only take approximately 30-35 years to achieve 95
percent of the expected change in the phosphorus content in Lake
Michigan following a reduction in its phosphorus loading.
Megard (1977) has indicated that the quantity of phosphorus
in Lower Lake Minnetonka was just beginning to move toward a new
equilibrium condition in 1973 because the phosphorus load was re-
duced in 1971-1972, following sewage diversion from the water body.
He estimated, on the basis of an adjusted phosphorus residence
time (see below) that a new phosphorus equilibrium would not be
reached until 1979, approximately seven years after diversion,
(Megard, 1975) as compared with the 4.2 years indicated in Table
21. Prior to the sewage diversion, the phosphorus residence time
was calculated to be 1.1 years, as compared to one year in Table
21. However, Megard (1977) has indicated that the predicted mean
phosphorus concentration at the new equilibrium, based on a
1.1 year residence time, would only be about 14 yg/1, atypical of
other lakes of the region. Consequently, he obtained a more con-
servative estimate of 26 yg P/l at a new equilibrium by adjusting
the new phosphorus residence time upward from 1.1 to 2.0 years.
However, Megard (1977) has also noted that the 1.1 year
phosphorus residence time in Lower Lake Minnetonka is based on
extensive data and should be considered an accurate estimate.
Since the post diversion phosphorus load is an estimate of residual
influx from, non-point sources, it is necessarily more tenuous than
the prediversion estimate (Megard, 1977). Consequently, Megard
suggests the post diversion phosphorus load estimate might be
adjusted up by a factor of 1.8 (i.e., the factor used to adjust
the residence time) to produce a post diversion loading of 180
mg P/m /yr, as compared to the 100 mg P/m /yr reported originally.
Adjusting the load by this 1.8 factor produces the same 26 yg P/l
mean concentration, at the new equilibrium, as is obtained by
increasing the phosphorus residence time by the -same factor
(Megard, 1975). That is, the computed rate of response would
still be consistent with the observed response during the first-
two years after diversion.
Lake Weir has a calculated phosphorus residence time of
3.7 years versus a reported value of 24.9 years (Table 21).
Messer (1977) has indicated that, in addition to the mean depth,
the flushing rate, or hydraulic residence time, is the princi-
pal reason for the inverse relationship between critical phos-
168
-------
phorus load and hydraulic load. According to Messer, while
this may be true for northern temperate drainage lakes which are
ice-covered during part of the year, Lake Weir is a sub-tropical
seepage lake located in Florida. While temperate lakes may
lose 10 percent of their hydraulic load through evaporation, Lake
Weir appears to lose about 83 percent of its hydraulic load
due to evaporation (Messer, 1977). This heavy evaporation loss
is not flushing phosphorus from the lake. Consequently, Messer
suggests using the hydraulic flushing rate, exclusive of
evaporation, as an estimate of the "effective flushing rate."
For Lake Weir, the hydraulic residence time, exclusive of evapora-
tion, was calculated to be about 24.9 years and indicates the
increased sensitivity of Lake Weir to phosphorus inputs, relative
to non-seepage water bodies.
Lake Washington provides an example of a lake which has
responded to a decreased nutrient flux. Table 21 shows that,
based on its hydraulic residence time, Lake Washington would
require about seven to eight years to reach a new phosphorus
equilibrium condition. However, the response of the lake to
nutrient reduction has been both prompt and sensitive (Edmondson
1970b, 1972). The lake was considered highly eutrophic in 1964.
Yet, by 1971, following completion of the sewage diversion pro-
ject in the late 1960's, the lake was re-classified as rneso-
trophic by Edmondson (1969, 1970b). The phosphorus residence
time was calculated as 0.5 years in Table 21. Consequently,
one would expect a 95 percent recovery of the lake in one to
two years following the sewage diversion. This situation was
in fact seen in Lake Washington following completion of sewage
diversion in the late 1960's (Edmondson, 1970b; Sonzogni, et al.,
1976).
Megard (1971) compared the actual rate at which the phos-
phorus concentration in Lake Washington decreased, following
sewage diversion, with the phosphorus concentration predicted
from the phosphorus residence time model. He found the observed
rates of decrease paralleled the predicted rates, and the
measured phosphorus concentrations were similar to the predicted
phosphorus concentrations. Based on these results, Lake Washing-
ton provides a successful test of the phosphorus residence time
model as an approach to assessing the rate of recovery of a water
body following phosphorus input reduction.
AS APPLIED IN VOLLENWEIDER EQUATION FOR CRITICAL PHOSPHORUS
LOADING
In addition to his phosphorus loading diagrams, Vollenweider
(1976a) had derived several equations for calculating the critical
phosphorus loading levels and expected trophic states for lakes
169
-------
and impoundments. As indicated earlier, Equation 19 expresses
a generalized relationship which can be used to determine critical
phosphorus loads for lakes and impoundments, based on their mean
depth and hydraulic residence time characteristics.
According to Vollenweider (1976a), assuming steady state con-
ditions , water bodies which receive phosphorus loadings below the
critical level defined by Equation 19 would be expected to be in
an oligotrophic condition. Conversely, water bodies whose phos-
phorus loadings were more than twice the critical loading level
would be expected to be eutrophic. A water body with phosphorus
loadings between these two limits would be mesotrophic.
Equation 19 was used by these reviewers to check the reported
phosphorus loading levels and trophic states for the US OECD water
bodies. The pertinent data for the US OECD water bodies is pre-
sented in Table 22. If a data range was reported for a water
body, the mean value was used in all calculations. The last
column in Table 22 indicates the approximate factor by which the
investigator-indicated phosphorus loading exceeds or falls short
of the predicted critical phosphorus loading level predicted by
Equation 19. For example, Lake Canadargo's reported phosphorus
loading is approximately 3.5 times greater than its calculated
critical phosphorus loading level. Conversely, Lake Waldo could
adsorb a phosphorus loading increase of over 5.6-fold and still
retain its oligotrophic character, according to Equation 19.
Lake Washington, having a reported phosphorus loading between one
and two times the predicted critical loading, would be classified
as mesotrophic in 1974 on the basis of Equation 19.
Overall, the results of Table 22 are essentially identical
to those illustrated in the Vollenweider phosphorus loading dia-
gram (Figure 19). As the investigator-indicated trophic con-
ditions are in good agreement with the trophic states indicated
in Table 22, this lends further support to the use of these two
methodologies for determining the critical phosphorus loads to
water bodies in a variety of trophic conditions.
COMPARISON OF RESULTS
Before the OECD eutrophication study data can be evaluated
with the Vollenweider phosphorus loading criteria, any discrepan-
cies between the predicted and reported phosphorus loading and
trophic conditions of the US OECD water bodies should be explain-
ed. This was attempted in previous sections in this report. It
is also necessary to try to explain why some US OECD water bod-
ies appear to plot accurately on the Vollenweider phosphorus
loading diagram, based on their reported phosphorus loading
and mean depth/hydraulic residence time characteristics and tro-
170
-------
Table 22. US OECD DATA USED IN VOLLENWEIDER'S CRITICAL PHOSPHORUS
LOADING EQUATION
h-1
Water Body
Blackhawk
Brownie
Calhoun
Came lot -Sherwood
Canadarago
Cayuga
Cedar
Cox Hollow
Dogfish
Dutch Hollow
George
Har pie t
Isles
Kerr Reservoir
Roanoke Arm
^Jutbush Arm
Hydraulic
Loading, q
(m/yr)a
9.8
3.4
2.94
21.4-33. 3
12.8
6 .28
1 .85
5.4-7.6
1 .14
1.67
2.25
3 .67
4 . 5
51.5
1.G1
Calculated
Critical
Phosphorus
Loading , L^ (P)
(mg P/m2/yr)b
167
82
85
294-433
227
247
52
90-130
33
39
86
94
80
745
52
Calculated
Trophic
State0
E
E
E
E
E
E
E
U-E
0
E
0
E
U-E
E
U-E
Investigator-
Indicated Phos-
phorus Loading
(mg P/m /yr)
2130-2320
1180
860
2350-2 G 80
800
800
350
1G20-2080
20
950-1010
70
710
2030
5200
700
Factor Relating
Investigator- Investigator-
Indicated Indicated Load-
Trophic ing to Calcu-^
State0 'd lated Loading"
E
E
E
E
E
M
E
E
0
E
0-M
E
E
E-M
E-M
+13 to +14
+ 14.4
+ 10.1
+5.4 to f9.1
+ 3.5
+ 3.2
+ 6.7
+12.5 to +21.0
- 1.6
+24 to +25
- 1.2
+ 7.6
+ 25
+ 7.0
+ 14
-------
Table 22 (continued). US OECD DATA USED IN VOLLENWEIDER'S CRITICAL
PHOSPHORUS LOADING EQUATION
Water Body
Lamb
Meander
Mendota
Hydraulic
Loading ,q
(m/yr )
1.7U
1.85
2.67
Michigan (open waters)
19711 2.8
t T = 30 yr
1974/ f> 2.8
197lS
0.84
yr
0.8U
Lower Lake Minnetonka
1969 1.32
1973
Potomac Estuary
Upper Reach
Middle Reach
Lower Reach
Redstone
Sal lie
Sammamish
Shagawa
1.32f
120
28.3
8.47
4 .3-6.1
3.56-5 .8?
10
7.1?
Calculated Factor Relating
Critical Investigator- Investigator- Investigator-
Phosphorus Calculated Indicated Phos- Indicated Indicated Load-
Loading ,LC (P) Trophic phorus Loading Trophic ing to Calcu-
(mg P/m2/yr)b Statec (mg P/m2/yr)d State0 'd lated Loading6
44
49
83
181
181
92
92
46
46
1440
403
163
86-1 1 2
83-119
234
135
0
0
U-E
0
0
0
0
E
E
E-
E
E
E
E
E
E
30
30
1200
140
100
140
100
500
100 (180)g
85000
8000
1200
1440-1680
1500-4200
700
700
0
0
E
0
0
0
0
E
E-M
U-E
U-E
U-E
E
E
M
E
- 1.5
- 1.6
+ 14
- 1.3
- 1.8
+ 1.5
+ 1.1
+ 11
+2.2 (+3.9)S
+ 59
+ 20
+ 7.4
+13 to +20
+13 to +51
+ 3.0
+ 5.2
-------
Table 22 (continued). US OECD DATA USED IN VOLLEHWEIDER' S CRITICAL
PHOSPHORUS LOADING EQUATION
Water Body
Stewart
Tahoe
East Twin
1972
1973
1974
West Twin
H 1972
oo 1973
1974
Twin Valley
Virginia
Waldo
Washington
1957
1964
1971
1974
Hydraulic
Loading.q
(m/yr)
23
0
6
5
10
2
2
4
7.6
0.6
1
13
13
13
13
.8
.45
.25
.56
.71
.41
. 34
-9 .5
-0 .9
.71
.8
.8
.8
.8
Calculated
Critical
Phosphorus Calculated
Loading, L (P) Trophic
(mg P/m2/yr)b State0
305
124
118
108
171
61
56
87
130-355
16- 37
95
351
351
351
351
E
0
E
E
E
E
E
M
E
U-E
0
E
E
M
M
Factor Relating
Investigator- Investigator- Investigator-
Indicated Phos- Indicated Indicated Load-
phorus Loading Trophic ing to Calcu-p
.,,2, .d c.d lated Load inn"
(mg P/m /yr) State ^
4820-8050
50
700
500
700
400
300
300
1740-2
(700)g
(500)
(800)
(400)
(200)
(300)
050
1150-1480
17
1200
2300
430
470
E
U-0
E
E
E
E
E
E
E
E
U-0
E
E
M
M
+ 16 to
- 2.5
+ 5
+ 4
+ 4
+ 6
+ 5
+ 3
+ 11 t
.9
.6
.1
.5
.3
.4
o
+ 31 to
- 5
+ 3
+ 6
+ 1
+ 1
.6
.4
.5
.2
. 3
+ 26
( + 5.
(+4.
(+4.
( + 6.
( + 3.
( + 3.
+ 16
+ 92
9)g
6)
7)
5)
6)
4)
-------
Table 22 (continued). US OECD DATA USED IN VOLLENWEIDER'S CRITICAL
PHOSPHORUS LOADING EQUATION
Water Body
Weir
Wingra
Hydraulic
Loading ,q
(m/yr)a
1.5
6
Calculated
Critical
Phosphorus
Loading ,Lc(p)
(mg P/m2/yr)b
46
98
Calculated
Trophic
State0
M
E
Investigator-
Indicated Phos-
phorus Loading
(mg P/m2/yr)d
mo
900
Factor Relating
Investigator- Investigator-
Indicated
Trophic
State0 'd
M
E
Indicated Load-
ing to Calcu-
lated Loading6
+ 3.0
+ 9.2
EXPLANATION:
aHydraulic loading, q = mean depth, z/hydraulic residence time, T .
Based on Equation 19.
E = eutrophic, M = mesotrophic, 0 = oligotrophic, U = ultra
Based on investigator's estimates.
Factor by which investigator-indicated loading exceeds (+) or falls short (-) of
the critical phosphorus loading predicted by Equation 19.
Hydraulic residence time for whole lake.
All data in parentheses represent data received by these reviewers from the principal investigators
subsequent to completion of this report. Examination of the data indicates no significant changes
in the conclusions concerning these water bodies.
-------
phic states, even though other relationships (Figures 14 or 15)
indicate that the reported phosphorus loadings may be in error.
This may be partially because the Vollenweider phosphorus
loading diagram is a log-log graph. This type of graph allows
the values of one or both parameters being plotted to change con-
siderably without a proportionally large change occurring in its
position on the graph. As a result, the reported phosphorus
loadings for many US OECD water bodies can be corrected for pos-
sible over or underestimations without altering their trophic
state categorizations on the Vollenweider phosphorus loading
diagram (Figure 19). The only exceptions are those water bod-
ies which plotted near the permissible or excessive boundary
lines.
Discrepancies between Vollenweider Phosphorus Loading Diagram
and Vollenweider Mean" Phosphorus/Infl_ue_n_t Phosphorus And"
Hydraulic Residence Time Diagram
Figure 14 indicates that the reported phosphorus loading
for several of the US OECD water bodies may have, been under or
overestimated. Those water bodies whose reported phosphorus
loadings may be underestimated include Lower Lake Minnetonka-
1973 (26), East Twin Lake-1974 (41), West Twin Lake-1973 and
1974 (44 and 45, respectively), bake Waldo (48), Lake Weir (53)
and the Upper Reach of the Potomac Estuary (28). Conversely, the
phosphorus loadings to Lakes Isles (1.4), the Roanoke and Nutbush
Arms of the Kerr Reservoir (16 and 17, respectively), Lake Stewart
(35) and Lake Virginia (47) may have bpen overestimated.
Figure 15, based on watershed land usage patterns arid phos-
phorus export coefficients, indicates the phosphorus loading
estimates to Lake Dogfish (10), Lake Lamb (19), Lake Meander (22),
Lake Sallie (32), Lake Tahoe (36), Lake Waldo (48) and Lake
Weir (53) may have been underestimated.
Lake Wai do --
Figure 14 indicates that phosphorus loadings to Lake Waldo
(48) may have been underestimated bv three-fold. Waldo, which is
classified as ultra-oligot rophi o by Powers e_t a_l. (1975) falls
in the ultra-oligotrophi r zone of the \/\>l"l enweicfer phosphorus
loading diagram (Figure 19). If its phosphorus loading estimates
were corrected to the degree, indicated in Figure 14, Lake Waldo
would plot much closer to the meso trophic zone. However, Its
reported nutrient and chlorophyll concentrations, primary pro-
ductivity and other1 classical trophic state indicators indicate
that Waldo is ultra-oligotrophic. It is classed among the most
pristine lakes in the United States. Thus, it would appear that
the phosphorus loading underestimation indicated in Figure 14 may
be in error, and that the reported phosphorus loading estimate
is correct.
175
-------
There are several possible reasons for the disagreement
between the results of Figure 14 and of the Vollenweider phos-
phorus loading diagram (Figure 19). The relationship expressed
in Figure 14 (Equation 26) is based partly on the annual mean
phosphorus concentration. Thus, use of this relationship as a
check on the phosphorus loading to Lake Waldo requires an accurate
knowledge of its annual mean phosphorus concentration. However,
according to Powers et al. (1975), the mean phosphorus concen-
trations reported for Lake Waldo were determined from an annual
visit to Lake Waldo in August or September from 1969 to 1974.
Thus, the reported mean phosphorus concentration was the August
mean value, rather than the annual mean value, and does not neces-
sarily reflect variations in the mean phospnorus concentrations
over the annual cycle. It may not be appropriate to apply the re-
ported growing season mean phosphorus concentration for Lake
Waldo to Equation 26 to check on its reported phosphorus loading.
Therefore, the phosphorus loading underestimation for Lake Waldo
in Figure 14 may be incorrect.
It should also be mentioned that Figure 14 is based on a
relationship derived for phosphorus-limited water bodies. It
is not clear that phosphorus limits algal growth in Lake Waldo
(Powers et al., 1972; Miller et al., 1974).
It is possible that the reported phosphorus loading to Waldo
may be in error to some degree. The phosphorus loadings were not
measured directly. Rather they were based on the results of four
indirect methods (.Powers et al. , 1975), The mean phosphorus load-
ing was obtained by averaging the results of these .four methods.
However, the results of these four methods differ by nearly three-
fold. An average phosphorus loading based on these methods would
incorporate any errors from each method into the final value.
In addition, while Powers et al. (1975) considered the phosphorus
input from precipitation and fallout in their phosphorus loading
estimate, they did not include the phosphorus contribution from
dry fallout (Table 9). According to Kluesener (1972), Sonzogni
and Lee (1974), Murphy (1974) and Murphy and Doskey (1975), dry
fallout can contribute substantial quantities of phosphorus to
water bodies. Kluesener (1972) reported dry fallout contributed
about three times as much total phosphorus and twice as much
total nitrogen to Lake Wingra than did precipitation. Murphy
(1974) reported that dry fallout contributes up to 18 percent
of the present phosphorus loading to Lake Michigan, and that
about half of the dry fallout loading is in the form of ortho-
phosphate, the form most readily available for algal growth.
Thus, this magnitude of phosphorus input could constitute a
significant fraction of the total phosphorus input to oligo-
trophic water bodies, which do not ordinarily have any major
point-source inputs.
Lake Waldo is still in a pristine state, based on its present
limnological characteristics. The phosphorus loading could be in-
creased about five-fold, according to both Figure 19 and Table 22,
176
-------
without altering its trophic state association in the oligotrophic
category. However, such an increase in phosphorus loading would
imply a significant decrease in water quality in Lake Waldo. Its
relatively deep mean depth and long hydraulic residence time, com-
pared to the other US OECD water bodies, implies a relatively
slight increase in phosphorus loading to Waldo could alter its
trophic status. This view is shared by the US OECD investigator
for Lake Waldo.
Lake Weir--
The phosphorus loading anomaly in Figure 14 concerning Lake*
Weir may be more complicated in nature. Lake Weir is atypical
in several respects to the other US OECD water bodies. It is
a seepage lake with no natural tributary or point-source inputs
of water or phosphorus. Rather, it receives its phosphorus solely
from groundwater seepage into the lake, from land runoff directly
into the lake and from atmospheric sources (i.e., precipitation
and dry fallout) directly onto its surface. Also, it is one of
only two US OECD water bodies (Figure 4) located in a sub-tropical
(i.e., warm water) setting. According to Brezonik and Messer
(1975), the application of relationships which were derived in
temperate zones to an area of high permeable sands, high soil
temperature, unique geology and sub-tropical climate, as is found
in the Lake Weir watershed, is questionable. It is possible the
phosphorus loading-algal response relationships in the southern
and southwestern US warm-water lakes and impoundments are dif-
ferent from those found in north temperate-cold water bodies.
This should be remembered in examination of the phosphorus load-
ing and trophic characterization data for Lake Weir.
Figures 14 and 15 indicate the phosphorus loadings to Lake
Weir may have been underestimated by a factor of three. Table
22 also indicates the possibility of a phosphorus loading under-
estimation. However, Lake Weir plots in the mesotrophic zone of
the Vollenweider phosphorus loading diagram, in agreement with
the trophic condition reported by the investigators (Brezonik and
Messer, 1975). A mesotrophic state is consistent with the re-
sults expressed in Table 22 for Lake Weir.
If the phosphorus loading estimates were corrected for the
three fold underestimation indicated in Figures 14 and 15,
Weir would plot in the eutrophic zone of the Vollenweider phos-
phorus loading diagram (Figure 19). However, Brezonik and Messer
(1975) have indicated that while the concentrations of nitrogen
and phosphorus are high throughout the water column and exceed
Sawyer's (1947) critical concentrations at all times of the year,
primary productivity in Lake Weir is low to moderate and nuisance
conditions do not occur. Further, although macrophytes are common
in Lake Weir, floating mats or nuisance growths of macrophytes
are not found. Brezonik and Messer also indicated that generally
177
-------
good water quality is found in Lake Weir. These indications
suggest the degree of phosphorus loading underestimation
indicated for Lake Weir in Figure 14 may be in error.
Another possible reason for the disagreement between Figures
14- and 19 may result from a fundamental difference in the phos-
phorus loading-algal response relationships in temperate and sub-
tropical systems. It is possible that both the reported phos-
phorus loading and trophic state of Lake Weir are correct, and
that what is actually anomalous is the interpretation of the
nutrient loading-algal response relationship in water bodies in
subtropical environments. A phosphorus loading which would place
a temperate water body in the mesotrophic zone of the Vollenweider
loading diagram may produce trophic conditions in a water body
(with the same mean depth/hydraulic residence time characteristics)
in the sub-tropical setting of Florida which would be interpreted
by most investigators as eutrophic. Brezonik et a1. (1969)
have presented some basic differences between northern US
temperate lakes and lakes in north central Florida. Although
the reported and predicted trophic conditions for Lake Weir are
in agreement in Figure 19, additional research on the nutrient
loading-algal response relationships in warm-water bodies may
still be necessary to determine whether the Vollenweider phos-
phorus loading diagram is applicable in its present form, or
whether the permissible and excessive boundary loading lines
may have to be modified to fit different nutrient loading-algal
response relationships in warm-water lakes and impoundments.
Lower Lake Minnetonka--
The phosphorus loading to Lower Lake Minnetonka-1973 (26)
is indicated as possibly being underestimated about two-fold in
Figure 14. Lower Lake Minnetonka plots at the early mesotrophic-
late oligotrophic boundary area of the Vollenweider phosphorus
loading diagram (Figure 19), although Megard (1975) has classified
Minnetonka as eutrophic. Minnetonka has undergone sewage efflu-
ent diversion, completed in early 1972, reducing the annual phos-
phorus influx almost 80 percent. Since that time, according to
Megard (1975), a decreasing mean phosphorus concentration and
relative integral photosynthetic rate indicates Lower Lake
Minnetonka to be changing from a eutrophic to a mesotrophic
condition. This is in agreement with the results of Table 22.
However, the inappropriate use of a non-equilibrium water body
mean phosphorus concentration for predicting phosphorus loading
is likely the reason for the loading underestimation indicated
in Figure 14. This was discussed in relation with the phosphorus
residence time in a previous section of this report.
178
-------
Twin Lakes-1973 and 1974~~
East Twin Lake-1974 (41) and West Twin Lake-1973 and 1974
(44 and 45, respectively) are indicated in Figure 14 as possibly
having phosphorus loading underestimations between two and three-
fold. Based on their plankton characteristics, both East Twin
Lake and West Twin Lake are currently in a eutrophic condition,
according to Cooke et al. (1975). These observations are consis-
tent with the trophic cTTaracter for these water bodies predicted
in Table 22 and with the Vollenweider phosphorus loading diagram
(Figure 19). This suggests the phosphorus loading underestimation
indicated in Figure 14 may be in error.
As with Lower Lake Minnetonka, the reason for the Twin Lake's
phosphorus loading underestimation indicated in Figure 14 is
likely related to the non-equilibrium mean phosphorus concentra-
tions of these water bodies. Sewage was diverted from the Twin
Lakes during 1972 to a package plant which discharges away from
the watershed. Thus, the relationship expressed in Figure 14,
based partly on the mean phosphorus concentration, is likely to
produce erroneous results.
The phosphorus residence time for Lower Lake Minnetonka is
about four years (Table 21) while that of East Twin and West
Twin is about 1 and 1.5 years, respectively. Thus, Lower Lake
Minnetonka should reach a new steady-state mean phosphorus con-
centration in about 10 to 12 years. East Twin Lake and West
Twin Lake should reach their equilibrium states in about three
and five years, respectively. Thus, while their phosphorus
loadings can be reduced rapidly'to substantially lower levels
by remedial treatments, it will take a longer period of time for
these water bodies to reach new equilibrium mean phosphorus con-
centrations and trophic conditions. Of the three water bodies,
East Twin Lake appears to be closest to a new equilibrium phos-
phorus concentration, based on its phosphorus residence time.
This is consistent with its position on the Vollenweider phos-
phorus loading diagram (Figure 19) and with the results of
Figure 14.
One point that should be mentioned here is that, while the
Vollenweider model (Figure 19) appears to accurately predict
the degree of fertility of water bodies as described by their
plankton productivity characteristics, it does not address the
problem of estimation of the degree of fertility expressed in
macrophyte growth. The Twin Lakes have an extensive littoral
area and approximately half of their primary productivity is
in the form of macrophyte growth. According to Cooke et al.
(1975), the Twin Lakes are of poorer water quality, from the
point of view of the recreational user, than is indicated by the
early eutrophic characterization given them by the Vollenweider
179
-------
phosphorus loading diagram. The Vollenweider model is based
primarily on plankton characteristics, and may not be applicable
in its present form to water bodies with extensive macrophyte
problems such as are found in the Twin Lakes and several other
US OECD water bodies, or to turbid waters as found in some Texas
lakes and impoundments (Lee, 1974b).
Potomac Estuary and Lake of the Isles--
The Upper Reach of the Potomac Estuary (28) is indicated
in Figure 14 to have phosphorus loading underestimations between
two and three fold. The Potomac Estuary is indicated by Jaworski
(1975) and on the Vollenweider phosphorus loading diagram
(Figure 19) as being highly eutrophic. Table 22 also indicates
that the phosphorus loads to all Reaches of the Potomac Estuary
are all many-fold above the permissible loading levels. Lake of
the Isles (14) is indicated in Figure 14 as having a possible
phosphorus loading overestimation of about two fold. This water
body is characterized by Shapiro (1975a) and on the Vollenweider
phosphorus loading diagram as being highly eutrophic.
As mentioned earlier, the relationship expressed in Figure 14
requires accurate knowledge of the annual mean phosphorus concen-
tration in the water body. The reported mean phosphorus concen-
trations for the Potomac Estuary and Lake of the Isles were the
mean summer value and the mean summer surface value, respective-
ly, rather than the annual mean values of these water bodies.
Because these water bodies are highly eutrophic, the mean phos-
phorus concentration during the summer months will lik-ely vary
cyclically as a function of algal blooms and die-offs. As a
result, the measured mean phosphorus concentration would be a
function of when the water body was sampled. Thus, the use of
the summer mean phosphorus concentration in the relationship ex-
pressed in Figure 14 as a check on the phosphorus loading is
probably not valid for these water bodies.
There are several other eutrophic US OECD water bodies (i.e.,
Brownie, Calhoun, Cedar, Harriet) for which only the mean summer
phosphorus concentration was reported, yet whose phosphorus load-
ings appear reasonable in Figure 14. This may be coincidental
as a function of when these water bodies were sampled for their
mean phosphorus concentrations. These findings are consistent
with the results of Figure 15, which is not based on mean phos-
phorus concentrations, and which indicates the phosphorus load-
ings to the Potomac Estuary and Lake of the Isles to be reason-
able. One additional factor to consider in examination of the
Potomac Estuary data is that it has typical estuarine water circu-
lation patterns. These circulation patterns would likely alter
the nutrient loading-algal response relationships which are de-
pendent on hydraulic residence time.
180
-------
Lake Stewart, Lake Virginia and Twin Valley Lake--
The phosphorus loadings for Twin Valley Lake (46), Lake
Stewart (35) and Lake Virginia (47) are indicated in Figure 14
as being overestimated by approximately two, three and four-fold
respectively. These water bodies are Wisconsin impoundments
with shallow mean depths and short hydraulic residence times.
According to Piwoni and Lee (1975) and their position on the
Vollenweider phosphorus loading diagram (Figure 19), these water
bodies are highly eutrophic.
The phosphorus loading underestimation indicated in Figure
14 for Lake Virginia may be due to an error in the calculation
of the hydraulic residence time (i.e., water body volume
(m3)/annual inflow volume (m3/yr)). With a mean depth of 1.7 m,
and a mean hydraulic residence time of 1.8 years, the resultant
hydraulic loading, qs (Z/TW), calculates to be 0.9 m/yr. This
value is unrealistically small for Lake Virginia's watershed.
The meteoric discharge rate is a measure of the rate at which
water is supplied to the water body from the watershed. Accord-
ing to Vollenweider and Dillon (1974; Vollenweider, 1976b), the
relationship is expressed as
MDR = (qs (A /A )) (36)
o
where MDR = meteoric discharge rate (m/yr),
q = hydraulic loading = z/i (m/yr),
z = mean depth (m),
T = hydraulic residence time (yr),
CO
2
A = water body surface area (m ), and
2
A , = watershed area (m ).
d
For Lake Virginia, MDR = (0.9 m/yr) (1.8 x 105 m2/6.5 x 106 m2)
= 0.02 m/yr. This low meteoric discharge rate is unlikely for
the Lake Virginia watershed area. The nearby Dutch Hollow Lake
and Lake Redstone have meteoric discharge rates of 0.22 m/yr
and 0.35 m/yr, respectively. Since the mean depth, watershed
area and water body surface area appear to be correct for Lake
Virginia, this suggests the hydraulic residence time may be in
error, probably overestimated by a factor of ten. If the
hydraulic residence time was changed from 1.8 to 0.18 years,
the value for [P]/[P] in Figure 14 would change from 0.06 to
-------
0.6, and the value for 1/(1 + JTp would change from 0.4 to
0.7 (Table 15). These new values plotted into Figure 14 would
place Lake Virginia in a position corresponding^to less than a
two-fold phosphorus loading overestimation, indicating that the
phosphorus loading estimate for Lake Virginia is reasonable.
Piwoni and Lee (1975) have indicated that the values re-
ported for Lake Virginia are highly uncertain because this water
body is a seepage lake and may behave quite differently from a
water body with a base flow surface input. They have also
indicated that the phosphorus loading estimates may be high be-
cause of the very sandy soils in Lake Virginia's watershed, which
would reduce overland transport of phosphorus. This would re-
sult in an indication of a possible phosphorus loading over-
estimation, particularly since the nutrient loadings to Lake
Virginia were estimated from watershed nutrient export coeffi-
cients (Piwoni and Lee, 1975). There is also a possibility that
the incoming phosphorus to Lake Virginia may be short-circuited
out of the lake during high flow periods. This would also pro-
duce a misleading estimate of the phosphorus loadings based on
Equation 26.
The possible phosphorus loading overestimations for Lake
Stewart and Twin Valley Lake cannot be resolved in the same man-
ner. Their hydraulic residence times appear reasonable, rela-
tive to the other impoundments in the region. If Figure 14 is
incorrect such that the phosphorus loading estimates for Lake
Stewart and Twin Valley Lake are reasonable, then according to
Vollenweider (1976a; 1975d) the mean phosphorus concentration
in these water bodies is lower than would be expected for the
reported phosphorus loadings. This indicates that the sedimenta-
tion rate in these water bodies is statistically above average.
Such a situation currently exists in Lake Erie (Vollenweider,
1975d). Whether this also occurs in Lake Stewart and Twin Valley
Lake is unknown.
Another factor which may have to be considered is that the
reported mean phosphorus concentration in these two water bodies
is the average of the mean summer and mean winter values. It
is not known whether a mean value derived from continuous measure-
ments over the annual cycle would differ significantly from a mean
value derived from the summer and winter average value in these
two water bodies. A large difference in the value of the mean
phosphorus concentrations measured by these two methods may
significantly alter the indicated phosphorus loading overestima-
tion for Twin Valley Lake and Lake Stewart in Figure 14. How-
ever, it should also be noted that' the same procedure was em-
ployed by Piwoni and Lee (1975) for other US OECD impoundments
in the same region and Figure 14 indicates the phosphorus loading
estimates for these other impoundments to be reasonable. A fac-
tor which may influence the phosphorus in Lake Stewart compared
to the other lakes is that a potentially significant part of
182
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Lake Stewart has extensive macrophyte growth which would tend
to alter the cycling of phosphorus in the lake. Therefore, the
phosphorus loading overestimation indicated for Lake Stewart in
Figure 14 may be incorrect.
Kerr Reservoir--
Figure 14 indicates the phosphorus loading estimates for
both the Roanoke and Nutbush Arms of the Kerr Reservoir (16 and
17, respectively) may be overestimated between two and four-fold.
The two arms of the Kerr Reservoir have been treated separately
by Weiss and Moore (1975) because they differ significantly in
their morphometric, hydrologic and limnologic characteristics.
In both arms of the reservoir, there is a changing magnitude in
nearly all water quality parameters as one moves from the upstream
end of the arm toward the dam. In general, the nutrient and
chlorophyll concentrations and associated productivity parameters
decrease as one approaches the dam, indicating a relative increase
in water quality in the direction of the dam. Weiss (1977)
indicated this shift in water quality illustrates that the
sedimentation characteristics of the upper arms of the Kerr
Reservoir, and probably other river systems impoundments, have a
marked impact on reduction of the phosphorus entering these
water bodies. The results would be a lower net phosphorus con-
centration in the upper arm than expected (this was discussed
earlier in relation to the inorganic nitrogen:soluble ortho-
phosphate ratio in the Kerr Reservoir; see Tables 9 and 10).
When this lower phosphorus concentration was inserted into
Equation 25 the result was the predicted underestimation of
phosphorus load indicated in Figure 14. Weiss (1977) rioted that
this interpretation was substantiated by Table 18, in which the
phosphorus load prediction is based on watershed phosphorus
export coefficients.
The flushing rate is believed to be the major controlling
variable in establishing the relative degree of fertility and
behavior differences in the two arms. According to Weiss and
Moore (1975) the hydraulic residence time is approximately
70 days in the Roanoke Arm and approximately 1800 days in the
Nutbush Arm. These computations are based on inflow water volume
and do not consider exchange of water between the main body of
the lake and the arms. The actual hydraulic residence time of
the water in each arm would likely be less than the indicated
amount by a factor somewhat proportional to water exchange
between various parts of the lake. However, Weiss (1977) has
indicated that the main flow of water through the Kerr Reser-
voir is down the Roanoke Arm and into the major basin above the
dam. The hydraulic load down the Roanoke Arm is so much faster
than the flow from the Nutbush Arm that exchange of water be-
tween the two arms is inconsequential. Weiss has indicated that
this is substantiated by the fact that the phosphorus concen-
183
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tration at the end of the Nutbush and Roanoke Arms, where they
both enter the main basin, are approximately the same,
suggesting that interchange effects are negligible. The high
correlation of growth parameters with the hydraulic residence
time indicates the importance of this factor in establishing the
relative degree of fertility of the two arms.
The two arms of the Kerr Reservoir are described as
eutrophic-mesotrophic by Weiss and Moore (1975) and plot in the
eutrophic zone on the Vollenweider phosphorus loading diagram
(Figure 19). The two arms would still remain in the eutrophic
zone of the Vollenweider loading diagram if their phosphorus
loading estimates were reduced by the degree indicated in
Figure 14. However, they would be closer to the excessive load-
ing boundary line. Unfortunately, watershed land usage data
was available only for the whole watershed, not for the sub-
watersheds of the two arms. Since the amount of mixing between
the two arms could not be estimated, it was not possible to use
Figure 15 to check on the reported phosphorus loadings. How-
ever, Table 22 indicates that the phosphorus loadings are many
fold above the permissible level. While it is not unequivocal,
this implies the phosphorus loading overestimation indicated
in Figure 14 for the two arms of the Kerr Reservoir may be in-
correct .
Discrepancies Between Vollenweider Phosphorus Loading Diagram
and Watershed Phosphorus Export Coefficient Calculations
Dogfish Lake, Lamb Lake and Meander Lake—
Figure 15 indicates the phosphorus loadings for Lakes Dog-
fish (10), Lamb (19) and Meander (21) are approximately five-
fold underestimated. Contrastingly, Figure 14 indicates their
phosphorus loadings are reasonable. The results of Table 22
are consistent with the phosphorus loading underestimation in-
dicated in Figure 15. Thus, it would appear that the reported
phosphorus loadings and the ultra-oligotrophic conditions of
Dogfish, Lamb and Meander predicted in Figure 19 may be in
error. The_low chlorophyll level in these water bodies indicate:;
them to be in relatively unproductive states. However, accord-
ing to Table 22, they are not in the ultra-oligotrophic state
indicated by their large vertical distance below the permissible
184
-------
loading line on the Vollenweider phosphorus loading diagram
(Figure 19). Based on their phosphorus and hydraulic loadings,
these three water bodies plot in the same general area of the
Vollenweider phosphorus loading diagram (Figure 19) as does Lake
Waldo, implying that they exhibit about the same relative degree
of oligotrophy as does pristine Lake Waldo. However, their water
quality does not support the view that they are relatively as
oligotrophic as Lake Waldo. The reported mean phosphorus and
nitrogen concentrations are all higher in Lakes Dogfish, Lamb
and Meander than those reported for Lake Waldo. Further, the
mean chlorophyll concentrations are also considerably higher in
Dogfish, Lamb and Meander than in Waldo, in some instances by an
order of magnitude or greater. Secchi depth is also considerably
greater in Waldo than in Dogfish, Lamb and Meander. However,
these three water bodies are reported to have high humic color
and, therefore, possibly have reduced light penetration. Con-
sequently, comparison of Secchi depth measurements would not
yield reliable information concerning the degree of oligotrophy
in Dogfish, Lamb and Meander relative to Waldo. It should also
be mentioned that the higher chlorophyll concentration in Dog-
fish, Lamb and Meander than that found in Waldo implies the
color of the water is not reducing the primary production in
these three water bodies to any great extent relative to Waldo.
In general, the results of Figure 15, Table 22 and the
reported water quality data Indicate that the reported phos-
phorus loadings for Lakes Dogfish, Lamb and Meander may have
been underestimated, though perhaps not to the extent indicated
in Figure 15. Consequently, their position on the Vollenweider
phosphorus loading diagram may have to be adjusted accordingly
so as to produce an accurate representation of the relative
trophic states of these three water bodies.
Lake Tahoe--
Figure 15 indicates the phosphorus loading to Lake Tahoe (36)
may have been overestimated by a factor of four. However, Lake
Tahoe appears to be nitrogen-limited with respect to aquatic
plant nutrient requirements (Table 9). As the Vollenweider
phosphorus loading diagram was developed for phosphorus-limited
water bodies, attempting to categorize its trophic condition based
solely on its trophic state association in the Vollenweider phos-
phorus loading diagram may not be a valid procedure. Therefore,
Lake Tahoe's nutrient loading-trophic response relationship will
be examined further in an analysis of the US OECD water body
nitrogen-loading estimates in a subsequent section. It should
be noted that Schindler (1977) has recently indicated there ap-
pears to exist a very precise relationship between the total
phosphorus concentration in a water body and the standing crop
185
-------
of phytoplankton, even In water bodies whose low N:P ratios should
favor nitrogen limitation. This suggests that natural mechanisms
may compensate for deficiencies of nitrogen in many water bodies.
Lake Sallie--
Figure 15 indicates Lake Sallie's (32) phosphorus loadings
may have been underestimated between two to seven fold. The same
trend is noted in Figure 14. Lake Sallie possesses one of the
highest ratios of watershed area to water body surface areas of
all the US OECD water bodies. Thus, its phosphorus loading is
very high when it is calculated with watershed land use phosphorus
coefficients. Lake Sallie plots in the ultra-eutrophic zone.
However, Neel (1975) characterizes Lake Sallie as being in a
late mesotrophic-early eutrophic state, suggesting the high de-
gree of fertility indicated in Figure 19 may be in error. Accord-
ing to Neel, the atmospheric input of phosphorus from dry fallout
was not considered in the phosphorus loading estimates. There-
fore, it is possible that Lake Sallie's phosphorus loadings are
underestimated to some degree. Table 22 also indicates that Lake
Sallie may be more fertile than the investigator-indicated late
mesotrophic-early eutrophic condition.
However, one other factor that must be considered is that the
water quality problems associated with excessive nutrients in Lake
Sallie are manifested to a major extent in the growth of attached
macrophytes. As discussed in earlier sections of this report,
the excessive and permissible loading lines on the Vollenweider
phosphorus loading diagram (Figure 19) are based primarily on
planktonic algal problems and may not be applicable to water
bodies such as Lake Sallie which possess extensive beds of macro-
phytes . The relatively high phosphorus loading to Lake Sallie
may be assimilated to a great extent in macrophyte growth, rather
than by algal uptake. This would keep both the algal and mean
phosphorus concentrations in Lake Sallie lower than expected from
its reported phosphorus loading. This would explain why Figure
15, based on watershed land usage, indicates a possible phosphorus
loading underestimation for Lake Sallie while Figure 14, based
partly on mean phosphorus concentration, indicates the phosphorus
loading to be reasonable. Any estimation of trophic state, based
on Lake Sallie's algal characteristics alone, would likely indicate
a trophic condition which is consistent with that indicated by
Neel (1975), but which is not a realistic appraisal of the over-
all degree of the fertility of Lake Sallie because it ignores the
portion of Lake Sallie's primary productivity which is manifested
in macrophyte growth.
186
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SECTION VIII
US OECD EUTROPHICATION STUDY NITROGEN DATA:
AS APPLIED IN VOLLENWEIDER NITROGEN LOADING AND MEAN
DEPTH/HYDRAULIC RESIDENCE TIME RELATIONSHIP
In addition to phosphorus loadings, the Vollenweider relation-
ship can also be applied to total nitrogen loadings. However,
because of the relatively scant knowledge concerning nitrogen
relationships in natural waters, Vollenweider has not developed
the permissible and excessive boundary conditions for a nitrogen
loading-mean depth/hydraulic residence time relationship. Thus,
the trophic state of a water body which is nitrogen limited with
respect to aquatic plant nutrient requirements cannot be deter-
mined in the same manner as with Vollenweider's phosphorus load-
ing diagram. Conceptually, such an application is possible.
However, it would necessarily be more difficult to establish the
permissible and excessive nitrogen loading boundary lines on
such a loading diagram.
As indicated earlier, several approaches could be utilized
to develop critical nitrogen loadings for lakes. One of the most
obvious involves using a direct proportion between the critical
N and P loadings based on typical algal stoichiometry of 16
nitrogen atoms for every phosphorus atom. On a mass basis, this
would mean that the permissible nitrogen loadings would be in-
creased by approximately 7.5 times the corresponding phosphorus
loadings.
Another approach would be utilization of the equivalent
nitrogen concentrations developed by Sawyer (1947). The validity
for this approach stems from the fact that Sawyer's critical
phosphorus concentrations play a dominant role in establishing
the permissible and excessive lines on the Vollenweider phosphorus
loading relationship. Sawyer suggested a critical inorganic
nitrogen concentration of 0.3 mg N/l. There are a number of
potential problems involved in attempting to use a direct pro-
portion between nitrogen and phosphorus critical loads, the most
important of which would occur in highly eutrophic lakes, where
nitrogen, rather than phosphorus, is frequently the key limiting
element. In these water bodies, blue-green algae, some of which
are nitrogen fixers, often dominate. While nitrogen fixation
does occur in many lakes, its overall significance is poorly
187
-------
understood. It does not appear, as sometimes stated, that
nitrogen fixation prevents lakes from becoming nitrogen limited.
There are some lakes which show significant nitrogen limitation
in the presence of nitrogen-fixing algae. Torrey and Lee (1976),
studying Lake Mendota, found that less than 10 percent of the
total nitrogen input was from nitrogen fixation.
Eutrophic lakes frequently show appreciable denitrification
reactions in which nitrate is converted to nitrogen gas in
anoxic waters and sediments. This type of reaction would tend
to convert readily available nitrogen into unavailable forms.
Brezonik and Lee (1968) determined the significance of denitrifi-
cation as a means of removing nitrogen from Lake Mendota.
Probably one of the most significant problems with trying to
develop a similar set of relationships for nitrogen as have been
presented for phosphorus is that it is often more difficult to
accurately estimate nitrogen loads. Potentially significant
problems occur with estimations of nitrogen input from ground-
water, which can be an appreciable nitrogen source for some lakes.
As discussed by Sonzogni and Lee (1974), even if the groundwater
input and its associated nitrate content are known, one cannot be
certain of the degree of nitrification, if any, that will occur
when the groundwater nitrate comes in contact with the lake
sediments.
The total nitrogen loading diagram, containing the data for
the US OECD water bodies, is presented in Figure 21. The data
was presented in Table 20. The total nitrogen loadings is com-+
prised of the inorganic nitrogen fraction (i.e., _N03 + N02 + NHij.
as N), plus the organic nitrogen fraction, except as indicated.
There are fewer data points in Figure 21 than in Figure 19
because nitrogen loadings were not reported for all the US OECD
water bodies.
