United States
Environmental Protection
Agency
Environmental Research
Laboratory
Corvallis OR 97330
EPA 600 3-79-046
April 1979
Research and Development
&EPA
Watershed and
Point Source
Enrichment and
Lake Trophic
State Index
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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-600/3-79-046
April 1979
WATERSHED AND POINT SOURCE ENRICHMENT
AND LAKE TROPHIC STATE INDEX
by
Joe K. Neel
Department of Biology
The University of North Dakota
Grand Forks, North Dakota 58202
Project No. R800490
Project Officer
Robert M. Brice
Marine and Freshwater Ecology Branch
Corvallis Environmental Research Laboratory
Corvallis, Oregon 97330
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. 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 contents necessarily
reflect the views and policies of the U.S. Environmental Protection Agency,
nor does mention of trade names or commercial products constitute endorse-
ment or recommendation for use.
11
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FOREWORD
Effective regulatory and enforcement actions by the Environmental
Protection Agency would be virtually impossible without sound scientific
data on pollutants and their impact on environmental 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, freshwater, and marine ecosystems;
the behavior, effects and control of pollutants in lake systems; and the
development of predictive models on the movement of pollutants in the
biosphere.
This study shows that diffuse sources of nutrients within a watershed may
be as important as a municipal wastewater treatment plant effluent in affect-
ing the trophic quality of a lake.
James C. McCarty
Acting Director, CERL
iii
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ABSTRACT
Water in the permeable soils of the upper Pelican River watershed,
Minnesota, requires slightly more than a year to move generally out of the
phreatic zone into surface channels and basins. Its nutrient content seems
mainly responsible for the load borne in surface Waters above entrance of a
wastewater effluent, and groundwater changes have been followed a year later
by similar ones in surface water. In 1975 P load from non-point sources
markedly exceeded that from the wastewater effluent. Nutrients in ground-
water are assumed to result from soil surface application, but only quantities
supplied by precipitation have been measured. The most noxious conditions in
surface waters have been occasioned by heterocystous blue-green phytoplankters,
but the greatest plant mass has been produced by rooted and attached vegeta-
tion. Blue-green algae have not been predominant in some water bodies and
only intermittently in most others. Their occurrence appeared controlled by
environmental conditions other than nutrient loading in the ranges encountered
here. Groundwater seepage into these lakes contributed more nutrients than
precipitation, but the latter supplied what may be significant amounts to
watershed soils. A trophic state index based on change in Mg/Ca quotient
relative to water residence time has reliably depicted relative total produc-
tivity levels in 6 lakes or ponds, and its general applicability, at least to
natural lakes, now appears likely.
This report was submitted in fulfillment of Grant R800490 by the Univer-
sity of North Dakota under sponsorship of the U.S. Environmental Protection
Agency. This report covers the period January 1, 1973, to December 5, 1975,
and work was completed as of August 18, 1976.
IV
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CONTENTS
Foreword .................................
Abstract ................................. iv
Figures ................................. v:Ji
Tables .................................. viii
Acknowledgments ............................. ix
1. Introduction ......................... 1
2. Conclusions ......................... 2
3. Recommendations ....................... 6
4. Study Area .......................... 7
Pelican River Watershed ................. 7
Miscellaneous lake features ............ 10
5. Methods ........................... ll
Sampling ........................
Analysis ........................
Miscellaneous ......................
6. Results and Discussion ....................
Climatological data .......... ......... 13
Water quality ...................... -"-->
Watershed nutrients ................ 13
1 ~\
Surface waters ................
Concentration ..............
Loads .................. 32
Groundwater ..................
General groundwater features .......
Nutrient concentration ..........
Ground and surface water .........
Groundwater movement ...........
Oxygen and hydrogen sulfide .......
Groundwater seepage into lakes ...........
Nutrient concentration ............ . 1
q. j^
Water and nutrient loads ...... .....
Precipitation ...................... '^
Nutrient concentration ...............
/ ~~)
Nutrient loads ...................
Lake Conditions .....................
Lake St. Clair
Bottom materials
Nutrient content ............. "*
l> l\
Water chemistry ................
Primary production ...............
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Lake Sallie 48
Thermal stratification 50
Bottom materials 50
Nutrient loads 52
Weed growth 53
Water chemistry 55
PH 55
Oxygen 55
Primary production 59
Watershed phytoplankton 59
Trophic state index 60
Development 60
Relationship to nutrient loading and local ....