If one compares the nitrogen loading diagram (Figure 21)
with the phosphorus loading diagram (Figure 19), an interesting
observation is that, except for the order of magnitude difference
on the loading axis, there is a good agreement between the
relative positions of the common water bodies on both the load-
ing diagrams. The relative zones denoting the different trophic
states on the phosphorus loading diagram are also maintained on
the nitrogen loading diagram. This similarity implies that a
water body receives nutrients in a relatively constant ratio,
with the nitrogen loading being approximately one order of
magnitude greater than the phosphorus loading. This is consistent
with the view that different types of land usage within a watershed
will yield a relatively constant amount of nutrient export over
the annual cycle. In addition, the ratio of nitrogen to phosphorus
of ten to one is approximately at the boundary condition between
limiting nutrients (i.e., above an N:P mass ratio of about eight
to one, phosphorus is the limiting aquatic plant nutrient; below
an eight to one ratio, nitrogen appears to be the limiting
188
-------
100
o
_J
U)
o
o
tr
<
(-
o
10
'35
:(288)
28
.39
t29 *I6
47
SU-^S
40
46 5
Jl W22
34 -50
(54
I5'
52
.53
.32
17'
•30
O
O
23-B
12
O
23-A
,36
48
I I I
III
III
INVESTIGATOR- INDICATED
TROPHIC STATE".
• -EUTROPHIC
A- MESOTROPHIC
O-OLIGOTROPHIC
I I I
01 I 10 100
MEAN DEPTH,Z/HYDRAULIC RESIDENCE TIME,TW
(m /yr)
1000
Figure 21. US OECD Data Applied to Vollenweider Nitrogen
Loading and Mean Depth/Hydraulic Residence
Time Relationship
189
-------
nutrient -- see Tables 9 and 10). This implies nitrogen and
phosphorus are present in such constant relative amounts that
either nutrient could become limiting with a small relative
increase in the other. Such a view is consistent with a water
body being phosphorus-limited during one time of the year and
nitrogen-limited during another time of the year (i.e., Lake-
Mendota). It is also consistent with nitrogen limitation in one
portion of a water body and phosphorus limitation in another portion
of the same water body at the same time because of different land
usage patterns in different portions of the watershed (i.e.,
Potomac Estuary -- see Table 9).
There is no equivalent expression for Vollenweider's mean
phosphorus/influent phosphorus concentration relationship
(Equation 26) to check the US OECD nitrogen loading estimates.
There is also no equivalent expression for Vollenweider's criti-
cal phosphorus loading relationship (Equation 19) which can be
applied to the US OECD water body loadings. However, it is
possible to compare the reported nitrogen loadings with those
predicted with the watershed land use nitrogen export coefficient
calculations. This was done earlier for the US OECD water
bodies (Figure 16). The US OECD data were presented in Table 18.
The nitrogen watershed land use export and atmospheric input
coefficients used by these reviewers were taken from Table 17 .
Figure 16 indicates generally good agreement between the
predicted and reported nitrogen loadings for the US OECD water
bodies. As with the phosphorus loadings, a nitrogen loading
was considered reasonable if it was within two-fold above or
below the nitrogen loading predicted with the use of the water-
shed land use nitrogen export calculations. However, it should
be noted that most US OECD investigators did not report data for
dry fallout and nitrogen fixation in their nitrogen inputs
(Table 13). If the results of Figure 16 are correct, this
suggests these sources are not significant nitrogen inputs to
the US OECD water bodies when they are compared to the other
nitrogen inputs. This is inconsistent with the observations of
Kluesener (1972) and Sonzogni and Lee (1974) who reported that
nitrogen inputs from these two sources could be substantial.
COMPARISON OF RESULTS:
Discrepancies Between Investigator-Indicated Nitrogen Loadings
and Watershed Nitrogen Export^ Coefficient Calculations
There are a few US OECD water bodies in Figure 16 whose
reported nitrogen loadings are indicated as possibly being in
error. These include Lake Sallie (32), Lake Sammamish (33),
Lake Tahoe (36), East Twin Lake-1972 (39), West Twin Lake-
1972 (43), and Lake Waldo (48). Among the US OECD water bodies
whose nitrogen loadings are indicated in Figure 16 as possibly
being in error, only Lakes Sallie (32), Tahoe (36) and Waldo
(48) may be nitrogen-limited.
190
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Lake Sallie --
Lake Sallie is indicated as having a nitrogen loading under-
estimation of approximately thirty-fold. In Vollenweider's
phosphorus loading diagram (Figure 19), Lake Sallie .plots in a
zone indicative of a relatively advanced eutrophic condition.
However, as Lake Sallie may not be phosphorus-limited (Table 9),
this predicted trophic condition in Figure 19 may not be indica-
tive of Lake Sallie's true trophic state. In fact, Neel (1975)
has characterized Lake Sallie as being in a late mesotrophic-
early eutrophic condition. Neel (1975) has also indicated that
phosphorus does not appear to control algal growth in Lake Sallie
beyond a certain point. This is consistent with observations
made by Vollenweider (1975a) that as a water body becomes more
eutrophic, beyond a certain point nitrogen becomes the limiting
nutrient, even though phosphorus may initially have been limit-
ing aquatic plant growth. According to Vollenweider, the turn-
ing point is reached when the ratio of the nitrogen residence
time to the phosphorus residence time drops below a value of one.
However, only the inorganic nitrogen concentration for Lake
Sallie was reported. Calculation of the nitrogen residence time
requires the total (i.e., organic fraction + inorganic fraction)
nitrogen concentration be known. Therefore, calculation of the
ratio of the residence times of nitrogen to phosphorus is not
possible for Lake Sallie (see Table 21). As a result, it is not
clear whether nitrogen or phosphorus limits algal growth in Lake
Sallie.
Lake Tahoe --
The nitrogen loading estimate for Lake Tahoe (36) is
indicated in Figure 16 as being underestimated about four-fold.
This water body is classified as ultra-oligotrophic by Goldman
(1975) and by its position on the Vollenweider phosphorus load-
ing diagram (Figure 19). It also plots in the lower half of
the nitrogen loading diagram (Figure 21), implying an oligotrophic
status. Lake Tahoe is nitrogen-limited (Table 9) according to
its investigator.
The atmospheric nitrogen contributions for Lake Tahoe were
considered insignificant by Goldman (1975). However, several
investigators (Kluesener, 1972; Sonzogni and Lee, 1974; Murphy,
1974) have indicated this can be a significant nutrient source,
especially for oligotrophic water bodies. In addition, the
nitrogen contribution from nitrogen fixation was not considered
in the nitrogen loading estimate for Lake Tahoe, though this
latter source is likely small.
The present condition of Lake Tahoe indicates it to be much
closer to its limit of permissible nutrient loading than
originally thought (Vollenweider and Dillon, 1974). Thus, the
nitrogen loadings to Lake Tahoe may have been underestimated to
some degree. However, it is not clear that the reported nitrogen
191
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loadings have been underestimated by the factor of four indicated
in Figure 16.
Lake Sammamish. Lake Cavuga and Twin Lakes --
Lake Sammamish, East Twin Lake-1972 and West Twin Lake-1972
show apparent nitrogen loading overestimations based on Figure 16.
Dry fallout and nitrogen fixation contributions were not considered
in the nitrogen loading estimates for these water bodies. As a
result, one would expect the nitrogen loadings to be underestimated,
rather than overestimated, unless the nitrogen loadings from one
or more of the sources have been highly overestimated. The pos-
sible nitrogen loading overestimations of approximately two-fold
for the Twin Lakes (East Twin Lake-1972 (39) and 1974 (40) and
West Twin Lake-1972 (43) and 1973 (44)) indicated in Figure 16
are likely in error. The nitrogen loading for Cayuga (6) is also
possibly overestimated by nearly two-fold. The nitrogen loadings
reported for these three water bodies comprise only the inorganic
nitrogen fractions of the total nitrogen loading. They do not
include the organic nitrogen fraction. While the organic nitrogen
fraction is not immediately available for algal growth, Cowen et al.
(1976a; 1976b) have reported that, under optimal conditions, 50~to~
80 percent of the organic nitrogen fraction present in urban and
rural runoff can be converted, in a few weeks to several months,
to inorganic nitrogen forms available for algal growth. Conse-
quently, omission of the organic nitrogen fraction can result in
a gross underestimation of the total nitrogen loading to a water
body in an urban or rural area. It would seem that these three
water bodies could not exhibit the nitrogen loading overestimation
indicated in Figure 16 unless the inorganic nitrogen 'fraction of
the total nitrogen loading has been grossly overestimated. As
a result, the overestimation of the nitrogen loadings indicated
in Figure 16 for the Twin Lakes and Lake Cayuga may be in error.
In general, the nitrogen loadings for most of the US OECD
water bodies, when compared with the nitrogen loadings derived
from watershed land use nitrogen export coefficients, appear to
be reasonable. This supports the view of these reviewers that
the use of a nitrogen loading diagram for denoting trophic state
associations for nitrogen-limited water bodies, similar to the
Vollenweider phosphorus loading diagram for phosphorus-limited
water bodies (i.e., Figure 19), is plausible. Such an applica-
tion, however, must wait until a valid input-output model
similar to that derived for phosphorus (Vollenweider, 1975a)
is available for nitrogen loadings.
192
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SECTION IX
US OECD DATA APPLIED IN OTHER NUTRIENT RELATIONSHIPS
US OECD PHOSPHORUS DATA APPLIED IN VOLLENWEIDER ' S PHOSPHORUS
LOADING CHARACTERISTICS AND MEAN CHLOROPHYLL RELATIONSHIP
As indicated earlier, several investigators have demonstrated
a relationship between phosphorus concentration at spring over-
turn and the annual or summer chlorophyll concentrations (Sawyer,
1947; Sakamoto, 1966; Dillon, 1974a; Dillon and Rigler, 1974a;
Jones and Bachmann , 1976). A positive correlation between these
parameters was also illustrated by Vollenweider at the May, 1975
North American OECD meeting in Minneapolis. Consequently, Vollen-
weider (1976a) developed a diagram for predicting algal biomass,
expressed as chlorophyll concentration, as a function of a water
body's specific phosphorus loading characteristics. The deriva-
tion of this approach was presented in an earlier section of this
report (see Equation 20 and Figure 11). The reader is reminded
that this phosphorus loading expression (L(P) /qs) / (l+/z7q^) is
equivalent to the predicted in-lake steady state mean phosphorus
concentration. In Equation 20 (used in Figure 22), the phosphorus
loadings can be checked as a function of the term L(P)/qs and
related to the mean in-lake phosphorus concentration. A similar
approach was used to check the phosphorus loading estimates, as
illustrated in Figure I'l and Equations 25 and 26.
The phosphorus loading characteristics and epilimnetic mean
chlorophyll a diagram is presented in Figure 22 for the US OECD
water bodies. The pertinent data for this diagram are presented
in Table 23. If a data range was reported for a water body, the
mean value was used in all calculations.
Based on Sawyer's (1947) and Sakamoto's (1966) critical nu-
trient concentrations, oligotrophic water bodies will plot to the
left of the 10 mg/rn^ phosphorus loading characteristics level, and
eutrophic water bodies to the right of the 20 mg/m phosphorus
Io-.idi.ng char -soter'istirs level. The mesotrophic water bodies would
plot between these two loading levels. The relative degree of
•--HI trophy or oligotrophy of a water body is determined by its hori-
zontal displacement to the right or left of the 10 mg/m^ phos-
phorus loading characteristics level (i.e., predicted in-lake
steady state phosphorus concentration). Thus, this 10 mg/m^ con-
centration corresponds to Vollenweider ' s (Figure 19) permissible
phosphorus loading.
193
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Table 23. US OECn DATA APPLIED TO VOLLENWEIDER'S PHOSPHORUS
LOADING AND MEAN CHLOROPHYLL a CONCENTRATION
RELATIONSHIP
to
-P
-
Trophic
Water Body State3
Blackhawk (l)d
Brownie ( 2 )
Calhoun (3)
Came lot -Sherwood
Complex (4)
Canadarago
1968 (5-A)
1969 (5-B)
Cayuga
1972 (6-A)
1973 (6-B)
Cedar (7)
Cox Hollow (8)
Dogfish
1972 (10)
Dutch Hollow (11)
George (12)
Harriet (13)
E
E
E
E
E
E
M
M
E
E
0
E
0-M
E
Phosphorus
Loading, L(P)
(mg/m /yr)
2.1 30-2320
1180
860
2350-2680
800
800
800
800
350
1620-2080
20
950-1010
70
710
Mean
Depth ,z
(m)
4 .9
6.8
10.6
3
7. 7
7.7
54
54
6.1
3.8
4
3
18
8.8
Hydraulic
Loading ,q
(m/yr)c
9
3
2
21 .4
12
12
6
6
1
5 .4
1
1
2
3
.8
. 4
.9
-33.3
. 8
.8
.3
.3
.8
-7.6
.1
.7
.2
.7
L(P)A, _
i + /z/qs
1 3 3
144
101
69
35 .1
35.1
32.4
32.4
69.0
160
6.3
246
8.3
75
Mean [loan
Secchi Chlorophyll a
Depth Concentration
(m) (ug/l)b
3
1
2
2
1
2
2
1
1
2
0
8
2
.6
.5
.1
.0
-
.8
.3
.3
.8
.5
.5
.8
.5
.4
15e
6f
6f
63
13
7
6
5
20f
26e
4 (2)g
34e
_
4f
-------
Table 23 (continued). US OECD DATA APPLIED TO VOLLIItlWEIDER'S
PHOSPHORUS LOADING AND MEAN CHLOROPHYLL a CONCENTRATION
RELATIONSHIP
CD
cn
Trophic
Water Body State3
Isles (14)
Kerr Reservoir
Roanoke Arm (16)
Nutbush Arm (17)
Lamb
1972 (19)
Meander
1972 (21)
Mendota (22)
Michigan (Open
Waters) (23-A)
Lower Lake23~B)
Minnetonka
1969 (25)
1973 (26)
Potomac Estuary
Upper (28)
Middle (29)
Lower (30)
Redstone (31)
E
E-M
-
-
0
0
E
0
0
E
E->M
U-E
-
-
-
E
Phosphorus Mean
Loading, L(P) Depth, z
r\ \.^
(mg/m /yr) (m)
2030
5200
700
30
30
1200
140
140
500
100(180)k
85000
8000
1200
]440-1680
2.7
10 .3
8.2
4
5
12
84
84
8.3
8.3
4 .8
5 .1
7.2
4.3
Hydraulic
Loading, qg
(m/yr)c
4 .5
51.5
1.6
1.7
1.8
2 .7
2. 8
0 .84
1.3
1.3
120
28. 3
8.5
4.3-6.1
L(P)/qs
1 * ^
254
69.8
134
7.0
6.3
142
7 . 7
15.2
109
21.9(39
590
198
73.4
156
Mean
Secchi
Depth
(m)
1.0
1.1
1.2
2.2
3.0
3.0
-
1.5
. "t )kl . 8
0.6
0.9
1.6
1.6
Mean
Chlorophyll a
Concent rat ion
(ug/D
53f
13
21
3 (3)8
2 (l)g
10 (20)h
2
2
21
12
30-150
30-100
10-20
13e
-------
Table 23 (continued). US OECD DATA APPLIED TO VOLLEHWEIDER'S
PHOSPHORUS LOADING AND MEAN CHLOROPHYLL a CONCENTRATION
RELATIONSHIP
Water Body
Sallie
Sammamish
Shagawa
Stewart
Tahoe
East Twin
"3 1973
CO
1974
West Twin
1972
1973
1974
(32)
(33)
(34)
(35)
(36)
(39)
(40)
(41).
(43)
(44)
(45)
Twin Valley(46)
Virginia
Waldo
(47)
(48)
Trophic
State3
E
M
E
E
U-0
E
E
E
E
E
E
E
E
U-0
Phosphorus Mean
Loading, L(P) Depth, z
(mg/m /yr) (m)
1500-4200
700
700
4820-8050
50
700(700)k
500 (500)
700 (500)
400 (400)k
300 (200)
300 (300)
1740-2050
1150-1480
17
6.4
18
5 .7
1.9
313
5
5
5
4 .3
4.3
4. 3
3.8
1.7
36
Hydraulic
Loading, q
(m/yr)c
3.6-5.8
10
7.
23.
0 .
6 .
5 .
10
2 .
2 .
4 .
7.6-9
0.6-1
1.
1
8
45
2
6
7
4
3
.5
.9
7
L(P)
1 + ,
Mean
Secchi
/qs Depth
Jz/q (m)
(lean
Chlorophyll a
Concentration
(Pg/l)b
275
29.
52 .
211
4 .
59 .
45 .
41 .
65 .
53.
34 .
133
44 .
1.
9
0
0
6
8
0
4
4
9
6
8
3
2
1
28
1
2
1
2
2
2
1
1
28
.3
. 3
.4
.3
.6
.3
.9
.2
.8
.3
.5
.2
.0
5
15 (24)1
12e
< lg
26
22
28
40
23
28
19e
29e
< 1^
-------
Table 23 (continued). US OECD DATA APPLIED TO VULLi:ilWEIDER 'S
PHOSPHORUS LOADING AND MEAN CHLOROPHYLL a CONCENTRATION
RELATIONSHIP
I—'
co
Water Body
Washington
1957
1964
1971
19 7M
Weir
Wirtgra
EXPLANATION
Mean Mean
Phosphorus Mean Hydraulic i(pw Secchi Chlorophyll a
Trophic Loading, L(P) Depth, z Loading, q_ ' qs Depth Concentration
Statea (mg/ra2/yr)b (m) (m/yr)c " 1 + /z7q"s (m) (pg/l)b
(49) E 1200 33 13.8 34. 1 2.2 12
(50) E 2300 33 13.8 65.3 1.2 20
(51) M 430 33 13.8 12.2 3.5 6
(52) M i(70 33 13.8 13.4 3.8 - (4)
(53) M 140 6.3 1.5 30.6 1.9 8
(54) E 900 2.4 6 91.9 1.3
M = mesotrophic
0 = oligotrophic
U = ultra
Based on investigator's estimates.
"Hydraulic loading, q = z/t = hydraulic residence time = water body
volume (m )/annual inflow volume (m /yr).
( ) = Identification number for Figures 22, 23 and 24 (see Table 14)
-------
Table 23 (continued). US OECD DATA APPLICD TO VOLLFJ1WEIDER' S
PHOSPHORUS LOADING AND MEAN CHLOROPHYLL a CONCENTRATION
RELATIONSHIP
EXPLANATION (continued)
e
First two meters of water column.
Summer surface values.
^Euphotic zone.
v.
Growing season.
"'"Ice-free period.
-'Average value for August.
k
All data in parentheses represent data received by these reviewers from the principal investigators
after the completion of this report. Figure 22 is based on the original data reported by the
investigators and does not reflect these revised values. Examination of the revised data indicated
no significant changes in the overall conclusions concerning these water bodies.
(—'
10 Dash (-) indicates data not available.
-------
IUU
~
3
z
o
(£
1-
Z
LU
2 10
o
o
o|
1
^J
_J
X
Q.
O
tr
o
_i
u '
\j
H
LU
5
i
_*
E
UJ
z
<
1 1 1
LU
2
Oi
.1
: ' ' 28*
29 «/
* 14 /
43 /^
>^jl
"•• ^' fi- •"'
•" "^&>T>C.
... 34 30/ _.
26 |5A*J|; %31B35
r *s^x *22"
- 5I /A5"B 4 , „
• '06-A • 43 ^2
10 /S-B*33
19 X^^
0 /
^r
X" A
w 23~B
23-A
^r
/ • ANNUAL MEAN CHLOROPHYLL 0
A GROWING SEASON CHLOROPHYLL o
Xm CHLOROPHYLL o IN FIRST TWO METER
OF WATER COLUMM
•/ V SUMMER MEAN CHLOROPHYLL i
+ SUMMER SURFACE MEAN CHLOROPHYLL o_
36
48 A
/
—
* LOG [CHLOROPHYLL g] =076 LOG [(L(p)/qs)/d+./2/qs)] -0259
P-LOADING CHARACTERISTICS
WITHIN EXCEED
j TO1 FRANCF --_!_ i . . Tf\l FDAMfT --
^ i WLcnMix^c. -4- • ----- - --T1 • • ' 1 L/LtKANUb "' •
i i i t i i t i 1 i i i t i i i i 1 i i ill
10 100
S i i
100
(mg /m )
Figure 22.
US OECD Data Applied to Vol1enweider
Phosphorus Loading Characteristics and
Mean Chlorophyll a^ Relationship
199
-------
Examination of Figure 22 indicates the investigators have
used a variety of approaches for estimating the chlorophyll a
content of their water. Some reported values are summer means
while other values are annual means, Some values are means for
the euphotic zone while others are means for the first two meters
of the water column. Therefore, in a strict sense the reported
chlorophyll a data for the US OECD water bodies are not dire.ctly
comparable. "However, even with tnese limitations, there is rea-
sonable agreement (r = 0.77) between the predicted trophic states
of the US OECD water bodies, based on their position to the right
or left of the 10 mg/m^ permissible phosphorus concentration boun-
dary line and the investigator's subjective trophic state charac-
terizations. In general, the results of Figure 22 confirm the re-
sults indicated in the Vollenweider phosphorus loading diagram
(Figure 19).
Figure 22 also supports some of the possible phosphorus load-
ing estimate discrepancies indicated in Figures 14 and 15. For
example, based on its phosphorus loading characteristics and mean
chlorophyll a_ concentrations, Lake Weir plots in the eutrophic zone
in Figure 22, in disagreement with the mesotrophic condition indi-
cated by Brezonik and Messer (1975). This supports the possibility
that the phosphorus loading underestimation indicated in Figures 14
and 15 are in error. If, on the other hand, the phosphorus loading
estimates for Lake Weir are correct, then the level of chlorophyll
production per 'unit of input phosphorus must be higher in Lake Weir
than in other water bodies. This would support the idea of a differ-
ent phosphorus loading-algal response relationship in warm water
bodies compared to that found in water bodies in the north temperate
zones of the US. Furthermore, the relative closeness of Lake
Dogfish (10), Lake Lamb (19) and Lake Meander (31) to the 10 mg/m3
concentration mark in Figure 22 supports the possible phosphorus
loading underestimations indicated earlier in Figure 15 for these
water bodies. As indicated earlier, their reported phosphorus
loadings place them in the trophic zone of the Vollenweider phos-
phorus loading diagram (Figure 19) characteristic of ultra-
oligotrophic Lakes Tahoe and Waldo. However, Lakes Dogfish, Lamb
and Meander are clearly more productive, in terms of relative
chlorophyll a concentrations, than Lakes Tahoe and Waldo, support-
ing the phosphorus loading underestimation indicated in Figure 15
for these three water bodies.
In spite of the non-uniform computations of the mean
chlorophyll a concentrations used in Figure 22, the results of
this relationship between phosphorus loading characteristics,
(i.e., predicted in-lake phosphorus concentration - see Equation
20) and chlorophyll a concentrations indirectly support the
200
-------
validity of the Vollenweider phosphorus loading diagram criteria
illustrated in Figure 19.
US OECD PHOSPHORUS DATA APPLIED IN PHOSPHORUS LOADING AND
SECCHI DEPTH RELATIONSHIP
The use of the Secchi depth as an indicator of algal bio-
mass has recently been proposed by several investigators
(Edmondson, 1972; Carlson, 1974; Shapiro, 1975b; Shapiro et al.,
1975). The use of this parameter as an indicator of a water
body's trophic condition is based largely on the public's per-
ception of eutrophication problems. Remedial treatment programs,
including sewage diversion and advanced waste treatment, have
often been initiated because of the public's reaction to the
side effects of eutrophication, such as dense algal blooms or
decaying algal mats. As a result, water transparency or clarity
has probably become the most frequently cited all-around general
indicator of water quality. The higher the transparency of the
water body, the higher is thought to be the general water quality.
Obvious exceptions to this general rule would be water bodies
with high color content.
Edmondson (1972) has found a close relationship between Secchi
depth and algal biomass (expressed as chlorophyll concentration)
in Lake Washington. While there are likely some effects due to
light scattering by non-planktonic particles in the water, there is
a definite negative hyperbolic relationship between Secchi depth
and chlorophyll concentration, with the slope of the curve
steepest at the lower biomass levels. This indicates changes in
biomass, as reflected in chlorophyll concentrations, are more
easily detected in clear (i.e., oligotrophic) waters than in
eutrophic waters. Above approximately 20 yg/1 chlorophyll con-
centrations, at least in Lake Washington, a large increase in
mean chlorophyll does not produce a proportionately large
decrease in Secchi depth. This indicates that, above a certain
degree of eutrophication, Secchi depth readings lose sensitivity
as an indicator of changes in algal biomass, other than a low
Secchi depth indicating a relatively eutrophic condition of the
water body.
Even with this limitation, however, the use of Secchi depth
measurements as an indicator of a water body's algal biomass,
and hence general trophic condition, remains an easily measured
parameter, involving a minimum of time and cost. In addition,
its meaning is easily understood by the general public and is a
parameter which can be evaluated over time in correlation with
the general trophic condition of the water body.
As the algal biomass of a water body is related to its
nutrient flux, the Secchi depths of the US OECD water bodies were
examined as a function of their phosphorus loading characteristics
201
-------
in a manner analagous to that of chlorophyll a concentration
in Figure 22. In order to give the plot the same general slope
as expressed in Vollenweider's chlorophyll concentration versus
phosphorus loading characteristics, the reciprocal of the Secchi
depth was plotted versus the phosphorus loading expression,
(L(P)/qs)/(l+\/z;/qs) • The pertinent data was presented in Table
23. The US OECD eutrophication study data are presented in
Figure 23.
Examination of Figure 23 shows a definite relationship does
exist between Secchi depth and phosphorus loadings, with the
reciprocal of the Secchi depth increasing as a function of the
phosphorus loading. However, the slope is not as steep as that
indicated in Figure 22 between chlorophyll a_ concentration and
phosphorus loading characteristics. Particularly scattered are
the data sets for the oligotrophic and mesotrophic water bodies.
In an attempt to graphically produce a greater spread of
data, a semilog plot of the US OECD data was prepared. This is
illustrated in Figure 24. Examination of Figure 24 again shows
a relationship exists between these two parameters. As the
phosphorus loading increases, the reciprocal of the Secchi depth
also increases, with the steepest slope at the higher phosphorus
loading and lower Secchi depth values. However, the data sets
still exhibit considerable scatter. Unfortunately, there is not
a sufficient number of oligotrophic water bodies in the US OECD
eutrophication study to allow examination of this relationship,
using US OECD data, other than on a general qualitative basis.
As a nonlinear relationship exists between Secchi depth and
chlorophyll (Edmondson, 1972), it is not surprising to see a
nonlinear relationship existing between phosphorus loading and
Secchi depth, particularly since the algal biomass in a water
body is generally a function of the intensity of the nutrient
flux. The use of this relationship as a tool for assessing the
expected change in water quality resulting from a changed
phosphorus load will be discussed in a later section of this
report.
US OECD PHOSPHORUS DATA APPLIED IN DILLON'S PHOSPHORUS
LOADING-PHOSPHORUS RETENTION AND MEAN DEPTH RELATIONSHIP
A different type of phosphorus loading diagram was subsequently
developed by Dillon (1975; Vollenweider and Dillon, 1974). This
loading diagram considers not only the phosphorus loading to a
water body, but also the capacity of the water body to retain
the input phosphorus. Vollenweider's earlier relationships do
this implicitly as a function of mean depth, z, or hydraulic
loading, qs. Derivation of Dillon's model was presented in an
earlier section of this report. Dillon's relationship allows
one to consider the effects of flushing time, phosphorus loading
and phosphorus retention on the degree of fertility of a water
202
-------
INVESTIGATOR-INDICATED
TROPHIC STATE:
• -EUTROPHIC
A-MESOTROPHIC
O-OLIGOTROPHIC
KD
O
CO
CL
LJ
Q
I
O
O
en
o i
2I
52
33
29*
• .14
50 17 47
«22
12
o48 o36
001
0.
1 1 1 1 1 1
1 1 1 1 1 1 1 1 1
Figure 23
10
100
1000
(mg/m3)
US OECD Data Applied to Phosphorus Loading and Secchi Depth
Relationship (Log-Log Scale).
-------
1.4
1.2
1.0
0.8
Q.
UJ
O
a:
O
O
0.4
0.2
INVESTIGATOR-INDICATED
TROPHIC STATE'.
• -EUTROPHIC
A- MESOTROPHIC
O- OLIGOTROPHIC
19
O
I0c
2U
28
.29
50 ..
• •
47-
39
26 5
• •
A 53
\30 »31
• 13
45 OIO
44*
.22
51 A33
^;
'52
'12
48
36
I I I Mil
I 10 100
(L(P)/qs)/(l+v/I7q;)
(mg/m3)
1000
Figure 24.
US OECD Data Applied to Phosphorus
Loading and Secchi Depth Relation-
ship (Semi log Scale).
204
-------
body. A main feature of Dillon's model is that since a water
body's phosphorus retention capacity is a function of its flush-
ing rate, consideration of the phosphorus retention coefficient
allows for a more accurate determination of the effects of an ex-
tremely fast or slow hydraulic flushing rate on the phosphorus
loading-trophic response relationship.
Dillon's phosphorus loading diagram is presented in Figure
25, The pertinent US OECD data are presented in Table 24. If
a data range was reported for a water body, the mean value was
used in all calculations. Phosphorus concentration boundary con-
ditions of 10 yg/1 and 20 yg/1 (Sawyer, 1947; Sakamoto, 1966;
Dillon, 1975) correspond to Vollenweider's permissible and ex-
cessive loading lines, respectively (Figure 19). The trophic
state associations are similar to those in Figure 19.
As was found with Vollenweider's phosphorus loading diagram
(Figure 19), water bodies of similar trophic character plot in the
same relative area in Dillon's loading diagram (Figure 25). There
is generally good agreement between the predicted trophic states
in Dillon's loading diagram and the US OECD investigator-indicated
trophic states. In addition, Figure 25 supports the possibility
of a phosphorus loading underestimation for Lakes Dogfish (10),
Lamb (19), and Meander (21), indicated in earlier diagrams.
In general, Dillon's phosphorus loading diagram appears to
be a valid procedure for establishing the relative trophic con-
ditions and phosphorus concentrations of water bodies . It also
indirectly supports the validity of the Vollenweider phosphorus
loading relationship expressed in Figure 19. It should be men-
tioned, however, that while Dillon's phosphorus loading diagram
is a substantial improvement over Vollenweider's original phos-
phorus loading and mean depth diagram (Figure 5), it does not
appear to offer any significant improvement over the information
obtained with Vollenweider's modified phosphorus loading and
mean depth/hydraulic residence time loading diagram (Figure 19).
Rather, it is an alternate method for predicting the relative
degree of fertility of a water body. In fact, Dillon (Vollenweider
and Dillon, 1974) offers his model as a simple method for predict-
ing phosphorus concentrations rather than as a substitute for
Vollenweider's modified phosphorus loading diagram. It should
be mentioned that Vollenweider's relationship used in Figure 19
(i.e., Equation 9) assumes that R(P) is expressed solely through
the hydraulic residence time, i^. However, Vollenweider's rela-
tionship likely would not indicate if any other parameters affected
R(P). In this regard, Dillon's relationship may be more complete.
205
-------
E
X,
O>
tr
EUTROPHIC
INVESTIGATOR -INDICATED
TROPHIC STATE:
• -EUTROPHIC
A-MESOTROPHIC
O-OLIGOTROPHIC
OLIGOTROPHIC
0.01
10 100
MEAN DEPTH(m)
1000
Fi gure 25.
US OECD Data Applied to Dillon
Phosphorus Loading - Phosphorus
Retention and Mean Depth
Relationshi p
206
-------
Table 24. US OECD DATA APPLIED TO DILLON'S PHOSPHORUS LOADING-
PHOSPHORUS RETENTION AND MEAN DEPTH RELATIONSHIP
r-o
o
Trophic
Water Body State3
Blackhawk (l)e
Brownie (2)
Calhoun (3)
Camelot-Sherwood ( 4 )
Canadarago
Cayuga (6)
Cedar (7)
Cox Hollow (8)
Dogfish (10)
Dutch Hollow (11)
George (12)
Harriet (13)
Isles (14)
Kerr Reservoir
Roanoke (16)
Nutbush (17)
Lamb (19)
Meander (21)
Mendota (22)
E
E
E
E
E
M
E
E
0
E
0-M
E
E
E-M
0
0
E
Phosphorus
Retention ,
Coefficient, R
0 .
0.
0.
0.23
0.
0.
0.
0.41
0.
0.
0.
0.
0 .
0.
0.
0.
0.
0.
41
59
66
-0.27
44
75
64
-0.46
65
57
74
61
44
31
69
60
62
68
Phosphorus
Loading, L
(g/m /yr)
2 .
1
0
1-2.3
.18
. 86
2. 35-2.68
0
0
0
. 8
.8
. 35
1.62-2 .08
0
.02
0.95-1.01
0
0
2
5
0
0
0
1
.07
.71
.03
.2
. 7
. 03
.03
. 2
Flushing
Rate, p
(yr-V
2
0
0
7.
1
0
0
1.
0
0
0
0
1
5
0
0
0
0
.0
. 5
.28
1-11.1
.67
.12
.30
4-2. 0
.29
. 56
.12
.42
.67
.0
.20
.44
.37
.22
L(l-R)/p
2
(mg/m )
0
0
1
0
0
0
0
0
0
0
0
0
0
1
0
0
1
.70
.98
.05
.21
.27
.41
.61
.02
.75
.15
.66
.69
.72
.08
.03
.03
.73
Mean Depth, z
(m)
4
6
10
3
7
54
6
3
4
3
18
8
2
10
8
4
5
12
.9
.8
.6
. 0
.7
.1
.8
.0
.0
.8
. 7
. 3
.2
.0
.0
-------
Table 24 (continued). US OKCD DATA APPLIED TO DILLON'S PHOSPHORUS
LOADING-PHOSPHORUS RETENTION AND MEAN DEPTH RELATIONSHIP
Water Body
Trophic
State3
Phosphorus
Retention ,
Coefficient, R
Phosphorus
Loading, L
(g/m2/yr)C
Flushing
Rate , p
L(1-R)/P Mean Depth, ?.
(mg/m ) (m)
Michigan (Open Waters)
1971 (23-A)
1974 (24-A)
1971 (23-B)
1974 (24-B)
0
0
0
0
0.
0.
0.
0.
84
84
91
91
0.
0 .
0 .
0.
14
1
14
10
0 .
0 .
0 .
0.
03
03
01
01
0
0
1
0
.72
.51
.27
.91
84
84
Lower Lake Minnetonka c
1969 (25)
1973 (26)
^J Potomac Estuary
<=> Upper (28)
Middle (29)
Lower (30)
Redstone (31)
Sallie (32)
Sammamish (33)
Shagawa (34)
Stewart (35)
Tahoe (36)
East Twin
]972 (39)
1973 (40)
1974 (41)
E
E^M
U-E
-
-
-
E
E
M
E
E
U-0
E
E
E
0.
0.
0.
0.
0.
o . M r,
0. 51
0.
0.
0.
0 .
0.
0.
0.
72f
72f
17
3
48
-0.50
-0.57
57
47
22
47
49
41
0.
0.
85
8
I.
1.44-
1.5-
0.
n .
4.82-
0.
0.
0.
0.
5
1 (0.2)1
2
1. 68
4.2
7
7
8 .05
OS
7 (0.7V
5 (0.5)
7 (0.8)
0.
? 0.
25
5.
1.
1. 0-
16
16
56
18
1.4
0. 56-0.91
0.
1.
12 .
0.
5 1.
1 .
? .
56
25
5
001
25
11
0
0
0
2
1
0
0
1
0
0
0
1
0
0
0
.88
.18 (0.35)g
.83
.01
.53
.68
.78
.54
. 30
. 40
.53
30 (0.30)g
.23 (0.23)
21 (0.24)
8 .
8 .
4 .
5.
7 .
4.
6.
18
5.
1.
313
5.
5.
5.
3
3
8
1
2
3
4
7
9
0
0
0
-------
Table 24 (continued). US OP.CD DATA APPLIED TO DII,LOU'S PHOSPHORUS
LOADING-PHOSPHOPUS RrTrHTICHI AtlD MEAN DEPTH RELATIONS!! IP
Trophic
Water Body State3
West Twin
1972 (43)
1973 (44)
1974 (45)
Twin Valley (46)
Virginia (47)
Waldo (48)
Washington
1957 (49)
1964 (50)
1971 (51)
1974 (52)
Weir (53)
Wingra (54)
EXPLANATION:
a
E
E
E
E
E
U-0
E
E
M
M
M
E
Phosphorus
Retention .
Coefficient, R
0.
0.
0.
0. 39
0.49
0.
0.
0.
0.
0.
0.
0.
56
57
50
-0.41
-0.63
82
61
61
61
61
67
39
Phosphorus Flushing
Loading, L Rate, p
(g/m /yr) (yr )
0.
0.
0.
1.74-2
1.15-1
0.
1 .
2.
0.
0.
0.
0.
4 (0.
3(0.
3(0.
.05
.48
017
2
3
43
47
14
9
4)g o
2) 0
3) i
2.0-
0. 36-
0
0
0
0
0
0
2
.62
.56
.0
2 . 5
1. 1
.05
.42
.42
.42
.42
. 24
. 5
L(1-R)2/P Mean Depth, ?,
(mg/m ) (m)
0
0
0
0
0
0
1
2
0
0
0
0
28 (0.28)g
;23<°.K>
.15(0.15)
.51
.80
.06
.11
.14
.40
.44
.20
. 22
4
4
4
3
1
36
33
33
33
33
6
2
. 3
. 3
.3
.8
. 7
. 3
.4
E = eutrophic
M = raesotrophic
0 = oligotrophic
U = ultra
-------
Table 24 (continued). US OECD DATA APPLIED TO DILLON'S PHOSPHORUS
LOADING-PHOSPHORUS RETENTION AND MEAN DEPTH RELATIONSHIP
EXPLANATION (continued)
Retention coefficient, R= 1 / ( 1 + Jp((J ) , where p = 1/T = I/hydraulic residence time ( Vollenweider ,
1975a; 197Ba). See Table 20 for hydrauTic residence time for US OECD water bodies.
Flushing rate, p = (discharge (m /yr) /water body volume (m ) = I/T ).
Based on investigator's estimates.
Flushing rate, p = (discharge (m /
p
Identification number for Figure 25 (See Table 14).
Whole lake value .
£
Data in parentheses represents data received by these reviewers from the principal investigators
subsequent to completion of this report. Figure 25 is based on the original data reported by
the investigators and does not reflect the revised data. Examination of the revised data
indicated no significant changes in the overall conclusions concerning these water bodies.
-------
US OECD PHOSPHORUS DATA APPLIED IN LARSEN AND MERCIER'S INFLUENT
PHOSPHORUS AND PHOSPHORUS RETENTION RELATIONSHIP
Larsen and Mercier (1976) proposed another alternate method
of examining the nutrient loading-trophic response relationships
in water bodies. Consistent with the view that the phosphorus
concentration in a water body, rather than the phosphorus loading
to the water body, ultimately controls algal blooms and the
eutrophication process (Vollenweider, 1968; Vollenweider and Dillon,
197M-), Larsen and Mercier (1976) devised a phosphorus loading dia-
gram which related a water body's trophic state to its influent
phosphorus concentration, as modified by its phosphorus retention
coefficient, R(P). They described the mean phosphorus concentration
in a water body as the relationship between its mean influent
phosphorus concentration and^ its ability to assimilate this influent
phosphorus . The derivation of this approach was presented in an
earlier section of this report. The Larsen-Mercier approach of
utilizing the water body influent phosphorus concentrations rather
than the phosphorus loading may be particularly important for water
bodies that receive a substantial part of their key limiting nu-
trient load in a form that is not immediately available for aquatic
plant growth. An example would be the phosphorus present in ero-
sional material. In such cases, the phosphorus loading would not
accurately predict the ultimate aquatic plant growth within the
water body. As indicated earlier, Cowen et al. (1976a) have found
that typically up to 20 percent of the norfsbluble orthophosphate
present in US tributaries to Lake Ontario is available for algal
growth in Lake Ontario.
Curves delineating trophic zones can be drawn on Larsen and
Mercier's loading diagram, analogous to the trophic zones in the
Vollenweider phosphorus loading diagram (Figure 19). The relative
degree of eutrophy or oligotrophy of a water body is a function of
its vertical displacement above or below the permissible phosphorus
concentration line. The permissible and excessive phosphorus con-
centration lines correspond to the 10 yg/1 and 20 yg/1 limits
determined by Sawyer (1947) and Sakamoto (1966), respectively.
They are included in the loading diagram, according to Larsen and
Mercier (1976), mainly for "illustrative purposes."
The Larsen and Mercier diagram, containing the US OECD water
bodies, is presented in Figure 26. The pertinent US OECD data
are presented in Table 25. If a data range was reported for a
water body, the mean value was used in all calculations. General-
ly, the results of Figure 26 agree with those of Figures 22 and 25.
In most cases, the predicted trophic states are in agreement with
those reported by the US OECD investigators. A feature of Larsen
and MercierTs relationship is that it allows one to relate the mean
phosphorus concentration of a water body to both its phosphorus
loading and its mean influent phosphorus concentration. If two
of the above parameters are known, one can use the interrelation-
ship between the three components to determine the value of the
third parameter.
211
-------
g
i-
K
H
z
Ul
o —
r>
tr
o
x
Q.
O
X
Q.
UJ
U.
100
20
10
0
._-,,- - -!- INDICATED
TROPHIC STATED
• -EUTROPHIC
A- MESOTROPHIC
O- OLIGOTROPHIC
J I I I
1
1
OLIGOTROPHIC
I i
0.2 0.4 0.6 0.8 1.0
PHOSPHORUS RETENTION COEFFICIENT. R
Figure 26. US OECD Data Applied to Larsen and Mercier
Influent Phosphorus and Phosphorus Retention
Relationship
212
-------
Table 25. US OECD DATA APPLIED TO LARSEN AND MERCIER'S
INFLUENT PHOSPHORUS CONCENTRATION AND
PHOSPHORUS RETENTION RELATIONSHIP
Water Body Trophic State3
Blackhawk (l)d
Brownie (2)
Calhoun (3)
Camelot-Sherwood (4)
Canadarago (5)
Cayuga (6)
Cedar (7)
Cox Hollow (8)
Dogfish (10)
Dutch Hollow (11)
George (12)
Harriet (13)
Isles (14)
Kerr Reservoir
Roanoke (16)
Nutbush (17)
Lamb (19)
Meander (21)
Mendota (22)
Michigan (Open Waters)
(23-A)
(24-A)
(23-B)
(24-B)
Lower Lake Minnetonka
1969 (25)
1973 (26)
Potomac Estuary
Upper (28)
Middle (29)
Lower (30)
Redstone (31)
E
E
E
E
E
M
E
E
0
E
0-M
E
E
E-M
-
-
0
0
E
0
0
0
0
E
E-*M
U-E
-
-
E
Phosphorus
Retention .
Coefficient ,R
0.41
0.59
0 .66
0.25
0 .44
0.75
0 .64
0 .44
0 .65
0 .57
0.74
0 .61
0 .44
0.31
0.69
0 .60
0.62
0 .68
0.84
0 .84
0 .91
0.91
0.728
0.72e
0.17
0 .30
0 .48
0 .48
Influent Phosphorus
Concentration, [p]
(yg/Dc
227
347
297
92 .0
62.4
127
194
285
18.2
576
32
192
451
101
438
17.6
16.7
444
50
36
167
119
417
76.9- (138 )f
708
283
142
300
213
-------
Table 25 (continued). US OECD DATA APPLIED TO LARSEN AND
MERCIER'S INFLUENT PHOSPHORUS CONCENTRATION AND
PHOSPHORUS RETENTION RELATIONSHIP
Phosphorus
Retention ,
Water Body Trophic State3 Coefficient ,R
Sallie (32)
Sammamish (33)
Shagawa (34)
Stewart (35)
Tahoe (36)
East Twin
1972 (39)
1973 (40)
1974 (41)
West Twin
1972 (43)
1973 (44)
1974 (45)
Twin Valley (46)
Virginia (47)
Waldo (48)
Washington
1957 (49)
1964 (50)
1971 (51)
1974 (52)
Weir (53)
Wingra (54)
EXPLANATION:
Investigator-indicated
E = eutrophic
M = mesotrophic
0 = oligotrophic
U = ultra
E
M
E
E
U-0
E
E
E
E
E
E
E
E
U-0
E
E
M
M
M
E
trophic state :
0 .54
0 .57
0 .47
0 .22
0 .96
0 .47
0.49
0 .41
0.56
0 .57
0 .50
0 .40
0.56
0 .82
0.616
0.61e
0 .61e
-0 .61e
0 .67
0.39
Influent Phosphorus
Concentration, [p]
(yg/l)c
606
70
98 .6
270
111
113
89 .3
70.0
148
125
69 .8
222
1052
10 .1
87.0
167
31.2
34.0
46.7
150
(113)f
(89.3)
( 8 0 '. 0 )
(148)
(83.8)
(69.8)
214
-------
Table 25 (continued). US OECD DATA APPLIED TO LARSEN AND
MERCIER'S INFLUENT PHOSPHORUS CONCENTRATION AND
PHOSPHORUS RETENTION RELATIONSHIP
EXPLANATION (continued).
Retention coefficient, R = I/ (1+ /JO > where p^ = I/TW = I/hydraulic
residence time (Vollenweider, I975a; 1976a). See Table 20
for hydraulic residence times of US OECD water bodies.
cMean influent phosphorus concentration, [P] = L(P)/qs,
where L(P) = phosphorus loading (mg/m^/yr) and qs =
hydraulic loading = Z/TU, where z = mean depth (m) and
To) ~ hydraulic residence time. See Table 15 for influent
phosphorus concentrations for US OECD water bodies.
Identification number for Figure 26 (see Table 14).
eWhole lake value.
All -data in parentheses represents data submitted to these reviewers
from the principal investigators subsequent to the completion of
this report. Figure 26 is based on the original data submitted by
the investigators and does not reflect the revised data. Exam-
ination of the revised data indicated no significant changes in
the overall conclusions concerning these water bodies.
215
-------
In summary, the results of Vollenweider's phosphorus loading
characteristics and mean chlorophyll a concentration relationship
(Figure 22), Dillon's phosphorus loading/phosphorus retention and
mean depth relationship (Figure 25) and Larsen and Mercier's
influent phosphorus concentration and phosphorus retention rela-
tionship (Figure 26), all either directly or indirectly support
Vollenweider's approach for estimating critical phosphorus loads
for lakes and impoundments. Furthermore, they generally support
the possible errors in the phosphorus loading estimates suggested
in Figures 14 and 15. This supports both the validity of the
Vollenweider relationship illustrated in Equation 26 , and the
use of watershed land use nutrient export coefficients as methods
of estimating phosphorus loadings and of checking the reasonable-
ness of calculated phosphorus loadings. Finally, these three
models offer a certain capacity, based on the phosphorus loadings,
for predicting the mean phosphorus and mean chlorophyll a_ concen-
trations in a water body. ~~
216
-------
SECTION X
CORRELATIONS BETWEEN NUTRIENT LOADINGS
AND EUTROPHICATION RESPONSE PARAMETERS
This section of this report is devoted to analysis of the cor-
relations between the nutrient loading for the US OECD water bodies
and their eutrophication response to these loadings. A list of
suggested correlations was developed by R. Vollenweider and mem-
bers of the OECD Eutrophication Technical Bureau and was dis-
tributed to the OECD eutrophication principal investigators. Many
of these suggested correlations could not be made for the lakes in
the US OECD eutrophication study since only a limited number of
investigators had data for all of the parameters required to make
these correlations. Included in the list of suggested eutrophica-
tion response parameters were maximum rates of primary production
and respiration, stratified period average chlorophyll a_ content,
average epilimnetic concentration of particulate phosphorus , areal
hypolimnetic oxygen deficit, maximum oxygen surplus , duration of
algal blooms and maximum rate of development of bloom. These data
were not reported for the US OECD water bodies . In some instances,
insufficient data were available to prepare a potentially meaning-
ful plot of the data. For some parameters, the correlations have
been presented and discussed in previous sections of this report .
This section of this report presents what might be considered mis-
cellaneous correlations which are thought to be of lesser importance
than those presented in other parts of the report or where there
were insufficient data to justify a more intensive discussion of
the relationship. A listing of the various correlations analyzed
in this report is presented in Table 26.
Before presenting the results of these correlations between
nutrient loadings and eutrophication response parameters, the
reader should be made aware of several factors which limit the
values of these analyses. First, as indicated in an earlier sec-
tion of this report (Table 11), the various response parameters
(i.e., nutrient concentrations) were measured using a variety of
analytical techniques. In addition to differing analytical pro-
cedures, the sampling methodologies also varied widely,which could
affect the results obtained for a given response parameter measure-
ment. As indicated in the Summary Sheets (Appendix II), the US
OECD water bodies were sampled at a variety of depths and locations
and on differing dates. For example, some water bodies were
sampled frequently all year, others were sampled frequently part
of the year and less frequently the rest of the year, while still
217
-------
Table 26. LIST OF CORRELATIONS EXAMINED IN US OECD
WATER BODIESa
I. Phosphorus Loading and:
A. annual mean chlorophyll a (Figure 27);
B. annual mean Secchi depth (Figure 28);
C. annual mean total phosphorus (Figure 29);
D. annual mean dissolved phosphorus (Figure 30);
E. annual primary productivity (Figure 31);
F. annual total primary production (Figure 32);
G. growing season epilimnetic chlorophyll a (Figure 33);
H. growing season epilimnetic total phosphorus (Figure 34);
I. growing season epilimnetic dissolved phosphorus
(Figure 35);
J. growing season epilimnetic primary productivity
(Figure 36) ;
K. spring overturn total phosphorus (Figure 37);
L. spring overturn dissolved phosphorus*
II. Nitrogen Loading and:
A. annual mean chlorophyll a (Figure 38);
B. annual mean Secchi depth (Figure 3S);
C. annual mean inorganic nitrogen (Figure 40);
D. annual primary productivity (Figure 41);
E. annual total primary production (Figure 42);
F. growing season epilimnetic chlorophyll a (Figure 43);
G. growing season epilimnetic inorganic nitrogen (Figure 44);
H. growing season epilimnetic primary productivity
(Figure 45);
I. spring overturn inorganic nitrogen (Figure 46).
III. Annual Mean Total Phosphorus and:
A. annual mean chlorophyll a (Figure 47);
B. annual mean Secchi depth (Figure 43);
218
-------
Table 26 (continued). LIST OF CORRELATIONS EXAMINED
IN US OECD WATER BODIES
C. annual mean dissolved phosphorus (Figure 49);
D. annual primary productivity (Figure 50);
E. growing season epilimnetic chlorophyll a (Figure 51);
F. growing season epilimnetic primary productivity
(Figure 52);
G. spring overturn total phosphorus (Figure 53).
IV. Growing Season Epilimnetic Total Phosphorus and:
A. growing season epilimnetic chlorophyll a (Figure 54);
B. growing season epilimnetic primary productivity
(Figure 55).
V. Spring Overturn Total Phosphorus and:
A. growing season epilimnetic chlorophyll a_ (Figure 56);
B. growing season epilimnetic total phosphorus (Figure 57);
C. growing season epilimnetic dissolved phosphorus
(Figure 58) .
VI. Annual Mean Dissolved Phosphorus and:
A. annual mean chlorophyll a (Figure 59);
B. annual primary productivity (Figure 50);
C. spring overturn dissolved phosphorus (Figure 61).
VII. Growing Season Epilimnetic Dissolved Phosphorus and:
A. growing season epilimnetic chlorophyll a_ (Figure 62).
VIII. Spring Overturn Dissolved Phosphorus and:
A. growing season epilimnetic chlorophyll a (Figure £3);
B. growing season epilimnetic dissolved phosphorus
(Figure 6^;;
C. growing season epilimnetic primary productivity*
219
-------
Table 26 (continued). LIST OF CORRELATIONS EXAMINED
IN US OECD WATER BODIES
IX. Annual Mean Inorganic Nitrogen and:
A. annual mean chlorophyll a (Figure 65);
B. annual mean Secchi depth (Figure 66);
C. annual primary productivity (Figure 67);
D. growing season epilimnetic chlorophyll a (Figure 68);
E. growing season epilimnetic primary productivity
(Figure 69);
F. spring overturn inorganic nitrogen*
X. Growing Season Epilimnetic Inorganic Nitrogen and:
A. growing season epilimetic chlorophyll a_ (Figure 70)
B. growing season epilimnetic primary productivity
(Figure 71).
XI. Others^:
A. annual primary productivity and annual mean chlorophyll a
(Figure 72) ;
B. annual mean chlorophyll a and annual mean Secchi depth
~ (see Figures 77 and 78 )j
C. annual primary productivity and mean Secchi depth
(Figure 73);
D. growing season mean primary productivity and growing
season mean chlorophyll a (Figure 7U);
E. annual mean daily primary productivity and annual mean
chlorophyll a (Figure 75);
F. annual mean daily primary productivity and annual mean
areal chlorophyll a (Figure 75).
aData taken from Summary Sheets (Appendix II).
Insufficient data available.
220
-------
others were sampled infrequently all year. Also, some reported
mean values were arithmetic means of several sampling depths,
others were mean values integrated over the sampling depths, while
still others were surface or epilimnetic mean values. As discussed
in an earlier section, these factors can all contribute to an
erroneous "mean" value for a given response parameter measurement.
It is not possible to determine the extent of possible errors in
the parameters used in the correlations. This section presents
a general idea of the correlation(s) that may exist between nu-
trient loads and eutrophication response parameters in the US OECD
water bodies. No statistical evaluation of the correlation data
was undertaken. This report is limited to a simple visual examina-
tion of the correlations in a graphical form for obvious trends.
A 'correlation' as used in this section of the report indicates
that a relationship, either positive or negative, appears to
exist between two parameters on the basis of a visual inspection
of a plot of these two parameters. No attempt is made in these
plots to indicate the particular water body responsible for the
data. All data used in these plots are available in Appendix II.
For some plots, the investigator-indicated trophic status is pre-
sented. For others, where there are obvious differences in the
types of data for some parameters, this is also indicated on the
plot .
PHOSPHORUS LOADINGS
Although there is a large amount of scattering of the data,
there is a correlation observed between phosphorus loading and
mean chlorophyll a (Figure 27). The scatter in this diagram, as
well as all other~correlations examined in this section, is partly
due to sampling and analysis variability, as indicated earlier.
In addition, the 'mean' chlorophyll a consisted of annual means,
summer means and annual mean chlorophyll in the upper two meters
of the water column. As algal growth is dependent on the loading,
the correlation is expected. However, there usually is no clear
correlation between phosphorus loading and the resulting algal
biomass (as indicated by chlorophyll a content) in a water body
(Vollenweider, 1968; Vollenweider and Dillon, 1974). It depends
on a number of factors discussed earlier, such as the mean depth
of the water body and its hydraulic residence time. Consequently,
Figure 22, which incorporates the phosphorus loading to a water
body, as modified by its assimilative capacity (i.e., (L(P)/qs)/
(1+ (TW) , is a much better indicator of the phosphorus loading-
chlorophyll response of a water body. Vollenweider (1976a) has
shown a good correlation between these two parameters. The US
OECD water bodies also show a good correlation (Figure 22).
There is a correlation between phosphorus loading and mean
Secchi depth (Figure 28). The relationship is a negative hyper-
bolic function on this semi-log plot, although it exhibits a cer-
tain degree of scatter. A negative relationship between Secchi
depth and chlorophyll a has been reported by Edmondson (1972)
and Carlson (1974). STnce phosphorus loading is correlated with
221
-------
lOOr-
O>
ol
10
ro
ro
i-o
°
o:
O
—1
X
0
u
O.I
0.01
I 1 I 1 I I i i
Annual Mean Concentration
Upper Two Meters of Water Column
Summer Mean Concentration
i i I i i i i i
0.1
I
10
PHOSPHORUS LOADING (gP/mz/yr)
Figure 27. Phosphorus Loading and Mean Chlorophyll a
Relationship in US OECD Water Bodies
-------
ISO
ro
CO
Q_
UJ
2 O
2 ^
< LJ
(f)
LJ
ou
25
20
15
10
5
*
4
3
2
1
O O 1 1 1 1
investigator -Indicated
— Trophic State i
— • Eutrophic
A Mesotrophic
~~ O O Oligotrophic
;
O
- 0 . •
" ° O %.
° ° •* • •
~ *• • 5* *
i 1 1 1 1 1 nj i 1 1 1 1 11 ii i 1 1 1 1 1 1 ii i 1 1 1 ii H) i it
i
—
—
—
1 1 in
0.01
O.I
10
100
1000
PHOSPHORUS LOADING (gP/mVyr)
Figure 28. Phosphorus Loading and Mean Secchi Depth
Relationship in US OECD Water Bodies
-------
chlorophyll (Figure 22) and chlorophyll Is correlated with Secchi
depth, then a correlation should, and does, exist between phos-
phorus loading and Secchi depth. This relationship will be used
in a following section of this report to indicate how changes in
water quality can be related to changes in phosphorus loadings to
a water body.
A positive correlation exists between phosphorus loading and
mean total phosphorus in the water body (Figure 29). Although
there is considerable data scatter, this correlation is not un-
expected since the total phosphorus content of a water body will
usually be a function of the input phosphorus. Contrastingly,
there is not a readily observable correlation between phosphorus
loading and the mean dissolved phosphorus concentrations in the
US OECD water bodies (Figure 30), in view of the considerable
scatter of the data. This lack of correlation is expected since
dissolved phosphorus is the algal-available phosphorus form and
will be readily assimilated by the algal population in a water
body. It is expected that, in general, the available nutrients,
both phosphorus and nitrogen, will not show a good correlation
with any of the parameters examined in this section. The avail-
able nutrient concentration will increase and decrease in a water
body, depending on the algal growth dynamics which fluctuate con-
siderably during the annual cycle.
There appears to be a positive correlation between areal
phosphorus loading and mean annual primary productivity (Figure 31)
although the data are scattered and limited. In general, correla-
tions between primary productivity and both nutrient loadings and
concentrations, although usually present, were marked by consider-
able data scatter. This rendered this eutrophication response
parameter of limited value. In addition, the question of macro-
phyte and attached algal primary production was not addressed in
this study. In contrast with primary productivity, there is no
readily observable correlation between phosphorus loading and
total primary production (i.e., g C/yr in the water body) in the
US OECD water bodies (Figure 32). The total production, as a
function of phosphorus loading, appears to vary widely.
A positive correlation appears to exist between phosphorus
loadings and the growing season epilimnetic concentrations of
both chlorophyll a and total phosphorus (Figures 33 and 34, re-
spectively). (Note: the growing season, as used in this report,
was the period between May and October. However, the growing
season varied considerably between water bodies, being less for
some water bodies and considerably longer for others such as
the Kerr Reservoir and Lake Weir. Since such differences in
growing season could not be standardized, all "growing season"
values, regardless of length of growing season, were assumed to
be equivalent in the correlations). By contrast, there is no
correlation between phosphorus loading and the growing season
dissolved phosphorus concentration (Figure 35). As indicated
above, this is not unexpected since the dissolved phosphorus con-
centrations will vary as a function of algal growth, rather than
224
-------
ro
NJ
a.
a>
CE
O
I
z
UJ
O.I
0.01
(85)
**
• Annual Mean Value
• Ice-Free Period Mean Value
A Summer Mean Value
0.001
i i i i t i i i
i i i i i i i i
i t i i i 1 1
0.01 O.I
10
PHOSPHORUS LOADING (gP/rn/yr)
Figure 29. Phosphorus Loading and Mean Total Phosphorus
Relationship in US OECD Mater Bodies
-------
ro
r-o
cn
en
£
CO
13
oc
o
Q.
CO
O
X
CL
Q
UJ
O
CO
CO
UJ
O.I
0.01
0.001
Investigolor - Indicated
Ttophic Slate'.
• Eulrophic
A Mesotrophic
O Oligolrophic
•%
O
A
A
A
i i i i i i
OJOI
O.I
10
PHOSPHORUS LOAD ING (gP/mVyr)
Figure 30. Phosphorus Loading and Mean Dissolved Phosphorus
Relationship in US OECD Water Bodijes
-------
o
o>
r 100
o
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0.01
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PHOSPHORUS LOADING(gP/mz/yr)
Figure 31. Phosphorus Loading and Primary Productivity
Relationship in US OECO Water Bodies
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PHOSPHORUS LOADING (gP/m/yr)
Figure 32. Phosphorus Loading and Total Primary Production
Relationship in US OECD Water Bodies
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PHOSPHORUS LOADING (gP/rri /yr)
Figure 33. Phosphorus Loading and Growing Season Epllimnetic
Chlorophyll a Relationship In US OECD Water Bodies
-------
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PHOSPHORUS LOADING (gP/mVyr)
Figure 34. Phosphorus Loading and Growing Season Epilimnetic
Total Phosphorus Relationship in US OECD Water
Bodies
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PHOSPHORUS LOADING (gP/mVyr)
Figure 35. Phosphorus Loading and Growing Season EpHimnetic
Dissolved Phosphorus Relationship in US OECD
Water Bodies
-------
phosphorus supply. It is not clear whether there is a correlation
between phosphorus loading and growing season primary productivity
(Figure 36) mainly because of scarcity of data. The growing sea-
son primary productivity was not measured in most US OECD water
bodies. There appears to be a poor correlation between phosphorus
loading and the spring overturn total phosphorus (Figure 37), al-
though there is also a scarcity of data for this correlation.
This is somewhat surprising since the total phosphorus throughout
the year should generally be a function of the input phosphorus.
There are not sufficient data available to examine the correlation
between phosphorus loading and spring overturn dissolved phos-
phorus. A reasonably good correlation should be found for these
two parameters for lakes which normally have ice cover during the
winter.
NITROGEN LOADINGS
It should be noted before examining the correlations between
nitrogen loadings and eutrophication response parameters that
most of the US OECD water bodies are phosphorus-limited (Table 9)
with respect to algal growth requirements. Nitrogen loadings
were not reported for a number of the US OECD water bodies with
the result that the US OECD data base for nitrogen loads is less
extensive than that for phosphorus loads . The application of any
of the correlations in this section for providing justification
for a certain type of eutrophication control measure should be
made with caution.
A positive correlation was found between nitrogen loading and
mean chlorophyll a (Figure 38). The correlation _is very similar
to that seen between phosphorus loading and chlorophyll a
(Figure 26). There is an order of magnitude increase on~the load-
ing axis of the graph, but the relative positions of the water
bodies are similar. This illustrates the relatively constant in-
put of nitrogen relative to phos-Dho^us. This is consistent with
Vollenweider's (1968) use of a ]5N:1P loading ratio (by weight'
in his original loading diagrams (Figures 5 and 6). Since most
of the US OECD water bodies are phosphorus-limited, one must view
the positive correlation between nitrogen loading and mean chloro-
phyll a with caution. The relatively constant N:P loading ratio
may be~producing an artifact with respect to this relationship.
This possibility is illustrated in examination of the correlation
between nitrogen loadings and Secchi depth (Figure 39). Although
there are fewer data points than with phosphorus loads, there is a
considerable amount of data scatter in this relationship (i.e., a
nitrogen load of approximately 2 g N/m^/yr producing a Secchi
depth range of about 2 to 9 meters, to cite one example). This
would suggest that the nitrogen load has less effect on the algal
populations, and hence resultant Secchi depth, than does the
phosphorus load. This view is consistent with a phosphorus-limita-
tion of most US OECD water bodies.
A high positive correlation is found between nitrogen load-
ing and mean inorganic nitrogen (Figure 40). The correlation
232
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PHOSPHORUS LOADING (g P/m /yr)
Figure 37. Phosphorus Loading and Spring Overturn Total
Phosphorus Relationship in US OECO Water Bodies
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NITROGEN LOADING (gN/rn/yr)
Figure 38. Nitrogen Loading and Mean Chlorophyll a
Relationship in US OECD Water Bodies ~
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NITROGEN LOADING (gN/m/yr)
Figure 39
Nitrogen Loading and Mean Secchi Depth
Relationship in US OECD Water Bodies
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NITROGEN LOADING (gN/m2/yr)
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Figure 40. Nitrogen Loading and Mean Inorganic Nitrogen
Relationship In US OECO Hater Bodies
-------
Is better than that found between phosphorus load and either mean
total phosphorus or mean dissolved phosphorus (Figure 29 and 30).
This strong positive nitrogen loading-mean inorganic nitrogen cor-
relation lends support to the view that most US OECD water bodies
are phosphorus-limited, rather than nitrogen-limited. This high
correlation Indicates that the algal populations are not in general
depleting the input nitrogen, regardless of the magnitude of the
input. Rather, the inorganic nitrogen (i.e., algal-available
nitrogen) is increasing as the loading is Increasing. Thus, the
algae are not growing in response to the input nitrogen, but
rather in response to another nutrient. The lack of correlation
between phosphorus loading and mean dissolved phosphorus (Figure 30)
indicates the controlling nutrient is likely phosphorus.
There appears to be a positive correlation between nitrogen
loading and primary productivity (Figure 41). The correlation ap-
pears to be about the same degree as that between phosphorus load-
ing and primary productivity (Figure 31). However, there are
fewer data sets for nitrogen loading than for phosphorus loading.
Thus, this nitrogen load-primary productivity correlation may also
be a coincidental artifact of the relatively constant N:P loading
ratio found with the US OECD water bodies. There appears to be
no readily observable correlation between total annual primary
production and nitrogen loading (Figure 41). The data scatter is
of the same magnitude 3.5 that between phosphorus loading and total
annual primary production (Figure 32). This further illustrates
the limited applicability of correlations between nutrient loads
and both primary productivity and total production. It indicates
the relationship between these parameters may be more complex than
can be visualized using this single graphing technique.
It is difficult to determine if there is a correlation between
nitrogen loading and growing season epilimnetic chlorophyll a
(Figure 43). The correlation may be real, but the scarcity of
data for these two parameters does_not allow an accurate evalua-
tion. For the common water bodies, the data scatter between these
two parameters appears to be as great as that seen between phos-
phorus loading arid growing season epilimnetic chlorophyll a_
(Fi^uie 33). There Is a better' correlation between nitrogen
loading and growing season epilimnetic inorganic nitrogen (Figure
4'i ) than between phosphorus loading and either growing season
epilimnetic total phosphorus or dissolved phosphorus (Figures 29
^ini ^ 0 , respectively). Thus, the growing season and annual
mean -i Igal-ava i L-ible nitrogen both seem to correlate reasonably
well with their input. This growing season correlation (i.e.,
deDendence) of inorganic nitrogen upon the nitrogen loading pro-
vides fin?fher support to phosphorus-limitation of most of the US
OL D water bodies.
While a positive correlation is seen between nitrogen loading
and growing season epilimnetic primary productivity (Figure 45),
the data are too scarce to draw any clear conclusions as to the
validity oT this relationship. It is likely this correlation is
238
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NITROGEN LOADING(gN/m£/yr)
Figure 41. Nitrogen Loading and Primary Productivity
Relationship in US OECD Water Bodies
-------
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NITROGEN LOADING (gN/WVyr)
100
Figure 43. Nitrogen Loading and Growing Season Epilimnetic
'Chlorophyll a^ Relationship 1n US OECD Mater Bodies
-------
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NITROGEN LOADING(gN/m/yr)
Figure 44. Nitrogen Loading and Growing Season Epilimnetic
Inorganic Nitrogen Relationship in US OECD
Water Bodies
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a coincidental artifact of phosphorus-limitation. Finally, there
appears to be no correlation between nitrogen loads and the spring
overturn concentration of inorganic nitrogen (Figure 4-6). It
should be noted, however, that as with phosphorus (Figure 37), a
majority of the data sets include the mean winter concentration
rather than the spring overturn concentration. How this difference
may affect the results obtained with these correlations is not
known.
MEAN TOTAL AND DISSOLVED PHOSPHORUS CONCENTRATIONS
A positive correlation was observed between total phosphorus
and mean chlorophyll a in the US OECD water bodies (Figure 47)
even though the 'mean' values consisted of annual means, ice-free
period means and summer means. Dillon and Rigler (1975) and Jones
and Bachmann (1976) have also reported high correlations between
these two parameters. A negative correlation was also seen
between mean total phosphorus and mean Secchi depth (Figure 48).
This is to be expected since Secchi depth is a negative hyperbolic
function of the chlorophyll content of a water body (Edmondson,
1972; Carlson, 1974; Dillon and Rigler, 1975). Since chlorophyll
is correlated with mean total phosphorus, mean Secchi depth should
also be correlated with mean total phosphorus, as was observed.
A high positive correlation was noted for the mean total phos-
phorus and the mean dissolved phosphorus (Figure 49). This is not
surprising since the dissolved phosphorus content of the water body
should be related to the total phosphorus content. This correla-
tion indicates the dissolved phosphorus appears to be a relatively
constant fraction on an annual basis of the total phosphorus in
the US OECD water bodies. The mean total phosphorus also appears
to be positively correlated with- the mean primary productivity
(Figure 50). The correlation between these two parameters is
better than that seen between the phosphorus or nitrogen loading
and mean primary productivity (Figures 31 and 32, respectively).
In general, although positive correlations are noted, the
data are too scarce to make any valid conclusions about the rela-
tionship between mean total phosphorus and either the growing
season epilimnetic chlorophyll a or primary productivity (Figures
51 and 52, respectively). A positive correlation may exist
between mean total phosphorus and the spring overturn total
phosphorus (Figure 53), although the data are also relatively
scarce for this relationship. It should also be noted that a
majority of the water bodies in Figure 53 have mean winter total
phosphorus concentrations plotted rather than the spring overturn
concentrations. It is not known how this affect-s the results
of this correlation, although the effects would likely be small.
A positive correlation was also noted between the growing season
epilimnetic total phosphorus concentration and the growing season
epilimnetic chlorophyll a (Figure 54). While there are more data
sets for this correlation than for the relationship between an-
nual mean total phosphorus and growing season chlorophyll a_
(Figure 51), there is also more scatter of the data. The cor-
relation between the growing season epilimnetic total phosphorus
244
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Mean Chlorophyll in Upper Two Meters
% of Water Column
• Summer Mean Concentrations
+ Ice-Free Period Mean Concentrations
O.I I i i i i i i 111 i i i l l i i 11 i i i i i 111
o.ooi o.oi o.i i
ANNUAL MEAN TOTAL PHOSPHORUS (mg P/l)
Figure W. Mean Total Phosphorus and Mean Chlorophyll a_
Relationship in US OECD Water Bodies
-------
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ANNUAL MEAN TOTAL PHOSPHORUS (mg P/|)
Figure 48. Mean Total Phosphorus and Mean Secchi Depth
Relationship in US OECD Water Bodies
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ANNUAL MEAN TOTAL PHOSPHOROUS (mg P/l)
Figure 49. Mearr Total Phosphorus and Mean Dissolved Phosphorus
Relationship in US OECO Water Bodies
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ANNUAL MEAN TOTAL PHOSPHORUS(mg P/1)
Figure 50. Mean Total" Phosphorus and Primary Productivity
Relationship In US OECD Water Bodies
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ANNUAL MEAN TOTAL PHOSPHORUS (mgP/l)
Figure 52. Mean Total Phosphorus and Growing Season Epilimnetlc
Primary Productivity Relationship in US OECD Water
Bodies
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GROWING SEASON MEAN EPILIMNETIC TOTAL PHOSPHORUS (mg P/l)
Figure 54. Growing Season Eplllmnetic Total Phosphorus and
Growing Season Eplllmnetic Chlorophyll a Relationship
1n US OECD Water Bodies
-------
and growing season primary productivity (Figure 55) is very similar
to that seen with the annual mean total phosphorus (Figure 52).
This suggests that the total phosphorus concentration does change
significantly over the annual cycle. However, the scarcity of data
does not allow for a rigorous examination of these two relationships
A positive correlation was also noted between the spring overturn
total phosphorus concentration and the growing season epilimnetic
concentrations of chlorophyll a, total phosphorus and dissolved
phosphorus (Figures 56, 57 and 58, respectively). However, none of
these three relationships had sufficient data for a valid assess-
ment of their degree of correlation. It would particularly have
been informative to examine the correlation between the spring
overturn total phosphorus concentration and the growing season
chlorophyll concentration (Figure 56) since Sakamoto (1966), Dillon
and Rigler (1974a) and Vollenweider (1976a) have shown good corre-
lations between these two parameters.
The correlation between spring overturn phosphorus and growing
season epilimnetic dissolved phosphorus was also examined (Figure
58). Although there is somewhat of a positive correlation noted,
this is not a limnologically logical correlation to consider, since
the measured growing season epilimnetic dissolved phosphorus will
be the portion of the available phosphorus 'left over' in a water
body after the aquatic plant populations have assimilated their
metabolic requirements. Consequently, the use of the 'available1
nutrients in any of the correlations is of dubious value. They are
included in this analysis solely because they were included on the
initial list of suggested parameters supplied to all the OECD inves-
tigators .
The mean dissolved phosphorus was also included in this
eutrophication response parameter analysis but is not expected
to yield any useful correlations for the reasons indicated above.
There is a possible correlation between the mean dissolved phos-
phorus and mean chlorophyll a (Figure 59). However, the mean
chlorophyll a is composed of annual mean, ice-free period mean and
surface mean~values. Consequently, little validity was given to
this relationship. By contrast, the correlation between the mean
total phosphorus and mean chlorophyll a (Figure 47) is much better
than that seen for mean dissolved phosphorus. The correlation
between mean dissolved phosphorus and primary productivity
(Figure 60) partially supports this view. There is considerable
scatter in the data for these two parameters which indicates
little correlation between them. The primary productivity data is
too scarce for correlation, but it is not expected that a larger
US OECD data set would show a positive correlation.
There appears to be a positive correlation between mean
dissolved phosphorus and spring overturn dissolved phosphorus
(Figure 61). This is not unexpected if the dissolved phosphorus
is the 'leftover1 fraction. Presumably the larger the leftover
dissolved phosphorus content of the water body, the larger will
be the concentration at spring overturn. However, this correla-
tion shows more data scatter than that between mean total phos-
254
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i i i
i i i
0.001
0.01 O.I I
OVERTURN TOTAL PHOSPHORUS (mg P/l)
Figure 56. Spring Overturn Total Phosphorus and Growing
Season Epilimnetic Chlorophyll a Relationship
In US OECO Water Bodies
-------
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f 1 1 1 1 1
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SPRING OVERTURN TOTAL PHOSPHORUS (mg P/l)
10
Figure 57. Spring Overturn Total Phosphorus and Growing
Season Epillmnetic Total Phosphorus Relation-
ship in US OECD Water Bodies
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SPRING OVERTURN TOTAL PHOSPHORUS (mg P/|)
Figure 58. Spring Overturn Total Phosphorus and Growing
Season Mean Epilimnetic Dissolved Phosphorus
Relationship in US OECD Water Bodies
10
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ANNUAL MEAN DISSOLVED PHOSPHORUS (mg P/l)
Figure 59. Mean Dissolved Phosphorus and Mean Chlorophyll a_
Relationship in US OECD Water Bodies ~~
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ANNUAL MEAN DISSOLVED PHOSPHORUS(m$P/l)
Figure 60. Mean Dissolved Phosphorus and Primary Productivity
Relationship in US OECD Water Bodies
-------
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phorus and spring overturn total phosphorus, as would be expected.
There also appears to be no readily observable correlation between
either the growing season epilimnetic dissolved phosphorus or the
spring overturn dissolved phosphorus and the growing season
epilimnetic chlorophyll a (Figures 62 and 63, respectively). How-
ever, the data set for these two correlations is very small, which
precludes a rigorous analysis of these relationships. It is
possible a positive correlation may exist between the spring over-
turn dissolved phosphorus concentration and the growing season
epilimnetic chlorophyll a in phosphorus-limited water bodies. A
positive correlation is noted between the spring overturn dissolved
phosphorus and the growing season epilimnetic dissolved phosphorus
(Figure 64-). However, in addition to a data set which is too
small for a valid evaluation of this relationship, a positive
correlation between these two parameters is not limnologically
consistent with the conditions normally found in phosphorus-limited
water bodies. The available US OECD data sets for these two
parameters are almost completely for phosphorus-limited waters.
Consequently, the apparent correlation is probably an artifact.
There were not sufficient data to examine the correlation between
spring overturn dissolved phosphorus and growing season epilimnetic
primary productivity. Presumably, if it existed, the correlation
'would be a positive one.
MEAN INORGANIC NITROGEN CONCENTRATIONS
Before examination of correlations between the mean inorganic
(i.e., algal-available) nitrogen and eutrophication response
parameters, it should be noted that the concentrations of this
algal nutrient, as with dissolved phosphorus, will rise and fall
as a function of the algal activity in a water body. Thus, as
before, this nitrogen fraction will represent the 'leftover'
nitrogen after the algal populations have assimilated their
stochiometric requirements for growth. Hence, an observed correla-
tion may be an artifact of this process. It is further complicated
because the majority of the US OECD water bodies are phosphorus-
limited. Therefore, the leftover inorganic nitrogen concentra-
tions will likely always be higher than the available dissolved
phosphorus concentration. The same inorganic nitrogen forms were
not reported for all US OECD water bodies. Some investigators
reported the mean concentration of NHiJ+NOj+NOJ (as N) and others
reported NH^+NOg (as N), while still others reported NO^+NOJ (as N),
These various combinations were treated as equal components in
the correlations, although it is not correct to do so. These
factors should be considered when examining any correlations
between inorganic nitrogen and other eutrophication response para-
meters in the US OECD water bodies.
There appears to be little correlation between mean inorganic
nitrogen and mean chlorophyll a_ (Figure 65). Removal of the one
outlying point at low annual mean inorganic nitrogen and chloro-
phyll a results in a situation in which there is essentially no
relationship between the two parameters. By contrast, there is a
262
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GROWING SEASON MEAN EPILIMNETIC DISSOLVED
PHOSPHORUS (mg/l)
Figure 62. Growing Season Epilimnetic Dissolved Phosphorus
and Growing Season Epilimnetic Chlorophyll a
Relationship in US OECD Water Bodies
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SPRING OVERTURN DISSOLVED PHOSPHORUS (mg P/1)
Figure 63. Spring Overturn Dissolved Phosphorus and Growing
Season Mean Epilimnetic Chlorophyll a Relationship
i-n US OECD Water Bodies
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ANNUAL MEAN INORGANIC NITROGEN (mgN/l)
Figure 65. Mean Inorganic Nitrogen and Mean Chlorophyll a
Relationship in US OECD Mater Bodies
-------
good correlation between mean total phosphorus and mean chloro-
phyll a (Figure 47). This observation further substantiates the
importance of phosphorus, rather than nitrogen, in controlling
algal growth. There is little or no correlation between mean inor-
ganic nitrogen and mean Secchi depth (Figure 66). There is a
positive correlation between mean inorganic nitrogen and primary
productivity (Figure 67). This further supports the phosphorus-
limitation of most US OECD water bodies. If the water bodies were
nitrogen-limited, one would expect a negative correlation between
these two parameters. In fact, the opposite correlation is
indicated in Figure 67. By contrast, the poor correlation between
the dissolved phosphorus and the primary productivity (Figure 60)
illustrates its controlling role in the eutrophication process in
the majority of the US OECD water bodies.
There is a correlation between mean inorganic nitrogen and
the growing season epilimnetic chlorophyll a (Figure 68). A nega-
tive correlation would be expected if nitrogen were the controll-
ing algal nutrient. Such a correlation was not seen in Figure 68.
A strong positive correlation appears to exist between the mean
inorganic nitrogen and the growing season epilimnetic primary
productivity (Figure 69). However, there are only about a half
dozen data sets for this correlation. This scarcity of data pre-
cludes any rigorous evaluation of this correlation. The positive,
rather than negative, correlation suggests that nitrogen does not
control the algal populations. The lack of data does not allow
one to evaluate the correlation between mean inorganic nitrogen
and spring overturn inorganic nitrogen.
Interestingly, a negative correlation appears to exist be-
tween the growing season epilimnetic inorganic nitrogen and the
growing season epilimnetic chlorophyll a_ (Figure 70). Although
the data set is somewhat limited, the correlation appears to be
real. This indicates that, while phosphorus may control the algal
populations in most of the US OECD water bodies (Figure 62), the
need for available nitrogen for algal growth results in a de-
creased nitrogen concentration during the growing season. A
positive correlation also appears to exist between the growing
season epilimnetic inorganic nitrogen and the growing season
epilimnetic primary productivity (Figure 71). While the data
sets are relatively scarce for this correlation, it is consistent
with the views expressed above for Figure 70.
OTHER CORRELATIONS BETWEEN EUTROPHICATION RESPONSE PARAMETERS
Several other correlations were also examined in this section,
as indicated in Table 26. These latter correlations are grouped
together because they are of a varied nature. They are discussed
below. There is a positive correlation observed between the mean
chlorophyll a and primary productivity (Figure 72) in the US OECD
water bodiesT Some scatter of the data is observed. One would
normally expect a good correlation between these two parameters.
This is supported somewhat by the correlation between the primary
267
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Figure 67. Mean Inorganic Nitrogen and Growing Season Mean
Epilimnetic Primary Productivity Relationship in
US OECD Water Bodies
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Figure 68. Mean Inorganic Nitrogen ar\d Growing Season Epilimnetic
Chlorophyll a^ Relationship in US OECD Water Bodies
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Figure 69. Mean Inorganic Nitrogen and Primary Productivity
Relationship in US OECD Water Bodies
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GROWING SEASON MEAN EPILIMNETIC
INORGANIC NITROGEN (mgN/l)
Figure 70. Growing Season Epilimnetic Inorganic Nitrogen
and Growing Season Epilimnetic Chlorophyll ^
Relationship in US OECD Water Bodies
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Figure 71. Growing Season Eplllmnetlc Inorganic Nitrogen
and Growing Season Epilimnetlc Primary Productivity
Relationship in US OECD Water Bodies
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Figure 72. Primary Productivity and Mean Chlorophyll a
Relationship .in US OECD Water Bodies
-------
productivity and the mean Secchi depth (Figure 73). As expected,
there is a negative correlation between these two parameters, al-
though the data are sparse. However, the correlation exhibits a
considerable data scatter, which limits its value. It is noted
that a majority of the water bodies have primary productivities
ranging from about 40-1000 g C/m /yr, yet have Secchi depths
between 1-3 meters.
A possible hyperbolic relationship was exhibited in the
correlation between mean chlorophyll a and mean Secchi depth.
The significance of this relationship as a "trigger" for public
response to eutrophic water bodies , and as a simple, practical
method for measuring water quality was discussed by Edmondson
(1972) and Carlson (1974). This correlation is discussed in detail
in a later section of this report (see Figures 77 and 78) and serves
as the basis of a nutrient load-water quality model developed in
this study. There is a positive correlation between the growing
season epilimnetic chlorophyll a and primary productivity (Figure
74). This is consistent with the observations indicated above
between the annual mean values of these two parameters. There is
a somewhat better correlation between the growing season epilim-
netic values, as would be expected. However, the very few data
sets limit the usefulness of this correlation as a predictive
tool.
The annual mean primary productivity, on a daily basis, was
correlated with the annual mean chlorophyll a on both a volumetric
and areal basis (Figures 75 and 76, respectively). This correla-
tion was analyzed solely because it appeared on the list of
suggested correlations. There is a positive correlation between
the daily average primary productivity and the annual mean chloro-
phyll a concentration (Figure 75). This correlation is similar
to that observed between the annual mean primary productivity and
annual mean chlorophyll a (Figure 72), except that the annual
primary productivity is expressed on a daily basis instead of an
annual basis. Consequently, Figure 75 yields no more additional
information than is already noted in Figure 72. There is little
or no correlation between the annual mean daily primary produc-
tivity and the annual mean areal chlorophyll a (Figure 76). This
data set exhibits a considerable scatter. There appears to be no
readily observable advantage in expressing mean chlorophyll a
concentrations on an areal basis instead of a volumetric basTs.
In conclusion, there appear to be better correlations between
the phosphorus loads and concentrations of the US OECD water bodies
and the various eutrophication response parameters indicated above
than for the nitrogen loads and concentrations. Consistent with
phosphorus-limitation of the US OECD water bodies, there are
generally poor correlations between the dissolved (i.e., algal-
available) phosphorus concentrations and the response parameters
examined in the US OECD water bodies. While correlations also
existed between the nitrogen loads and concentrations and response
parameters of the US OECD water bodies , it is felt that many of
these correlations are coincidental artifacts caused by a relatively
275
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Figure 73. Primary Productivity and Mean Secchi Depth
Relationship in US OECD Water Bodies
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Figure 74. Growing Season EpIHmnetlc Primary Productivity
and Growing Season Ep1l1mnet1c Chlorophyll a
Relationship 1n US OECO Hater Bodies
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Figure 75. Mean Daily Primary Productivity and Mean Chlorophyll a
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Chlorophyll a_ Relationship in US OECD Water Bodies
-------
constant N:P loading ratio and the basic phosphorus limitation of
the water bodies. Several of these correlations, notably total
phosphorus versus chlorophyll a and chlorophyll a versus Secchi
depth, have been used in the development of several phosphorus
load-water quality models presented in the following section of
this report.
280
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SECTION XI
APPLICATION OF US OECD RESULTS FOR PREDICTING CHANGES IN
WATER QUALITY AS A RESULT OF ALTERING NUTRIENT INPUTS
It is of interest to attempt to predict the change in water
quality that might be expected to occur as a result of altering
the nutrient loading to a water body. Attention will be focused
here on phosphorus loadings for reasons mentioned earlier; namely
because many US water bodies are phosphorus-limited, and because
phosphorus removal from point sources is both technically and
economically feasible (Vollenweider, 1968, 1975a; Lee, 1971, 1973;
Vallentyne, 1974; Vollenweider and Dillon, 1974).
The specific question to be addressed is what is the change
in water quality expected from a change in the phosphorus load-
ings to a water body? There are several ways to attempt to answer
this question. The best overall approach that can be taken to
assess the effects of a change in phosphorus loadings on the
trophic conditions of a water body is based on the work of Vollen-
weider (1975a), discussed in an earlier section of this report.
Vollenweider's approach for assessing the degree of fertility of
a water body, based on its phosphorus loadings and its mean depth
and hydraulic residence time characteristics, was presented graphi-
cally in Figure 19. The results of the US OECD eutrophication
study, as well as those of the Canadian portion of the North Ameri-
can Project, and the Alpine, Nordic and Shallow Lakes and Reservoirs
Project have provided considerable support for this approach. An
earlier version of this approach has also been used by tne US EPA
(1975a) in evaluating the phosphorus loading-eutrophication response
in the water bodies in the National Eutrophication Survey, as re-
flected in their degree of fertility. Further5 this earlier version
was recommended by the US EPA in their Quality Criteria for Water
(US EPA, 1976a) as a basis for determining critical phosphorus load-
ings for US lakes and impoundments.
As indicated earlier by examination of Figure 19, there is
remarkably good agreement between the overall trophic states of
the lakes and impoundments in the US OECD eutrophication study as
determined by their respective investigators and as indicated by
their phosphorus loadings and mean depth/hydraulic residence time
characteristics. The US EPA, in the National Eutrophication Sur-
vey (US EPA, 1975a), has found a similar agreement for the water
281
-------
bodies that they have investigated thus far. In general, using
this relationship, it can be said that in terms of water quality
for a given set of morphologic and hydrologic characteristics,
as the phosphorus load is increased there is a gradation of
deteriorated water quality, as measured by the frequency and
severity of obnoxious algal blooms.
The reader should be reminded that the permissible and ex-
cessive lines on the Vollenweider phosphorus loading diagram
(Figure 19) should not be interpreted as rigid values which de-
fine a certain level of water quality. That is, a water body
whose phosphorus loading and mean depth/hydraulic residence time
characteristics place it just above the excessive line should not
be rigidly viewed as having poor water quality. Nor should a
water body plotting just below the permissible line be defined
strictly as possessing good water quality. Rather, the influence
of eutrophication on water quality in a water body is dependent
on the public's response, as manifested in an impairment of use
of the water body.
As discussed earlier, those water bodies with a given mean
depth/hydraulic residence time relationship which plot the great-
est vertical distance below the permissible boundary line can be
expected to have the best water quality. Conversely, those which
plot the greatest vertical distance above the excessive loading
line would have the poorest water quality. There is a continual
gradient of water quality between these two extremes, with the
permissible boundary area defining a general water quality con-
dition acceptable to most of the population.
The position of these lines, as indicated in Equation 11, is
influenced by the work of Sawyer (1947). While studying the ef-
fects of urban and agricultural runoff on the fertility of 17
lakes in southern Wisconsin, he found a 0.01 mg/1 phosphorus con-
centration in a water body at spring overturn to be a critical
concentration for high water quality. Water bodies whose spring
overturn phosphorus concentrations exceeded this 0.01 mg P/l
critical concentration were likely to experience algal bloom
problems during the following summer growing season. The Vollen-
weider model (Figure 19) is an extension of Sawyer's findings
which takes into account some of the morphological and hydrological
characteristics of a water body which influence its phosphorus
loading-algal growth relationships.
The excessive and permissible phosphorus loading boundary
lines on the Vollenweider diagram are based mainly upon the recrea-
tional impact of eutrophication. They do not address some of the
other parameters of water quality that are influenced by eutroph-
ication. To cite one such example, one could not utilize these
phosphorus boundary loading lines to judge whether anoxic condi-
tions would develop in the hypolimnion of a water body. A lake
could receive an excessive loading and still have an oxic
282
-------
hyDolimnion throughout the year. Dillon (1975; Vollenweider
and Dillon, 1974; Dillon and Rigler, 1974b) has reported such
an occurrence in a number of water bodies in southern Ontario.
This occurred because hypolimnetic oxygen depletion, which is
an important eutrophication parameter, is dependent not only on
the nutrient load, but also on the hypolimnetic morphology
and the hydraulic flushing rate of the water body. Furthermore,
the excessive and permissible phosphorus loading lines in Figure
19 do not address the potential eutrophication problems arising
from excessive fertilization of water bodies used for domestic
water supplies (i.e., taste and odor problems, shortened filter
runs, etc.) as contrasted with recreational uses (Gaufin, 1964;
DeCosta and Laverty, 1964; Poston and Garnet, 1964; AWWA, 1966).
While the positions of the US OECD water bodies in the
Vollenweider diagram (Figure 19) appear to be a good indication
of the overall eutrophication and associated water quality for
these water bodies, it is desirable to be able to translate this
relationship to a eutrophication parameter which is more easily
and widely appreciated by both the scientist and layman. For
example, in Figure 19, the phosphorus loading to Lake Washington
decreased from 2.3 g/m /yr in 1964 (water body number 50 in
Figure 19), to 0.4 g/m^/yr in 1971 (number 51 in Figure 19),
moving it from the eutrophic zone to a position indicating a
much less productive water body. However, a decrease in phos-
phorus loading or in-lake phosphorus concentration in a water
body does not necessarily mean that an improvement in water
quality has also occurred. A concomitant change in a parameter
which is commonly used to indicate trophic conditions in a water
body would help one to appreciate the change in general water
quality resulting from a reduced phosphorus input. This section
of this report presents the development and application of an ap-
proach for assessing changes in water quality to be expected
from a change in the phosphorus load to a water body.