conditions • • "°
Relationship to varying hardness ^7
General considerations 67
References 70
Appendix 72
VI
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FIGURES
Number Page_
1 Upper Pelican River watershed, Minnesota 8
2 Details of wastewater treatment area 9
3 Total P and SRP variation, 1974 15
4 Total P and SRP variation, 1975 20
5 Percentages of total P formed by SRP 26
6 Ammonia, nitrite, and nitrate nitrogen variation, Station A,
1975 29
7 Ammonia, nitrite, and nitrate nitrogen variation, Station B,
1975 : 30
8 Ammonia, nitrite, and nitrate nitrogen variation, Station F,
1975 31
9 Total N variation, Stations A, B, and F, 1975 33
10 Locations of ground-water sampling sites 35
11 Mean groundwater level elevations in sampling wells 39
12 Groundwater contours and indicated flow paths 40
13 Hydrographic map of Lake St. Clair £5
14 Oxygen and pH variation, Lake St. Clair, 1975
15 Mean C fixed per hour, 8:30 a.m. - 2:30 p.m. CDT, Lakes
Sallie and St. Clair 47
16 Hydrographic map of Lake Sallie 49
17 Bottom sediments, Lake Sallie 51
18 Weed harvesting areas, Lake Sallie 54
19 pH and oxygen variation, Lake Sallie, 1973 56
20 pH and oxygen variation. Lake Sallie, 1974 57
21 pH and oxygen variation, Lake Sallie, 1975 58
22 Mg/Ca quotient variation, aeration and stabilization ponds, 1975. 61
23 Mg/Ca quotient variation, stabilization pond and Lake St.
Clair, 1975 62
24 Mg/Ca quotient variation, Detroit Lake inlet and outlet, 1975 . . 63
25 Mg/Ca quotient variation, Lake Sallie inlet and outlet, 1975. . . 64
vii
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TABLES
Number Page
1 Magnitude features of lakes and ponds 77
2 Discharges at selected points in the upper Pelican River
watershed 78
3 Individual well features 79
4 Temperature and precipitation records, Detroit Lakes, 1973-75. . 82
5 Pelican River discharge near Fergus Falls, Minnesota,
water years 1973-75 83
6 Mean annual nutrient concentrations, mg/1, watershed stations. . 84
7 Mean monthly concentrations total P, mg/1 85
8 Mean monthly concentrations total N, mg/1 87
9 Total phosphorus loads at watershed stations (metric tons) ... 34
10 Total nitrogen loads at watershed stations (metric tons) .... 36
11 Mean nutrient concentrations in individual wells (top and
bottom) and in groundwater sub-areas 89
12 Mean nutrient concentrations at top and bottom of groundwater
in individual wells 90
13 Mean calcium and magnesium concentrations, groundwater, mg/1
as CaCO-j 93
14 Mean alkalinities, groundwater, mg/1 as CaCO^ 94
15 Oxygen ranges at groundwater sampling sites, April, 1974 -
August, 1975 (mg/1) 95
16 Variation in seepage volume and P and N loads (quantities/
hectare/day) 96
17 Nutrient concentration in rain, daily means, mg/1 97
18 Precipitation and nutrients falling on Lake Sallie 98
19 Nutrients contributed by rain to lake surfaces (kilograms) ... 99
20 Dates and volumes of hypolimnia appearing in Lake Sallie .... 100
21 Phytoplankton concentration at watershed stations, May -
November, 1975 (nos. per ml) 101
vnx
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ACKNOWLEDGMENTS
Lakeside (Lake Sallie) laboratory and storage facilities were provided by
the Minnesota Department of Natural Resources and local cooperation by
Manferd Branby, Coleman Nordhausen, Donald Olson, and Walter Wiese is grate-
fully acknowledged.
The Pelican River Watershed District and the City of Detroit Lakes contin-
ued the fine cooperation they began with Project No. 16010 DFI in 1968, and
special recognition is again due Winston C. Larson, of Larson-Peterson and
Associates, Inc., and Dr. T.A. Rogstad, Chairman, Pelican River Watershed
District.
Surface water discharge measurements were performed by the U.S. Geologi-
cal Survey, Charles Cornelius, Montevideo, Minnesota, in cooperation with
Albert M. Ungerecht, Research Assistant on this project, who also measured
water elevations in groundwater sampling wells.
Sampling and analyses were performed by Research Assistants David F.
Brakke, Jayce L. Lahlum, Richard S. McVoy, Stanley J. Miekicki, Arlene P.
Moran, Michael Pfeifer, John W. Stambaugh, Jr., and William M. West.
IX
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SECTION 1
INTRODUCTION
This report covers the second phase of a study program designed to learn
methods that may be applied to reversal or alleviation of cultural lake
eutrophication. Phase 1 (1) evaluated the possibility of critical nutrient
reduction through harvest of aquatic weeds and associated organisms and led to
the conclusion that removal of all organisms from the lake under consideration
(Lake Sallie, Minnesota) would decrease annual nutrient increments by a very
small fraction and would alone contribute little or nothing toward the lake's
recovery. Harvest did markedly reduce the growth of aquatic weeds in
succeeding years.
Soon after the results of Phase 1 were known (1971) a conference, attended
by project personnel, representatives of the EPA, U.S. Geological Survey, the
Minnesota Department of Natural Resources, and consultants, led to the opinion
that a more profitable approach toward solution of these lake eutrophication
problems was reduction or removal of nutrients in influent waters. It was
recommended that what then appeared the major nutrient inflow, wastewater
effluent from the City of Detroit Lakes, Minnesota, be subjected to additional
treatment procedures to remove nutrients, especially phosphorus. Methods
approved by the group were: (1) chemical precipitation, (2) intermittent
application to grassed adsorption galleries, and (3) spray irrigation. These
procedures had previously been applied singly to individual wastes at other
locations, and it was agreed that their relative efficiency could better be
learned by applying all 3 to the same effluent.
Meeting the directives of this conference required, in addition to con-
struction of treatment facilities, (1) expansion of the analytical program to
cover groundwaters in the Pelican River watershed above Lake Sallie,
especially in the region to receive applications of wastewater effluent, (2)
continuation of the Lake Sallie program involving study of water, bottom
sediments, surface and groundwater inflow, plankton, chlorophyll, primary
production, etc., (3) expansion of these procedures to include water bodies
traversed by the wastewater effluent enroute to Lake Sallie, and (4) sampling
of the Pelican River at key locations to ascertain conditions in the water-
shed above entrance of the wastewater effluent.
This program began in 1972. Early phases were reported in MS theses by
Miekicki (2), and Brakke (3); watershed plankton studies were carried out in
1974-75 by Stambaugh (17), and chlorophyll-phytoplankton relations were
considered by West (18). Abstracts of these 4 MS theses appear in the
Appendix. Dissertations dealing with Phase 1 investigations were written by
Peterson (6) and Smith (7); Lee (8) was author of an MS thesis dealing with
nutrients entering Lake Sallie in groundwater.
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SECTION 2
CONCLUSIONS
1. Lakes in the upper Pelican River watershed are situated in permeable
soils and are subject to considerable groundwater flow-through.
2. The general trend of groundwater movement in the western part of the
upper basin is south toward Long Lake, the waste treatment area, Lake St. Clair,
and Lake Sallie.
3. Surface discharge in the western area, which includes wastewater
effluent from the City of Detroit Lakes, amounted to 22% of the total reaching
Lake Sallie via the Pelican River and 28% of the surface discharge from
Detroit Lake, which represents the eastern part of the upper basin.
4. Chemical data indicated both a spatial and seasonal non-uniformity of
groundwater quality. Phosphorus and nitrogen varied from year to year
(1973-74, 1974-75); phosphorus was markedly less concentrated the second year
and nitrogen slightly so.
5. Most groundwater nitrogen was present as NH^-N or NO^-N, their
relative abundance apparently dependent on oxygen level. Neither was noted
to be absent, but NH3-N was most concentrated when oxygen was very low or
absent and NO-j-N when oxygen was in middle or upper groundwater ranges.
6. Slightly more than 12 months has been required for groundwater to
make a general appearance in watershed surface waters; and high groundwater P
concentrations in 1973-74 were followed by increased P values in surface
water in 1975, and lower groundwater P concentrations in 1974-75 were trans-
mitted to surface water in 1976.
7. Project resources limited groundwater study to the area within and
adjacent to the wastewater treatment facilities, but this region was assumed,
with a high confidence level, to be diagnostic of the upper watershed when
surface water changes in. other parts coincided in time and character with
those attributable to groundwater in the study area. Screen casings permitted
groundwater to pass through wells at the levels it occupied in surrounding
soils.
8. Although groundwater varied chemically at different sites and depths
in the water table, it was quite distinct in character from surface water
present at the same time.
9. In 1973 and 1974, the major share of the P load entering Lake Sallie
via the Pelican River was in the wastewater effluent from the City of Detroit
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Lakes, but in 1975 most P going into Lake Sallie came from non-point sources
in the drainage area above Detroit Lake. No groundwater sampling was carried
out in that area, but similarities in annual surface water changes to those
in the area with groundwater records strongly suggest that higher surface
water P values in 1975 came from water that had been underground the preceding
year.