The first step in transforming phosphorus loading changes
to readily-appreciated indicators of changes in trophic conditions
is to examine the relationship between the spring overturn crit-
ical phosphorus concentration, and the average chlorophyll con-
centration during the following summer growing season. Several
investigators (Sakamoto, 1966; Dillon and Rigler, 1974a, 1975;
Vollenweider, 1976a) have shown a strong relationship exists
between these two parameters. Chlorophyll a concentration in
a water body is a much more readily observable consequence of
phosphorus loading than is a water body's phosphorus concentra-
tion. The effects of phosphorus loading can be visibly appre-
ciated as a function of the resulting chlorophyll a concentra-
tion or "greenness" of a water body. Vollenweider~(1976a) has
plotted chlorophyll a concentrations as a function of the phos-
phorus loading characteristics of a water body. The theoretical
basis of this approach was presented in an earlier section of
this report. The reader is reminded that the phosphorus loading
283
-------
characteristic expression, ( (L(P) /qs) / (1+
-------
Washington, both before and after the completion of its ex-
tensive sewage diversion program. The resultant chlorophyll a
changes tracked quite closely the expected changes (See Figure
9 in Vollenweider, 1976a). It is noted, however, that a few
years after the sewage diversion project was completed, the
chlorophyll a concentrations tended to be higher than that
based on Vollenweider's relationship between phosphorus load-
ing and chlorophyll. As discussed in an earlier section, this
is most probably related to the fact that a water body takes
several years to adjust to a new phosphorus loading. This
time period of adjustment is equal to approximately three
phosphorus residence times (Sonzogni et_ al_. , 1976). The
final result in Vollenweider's (I976a; application of the Lake
Washington data to his phosphorus loading and chlorophyll a rela-
tionship is in accordance with what is expected based on the
phosphorus load under equilibrium conditions.
Thus, in summary, examination of the US OECD data as pre-
sented in Figure 22 indicates there is good agreement between
overall chlorophyll levels and phosphorus loads (as expressed^
in the phosphorus loading characteristics term (L(P)/qs)/(l+i
for water bodies studied in the US OECD eutrophication study.
This relationship will be used in the following pages to fur-
ther develop a meaningful relationship for assessing changes
in water quality to be expected following a change in the phos-
phorus load to a water body.
The next step in this effort is to examine the relation-
ship between chlorophyll and Secchi depth and then to unite
this relationship with the phosphorus load to a water body. As
indicated in an earlier section, the use of the Secchi depth of
a water body as an indicator of its algal biomass and overall
water quality has been proposed by several investigators
(Edmondson, 1972; Carlson, 1974; Shapiro, 1975b; Shapiro et al. ,
1975). Indeed, the Secchi depth is thought to be one of the
best overall parameters that the public could respond to for
improved water quality. Edmondson (1972) and Shapiro et al.
(1975b) have presented similar conclusions on the value~of~the
Secchi depth as a measure of the impairment of water quality
by excessive fertilization. A number of investigators have
demonstrated an inverse non-linear relationship between the
chlorophyll a content of a water body and its Secchi depth
(Edmondson, 1972; Carlson, 1974; Bachmann and Jones, 1974;
Dillon and Rigler, 1974a; 1974b; Dobson, 1975; Norvell and
Frink, 1975 and Michalski et al., 1975). Further, the US OECD
data showed a similar relationship. The pertinent data are
presented in Table 27. A plot of the chlorophyll a concentrations
and Secchi depths from these various sources is presented in
Figure 77. The data reported by Edmondson (1972), although
extensive and extending over a number of years , was not in-
cluded in this plot since this relationship was for only one
water body while the other data sets were from a variety of
water bodies. It was felt by these reviewers that his data
285
-------
Table 27. DATA FOR CHLOROPHYLL a AND SECCHT DEPTH RELATIONSHIP"
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Carlson
(1974)3
Chlor a
0
2
6
20
56
1
2
3
4
5
6
7
8
9
10
12
14
16
18
20
0
22
25
27
30
35
40
.94
.6
.4
.5
.5
.0
.5
.0
.0
.0
b SD
8
4
2
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0
7
4
0
3
2
2
2
1
1
1
1
1
1
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1
12
0
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.0
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.90
.85
.80
.75
.70
.65
Dobson
(1975)a
Chlor a
5
5 ,
4 .
4 .
4 ,
4 .
4
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3
3.
1 .
1
1 .
0
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.9
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C SD
2 ,
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2 .
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3
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4
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8
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Dillon £
Rigler
O97'la)a
Chlor a° SD
.55
.18
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.7
.75
.0
.6
.0
.2
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.7
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. 7
Bachmann 6
Jones
(1974)
Chlor a
4
5
1
3
5
4
3
4
8
4
5
6
6
9
12
9
10
10
12
10
22
30
14
23
14
24
.5
.5
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.0
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.0
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.0
.0
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.0
.0
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.5
.0
.0
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.0
SD
5
5
4
3
3
3
3
2
2
Z_
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
.5
.1
.75
. 7
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.0
.9
.9
.85
.5
.5
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.3
.1
.05
.9
.8
.7
.65
.6
.45
.2
.1
.0
.0
Norvell £
Frink
(1975)
Chlor a SD
0
0
50
30
14
7
13
34
2
7
a
0
1
4
9
4
7
38
5
2
2
4
5
14
13
1
3
.6
.9
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.5
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.0
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.3
US OKCD Eu-
trophication
Study3
Chlor a
14.
5 .
6 .
6 .
5 .
6
5
7 .
5 .
20e
26.
G
4
33.
3.
53d
13.
21.
6
3
5
2
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5
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10
6d
gO
°d
3d
0
4
6
c\
5
A
9d
5
2
2
SD
3
1
2
2
1
2
2
1
2
1
1
2
2
0
2
1
1
1
1
2
3
3
3
2
1
1
1
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.0
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. 3
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. 8
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.5
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.4
.0
.4
.2
.8
.2
.1
.0
.3
.5
.8
.8
Michalsk
et al .
(1975)
Chlor
1
2
1
2
7
8
6
13
6
4
9
14
5
14
20
24
18
.1
.2
.0
.3
.2
.0
.8
.5
.6
.1
. 3
.1
.8
.4
.0
.9
.0
a
8
6
4
4
J
3
3
2
2
2
2
1
1
1
1
0
0
i
a
SD
.05
.25
.35
. 0
. 35
.15
.0
.65
.5
.1
.1
.95
. 80
.1
.1
.85
.45
-------
Table 27 (continued). DATA FOR CHLOROPHYLL a AMD SECCHI DEPTH RELATIONSHIP0
ro
oo
Dillon £
Carlson Dobson Riglor
(1974)3 (1975)3 (197i|a)a
Bachmann £ Norvell &
Jones Frink
(1974) (1975)
Clilor ab SD Chlor a° SD Chlor a° SD Chlor a
45.0 0 . G 0 2
50.0 0 . 5 5 0
60.0 0.50 1
70.0 0.45 1
|
1
2
2
6
1
]
2
1
3
1
7
1
0
1
1
2
3
2
]
2
1
1.
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. 5
. 5
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. 8
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.8
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. 7
. 8
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. 5
5
5
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5
5
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4
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4
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3
3
3
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3
. 7
r
. 5
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.?b
.25
.25
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. 7
. 7
. 7
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s s
.45
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. 35
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. ?5
.1
.95
. 85
. 7 5
. 7
. b
.55
.45
SD Chlor a SD
1 5
3
2
3
31
9
5
5
r
2
13
9
1
1
0
2
103
25
.5
.2
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.]
.0
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2
6
7
6
2
3
4
3
3
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7
7
8
1
2
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.2
. 3
.2
.0
.5
US OECD Eu- Michalski
trophication et al.
Study3 Tl975)a
Chlor a
90
65
15
12 .8
-------
Table 27 (continued). DATA FOR CHLOROPHYLL a AND SECCHI DEPTH RELATIONSHIP11
CD
CO
Dillon &
Carlson Dobson Rigler
(197i4)a (1975)3 (1974a)a
Chlor ab SD Chlor ac SD Chlor ac SD
2
?
3
5
7
I
4
9
6
5
13
17
3
19
14
14
7
13
16
.9
.2
. 2
.4
.9
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.0
.1
.4
.2
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.9
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.1
.3
3
3
3
2
2
2
2
2
2
2
1
1
1
1
1
1
1
0
0
Bachmann 6 Norvell E US OECD Eu- Michalski
Jones Frink trophication et al.
(1974)a (1975)a Study3 ~U975)a
Chlor a SD Chlor a SD Chlor a SD Chlor a SD
.45
.4
. 35
.65
.35
.25
.2
.15
.15
.0
.9
. 7
.4
.2
.2
.05
.0
. 75
.45
Explanation:
b
Source of data; all chlorophyll values are in pg/1; all Secchi depth values are in meters
Surface chlorophyll
d
Summer total chlorophyll
Upper 2 meter's of water column
Summer surface moan values
-------
9.0
8.5 F
8.0
7.5
7.0
6.5
X
K
0-
X
o
o
LJ
CO
6.0
5.5
5.0 |a
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
Cf
•"on
OD
on
- 6 D
i<>£» n
0 tl
5 x°
x00 D
*3& m
0*S%°0 D.
•-I I sD
D D
• •
C& 0 " n
*-• S.A° o.
*^ ^ % 0 •* '
A.* •« » R>
§3 A O • . •
DATA FROM:
A CARLSON (1974)
V DOBSON1I976)
O DILLON AND RI6LER (19740,1975)
0 BACHMANN AND JONES (1974)
D NORVELL AND FRINK (1975)
X MICHALSKI «! OUI975)
• US OECD STUDY
_L
J_
_i_
10 15
25 30 35 40 45 50 55 60 65 70 75 80 • 85 90
MEAN CHLOROPHYLL a (ug/D
Figure 77. Secchi Depth and Chlorophyll a_ Relationship in
Natural Waters (Linear Scale).
289
-------
base would bias the resultant plot toward the chlorophyll a_ and
Secchi depth relationship typical of Lake Washington. In addition,
an examination of the Secchi depth and chlorophyll relationship in
Lake Washington showed it to be somewhat different than that seen
with the other sources listed above. Consequently, only data re-
ported from a wide range of water body types were used in Figure 77.
However, a comparison of this figure with the plot presented by
Edmondson (1972) shows a similar hyperbolic relationship
between these two parameters, with the slope of the curve steepest
at the lower chlorophyll concentrations.
As it is difficult to get an accurate regression line of best
fit for the non-linear chlorophyll a and Secchi depth relationship
illustration in Figure 77, the same~data sets were plotted on a
double logarithm plot. This is illustrated in Figure 78. The
regression equation for this plot is:
Iog10 Secchi depth = -0.473 log1Q [chlorophyll a] + 0.803
(39)
The regression line has a correlation coefficient, r = -0.85, in-
dicating a good correlation between the chlorophyll a_ content and
Secchi depth in natural waters for a wide variety of water bodies
located throughout the US.
Since the chlorophyll content of a water body is related to
its phosphorus loading characteristics (Figure 22), and since
a strong correlation was demonstrated above between chlorophyll a
and Secchi depth (Figure 78), there should also be a relationship
between a water body's phosphorus loading characteristics and its
Secchi depth. In fact, the final step remaining in this exercise
is to unite both these relationships (Figures 22 and 78) into a
single expression which directly relates these two parameters.
This has been accomplished by producing a double logarithmic plot
of the phosphorus loading expression, (L(P)/qs)/ (l+,/!2T/qs) , and
Secchi depth, as illustrated in Figure 79. The line of best fit
was extrapolated from the data presented in Figures 22 and 78.
Chlorophyll a. values, as a function of a water body's phosphorus
loading characteristics, were taken from Figure 22. Then, the
expected Secchi depth for a given chlorophyll a_ concentration was
taken from Figure 78. The expected Secchi depth was then plotted
as a function of the original phosphorus loading expression above,
to produce the line of best fit illustrated in Figure 79. Using
least square analysis, the regression equation for this line is:
Iog10 Secchi depth = -0.359 Iogl0 [ (L(P)/qs ) / (1+,/fTq^) ] + 0.925
(40)
Using this relationship (Figure 79), one can determine the Secchi
depth to be expected as a function of the phosphorus loading
290
-------
20
r-o
CO
10
O)
£
X
I-
Q.
LJ
Q
X
O
o
Ul
CO
o
o
X
n
Source of Polo:
Corlson(l974)
Dobson (I97S)
Dillon 8 Rigler (I974o ; 1975)
Bochmonn 8 Jones (1974)
Michalski et oM(975)
Norvell 8 Frink (1975)
US OECD Study
log Secchi depth = -0.473 log [Chlorophyll o] 40.803
0.4
I
I
1 1 1 1 1
0.4
I 10
CHLOROPHYLL g CONCENTRATION (/Ltg/l)
Figure 78.
100
Secchi Depth and Chlorophyll a^ Relationship in
Natural Waters (Log-Log Scale).
-------
z&z
MEAN SECCHI DEPTH (meters)
o
In - C
- \ /[(L(P)/qs)/(l+.y?/qs)]=4.0(36); 1.8(48)
| Secchi depth = 28.3(36), 28(48)
L tog Secchi deplh = -0.359 log[(L(P)/qs)/(l+/fAts)|+0.925
— -«^. ... ¥ ,, | INVESTIGATOR-INDICATED
-~-v^^* ^ • TROPHIC STATE;
. O ^^"^^ ~ 44 ^2 •-EUTROPHIC
lOT "-^^. 45 « ,3 •
°)9 ->>. • 40 34 4J « A-MESOTROPHIC
° 26 49^>>^ *4 ^ O-OLIGOTROPHIC
• ^•^"•^^^•••^8
• l6 54 ^-vAe «35
50 • 'V^-^ 47
(US OECD woler bodies ore • *^ — „
plotted obove) ^
28
i i I t I I I I I I I I I 1 i I I I I I I 1
> 10 100 1000
(mg/m3)
Figure 79. Phosphorus Loading Characteristics and Secchi
Depth Relationship in Natural Waters
-------
characteristics of a given water body. As indicated earlier,
this relationship allows one to be able to determine the change
in water quality in a water body, expressed as a function of
its Secchi depth, which would result from a change in its
phosphorus load. The change may be deterioration or enhancement
of water quality (i.e., decrease or increase in Secchi depth)
depending on whether the phosphorus flux to a water body was
increased or decreased. This relationship, therefore, represents
a single, practical application of some of the results of the
US OECD Project in assessing the effects of phosphorus loadings
to water bodies as expressed as a function of a widely-appreciated
parameter of eutrophication, both to scientists and laymen.
There are several precautions that should be noted in the
use of this relationship. One consideration is that it would
hold only for those water bodies where the primary factor con-
trolling water clarity is phytoplankton. It would not be ap-
plicable in its present form to water bodies with large amounts
of inorganic turbidity or color. However, it may be possible to
partially correct for the effects of excessive inorganic turbidity
and color on the Secchi depth of a water body. According to
Vollenweider (1977), in the simple case, the Secchi depth may be
computed as the integral of the turbidity above the Secchi disk
(i.e., / T(g)da = constant, where S = Secchi depth (m), T(B) =
mineral turbidity at depth g (mg/1), and T(g) is inhomogenous
over depth g). For the homogenous case, the Secchi depth may
be calculated as S = l/(k]_ + k2 (C) + k3 (T) + k4 (Chi)), where
C = color (mg P,/l), T = mineral turbidity (mg/l), Chi = chlorophyll
a (mg/m3) and k,, k2, k and k. = constants. Vollenweider (1977)
is evaluating trie constants as follows: k-, * 0.025, k~ ~ 0.005 to
0.01 and k^ * 0.01 to 0.02. The constant k"3 is difficult to
estimate because of the lack of appropriate data for expression
of the interaction of primarily biological turbidity with chlor-
ophyll a. In relatively transparent water (i.e., little color
or mineral turbidity), one may approximate k~ by use of the
relationship, S = l/(k«(Chl) . For very transparent waters, C,
T and Chi can be expected to be very small. Accordingly, recalling
k^ ~ 0.025, the Secchi depth approximates 40 meters (i.e., S =
1/0.025). For less transparent waters, one will have a family
of curves, depending mainly on the terms k? (C) and k~(T). Thus,
one could attempt to correct the Secchi depth for high color or
inorganic turbidity in water bodies using the relationships
expressed above. The corrected Secchi depth can likely then be
applied in the previously-mentioned equations relating the phos-
phorus loading, chlorophyll a and Secchi depths in natural waters.
It should be noted, however, that it was not possible to test the
homogenous equation above because of lack of sufficient data for
the US OECD water bodies. Few water bodies in the US OECD eutro-
phication study had excessive color or turbidity to permit such
an evaluation.
This relationship would also not hold for water bodies
whose excessive phosphorus loadings were manifested principally
293
-------
in excessive macrophyte growths and attached algae, rather than
in nuisance planktonic algal blooms. Such water bodies tend
to have a larger Secchi depth than would be expected on the
basis of phosphorus loadings alone since a portion of the phos-
phorus input would be incorporated into the macrophytes rather
than into the phytoplankton. Finally, this relationship would
hold only for those water bodies whose phosphorus loadings were
relatively constant (i.e., in an equilibrium state). This is
because the phytoplankton populations and, hence, chlorophyll
content of a water body, are a function of the phosphorus concen-
tration, which in turn is a function of the phosphorus loading
to the water body. The relationship between the phosphorus con-
centration in a water body and the phosphorus load to the water
body is a complicated one (Vollenweider, 1968), being a function
of the water body's mean, depth, hydraulic residence time,_in-
ternal loading, aquatic plant population, etc. However, if the
phosphorus load is relatively constant over the annual cycle, it
can be expected that the mean total phosphorus concentration is
also relatively constant over the annual cycle. Under such
equilibrium conditions, the use of Figure 79 to predict Secchi
depth as a function of a water body's phosphorus loading character-
istics should present no problems. On the other hand, if the
phosphorus load to a water body is increased or decreased signifi-
cantly, as in a sewage diversion project or the introduction of
sewage treatment plant effluent to a water body, then the rela-
tionship expressed in Figure 79 would likely not be valid for
prediction of Secchi depth. As discussed by Sonzogni et al.
(1976), a water body does not instantaneously adjust to a new
phosphorus load. Rather, a period of approximately three times
the phosphorus residence time is necessary for a water body to
adjust to a new phosphorus load. After this time period, assuming
the phosphorus load has not been further changed since an initial
increase or decrease, one could expect to again be able to use
Figure 79 to predict Secchi depth in a water body as a function
of its phosphorus load characteristics. It should be noted
that this represents a simple, quantitative and practical method-
ology for determining what the expected Secchi depth will be in
a water body in response to a sewage diversion or advanced treat-
ment project, prior to initiation of the project.
If one examines the phosphorus loading and Secchi depth data
for Lake Washington (Vollenweider, 1976a; Edmondson, 1975a), the
1964 phosphorus loading for Lake Washington, at the -initiation
of its sewage diversion project, gives it an (L(P)/qs)/(l+/z/qs)
value of approximately 100 (Vollenweider, 1976a). This corresponds
to a Secchi depth of about 1.6 m. Edmondson reported a mean
Secchi depth for Lake Washington in 1964- to be 1.2 m. However,
the phosphorus loading, had been increasing dramatically since 1957
(i.e., (L(P)/qs)/(l+/z/qs) value of approximately 40 in 1957 and
1964 value of 100), and consequently the relatively poor prediction of
Secchi depth was not unexpected. However, as noted earlier in
Table 21, the phosphorus residence time for Lake Washington was
approximately one year in 1964. Thus, according to Sonzogni et al.
(1976), one could expect a new phosphorus concentration equilibrium
294
-------
condition in about three years. However, the sewage diversion
project, although begun in the early 1960Ts, was not completed
until about 1968. Therefore, by 1972-1973 at the latest, one
could expect phosphorus equilibrium conditions to again exist.
In fact, if one examines the phosphorus loading expression
value for Lake Washington in 1971 and 1974 (Vollenweider, 1976a)
and compares the Secchi depth predicted in Figure 79 (i.e., 3.7 m
and 3.5 m, respectively) with the mean Secchi depth reported by
Edmondson (i.e., 3.5 m and 3.8 m, respectively), they are quite
similar. The small discrepancies may exist because Vollenweider
(1976a) appeared to use slightly different phosphorus loadings in
his Lake Washington calculations than those reported by Edmondson
(I975a), at least for 1971. If one uses the phosphorus loadings
reported by Edmondson in 1971 in Figure 79, the predicted and
reported Secchi depths for that year are identical. Edmondson
(1975a) did not report phosphorus loadings for 1974, so it was
not possible to compare the predicted and observed Secchi depths
for that year based on his loadings. For this reason, the
(L(P)/qs)/(l+/z/qs) expression values indicated by Vollenweider
(1976a) were used to compare the predicted and observed Secchi
depth values for 1971 and 1974. Even so, the agreement between
these two Secchi depth values for 1971 and 1974 is quite good,
lending support to this approach in assessing water quality as
a function of several easily understood and measurable parameters.
It should be noted that, as was the case for the phosphorus load-
ing characteristic and chlorophyll a concentration relationship,
this new relationship also indicates that a relatively large
change in the phosphorus load must occur to water bodies in order
to show marked improvement in water clarity.
It is also feasible to develop a model which relates pnos-
phorus loads to the water quality parameter of hypolimnetic
oxygen depletion. This latter parameter is of concern because
of its implications for the development of anoxic conditions in
hypolimnetic waters, especially in eutrophic water bodies. The
consequences of anoxic conditions in the hypolimnion on the cold
water fisheries which usually populate this region of a water
body are obvious. The chemically-reducing conditions usually
found in an anoxic hypolimnion also have implications for water
quality. For these reasons, the development of a water quality
model relating phosphorus loads to hypolimnetic oxygen depletion
is discussed below.
Gilbertson e_t al. (1972) found a remarkably good linear
correlation between municipal phosphorus loads and hypolimnetic
oxygen depletion rates in the central basin of Lake Erie. Based
on the observed period of thermal stratification and the oxygen
levels in Lake Erie's central basin, Gilbertson e_t al. determined
that the critical oxygen depletion rate in the hypoTTmnion of Lake
Erie's central basin was about 2.7 mg 02/l/month. That is, a
hypolimnetic oxygen depletion rate of 2.7 mg 02/I/month during the
period of thermal stratification would produce a zero concentration
295
-------
of oxygen in the hypolimnion of the central basin of Lake Erie
by the end of a given summer. Examination of the historical
data for Lake Erie (Gilbertson e_t al. , 1972) indicates this
critical depletion rate corresponds~to the 1955 phosphorus loading
conditions of about 12,000 tons per year, and has been exceeded
every year since that time.
The observations of Gilbertson et al. suggest that a gen-
eralized approach relating phosphorus~loads and hypolimnetic oxygen
depletion would appear to be feasible for a wide range of water
bodies. One approach for developing such a relationship involves
the use of a model derived by Lasenby (1975) between areal hypo-
limnetic oxygen depletion and Secchi depth. Studying 14 lakes
in southern Ontario, and several other water bodies Lasenby re-
ported that a strong inverse relationship (r=-0.85) appeared to
exist between the areal hypolimnetic oxygen depletion rate and
Secchi depth in these water bodies, as follows:
2
log, n areal hypolimnetic oxygen depletion rate (mg 0,.,/cm /day)
= -1.37 log1Q Secchi depth (m) -0.65 (41)
An assumption in Lasenby 's model was that the quantity of seston
sinking into the hypolimnion was proportional to the quantity in
the epilimnion. Lasenby (1975) has indicated that the linear
development of his hypolimnetic oxygen depletion model suggests
that hypolimnetic oxygen consumption is not too sensitive to brief
changes in productivity and, therefore, relatively few measurements
should give a good estimate of oxygen depletion rates.
With the relationship expressed earlier between phosphorus
loading and growing season mean Secchi depth (Equation 40), and
using Secchi depth as the common variable, Equation 41 above was
used to derive a relationship between phosphorus loading and areal
hypolimentic oxygen depletion. This model was then tested using
US OECD data, as well as data presented by Welch and Perkins
(1977) for a large number of water bodies with a wide range of
trophic conditions. Examination of the data indicated that Lasenby 's
relationship, derived mainly from oligotrophic and mesotrophic
water bodies, tended to overestimate the areal hypolimnetic oxygen
depletion rates in the majority of the water bodies. Consequently,
it was decided to use simple linear regression techniques, as was
done with Figure 22, to determine the best relationship. The
following regression was obtained:
2
log, n areal hypolimnetic oxygen depletion rate (g O^/m /day)
= 0.467 log, n [(L(P)/q )/(l+z/q )] -1.07 (42)
J_ U S S
This relationship is illustrated in Figure 80, along with the
available US OECD data, as well as data furnished by Welch and
236
-------
Perkins (1977) for several other water bodies. The model refers
to the mean areal hypolimnetic oxygen depletion rate during the
period of thermal stratification. Since the oxygen depletion rate
is expressed on an areal basis, it can be applied to any hypo-
limnetic volume, regardless of size pr oxygen content. It should
be noted that the units of hypolimnetic oxygen depletion in Equa-
tion 42 are different from those presented in Equation 41.
Very few studies on hypolimnetic oxygen depletion were con-
ducted on the US OECD water bodies. Consequently, the data base
for testing this phosphorus load-hypolimnetic oxygen depletion
model (Equation 42) was not as large as that for either the phos-
phorus load and chlorophyll a. or Secchi depth models. Although
there is some scatter of the data in Figure 80, considering the
uncertainty in the data available for the phosphorus loads, hypo-
limnetic volume, area and oxygen concentration, thermal stratifi-
cation, etc., the agreement between the predicted and observed
values is reasonably good and provides support for this model
as a predictive management tool for assessing the effects of a
given phosphorus load on the hypolimnetic oxygen depletion in a
water body. Further details concerning this model are presented
in Rast (1977).
APPLICATION OF RESULTS FOR ASSESSING WATER QUALITY IN LAKES AND
IMPOUNDMENTS
The approach presented in this section of this report can be
used to assess the potential effects of phosphorus load reductions
on water quality in lakes and impoundments. Assessments of this
type are becoming increasingly important in developing the most
cost-effective phosphorus control strategies for these water bodies.
In the past, eutrophication control strategies were frequently based
on the removal of phosphorus from its most readily controllable
sources, without any quantitative assessment possible beforehand of
the magnitude of water quality improvement that would result from
controlling the phosphorus input to a certain degree. The implemen-
tation of Section 314-A of PL 92-500 will require water pollution
regulatory agencies throughout the US to develop nutrient control
strategies for those water bodies which are found to be excessively
fertile. As a result of the US OECD eutrophication program, it
will now be possible for these agencies to quantitatively assess
the magnitude of water quality improvement that can be achieved
as a result of a phosphorus input reduction of a certain amount.
This section of this report discusses the application of these
results to a hypothetical situation which is likely to be typical
297
-------
r-O
CD
CO
z
o
H
LJ
_J
CL
LJ
Q
LJ ^
>- ?
vv j"*
O v.
C\J
- 1 '
LJ o™
~z?
^~ CT*
O
CL
X
_,
<
LJ
** n \
-
log oreol
H— CENTRAL
O
hypolimnetic oxygen depletion (gOo/171 /day)
0.467 log[(L(P)/qs)/(l + v/r;7')]- 1-07
BASIN OF LAKE ERIE
( Year of Data Record )
• — US OECD WATER BODIES
(See Table
14 For Identification Key)
A — WASHINGTON, USA, AND ONTARIO, 03 ^*
CANADA, WATER BODIES ^*
(Data Taken From, And Water Bodies 34 ^•^^
Identified
—
-
-
-
A
.^
^ ,
In, Welch And Perkins, 1977) ^ • ^>*^
' D ^^
• * 4I 13 ^* ~
• ^
45 441^9
> ^^ **
A ^AT^^dgei) _
A A *r^ m "
**f£ • (1966)
^^^^ m (1956)
^•^^ ^^ A A
^^^^ 1 I Q * 1 \ ^^^_ ^& ^K
^^^ \ i y ^ i / ^^^B A^ / 1 Q ^ 1 1 £A
(1931) • A
A(0.06) A
i i if i ill I i i i i i i i 1 i i i i i i i i
100
Figure 80.
10
( mg/m3)
Phosphorus Loading Characteristics and Hypolimnetic
Oxygen Depletion Relationship in Natural Waters
1000
-------
of what pollution control agencies will encounter as they attempt
to implement Section 314-A of PL 92-500. The approach taken in
this section is patterned after the approach developed by Rast
(1977) and used by Lee (1976) and Lee et_ al. (1977) to assess the
improvement in water quality that would occur in the Great Lakes as
a result of a phosphate detergent ban in the State of Michigan.
A hypothetical phosphorus loading situation has been con-
ceived in this section to illustrate the use of the approach des-
cribed above for assessing the potential effects of phosphorus
load reductions on water quality in a water body. Several phos-
phorus load reduction possibilities are considered. The phosphorus
loads and other pertinent data for analyzing the potential effects
of phosphorus load reductions are summarized in Table 28. In this
hypothetical water body, the point source inputs are 56 percent of
the total phosphorus load, with non-point sources comprising the
other 44 percent. The initial phosphorus loading is the hypo-
thetical load for 1975 and consists of both point sources (domestic
wastewater treatment plants) and non-point sources (land runoff
and atmospheric inputs). As shown in Table 28, in this hypothet-
ical example, the point source phosphorus load is 6.6 million
kg/yr, while the nonpoint phosphorus load is 6.2 million kg/yr.
For an assumed surface area of 2.6 X lO^O m?, this corresponds
to an areal loading of 0.46 g P/m^/yr. The first modified phos-
phorus loading considers the effects of a detergent phosphate ban
on the loading to the water body. It was determined by Lee (1976)
that a detergent phosphate ban would result in approximately a 35
percent reduction in the amount of phosphorus in domestic waste-
waters. This percentage value was used in these examples. This
would reduce the phosphorus input to the hypothetical water body
from this source by the same magnitude. This reduction would change
• C R
the point source phosphorus load from 6.6 x 10" kg/yr to 4.3 x 10
kg/yr, and reduce the overall areal load from 0.46 to 0.37 g P/m /yr
The second modified condition considers the effects of a 90
percent phosphorus removal from the domestic wastewater treat-
ment plant loadings. In this case, it will simulate the effects
of advanced waste treatment for phosphorus removal on the point
source load to the water body. The 90 percent removal reduces the
point source phosphorus load to 6.6 x 10"3 kg/yr, and the overall
areal load to 0.23 g P/m^/yr. The third modified phosphorus load-
ing simulates the effect of advanced waste treatment on the sewage
treatment plant inputs plus phosphorus loading reduction from the
non-point sources. In this case, it will simulate the effects of
advanced waste treatment phosphorus removal techniques on land
runoff.
Figure 81 presents the Vollenweider phosphorus load and mean
depth/hydraulic residence time relationship for this hypothetical
water body. Included in Figure 81 are the expected changes in
phosphorus loading for each of the phosphorus loading reduction
scenarios described above. Examination of Figure 81 shows that
the phosphorus load for 1975 places the water body in the eutrophic
299
-------
Table 28. SUMMARY OF DATA FOR HYPOTHETICAL
WATER BODY UNDER SEVERAL PHOSPHORUS
LOAD REDUCTION SCENARIOS
A) Morphometric and Hydrologic Data:
1) Volume = 4.55 x 10i:Lm3
in 9
2) Surface area = 2.6 x 10 m
3) Mean depth (volume/surface area) = 17.7 m
4) Hydraulic residence time (volume/annual inflow volume) =
2.6 yr.
5) Phosphorus residence time (phosphorus content/phosphorus
load) = 0.56 yr.
B) Phosphorus Loading Data:
1) 1975 phosphorus load -
a) point sources3: , 6.6 x 10,. kg/yr
b) non-point sources : 5.2 x_10 kg/yr
total load = 1.2 x 1C7 kg/yr
~ 0 .46 g P/m2/yr
2) 1975 phosphorus load minus detergent phosphate -
a) point sources3: , 4.3 x 10_ kg/yr
b) non-point sources : 5.2 x 10 kg/yr
total load = 9.5 x 106 kg/yr
0.37 g P/m2/yr
3) 1975 phosphorus load minus 90 percent point
source loading -
a) point sources3; , 6.6 x 10 kg/yr
b) non-point sources : 5.2^ x 10 kg/yr
total load = 5.8 x 10 kg/yr
0.23 g P/m2/yr
4) 1975 phosphorus load minus 90 percent point
source loading minus 40 percent non-point
source loading -
a) point sources3: , 6,6 x 10g kg/yr
b) non-point sources : 3^.1_ x 10 kg/yr
total load = 3.7 x 10 kg/yr
0.15 g P/m2/yr
Explanation:
aassumed to consist solely of sewage treatment plant inputs.
'-'includes atmospheric inputs.
300
-------
10
EUTROPHIC
ZONE
EXCESSIVE
/LOADING
PERMISSIBLE
/LOADING
I
o
z
o
_J
tr
o o.i
i
Q.
ir>
O
I
0.
1975 P-Lood Minus
Detergent P-Lood
1975 P-Lood Minus 90 Percent
1975 P-Lood
1975 P-Lood Minus 90 Percent
Point Source P-Lood ond
40 Percent Nonpoint Source
P-Lood
OLIGOTROPHIC
ZONE
0.01
_L
I I I I I III
J I I I I III
O.I
I 10
MEAN DEPTH,z/HYDRAULIC RESIDENCE
(m/yr)
100
1000
Figure 81. Phosphorus Loading and Mean Depth/Hydraulic Residence
Time Relationship as Applied to Hypothetical Water Body
Under Several Phosphorus Loading Scenarios
301
-------
zone of the Vollenweider phosphorus loading diagram, based on
the water body's mean depth and hydraulic residence time charac-
teristics. When the detergent phosphate ban is considered,
there is a discernible decrease in the phosphorus load (e.g.
approximately 20 percent decrease in total phosphorus load),
as indicated in Figure 81. It is important to note that Figure
80 is based on total phosphorus loadings to the hypothetical
water body, which may not properly reflect the phosphorus in-
put which is available for utilization by the phytoplankton
populations in the water body. It is reasonable to suggest
that the decrease in the available phosphorus fraction of the
phosphorus load to the hypothetical water body will be somewhat
less than shown in Figure 81,.
If the point source load is reduced by 90 percent, as
would be seen with advanced waste treatment phosphorus removal
techniques, there is a relatively large decrease of approximately
50 percent in the total phosphorus load. This would place the
hypothetical water body in the mesotrophic zone of the Vollen-
weider diagram, based on its mean depth and hydraulic residence
time characteristics. The reduction of the phosphorus input
from non-point sources can potentially be achieved by a variety
of means such as control of agricultural use of fertilizers and
animal manures, improved street sweeping to minimize phosphorus
derived from urban drainage, and/or the control of atmospheric
inputs of phosphorus. As shown in Table 28, a 90 percent point
source and 40 percent nonpoint source phosphorus removal program
reduces the areal phosphorus load to 0.15 g P/m^/yr. The impact
of advanced waste treatment for point source phosphorus removal,
plus control of the diffuse sources, places the hypothetical water
body in the oligotrophic zone of the Vollenweider phosphorus load-
ing diagram (Figure 81). As discussed in another section of this
report, it is important to emphasize that a change in the position
of a water body, based on an altered phosphorus load, from just
above, or just below, the excessive and permissible loading lines
in a Vollenweider phosphorus loading diagram does not necessarily
translate into a significant change in water quality. A lake may
change from the eutrophic to mesotrophic zone as a result of an
altered phosphorus load and still not experience a significant
change in water quality.
Figures 82, 83 and 84 can be used to evaluate the expected
changes in water quality resulting from various phosphorus loading
reduction scenarios. In order to inject realism into the use
of this model, as well as the others developed in this section,
it will be assumed that the chlorophyll a concentration of the
hypothetical water body does not lie exactly on the line of
best fit. Changes in the water quality parameters can then be
determined by moving the data point parallel to the line of
best fit in the model. Table 29 and Figure 82 indicate a chloro-
302
-------
10
0>
o:
i-
\±)
o
z
o
o
o!
X
Q_
O
-------
20
log Secchi Depth--0.473 log [chlorophyll a] + 0.803
co
CD
-F
Z 10
v
E
Q.
LJ
Q
X
o
o
u
(/>
z
<
UJ
2
1975 P-Load Minus 90 Percent
Point Source P-Load and
40 Percent Nonpoint Source
P-Load
1975 P-Load Minus 90 Percent
Point Source P-Load
1975 P-Lood Minus
Detergent P-Lood
1975 P-Load
i i
1 1 1
I I 1
0.5
10
100
Figure 33.
MEAN CHLOROPHYLL a CONCENTRATION (p. g/l)
Secchi Depth and Mean Chlorophyll £ Relationship as Applied to Hypo-
thetical Water Body Under Several Phosphorus Loading Scenarios.
-------
100
log Secchi Depth = -0.359log[(L(P)/Qs)/(l+./z/qs)] 40.925
in
Q)
jr
X
h-
0_
LJ
O
X
O
o
LJ
CO
<
LJ
10
!975P-Lood Minus
90 Percent Point Source
P-Lood ond 40 Percenl
Nonpoint Source P-Lood
!975P-Lood Minus
90 Percent Point Source
1975 P-Lood Minus
Detergent P-Lood
1975 P-Lood
10
100
(mg/m )
Figure 84. Phosphorus Loading Characteristics and Secchi
Depth Relationship as Applied to Hypothetical
Water Body Under Several Phosphorus Loading
Scenarios.
305
-------
GO
O
CD
z
o
LJ
_J
CL
LJ
O
O
CL
LJ
o:
10
o E 1
O.I
o
log oreol hypolimnetic oxygen depletiontgOg/m /day)
= 0.467 log[(L(P)/qs)/(l+v'T5J")j-l.07
1975 P-Load minus90%
Point Source P-Load 8
40% Non-point Source
P-Load-
» 1975 P-Load
975 P-Load minus
Detergent P-Load
975 P-Load minus
90% Point Source
P-Load
i i i i i
i i i i
10
100
1000
Figure 85.
(mg/m3)
Phosphorus Loading Characteristics and Hypo!imnetic
Oxygen Depletion Relationships as Applied to
Hypothetical Water Body Under Several Phosphorus
Loading Scenarios
-------
phyll a concentration of 6.5 yg/1, based on the 1975 phosphorus
load. ~0n the basis of a detergent phosphate ban alone, there will
be a decrease of approximately 1.0 yg/1 in the chlorophyll a con-
centration of the hypothetical water body. It should be noted that
changes of this magnitude are frequently within the experimental
error normally associated with chlorophyll a_ measurements on a
lake-wide basis. On the other hand, a noticeable change will
be seen when the 90 percent point source phosphorus removal
scenario is considered. The mean chlorophyll a concentration
will drop from about 6.5 yg/1 to 3.9 yg/1, a decrease of approxi-
mately 40 percent. A decrease of this magnitude is significant
and a noticeable increase in water quality, as reflected in
chlorophyll a content, would likely result in this hypothetical
water body. Finally, if a 90 percent point source and a 40
percent non-point source phosphorus reduction are considered,
an additional decrease of 1,1 yg/1 chlorophyll a will be seen.
The chlorophyll a concentrations will have decreased from 6.5 yg/1
to 2.8 yg/1. ThTs constitutes a 57 percent decrease in the
total chlorophyll a concentration in the water body compared
to a 66 percent decrease in the total phosphorus load. This
low chlorophyll a level is typical of unproductive water bodies,
and would be consistent with the oligotrophic status of the
hypothetical water body as indicated in the Vollenweider phos-
phorus loading diagram (Figure 81).
The changes in Secchi depth which would be expected to
result from the various phosphorus load reductions are indicated
in Table 29 and Figures 83 and 84. The predicted Secchi depth
based on the hypothetical 1975 phosphorus load will be approxi-
mately 2.6 m. If a detergent phosphate ban is considered,
the Secchi depth will increase approximately 0.2 m. This is
equivalent to an increase of about 8 percent resulting from a
35 percent reduction in the point source loading. As with the
chlorophyll a_ concentration, this amounts to an essentially
undetectable change in the Secchi depth on the basis of a deter-
gent phosphate ban alone in the hypothetical water body. The
change is more significant when the 90 percent reduction in
point source phosphorus loads is considered. The Secchi depth
increase will be 0.8 m, a definitely discernible Secchi depth
increase of about 30 percent for the 50 percent decrease in
the total phosphorus load. Finally, when both the 90 percent
point source and 40 percent non-point source phosphorus load
reduction is considered, the Secchi depth increases from 2.6
to 3.9 m, an overall increase of 1.3 m. This constitutes a
33 percent overall increase in Secchi depth for a 66 percent
overall decrease in phosphorus load.
307
-------
The hypolimnetic oxygen depletion rate changes to be
expected from the various phosphorus loading scenarios is
indicated in Figure 85. The predicted 1975 areal hypolimnetic
oxygen depletion rate is 0.60 g C^/m^/day. When the
detergent phosphate ban is considered, the rate decreases
approximately 0.1 g 02 for each m? of hypolimnetic area.
This is a 17 percent decrease for a 33 percent decrease in
the point source phosphorus loading. The 90 percent point
source phosphorus loading reduction results are more signifi-
cant, with the hypolimnetic oxygen depletion rate dropping
to 0.37 g 02/m^/day. This corresponds to a 38 percent
decrease in the oxygen depletion rate for a 50 percent
reduction in the phosphorus load. When both the point and
non-point phosphorus load reductions are considered, the
hypolimnetic oxygen depletion rate decreases to 0.32 g
02/m2/day, an overall decrease of 47 percent for an overall
66 percent reduction in the phosphorus load to the hypothetical
water body.
The improved water quality associated with 40 percent
control of phosphorus from diffuse sources will almost
certainly be less than that predicted in Table 29. As a
result of the fact that many diffuse sources of phosphorus
such as urban and rural drainage and the atmosphere usually
have large parts of their phosphorus in a particulate form,
much of which is unavailable to support algal growth.
Several points should be noted on the use of this
approach. First, it is important to emphasize that the
magnitude of the changes discussed in the chlorophyll a_
or Secchi depth relationships refer to changes associated
with planktonic algal growth. At present, there is no
information available for reliably predicting the effects of
a reduced phosphorus load on the growth of Cladophora and
other attached algae, as well as the growth of macrophytes
and floating macrophytes, such as water hyacinths and duckweed.
There is also no information available for reliably predicting
the effects of a phosphorus load reduction on water clarity
in the nearshore waters of a water body. Further, water
bodies will not adjust immediately to an altered phosphorus
load. Rather, it will require a period of time equal to three
308
-------
Table 29. SUMMARY OF PHOSPHORUS LOADING CHARACTERISTICS,
CHLOROPHYLL a AND SECCHI DEPTH OF HYPOTHETICAL
WATER BODY UNDER SEVERAL PHOSPHORUS LOAD
REDUCTION SCENARIOS
Phosphorus
Loading
Si tuationa
(L(P)/q )/(!+ Jz/(\ )
S Q S
( mg/m* )
Hypolimnetic
Chlorophyll a Secchi Depth Deoletion
t) f \ C /
((JR/t) vm; (gO^/m /lay)
CO
CD
ID
1975 Phosphorus
Loading
1975 Phosphorus
Loading Minus
Detergent Phos-
phate
1975 Phosphorus
Loading Minus
90% Point Source
Loadi ng
1975 Phosphorus
Loading Minus 90%
Point Source and
i|0% Non-Point
Source Loading
25 .9
20 .8
13 .0
8 .4
6 .5
5 .5
3.9
2.8
2 .6
2.8
3 .'I
3.9
0.32
Phosphorus loadings were taken from Table 28.
As determined in Figure 83, based on phosphorus load characteristics indicated in this
table.
°As determined in Figure 8f, based on phosphorus load characteristics indicated in this
table.
As determined in Figure 85, based on phosphorus load characteristics indicated in this
table.
-------
phosphorus residence times (Sonzogni et a1., 1976) before a
new equilibrium condition will be established in the water body.
The models presented in Figures 22, 79, and 80, may be appli-
cable when a new equilibrium state is reached in a water body.
For example, the use of this approach predicts a chlorophyll a_
concentration in Lake Ontario of about 4.5 yg/1, based on its
1973 phosphorus load. However, chlorophyll a values reported by
Dobson (1975), the International Joint Commission (1976b) and
Vollenweider (1976a) are in the order of six to eight yg/1 for
the openwaters of Lake Ontario. These higher values are possibly
due to a non-equilibrium condition of Lake Ontario resulting
from its reduced phosphorus load. Lake Ontario has not yet had
sufficient time to respond to this reduced phosphorus load. How-
ever, the use of these models in successfully predicting
chlorophyll a concentrations and Secchi depths in Lake Washington
following completion of its sewage diversion project, which was
discussed earlier in the section, lends considerable support to
these approaches in assessing the resulting water quality in a
water body following a change in its phosphorus load. When this
approach is applied to the Great Lakes, the results obtained with
the use of Figures 22, 78, 79, and 80 are in general agreement with
the observations of Gilbertson et aJL. (1972), Vollenweider et al.
(1974) and Dobson (1975) concernTng the Great Lakes.
In the Great Lakes consideration has to be given to the
fact that the nearshore waters of the lakes often have elevated
concentrations of nutrients compared to the open water. This
situation arises from the strong longshore currents which tend
to be present in large water bodies and which inhibit mixing of
nearshore with offshore water. Under these conditions, a differ-
ent mean depth/hydraulic residence time relationship should be
used in order to predict nutrient load-response relationships
than would be applicable to the open waters of the lakes.
Results of computations such as those presented above on
nutrient load-response relationships provide water quality
managers and the public with the information needed to evaluate
the magnitude of water quality improvement associated with a
particular nutrient control strategy. In order to develop a
meaningful nutrient control program it is necessary to evaluate
the costs associated with each approach. The cost of each
nutrient control program and the degree of water quality im-
provement can be used to choose the most cost-effective control
310
-------
program. Prior to the development of these relationships be-
tween phosphorus loading and water quality, as measured by
chlorophyll a concentrations, Secchi depth, and hypolimnetic
oxygen depletion, there was no readily available, and reliable,
method for predicting the expected improvement in water quality
resulting from a reduction in the phosphorus loading to a
water body by a certain degree. Water quality managers can now
develop cost-effective eutrophication control programs in which
they can inform the public of the degree of improvement in water
quality expected to result from expenditure of funds by a certain
amount. The taxpayers can then decide how much they are willing
to pay for improved water quality.
APPLICATION OF RESULTS TO IMPLEMENTATION OF SECTION 314-A
OF PUBLIC LAW 92-500
Section 314-A of PL 92-500 requires that each state clas-
sify its lakes and impoundments with respect to their degree
of fertility. Furthermore, the states must develop a nutrient
control program to minimize fertility in those water bodies
found to be excessively fertile. The results of this investi-
gation of the US OECD eutrophication study provide the states
and the federal government both with a basis by which this
type of classification can be made , and with the ability to
assess the improvement in water quality that is likely to re-
sult from a nutrient control effort of a certain magnitude.
From a water quality management point of view, the expected
improvement from a nutrient control program can be weighed
against the cost of achieving the nutrient control, and a
decision can be made as to whether the control effort will
result in a sufficient improvement in water quality to justify
the expense of the program. It is important to look on the
results of this study as a guide for implementation of public
policy in the area of excessive eutrophication of natural
waters. While Vollenweider, and others who have modified
his approach, have been able to formulate nutrient load-
eutrophication response relationships with a relatively simple
methodology, involving normalizing water bodies based on
their mean depth and hydraulic residence time, there are
many other factors which can influence the nutrient load-
algal response relationship in natural waters.
Examination of the various plots presented in this report
show there is considerable scatter in the data. Part of this
data scatter is due to differences in measurement techniques .
Another part is due to the inherent variabilitv of lakes and
impoundments. With respect to measurement, every point on any
of the nutrient load-response diagrams usually has considerable
311
-------
variance in both the x and y directions. One of the most diffi-
cult parameters to estimate for many water bodies is the hy-
draulic residence time. This factor is continuously changing.
A series of wet years could markedly affect the results com-
pared to more normal or dry conditions. For example, an im-
poundment in north central Texas shows a hydraulic residence time
from 0.3 years to 22 years, with a mean of about 4 years, depend-
ent upon wet and dry climatic cycles . In addition to variable
climatic patterns, another factor to be considered is that of
short-circuiting of the inflow and outflow waters, such that
the inflowing nutrients do not interact with the total water
body. This may be an especially significant problem for large,
deep impoundments. Under these conditions, a modification of
the hydraulic residence time term should be made to more properly
reflect the actual behavior of the nutrients in the impoundment.
This modification should reflect the fact that some of the
nutrients that enter a water body may leave it by way of outflow
before they have had the opportunity to interact with the phyto-
plankton.
The variance about the vertical displacement on the diagrams
in this report, for a phosphorus load, chlorophyll, Secchi depth
or hypolimnetic oxygen depletion response, is likely to be very
large under certain circumstances. The data presented in this
report are often based on a single year's measurements. Lakes
and impoundments respond to nutrients not only for the year in
which the nutrients are added, but for previous years' nutrient
inputs as well. Each water body would have an individual response
in this respect. Further work, which will not be reported in this
report , is being done by these authors to estimate the magnitude
of the associated variance that is likely to be encountered with
measurements of the various load-response relationships. From the
work done thus far, it is important that no regulatory agency re-
quire implementation of a control program because a water body's
phosphorus load plots just above the permissible or excessive
line on the diagrams presented in this report. Similarly, no
regulatory agency, or other group, should assume that because a
lake plots just below the excessive or permissible line, that
this lake will not have water quality problems due to excessive
fertilization.
Factors such as color, turbidity, morphological shape of
the water body basin, rainfall runoff patterns, characteristics
of the watershed, etc., all would have an influence on the
nutrient load-response relationships in natural waters, and all
contribute to the scatter of points in the various nutrient load-
response evaluations made in this study. One of the areas of
research that needs considerable additional attention, in attempt-
ing to reduce the scatter in the data, is that of'available
nutrients. In general, the various diagrams presented in this
312
-------
report are based on total phosphorus. It is well known that
only part of this total phosphorus is available. As a guide-
line, Cowen and Lee (1976b)have concluded that the best approach
for estimating the available phosphorus load to a water body
is that it is equal to the soluble orthophosphate load plus 20 per-
cent of the difference between the total phosphorus and soluble
orthophosphate load. This difference between the total and soluble
orthophosphate is made up of inorganic and organic forms which
are generally particulate. These results indicate that for
those water bodies in which the primary source of nutrients is
from agricultural or land runoff, a substantial part of the
phosphorus may not contribute to the algal-available load.
Another factor to consider concerns the amounts of available
phosphorus that reach a water body when the origin of the phos-
phorus load is a considerable distance from the water body.
For example, in the US-Canadian Great Lakes, some controversy
has developed concerning the significance of domestic wastewater
discharges many miles from the lake in influencing excessive
fertilization problems in the Great Lakes. If the wastewaters
enter a lake somewhere between their origin and the Great Lakes,
most of the nutrients would be retained in the intermediate lake,
since many water bodies trap from 60 to 90 percent of the
phosphorus that enters them by incorporation of the phosphorus
into the sediments. Further, as the available phosphorus added
to a stream some distance from the lakes mixes with the erosional
materials, and/or is utilized in various biological processes,
it is becoming less and less available for stimulation of algal
growths. It is likely that available nutrients discharged to
rivers which are considerable distances from the lake of interest
will have much less influence on stimulating extensive fertiliza-
tion problems than would the same nutrients discharged directly
to the water body.
Special consideration in assessing nutrient sources should
be given to septic tank wastewater disposal systems since a large
part of the US population utilizes this form of wastewater dis-
posal. A comprehensive review on the significance of septic
wastewater disposal systems as a source of phosphorus has recently
been completed by Jones and Lee (1977). They concluded that,
with few exceptions, the phosphorus present in septic tank domestic
wastewater disposal systems will have little influence on stimulat-
ing excessive fertilization problems in natural waters. Guidance
is provided by Jones and Lee in evaluating, on a case by case
basis, whether in a localized area excessive fertilization prob-
lems are caused by septic tank systems.
While this report has focused primarily on the application
of the Vollenweider loading approach to assessing water quality
in which the water quality problems are related to excessive
fertilization for whole bodies of water, it is applicable to
parts of a water body as well. A number of the lakes and impound-
ments investigated in this report were subdivided into various
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sections or arms. The results appear to indicate that this approach
is appropriate. Further, for large water bodies such as the Great
Lakes, the approach described in this report should be applicable
to bays and nearshore waters as well. In the case of the Great
Lakes, it is important to be able to estimate the exchange of
water between the nearshore and offshore zones, or between the
openwaters of the lakes and their bays. It is important to em-
phasize once again that the Vollenweider loading approach is
directly applicable to the management of water quality problems
associated with excessive fertility, as manifested in phytoplank-
ton growth which cause an impairment of recreational use of water.
Further research is likely to produce the information needed to
develop modifications of the Vollenweider loading relationship
for other water quality problems such as excessive growth of
macrophytes, attached algae, dissolved oxygen depletion in the
hypolimnion and impairment of water supplies for domestic and
industrial use. Further work, which will be reported by these
authors in subsequent reports, is being done along these lines
in order to define conditions for which the Vollenweider loading
approach is not applicable. It is already apparent from this
study that the Vollenweider approach must be modified for those
water bodies which show very short hydraulic residence times
because the nutrients entering into the water body could pass
through it before interacting with the phytoplankton and thus
would not produce an algal crop in the water body proportional to
its nutrient loading. In these cases, the Vollenweider loading
approach, in its present form, would be inappropriate for
assessing the eutrophication status of the water body.
AN APPROACH FOR THE USE OF THE VOLLENWEIDER NUTRIENT LOAD-WATER
QUALITY PROGRAM
The procedures that should be utilized in applying the Vollen-
weider loading relationship for the development of a water quality
management program designed to Improve water quality or minimize
future deterioration are presented below.
1. Determine the limiting nutrient. Since the Vollenweider
loading relationship was derived for phosphorus, the first step
in its application would be to determine whether phosphorus or
nitrogen is the limiting nutrient in the water body. This assumes
that all other factors affecting algal growth (i.e., light and
temperature) do not limit the maximum algal biomass that will
develop and that it is the concentration of the limiting nutrient ,
relative to the stochiometric needs of the algae, which controls
or limits the deterioration of water quality.
The limiting nutrient can usually be determined by several
techniques, including N:P ratios, bioassay studies or simple ob-
servation of the available nutrient concentration dynamics over
the seasonal and/or annual cycle (Lee, 1973). The use of the
growing season inorganic nitrogen: soluble orthophosphate mass
ratio (expressed as N:P) in a water body was discussed in an
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earlier section of this report (see Tables 9 and 10). Bioassay
techniques can also be used to determine the limiting nutrient in
a water body. The algal assay procedure provides a standardized
test for identifying algal-growth-limiting nutrients in water
bodies, for determining the biological availability of algal
growth-limiting nutrients, and for quantifying algal responses
to changes in concentrations of the nutrients (Sridharan and Lee,
1977). An estimate of the limiting nutrient can be obtained by
observing the dynamics of the available nutrients during the grow-
ing season. If one of the algal-available nutrient forms becomes
depleted in a water body at the same time that the other is still
present in large quantities, it is usually reasonable to assume
that the depleted nutrient may be the algal-growth-limiting
nutrient.
If it is determined that nitrogen, rather than phosphorus,
is the aquatic plant growth-limiting nutrient, then two options
are available. One can either attempt to control the nitrogen
loading, or else reduce the phosphorus loadings to such an extent
that phosphorus becomes the limiting nutrient. The latter course
of action is almost always preferred, for reasons mentioned in
earlier sections of this report (Vollenweider, 1968; 1975a; Lee,
1971; 1973; Vallentyne, 1974; Golterman, 1976). It does not
matter that nitrogen initially controls the algal growth in a
water body, but rather that phosphorus can be made limiting in
the water body. To determine if it is possible to change a water
body from nitrogen-limitation to phosphorus-limitation, one must
be able to assess the potential benefit that might be derived
from a reduction of phosphorus in a water body. Sridharan and
Lee (1977) have recently developed a technique for making such an
assessment. This procedure is based on studying the response of
algae to alum-treated lake water and has worked well for evalu-
ation of the potential benefit to be derived from a phosphorus
reduction in Lake Ontario. Based on the results of these types
of analyses, one can determine the limiting nutrient in a water
body, and make an evaluation of the potential benefits, in terms
of algal growth responses, to be derived from a decrease in the
phosphorus content of a water body.
2. Determine the available nutrient sources and significance
of each source. This step consists of quantifying the nutrient
loadings to a water body. It is first necessary to identify all
the sources of nutrient inputs, both point and non-point sources.
Sonzogni and Lee (1974) have presented an extensive examination
of the estimated nutrient loadings to Lake Mendota in 1972. The
approach used by Sonzogni and Lee is an example of how one may
assess the nutrient sources to a water body. They examined the
nutrient inputs from waste water discharges, urban, rural and
forest runoff, groundwater seepage, baseflow, nitrogen fixation
and from the atmosphere directly onto the lake surface. They
then determined the total nutrient loadings from these sources.
This same approach can be used to assess the nutrient sources
for most water bodies.
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Once the sources are identified, one may then quantify the
nutrient inputs for a water body. The loadings may be directly
measured or determined by indirect methods. If it is measured
directly, the sampling program should be sufficient to allow one
to determine the variability from a particular source. For ex-
ample, the amount of phosphorus from a sewage treatment plant can
be determined by measuring the phosphorus concentration in the ef-
fluent and multiplying this concentration by the flow. The result
will be the mass of phosphorus loading from this source. However,
the phosphorus concentrations in sewage treatment plants can vary
widely over a daily, weekly and monthly cycle. This variability
must be determined so that accurate loads from this major nutri-
ent source can be computed. Another case of variability involves
measurement of land runoff. According to Kluesner and Lee (1974),
the phosphorus concentration in urban runoff after a storm varies
widely, usually reaching a peak which is not coincident with the
peak runoff flow. Thus, the concentrations and flows may have to
be measured frequently during a storm if it is desirable to get
very accurate loading estimates during this period.
An alternative to direct measurement is to use watershed land
use nutrient export coefficients. This method was used in this
report and is described in detail in an earlier section. This
method is based on the fact that a given land use activity with-
in a watershed will produce a relatively constant nutrient ex-
port over an annual cycle (i.e., an acre of corn field or urban
area will produce about the same annual export of phosphorus and
nitrogen). Thus, loadings to a given water body can be determined
on the basis of land use type in the water body's watershed and
use of the appropriate nutrient export coefficient. A number of
studies concerning export coefficients for various land uses have
recently been completed (Vollenweider, 1968; Sonzogni and Lee,
1974; US EPA, 1974c; Vollenweider and Dillon, 1974; Uttormark
et a_l. 1974; Dillon and Kirchner, 1975; Dillon and Rigler, 1975).
One can determine phosphorus and nitrogen loadings from sewage
treatment plants in a similar manner. Several studies have been
conducted to estimate per capita nutrient concentrations in
domestic wastewaters (Vollenweider, 1968; Sonzogni and Lee, 1974;
Dillon and Rigler, 1975). One may use these reported values or
experimentally determine the per capita loadings by direct measure-
ments. The reader is referred to these various studies for ap-
propriate nutrient export coefficients on per capita inputs. If
it is felt that a given export coefficient is not accurate for a
given land use, an alternative is to directly measure the nutrient
runoff from a land use type in the watershed and formulate one's
own coefficients.
Using these methods, the loadings of total phosphorus and
nitrogen, as well as algal-available phosphorus and nitrogen to
a water body can be computed. One can also then evaluate the
relative significance of each source if it is necessary to choose
between controlling the input from several sources. The nutrient
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loadings from domestic sewage treatment plants is usually one of
the most significant sources for most water bodies. One should al-
so evaluate the loadings of available nutrients versus the loadings
of total phosphorus and nitrogen, since the available nutrients are
the ones assimilated by algal populations in water bodies. As
mentioned earlier (Cowen and Lee, 1976b), the best estimate of the
loading of available phosphorus is that it is equal to the sum of
the available phosphorus loading plus 20 percent of the difference
between the total phosphorus and available phosphorus loading.
3. Assess the nutrient load-eutrophication response relation-
ships . When an estimate of the available phosphorus loading is
available, the next step is to assess the relationship between the
loading and the eutrophication responses of a water body. This
assessment assumes that the computed phosphorus loading is accurate.
The accuracy of the phosphorus loading estimate, whether measured
or computed using nutrient export coefficients , can be checked us-
ing the relationship developed by Vollenweider between the ratio of
the mean total phosphorus concentration to the influent phosphorus
concentration and the hydraulic residence time (see Equation 26
and Figure 14). This approach was presented in an earlier section
of this report. The phosphorus and nitrogen loading estimates, if
they were directly measured, could also be checked using appropriate
watershed nutrient export coefficients.
After the reasonableness of the loading estimates, particular-
ly phosphorus, has been determined, the relationships presented
in earlier sections of this report can be used to assess the rela-
tive degree of oligotrophy or eutrophy of a water body. The
critical phosphorus loading levels can be determined for a water
body. Also, the expected enhancement or deterioration of water
quality following a phosphorus loading reduction or increase,
respectively, can be evaluated. This can be done in a manner
completely analagous to that presented by Lee (1976) concerning
the expected effects of a phosphate detergent ban in the State of
Michigan on v.'ater quality in the Great Lakes.
The relative trophic condition of the water body can be
determined using the Vollenweider phosphorus loading and mean
depth/hydraulic residence time relationship (Figure 19). To
evaluate the water quality, the relationship between phosphorus load-
ing and mean epilimnetic chlorophyll a concentration in a water body
can be determined with the use of Figure 22. One can next determine
the expected water clarity for a given phosphorus load with the
use of Figure 79. If a large quantity of data is available for a
water body concerning its chlorophyll a concentrations and cor-
responding Secchi depths , one can construct a Secchi depth and
chlorophyll a concentration diagram specific for that water body.
This can be transformed into a phosphorus load characteristics
and Secchi depth diagram in the same manner as was done with
Figure 79. Otherwise, Figure 79 can be used in its present
form.
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One could also use these relationships to evaluate the
expected changes in water quality in a water body in future years
as a function of future changes in phosphorus loads. Figures 19,
22,79 and 80 can be used in the same manner as indicated above for
evaluating expected future phosphorus loads. Particularly,
Figure 19 can indicate the expected relative changes in trophic
condition resulting from an altered phosphorus load. Figures 22, 79
and 80 can be used to predict the expected changes in mean
chlorophyll a concentrations, Secchi depth and hypolimnetic oxygen
depletion for an altered phosphorus load.
4. Evaluate cost-benefit analysis of eutrophication control
program. Most eutrophication control programs are based on reduc-
tion of phosphorus loads to a water body. As indicated above, the
expected water quality changes can be evaluated for a given phos-
phorus load reduction. The final question then involves the cost-
benefit of any given eutrophication control program. Previously,
eutrophication control programs based on phosphorus load reduction
were largely subjective in nature. The use of the above-mentioned
relationships provides individuals concerned with water quality
management with a quantitative tool to evaluate expected changes
in water quality resulting from eutrophication control programs
based on reduction of phosphorus inputs. The final question to
be answered concerns evaluation of the relative monetary worth of
such a eutrophication control program. Do the results of a phos-
phorus removal or sewage diversion program, for example, justify
the funds expended for the project? In short, is the final ex-
pected product worth the money?
This final question brings social, economic and political
considerations into the overall picture. Lee (1971; 1973) and
Vollenweider and Dillon (1974) have determined that widespread
use of phosphorus removal programs is economically feasible.
Lee (1971; 1973) has determined that phosphorus removal from
domestic wastewaters is possible for a cost of about one cent
per person per day. It is then up to those individuals con-
cerned with water quality management to determine if it is worth
one cent per person per day to produce a change in water quality
as predicted with the use of Figures 22, 79 and 80 For example, if
it is shown that the phosphorus loading to a water body can be
reduced by 60 percent by initiating advanced waste treatment for
phosphorus removal from domestic waste waters, and that such a
reduction will lower the mean chlorophyll a concentration from
10 yg/1 to 5 ug/1 and raise the Secchi depth from 1 meter to
2 meters, is the cost of building and operating the plant justi-
fied by the expected improvements in water quality? This will
have to be evaluated on an economic and political level since
such programs are usually ultimately funded by the taxpayers.
The important point to be made is that now the individuals who
must pay for eutrophication control programs can be shown in ad-
vance of the initiation of such programs what they will get in
terms of improved water quality for their money. They can then
decide, by whatever means they choose, whether the expected im-
provements are worth the expected costs to them.
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It is expected by these authors that additional quantitative
tools for evaluating predicted changes in water quality will be
developed in the future, providing further methodologies for
making water quality management cost-benefit analysis decisions.
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SECTION XII
TROPHIC STATUS INDEX STUDY
The US OECD data base offers an opportunity to examine the
comparability and to some degree the reliability of several recently-
proposed water body trophic status indices. This section of this
report is devoted to a review of these trophic status index schemes
and an analysis of the results of the trophic classifications of
the US OECD water bodies.
GENERAL CONSIDERATIONS
Lakes and other surface waters are characteristically divided
into two general categories, oligotrophic and eutrophic. Further,
it is generally agreed that mesotrophic describes water bodies in
a transition state between oligotrophic and eutrophic (Fruh et al.
1966; Vollenweider, 1968; Lee, 1971; Vallentyne, 1974). However^"
the exact meaning of these three terms is still debated among lim-
nologists because of a lack of understanding concerning details of
the eutrophication process, other than on a gross level, and its
effects on the aquatic environment.
Weber (1907, as cited in Hutchinson, 1969), was the first to
introduce the terms "eutrophic" and "oligotrophic." He used these
terms to describe the general nutrient conditions of soils in Ger-
man bogs. The succession of Weber's scheme ran from eutrophic to
oligotrophic as a submerged bog was built up to a raised bog. The
submerged bog was characterized as eutrophic or well-nourished,
while the raised bog was characterized as oligotrophic. Naumann
(1919, as cited in Hutchinson, 1969), introduced these terms into
limnology. Naumann used the term "eutrophic formation" to describe
a phytoplankton assemblage in nutrient-rich waters. Naumann (1931,
as cited in Stewart and Rohlich, 1967) later refined his definition
of eutrophication as "an increase of the nutritional standards (of
a body of water), especially with respect to nitrogen and phosphorus.'
As originally defined, eutrophic and oligotrophic referred to
water types (i.e., quality of water). However, the term has general-
ly come to refer to general lake types, including the physical,
chemical and biological characteristics of the water body and its
drainage basin (Brezonik et a1., 1969). The difficulty in defining
the terms oligotrophic an3~~eut"rophic is related to the fact that
these terms are used in different ways by different investigators.
Some use these terms to refer to aquatic plant nutrient flux, others
use them to describe plant and animal production, while even others
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Table 30. GENERAL CHARACTERISTICS FREQUENTLY
USED TO CLASSIFY WATER BODIES
General Characteristic
Parameter
Oligotrophic
Eutrophic
Aquatic plant production low
Algal blooms rare
Algal species variety many
Characteristic algal groups
high
many
variable to few
blue-green
Anabena
Aphanizomenon
Microcystis
Oscillatoria
rubescens
Littoral zone aquatic plant
growth
Aquatic animal production
Characteristic zooplankton
Characteristic bottom fauna
Characteristic fish
Oxygen in the hypolimnion
Depth
Water quality for most
domestic and industrial
use
Total salts or conductance
Number of plant and an-imal
species
sparce
low
abundant
high
Bosmina obturirostris B_. longirostris
B_. coregoni D_. cucullata
Diaptomus gracilus
Tanytarsus
deep-dwelling, cold
water fishes such as
trout, salmon and
cisco
present
tend to be deeper
good
usually lower
many
Chironomids
surface-dwelling,
warm water fish
such as pike,
perch and bass;
also bottom dwell-
ing fish such as
catfish
absent
tend to be
shallower
poor
sometimes higher
few
Taken from Fruh et_ al. (1966); Lee (1971); Vallentyne (1974)
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use them to describe the process of excessive discharge of aquatic
plant nutrients to a water body that results in water quality dete-
riotation (Lee, 1971).
Even though there is general agreement concerning a oligotrophic-
eutrophic succession scheme, the problem of the trophic status or
classification of a water body at a given point in time remains to
be considered. This illustrates a basic problem in lake classifica-
tion, namely that the exact classification of a water body is usual-
ly related to its intended use. A water supply reservoir manager
would likely have a much more stringent definition of eutrophic
than would a fisherman who was interested in fish production. They
would desire opposite ends of the trophic spectrum; hence, their
views of oligotrophy versus eutrophy would also likely be different.
However, there are some relatively widely-accepted general
characteristics used to characterize lakes. Table 30 summarizes
the commonly accepted characteristics of oligotrophic and eutro-
phic lakes. The reader is also referred to recent reviews of the
eutrophication process and its manifestations (Sawyer, 1966; Ameri-
can Water Works Association, 1966; Fruh et_ al., 1966; Stewart and
Rohlich, 1967; Vollenweider, 1968; Brezonik et_ aJL. , 1969; Federal
Water Quality Administration, 1969; National Academy of Sciences,
1969; Lee, 1971; Likens, 1972a; US EPA, 1973a; and Vallentyne,
1974) .
Examination of Table 30 shows that oligotrophic lakes tend to
have a low nutrient flux relative to their volume of water. They
contain small amounts of organisms, but many different species of
both aquatic plants and animals. In general, oligotrophic lakes
are deep, with average depths of 15 meters or greater and maximum
depths frequently greater than 25 meters (Vallentyne, 1974). How-
ever, this feature is highly variable. Further, as oligotrophic
lakes fill, due to sediment'deposition over time, they will tend to
become eutrophic (Lee, 1971). Oligotrophic lakes usually have high
dissolved oxygen concentrations in the hypolimnion during all
periods of the year, including the growing season. This oxygen-
containing, cool hypolimnetic region is the home of the trout,
walleye, cisco and other cold water prized game fish sought by
fishermen. The water quality is generally good the year round in
oligotrophic lakes. In general, oligotrophic lakes can be charac-
terized as deep, transparent water bodies with a low nutrient flux
relative to their ability to assimilate the nutrients.
By contrast, eutrophic water bodies have a high nutrient flux
relative to their water volume. As a result, they are highly pro-
ductive water bodies with large amounts of aquatic life, but of
somewhat fewer species than oligotrophic lakes. They are highly
productive at all trophic levels and frequently experience algal
blooms, especially during the growing season. Characteristic
algae include the nuisance blue-green species associated with
deteriorated water quality. The same is true for all other aquatic
life species. The fish are usually the "coarser" species not
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generally sought by most fishermen (though this may vary from loca-
tion to location). They are generally shallow, often with exten-
sive littoral areas with abundant plant growths. Mats of macro-
phytes and attached algae may carpet the littoral zone, depending
on competition between planktonic and attached plants and on the
normally higher turbidity waters in eutrophic water bodies. Eu-
trophic lakes deep enough to develop a thermocline usually show a
partial or complete dissolved oxygen depletion in the hypolimnion.
The extent of oxygen depletion will depend on the amounts of
aquatic plants that develop in the surface waters, and may become
super-saturated with oxygen due to the increased photosynthetic
activity at the surface. The surface water typically becomes
turbid in the summer as a result of algal growth, to the extent
that, with few exceptions, the amount of aquatic plants produced
will be restricted to the surface waters. Such turbidity restricts
light penetration to the epilimnetic waters, with the result that
the Secchi depth is usually three meters or less (in contrast to
the 10+ meters of some oligotrophic waters).
There also appears to be a correlation between the total dis-
solved salt content or conductivity and the increased primary pro-
ductivity, presumably because the higher salt content is related to
a high aquatic plant nutrient flux. In general, the overall water
quality is poor as a result of the increased nutrient flux and re-
sultant increased growth at all trophic levels.
In spite of these generally-accepted characteristics of pro-
ductive versus nonproductive, the problem of the absolute classifi-
cation of the trophic conditions of water bodies is still unsettled
Individuals tend to subjectively classify water bodies on the basis
of some of the common, though arbitrary, trophic state indicators
listed in Table 30 (i.e., nutrient concentrations, Secchi depth,
hypolimnetic oxygen depletion, chlorophyll concentrations, etc.).
A strict agreement is missing on what standards or values of these
and other parameters constitutes a given trophic state. This
interpretation still varies widely among investigators.
REQUIREMENTS FOR A TROPHIC STATUS CLASSIFICATION INDEX
The traditional water body classification scheme of oligotro-
phic, mesotrophic and eutrophic is inadequate for descriptive
purposes other than in a very broad sense (Shapiro, 1975b). As
a result, there has been a development of several trophic clas-
sification systems in an attempt to classify lakes on a quantita-
tive basis. A variety of characteristics of water bodies have
been used as a basis for various classification schemes and many
of the schemes use markedly different approaches.
An adequate trophic index scale or scheme is particularly
needed in view of the mandates of Public Law 92-500. Section
314-A of this law requires that each state classify its lakes
according to their trophic condition. Further, eutrophication
control measures must be initiated by the states in water bodies
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deemed to be excessively fertile. The question then arises as to
which classification or index scheme to use. The array of trophic
indices used in the past is both wide and diverse. These range
from determining recreational potential, management purposes and
scientific studies. The indices may be descriptive or analytical,
subjective or objective, simple or complex, relative or absolute,
biological, physical and/or chemical, etc. (Shapiro, 1975b).
There is need for a numerical trophic state index which will
permit a more appropriate assignment of the trophic condition of a
water body than the previous broad descriptions of oligotrophic,
mesotrophic and eutrophic. The index scheme should be simple,
based on practical parameters whose values can be determined rela-
tively easily and which do not require sophisticated methods of
statistical analysis. More complicated trophic classification
indices could be developed, but would likely have limited use.
An example of a more complex scheme is a trophic state index
based on the simultaneous use of multiple factors developed by
Shannon and Brezonik (1972). They based their multivariate ap-
proach on seven trophic state indicators, including primary pro-
ductivity, chlorophyll a, total phosphorus, total organic nitrogen,
Secchi depth, specific conductivity and Pearsall's cation ratio
(i.e., (Na+K)/(Ca+Mg)). Shannon and Brezonik applied their clas-
sification system to 55 lakes in Florida and found a good correla-
tion between the trophic status index values obtained using their
approach and the traditional trophic classification of these water
bodies. This index has problems based on the amount of data needed
for its use. For many water bodies, it is not always possible to
obtain all the data needed for classification. Shapiro has
criticized the Shannon and Brezonik approach since it tends to mis-
classify water bodies. According to Shapiro (1975b), when Shannon
and Brezonik (1972) applied their trophic index system to Lake Alice,
one of the 55 Florida lakes in their study, it had a TSI value of
10.7. This places it in a hypereutrophic category, relative to the
other lakes in their study. However, Lake Alice has a low primary
productivity and chlorophyll concentration, inconsistent with a
hypereutrophic water body.
Three trophic index schemes which show varying degrees of
promise have recently been developed. These include the trophic
classifications of the US EPA (1974d), Carlson (1974) and Piwoni
and Lee (1975). In addition, a trophic index system based on
Vollenweider's phosphorus loading diagram (Figure 19) has been
developed as part of this report. These classification schemes
are discussed below.
CURRENT TROPHIC STATUS CLASSIFICATION INDICES
US EPA Trophic Status Index System
The US EPA (1974d) Trophic Index System was developed as part
of the National Eutrophication Survey. This system is a variation
of a ranking method used by Lueschow et al. (1970) for 12 lakes in
Wisconsin. Lueschow et al. used several unweighted characteristics
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of a water body which each reflect, in one way or another, its
trophic condition. From these parameters Lueschow et al. derived
a composite rating which was the sum of the numerical values of
position for each of the parameters used in the index. The para-
meters used were dissolved oxygen (DO) 1 meter above bottom,
organic nitrogen, total inorganic nitrogen, Secchi depth and net
plankton. The water body with the lowest composite value was
judged the most oligotrophic and the highest composite value
lake was judged the most eutrophic.
The US EPA based their initial index system on 200+ lakes
surveyed in 1972 (US EPA, 1974d). Ultimately 812 lakes will form
the data base. However, rather than using the positional ranking
used by Lueschow et al., the US EPA adopted a percentile ranking
procedure. For each of the unweighted characteristics used, the
percentage of each of the 200+ lakes exceeding a given lake in
that parameter (i.e., chlorophyll a concentration, for example)
was determined. The final ranking or index value was simply the
sum of the percentile ranks for each of the parameters used. The
six parameters used in the US EPA Trophic Index System are sum-
marized in Table 31. The values for the Secchi depth and minimum
DO were subtracted from a fixed value (500 inches and 15 mg/1,
respectively) so that all parameters would contribute a positive
number to the ranking system. Using this system, a single index
number was produced for each lake, so that a large number of lakes
could be ranked in relative order from most oligotrophic to most
eutrophic. However, this system does have several problems.
This system sums the rankings for each parameter of a given water
body, and thus loses information concerning specific water body
characteristics. Furthermore, according to the US EPA (1974d),
water bodies with very short hydraulic residence times and those
with extensive littoral zones and excessive macrophyte production
do not seem to fit the scheme. In the first case, the high
flushing rates can cause relatively low mean nutrient concentra-
tions in spite of high nutrient loadings. In the latter cases,
the macrophytes may effectively compete with the algae for avail-
able nutrients, producing low nutrient and chlorophyll a levels
and relatively high Secchi depths in spite of a highly eutrophic
condition.
Table 31. US EPA TROPHIC STATE INDEX PARAMETERS
1. Median Total Phosphorus Concentration (mg/1).
2. Median Inorganic Nitrogen Concentration (mg/1).
3. 500 - Mean Secchi Depth (inches).
4. Mean Chlorophyll a (yg/1).
5. 15 - Minimum Dissolved Oxygen Concentration (mg/1)
6. Median Dissolved Phosphorus Concentration (mg/1).
Taken from US EPA (1974d).
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Carlson Trophic Status Index System
Carlson's (1974) Index System is based upon Secchi depth as
a means of characterizing algal biomass. As mentioned earlier,
this parameter, in the absence of turbidity and colored materials
in water, is a direct measure of planktonic-algal-manifested
eutrophication processes in natural waters. Its range of values
can easily be transformed into a convenient scale. Further, by
using empirically-derived relationships between Secchi depth and
both total phosphorus and chlorophyll a concentrations, Carlson
has derived equations to estimate the same index value from these
two parameters as well as from Secchi depth.
Carlson's Trophic Index is basically a linear transformation
of Secchi depth, such that each major unit in his scale has half
the value of the next lowest unit. Conversely, for total phos-
phorus and chlorophyll a each major unit in his scale has larger
values for the next higher unit. The computational form of the
equations for his trophic scheme is as follows:
TSI(SD) = 10(6-log2SD), (43)
TSI(Tp) = 10(6-log265 ip), and (44)
TSI(Chlor) = 10<6-log27.7 L_) (45)
Chlor0'68
where SD = Secchi depth (m) ,
TP = Total phosphorus concentration (yg/1),
and Chlor = Chlorophyll a concentration (yg/l).
Calculation of the indices is facilitated by using these three
equations:
TSI(SD) = 10(6 - In-f^' (46)
65
TSI,mT,N = 10(6 - JlL-S , and (47)
,n,c 2.04-0.68 In Chlor a
(Chlor) = 10(6 -TF-2 (48)
The trophic scale and associated parameter values are presented in
Table 32.
According to Carlson (1974), this index system has the
advantages of easily obtained data, simplicity of form (i.e.,
326
-------
Table 32. THE CARLSON TROPHIC STATE INDEX
AND ITS ASSOCIATED PARAMETERS
TSI
0
10
20
30
40
50
60
70
80
90
100
Secchi
Depth
(m)
64
32
16
8
4
2
1
0.5
0.25
0.12
0. 062
Surface
Phosphorus
(mg/m3 )
1
2
4
8
16
32
65
140
260
519
1032
Surface
Chlorophyll
(mg/m3 )
0.
0.
0.
0.
2.
6.
20
56
154
427
1183
04
12
34
94
6
4
Taken from Carlson (1974).
327
-------
trophic condition reported as a single number), objectivity,
absolute TSI values, valid relationships, retrieval of data from
the index (i.e., information is not lost, as in the US EPA and
Lueschow index systems) and can be intuitively grasped by the
layman in much the same manner as the Richter earthquake scale.
Piwoni and Lee Trophic Status Index System
A trophic index scale has been proposed by Piwoni and Lee
(1975). This index system was derived in a manner analogous
to that of Lueschow et al. (1970), except it contains modified
and additional parameters. The trophic state parameters are
summarized in Table 33. The total inorganic nitrogen parameters
were later dropped because the Wisconsin water bodies from which
the index system was derived, and on which it was first tested,
were not nitrogen-limited with respect to aquatic plan nutrient
requirements.
The sum of the rankings of the water bodies, after examina-
tion of the 10 trophic index parameters, was used to classify a
water body. The water body with the lowest overall ranking number
was judged the most oligotrophic of the water bodies being con-
sidered. Like the US EPA (I97<4d) and the Lueschow et_ al. (1970)
trophic index systems, the Piwoni and Lee (1975) system is a
relative trophic ranking system with the water body of the high-
est water quality receiving the lowest trophic index number.
The Piwoni and Lee system has a significant advantage over
the Lueschow et al. and US EPA systems in that it attempts to
eliminate from the classification those parameters (characteris-
tics) which may not properly characterize a water body's trophic
state. For example, for water bodies in which the chemical
nutrient determining overall algal biomass is phosphorus, (i.e.,
phosphorus-limited lakes) a classification system that utilizes
inorganic nitrogen concentrations would incorporate extraneous
information which would not be directly related to the overall
water quality of the water body as it relates to excessive
fertiliation.
One of the primary values of the multiparameter trophic
state index system is that for a given area of the country it is
possible to assess in quantitative to semi-quantitative terms the
relative water quality (trophic state) of various water bodies.
Lee (1974b) has utilized this approach to predict the relative
water quality of a proposed impoundment, compared to other lakes
and impoundments in south-central Wisconsin.
It should be noted that trophic state in a limnological sense
is not directly translatable to water quality. Highly fertile
water bodies in which the fertility is manifested in macrophyte
growth could have a relatively low trophic state index based on
the parameters normally used in the relative ranking schemes.
328
-------
Table 33. PIWONI AND LEE TROPHIC STATE
INDEX PARAMETERS
Parameters
Description
1. Secchi Depth
2. Chlorophyll a
3. DO Depletion
4. Winter Orthophosphate
5. Summer Orthophosphate
6. Winter Total Phosphorus
7. Summer Total Phosphorus
8. Winter Total Inorganic
Nitrogen
9. Summer Total Inorganic
Nitrogen
10 . Organic Nitrogen
Mean of all values obtained.
Average concentration in first 2
meters of water column during
study period.
Percent of lake volume with less
than 0.5 mg DO/1; May to October,
inclusive.
Average in-lake concentration dur-
ing winter under the ice.
Average epilimnion concentration;
May to October, inclusive.
Average in-lake concentrations dur-
ing winter under the ice.
Average epilimnion concentrations;
May to October, inclusive.
Average in-lake concentration dur-
ing winter under the ice.
Average epilimnion concentration;
May to October, inclusive.
Average concentration in first 2
meters of water column during
study period.
Taken from Piwoni and Lee (1975).
329
-------
Yet it could still have very poor water quality, if water quality
is assessed in terms of impairment of beneficial uses such as
swimming, boating, fishing, etc. As discussed in another section
of this report, great caution should be exercised in attempting
to translate the impairment in water quality associated with
a given level of chlorophyll or Secchi depth from one part of
the US to another. The response of the public to various degrees
of algal productivity is highly subjective and regional in
character (Lee, 1
Rast and Lee Trophic Status Index Systems
Several approaches have been used in this study to develop a
trophic index system based on the Vollenweider phosphorus loading
and mean depth/hydraulic residence time relationship (Figure 19).
One approach is based on the ratio of the current phosphorus load-
ing to the permissible phosphorus loading, the latter as defined
on the Vollenweider phosphorus loading diagram for a given mean
depth/hydraulic residence time value (Figure 19). This approach
was chosen because it reflects the amount of change in phosphorus
loading necessary to attain a permissible phosphorus load for a
water body with a given mean depth/hydraulic residence time rela-
tionship. Another approach was developed which relates the per-
missible and excessive phosphorus loads to several water quality
parameters, including chlorophyll a. and Secchi depth. These
approaches are discussed below.
The first trophic index classification approach developed in
this study is based on the position of the water bodies on the
Vollenweider phosphorus loading diagram (Figure 19). It is reason-
able to* suspect that a water body which plots a large vertical
distance above the permissible phosphorus loading line on Vollen-
weider 's diagram is relatively more eutrophic than a water body
which plots a smaller vertical distance above the permissible line,
However, it would be inappropriate to use the linear vertical dis-
tance of a water body above the permissible phosphorus loading
line because of the log-log scale of the Vollenweider diagram.
The simple linear vertical distance from the permissible phos-
phorus loading line would not take into account that water bodies
with high Z/T^ values, and hence in relatively higher phosphorus
loading positions on the Vollenweider diagram, would require a
greater total reduction in phosphorus loads to bring them down to
the permissible phosphorus loading level than would water bodies
with low Z/T values.
It should also be noted that since the permissible phosphorus
loading line defines a boundary condition, it may be more appro-
priate to use the perpendicular displacement (i.e., shortest
linear distance) of a water body from the line as a trophic rank-
ing parameter rather than the vertical distance, particularly for
water bodies with high Z/TW values. However, from the point of
330
-------
view of water quality management, the phosphorus loading (i.e.,
y-axis) is the only parameter among the Vollenweider criteria
which can be controlled or managed by man. Normally, man has
limited opportunity to control or manage the mean depth and
hydraulic residence time of a water body. Therefore, the dis-
placement of a water body along the y-axis (i.e., phosphorus
loading) of the Vollenweider phosphorus loading diagram (Figure
19) is the parameter of concern in the Rast and Lee trophic
status index.
This approach involves a determination of the magnitude of
change in water quality one could expect to occur for a given
change in phosphorus loading from the permissible loading level.
This approach assumes that the degree of eutrophy of a water
body is proportional to its phosphorus loading (i.e., phosphorus
limits algal growth in the water body). While this is true for
many water bodies, there are some water bodies in which phyto-
plankton growth is dependent on other factors such as nitrogen
load. Under these conditions, the above statements would not be
true over the complete range of phosphorus loads under condi-
tions where phosphorus loads control phytoplankton growth.
This trophic index system was developed by examining whether
a water body, with a certain phosphorus loading and chlorophyll a_
level, would experience a proportional change in water quality
for a given change in phosphorus load. This can be determined
by examining whether the magnitude of the phosphorus loading for
a water body above the permissible phosphorus loading is matched
by a proportional difference in chlorophyll a_ above a permissible
level. As indicated in a following section of this report, the
chlorophyll a concentration corresponding to the permissible
phosphorus loading line on the Vollenweider diagram (Figure 19)
is approximately 2 yg/1 (Vollenweider, 1975a; Dillon and Rigler,
1974a; Jones and Bachmann (1976). The ratio of the current
phosphorus loads to the permissible phosphorus load, as defined
on the Vollenweider phosphorus diagram (Figure 19) for a given
mean depth/hydraulic residence time value, was used in the trophic
index. Thus, a ratio greater than one represents the excessive
phosphorus loading above a certain critical phosphorus loading
level for the eutrophic US OECD water bodies. Conversely, a ratio
less than one represents a water body which is not receiving a
"permissible" phosphorus load, relative to its mean depth/
hydraulic residence time characteristics.
These ratios can be related to water quality parameters,
namely chlorophyll a, Secchi depth, and hypolimnetic oxygen
depletion, in order to provide trophic rankings for different
water bodies. The validity of this approach stems from the fact
that it has been shown in this investigation that the phosphorus
load to US OECD water bodies can be highly correlated with these
three parameters. These parameters are generally considered as
being highly indicative of planktonic algal growth and eutrophi-
cation-related water quality.
331
-------
The Rast and Lee trophic index system is similar in several
respects to that of Carlson. Emphasis is placed on utilization
of parameters of eutrophication (i.e. chlorophyll and Secchi
depth) to which the public can generally relate. This is espe-
cially true for water clarity (i.e. Secchi depth). An important
difference between the Carlson approach and this approach is
that Carlson develops his trophic state index system around
response parameters (i.e., chlorophyll, Secchi depth and total
phosphorus). These reviewers utilized an excess nutrient load-
ing parameter (i.e., phosphorus) as a means of classifying the
relative trophic status of water bodies.
It would be of interest to develop e relationship which
directly relates Vollenweider's (1975a) phosphorus loading and
mean depth/hydraulic residence time diagram (Figure 19) to
measurable water quality parameters, as was done with his phos-
phorus loading characteristics and chlorophyll a diagram (Figure
22). The development of such a model is discussed below.
This model or trophic index development centers around the
loading relationship (Equation 9) which serves as the basis for
the permissible phosphorus loading level in the Vollenweider
diagram (Figure 19). This equation is presented below in a
steady state form suitable for development of this approach:
L(P) = [P] z(p +a ) (49)
« « p 2
where L(P) = surface area total phosphorus loading (mg P/m /yr)
z = mean depth (m),
p = hydraulic flushing rate (yr~ ) = 1/T ,
T = hydraulic residence time (yr) = water body
w 3 . 3
volume (m )/annual inflow volume (m /yr),
o = sedimentation coefficient for phosphorus (yr~ ),
and [P] = steady state phosphorus concentration.
The same assumptions as noted for Vollenweider's model (Vollen-
weider, 1975a) apply to this approach. In derivation of the
permissible loading line in his loading diagram^ Vollenweider
(1975a; 1976a) chose Sawyer's (1947) spring overturn phosphorus
concentration (i.e., 10 yg/1) as the steady state phosphorus
concentration in the above equation. The permissible loading
line denotes the phosphorus loading, as a function of the mean
depth/hydraulic residence time characteristics of a water body,
which will produce a spring overturn phosphorus concentration of
10 ug/1 under steady state conditions.
332
-------
However, it is not mandatory that a steady state phosphorus
concentration of 10 yg/1 be used in Equation 49. Vollenweider
chose this value "for simplicity" as a meaningful reference point
around which to base boundary conditions. Other steady state
phosphorus concentrations may also be used in Equation 49 to
produce new phosphorus loading boundary conditions. The new
boundary condition will no longer be related to Sawyer's (1947)
spring overturn criteria for denoting oligotrophic versus eutrophic
conditions in water bodies. Instead, the new "permissible" load-
ing level will be the phosphorus loading which will produce the
new steady state phosphorus concentration which was inserted into
Equation 49 .
The basis for the modification of Equation 49 in this study
to relate the loading lines on the Vollenweider diagram to water
quality parameters is based on earlier work by Sakamoto (1966),
Dillon and Rigler (1974a) and Jones and Bachmann (1976). Dillon
and Rigler (1974a; 1975), elaborating on earlier work by Sakamoto,
investigated the hypothesis that a power relationship existed
between chlorophyll and phosphorus in many water bodies. They
correlated the summer mean chlorophyll a concentration (as a
measure of the algal biomass ) in a water body with its spring
overturn phosphorus concentration. Their data base (n=77) also
included that of Sakamoto (1966) plus a number of literature
values. The result was the regression equation:
log1Q [chlorophyll
= 1.45 log
1Q
(50)
r , n TIT -, summer , n , -, -,
where [chlorophyll aj, = summer mean chlorophyll a
~ 3 ~
concentration (mg/m ) , and
[P],
A
= spring overturn mean total
phosphorus concentration
• (mg/m ) .