10. Sources of P in the phreatic zone are unknown. Quantities brought
to water surfaces by precipitation are inadequate to account for non-point
loads any year, but P in summer precipitation to the 12,821 hectare upper
watershed has amounted to 29 - 43% of the annual P ]oad from Detroit
Lake. Summer rains have provided a rather uniforn percentage of total precip-
itation from year to year, but the fate of rain borne P in soils and the
constancy of P concentration in precipitation over the seasons are quite
speculative at this time. If atmospheric P is notably involved in amounts
carried in groundwater, it appears that 2 or more years are required for it to
travel from soil surface to phreatic zone.
11. Phosphorus in groundwater was assumed to come from surface applica-
tion in some form, precipitation, fertilizers, manure, etc., but detailed
records of farm practices, precipitation chemistry, etc., over a period of a
few years seem necessary to establish its sources, and studies to ascertain
its travel time through soil to the water table would seemingly require a like
amount of time.
12. Heterocystous blue-green phytoplankters were not observed in the 2
sewage ponds (see study area description); they became predominant for all or
a major part of the growing season in lakes receiving some share of the waste-
water effluent, were dominant for 8 weeks spread through July, August and
October in discharges from the 2 Floyd Lakes in the upper watershed (Figure 1),
practically disappeared from the Pelican River before it reached Detroit Lake,
and were never more than a minor component of the plankton leaving that lake.
13. Heterocystous blue-green algae never amounted to more than a small
percentage of the total mass of photosynthate produced in any lake but were
responsible for the most offensive conditions observed. Rooted and attached
vegetation produced physical nuisances.
14. Nitrogen fixation by blue-green algae was detectable by aberrant
oxygen-pH relationships when they dominated the phytoplankton.
15. Groundwater seepage brought in significant quantities of water,
phosphorus, and nitrogen in lakes where it was measured and analyzed, conspic-
uously more nutrients than they received directly from precipitation.
16. Precipitation was the lowest ranking contributor of P and N directly
to lakes, but amounts so supplied in summer to the upper 12,821 hectare water-
shed ranged from 1.39 to 2.88 metric tons P and 15,3 to 58.82 metric tons N.
17. Lake St. Clair, a small shallow natural lake, first in line to
receive effluent from the stabilization pond, became crowded with macrophytes
and attached vegetation each year but produced also quantities of blue-green
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phytoplankters that affected water chemistry. Marl composed 80-85% of
sediments in the lake's central area but only 30% or less of those in the
littoral zone. In 1974 its sediments contained 9.82 and 35.37 metric tons,
respectively, of P and N. Its blue-green dominated phytoplankton fixed
nitrogen from the atmosphere over most of the growing season, and primary pro-
duction by this plankton population ranged from 2 to 4.25 grams of C fixed per
hour over the period 8:30 a.m. to 2:30 p.m. CDT.
18. Lake Sallie exhibited intermittent thermal stratification in summer,
and total time it was in this condition was very short in 1974 and 1975.
Distribution of P in its bottom sediments suggests that conditions leading to
calcium deposition reduce P availability and that CCL production enhances it.
In 1974 the bottom loads, in metric tons, were nitrogen 208, total P 45.06,
and SRP 9.74. Weeds accessible to the available harvester declined each year
following initial harvest in 1970 and were not considered worthy of harvester
effort in 1973 and 1974. In 1975 higher lake level permitted harvesting in
areas previously too shallow to enter, and 41 metric tons wet weight were
removed. Phosphorus taken out with weeds also declined progressively. Some
qualitative changes in the macrophyte population followed weed harvest. Some
photosynthesis occurred under ice and snow cover. Primary production by
phytoplankton was lower than in Lake St. Glair.
19. A trophic state index, based on increase in the Mg/Ca quotient
relative to water residence time and developed from records on 4 watershed
lakes and the stabilization pond, has indicated relative status of each with
regard to total photosynthate production. Experience to date suggests that
this index will probably be generally applicable to those standing water
bodies whose major inflow and outflow may be sampled, except possibly reser-
voirs that have a large share of discharge from their hypolimnions. In
these watershed lakes it has provided a precise mathematical statement that
has denoted the relative productivity status of each and has proved much more
descriptive of individual situations than terms, mesotrophic, eutrophic, etc.,
currently applied.
20. Calculation of the above trophic state index (TSI) requires measure-
ment of (1) lake volume, (2) annual outflow volume, and (3) calcium and
magnesium (preferably as CaCO-) concentration of inflow and outflow at regular
intervals (probably biweekly) over 12 consecutive months. The formula for
calculation appears in the body of this report. Since this TSI reflects total
photosynthate production, it may hardly be expected to be exceptionally
reliable in predicting nuisance conditions that may develop from accelerated
growth of a restricted group or biotic segment. Such irruptions may be in-
fluenced by environmental factors not especially related to over-all
productivity, and their occurrence at times may actually have a negative
effect on total plant growth. This index has proved very helpful in conduct
of these studies. It has (1) established total productivity rankings among
the varied lakes under prevailing conditions, (2) demonstrated that nuisance
conditions due to blue-green algae are not necessarily indicative of highest
trophic state, (3) indicated that attached algae and vascular plants produce
greater masses of photosynthate than phytoplankton, (4) reaffirmed that
nutrient loading and lake conditions control productivity, and (5) pointed out
rewarding study routes. Experience here shows it to be unaffected by lake size
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from 3 to 38,602 hectare meters capacity, by total hardness concentration up
to 1,045 mg/1, or by wide variation in the carbonate/noncarbonate hardness
ratio. Several other details appear in the body of this report.
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SECTION 3
RECOMMENDATIONS
1. This study demonstrated that a wastewater effluent does not always
overshadow non-point sources in supplying nutrients to a small watershed; and
it appears that in many cases non-point sources will need be sought and
evaluated for meaningful appraisal of areal eutrophication problems.
2. It has been shown here that groundwater can have a delayed but very
marked effect on phosphorus load in surface waters and that the strength of
subterranean waters differs from year to year; but these data shed very little
light on sources of groundwater P, and other nutrients, and the mechanics of
their transport through soil. Data on these aspects, including any organisms
involved, would be very helpful to eutrophication study and control.
3. The most noxious condition appearing in these water bodies arose
through heavy development of heterocystous blue-green phytoplankters. The
occurrence of prevalent growths of these organisms was apparently not con-
trolled by nutrient loading in the ranges encountered; they were not
conspicuous in all lakes nor throughout the growing season in most lakes in
which they at times achieved dominance. These facts suggest that investigation
into their natural energizing and limiting factors would be quite relevant, as
their control may prove to be a workable approach to improvement of lake
conditions stemming from non-point enrichment.