The correlation coefficient was r=0.96, indicating a very strong
relationship between these two parameters. Jones and Bachmann
(1976) did a similar analysis on lakes in Iowa plus a larger num-
ber of literature values. Interestingly, Jones and Bachmann
regressed the summer mean chlorophyll concentration on the summer
mean total phospohrus , rather than the spring overturn total phos
phorus . However, they obtained an almost identical regression
equation and correlation coefficient :
log1Q [chlorophyll
= 1.46 Io
10
_ 1>Q9
r = 0.95
This indicates a water body's total phosphorus concentration
appears to remain relatively constant over the annual cycle .
Such an occurrence was demonstrated by Lee et al . (1976) in
studies on Lake Mendota.
333
-------
One may incorporate the work of Dillon and Rigler (1974a;
1975) and Jones and Bachmann (1976) into Vollenweider ' s equation
for the permissible and/or excessive phosphorus loading levels
to produce boundary conditions manifested in a water quality
parameter, namely phosphorus concentration. Equation 50 above
can be rearranged as :
Iog10 [P]SP = Iog10 [chlorophyll a]SUmmer + 1.14^ (52)
__^ »
Equation 49 can be arranged in the same manner as :
log [P]summer= log1Q [chlorophyll a]summer> + 1>09 (53)
10 A ~ j-^ - •
One can solve these equations for the phosphorus concentrations
which will produce a given summer chlorophyll a_ concentration.
A useful point about the above equations is that one can solve
them to obtain the relationship between as many total phosphorus
and chlorophyll a concentrations as desired. The result will be
a sequence of different total phosphorus and chlorophyll a data
sets . ~
The final step in the development of this approach is to use
either Equation 52 or 53, or the mean value of both equations,
and Equation 49 to translate Vollenweider ' s permissible and exces-
sive loading lines (Figure 19) into expected chlorophyll a_ con-
centrations. This can be done by the use of Equations 52~and/or
53 to determine the total phosphorus concentration required to produce
a given summer epilimnetic chlorophyll a_ concentration. The resultant
phosphorus concentration can be inserted into Equation 49, which
can then be solved for the particular phosphorus loading necessary
to produce the inserted phosphorus concentration. In addition,
the phosphorus concentration has also been related to a chlorophyll
a concentration (Equations 50 and/or 51). Thus, the solution of
Equation 49 for a given steady state phosphorus concentration also
directly relates the phosphorus loading to a given chlorophyll a_
concentration. One can then also relate these boundary lines to
Secchi depth and hypolimnetic oxygen depletion with the use of
Equations 38 and 41, respectively. With the use of these equations
Vollenweider ' s phosphorus loading diagram (Figure 19) can be
transformed so as to relate phosphorus loads to summer chlorophyll,
Secchi depth and hypolimnetic oxygen depletion conditions in a
water body. The permissible and excessive phosphorus loading
lines correspond, based on spring overturn phosphorus concentra-
tions of 10 yg/1 and 20 yg/1, respectively (Sawyer, 1947;
Sakamoto, 1966; Dillon and Rigler, 1975), to summer mean
epilimnetic chlorophyll a concentrations of 2 yg/1 and 6 yg/1,
to mean Secchi depths of 4.6 m? and 2.7 m and hypolimnetic oxygen
depletion rates of 0.3 mg 02/m^/day and 0 . 6 mg 0^/m2/day, re-
spectively. The results of the above approach are presented in
a following section.
334
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TROPHIC STATUS INDICES AS APPLIED TO THE US OECD WATER BODIES
US EPA Trophic Status Index System
The US EPA (1974d) Trophic State Index parameters were listed
in Table 31. Because the minimum dissolved oxygen concentration
was not available for most of the US OECD water bodies, this para-
meter (i.e., 15 minus the dissolved oxygen concentration) was not
included in the final ranking number. While this means that the
final ranking of the US OECD water bodies is based only on five
of the six US EPA Trophic State Index parameters, it should still
give a reasonably accurate relative trophic state ranking of the
US OECD water bodies. For the purpose of this discussion, the
US EPA approach is described as "modified" Commission of DO value)
from the classification scheme. In general, the data used in the
US EPA Trophic State Index, as well as that of Carlson, Piwoni
and Lee, and Rast and Lee, was taken from the US OECD Summary
Sheets (Appendix II) in this report. However, Rast and Lee also
made use of Vollenweider's phosphorus loading diagram (Figure 19).
The relative ranks of the US OECD water bodies based on the
five US EPA trophic state index parameters used in this classifi-
cation effort are presented in Table 34. In this system, the
water bodies with the lowest trophic status index number are
relatively the most productive, while the least productive lake in
the series will have the highest trophic status index number. The
US EPA (1974d) used the percent of the lakes in their study which
exceeded a parameter value for each lake to produce the relative
ranking for each lake for a given trophic state index parameter.
The same method was used by these reviewers, but the actual
number of lakes, rather than the percent exceeding a parameter
value for a particular lake, was used in the ranking. The relative
ranking position of the water bodies is identical in both cases.
Water bodies with identical parameter values (ties) were given the
same ranking number. It should be noted that all parameter values
were not available for all US OECD water bodies.
The trophic status rankings of the US OECD water bodies,
using the modified US EPA criteria, are presented in Table 35.
Since no trophic condition has been associated with a particular
Trophic Status Index Number(s), the trophic ranking is by necessity
only a relative ranking. In general, the relative trophic rank-
ing of the US OECD water bodies is as expected based on the
relative general characteristics of the water bodies. There are,
however, several anomalies in the ranking, based on the trophic
conditions reported by the US OECD investigators. Particularly,
Lakes Harriet, Washington-1957, Calhoun, and Shagawa appear to be
higher in the ranking (i.e., more toward the oligotrophic end of
the scale) than expected. Conversely, it would be said that Lakes
Cayuga and Weir are lower in the ranking than would be expected,
relative to the reported trophic conditions for the other water
bodies in the ranking. These apparent anomalies will be addressed
in more detail in a following section.
335
-------
Table 34. RANKING OF US OECD WATER BODIES USING
MODIFIED US EPA TROPHIC STATE INDEX SYSTEM
GO
co
Relative Ranking Under Indicated Parameter:
Total
Phosphorus
Water Body (mg/1)
Blackhawk (E)a
Brownie (E)
Calhoun (E)
Camelot-Sherwood (E)
Canadarago (E)
1968
1969
Cayuga (M)
1972
1973
Cedar (E)
Cox Hollow (E)
Dogfish (0)
1971
1972
Dutch Hollow (E)
George (0-M)
Harriet (E)
Isles (E)
Kerr Reservoir (E-M)
Roanoke Arm
Nutbush Arm
llb
_
8C
29b
26
28
36
36
24C
16b
44
44
3b
46
20C
7C
32
32
Inorganic
Nitrogen
(mg/l)e
6
39C'f
33°'f
4
18
15
20
12
39c'f
8
17
_
16
U0f
39°'f
39C'f
22
25
500-Secchi
Depth
( inches)
43
14
24
23
20
20
33
33
20
14
36
35
2
45
34
3
14
6
Dissolved
Chlorophyll a Phosphorus
(pg/1) (mg/1)
191
35C
34C
291
22
28
34
38
15°
81
34
39
41
_
40C
2C
20
12
11
25
34
27
19
19
38
36
34
10
-
_
20
40
34
25
23
19
Trophic Status
Index Number
(Sum of
Rankings)
90
_
133
112
105
110
161
155
132
56
-
_
45
_
167
76
111
94
-------
Table 34 (continued).
RANKING OF US OECD WATER BODIES USING
MODIFIED US EPA TROPHIC STATE INDEX SYSTEM
CO
CO
Relative Ranking Under Indicated Parameter:
Water Body
Lamb (0)
1971
1972
Meander (0)
1971
1972
Mendota (E)
Total
Phosphorus
(mg/1)
40
42
42
45
4
Inorganic
Nitrogen
(mg/l)e
12
-
13
-
7
500-Secchi
Depth
( inches )
20
27
40
39
39
Chlorophyll a
(Ug/l)
34
41
38
43
26
Dissolved
Phosphorus
(mg/1)
-
_
-
_
3
Trophic Status
Index Number
(Sum of
Rankings)
_
_
-
_
79
Michigan
Openwaters - 1971 (0) 39
Nearshore
Waters - 1971(M) 38
Lower Minnetonka
1969 (E) 23
1973 (E-"M) 26
Potomac Estuary (U-E)
Upper Reach 0°
Middle Reach ld
Lower Reach 27
Redstone (E) 17b
Sallie (E) 2
Sammarftish (M) 32
Shagawa (E) 23
Stewart (E) 23*
30
27
33
14
20
24U
34d
12
15
29®
31
0
16
41
33
43
38
13
25
18
21J
18
23d
42
41
38
27
1
29
14
36
187
I
31
107
93
119
90
-------
Table 34 (continued).
RANKING OF US OECD WATER BODIES USING
MODIFIED US EPA TROPHIC STATE INDEX SYSTEM
CO
CO
oo
Relative Ranking Under Indicated Parameter:
Water Body
Tahoe (U-0)
East Twin
1972 (E)
1973 (E)
1974 (E)
West Twin
1972 (E)
1973 (E)
1974 (E)
Twin Valley (E)
Virginia (E)
Waldo (U-0)
Washington
1957 (E)
1964 (E)
1971 (M)
1974 (M)
Weir (M)
Wingra (E)
Total
Phosphorus
(mg/1)
47
16
16
16
5
7
9
19b
llb
48h
33
18
37
-
16
36
Inorganic
Nitrogen
(mg/l)e
41
9
2
-
5
4
_
20
27
42h
32
24
29
-
35
21f
500-Secchi
Depth
(inches)
47
16
33
22
27
37
33
14
6
46h
27
6
42
44
22
7
Chlorophyll a
(ug/1)
45^
9
11
7
3
10
7
161
51
44h
25
15
34
-
27
^
Dissolved
Phosphorus
(mg/1)
34
10
7
19
5
5
7
22
22
34h
40
10
29
_
14
19
Trophic Status
Index Number
(Sum of
Rankings)
214
60
69
-
45
63
_
91
71
214
157
73
171
_
liu
—
-------
Table 34 (continued). RANKING OF US OECD WATER BODIES USING
MODIFIED US EPA TROPHIC STATE INDEX SYSTEM
Relative Ranking Under Indicated Parameter: Trophic Status
TotalInorganic500-SecchiDissolved Index Number
Phosphorus Nitrogen Depth Chlorophyll a Phosphorus (Sum of
Water Body (mg/1) (mg/l)e (inches) (wg/1) ~ (mg/1) Rankings)
EXPLANATION:
Investigator-indicated trophic condition
E = eutrophic
M = mesotrophic
0 = oligotrophic
U = ultra
Based on mean of summer and winter concentrations.
Q
Based on mean summer surface values.
Based on mean summer values.
oj e +
co Based on NH4+MO.+NO- (as N) unless otherwise indicated.
CD J *•
fBased on NH*+NO~ (as N) values.
gBased on N0~+N0~ (as N) values.
'Based on August values from 1970 to 1974.
Based on samples from upper two meters of water column.
JBased on euphotic zone measurements.
Dash (-) indicates data not available.
-------
Table 35. RELATIVE TROPHIC STATUS RANKING
OF US OECD WATER BODIES USING MODIFIED
US EPA TROPHIC STATUS INDEX SYSTEM.
Water Body
Investigator-Indicated
Trophic Status
Trophic Status
Index Number
tie
tie
TTahoe
|^ Waldo
Michigan
Open Waters - 1971
Washington - 1971
Harriet
Cayuga - 1972
Washington - 1957
Cayuga - 1973
Calhoun
Shagawa
Weir
Camelot - Sherwood
Kerr - Roanoke Arm
Canadarago - 1969
Potomac - Lower
Reach
Canadarago - 1968
Kerr - Nutbush Arm
Redstone
Twin Valley
JBlackhawk
\.Stewart
Mendota
Isles
Washington - 1964
Virginia
East Twin - 1973
West twin - 1973
ultra - oligotrophic
ultra - oligotrophic
oligotrophic
mesotrophic
eutrophic
mesotrophic
eutrophic
mesotrophic
eutrophic
eutrophic
mesotrophic
eutrophic
eutrophic - mesotrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
- mesotrophic
214
214
187
171
167
161
157
155
133
119
114
112
111
110
107
105
94
93
91
90
90
79
76
73
71
69
63
340
-------
Table 35 (continued)
RELATIVE TROPHIC STATUS RANKING
OF US OECD WATER BODIES USING MODIFIED
US EPA TROPHIC STATUS INDEX SYSTEM
Water Body
Investigator-Indicated
Trophic Status
Trophic Status
Index Number
tie
East Twin - 1972
Cox Hollow
: Dutch Hollow
West Twin - 1972
Potomac - Middle
Reach
Potomac - Upper
Reach
eutrophic
eutrophic
eutrophic
eutrophic
ultra-eutrophic
ultra-eutrophic
60
45
45
45
31
1
341
-------
Carlson Trophic Status Index System
The parameters in Carlson's (1974) Trophic Status Index
were listed in Table 32. An absolute TSI value can be assigned
to a water body on the basis of either its phosphorus or chloro-
phyll concentration and/or its Secchi depth. However, the
trophic rankings are still relative, as with the US EPA Trophic
Status Index System, since no TSI value or range was assigned to
a given trophic condition in Carlson's system. If it were neces-
sary to assign a TSI value to a given trophic condition, general
limnological knowledge would suggest that a reasonable boundary
value between eutrophic and oligotrophic might be a TSI value of
40. This TSI value would indicate a Secchi depth of 4 meters, a
chlorophyll concentration of 2.6 ug/1 and a phosphorus concen-
tration of about 16 ug/1. This value as a boundary condition is
based solely on the experience of these reviewers.
The relative rankings of the US OECD water bodies, based on
their phosphorus and chlorophyll concentrations, and Secchi depths,
are presented in Table 36. Inspection of Table 36 indicates that
the relative positions of the US OECD water bodies vary widely,
depending on the particular Carlson TSI parameter examined.
In order to demonstrate the relationship between the three
Carlson TSI parameters, the US OECD water bodies were ranked by
these parameters on the basis of increasing productivity or
eutrophy. In this ranking the order of water bodies is from the
oligotrophic end of the trophic scale to the eutrophic end, with
the relatively most eutrophic water body listed first. The re-
sults are presented in Table 37 (the investigator-indicated
trophic states were indicated in Table 36).
A general inspection of Table 37 shows that while the ultra-
oligotrophic and ultra-eutrophic water bodies are listed at the
appropriate ends of the ranking scales, there are a number of
differences in the relative positions of US OECD water bodies
using the three different Carlson TSI parameters. For example,
the reported Secchi depths for Lakes Blackhawk, Mendota, and
Harriet place them higher (i.e., toward the oligotrophic end of
the scale) in the relative ranking than several other water bodies
generally considered less productive (i.e., Washington - 1971,
Dogfish and Cayuga, respectively). The chlorophyll concentrations
for Lakes Harriet, Brownie and Calhoun also place them higher in
the relative ranking than less productive Lakes Cayuga, Dogfish
and Lamb.
Carlson (1974), using data for Lake Washington, has demon-
strated that the data for this lake and TSI values follow the same
trends and that they produce the same relative values when trans-
formed to the trophic scale. He has also indicated that the TSI
values (and relative rankings) are not always identical. Such an
anomaly can be used as an internal check on the assumptions being
342
-------
Table 36. RANKING OF US OECD WATER BODIES USING
CARLSON TROPHIC STATUS INDEX SYSTEM
Water Body ''
Blackhawk (E)a
Brownie (E)
Calhoun (E)
Came lot -Sherwood (E)
Canadarago (E)
1968
1969
Cayuga (M)
1972
1973
Cedar (E)
Cox Hollow (E)
Dogfish (0)
1971
1972
Dutch Hollow (E)
George (0-M)
Harriet (E)
Isles (E)
Kerr Reservoir (E-M)
Roanoke Arm
Nutbush Arm
Lamb ( 0 )
1971
1972
Meander (0)
1971
1972
Mendota (E)
Relative Ranking Under Indicated Parameter:
rSI(SD)
5
33
24
25
.
28
15
15
28
33
12
13
45
3
14
44
33
41
28
21
8
9
9
TSI(TP)
35b
—
37°
19b
22
20
13
13
24C
31b
5
5
43b
3
28°
38
16
16
9
7
7
4
42
TSH Chlorophyll)
26f
12
13°
18f
25
19
13
8
29C
37f
13
7
41f
6C
43C
26
33
13
5
8
3
21
343
-------
Table 36(continued). RANKING OF US OECD WATER
BODIES USING CARLSON TROPHIC INDEX SYSTEM
Relative Ranking Under Indicated Parameter:
Water Body
Michigan (0-M)
Nearshore Waters -
1971
Open Waters -
1971
Lower Minnetonka
1969 (E)
1973 (E+M)
Potomac Estuary (U-E)
Upper Reach
Middle Reach
Lower Reach
Redstone (E)
Sallie (E)
Sammamish (M)
Shagawa (E)
Stewart (E)
Tahoe (U-0)
East Twin
1972 (E)
1973 (E)
1974 (E)
West Twin
1972 (E)
1973 (E)
1974 (E)
Twin Valley (E)
Virginia (E)
Waldo (U-0)
TSI(SD)
15
__
33
28
47d
45d
33d
31
-
7
15
33
1
31
15
26
21
11
15
33
41
26
TSKTP)
11
9
25
22
46d
45d
21d
30b
44
16
25
25b
1
31
31
31
41
38
38
29b
35b
2e
TSKChlorophyll)
8
3
32
22
45d
44d
2yd
25f
-
8
27
24f
is
36
34
38
42
35
38
29f
40f
2e »g
344
-------
Table 36(continued). RANKING OF US OECD WATER
BODIES USING CARLSON TROPHIC INDEX SYSTEM
Relative Ranking Under Indicated Parameter:
Water Body
Washington
1957 (E)
1964 (E)
1971 (M)
1974 (M)
Weir (M)
Wingra (E)
TSI(SD)
21
41
6
4
26
40
TSI(TP)
15
29
12
-
31
13
TS I (Chlorophyll)
22
29
13
-
20
—
EXPLANATION:
Investigator-indicated trophic status:
E = eutrophic
M = mesotrophic
0 = oligotrophic
U = ultra
Based on mean of summer and winter concentrations.
°Based on mean summer surface values.
Based on mean summer values.
6Based on August values from 1970 to 1974.
Based on samples from upper two meters of water column.
Q~
&Based on euphotic zone measurements.
Dash (-) indicates data not available.
345
-------
Table 37. RELATIVE TROPHIC STATUS RANKING OF US
OECD WATER BODIES USING CARLSON TROPHIC
STATUS INDEX SYSTEM
TSI(SD)
TSI(TP)
TSI(Chlorophyll)
Tahoe
Waldo
George
Washington-1974
Blackhawk
Washington-1971
Sammamish
Meander-1971
fMeander-1972
\Mendota
West Twin-1973
Dogfish-1971
Dogfish-1972
Harriet
^tayuga-1972
Cayuga-1973
Michigan
tie\
tie
tie< .
tie
Open Waters - 1971
Tahoe
Waldo
George
Meander-1972
Dogfish-1971
Dogfish-1972
•^
fLamb-1972
Meander-1972
Lamb-1971
Michigan , . ,
Open Waters-1971 \
Michigan , Nearshore
Waters-1971
Washington-1971
fCayuga-1972
^Cayuga-1973
Washington-1957
/rCerr-Roanoke Arm
Tahoe
Waldo
(Meander-1972
Shagawa
East Twin-1973
West Twin-1974
v
fLamb-1972
tie(West Twin-1972
lwashington-1957
Calhoun
Camelot-Sherwood
(East Twin-1974
tie(Kerr-Nutbush Arm
vSammamish
Camelot-Sherwood
Canadarago-1969
Potomac-Lower
Reach
rCanadarago-1968
tieS
I Lower Minnetonka-
1973
Cedar
tie/.,. , .
NMichigan
L Open Waters-1971
Lamb-1972
Harriet
Dogfish-1972
*•
Cayuga-1973
Meander-1971
Michigan, Nearshore
Waters-1971
Sammamish
W
Brownie
(Calhoun
Cayuga-1972
tie{Dogfish-1971
Lamb-1971
Washington-1971
Camelot-Sherwood
Canadarago-1969
Weir
Mendota
/Lower Minnetonka-
tie/ 1973
(Washington-1957
Stewart
Canadarago-1968
346
-------
Table 37(continued) RELATIVE TROPHIC STATUS RANKING
OF THE US OECD WATER BODIES USING CARLSON
TROPHIC STATUS INDEX SYSTEM
TSI(SD)
TSI(TP)
TSK Chlorophyll)
(Canadarago-1969
I Cedar
tie^Lamb-1971
[Lower Minnetonka-
v> 1973
(Redstone
East Twin-1972
Brownie
(Cox Hollow
jKerr-Roanoke Arm
Lower Minnetonka-
1969
Potomac-Lower
Reach
JWin Valley
Stewart
Wingra
/Kerr-Nutbush Arm
tie< Virginia
lwashington-1964
Isles
/Dutch Hollow
tle\Potomac-Middle
L. Reach
Potomac-Upper
Reach
[Lower Minnetonka-
1969
tiesShagawa
(Stewart
Harriet
Twin Valley
[c.
IE,
tie £
IE,
Redstone
S
Cox Hollow
East Twin-1972
East Twin-1973
East Twin-1974
(^Blackhawk
tie
-------
made about a water body's utilization of phosphorus for planktonic
algal growth. To cite an example (Carlson, 1974), if a water body
has a higher TSI(TP) than its TSI(SD) and TSI (Chlorophyll), and
the latter two values are similar, then it may indicate that the
water body is not phosphorus-limited.
Piwoni and Lee Trophic Status Index System
The Trophic State Index parameters of Piwoni and Lee were
presented in Table 33. As with the US EPA (1974d) Trophic State
Index System, all parameter values were not available for all US
OECD water bodies. As before, if a water body did not have values
for all the Piwoni and Lee Trophic State Index parameters, it was
not included in the final ranking. Further, the parameters used
by these reviewers in ranking the US OECD water bodies using the
Piwoni and Lee system were altered so that available data could be
used. Phosphorus and nitrogen values were not reported on a
seasonal basis in most cases. Also, the DO depletion was unavail-
able for most US OECD water bodies. The result was that the
Secchi depths, total and dissolved phosphorus, and inorganic
nitrogen concentration, and chlorophyll a concentration of the
US OECD water bodies were used to rank them in the Piwoni and Lee
Trophic Status Index System. The rankings of the US OECD water
bodies using the modified Piwoni and Lee parameters, are presented
in Table 38.
The relative ranks of the US OECD water bodies, based on the
five modified Piwoni and Lee Trophic State Index parameters, are
presented in Table 39. In this table, the more oligotrophic water
bodies are listed first. As with the other relative trophic rank-
ings , there is general agreement between the US OECD water body's
relative trophic rankings and the trophic conditions indicated by
their respective investigators. Lake Harriet occupies a higher
relative ranking than less productive Lakes Washington - 1974 and
Cayuga, while Lake Weir occupies a. lower relative ranking than
more productive Lakes Cedar, Shagawa and Calhoun. Lake Shagawa,
based on limnological characteristics, also occupies a higher
ranking than less productive water bodies.
Rast and Lee Trophic Status Index System
Eor this discussion, these authors chose several of the same
trophic state indicators used in Carlson's (1974) Trophic Status
Index System; namely Secchi depth and chlorophyll a. The ranking
of the US OECD water bodies, based on their current phosphorus
loading/permissible phosphorus loading and current chlorophyll/per-
missible chlorophyll quotients, Secchi depth and chlorophyll a
concentrations as ranking parameters, is presented in Table 40.
The relative rankings of the US OECD water bodies , based on the
above-mentioned parameters, are listed in Table 41.
348
-------
Table 38 . RANKING OF US OECD WATER BODIES USING
PIWONI AND LEE MODIFIED TROPHIC STATUS
INDEX SYSTEM
co
-tr
Relative Ranking Under Indicated Parameter: Trophic Status
Total
Phosphorus
Water Body (mg/1)
Blackhawk (E)a
Brownie (E)
Calhoun (E)
Camelot-Sherwood (E)
Canadarago (E)
1968
1969
Cayuga (M)
1972
1973
Cedar (E)
Cox Hollow (E)
Dogfish (0)
1971
1972
Dutch Hollow (E)
George (0-M)
Harriet (E)
Isles (E)
Kerr Reservoir (E-M)
Roanoke Arm
Nutbush Arm
39g
_
426
20g
23
21
13
13
25e
336
5
5
47g
3
29e
43e
17
17
Inorganic
Nitrogen
(mg/1) h
36g
4e,i
II6'1
38g
25
28
23
31
4e,i
34g
26
_
27g
31
4e,i
^,i
21
18
Secchi
Depth
(m)
5
34
24
25
28
-
15
15
28
34
12
13
46
3
14
45
34
42
Dissolved
Chlorophyll a Phosphorus
(yg/1) ~ (mg/1)
27d
lle
12e
17d
24
18
12
8
316
38d
12
7
42d
_
66
44fi
26
34
32g
18S
9e
16g
24
24
5
7
9e
33g
-
_
23g
3
9e
18S
20
24
Index Number
(Sum of
Rankings)
139
-
98
116
124
-
68
74
97
172
-
-
185
-
62
154
118
135
-------
Table 38(continued). RANKING OF US OECD WATER BODIES USING
PIWONI AND LEE MODIFIED TROPHIC STATUS INDEX SYSTEM
OJ
en
O
Relative Ranking Under Indicated Parameter: Trophic Status
Total Inorganic Secchi
Phosphorus Nitrogen Depth
Water Body (mg/1) (mg/1) h (m)
Lamb ( 0 )
1971
1972
Meander (0)
1971
1972
Mendota (E)
Michigan
Nearshore Waters (M)
-1971
Open Waters (0)
-1971
Lower Minnetonka
1969 (E)
1973 (E-M)
9 31 28
7 - 21
7 30 8
4-9
46 35 9
11 16
10 13 15
26 - 34
23 - 28
Chlorophyll a
(Mg/D ~
12
5
8
3
20
8
3
33
21
Dissolved Index Number
Phosphorus (Sum of
(mg/1) Rankings)
-
-
-
-
46 156
2
1 42
_
5
Potomac Estuary (U-E) ^
Upper Reach 50
Middle Reach 49
Lower Reach 22
Redstone (E) 32g
Sallie (E) 48
Sanunamish (M) 17
Shagawa (E) 26
Stewart (E) 26g
42
19
10
28
13
m«
48
46l
341
32
7
15
40
461
451
281
25C
28
23C
43
40
30
42
14
29
229
199
124
137
60
111
137
-------
Table 38(continued). RANKING OF US OECD WATER BODIES USING
PIWONI AND LEE MODIFIED TROPHIC STATUS INDEX SYSTEM
CO
en
Relative Ranking Under Indicated Parameter: Trophic Status
Water Body
Tahoe (U-0)
East Twin
1972 (E)
1973 (E)
1974 (E)
West Twin
1972 (E)
1973 (E)
1974 (E)
Twin Valley (E)
Virginia (E)
Waldo (U-0)
Washington
1957 (E)
1964 (E)
1971 (M)
1974 (M)
EXPLANATION:
a_ . . ...
Total
Phosphorus
(mg/1)
1
33
33
33
45
43
41
3QS
39^
2C
16
31
12
13
Inorganic
Nitrogen
(mg/l)h
2
33
40
-
37
38
_
23g
16^
lc
12
19
14
221
Secchi
Depth
(m)
1
32
15
26
21
11
15
34
42
2c
21
42
6
41
Chlorophyll a
(pg/1)
1
37
35
39
43
36
39
30d
41d
2c,f
21
31
12
-
Dissolved
Phosphorus
(mg/1)
9
33
36
24
38
38
36
216
218
9C
3
33
14
24
Index Number
(Sum of
Rankings)
14
168
159
-
184
166
-
138
159
16
73
156
58
-
Investigator-indicated trophic status
E = eutrophic
M = mesotrophic
0 = oligotrophic
U = ultra
-------
Table 38(continued). RANKING OF US OECD WATER BODIES USING
PIWONI AND LEE MODIFIED TROPHIC STATUS INDEX SYSTEM
Relative Ranking Under Indicated Parameter: Trophic Statin
Total InorganicSecchiDissolvedIndex Number
Phosphorus Nitrogen Depth Chlorophyll a Phosphorus (Sum of
Water Body (mg/1) (mg/1) (m) (ug/D (nig/1) Rankings)
Based on mean summer values.
GBased on August values from 1970 to 1974.
Based on samples taken from upper two meters of water column.
eBased on mean summer surface values.
Based on eutrophic zone measurements.
^Based on mean of summer and winter concentrations.
Based on NH. +N07+NO" (as N) unless otherwise indicated.
" o L.
1Based on NH^+NO~ (as N) values.
. 4 J
^Based on N0~+N0~ (as N) values.
-------
Table 39 .
RELATIVE TROPHIC STATUS RANKINGS
OF US OECD WATER BODIES USING
PIWONI AND LEE MODIFIED TROPHIC
STATUS INDEX SYSTEM
Water Body
Investigator-Indicated
Trophic Status
Trophic Status
Index Number
tie
tie
Tahoe
Waldo
Michigan
Open Waters - 1971
Washington - 1971
Sammamish
Harriet
Cayuga - 1972
Cayuga - 1973
Washington - 1974
Cedar
Calhoun
Shagawa
Camelot-Sherwood
Weir
Kerr-Roanoke Arm
rCanadarago - 1968
(^Potomac - Lower Reach
Kerr - Nutbush Arm
fRedstone
(_ Stewart
Twin Valley
Virginia
Mendota
Isles
Washington - 1964
East Twin - 1973
West Twin - 1973
ultra-oligotrophic
ultra-oligotrophic
oligotrophic
mesotrophic
mesotrophic
eutrophic
mesotrophic
mesotrophic
mesotrophic
eutrophic
eutrophic
eutrophic
eutrophic
mesotrophic
eutrophic-mesotrophic
eutrophic
eutrophic
eutrophic-mesotrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
eutrophic
14
16
42
58
60
62
68
74
82
97
98
111
116
117
118
124
124
135
137
137
138
144
150
154
156
159
166
353
-------
Table 39 (Continued). RELATIVE TROPHIC STATUS RANKINGS
OF US OECD WATER BODIES USING PIWONI AND LEE
MODIFIED TROPHIC STATUS INDEX SYSTEM
Investigator-Indicated Trophic Status
Water Body Trophic Status Index Number
East Twin - 1972 eutrophic 168
West Twin - 1972 eutrophic 184
Dutch Hollow eutrophic 185
Potomac - Middle
Reach ultra-eutrophic 199
Potomac - Upper
Reach ultra-eutrophic 229
354
-------
Table 40. RANKING OF US OECD WATER BODIES
USING SECCHI DEPTH, CHLOROPHYLL a, EXCESS
CHLOROPHYLL AND EXCESS PHOSPHORUS LOADING AS
RANKING PARAMETERS
Relative Ranking Under Indicated Parameters
Water Body
Blackhawk (E)a
Brownie (E)
Calhoun (E)
Camelot -Sherwood (E)
Canadarago (E)
1968
1969
Cayuga (M)
1972
1973
Cedar (E)
Cox Hollow (E)
Dogfish (0)
1971
1972
Dutch Hollow (E)
George (0-M)
Harriet (E)
Isles (E)
Kerr Reservoir (E-M)
Roanoke Arm
Nutbush Arm
Lamb ( 0 )
1971
1972
Mean
Secchi
Depth
(m)
5
33
24
25
-
28
15
15
28
33
12
13
45
3
14
44
33
41
28
21
Mean
Chloro-
phyll a
(yg/D~
26C
12d
13d
18C
25
19
13
8
29d
37°
13
7
41°
_
6d
43d
26
33
13
5
(Current
Chloro-
phyll a ) /
(Permis-
sible
Chloro-
phyll a )
27
14
15
18
19
22
20
13
31
38
7
4
42
_
7
44
26
29
11
7
(Current
Phosphorus
Loading ) /
(Permissible
Phosphorus
Loading )
41
36
32
33
-
20
26
_
17
42
-
2
34
6
28
44
35
30
-
3
355
-------
Table 40 (continued). RANKING OF US OECD WATER BODIES
USING SECCHI DEPTH, CHLOROPHYLL a, EXCESS
CHLOROPHYLL AND EXCESS PHOSPHORUS LOADING AS
RANKING PARAMETERS
Relative Ranking Under Indicated Parameters
Water Body
Meander (0)
1971
1972
Mendota (E)
Michigan (0)
-open waters
(T =30 yrs)
1971
1974
Michigan (0)
-open waters
(T = 100 yrs)
1971
1974
Lower Minnetonka
1969 (E)
1973 (E+M)
Potomac Estuary (U-E)
Upper Reach
Middle Reach
Lower Reach
Redstone (E)
Sallie (E)
Sammamish (M)
Shagawa (E)
Mean
Secchi
Depth
(m)
8
9
9
-
-
-
-
33
28
47b
45b
33b
31
-
7
15
Mean
Chloro-
phyll a
(yg/l)~
8
3
21
3
-
3
-
32
22
45b
44b
27b
25C
-
8
27
(Current
Chloro-
phyll a)/
(Permis-
sible
Chloro-
phyll a)
7
3
31
5
-
5
-
33
21
46
45
28
25
12
35
(Current
Phosphorus
Loading)/
(Permissible
Phosphorus
Loading )
-
3
37
11
8
12
9
25
10
48
47
31
40
46
20
23
356
-------
Table 40 (continued). RANKING OF US OECD WATER BODIES
USING SECCHI DEPTH, CHLOROPHYLL a, EXCESS
CHLOROPHYLL AND EXCESS PHOSPHORUS LOADING AS
RANKING PARAMETERS
Water Body
Stewart (E)
Tahoe (U-0)
East Twin
1972 (E)
1973 (E)
1974 (E)
West Twin
1972 (E)
1973 (E)
1974 (E)
Twin Valley (E)
Virginia (E)
Waldo (U-0)
Washington
1957 (E)
1964 (E)
1971 (M)
1974 (M)
Weir (M)
Wingra (E)
Explanation :
Investigator -indicated
E = eutrophic
M - mesotrophic
0 = oligotrophic
U = ultra
Relative
Mean
Secchi
Depth
(m)
33
1
31
15
26
21
11
15
33
41
2e
21
41
6
4
26
40
trophic
Ranking Under Indicated Parameters
Mean
Chloro-
phyll a
(yg/l)~~
24°
lf
36
34
38
42
35
38
29C
40C
2e,f
22
29
13
-
20
-
state :
(Current
Chloro-
phyll a)/
(Permis-
sible
Chloro-
phyll a)
24
1
37
34
39
43
36
39
30
41
1
23
31
16
-
17
-
(Current
Phosphorus
Loading ) /
(Permissible
Phosphorus
Loading )
45
5
24
19
20
18
16
15
39
43
1
27
38
13
14
6
29
357
-------
Table 40 (continued). RANKING OF US OECD WATER BODIES
USING SECCHI DEPTH, CHLOROPHYLL a, EXCESS
CHLOROPHYLL AND EXCESS PHOSPHORUS LOADING AS
RANKING PARAMETERS
EXPLANATION (continued)
Based on mean summer values.
Based on samples taken from upper two meters of water column
Based on summer surface values.
6Based on August values from 1970 to 1974.
Based on euphotic zone measurements.
^Based on mean of summer and winter concentrations.
Dash (-) indicates data not available.
358
-------
Table 41 . RELATIVE TROPHIC STATUS RANKING OF US OECD WATER
BODIES USING SECCHI DEPTH, CHLOROPHYLL a, EXCESS
CHLOROPHYLL a AND EXCESS PHOSPHORUS LOAD
GO
en
CD
Mean Secchi
Depth
(m)
Tahoe
Waldo
George
Washington -
197"+
Blackhawk
Washington -
1971
Sammamish
Meander1 —
1971
Meander -
1972
Mendota
West Twin -
1973
Dogfish -
1971
Dogfish -
1972
Harriet
Mean Chlorophyll
(yg/D
Tahoe
Waldo
Meander - 1972
Michigan -
Open Waters -
1971
Lamb - 1972
Harriet
Dogfish - 1972
Cayuga - 1973
Meander - 1971
Michigan
Nearshore
Waters - 1971
Brownie
Calhoun
Cayuga - 1972
Dogfish - 1971
Lamb - 1971
Washington -
1971
(Current Chlorophyll a)/
(Permissible Chlorophyll
Tahoe
Waldo
Meander - 1972
Dogfish - 1972
Michigan
Open Waters - 1971
(T = 30 S 100 yrs)
10
rjclir*!1 J- &L
Lamb - 1972
Meander - 1971
Dogfish - 1971
Lamb - 1971
Dogfish - 1971
Sammamish
Cayuga - 1973
Brownie
Calhoun
Washington - 1971
Weir
Camelot -Sherwood
(Current Phosphorus Load)/
a) (Permissible Phosphorus Load)
Waldo
Dogfish - 1972
Lamb - 1972
Meander - 1972
Tahoe
George
Weir
Michigan
Open Waters -
(T^ = 30 yrs)
Michigan
Open Waters -
(T = 100 yrs)
CO
1974
1974
Minnetonka - 1973
Michigan
Open Waters -
(T = 30 yrs)
Michigan
Open Waters -
(T = 100 yrs)
1971
1971
Washington - 1971
-------
Table 41 (continued).
RELATIVE TROPHIC STATUS RANKING OF US OECD WATER
BODIES USING SECCHI DEPTH, CHLOROPHYLL a, EXCESS
CHLOROPHYLL a AND EXCESS PHOSPHORUS LOAD
CO
CD
O
Mean Secchi
Depth
(m)
Cayuga - 1972
Cayuga - 1973
Michigan
Open Waters -
1971
Shagawa
East Twin -
1973
West Twin -
1974
Lamb - 1972
West Twin -
1972
Washington -
1957
Calhoun
Camelot-
Sherwood
East Twin -
1974
Weir
Canadarago -
1969
Mean Chlorophyll
(yg/i)
Came lot -Sherwood
Canadarago - 1969
Weir
Mendota
Lower Minnetonka
1973
Washington -
1957
Stewart
Canadarago - 1968
Redstone
Kerr-Roanoke Arm
Blackhawk
Potomac -Lower
Reach
Shagawa
Twin Valley
Cedar
Washington-1964
Lower Minnetonka
1969
Kerr-Roanoke Arm
(Current Chlorophyll a)/
(Permissible Chlorophyll a)
Canadarago - 1968
Cayuga - 1972
Minnetonka - 1973
Canadarago - 1969
Washington - 1957
Stewart
Redstone
Kerr Reservoir
-Roanoke Arm
Blackhawk
Kerr Reservoir
-Nutbush Arm
Potomac Estuary
-Lower Reach
Kerr Reservoir
-Nutbush Arm
Twin Valley
Cedar
Mendota
Minnetonka - 1969
East Twin - 1973
Shagawa
(Current Phosphorus Load)/
(Permissible Phosphorus Load)
Washington - 1974
West Twin - 1974
West Twin - 1973
Cedar
West Twin - 1972
East Twin - 1973
Canadarago
Sammamish
East Twin - 1974
Shagawa
East Twin - 1972
Minnetonka - 1969
Cayuga
Washington - 1957
Harriet
Wingra
Kerr Reservoir -
Nutbush Arm
Potomac Estuary -
Lower Reach
Calhoun
-------
Table 41 (continued).
RELATIVE TROPHIC STATUS RANKING OF US OECD WATER
BODIES USING SECCHI DEPTH, CHLOROPHYLL a, EXCESS
CHLOROPHYLL a AND EXCESS PHOSPHORUS LOAD
CO
CD
Mean Secchi
Depth
(m)
Cedar
Lamb - 1971
Lower Minne-
tonka - 1973
Redstone
Mean Chlorophyll
a (Current Chlorophyll a)/
(yg/1) (Permissible Chlorophyll
East Twin - 1973 West Twin - 1973
East Twin - 1972
Cox Hollow
East Twin - 1974
West Twin - 1974
Virginia
Dutch Hollow
West Twin - 1972
Isles
Potomac Estuary -
Middle Reach
Potomac Estuary -
Upper Reach
(Current Phosphorus Load)/
a) (Permissible Phosphorus Load)
Came lot -Sherwood
Dutch Hollow
Kerr Reservoir -
Roanoke Arm
Brownie
Mendota
Washington - 1964
Twin Valley
Redstone
Blackhawk
Cox Hollow
Virginia
Isles
Stewart
Sallie
Potomac Estuary -
Middle Reach
Potomac Estuary -
Upper Reach
-------
A plot of the ratio of the current phosphorus loading/per-
missible phosphorus loading and the mean chlorophyll a concentra-
tions for the US OECD water bodies is presented in Figure 86.
This correlation was developed to relate the excess phosphorus
loading of a water body (as related to its permissible phosphorus
loading) to water quality parameters. Lines corresponding to
Vollenweider's permissible and excessive loadings (Figure 19) can
be inserted in Figure 86. The permissible line corresponds to a
current phosphorus load/permissible phosphorus load quotient of
one (i.e., the current and permissible phosphorus loads are
identical) while a quotient of two (i.e., the current phosphorus
load is twice the permissible phosphorus load) denotes the
excessive loading level on the Vollenweider diagram. Figure 86
indicates a reasonably good agreement between the investigator-
indicated trophic conditions and the predicted trophic conditions
based on this relationship. There are apparent anomalies and
data scatter which may be due to possible errors in the estimates
of either the phosphorus load or mean chlorophyll a_ values, as
well as a number of other factors. For example, the possibility
of underestimations of the phosphorus loads for Lakes Dogfish,
Lamb and Meander was addressed earlier. The situation with respect
to the lag time between a phosphorus loading reduction and a new
steady state chlorophyll a concentration for Lakes Washington and
Minnetonka have also been addressed. Lake Weir, possibly because
of its subtropical nature relative to the northern US temperate
conditions of the other US OECD water bodies, also exhibits an
anomalous fit.
In general, however, there is a relationship between the current
phosphorus load/permissible phosphorus load quotients and the
resultant summer chlorophyll a concentrations for the US OECD
water bodies. The agreement lends support to the use of this
approach for assessing the trophic conditions of water bodies,
based on their excess phosphorus ^loadings above a permissible
level, and the resultant chlorophyll a concentrations in the
water bodies.
A plot was also made of the ratio of the current phosphorus
load to the permissible phosphorus load and the ratio of the
current chlorophyll a concentration to the permissible chlorophyll
a. concentration (Figure 87). As indicated earlier, the permissible
chlorophyll a concentration (i.e., 2 yg/D was the summer mean
concentration corresponding to Vollenweider's permissible phos-
phorus loading line (Figure 19). One can view this graph as a
correlation between the "excess" phosphorus loading, as expressed
in the current load/permissible load quotient, and the "excess"
summer chlorophyll a concentration, as expressed in the current
chlorophyll a concentration/summer permissible chlorophyll a con-
centration (i.e., 2 yg/1) quotient. There is a reasonably good
agreement between these two parameters. If the water bodies
which have been accepted as anomalous on the basis of various
previous analyses (i.e., Lakes Weir, Dogfish, Lamb, Meander,
Minnetonka - 1973, Twin Lakes, etc.) are removed, there is a
362
-------
100
O»
-I
-I
>
X
CL
O
cn
o
x
o
<
QJ
10
0.1
- 1 1 29 •
14 0
43
9 II
" JJ 4' 33 • £t
7* " 30 ^**
9« ^^^ ^^ ^^^^^ ^k,
^ 98^*49 »*• •
^^ ^^ 9*
~ 93
! 9 ia si
10—. _2O
O o
O O
21 23-B
Perm
:s 5
'
I 1 I I 1 1 i 1
^•i
*..
ssible
Exce«
68
| -I t*»'
• '3
Investigator- Indicated
Trophic State:
>sive
• - Eutrophic
A - Mesotrophic
O - Oligotrophic
I t 1 1 ! 1 I 1 111 ! I 1 ' i !
O.I
10
100
CURRENT PHOSPHORUS LOADING
PERMISSIBLE PHOSPHORUS LOADING
Figure 86. Relationship Between Excessive Phosphorus
Loads and Chlorophyll a^ in US OECD Water
Bodies
363
-------
lOOp
01
ol
-J
_l
>-
X
CL
O
or
o
_i
X
o
Id
2E
_J
>-
X
Q.
O
or
o
_j
X
0
LJ
_J
CD
i
a:
UJ
CL
o
0.1
29
26
26
49
35
9 IB
O O
O20
- IOO
21
Investigator-Indicated
Trophic State:
Eutrophic
Mesotrophic
Oiigotrophic
1 1 1 1 I l
I t j 1 ! I i
O.I
10
100
CURRENT PHOSPHORUS LOADING
PERMISSIBLE PHOSPHORUS LOADING
Figure 87.
Relationship Between Excessive
Phosphorus Loads and Excessive
Chlorophyll a_ in US OECD Hater
Bodies
364
-------
better fit of the data sets to a 1:1 relationship. This figure sug-
gests that for a given increase in phosphorus loading to a water
body, one can expect a proportional increase in the chlorophyll a_
concentration. It should be noted that the correlation is a reason-
ably good one even though the summer chlorophyll a concentrations
were not available for all US OECD water bodies, in which case the
annual mean values were used in Figure 87. If one accepts a 1:1
relationship between these two parameters, this approach represents
a good water quality management tool in that it illustrates that if
a water body is receiving three times its permissible phosphorus
loading, it can be expected to have a mean epilimnetic summer chloro-
phyll a_ of about 3 times the permissible level of 2 yg/1. One can,
of course, also use the value of the current phosphorus load/per-
missible phosphorus load quotient as a trophic ranking system for
a wide range of water bodies.
The permissible and excessive phosphorus loading lines on
the Vollenweider phosphorus loading diagram (Figure 19) have
been related to the water quality parameters of mean summer epi-
limnetic chlorophyll a_, mean Secchi depth, and hypolimnetic
oxygen depletion in Figure 88. The basis for this approach was
presented earlier. A sequence of increasing chlorophyll a_ con-
centrations has been inserted into Figure 88 to illustrate how
a variety of boundary loading conditions can be translated into
a water quality parameter on Vollenweider's loading diagram.
Thus, an individual can literally set his own boundary phosphorus
loading levels, as a function of the mean depth/hydraulic
residence time characteristics of a water body, based on his
own concepts of acceptable chlorophyll a_ levels during the summer
season. Further, by use of Equation 39, which relates chlorophyll
a_ levels and Secchi depths in natural waters, one can also sub-
stitute expected Secchi depths as boundary conditions in Vollen-
weider's loading diagram. Using Equation 39, the permissible
loading line (i.e., chlorophyll a_ concentration of 2 jjg/1)
corresponds to a Secchi depth of approximately 4.6 meters while
the excessive loading line (i.e., chlorophyll a concentration of
6 ng/1) corresponds to 2.7 meters. Finally, with the use of
Equation 41, relating hypolimnetic oxygen depletion to Secchi
depth, the permissible and excessive loading lines correspond to
hypolimnetic oxygen depletion rates of 0.3 and 0.6 mg 02/m2/day.
These depletion rates can, in turn, be applied to a water body's
total hypolimnetic oxygen volume to assess the effects of the
phosphorus load on the hypolimnetic oxygen content. These levels
are consistent with generally accepted limnological observations.
Thus, this new relationship (Figure 88) appears to relate a
phosphorus loading level to the more readily appreciated water
quality parameters of chlorophyll a_ concentrations and Secchi
depth. Obviously, it may also be used as a trophic ranking sys-
tem, based on a water body's predicted chlorophyll a concentra-
tions and/or Secchi depths. It has the feature of relating
365
-------
100
• EUTROPHIC
ZONE
T 10
.E
Q.
Summer Meon
' Chlorophyll a
~
- I5Q ."•£--
o
<
o
rr
o
X
CL
2 o.i
0.01
/
''/'
s-'/y,
* 'S.'s
Hypollmnefic
Oxygen
Depletion
OLIGOTROPHIC
ZONE
I 1 1 1 _1 1 1 L! i liillttl t it i i 1 i i I I t i i I I II
O.I
I
10
IOO
MEAN DEPTH,z/HYDRAULIC RESIDENCE TIME.TW
(m/yr)
Figure 88. Relationship Between Vollenweider Phosphorus
Loading Diagram, Summer Mean Chlorophyll a_
and Secchi Depth.
1000
366
-------
Vollenweider's criteria to mean summer conditions in a water body.
As indicated earlier, the summer period is usually the period of
greatest recreational use of a water body. Consequently, this
approach allows individuals concerned with water quality manage-
ment to predict the phosphorus loading reduction necessary to
achieve an "acceptable" summer recreational level of chlorophyll
a or transparency in a water body. This can then be translated
into costs, using methods indicated in an earlier section, so
that the cost-effectiveness of a given eutrophication control
program can be evaluated.
It was not possible to satisfactorily test this latter rela-
tionship because of lack of sufficient data for the mean summer
chlorophyll a concentrations in most of the US OECD water bodies.
Even with the" data supplied by Dillon and Rigler (1974a) and by
Jones and Bachmann (1976), there was still insufficient data for
rigorous testing purposes. The data supplied by Dillon and
Rigler fit Figure 88 reasonably well, although essentially all
his data sets were from oligotrophic water bodies in southern
Ontario. The data from Jones and Bachmann on 16 Iowa Lakes
(1976) produced a poor fit in Figure 88. However, it was also
noted that the data presented by these latter investigators
produced poor agreement between predicted and measured chlorophyll
a concentrations, by + 100 percent in some cases. Jones and
Bachmann supplemented their data with literature values for 143
lakes in the determination of their regression equation. However,
this data was not presented in their report, and thus could not
be tested for its fit in Equation 51. Consequently, the authors
of this report offer this model only as a theoretical contribution
at the present. However, it has its basis in the same theory and
assumptions as does Vollenweider's input-output phosphorus mass
balance model (Vollenweider, 1975a; 1976a) and is related to
several good correlations between the mean phosphorus, chlorophyll
a and Secchi depth in natural waters. This model will be further
tested as more data sets become available, and the results
reported at a later date. It appears to offer promise as a
quantitative tool both for ranking water bodies on a relative
trophic scale and for relating phosphorus loads to several
readily-appreciated water quality parameters.
In summary, the approaches developed in this study offer
methods for the trophic rankings of water bodies based on their
displacement from the permissible loading line on the Vollenweider
diagram (Figure 19) as related to their predicted summer chloro-
phyll a and/or Secchi depth characteristics. In general, these
approaches appear to complement each other and produce relative-
ly similar results.
367
-------
SECTION XIII
DISCUSSION
From an overall point of view, based on initial analysis of
the US OECD eutrophication study data, it appears that the ap-
proach originally developed by Vollenweider and subsequently
modified by him, as well as by Dillon and by Larsen and Mercier,
has considerable validity as a tool for estimating phosphorus
loadings, average phosphorus concentrations and the associated
overall degree of fertility for many US lakes and impoundments.
In general, based on the US OECD investigators' classifications
of the trophic states of their respective water bodies, the US
OECD water bodies can be classified into groups with similar
phosphorus loads and morphometric and hydrologic characteristics.
That is, lakes and impoundments which are generally recognized
as being eutrophic in character plot together in each of the
various loading-response relationships which have been investi-
gated in this study. While the relationship among the water
bodies within a particular group change, depending on the parti-
cular relationship being used, the overall relative positions
of the water bodies hold reasonably well.
This finding gives considerable validity to the nutrient
loading-water body fertility relationship approach originally
proposed by Vollenweider and recently adopted by the US EPA as
a basis for phosphorus loading water quality criteria (US EPA,
1975b; 1976a). At this time, it appears that the phosphorus
loading.criteria presented in the US EPA Quality Criteria for
Water (US EPA, 1976a) should be modified to include some of the
recent modifications of Vollenweider, Dillon and Larsen and Mer-
cier. These modifications are important for water bodies with
short hydraulic residence times, such as some impoundments. From
the information available today, it appears that water bodies with
short hydraulic residence times may have a higher nutrient load-
ing without the same degree of excessive fertilization problems
as would be expected in water bodies with longer hydraulic resi-
dence times. Conceptually, the nutrients are not present in
the water body for a sufficiently long period of time before
being flushed out so as to allow their utilization by the aquatic
plant populations .
368
-------
One of the major difficulties that may be encountered in
attempting to utilize the US OECD results as a basis for develop-
ing uniform national nutrient loading criteria is the fact that,
except for one seepage lake in Florida and an impoundment in
North Carolina, all of the rest of the US OECD water bodies are
located in the colder climates of the East and West coasts and
the upper Midwest area of the US. It is possible that nutrient
loading-response relationships for water bodies from "typically
cold" climates will not hold for the warmer climatic conditions
that prevail in the southeast and southwestern US. Additional
studies should be conducted on warm water body nutrient—response
relationships to ascertain whether these relationships for cold
climates are also applicable for warm climates.
Another factor which may play an important role in causing
southern water bodies to behave differently from their northern
counterparts is that many of these water bodies tend to be more
turbid because of suspended sediments resulting from erosion in
the watershed and suspension of sediment from the bottom (Lee,
1974b) . Some Texas impoundments tend to have severe water quality
problems which are associated with floating macrophytes rather
than with the planktonic or attached algae typical of excessively
fertile waters in cold climates. There is need for nutrient load-
response studies such as those currently being conducted as part
of the OECD international eutrophication study for water bodies
of this type.
There are several aspects of the Vollenweider phosphorus
load-fertility response loading diagrams which should be dis-
cussed. First, it is clear that the relatively simple model
originally developed by Vollenweider is a useful tool to formu-
late phosphorus load-response relationships in such a way as to
be useful as management tools for excessive fertilization con-
trol . For the first time, those concerned with control of eutro-
phication have a basis for predicting the overall trophic state
of a particular water body and the associated water quality that
will arise from either an increase or decrease in its current
nutrient loadings.
With respect to eutrophication modeling, Vollenweider has
demonstrated that nutrient loading, lake morphology (as mani-
fested in mean depth) and hydraulic residence time (i.e., "fill-
ing time") are the three primary factors which govern lake fer-
tility. As further work is done with the Vollenweider loading
curves as part of the international OECD eutrophication study, it
is likely other factors (i.e., color, turbidity, seasonal flush-
ing and mixing regimes and temperature) will be found which will
further refine the Vollenweider loading relationships and thereby
explain apparent deviations from these relationships.
There are certain conditions that must be met before the
Vollenweider loading diagram can be used in management of water
369
-------
quality. The most important of these is that the diagram is only
valid as a predictive tool in eutrophication control when the pri-
mary control of excessive fertilization is through control of a
chemical element such as nitrogen or phosphorus , since the load-
ing diagram was developed for a limiting element. It is not
technically valid to utilize a loading diagram based on phospho-
rus loads for eutrophication control when the key limiting ele-
ment is nitrogen. This report has focused mainly on phosphorus
loading relationships. This is justified on the basis of the
water bodies that have been included in the US OECD eutrophica-
tion study. The majority are phosphorus-limited with respect to
algal growth requirements (Table 9). However, there appear to
be large numbers of water bodies in the US which are nitrogen-
limited. Yet, if phosphorus loading can be decreased to the ex-
tent that phosphorus becomes the limiting element in a water
body, then the use of VollenweiderTs phosphorus loading relation-
ship becomes valid again. This report also discussed the results
obtained in the US OECD eutrophication study for nitrogen load-
water body response relationships. As discussed in this report,
several techniques are available which can be used to assess
the key limiting nutrient in a water body.
Another situation in which the Vollenweider loading diagrams
may not be applicable is for water bodies with low light penetra-
tion. As discussed above, there is reason to believe that water
bodies with high inorganic turbidity may behave anomalously, com-
pared to other US OECD water bodies, with respect to their nutri-
ent load-water body response relationships. Piwoni and Lee (1975)
have noted a similar phenomenon for highly-colored waters and
lakes located in central Wisconsin.
The Vollenweider loading curve may not be applicable with-
out modification to large impoundments with significant amounts
of stratified inter- or underflow which would cause nutrients
present in the inflow waters to not interact with, or be avail-
able to, aquatic plants located in the euphotic zone of the water
body. Under these conditions, it may be necessary to modify the
loading relationship to utilize a modified hydraulic residence
time which would reflect the lack of mixing of the inflowing
waters with the euphotic zone waters.
The Vollenweider loading diagram provides some useful infor-
mation on potential benefits to be derived from manipulating the
limiting nutrient input for a particular water body. In general,
the log-log plot means that substantial reductions in the nu-
trient loads must be made before any significant improvement in
water quality would be expected. This was discussed in relation
to^the possible effects of a detergent phosphate ban on eutro-
phication and water quality in a hypothetical water body in an
earlier section of this report.
370
-------
The Vollenweider loading diagram allows a comparison to be
made of the general trophic status of a particular water body
relative to a certain nutrient loading. While it is highly
successful in categorizing lakes and impoundments into groups
with similar trophic states and water quality, such a diagram
should not be used as a basis for classification of a water
body's trophic status. One should not state that a lake has a
particular trophic state merely because of its position on the
Vollenweider loading diagram. Rather, one can only indicate
that a water body of a given phosphorus loading and mean depth/
hydraulic residence time quotient tends to plot in the same re-
lative area of the Vollenweider diagram as water bodies of similar
phosphorus loads and mean depth/hydraulic residence time values.
A logical extension of the Vollenweider loading diagram is
the development of a relationship between the position of a water
body on this curve, or a modification thereof, and the resultant
water quality in the water body in which concern is focused on
excessive fertilization problems. Ultimately, it should be pos-
sible to make a quantitative estimate of the improvement in water
quality that may result in a water body from reduction of the nu-
trient loading by a certain amount. The phosphorus load-chloro-
phyll a, Secchi depth and hypolimnetic oxygen depletion rate
relationships (Figures 22, 79 and 80, respectively) and the
Vollenweider phosphorus loading diagram incorporating boundary
conditions for chlorophyll a, Secchi depth and hypolimnetic
oxygen depletion (Figure 88T represent significant steps in this
direction. Similar types of relationships should be explored
for various other types of nutrient load-water quality type re-
sponse parameters, such as domestic water supply tastes and odors,
shortening of water treatment plant filter runs, etc.
Associated with several of the load-response relationships
discussed above are descriptive terms such as "excessive", "per-
missible", "oligotrophic" or "eutrophic" which can be translated
into a certain water quality condition. It is important to em-
phasize that these narrative terms go back to the work of Sawyer
(19M-7) who established critical nutrient concentrations for
approximately 20 south-central Wisconsin lakes. Several indi-
viduals, including Vollenweider (1968) have found that for many
lakes with ice cover during the winter, Sawyer's original cri-
tical phosphorus concentrations can be translated into water
quality deterioration which typically manifests itself in in-
creased "greenness" of the water. The "greenness" is roughly re-
lated to the chlorophyll content of the water. Chlorophyll a
values of less than 5 yg/1 are considered to be indicative of
oligotrophic waters with high water quality. Chlorophyll a con-
centrations of greater than about 10 yg/1 are often associated
with waters classified as eutrophic and possessing deteriorated
water quality for many beneficial uses . Chlorophyll concentra-
tions of 2 and 6 yg/1 were found for the Vollenweider diagram
(Figure 88) permissible and excessive loading lines in an earlier
section.
371
-------
It is important to note, however, that Sawyer and others
have been involved with water bodies in which the primary problem
was generally the growth of excessive amounts of planktonic algae,
and in which this growth affected water clarity. This is mani-
fested in an increased "greenness" during periods of algal blooms
and a decreased Secchi depth. In addition, these water bodies
generally have planktonic algal growth limited by the phosphorus
content of water. In general, these water bodies are natural
lakes with little or no color or turbidity. During periods of
little or no algal growth, this water has a high degree of clarity
with Secchi depths exceeding 3 to 4 meters. The residents of the
area who make use of those lakes which have 'excessive' loadings
find the water quality sufficiently impaired during periods of
algal blooms to curtail recreational use of these water bodies.
The impairment of recreational use (i.e., boating, swimming
and fishing) has been used as the basis for determining what con-
stitutes 'excessive' loadings. Lee (1974b) has discussed a pos-
sible lack of application of the Sawyer critical nutrient concen-
trations for the warmer water bodies of the southern US. He noted
these critical concentrations may not produce the same deteriora-
tion of water quality in the normally turbid or colored waters
found in many southern US impoundments as would be expected in
water bodies in the north temperate zones of the US. The public
does not perceive the same decrease in water clarity, resulting
from a certain magnitude of algal blooms, in normally turbid or
colored waters as would be perceived in a normally clear water
body. Further, Lee (1974b) discussed the fact that in many parts
of the US the public will not perceive deteriorated water quality
to the same degree since all the water bodies in some areas of
the US normally have essentially the same water quality, in con-
trast to Wisconsin, Michigan and Minnesota, where there are
several thousand small lakes of widely varying water quality.
Therefore, it must be concluded that, without further study, one
cannot assume that permissible' and 'excessive' loading criteria,
or for that matter, oligotrophic versus eutrophic waters, are
necessarily translated into the same degree of impairment of re-
creational use in various parts of the US.
In addition to impairing recreational use of water, the
stimulation of algal growth by excessive nutrient loading may
also cause significant water quality deterioration in domestic
and industrial water supplies. Lee (1971) has discussed the
potential effects of excessive fertilization on water supply
water quality. The most significant problems are those of taste
and odor production associated with materials excreted from the
algae and a shortening of the length of filter runs. The per-
missible and excessive criteria used on the various loading dia-
grams do not consider the potential effects of the nutrients on
water supply water quality. From the point of view of eutro-
phication control in water supply water bodies, at least for cer-
tain types of algae, the excessive loading line in the Vollen-
weider and other phosphorus loading diagrams may have to be
372
-------
lowered significantly in order to minimize the problems of
excessive fertility on water quality in these water bodies .
It is important to emphasize that the concepts of excessive
nutrient loading pertain to planktonic algal problems and do not
consider the problems of attached algae or attached or floating
macrophytes. It is highly probable that the permissible and ex-
cessive nutrient loadings would also be different in those water
bodies which have a tendency to manifest their excessive nutrient
concentrations in the growth of nonplanktonic aquatic plants .
Another aspect that should be considered with respect to
the Vollenweider loading diagram's emphasis on permissible and
excessive loadings based on recreational impairment is that the
critical nutrient loading is the loading that impairs recreation-
al use. For many water bodies, algal growth problems which may
affect extensive recreational use of the water body are essen-
tially restricted to the summer months. In general, from the
point of view of recreational use, there is little concern about
the algal blooms that occur in late fall in association with
fall overturn and the transport of hypolimnetic nutrients to the
surface waters. Further, algal blooms under the ice, or just
after ice-out, are usually of little or no significance to im-
pairment of recreational use of the water body. Therefore, as
a potential modification of the Vollenweider loading diagram,
it is important to consider the nutrient transport to, and
cycling within, a water body in relation to how a particular
nutrient loading affects water quality. There will likely be
situations where major nutrient loads added in late fall or
during the winter period will have little or no effect on the
following summer's planktonic algal growths. This is an area
that needs additional study to determine the critical nutrient
loads that have the greatest impact on the water body's water
quality.
Examination of the US OECD water bodies for correlations
between their nutrient loads and selected eutrophication re-
sponse parameters (Table 26) has been useful in some instances,
although not for all parameters. A major problem which limits
the usefulness of many of the correlations is that standardiza-
tion of data was not possible in many cases. Data for specific
parameters was scarce for many water bodies. Further, as indi-
cated in Table 11, a variety of analytical procedures were used
to determine the various chemical, biological and physical
parameters of interest in the US OECD eutrophication study.
Also, a wide variety of sampling methodologies (Appendix II)
were employed by the various US OECD investigators.
This lack of uniform analytical and sampling methodologies
was due in part to the nature of the US OECD eutrophication
study. As indicated in an earlier section, essentially no new-
lake studies were begun in the US portion of the OECD
373
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Eutrophication Project. Rather, in general, lakes which had
been studied extensively in the past were selected for inclusion
in the US OECD eutrophication study. In many cases, the goals
of the previous studies on the US OECD water bodies were dif-
ferent from those of the overall OECD efforts. This factor is
a cause of at least part of the problem of standardization of
data. This lack of standardization has made direct comparability
of data between US OECD water bodies of limited value. Inability
to compare eutrophication data between water bodies , as indi'-
cated by Vollenweider (1968), was a major impetus to initiation
of the current OECD Eutrophication Project.
In general, the results of the correlations have indicated
the large majority of US OECD water bodies are phosphorus-limited
with respect to algal nutrient requirements. The correlations
between the phosphorus loads and the various eutrophication re-
sponse parameters are usually better than those between nitrogen
loads and the same response parameters. The exception is the
relationship between phosphorus loads and both annual and grow-
ing season dissolved phosphorus in the US OECD water bodies,
which shows essentially no correlation. By contrast, there is
a good correlation between nitrogen loads and inorganic nitrogen,
indicating that the inorganic nitrogen is not being used by the
algal populations in proportion to its supply to most of the US
OECD water bodies. There is essentially no correlation between
either dissolved phosphorus or inorganic nitrogen and mean
chlorophyll a. By contrast, a good correlation is seen between
total phosphorus and mean chlorophyll a supporting the importance
of phosphorus in controlling algal growths in most of the US OECD
water bodies. This is consistent with the observations concern-
ing algal-limiting nutrients reported by the US OECD investi-
gators (see Table 9).
It is likely that many of the apparently good correlations
observed between nitrogen loadings-concentrations and eutrophica-
tion response parameters are coincidental artifacts of the rela-
tively constant N:P loading ratio observed in the US OECD water
bodies (see Figures 19 and 21). This was noted earlier by
Vollenweider (1968), although he used a. slightly higher N:P
loading ratio (i.e., 15N:1P (by weight)) in the derivation of
his nitrogen loading and mean depth relationship (see Figure 6)
than was indicated in Figures 19 and 21 in this report.
Several of these correlations were useful in the derivation
of several of the relationships derived to evaluate expected
changes in water quality resulting from changes in nutrient loads
to the US OECD water bodies. Particularly, the relationship be-
tween the phosphorus loads and chlorophyll a_, between chlorophyll
a_ and Secchi depth, between hypolimnetic oxygen depletion rate and
Secchi depth, and between spring overturn total phosphorus
and summer chlorophyll a served as the basis for most of these
water quality models (see Figures 22, 78 and 79). These
37H
-------
relationships have been observed in many other water bodies , in
addition to the US OECD water bodies, substantiating their oc-
currence in water bodies of differing trophic conditions. Using
the water quality model relationships derived in this report,
it is now possible to make a technically sound evaluation of the
effects of any given water quality management program. In the
past, eutrophication control programs have largely been directed
toward the removal of phosphorus from domestic wastewater sources.
However, this approach has been largely subjective. The water
quality models derived in this report offer practical tools for
individuals concerned with water quality management and eutro-
phication control.
These water quality models have several advantages over
previous eutrophication modeling efforts. First , they are re-
lated to common eutrophication response parameters which are
readily discernible to both scientist, engineer and layman.
While the Vollenweider loading diagram (Figure 19) offers a good
indication of the overall eutrophication of the US OECD water
bodies, these water quality models then relate the relative de-
gree of fertility of the US OECD water bodies into three common
eutrophication response parameters, namely chlorophyll a con-
centrations, Secchi depth, and the hypolimnetic oxygen depletion
rate. These first two parameters, both related to the "green-
ness" or transparency of water bodies, are more widely appre-
ciated and understood as a good overall indicator of water
quality that the public could perceive than would be the know-
ledge concerning the extent of areal total phosphorus loading
reduction necessary to achieve a permissible phosphorus load.
Another feature of these models is that they are simple, re-
quiring only knowledge of easily-measured parameters. They are
also based on observations concerning nutrient load-eutrophication
response relationships which have been observed in a wide range
of water bodies, lending credibility to their general applica-
bility.
One of their main features is that they allow evaluation of
the effects of a phosphorus eutrophication control program prior
to initiation of the program. This information will enable water
quality managers to inform the public of the expected increase
in water quality that can be achieved as a result of controlling
phosphorus from each of the potentially available sources for a
particular water body to a selected degree. A proper cost-
benefit analysis can then be conducted for a given eutrophication
control program prior to its initiation. With this knowledge and
the water quality models derived in this report, the public can
then determine whether the expected results of a given eutro-
phication control program are justified by its expense. Lee
(1976) has used these above approaches in evaluating the ex-
pected water quality benefits to be derived for the Great
Lakes from a phosphate-built detergent ban in the State of
Michigan.
375
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The Vollenweider phosphorus loading diagram has been re-
lated to the same water quality parameters (see Figure 88). This
relationship was derived in an earlier section of this report
(i.e., Equations 40, 47 and 48). Vollenweider's later models
(1976a), as well as those of Dillon (1975) and Larsen and Mer-
cier (1976) have their basis in the same theoretical phosphorus
mass balance approach as was used to derive the Vollenweider
phosphorus loading diagram (Figure 19). Consequently, relating
the Vollenweider phosphorus loading diagram to these water quality
parameters is pleasing in that it relates the above-mentioned
models of Vollenweider, Dillon and Larsen and Mercier to these
same parameters. Relating them to more readily appreciated
water quality parameters will likely enhance their application
as eutrophication evaluation methodologies.
The results of the trophic status index study indicated
that, in general, the trophic classification systems of the US
EPA (1974d), Carlson (1974) and Piwoni and Lee (1975) produce
approximately the same relative trophic rankings for the US OECD
water bodies. There are a few anomalies noted with all three
indices, with some water bodies of more fertile conditions ranked
more toward the oligotrophic end of the trophic spectrum than
less fertile water bodies. All three ranking systems producing
similar results may be partially due to the fact that all three
systems have several common parameters. These parameters may
have been of sufficient importance in the trophic rankings,
relative to the other parameters, that they influenced all three
systems toward similar results.
The approach developed in this report of ranking the US OECD
water bodies on the basis of their excess phosphorus loads (i.e.,
ratio of current phosphorus load to permissible phosphorus load)
offers another simple method of relating phosphorus loads to
eutrophication response parameters. Examination of the rela-
tionship between the excess phosphorus load and mean chlorophyll
a (Figure 86) shows a positive correlation exists between these
parameters, although there is a scatter of the data. This data
scatter is due in part to the fact that the mean chlorophyll a
values used in this relationship are a mixture of annual and
growing season values. This relationship is similar to that of
Vollenweider which relates the phosphorus load, as modified by
mean depth and hydraulic residence time, to the mean chlorophyll
a (see Figure 22), except that the chlorophyll a is being corre-
lated with the excess phosphorus load in this model.
The relationship between excess chlorophyll a_ and excess
phosphorus' load also showed good promise as a water body trophic
ranking system. The excess chlorophyll a was referenced to the
permissible 2 yg/1 chlorophyll a concentration derived in an
earlier section (see Equations 4~8 and 49). This relationship
(Figure 87) is interesting in that, although the data is somewhat
376
-------
scattered, it appears to illustrate a 1:1 relationship between
the excess phosphorus load and excess chlorophyll a in the US
OECD water bodies. This suggests that a water body receiving
a phosphorus load of a certain magnitude above the permissible
level will experience a mean summer chlorophyll a_ level of
essentially the same proportion above the 'permissible' chloro-
phyll level. While this is not unexpected to some degree, it is
surprising to note that this approximately 1:1 relationship
between excess phosphorus and excess chlorophyll a_ appeared to
hold over the whole phosphorus loading and chlorophyll a_ range
of the US OECD water bodies. Thus, one could use the current
phosphorus load/permissible phosphorus load quotient as a trophic
ranking system for a wide range of water bodies.
The applicability of the Vollenweider loading relationships
for shallow lakes is an area that needs further attention.
Examination of the US OECD eutrophication study data, although
limited for these types of water bodies , shows that shallow
lakes and impoundments do not appear to have significantly
different chlorophyll a and Secchi depth responses to phosphorus
loads than do the other US OECD water bodies (Figures 22 and 79,
respectively). It should be noted that the nutrient load estimates
for many of the shallow lakes and impoundments are based on land
use in the watershed and the appropriate nutrient export coeffic-
ients . Because of the uncertainty of the nutrient loads for these
water bodies at this time, it would be inappropriate to conclude
that shallow water bodies have different nutrient load-eutrophica-
tion response relationships than do deeper water bodies.
The primary distinguishing feature between shallow lakes and
deeper lakes is the absence of thermal stratification. For the
purposes of this report, a shallow lake is one with a mean depth
of 3 m or less. Generally, water bodies of this type do not
thermally stratify, except under highly sheltered conditions in
which wind-induced mixing of the water column is hampered. The
lack of permanent thermal stratification during the growing
season plays a major role in nutrient recycling. In deep lakes
(i.e., lakes that remain thermally-stratified during the entire
growing season), the thermocline represents a barrier to nutrient
recycling from the hypolimnetic waters. The effectiveness of the
thermocline as a nutrient barrier is highly variable and varies
from lake to lake. As discussed by Stauffer and Lee (1973),
some water bodies, such as Lake Mendota in Madison, Wisconsin,
which permanently stratify during the summer, still derive
appreciable nutrients from the hypolimnion, as a result of thermo-
cline migration. In fact, this phenomenon appears to be the pri-
mary controlling mechanism governing many of the algal blooms
that occur in Lake Mendota during the summer.
As shown by Lee et. a_l (1976), appreciable phosphorus re-
cycling occurs in aerobic waters. This recycling is associated
377
-------
primarily with mineralization of algal phosphorus. This phenomenon
would be especially important in shallow lakes because they tend
to have warmer water overall than the surface waters of deeper
lakes of the same region. The higher temperatures in the shallow
lakes would promote the phosphorus mineralization. This higher
overall temperature, in addition to increasing the rate of
nutrient recycling, also affects many other factors controlling
algal growth including the algal growth rate and algal predation
by zooplankton. Further, higher temperatures would likely have
some effects on the types of algae present. It is therefore
reasonable to conclude that, as a result of their somewhat
elevated temperatures compared to deeper water bodies , shallow
lakes would tend to use their nutrients , especially phosphorus ,
to a somewhat greater degree and at a faster rate. This could cause
shallow lakes to not fit as well as deeper water bodies in the
Vollenweider nutrient load-eutrophication response relationships
or to deviate from the Vollenweider nutrient load relationships
which were developed for deeper water bodies.
Another factor which could influence the behavior of shallow
lakes, compared to deeper water bodies , in the Vollenweider
phosphorus loading relationships is water clarity. In general,
shallow water bodies tend to be more turbid as a result of suspen-
sion of the sediments into the water column. This suspension arises
from several factors, the most important of which is wind-induced
mixing. Also important in their suspension is the mixing of sedi-
ments to the overlying waters from the activities of fish, such
as carp burrowing in the sediments. As discussed by Lee (1970),
anaerobic fermentation of the sediments, as well as benthic organ-
ism biomass suspension due to photosynthesis, also contribute to
the mixing of the sediments in the water column. Another factor
which would tend to make shallow lakes more turbid in hardwater
areas is the precipitation of calcium carbonate which, under cer-
tain extreme conditions, can produce a "milky" appearance in the
water column.
The elevated turbidity often present in shallow lakes could
cause these water bodies to deviate from the Vollenweider relation-
ships in a variety of ways. One of the most important of these
possible deviations is the promotion of light limitation of algal
growth. Therefore, even though water temperatures would tend to
be higher and aerobic nutrient recycling faster in shallow lakes,
algal growth in these water bodies may not be stimulated because
of increased detrital and mineral activity in the water, which
could cause a light limitation of algal growth in these water bodies
This increase in nonalgal turbidity in shallow lakes would
tend to make phosphorus somewhat less available for algal growth
because of sorption and precipitation reactions in the water body.
Detrital minerals, especially clays, have a relatively high capac-
ity for phosphate uptale. Also, calcium carbonate precipitation
in hard water systems would probably result in coprecipitation of
378
-------
hydroxyapatites. On the other hand, since the water in shallow
lakes is almost always oxygenated, phosphate sorption by freshly
precipitated iron hydroxide would be minimal, Thus , from an over-
all point of view, it is likely that less of the phosphorus
added to a shallow lake would be available to promote algal
growth than would be seen in deeper water bodies.
The increased turbidity often present in shallow lakes would
tend to greatly alter the public's response to planktonic algal
growths. The public in general tends to perceive change in a
water body as a significant detrimental factor, Planktonic
algal growth in a water body that is generally somewhat turbid
because of sediment suspension in the water column would be less
objectionable to the public since the effect of the algal on
overall water clarity is more difficult to perceive than in less
turbid water bodies , In a study currently being conducted by
Lee et_ al. (1977), it has been found that Lake Ray Hubbard, an
impoundment near Dallas, Texas, tends to have a markedly different
chlorophyll-Secchi depth relationship than do the US OECD water
bodies. Several arms of this impoundment are 1 to 3 m deep and
contain large amounts of mineral and detrital turbidity in the
water column. A given planktonic algal chlorophyll in this lake
is associated with a significantly shallower Secchi depth than
found in typical US OECD eutrophication study water bodies.
Large algal blooms occur in this lake, yet have limited impact
on its recreational use because the planktonic chloroDhyll does
not change overall water clarity to a significant degree compared
to non-bloom conditions in the water body.
Many shallow lakes and the shallow waters of deeper lakes tend
to support large populations of attached algae and macrophytes.
Since the Vollenweider nutrient relationships are based primarily
on planktonic algal chlorophyll, growth of non-planktonic plants
tend to act as a sink for nutrients during the growing season.
Therefore, less planktonic algal production will occur in shallow
lakes containing high populations of attached algae and macrophytes
From the above discussion it is apparent that a variety of
factors would tend to cause shallow lakes to deviate from the
Vollenweider nutrient load-eutrophication response relationships.
However, the effects of many of these factors tend to oppose one
another, with the result that it is impossible at this time to
predict, without additional study, whether shallow lakes and
impoundments will tend to show different nutrient load-eutrophica-
tion response relationships than other deeper water bodies . The
combined OECD Eutrophication Program study data from the Alpine ,
Nordic, North American and Shallow Lakes and Impoundments Projects
will likely provide a sufficient data base to determine whether
shallow lakes and impoundments tend to deviate significantly from
the nutrient load-eutrophication response relationships than
deeper water bodies.
379
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for public comment. Washington, D.C.) Document undated.
501 pp.
US Environmental Protection Agency. 1975c. National Water
Quality Inventory. 1975 Report to Congress. Office of
Water Planning and Standards, Washington, D.C. 48 pp.
US Environmental Protection Agency. 1976a. Quality Criteria
for Water. US EPA Report EPA-440/9-76-023. 501 pp.
US Environmental Protection Agency. 1976b. Water Quality
Criteria Research of the US Environmental Protection
Agency. Proceedings of an EPA-Sponsored Symposium on
Marine, Estaurine and Fresh Water Quality. US EPA Report
EPA-600/3-76-079. pp. 185-205.
Uttormark, P. D., J. D. Chapin and K. M. Green. 1974.
Estimating Nutrient Loading of Lakes from Non-Point
Sources. US EPA Report EPA-66 D/3-74-02'0 . 112 pp.
Vallentyne, J. R. 1974. The Algal Bowl. Information Canada,
Special Publication No. 2"2 , Department of the Environment,
Fisheries and Marine Service, Ottawa, Ontario. 186 pp.
Vollenweider, R, A. 1968. Scientific Fundamentals of the
Eutrophication of Lakes and Flowing Waters, with Particular
Reference to Nitrogen and Phosphorus As Factors in Euto-
phication. Technical Report DAS/CSI/68.27, Organization for
Economic Cooperation and Development (OECD), Paris. 250 pp.
396
-------
Vollenweider, R. A. 1969. Moglichkeiten Und Grenzen elementarer
Modelle der Stoffbilanz von Seen. Arch. Hydrobiol. 66:l-36.
Vollenweider, R, A. 1975a. Input-Output Models, with Special
Reference to the Phosphorus Loading Concept in Limnology.
Schweiz Z. Hydrol . 3_7 : 53-84,
Vollenweider, R. A, 1975b. Personal Communication. (Canada
Centre for Inland Waters-Burlington, Ontario). June 13,
1975 .
Vollenweider, R, A. 1975c. Personal Communication. (Canada
Centre for Inland Waters-Burlington, Ontario). August 15,
1975.
Vollenweider, R. A. 1975d. Personal Communication. (Canada
Centre for Inland Waters-Burlington, Ontario). December 8,
1975 .
Vollenweider, R. A. 1976a. Advances in Defining Critical
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Vollenweider, R. A. 1976b. Personal Communication. (Canada
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1976 .
Vollenweider, R. A. 1977. Personal Communication. (Canada
Centre for Inland Waters-Burlington, Ontario). January 20,
1977 .
Vollenweider, R. A. and P. J. Dillon. 1974. The Application
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397
-------
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398
-------
APPENDIX I
FINAL REPORT OUTLINE
(North American Project)
I. Introduction - Short Past History of Water Body
II. Brief Geographical Description of Water Body
A. Latitude and Longitude (Centroid of Water Body)
B. Altitude Above or Below Sea Level
C. Catchment Area (Including Area of Surface Water)
D. General Climatic Data (Ice Coverage; Average Month-
ly Air Temperature; Wind Patterns; Evaporation; etc.)
E. General Geological Characteristics (Nature of
Bedrock; Subsoil and Soils; Importance of Land
Erosion)
F. Vegetation
G. Population
H. Land Usage (Industrial, Urban, Agricultural, etc.)
I. Use of Water (Drinking, Sport, Fishing, etc.)
J. Wastewater Discharges (Population and Industry)
III. Brief Description of Morphometric and Hydrologic Char-
acteristics of Water Body
A. Surface Area of Water (Length, Width, Shore Length,
etc. )
B. Volume of Water (Information on Regulation)
C. Maximum and Mean Depth
D. Ratio of Epilimnion over Hypolimnion
E. Duration of Stratification
F. Nature of Lake Sediments
G. Seasonal Variation of Monthly Precipitation
(Maximum, Minimum Conditions on Drainage Basin)
HOO
-------
H. Inflow and Outflow of Water (Also Underground)
I. Water Currents
J. Water Renewal Time (Residence Time)
IV. Limnological Characterization Summary
A. Physical
1. Temperature
2. Conductivity
3. Light
4. Color
5. Solar Radiation
B. Chemical
1. pH
2. Dissolved Oxygen
3. Total Phosphorus (Including Fraction Forms)
4. Total Nitrogen (Including Fraction Forms)
5. Alkalinity arid/or Acidity
6. Ca, Mg, Na, K, SO^, Fe
C. Biological
1. Phytoplankton (Chlorophyll; Primary Productivity;
Algal Assays; Identification and Count)
2. Zooplankton (Identification and Count)
3. Bottom Fauna
4. Fish
5. Bacteria
6. Bottom Flora
7. Macrophytes
V. Nutrient Budgets Summary
A. Phosphorus Source Kg/Yr
Waste Discharges xx
Land Runoff xx
Precipitation xx
Ground Water xx
Other xx
Total xx
401
-------
B. Nitrogen _ Source Kg/Yr
Waste Discharges xx
Land Runoff xx
Precipitation xx
Ground Water xx
Other xx
Total xx
C. Other Nutrient Budgets, If Available
VI. Discussion
A. Limnological Characterization
B. Delineation of Trophic Status
C. Trophic Status Versus Nutrient Budgets
1. Present Vollenweider Numbers
(Grams/Meter2/Year)
2. Mean Depth/Hydraulic Residence Time
VII. Summary
402
-------
BLACKHAWK (WISC. ) """
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(IMPOUNDMENT)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depthb
Mean Dissolved Phosphorus13
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NHJ+N03+N02 as N)
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Summer Mean Epilimnetic Values:
Total Phosphorus
Dissolved Phosphorus
Inorganic Nitrogen
Eutrophic in 1972-1973
3.6 x 107 m2
8.9 x 105 m2
4.9 m
0 .5 yr
227 mg/1 as CaC03
471 ymhos/cm @ 25°C
3.6 m
0.04° mg P/l
0.12C mg P/l
1.02 mg N/l
14.6 yg/1 (first two meters of
water column)
0 kg P/yr
1900-2070 kg P/yr
2.13-2.32 g P/m2/yr
0 kg P/yr
20 ,900 kg N/yr
23.4 g N/m2/yr
0.05 mg P/l
0.015 mg P/l
0.54 mg N/l
Invest igator - Indicated Comments
aDoes not include water body surface area.
Data based on samples obtained at six-week intervals at either
one or two meter depth intervals in the deepest part of the im-
poundment .
c .
Average winter concentrations.
Dash (-) indicates no data available.
*Data taken from Piwoni and Lee (1975)' and personal communication
(Table 3).
404
-------
BROWNIE (MINN.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
as N)
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Eutrophic in 1971
2
2
4.7 x 105 m2
7.3x10 m
6.8m
2 .0 yr
123-136 mg/1 as CaCO,
O
400-475 ymhos/cm @ 25°C
1.5 m
< 0.01b mg P/l
< 0.055b mg N/l
5.9b yg/1
82.1C kg P/yr
3.8 kg P/yr
1.18 g P/m2/yr
Investigator-Indicated Comments
Does not include water body surface area.
Summer average surface values
Includes urban storm water drainage.
Dash (-) indicates no data available.
"Data taken from Shapiro (1975a) and personal communication
(Table 3).
405
-------
CALHOUN (MINN.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
as N)
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading :
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Eutrophic in 1971
7.6 x 106 m2
1.7 x 106 m2
10.6 m
3.6 yr
80-123 mg/1 as CaC03
400-500 ymhos/cm @ 25°C
2.1m
< 0.005b mg P/l
0.106b mg P/l
< 0.055b mg N/l
6.0b yg/1
1370U kg P/yr
91 kg P/yr
0.86 g P/m2/yr
Investigator-Indicated Comments
Does not include water body surface area.
Summer surface average values.
c
Includes urban stormwater drainage.
JDash (-) indicates no data available.
"Data taken from Shapiro (1975a) and personal communication
(Table 3).
406
-------
CAMELOT-SHERWOOD (WISC . )'"
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(IMPOUNDMENT)
b
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus3
Mean Total Phosphorusr
Mean Inorganic Nitrogen
(NHJ+N03+N02 as N)
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Summer Mean Epilimnetic Values :
Total Phosphorus
Dissolved Phosphorus
Inorganic Nitrogen
Eutrophic in 1972-1973
9.1 x 107 m2
2.8 x 106 m2
3 m
0.09 - 0.14 yr
125 mg/1 as CaC03
311 ymhos/cm @ 25°C
2.0m
0 .008° mg P/l
0.03C mg P/l
1.07
N/l
6.3 yg/1 (first two meters of
water column)
0 kg P/yr
6600-7580 kg P/yr
2 .35-2.68 g P/m2/yr
0 kg N/yr
97,600 kg N/yr
34.6 g N/m2/yr
0.04 mg P/l
0.008 mg P/l
0.59 mg N/l
Investigator-Indicated Comments
Lake highly colored because of humic content.
Does not include water body surface area.
Data based on samples obtained at six-week intervals at either one
or two meter depth intervals in the deepest part of the impoundment
Average winter concentrations.
Dash (-) indicates no data available.
''Data taken from Piwoni and Lee (1975) and personal communication
(Table 3).
407
-------
CANADARAGO (N.Y.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
rx b
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth0
Mean Dissolved Phosphorus0
Mean Total Phosphorus0
Mean Inorganic Nitrogen0
(NH4+N03+N02 as N)
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
aEutrophic in 1968-1969
2
10 m
106 m2
1.8
7 .6
7.7m
0 .6 yr
248 mg/1 as
°
223 ymhos/cm @ 25C
1.8 m
1968
0 .02
0.05
0 .38
13
1971=195
1969
0.02 mg P/l
0.04 mg P/l
0.44 mg N/l
7 yg/1
1972=136; 1973=236
g C/m^/yr
2800 kg P/yr
3200 kg P/yr
0.8 g P/m2/yr
7800 kg N/yr
128 ,600 kg N/yr
18.0 g N/m2/yr
Spring
Overturn Values
1968r96~9
Growing Season(May-Sept)
Mean Epilimnetic Values
1968 1969
Mean Secchi Depth (m) - 1.7
Total Phosphorus (mg P/l) 0.06 0.04 0.02 0.03
Dissolved Phosphorus(mg P/l) 0.020 0.013 0.016 0.015
Inorganic Nitrogen (mg N/l) 0.21 0.30 0.38 0.44
Chlorophyll a (yg/1) 9 5 - -
Investigator-Indicated Comment^
aPrior to completion of tertiary waste treatment plant for treatment
of major point source nutrient input in 1972.
(continued)
408
-------
DATA SUMMARY FOR CANADARAGO (N.Y.)"- (continued)
Does not include water body surface area.
Q
Data based on samples obtained monthly from early May-late
November, 1968-1969, from ten stations at the 0-4.5 m depth,
4.5-9.0 m depth, and 9.0 bottom depth.
Dash (-) indicates no data available.
s'c
Data taken from Hetling et al. (1975) and persona] communi-
cation (Table 3).
409
-------
CAYUGA (N.Y.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
N)
.b
as
Mean Chlorophyll a_~
Annual Primary Productivity
Phosphorus Loading
Point Source
d
Non-Point Source
Surface Area Loading
Nitrogen Loading :
Point Source
Non-Point Source
Surface Area Loading
Secchi Depth (m)
Dissolved Phosphorus (mg P/l)
Inorganic Nitrogen (mg N/l)
Chlorophyll a (yg/1)
Mesotrophic in 1972-1973
q ?
2.0 x 1(T m
1.7 x 108 m2
54 m
8 . 6 yr
102 mg/1 as CaC03
575 umhos/cm @ 25°C
1972 1973
2.3
0.003
0 .02
0.37
2.3m
0.004 mg P/l
0.02 mg P/l
0.51 mg N/l
5 yg/1
58° g C/m2/yr
63,900 kg P/yr
77 ,100 kg P/yr
0.8 g P/m2/yr
168 ,000 kg N/yr
2 ,300 ,000 kg N/yr
14.3 g N/m2/yr
Growing Season (May-Sept)
Mean Epilimnetic Values
T9T2 19T3
0 .003
0.35
7 .4
2.4
0.001
0.36
5.6
Total Phosphorus ranges from 0.015-0.022 mg/1 throughout water
column during all seasons of the year.
I_nye_£tigator-I_ndicated Comments
Data does not include water body surface area.
(continued)
410
-------
DATA SUMMARY FOR CAYUGA (N.Y.) - (continued)
Data based on samples collected at three-five sampling sta-
tions in 1972-1973, at surface, 2m, 5m and 10m, at weekly in-
tervals during June-August, biweekly intervals during mid-
April-May and September-October, and monthly intervals the
rest of the year, down the long axis of the lake.
°Based on Barlow (1969) and Peterson (1971).
d!970-1971 data.
*
Data taken from Oglesby (1975) and personal communication
(Table 3).