4. The trophic state index used here accurately indicated the relative
productivity of 6 standing water bodies, and its testing on other waters in
varied geographic areas is advocated. If it proves generally applicable, it
should simplify eutrophication assessment and terminology.
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SECTION 4
STUDY AREA
PELICAN RIVER WATERSHED
The upper Pelican River is a rather slow streamtraversing a number of
lakes (Figure 1). It begins with Campbell Creek ( \l) , Figure 1) and acquires
the name of the river when it leaves Little Floyd Lake. Just below Detroit
Lake it is joined by a ditch that carries discharges from Long and St. Clair
Lakes, which include effluent residuals from waste treatment facilities at the
City of Detroit Lakes (see below). The river is dammed just above Lake Sallie,
forming 26-hectare (65-acre) Muskrat Lake, which discharges to Lake Sallie
over 2 adjustable weirs at the heads of 2 concrete-lined flumes. Monson and
Fox Lakes have small, the latter intermittent, discharges to Lake Sallie.
The Pelican River watershed represented in this sampling program extends
from Campbell Creek to the outlet of Lake Sallie and includes final sewage
treatment facilities for the City of Detroit Lakes and the lake and stream
they pass through enroute to the Pelican River. Layout of the treatment area
appears in Figure 2,
Sampling stations shown in Figure 1 are as follows:
A. Aerated pond following secondary (biofiltration) sewage treatment
B. Stabilization pond receiving effluent from A, outlet
E. Long Lake outlet
F. Lake St. Clair outlet
G. Drainage ditch above Highway 6
H. Drainage ditch above Pelican River
I. Campbell Creek above Floyd Lake
J. Floyd Lake outlet
K. Little Floyd Lake outlet
L. Pelican River at Highway 34
M. Pelican River above Detroit Lake
N. Detroit Lake outlet
P. Pelican River above Muskrat Lake
1. Muskrat Lake outlet to Lake Sallie
8. Lake Sallie outlet
Discharge data have been available for Stations A, B, F, M (January-June,
1975, only), N, 1, and 8.
Areas, depths, and volumes of the lakes involved (Figure 1) appear in
Table 1 and total annual discharges are listed in Table 2.
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Figure 1
Upper Pelican
River Watershed
x Sampling Wells
Sampling Stations
Spray Irrigation Plots
Stabilization Pond
FOX LAKE
CITY'OF
DETROIT
LAKES
MONSON LAKE
SCALE IN FEET
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Figure 2. Details of Treatment Area
N
IRRIGATION
AREAS
INFILTRATION
BASINS
LIME SLUDGE BEDS
C3CHEMICAL PRECIPITATION PLANT
I STAE
SEWAGE
STABILIZATION
POND
AERATED POND
WASTE TREATMENT
PLANT
600 1200
SCALE IN FEET
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Flow is regulated at the Muskrat Lake dam, and discharge at Station 1 is
not considered representative of natural conditions. Losses indicated for
F + N discharges at Station 1 in 1973 and 1974 may reflect control exercised
at the weirs in the Muskrat Lake dam, as may the gain indicated for 1975.
Mean water residence times in those water bodies with discharge records
over the period 1973-75 were:
Detroit Lake 2.17 years
Lake St. Clair 0.10 years
Muskrat Lake 0.012 years
Lake Sallie 0.70 years
Aerated pond 0.02 years
Stabilization pond 0.03 years
As reference to Table 3 will demonstrate, soils in the upper Pelican
River watershed are composed of permeable materials, sand, gravel, glacial
till, etc., at least down into the phreatic zone. Lakes in this area are
interposed in groundwater flow, receiving all or significant amounts of their
inflow from this source and returning varied quantities. There have been no
direct measurements of water volumes going from ground to lake to ground, but
in some instances surface water discharge records show changes that may be
attributed to gain from or loss to groundwater. Long Lake has no surface
inlet, and it appears that its major outflow is to the ground. From December,
1974, to June, 1975, Detroit Lake, as estimated from surface inflow and outflow
records and evaporation losses, gained about 560 hm (4,520 af) from the ground.
Mann and McBride (11) indicated that Lake Sallie gained 19 and 22% of its total
inflow in 1969 and 1970, respectively, from ground sources. Over 1973-75 an
estimated 13% of water entering Lake Sallie was from the ground.
Miscellaneous Lake Features
The only observations on the 2 Floyd Lakes relate to water chemistry and
plankton of their discharges. In other lakes autotrophic populations have
been dominated by rooted, floating, and attached plants; and these forms have
been reduced in Lake Sallie by weed harvest.
The aerated pond is continuously oxygenated by a tethered floating mixer
that drives air into the water. It has had very little attached or rooted
vegetation, and its ice cover has never been complete. Volume varied in the
stabiliEation pond in 1974-75 largely due to construction of advanced waste
treatment facilities. Dense accumulations of duckweed have covered most of
its surface during growing seasons of the 3 year period.
10
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SECTION 5
METHODS
SAMPLING
Surface and groundwater samples were collected with Kemmerer samplers.
Groundwater was obtained from 15.25 era (6") diameter wells, with PVT, casings,
that were drilled down to gray till, which occurred at varying distances
below the soil surface. The lower part of each casing was formed by a plastic
screen that extended from the well bottom up to near the upper limit of the
saturated zone or water table. It was hoped that this screen would permit
normal lateral passage of water through each well, and analytical results
suggest that water moved through wells at the level it occupied in the
surrounding earth formations. Details of each well appear in Table 3. Where
water depth permitted, surface and bottom samples were taken from weH water
columns.
Groundwater seepage into lakes was collected in evacuated plastic bags
connected to a cap (the cut-off end of a steel drum) that isolated a 0.325 m
area of bottom. This collector was developed for seepage studies in Lake
Sallie and is described by Lee (6 and 7) in some detail. As groundwater head
declined, it was necessary to move these collectors farther into the lake; and
they sometimes were partially or completely clogged by algae, fungi, or benthic
animals. Lee (7) lists problems he encountered.
Sediment samples were collected with an Ekman dredge which drove to a
depth of 15 cm (6"). Plankton was taken with a Kemmerer sampler and concen-
trated by settling. Sampling of lakes was omitted during periods of ice
formation in early winter and ice melt in spring.
Precipitation samples were collected in enamel pans that were placed on
stands to avoid surface splash and located beyond the reach of eave and tree
drip.
ANALYSIS
Most chemical methods were according to Standard Methods, 13th edition
(8). Total phosphorus was by the method of Krawczyk (9) and NO-^ as described
by Strickland and Parsons (10). Field measurement of oxygen was usually with
a galvanic cell oxygen analyzer that was calibrated every 2 hours.