-------
CEDAR (MINN.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NHJ+N03 as N)
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Eutrophic in 1971
1.6 x 106 m2
6.9 x 105 m2
6.1 m
3.3 yr
71-109 mg/1 as CaCO,
400 ymhos/cm @ 25°C
1.8m
< 0.005b mg P/l
0.055b mg P/l
< 0.055b mg N/l
20^ yg/1
205° kg P/yr
36 kg P/yr
0.35 g P/m2/yr
Investigator-Indicated Comments
Does not include water body surface area.
Summer surface average values.
c
Includes urban stormwater drainage.
Dash (-) indicates no data available.
A
Data taken from Shapiro (1975a) and personal communication
(Table 3).
412
-------
COX HOLLOW LAKE (WISC.) "
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(IMPOUNDMENT)
b
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth b
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NHj + NC>3+NO~ as N)
Mean Chlorophyll ab
Annual Primary Productivity
Phosphorus Loading :
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Summer Mean Epilimnetic Values:
Total Phosphorus
Dissolved Phosphorus
Inorganic Nitrogen
Eutrophic in 1972-1973
1.6 x 107 m2
3.9 x 10 5 m2
3.8m
0.5 - 0.7 yr
205 mg/1 as CaCO
3
440 ymhos/cm @ 25°C
1.5 m
0.04° mg P/l
0.10° mg P/l
0.83° mg N/l
26.5 yg/1 (first two meters of
water column)
0 kg P/yr
630-810 kg P/yr
1.62-2.08 g P/m2/yr
0 kg N/yr
7410 kg N/yr
19 .1 g N/m2/yr
0.06 mg P/l
0.02 mg P/l
0.36 mg N/l
Investigator-Indicated Comments
Does not include water body surface area.
Data based on samples obtained at six-week intervals at either
one or two meter depth intervals in the deepest part of the im-
poundment .
Q
Average winter concentration.
Dash (-) indicates no data available.
;'t
Data taken from Piwoni and Lee (1975) and personal communication
(Table 3).
413
-------
DOGFISH (MINN.) '
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
as N)
Oligotrophic in 1971-1972
8.8 x 10F
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
2.9 x 10
4.0 m
3.5 yr
1971
8
17 .3
2 .7
0.010
0.39
6 (4)c
m
m
1972
10 mg/1 as CaC03
16.0 ymhos/cm @ 25°C
2.5m
0.010 mg P/l
mg N/l
4 (2)c yg/1
0 kg P/yr
4.9 kg P/yr
0.02 g P/m2/yr
Non-Point Source
Surface Area Loading
Mean pH = 6.0
Investigator-Indicated Comments
Water slightly stained with humics.
Phytoplankton characterized by chrysophytes and cryptomonads except
during summer and fall, when greens and blue greens were significant
aDoes not include water body surface area.
May-October mean values for 1971-1972.
"Euphotic zone values.
Dash (-) indicates no data available.
Data taken from Tarapchak et al. (1975) and personal communication
(Table 3).
-------
DUTCH HOLLOW LAKE (WISC.)*
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(IMPOUNDMENT)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth13
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NHJ+N03+ N02 as N)
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Eutrophic in 1972-1973
1.2 x 107 m2
8.5 x 105 m2
3 m
1. 8 yr
133 mg/1 as CaC03
252 ymhos/cm @ 25°C
0.8m
0.020° mg P/l
0.40C mg P/l
°
0.61
N/l
33.9 yg/1 (first 2 meters of water
column)
0 kg P/yr
810-870 kg P/yr
0.95-1.01 g P/m2/yr
0 kg N/yr
8840 kg N/yr
10.4 g N/m2/yr
Summer Mean Epilimnetic Values:
Total Phosphorus
Dissolved Phosphorus
Inorganic Nitrogen
0.12 mg P/l
0.01 mg P/l
0.22 mg N/l
Investigator-Indicated Comments
Does not include water body surface area.
Data based on samples obtained at six week intervals at
either one or two meter depth intervals in the deepest
part of the impoundment.
Average winter concentrations.
Dash (-) No data available.
Data taken from Piwoni and Lee (1975) and personal communication
(Table 3).
415
-------
GEORGE (N.Y.)"
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
( LAKE )
Trophic State Oligotrophic-Mesotrophic in 1972-73
o 2
Drainage Area 6.1 x 10 m
8 2
Water Body Surface Area 1.1 x 10 m
Mean Depth 18 m
Hydraulic Residence Time 8 yr
Mean Alkalinity 21 mg/1 as CaC03
Mean Conductivity 86 ymhos/cm @ 25°C
Mean Secchi Depth 8.5 m
Mean Dissolved Phosphorus 0.002 mg P/l
Mean Total Phosphorus 0.0085 mg P/l
Mean Inorganic Nitrogen
as N) 0.05 mg N/l
Mean Chlorophyll a
— 2
Annual Primary Productivity 7.2 g C/m /yr
Phosphorus Loading:
Point Source 80 kg P/yr
Non-Point Source 7800 kg P/yr
2
Surface Area Loading 0.07 g P/m /yr
Nitrogen Loading:
Point Source 17,700 kg N/yr
Non-Point Source 201,000 kg N/yr
2
Surface Area Loading 1.8 g N/m_/yr
Investigator-Indicated Comments
water body surface <
Dash (-) indicates no data available.
Does not include water body surface area.
ft
Data taken from Ferris and Clesceri (1975) and personal
communication (Table 3).
416
-------
HARRIET (MINN.)*
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
as N)
Eutrophic in 1971
4.8 x 106 m2
6 2
1.4x10 m
8.8m
2 .4 yr
92 - 124 mg/1 as
360-425 ymhos/cm @ 25°C
2.4m
<0.005b mg P/l
0.062b mg P/l
<0.055b mg N/l
b
3.
yg/i
890 kg P/yr
126 kg P/yr
0.71 g P/m2/yr
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Investigator-Indicated Comments
1Does not include water body surface area.
Summer average surface values.
G
Urban stormwater drainage only.
Dash (-) indicates no data available.
Data taken from Shapiro (1975a) and personal communication
(Table 3).
b
417
-------
ISLES (MINN.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
O,
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NH4+N03 as N)
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Investigator-Indicated Comments
Does not include water body surface area.
Summer surface average values.
Q
Urban storm water drainage only.
Dash (-) No data available.
*Data taken from Shapiro (1975a) and personal communication
(Table 3).
Eutrophic in 1971
2.8 x 106 m2
4.2 x 105
2.7m
0.6 yr
68-131 mg/1 as CaC03
380-470 ymhos/cm @ 2!
1.0m
<0.010b mg P/l
0.110b mg P/l
<0.055b mg N/l
53 yg/1
828 kg P/yr
23 kg P/yr
2.03 g P/m2/yr
418
-------
KERR RESERVOIR (N. CAROLINA-VIR.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(IMPOUNDMENT)
Trophic State
Drainage Areaa
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity0
Mean Conductivity °
Mean Secchi Depth °
Mean Dissolved Phosphorus0
Mean Total Phosphorus °
Mean Inorganic Nitrogen0
(NHj+N03+NO~ as N)
Mean Chlorophyll ac
Annual Primary Productivity c
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point 'Source
Non-Point Source
Surface Area Loading
Growing Season Mean
__ Epilimnetic Values
06
Total Phosphorus
(mg P/l)
Dissolved Phos-
phorusCmg P/l)
Inorganic Nitrogen
(mg N/l)
Chlorophyll a
(yg/D
Primary Productiv-
ity (g C/m2/day)
Mean Hypolimnetic D.O. Content (mg/1)
Roanoke Arm
Nutbush Arm
(continued)
419
Eutrophic-Mesotrophic in 1975
2.02 x 1010,m2
Roanoke Arm0 Nutbush Arm13 „
1.2 x 10»
10.3
0.2
28
100
1.4
0.01
0.03
0.28
13.2
171
630,600
13,600
5.2
18 ,500
4 ,509 ,600
36.2
5.1) x 10 ' m
8.2 m
5.1 yr
22 mg/1 as CaC03
123 ymhos/cm @ 2
1.2 m
0 .02 mg P/l
0.03 mg P/l
0.22 mg N/l
21.2 yg/1
249 g C/m2/yr
30,500 kg P/yr
5,500 kg P/yr
0 .7 g P/m2/yr
7 ,480 kg N/yr
114 ,400 kg N/yr
2 .4 g N/m2/yr
25°C
Roanoke Arm Nutbush Arm
s
)
gen
iv-
0.02
0 .006
0 .13
14
0.7
0
0
0
1
0
.03
.007
.10
8
.7
Spring Overturn
Mean Values
RoanokeArmNutbush Arm
0 .04
0 .006
0 .30
0 .05
0 .010
0 .20
3/14/74 5/6/74
9.6 6.8
10 .8 5.1
7/3/74
0 . 3
1.1
-------
ft
DATA SUMMARY FOR KERR RESERVOIR (N. CAROLINA-VIR.) - (continued)
Investigator-1n d i c a t e d Commen t s
The upper ends of both arms of the reservoir are nitrogen-limited,
while the lower ends of both arms are phosphorus-limited, with
respect to algal nutrient requirements.
Does not include water body surface area.
The two principal arms of the impoundment have been treated
separately.
C •
Data based on samples obtained at approximately three-month in-
tervals at four stations, six miles apart in the Roanoke Arm, and
five stations, three-five miles apart in the Nutbush Arm, during
the period 1971-1974. All loading estimates for April, 1974,
March, 1975 ar.e based on monthly sampling frequency for all
principal phosphorus inputs.
Dash(-) indicates data not available.
ft
Data taken from Weiss and Moore (1975) and personal communication
(Table 3).
420
-------
LAMB (MINN.)*
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Oligotrophic in 1971-1972
2.0 x 10
4. 0 x 10!
4.0m
2. 3 yr
1971
47
1. 8
0.013
0. 51
m
m
1972
36 mg/1 as CaCO,
6 (5)
c
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NHiJ + NOo+NO" as N)
/
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Investigator-Indicated Comments
Lake highly colored by humic materials. Green and blue-green
algae dominates summer and fall phytoplankton community..
Does not include water body surface area.
May-October mean values for 1971-1972.
Euphotic zone.
Dash (-) No data available.
"Data taken from Tarapchak et_ al. (1975) and personal communication
(Table 3).
-o.
47 -ymhos/cm @ 25 C
2.2m
0.012 mg P/l
- mg N/l
3 (3)C ug/1
0 kg P/yr
12.1 kg P/yr
0.03 g P/m2/yr
421
-------
MEANDER (MINN.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NH4+N03+NOI as N)
1
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Oligotrophic in 1971-1972
1.7 x 106 m2
3.6 x 105 m2
5.0m
2.7 yr
1971
20.4
3.1
0.012
0 .45
1972
8 mg/1 as CaCO,
16.7 ymhos/cm {
3.0m
0.009 mg P/l
- mg N/l
2 (l)c yg/1
0 kg P/yr
9.9 kg P/yr
0.03 g P/m2/yr
25°C
Non-Point Source
Surface Area Loading
Mean pH = 5.5
Investigator-Indicated Comments
Chrysophytes and crytomonads characterize phytoplankton, except
during summer and fall when green and blue-green algae-are dominant
Does not include water body surface area.
May-October mean values.
Euphotic zone.
Dash (-) indicates no data available.
.'.
Data taken from Tarapchak et_ al_. (1975) and personal communication
(Table 3).
422
-------
MENDOTA (WISC.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
.b
Mean Total Phosphorus
Mean Inorganic Nitrogen
as N)
b
c
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Euphotic zone = to 3 m depth
Euphotic zone volume = 9 x 10
Summer eiplimnion mean depth =
Summer epilimnion mean volume
Eutrophic in 1965-1966
6.9 x 108 m2
3.9 x 107 m2
12 m
4 . 5 yr
160 mg/1 as CaCO
300 ymhos/cm
3.0m
0.12 mg P/l
0.15 mg P/l
0.64 mg N/l
25°C
10 (20) yg/1
1100e g C/m2/yr
908f kg P/yr
45,600 kg P/yr
1.2 g P/m2/yr
3130f kg N/yr
540 ,700 kg N/yr
13 g N/m2/yr
7
m
to 10 m
- 3 x 10?
x m
Investigator-Indicated Comments^
Does not include water body surface area.
Based on 1965-1966 study by students and staff of Water Chemistry
Program, Univ. of Wisconsin, Madison, and compiled by Lee (1966).
-i
'Mean epilimnetic concentration.
(continued)
423
-------
DATA SUMMARY FOR MENDOTA (WISC.)"- (continued)
Growing season concentration.
Estimated from chlorophyll and light intensity data.
Point source loadings are mainly storm water drainage inputs.
&
Data taken from Lopez and Lee (1975) and personal communication
(Table 3).
-------
MICHIGAN (MICH.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NHj + NC>3+N0~ as N)
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading6:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading6:
Point Source
Non-Point Source
Surface Area Loading
Euphotic zone = 8 m
Nearshore-Mesotrophic in 1972
Open waters-Oligotrophic in 1974
1 Q v 1 nil m2
1.8 x 10
5.8 x 10
84 m
nr
10 m2
30-100 yrh
Nearshore^
107
265
2.3
<0. 002
0.015
0.20
187-247
Open Waters
113 mg/1 as CaC03
255 ymhos/cm @ 25°C
m
1971
1974
0.001 mg P/l
0.013° mg P/l
0.17° mg N/l
2 yg/i
150d g C/m2/yr
3.4 x 10 kg P/yr
2.2 x 106 kg P/yr
0.14 g P/m2/yr
0.10 g P/m2/yr
1971 = 1.3 g N/m /yr
b
Investigator-Indicated Comments
Does not include water body surface area.
Data based on samples obtained at the four meter depth from one
station over an 18 month period in 1970-1971.
CAfter Schelske and Callender (1970).
dAfter Vollenweider (1975a).
SAfter Lee (1974a).
Dash(-) indicates no data available.
&
Data taken from Piwoni et al. (1976) and personal communication
(Table 3).
425
-------
LOWER LAKE MINNETONKA (MINN.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NHJ+N03 +N0~ as N)
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Eutrophica in 1973
3.7 x 108 m2
2.62 x 107 m2
.3m
.3°
1969
6.3° yr
125
1.5
0.06
21
440
8900
4000
0.5
Growing Season Mean
Epilimnetic Values
1973
- mg/1 as CaC03
125 ymhos cm @ 25°C
1.8 m
0.003 mg P/l
0.05 mg P/l
12 yg/1
320 g C/m2/yr
0 kg P/yr
2800 kg P/yr
0.1 g P/m2/yr
(0.2)f
Spring Overturn
Mean Values
Secchi Depth (m)
Total Phosphorus
(mg P/l)
Chlorophyll a (yg/1)
PhotosynthetTc Rate
(g C/m2/day)
1969
1.4
0.05
23
2 .5
1973 1972
1.7
0 .04 . 0.08
15
1.9
1973
0 .04
-
(continued)
426
-------
DATA SUMMARY FOR LOWER LAKE MINNETONKA (MINN.)"- (continued)
Investigator-Indicated Comments
aTrophic status as of 1973. Sewage diversion was begun during win-
ter of 1971-1972, eliminating the point source phosphorus input.
Prior to sewage diversion, lake was considered eutrophic. Lower
Lake Minnetonka is still considered eutrophic in 1973. However,
the decreasing nutrient and chlorophyll concentrations and
primary productivity and increasing Secchi depth observed in
1973-1974, relative to the 1969 values, indicate the lake to
be changing to a less fertile trophic condition.
Does not include water body surface area.
c • •
Watershed area and hydraulic residence time data is for entire
lake. All other data is only for Lower Lake Minnetonka. It was
not possible to calculate hydraulic retention times for individual
basins. Thus, the hydraulic residence time for the whole lake was
used in all calculations.
Data obtained from samples obtained during the 210-day ice-free
period, on ten dates in 1969 and seven dates in 1973, at five
meter depth intervals from the surface to the bottom of the lake.
Q
Data obtained from samples incubated at 0, 0.5, 1.0, 2.0, 3.0 and
5.0 meter depths on eight dates between April 25-November 11,
1969 and 1973.
Data in parentheses represents data received by these reviewers
from the principal investigator subsequent to completion of this
report. Examination of the revised data indicated no significant
changes in the overall conclusions concerning Lake Minnetonka.
Dash (-) indicates no data available.
*
Data taken from Megard (1975) and personal communication
427
-------
POTOMAC ESTUARY (MARYLAND, VIRGINIA)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(ESTUARY)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth0
Mean Dissolved Phosphorus0
Mean Total Phosphorus0
Mean Inorganic Nitrogen0
as N)
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Ultra-eutrophic in 1966-1970
3.8 x 1010 m2
Upper Reach Middle Reach
Lower Reach
5.7 x 10'
4.8
0.04
70-110
200-500
0.4-0.8
0.2-0.8
0.3-1.2
1.8-3.2
30-150
2.1 x
5.1
7.0 x 108 m2
7.2m
0.18 0.85 yr
60-85 65-85 mg/1 as CaCO.
600-17,000
0.5-1.3
0.08-0.15 0.01-0.04 mg P/l
0.01-0.75 0.03-0.06 mg P/l
0.15-0.33 0.05-0.15 mg N/l
17,000-26,000
yrrmo s / cm@ 2 5° C
1.0-2.3 m
30-100
10-20 yg/1
4.0 x 10 kg P/yr
8.8 x 105 kg P/yr
85 8 _._ _..
(For total estuary = 5 g P/m^/yr)
9.9 x 106 kg N/yr
6.6 x 106 kg N/yr
1.2 g P/m /yr
288 32 25
(For total estuary - 17.2 g
Investigator-Indicated Comments
Lower estuary is saline.
Dominant algae is Anacystis.
The dissolved oxygen content is low in the upper and lower reach.
2
The
upper and middle reaches become nitrogen-limited with respect to aquatic
plant nutrient requirements during the summer months .
Does not include water body surface area.
The estuary has been divided into three separate regions (reaches).
Each reach is treated separately.
(continued)
428
-------
DATA SUMMARY FOR POTOMAC ESTUARY (MARYLAND, VIRGINIA)*- (continued)
Q
June through September values; data based on samples obtained at
monthly intervals between 1966-1969, and weekly intervals between
1969-1970, at the top and bottom sampling depths, from sampling
stations at five mile intervals in the upper estuary and larger
intervals in the lower estuary.
Dash (-) No data available.
*
Data taken from Jaworski (1975) and personal communication
(Table 3).
429
-------
LAKE REDSTONE (WISC.)"
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(IMPOUNDMENT)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depthb
Mean Dissolved Phosphorus
V
Mean Total Phosphorus
b
Mean Inorganic Nitrogen
(NH4+N03+N02 as N)
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Summer Mean Epilimnetic Volumes
Total Phosphorus
Dissolved Phosphorus
Inorganic Nitrogen
Eutrophic in 1972-1973
7.7 x 107 m2
2.5 x 106 m2
4.3m
0.7-1.0 yr
125 mg/1 as CaCO
260 ymhos/cm @ 25°C
1.6 m
0.008C mg P/l
0.03° mg P/l
0.80° mg N/l
12.8 yg/1 (first two meters
of water column)
0 kg P/yr
3630-4230 kg P/yr
1.44-1.68 g P/m2/yr
0 kg N/yr
45,400 kg N/yr
18.1 g N/m2/yr
0.11 mg P/l
0.008 mg P/l
0.30 mg N/l
b
Investigator-Indicated Comments
""Does not include water body surface area.
Data based on samples obtained at six week intervals at either
one or two meter depth intervals in the deepest part of the
impoundment.
c
Average winter concentration.
Dash (-) No data available.
Data taken from Piwoni and Lee (1975) and personal communication
(Table 3).
-------
LAKE SALLIE (MINN.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorgan_ic Nitrogen
' as N)
Mean Chlorophyll a_
Annual Primary Productivity
c
Phosphorus Loading :
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading0 :
Point Source
Non-Point Source
Surface Area Loading
Eutrophic in 1968-1972
9 2
1.5 x 10 m
5.3 x 106 m2
6.4m
1.1-1.8 yr
162 mg/1 as CaCO
O
280-360 ymhos/cm @ 25 C
0.13 mg P/l
0.35 mg P/l
0.44 mg N/l
7060-20,080 kg P/yr
1030-1970 kg P/yr
1.5-4.2 g P/m2/yr
5590-11,360 kg N/yr
4195-9086 kg N/yr
2.8-3.0 g N/m2/yr
Growing Season
(May-September)
Mean Epilimnetic Values
Total Phosphorus (mg P/l)
Dissolved Phosphorus (mg P/l)
Inorganic Nitrogen (mg N/l)
Primary Productivity
(mg C/m^/Langley/hr)
/I)
)
1972
0.4
0. 04
0.15
1973
0.65
0.20
0.18
Spring Overturn
Mean Values
1.12
0. 26
0.70
9.6
9.6
(continued)
431
-------
DATA SUMMARY FOR LAKE SALLIE (MINN.)''- (continued)
Investigator-Indicated Comments
Hypolimnion does not persist over a growing season
Does not include water body surface area.
Data based on samples obtained at weekly intervals during 1972-
1973 at 22 stations located at the lake inlet and outlet, on
a transect down the middle of the lake, and around the shore line
C1968-1972 data.
Dash (-) No data available.
it
Data taken from Neel (1975) and personal communication
(Table 3).
M-32
-------
SAMMAMISH (WASH.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus0
Mean Total Phosphorus0
Mean_Inorganic Nitrogen0
(N03+N02 as N)
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Mesotrophic in 1970-1975
2.7 x 108 m2
7 2
2.0 x 10 m
18 m
1. 8 yr
33 mg/1 as CaCOQ
O
94 umhos/cm @ 25 C
3.3m
0.006 mg P/l
0.03 mg P/l
0.18 mg N/l
5 yg/1
238 g C/m2/yr
500 kg P/yr
12,500 kg P/yr
2
0.7 g P/m /yr
0 kg N/yr
258,000 kg N/yr
13.0 g N/m /yr
Non-Point Source
Surface Area Loading
Growing Season
(March - August)
Mean Epilimnetic Values
Secchi Depth (m) 3.3
Total Phosphorus (mg P/l) 0.03
Dissolved Phosphorus (mg P/l) 0.004
Inorganic Nitrogen (mg N/l) 0.24
Chlorophyll a (yg/1) 6
2
Primary Productivity (g C/m /day) Q.7
2
Growing Season Hypolimnetic Oxygen Depletion Rate = 0.05 mg/cm /day
(constant from year to year)
(continued)
433
Winter (Dec.-Feb.)
Mean Values
(photic zone)
3.0
0.03
0.013
-------
s't
DATA SUMMARY FOR SAMMAMISH (WASH.) - (continued)
Investigator-Indicated Comments
Partial wastewater input diversion («30% of total phosphorus
input) begun in 1968.
Does not include water body surface area.
/-»
Data based on photic zone (7.3 m) measurements.
Post-sewage diversion nutrient loadings. Pre-sewage diversions
are as follows: total phosphorus = 20,000 g/yr = 1 g/m2/yr
total nitrogen = 243,000 kg/yr = 12.3 g/m2/yr
Dash (-) No data available.
*
Data taken from Welch et al. (1975) and personal communication
(Table 3).
434
-------
SHAGAWA (MINN.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth0
Mean Dissolved Phosphorus1"
Mean Total Phosphorus0
Mean Inorganic Nitrogen
(NH^+NO^+NO" as N)
Mean Chlorophyll a°
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Eutrophic
2.7 x 108 m
in 1972
2
d
9.2 x 106 m2
5.7m
0. 8 yr
22 (fall circulation) mg/1 as CaC03
60 (fall circulation) ymhos/cm @ 25 C
2.3 (ice-free period) m
0.021 mg P/l
0.06 mg P/l
0.160 mg N/l
15 (24)d yg/1
220 g C/m2/yr
5100 kg P/yr
1150 kg P/yr
0.7 g P/m2/yr
20,000 kg N/yr
52 ,000 kg N/yr
7.8 g N/m2/yr
Growing Season
(May-September)
Mean Epilimnetic Values
Spring Overturn
Mean Values
Secchi Depth (m) 1.7 2.1
Total Phosphorus (mg P/l) 0.05 0.05
Dissolved Phosphorus (mg P/l) 0.005 0.024
Inorganic Nitrogen (mg N/l) 0.04 0.20
Chlorophyll a (yg/1) 31 13.0
1972 Growing Season Hypolimnetic Oxygen Depletion Rate =1.0 mg/1/week
(assumed constant growing season hypolimnion volume)
(continued)
435
-------
DATA SUMMARY FOR SHAGAWA (MINN.)*- (continued)
Investigator-Indicated Comments
Prior to completion of tertiary waste treatment plant for input
wastewater discharges in 1972-1973.
Does not include water body surface area.
Q
Data based on samples obtained from three stations at 1.5 m
depth intervals from surface to bottom
Ice-free period averages.
Dash (-) No data available.
A
Data taken from Malueg et al. (1975) and personal communication
(Table 3).
-------
LAKE STEWART (WISC.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(IMPOUNDMENT)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NHL| +N0g +N0o as N)
Mean Chlorophyll ab
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Summer Mean Epilimnetic Values
Total Phosphorus
Dissolved Phosphorus
Inorganic Nitrogen
Eutrophic in 1972-1973
2.1 x 106 m2
2.5 x 104 m2
1.9m
0.08 yr
213 mg/1 as CaCO.
O
540 ymhos/cm @ 25°C
1.4 m
0.001° mg P/l
0.04° mg P/l
2.26° mg N/l
12.3 yg/1 (first two meters of
water column)
0 kg P/yr
121-202 kg P/yr
4. 82-8.05 g P/m2/yr
0 kg N/yr
1850 kg N/yr
73.6 g N/m2/yr
0.08 mg P/l
0.008 mg P/l
0.86 mg N/l
Investigator-Indicated Comments
Does not include water body surface area.
Data based on samples obtained at six week intervals at either
one or two meter depth intervals in the deepest part of the im-
poundment .
c
Average winter concentration.
tDash (-) No data available.
Data taken from Piwoni and Lee (1975) and personal communication
(Table 3).
437
-------
TAHOE (CALIF., NEVADA)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
N)
b
(NH4+N03+N02 as
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Growing Season (May-September)
Mean Epilimnetic Values:
Secchi Depth (m)
Total Phosphorus (mg P/l)
Dissolved Phosphorus (mg P/l)
Inorganic Nitrogen (mg N/l)
Chlorophyll a (yg/1)
2
Primary Productivity (g C/m /day)
Ultra-oligotrophic in 1973-1974
9 ?
1.3 x 10 m
5.0 x 108 m2
313 m
700 yr
43 mg/1 as CaCO
O
92 umhos/cm @ 25°C
28.3m
<0.005 mg P/l (non-detectable)
0.003 mg P/l
0.02 mg N/l
0.3 yg/1 (euphotic zone)
2
5.6 g C/m /yr
0 kg P/yr
23,400 kg P/yr
0.05 g P/m2/yr
0 kg N/yr
257,300 kg N/yr
0. 52 g N/m2/yr
1973
1974
22.5
0.003
<0.003
0.006
-
0. 05
24.3
0.003
<0.003
0.003
0.2
0. 03
(6 year euphotic zone average =
0.15)
(continued)
438
-------
*
DATA SUMMARY FOR TAHOE (CALIF., NEVADA) - (continued)
Investigator-Indicated Comments
Does not include water body surface area.
Data based on samples obtained at monthly intervals during
1973-1974, at the deep midlake stations from twelve depths
between 0 and 400 meters. The chlorophyll value is only for
1974.
Q
Six-year average value
Data based on samples obtained weekly to tri-monthly between
August, 1967 and December, 1971 at 13 depths between 0 and 105 m
(euphotic zone).
Dash (-) No data available.
ft
Data taken from Goldman (1975) and personal communication
(Table 3).
439
-------
EAST TWIN LAKE (OHIO)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area"
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NH4+N03+N07 as N)
r\
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Eutrophic in 1972-1974
3.3 x 106 m2
2.7 x 105 m2
5.0m
1971
-
~
-
2.1
0. 05
0. 09
1. 34
1972
0 .8
~
374
1.6
0.03
0. 08
0. 58
1973
0.9
105
380
2. 3
0. 04
0. 08
0. 84
1974°
0 .5 yr
105 mg/1 as CaC03
366 ymhos/cm
@ 25oC
1.9m
0.02 mg P/l
0.08 mg P/l
mg N/l
21
26
22
Ug/1
4748 g C/m2/yr
0 kg P/yr
- 192 (18lfl39(127)185(220)kg P/yr
- 0.7 (0.7^0. 5(0. 5)0. 7(0. 8) g P/m2/vr
0
8340
31.4
0
5190
19.3
- kg N/yr
- kg N/yr
- g N/m2/yr
Investigator Indicated Comments
1Sewage diversion begun in late 1971-1972. Lake was considered
early eutrophic prior to sewage diversion. Lake is still con-
sidered eutrophic at present time. However, the changing char-
acter of the plankton populations indicate the lake to be changing
toward a mesotrophic state.
East Twin Lake and West Twin Lake are connected by a tributary and
share the same watershed drainage area. Drainage area does not
include water body surface area.
•»
'Experienced sewage leak from West Twin Lake- into East Twin Lake
in 1974.
(continued)
440
-------
DATA SUMMARY FOR EAST TWIN LAKE (OHIO)" - (continued)
Data based on samples obtained from the deepest point in each
lake, generally weekly from late spring - early fall, and less
frequently the rest of the year, at 0.1, 2, 4, 7, and 10 meters
from 1971-1974.
Average of 6 measurements made between June 27, 1974 - August 9,
1974. An in situ measurement technique used because of diffi-
culty of estimating primary productivity of extensive macrophyte
production.
Summer season mean epilimnetic nutrient concentrations given in
Cooke et aJL. (1975)
Dash (-) No data available.
All data in parentheses represents data received by these reviewers
from the principal investigators subsequent to completion of
this report. The original data supplied by the investigator
was used in all figures in this report. Examination of the
revised data indicated no significant changes in the overall
conclusions concerning East Twin Lake.
it
Data taken from Cooke et a1. (1975) and personal communication
(Table 3).
441
-------
WEST TWIN LAKE (OHIO)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depthc
c
Mean Dissolved Phosphorus
Mean Total Phosphorus
c
Mean Inorganic Nitrogen
(NH4+N03+NO~ as N)
^ Q
Mean Chlorophyll a
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Eutrophic in 1974
3.3 x 106 m2
3.4 x 105 m2
4. 34 m
1971 1972 1973 1974
-
1
.6
1
.8
110
0
0
1
1.
.0
7
7
.15
.9
3
411
2.2
0
0
0
•
•
.
06
12
79
0
0
0
4
2
.
•
•
09
.8
06
11
83
1.0
106
380
2.3
0.04
0.10
-
yr
mg/1 as
ymhos/cm
in 25°C
mg P/l
mg P/l
mg N/l
CaCO
27 40 23 28 ug/1
576d g C/m2/yr
0 0 0 kg P/yr
- 118(143^103(61)91(107) kg P/yr
- 0.4(0.4)0.3 (0.2)0.3(0.3')gP/m2/yr
0
5457
16
0
5094
15
kg N/yr
g N/m /yr
Investigator-Indicated Comments
b
Sewage diversion begun in late 1971-1972. Lake was considered
eutrophic prior to sewage diversion. However, lake is considered
mesotrophic at the present time because of its changing plankton
characteristics.
East Twin and West Twin Lake are connected by a tributary and
share the same watershed drainage area. Drainage area does not
include water body surface area.
-i
"Data based on samples obtained from the deepest point in each lake,
generally weekly from late spring-early fall, and less frequently
the rest of the year at 0.1, 2, 4, 7 and 10 meters from 1971-1974.
(continued)
442
-------
DATA SUMMARY FOR WEST TWIN LAKE (OHIO)"- (continued)
All data in parentheses represents data received by these re-
viewers from the principal investigator subsequent to completion
of this report. The original data supplied by the investigator
was used in all figures in this report. Examination of the re-
vised data indicated no significant changes in the overall
conclusions concerning West Twin Lake.
Summer season mean epilimnetic nutrient concentrations given in
Cooke et al. (1975).
Dash (-) No data available.
*
Data taken from Cooke et al. (1975) and personal communication
(Table 3).
-------
TWIN VALLEY LAKE (WISC.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(IMPOUNDMENT)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NHiJ + NOs+NO' as N)
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Summer Mean Epilimnetic Values
Total Phosphorus
Dissolved Phosphorus
Inorganic Nitrogen
Eutrophic in 1972-1973
3.1 x 107 m2
6.1 x ID5 m2
3.8m
0.4-0.5 yr
175 mg/1 as CaC03
370 ymhos/cm @ 25°C
1.5 m
0.019° mg P/l
0.07° mg P/l
0.51° mg P/l
19 ug/1 (first two meters of
water column)
0 kg P/yr
1090-1250 kg P/yr
1.74-2.05 g P/m2/yr
0 kg N/yr
10,500 kg N/yr
17.4 g N/m2/yr
0.06 mg P/l
0.01 mg P/l
0.23 mg N/l
Investigator-Indicated Comments
Does not include water body surface area".
Data based on samples obtained at six week intervals, at
either one or two meter depth intervals,- in the deepest
part of the impoundment.
Q
Average winter concentrations.
Dash (-) No data available.
&
Data taken from Piwoni and Lee (1975) and personal communication
(Table 3).
444
-------
ft
LAKE VIRGINIA (WISC.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(SEEPAGE IMPOUNDMENT)
b
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
CNH4+N03+N02 as N)
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Summer Mean Epilimnetic Values:
Total Phosphorus
Dissolved Phosphorus
Inorganic Nitrogen
Eutrophic in 1972-1973
c o
6.5x10 m
1.8 x 105 m2
1.7m
0.9-2.8 yr
64 mg/1 as CaCO
230 ymhos/cm @ 25°C
1.2m
0.004° mg P/l
0.02C mg P/l
0.22° mg P/l
29.0 yg/1 (first two meters
of water column)
0 kg P/yr
210-270 kg P/yr
1.15-1.48 g P/m2/yr
0 kg N/yr
3300 kg N/yr
18.3 g N/m2/yr
0.15 mg P/l
0.025 mg P/l
0.18 mg N/l
Investigator-Indicated Comments
Does not include water body surface area.
Data based on samples obtained at six week intervals at either
one or two meter depth intervals in the deepest part of the
impoundment.
Q
Average winter concentration.
Dash (-) No data available.
ft
Data taken from Piwoni and Lee (1975) and personal communication
(Table 3).
-------
WALDO (ORE.)'
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
b
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus'
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NH4+N03+NO~ as N)
Mean Chlorophyll a_
Annual Primary Productivity6
e
Phosphorus Loading :
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading :
Point Source
Non-Point Source
Surface Area Loading
Ultra-Oligotrophic in 1974
7.9 x 10? m2
2.7 x 107 m2
36 m
21 yr
1.8 mg/1 as CaC03
3.4 ymhos/cm @ 25°C
28 m
<0.005 mg P/l
<0.005 mg P/l
<0.010 mg N/l
0.32
0.001-0.003 g C/m2/dayd
0 kg P/yr
458 kg P/yr
0.017 g P/m2/yr
0 kg N/yr
9020 kg N/yr
0.33 g N/m2/yr
b
c
Investigator-Indicated Comments
Does not include water body surface area.
Data based on samples obtained from nine stations each August
from 1970 to 1974, at 20 meter depth intervals. Significant
differences between epilimnetic and hypolimnetic values do not
appear to exist.
Average of summer measurements for 1969, 1970, and 1974.
Summer 1970 value.
Q
Based on average of four indirect calculation methods.
(see Powers et al., 1975)
Based on average of two indirect calculation methods.
(see Powers ejt al. , 1975)
*Data taken from Powers et_ al. (1975) and personal communication
(Table 3).
-------
WASHINGTON (WASH.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area*5
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
(NHj+N03+NO~ as N)
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrop.en Loading:
Point Source
Non-Point Source l,
Surface Area Loading
Growing Season (May-Sept.)
Mean Epilimnetic Values:
Total Phosphorus (mg P/l)
Dissolved Phosphorus (mg P/l
Inorganic Nitrogen (mg N/l)
Chlorophyll a (jig/l)
Mesotrophica in 1974
Q 9
1.6 x 10 m
8.8 x 107 m2
33 m
2 .4 yr
45 mg/1 as CaCO_
J,
81 ymhos/cm @ 25
1S33
-
0.003
0.016
0.007
_
—
1957°
1957
2.2
0.002
0.024
0.12
12
—
1964°
1963-4
1.2
0.030
0.066
0.24
20
766
1971d
1971
3.5
0.006
0.018
0.18
6
354
1974d
1974
3.8m
(3.5 m)e
- mg P/l
- mg N/l
(l4)e
- g C/m2/
yr
57,100 103,900 0
60,400 98,500 37,600
1.2 2.3 0.43
201,700 271,000 0
487,200 418,200 401,600
19.2 7.8 4.6
1933 1957
0.013 0.022
) 0.001 0.002
0.037 0.042
15
0 kg P/yr
41,300 kg P/yr
0.47 g P/m2/yr
0 kg N/yr
386,900 kg N/yr
4.4 g N/m2/yr
1963 1971
0.060 0.014
0.010 0.005
0.106 0.067
29 9
(continued)
447
-------
DATA SUMMARY FOR WASHINGTON (WASH.) - (continued)
Investigator-Indicated Comments
Sewage diversion project begun in 1963 and completed in 1968.
Lake Washington was considered eutrophic prior to 1963. However,
the nutrient and chlorophyll concentrations and primary pro-
ductivity have decreased dramatically since 1963, indicating
a much lower fertility as a result of the sewage diversion
project. Lake Washington is considered mesotrophic at the
present time.
Does not include water body surface area.
c ....
Maximum estimated input, including septic tank drainage. However,
part of this would already have been measured in the stream in-
puts, and therefore this estimate may be slightly higher than the
actual input phosphorus loading.
Post-sewage diversion loading of the two major outlets; does
not include storm water drainage overflow, which is not considered
a major nutrient input source.
Data in parentheses represents data received by these reviewers
from the principal investigators subsequent to completion of this
report. Examination of the data indicates no significant changes
in the overall conclusions concerning the water body.
Dash (-) No data available.
"Data taken from Edmondson (1975a) and personal communication
(Table 3).
-------
WEIR (FLA.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
V'ater Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
b
Mean Inorganic Nitrogen
(NH^ + NO^+NO" as N)
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
ICon-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
May-September Mean Epilimnetic
Values:
Secchi Depth
Total Phosphorus
Dissolved Phosphorus
Inorganic Nitrogen
Chlorophyll a
Primary Productivity
Mesotrophic in 1974-75
7 9
4.6 x 10 m
2.4 x 107 m2
6.3m
4 . 2 yr
11.5 mg/1 as CaCO
133 ymhos/cm @ 25 C
1.9 m
0.025 (0.006) mg P/l
0.08 (0.02)C mg P/l
0.07 (0.20)° mg N/l
8 (6)^ yg/1
2
36 g C/m /yr
0 kg P/yr
3290 kg P/yr
0.14 g P/m2/yr
0 kg N/yr
61,920 kg N/yr
2.6 g N/m2/yr
1.9m
0.08 mg P/l
0.022 mg P/l
0.04 mg N/l
4 yg/1
0.4 g C/m2/day
(continued)
449
-------
DATA SUMMAFY FOR WEIF (FLA.) - (continued)
Investigator-Indicated Comments
Does not include water body surface area.
Data based on samples obtained at biweekly intervals at three
stations at the surface, 1m, 3m, 5m, and at station 1, 7m depths,
from 6/20/74 to 1/19/75.
Q
1969-70 average values.
*Data taken from Brezonik and Messer (1975) and personal communication
(Table 3).
450
-------
WINGRA (WISC.)
DATA SUMMARY FOR US OECD EUTROPHICATION PROJECT
(LAKE)
Trophic State
Drainage Area
Water Body Surface Area
Mean Depth
Hydraulic Residence Time
Mean Alkalinity
Mean Conductivity
Mean Secchi Depth
Mean Dissolved Phosphorus
Mean Total Phosphorus
Mean Inorganic Nitrogen
as N)
Mean Chlorophyll a_
Annual Primary Productivity
Phosphorus Loading:
Point Source
Non-Point Source
Surface Area Loading
Nitrogen Loading:
Point Source
Non-Point Source
Surface Area Loading
Growing Season (May-September)
Mean Epilimnetic Values:
Total Phosphorus
Dissolved Phosphorus
Inorganic Nitrogen
Primary Productivity
Eutrophic in 1970-1971
7 2
1.4 x 10 m
1.4 x 106 m2
2.4m
0. 4 yr
153 mg/1 as CaC00
1.3m
0.02 mg P/l
0.07 mg P/l
0.31 mg N/l
870 g C/m /yr (phytoplankton
productivity)
0 kg P/yr
1200 kg P/yr
0.9 g P/m2/yr
0 kg N/yr
7200 kg N/yr
5.14 g N/m2/yr
0.08 mg P/l
0.06 mg P/l
1.0 mg N/l
2
4.6 g C/m /day
Investigator-Indicated Comments
Lake has extensive littoral zone and exhibits large amount of
macrophyte growth.
(continued)
451
-------
DATA SUMMARY FOR WINGRA (WISC.) - (continued)
Does not include water body surface area.
Data based on samples obtained at weekly intervals during
1970-1971, at one and two meters, from four open lake and
four littoral zone stations.
Dash (-) No data available.
Data taken from Rast and Lee (1975) and personal communication
(Table 3).
452
-------
GLOSSARY
2
A, Watershed area (L )
a
2
A Water body surface area (L )
L Areal loading (ML'2?'1)
L Critical loading (ML'2?'1)
L (P) Permissible ("critical") total phosphorus loading
(ML-2T-1)
-2 -1
L(N) Total nitrogen loading (ML T )
L(P) Total phosphorus loading (ML'2?'1)
_3
L(P)/q Influent total phosphorus concentration (ML )
-3 -1 -
£(P) Volumnar total phosphorus loading (ML T ) = L(P)/z
MDR Meteoric discharge rate (LT~ )
_ q
[P] S [P]X In-lake total phosphorus concentration (ML )
_ q
[P] Influent total phosphorus concentration (ML ) =
L(P)/q
o
_ q
[P]. Inflow total phosphorus concentration (ML )
_ q
[P] Outflow total phosphorus concentration (ML )
[P] P Critical total phosphorus concentration at spring
overturn (ML~3)
r-r.-, summer „ • •, •> ^ . -, -^ -. ^ •
IP], Summer mean in-lake total phosphorus concentration
X (ML-3)
[P], Total phosphorus concentration at time t (ML~ )
_ o
[P], Total phosphorus concentration at time 0 (ML )
o _3
[P] Steady state total phosphorus concentration (ML~ )
453
-------
Q Annual inflow or outflow volume (L )
3
q. Inflow volume (L )
2
q Outflow volume (L )
o
q Hydraulic loading (LT~ ) = Z/T = areal water load
(Q/Ao)
R Retention coefficient
R • Nitrogen residence time (T)
R Phosphorus residence time (T)
P
l-R(P) Fraction of phosphorus input not retained in sediment
T Phosphorus residence time (T)
3
V Water body volume (L )
v Apparent settling velocity of total phosphorus
(LT-1) = « v1
v. Flow rate in j th tributary (L3T~1)
v-'- Settling velocity of settleable particulate phosphor-
us (LT-1)
z Mean depth (L) = V/A
c o
<* Fraction of total phosphorus represented by settle-
able particulate phosphorus
p Flushing rate (T )
p Hydraulic flushing rate (T~ )
TT Phosphorus residence time relative to hydraulic
residence time (TT~^) = f /T
p oo
a ' Sedimentation rate coefficient (T )
a Phosphorus sedimentation rate coefficient (T~ )
T Hydraulic residence time (T)
454
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before -ompleting)
1. REPORT NO.
EPA-6QO/3~78-nna
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
SUMMARY ANALYSIS OF THE NORTH AMERICAN (U.S. PORTION)
OECD EUTROPHICATION PROJECT: Nutrient Loading—Lake
Response Relationships and Trophic State Indices
DATE
1978
6. PERF-,RM)NG ORGANIZATION CODE
7. AUTHOR(S)
Walter Rast and G. Fred Lee
8. PERFORMIIG ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Center for Environmental Studies
The University of Texas at Dallas
Richardson, TX 75Q80
10. PROGRAM ELEME.T No
1BA608
11. CONTRACT/GRANT NO.~
R-803356-01-0
R-803356-01-3
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research Laboratory - Corvallis, OR
U.S. Environmental Protection Agency
200 SW 35th St., Corvallis, OR 97330
13. TYPE OF REPORT AND PERIOD
Final - July 1974/NovemU
14. SPONSORING AGENCY CODE
EPA/600/02
15. SUPPLEMENTARY NOTES
Companion document to EPA-6'00/3-77-086:NORTH AMERICAN PROJECT - A Study of U.S.
I'/ater Bodies
16. ABSTRACT
This report summarizes and critically analyses nutrient load-lake response relation-
ships for 38 U.S. water bodies which have been intensively studied by 20 scientists
participating in the OECD Eutrophication Program.
It was determined that the Vollenweider nutrient load relationship involving mean
depth, hydraulic residence time and phosphorus load correlated well with the trophic
states assigned by the individual investigators.
A good correlation was also found between phosphorus loading, normalized as to hydrau-
lic residence time and mean depth, and the average chlorophyll and water clarity (as
neasured by Secchi depth).
The relationships developed in this study can be used to predict the improvement in
water quality that will result from a change in the phospohrus load to a water body
for which phosphorus is the key chemical element limiting planktonic algal growth.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
eutrophication
lakes
nutrients
phosphorus
nitrogen
loading
05B
05C
18. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
478
20 SECURITY CLASS (This page)
22. PRICE
Unclassified
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
455
rU S GOVERNMENT PRINTING OFFICE 1978—799-716/74 REGION 10
------- |