Water analyses were conducted on the date of collection and phosphorus
for groundwater samples within 3 hours. Tests showed that longer periods of
11
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storage generally resulted in grossly exaggerated P values.
MISCELLANEOUS
Primary production by phytoplankton was measured with the light and dark
bottle technique with 2-hour incubation periods from 8:30 a.m. to 2:30 p.m.,
CDT. Weed harvest was with the same apparatus listed in the 1973 report (1),
and weeds removed were hauled out of the drainage basin. Weighing of harvested
weeds was limited to Lake Sallie.
12
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SECTION 6
RESULTS AND DISCUSSION
CLIMATOLOGICAL DATA
Air temperature and precipitation data from U.S. Weather Bureau records
over 1973-75 appear in Table 4. Mean annual air temperature declined over the
3-year period, but some months were contrary to this trend as may be noted in
the table. Precipitation declined 24.37 cm (9.6") below the 1973 amount in
1974, but 1975 received 14.55 cm (5.73") more than 1974. The heaviest monthly
total was in June, 1975, which was followed by severe flooding of local streams
extending into July. This, in turn, produced the highest water level observed
in Lake Sallie over the 7 years (since 1968) this study has continued and
permitted weed harvest in areas previously too shallow for the harvester to
enter.
Discharge records for the Pelican River in the study area end with June,
1975, but measurements at a site near Fergus Falls, Minnesota, about 30 miles
downstream from the study area, show unusually high discharges in July and
August, 1975 (Table 5).
WATER QUALITY
Watershed Nutrients
Surface Waters—
Concentration—Mean annual concentrations of total P and total inorganic
N (NHo—I- N02—I- NOo-N) varied over the watershed (Table 6) and at individual
sites over the seasons (Tables 7 and 8). The aerated and stabilization ponds
were most heavily endowed in these respects, and their influences carried
through Lake St. Clair and into the ditch below, but P was diluted noticeably
when the ditch joined the Pelican River (see Muskrat Lake inlet). All lake
and stream sites above entrance of the wastewater effluent showed marked in-
creases in total P concentration in 1975 that could only result from general
watershed conditions. Only a minor share of this phosphorus was brought in by
precipitation (see precipitation section); and it appears that these increases
must be attributed to the soil. Reference will be made to this matter again
in the groundwater section. High phosphorus levels from non-point sources may
have been produced by unknown, unusual phenomena in 1975, and there is no
certainty that they will be continued over later years.
13
-------
Total nitrogen was most concentrated in water containing 10% or more of
the wastewater effluent (Station A down to Station H in the ditch).
Total P and soluble reactive phosphorus (SRP) were generally higher in
1975 than in 1974 (Figures 3 and 4). This trend was evident in both waste-
water effluent and land drainage. There was a basin-wide increase in phos-
phorus content of runoff in 1975; it was most concentrated in wastewater in
winter and declined as aeration and stabilization ponds supported photosyn-
thesis during the growing season (Figures 3a, b and 4a, b). A low record
frequency makes 1974 values prior to June invalid for comparison with 1975
data, but in summer and late autumn variation at Station A was much greater in
1974. Greater uniformity and concentration of P in 1975 may both reflect
influences of higher P levels in general runoff.
These data (Figures 3 and 4) were plotted chiefly to illustrate that
phosphorus control was exercised either by conditions restricted to individual
water bodies or by phenomena common to the entire watershed. Reference to
Figures 3a and 3b will show that in 1974 phosphorus patterns at Stations A and
B were each largely due to events in each pond. In 1975 (Figures 4a and 4b)
peaks at Station B in late January and mid-March could be interpreted to
represent transmission from Station A, since there is an 11-day detention
period between Stations A and B. However, the January and March peaks occurred
at Station F (Figure 4c) on the same dates they were evident at Station B, and
time of passage between those 2 points was 37 days. The March high was also
present on the same date, albeit to a lesser degree, at Stations P, 1, and 8,
where similar patterns also occurred in April. Farther up the Pelican River,
Stations M and N had closely corresponding P peaks and lows in March, April,
and May, 1975 (Figures 4e and 4f), despite their being separated by a 792-day
time interval. Phosphorus dynamics usually seemed a function of individual
water bodies, and it is assumed that basin-wide similarities in phosphorus
patterns indicated like processes or conditions in this respect in each of the
various water bodies. Reference to Figures 3 and 4 will show that sometimes
only 2 water bodies exhibited like patterns.
It may be noted in Figures 3 and 4 that there were often marked differ-
ences in the amount of SRP. Up and down oscillation was frequent at all
stations in 1975, but those with larger percentages of sewage effluent, and
higher P concentrations, showed considerably less amplitude most of the time
(Figure 5). Amplitude increased as sewage (and P) load decreased. SRP de-
clined with sewage load from Stations A through 8 but decreased with a slight
increase in total P between Stations M and N.
Variation in per cent SRP during the growing season may possibly be
attributed to varying utilization by autotrophs in the aeration and stabiliza-
tion ponds and to assimilation by and release from autotrophic tissues in the
more lightly loaded lakes. Neither of these would account for the similar
patterns shown under ice cover when autotrophic activity was generally quite
low or non-existent and metabolism slow, and this suggests that other explana-
tions should probably be sought for growing season variation.
Comparison of 1975 weekly NH3-, N02-, and N03-N concentrations at
Stations A, B, and F (Figures 6, 7 and 8) shows that autotrophic activity was
the prime remover of nitrogen from solution. The aeration pond (Station A)
14
-------
3Ch
25-
20-
15i
en
E
10-
5-
Total PO4
SRP
Figure 3a. Total P and SRP Station A
(Both as PO4)
\ —_
\
T I
19 24 13 12 4 11
JAN FEB MAR APR MAY
JUN
1974
JUL AUG NOV DEC
-------
30-
25-
20-
to 15-1
OB lsj
10-1
5-
0-
Total PO4
SRP
Figure 3b. Total P and SRP Station B
(Both as PO4)
19 24 13 12 4 11
JAN FEB MAR APR MAY
JUN
JUL
AUG
NOV DEC
-------
8-
Cf
Q_
2-
O
Total PO4
SRP
Figure 3c. Total P and SRP Station F
(Both as PO4)
\
\
\
X
I I I I I I
19 24 13 12 4 11
JAN FEB MAR APR MAY
JUN JUL
1974
AUG
/
/
•V
/ \ -J
NOV DEC
-------
00
1-
0-
2-
Sta. 8
Figure 3d. Total P and SRP
(Both as PO4)
*° 1
nJ *
"o>
O
2-
Sta. 1
Total PO4
SRP
1-
0-
Sta. P
19 24 13 12 4 11
JAN FEB MAR APR MAY
\/
'2.75
AT
JUN
1Q74
JUL
^^^^^^^^^^^ ^^^^^^^^^^^^^^^1
AUG NOV DEC
-------
2-
1-
Cf
0.
Figure 3e. Total P and SRP
(Both as PO4)
Sta. N
Total PO4
SRP
Sta. M
\/
V
JUN
NOV DEC
-------
70-,
60-
50-
M O
0 Q-
-------
60
50
40
30
20
10-
Figure 4b. Total P and SRP
Station B (Both as PO4)
JAN FEB MAR APR MAY
JUN
1975
JUL
AUG SEP OCT
NOV DEC
-------
20
S3
S3
15-
$
$ 10
en
E
5-
O
Total P
SRP
Figure Ac Total P and SRP
Station F (Both as PO4)
=raF-r
^^^^ r
^A
JAN
FEB MAR APR
MAY
JUN
1975
JUL
AUG SEP OCT
NOV DEC
-------
Figure 4d Total P and SRP (Both as PO4)
o-
Total P
SRP -
Sta. P
2-
0-
JAN FEB MAR APR MAY
JUN
1975
JUL
AUG SEP OCT NOV DEC
-------
8
0
Figure 4e. Total P and 5RP
Station M (Both as PO4)
JAN
FEB MAR APR
MAY
JUN
1975
JUL
AUG SEP OCT
NOV DEC
-------
8-
6-
4-
m Q_
-------
100-
90-
80-
70-
60-
50-
40-
30-
20-
10-
Mean 68%
100-1
90-
80-
2s 70-
60-
50-
4O-
30-
20-
10
Sta. B
Mean 83%
100-
90-
80-
70-
60-
5O-
40-
30
Mean 86%
Figure 5a. Percentage of Total P Formed by SRP
JAN
FEB MAR APR
MAY
JUN JUL
1975
AUG SEP OCT
NOV DEC
-------
N3
100n
90-
80-
7O-
60-
5O-
40-
30-
20-
10-
O-J
10O-1
90-
80-
70-
60-
50-
4O-
30-
20-
10-
04
100!
90-
80-
70-
60-
50-
40-
30-
20-
10-
O-
Mean 49%
Sta 1
Mean 58%
Sta. P
Mean 62%
Figure 5b. Percentage of
Total P Formed by SRP
JAN FEB MAR APR MAY JUN JUL
1975
AUG SEP OCT
NOV DEC
-------
t-o
00
Mean 44%
Mean 52°/
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT
1975
Figure 5c. Percentage of Total P Formed by SRP
NOV DEC
-------
20
15-
2
^ 10'
O)
E '
5-
0-
NH3
NO2
NO3
:S
Station A
Figure 6. Ammonia, Nitrite, and
Nitrate Nitrogen Variation
JAN
FEB MAR APR
MAY
JUN
1975
JUL
AUG SEP OCT
NOV DEC
-------
UJ
o
NHa
NOa
NO3
Station B
Figure 7 Ammonia, Nitrite, and
Nitrate Nitrogen Variation
JAN
FEB
T ' ' I
MAR
APR
MAY
AUG SEP OCT
NOV DEC
1975
-------
10-i
9-
8-
7-
NH3-
NO2-
NO3-
Station F
JAN
Figure 8. Ammonia, Nitrite, and
Nitrate Nitrogen Variation
FEB MAR APR
MAY
JUN
1975
JUL
AUG SEP OCT
NOV DEC
-------
developed a plankton population in early May, 1975, and maintained it until
early December when sampling stopped. The population density varied from 120
to 318,336 organisms per ml, but was usually above 10,000. Higher concentra-
tions were in May, October, and November. The general nitrogen level
(Figure 9) was lowered following development of phytoplankton; but a peak in
June, due to NO^-N increase, was above the winter level, and another in early
September, reflecting NH3~N rise (Figure 6), nearly equalled it. It is assumed
that both high concentrations were present in wastewater entering the aeration
pond. Autotrophic activity mainly, if not exclusively, affected NH-^-N in this
period; nitrate varied over a wider range but not in manners that suggested a
relationship with autotrophism.
Autotrophic nitrogen removal was more evident in the stabilization pond
(Station B), but the June NO^-N and September NH-j-N pulses carried over from
Station A (Figures 6 and 7). Here NO-j-N decreased with NH-j-N. In Lake St.
Clair (Station F) NHo- and NO--N were reduced by photosynthesis (Figure 8),
but concentration of NO^-N was, relative to Stations A and B, quite low, and
autotrophic influences were most noticeable on NHo-N. A June peak in NHo-N
here corresponded to elevations of NOo-N in Stations A and B.
Nitrogen variation in these 3 water bodies suggests that NHo-N was
selected first by active autotrophic organisms and that recourse was made to
NOo-N only after supplies of NH-j-N were inadequate to meet the population
demands. In the aeration pond quantity of NHo-N always appeared adequate, but
in the stabilization pond and Lake St. Clair recourse was evidently made to
NOo-N after NHo-N declined noticeably below 1.0 mg/1. At Station F summer pro-
duction of NHo-N did not attain 1.0 mg/1, and nitrate was suppressed until
autumn. In the stabilization pond NOo-N and NHo-N were augmented at times by
inflow from Station A, and relationships of these 2 forms of N were less clear-
cut. Phytoplankton also developed in B and F in early May and endured until
winter. Nitrogen fixation by blue-green algae occurred in Lake St. Clair each
year.
Loads—In 1973 and 1974 the major part of the phosphorus load reaching
the Lake Sallie inlet was discharged from Lake St. Clair, but in 1975 this
wastewater affected load was exceeded by that contributed from non-point
sources upstream from Detroit Lake (refer to Stations F and N in Table 9).
This reversal was occasioned by higher concentrations in watershed drainage,
not by greater amounts of runoff. Phosphorus was detained and lost to ground
drainage in the stabilization pond (Station B) each year, but this was followed
by a gain in Lake St. Clair (Station F), which apparently came to a large
extent from this seepage. There was a phosphorus loss each year between the
ditch-Pelican River junction and the Lake Sallie inlet (Station 1) that was
occasioned by discharge loss (largest in 1973) and precipitation and loss to
seepage in Muskrat Lake. Seepage into Lakes Sallie and St. Clair will be
described later.
Considerable quantities of Pelican River-borne phosphorus remained in
Lake Sallie each year, giving a 13.72 metric ton (15.11 ton) build-up over the
2-1/2 year period covered in Table 6. In 1973 and 1974 4.40 metric tons
remained in the lake water mass, and during the first 6 months in 1975 this
load built up to 11.22 metric tons. In early autumn 1974 bottom sediments
32
-------
25 -,
Figure 9
Total N 1975
i i i | i | i i i i T™T™T™^iM
0
JAN FEB MAR
APR
MAY
JUN
JUL
AUG SEP OCT
NOV DEC
-------
(upper 15 centimeters) contained 45 metric tons of phosphorus, and it would
appear that 2,50 metric tons, net, were added to bottom sediments from Pelican
River inflow over this 2-1/2 year period (13.72 - 11.22).
TABLE 9. TOTAL PHOSPHORUS LOADS AT WATERSHED STATIONS (METRIC TONS)
A B F N F + N 1 8
1973
1974
1975
TOTALS
12.02
5.15
6.18
23.35
6.34
2.76
4.12
13.22
10.46
5.88
5.96
22.30
6.40
3.52
9.98
19.90
16.86
9.40
15.94
42.20
12.70
9.64
9.52
31.86
6.10
4.98
7.06
18.14
1975: January-June records
Nitrogen loads were at times affected by nitrogen fixation from the
atmosphere and groundwater seepage into lakes. Active nitrogen fixation
occurred in Lake St. Glair (suggested by high pH and low oxygen levels over
extended periods) but routine analytical methods did not denote N in the
organic state and hence omitted quantities carried in bodies of organisms
leaving the lake. It is assumed that loads leaving Lake St. Clair (Table 10)
were in excess of those indicated by analyses for inorganic nitrogen compounds.
Nitrogen loss at Station B seemingly reflects utilization by plants and loss to
seepage. Nitrogen fixers rarely occurred there.
Organisms in Lake Sallie appeared to utilize more nitrogen than they
fixed in 1974 and 1975, but the reverse seemed true in 1973. Nitrogen loads
therefore have shortcomings for estimation of nutrient point source contribu-
tions, even at short distances from such sources, in this watershed.
Groundwater—
Locations of the 33 groundwater sampling wells are shown by X's in
Figure 1, and a more detailed map of the well area is presented as Figure 10.
Wells were grouped into sub-areas that represented distinctive surface regions
as related to this project. These sub-areas are:
1. Airport and vicinity
2. Proposed irrigation area
3. N of stabilization pond
4. S of stabilization pond
34
-------
19
•13 .18
Subarea 1
•12
•31
Long Lake
derated
Pond
Stabilization
Pond
'Subarea 4
Subarea 6
Subarea 5
©Water Level Measurement Only
29
Figure 1O. Locations of Ground
Water Sampling Sites
35
-------
5. S of Lake St. Glair
6. NE of Lake St. Clair
7. E of Long Lake
TABLE 10. TOTAL NITROGEN LOADS AT WATERSHED STATIONS (METRIC TONS)
A B F N F+N 1
1973
1974
1975
TOTALS
19.60
11.06
9.80
40.46
7.40
5.12
4.04
16.56
6.24 ,
9.22
6.30
21.76
2.96
3.62
3.84
10.42
9.20
12.84
10.14
32.18
7.74
10.64
10.. 80
29.18
9.04
8.38
5.74
23.16
1975: January-June records.
Well numbers in each sub-area and groundwater sampling periods appear in
Table 11, and sub-areas are delineated in Figure 10. None of the above areas
contains human habitations. Features of each well, bottom and water level
elevations, earth strata penetrated, etc., are listed in Table 3.
General groundwater features—The considerable vertical extent of plastic
screen provided by these wells seemingly permitted water to pass laterally
through the pipes at or near the depth it occupied in the soil. Chemistry of
water near the top of longer well water columns was usually noticeably, often
markedly, different in 1 or more parameters from that near the bottom. This is
quite evident in mean nutrient concentrations appearing in Table 12. It was
also common for calcium and magnesium (Table 13), alkalinity (Table 14), oxygen
and pH. Vertical temperature differences were often evident in the deeper
wells, with surface temperature usually colder in winter and warmer in summer
than that near the well bottoms.
Most wells maintained some oxygen in solution, top and bottom, over the
2 record periods. Nitrate nitrogen attained its greatest concentrations when
oxygen was present and ammonia when it was absent, but ammonia at times occur-
red in the presence of oxygen and nitrate when oxygen was absent. Nitrogen
values were often quite high, as evidenced by mean values in Table 12.
All parameters of water chemistry varied over the seasons in individual
wells, which is assumed to indicate continuous lateral flow through each and
not changes that would come about in a stagnant water column with passage of
time. Random selection of any individual well records shows this, although it
36
-------
is more marked in some instances than others. PC-28T and B, for instance,
over the 1973-74 record period, exhibited the following ranges:
Top
Bottom
pH
Alkalinity
Hardness (T)
Calcium
Magnesium
Total PO,
NH3-N
N03-N
Oxygen
7.15 - 7.80
68 - 394 mg/1
140 - 462 mg/1
90 - 315 mg/1
50 - 147 mg/1
6.95 - 7.70
164 - 398 mg/1
375 - 710 mg/1
245 - 435 mg/1
120 - 307 mg/1
0.395-6.40 mg/1 0.26-4.50 mg/1
0.46-2.40 mg/1 0.395-2.95 mg/1
0.099-1.198 mg/1 0.003-1.00 mg/1
0.06-2.40 mg/1 0 - 0.4 mg/1
The above data are also illustrative of differences in upper and lower
parts of the water columns in the deeper wells. In PC-28, which was selected
at random, NEU- exceeded NO-j-N, but this was by no means characteristic of all
wells. N03-N/NH3-N ratios for PC-28 were : top, 0.348, bottom, 0.19; whereas
in PC-2, also picked at random, they were: top, 7.54, bottom, 9.78.
Nutrient concentration—Mean nitrogen and phosphorus concentration in
groundwater at top and bottom of each well sampling site appears in Table 12
and the averages of top and bottom concentrations (top only for shallow wells)
for groundwater sub-areas and wells contained in each are listed in Table 11.
In the latter table it may be noted that,,with the exception of sub-areas 4 and
7, phosphorus was markedly more concentrated in 1973-74 than in 1974-75. Sub-
area 4 exhibited the highest P mean value each period, and its constancy over
the 2 periods suggests a steady source of supply to that region, namely, the
stabilization pond.
Nitrogen was also less concentrated in 1974-75, although to a less
degree; but in this case it was sub-area 5 that showed the greatest constancy.
Concentrations of nutrients in groundwaters in this area is significant
and critical for surface waters into which they discharge. The Detroit Lakes
wastewater contributes these compounds to a relatively small part of the
sampled groundwater area (sub-areas 4, 5, and 6); and surface land application
in fertilizer, and perhaps in precipitation, seems the most likely source of
nutrients, especially phosphorus, in the uninhabited region north of the stabi-
lization pond. Time of P passage from soil surface to the saturated zone or
water table is unknown.
37
-------
Ground and surface water—Velocity of groundwater movement across the
sampling area and time required for its emergence in surface water bodies were
not directly measurable. Comparison of ground and surface water phosphorus
concentrations over 1974 and 1975 suggests that about a year is required for
the general appearance of unconfined groundwater in lakes and stream segments
studied. Tables 6 and 11 show that high groundwater P levels in 1974 were
followed by high surface water concentrations in 1975, which gave larger P
loads from general drainage than from the sewage effluent. If this indicated
ground-surface time relationship is valid, 1976 surface P levels should show
a decline from the 1975 concentrations; and 20 records over the period from
January 9 to July 24, 1976, indicate a general and, in most instances, a
marked reduction at surface water stations representative of general watershed
runoff. Mean P concentrations for 1974, 1975 and 1976 at these stations were:
Little
Long Campbell Floyd Floyd Station Station Detroit
Lake Creek Lake Lake L M Lake
1974 0.19 0.20 0.20 0.20 0.31 0.23 0.22
1975 0.37 0.85 0.35 0.38 0.45 0.46 0.47
1976 0.22 0.28 0.25 0.32 0.29 0.25 0.30
With the exception of Little Floyd Lake, surface waters had significantly
less P in 1976, many returning to near their 1974 mean concentration after
record highs in 1975. Long Lake, situated near the groundwater sampling area,
is considered particularly diagnostic in this respect.
Groundwater movement—Mean groundwater elevation at each sampling site
over 1974-75 and mean surface elevation of Long Lake appear in Figure 11, and
contours and likely flow paths developed from these means in Figure 12. Water
level elevation was lowest at Site 27 and highest near the airport at Site 13.
The general flow trend was toward Lake St. Clair with divergences to east and
west, as shown in Figure 12. The mean water level elevation in Long Lake was
below that of the water table in ground areas to the Bast, but uncertainties
regarding the course of the 1,349' water level contour do not permit a positive
statement at this time. There seems little reason to doubt that Long Lake
discharged to the ground in the vicinity of Well Site 30.
The lowest groundwater level was at Site 27, just east of Lake St. Clair
(Figure 11). Water there was strikingly more highly mineralized, as indicated
by hardness and alkalinity, than that at any other site (Tables 13 and 14).
This could have resulted from a higher level of sulfate reduction during
oxygenless periods promoted by dissolved organic matter from Lake St. Clair,
with perhaps some contribution from shells and other materials in the satura-
ted ground strata. Oxygen was absent for long periods in deeper water there
in 1974.
Oxygen and hydrogen sulfide—Oxygen declined to 0.0 in only 13 of the 57
groundwater sampling sites (tops and bottoms of water columns are considered
individual sites) but fell to this level in less than 50% of samples from any
38
-------
•53.46
•52.47
.52.07
56.15*
Long Lake
Surface Elevation 49.79
•55.14
51.81
e rated
Stabilization
Pond
36.48*
To Obtain Distance Above Mean
Sea Level Add 130O to
Elevations Listed.
Figure 11. Mean Water
Elevations in Individual
Wells and Long Lake.
39
-------
Long Lake
Derated
Pond
Stabilization
Pond
Figure 12. Groundwater Contours
and Indicated Flow Paths.
40
-------
site, and in only 2 places (Wells 9 and 27) was 0.0 Q£ found at the top of the
water column. Site 27B was oxygenless over a long period, July-August, in 1974
(83% of samples that year) but lacked oxygen in only 24% of samples taken in
1975; however, oxygen was generally quite low there, attaining as much as 1.0
mg/1 in only 13% of samples.
Groundwater was generally higher in oxygen in 1975; maxima for each site
were usually attained that year. Oxygen ranges at individual sampling sites
over the entire sampling period appear in Table 15.
Hydrogen sulfide odor of samples was rated subjectively according to its
intensity (+ if weak, ++ moderate, and +-H- if strong). + and ++ H2S intensi-
ties were sometimes recorded when oxygen was in the 0.1 - 0.5 mg/1 range, but
-H-+ did not occur until 02 was below 0.05 mg/1. Groundwater was frequently
colored orange or gray (not in all wells or in any well at all times), the
orange color when oxygen was substantially present and the gray when it was
absent or nearly so. No iron analyses were conducted, but from the above it
would appear that the orange color represented iron oxide(s) and the gray, iron
sulfide.
Groundwater Seepage into Lakes
Nutrient Concentration—
Water entering seepage collectors in Lakes Sallie and St. Clair in areas
shown in Figures 13 and 16 (1974 and 1975) invariably contained phosphorus and
nitrogen. In St. Clair, total P concentration ranged from 0.27 to 2.10 mg/1
(mean, 1.04 mg/1) and total inorganic nitrogen from 0.90 to 2.337 mg/1 (mean,
1.59 mg/1); whereas, in Lake Sallie, total P range was 0.23 - 7.05 mg/1 (mean,
1.63) and total nitrogen 1.07 - 8.1 mg/1 (mean, 4.00). In seepage water
entering both lakes, NHo-N greatly exceeded the sum of N02- and NOg-N.
Water and Nutrient Loads—
Rate of seepage inflow into either lake varied from day to day and between
different collectors on the same day. Rates measured in 1974 are considered
inaccurate. It was necessary to leave collectors for extended periods (19 -
24 hours), and bag capacity was usually exceeded. Collectors were not operated
longer than 6.5 hours in 1975, and inflow rates so determined are deemed
acceptable. Table 16 shows variation in seepage inflow volume and P and N
loads so brought into each lake.
Nitrate values were omitted when sample volume was insufficient for all 3
N tests.
Measured seepage flow into Lake Sallie is excessive for the entire lake
bottom except possibly on June 27 when the rate of 20 m /hectare/day would
equal the indicated 1975 increment in the lake. With few exceptions, nitrogen
load exceeded phosphorus load into Lake Sallie.
Since the seepage rate into the upper area of this lake is excessive for
the entire bottom, it seems inadvisable to use these volume-area relationships
to compute seepage loads for the whole lake. It is evident, however, that
these lakes gain meaningful quantities of nutrients through their bottoms.
41
-------
One hundred grams/hectare/day would result in 36.5 kg/hectare/year or 32.62
Ibs./acre/year.
PRECIPITATION
Precipitation records represent the following periods and amounts of
rainfall:
Period cm Rainfall Inches Rainfall
1973 May 24 - September 1 31.01 12.21
1974 May 10 - August 15 13.59 5.35
1975 June 4 - August 1 17.30 6.81
Weekly visits to the study area during fall and winter seldom coincided
with periods of precipitation. In summer it was often possible to collect
several samples during the course of 1 rainstorm.
Nutrient Concentration
Phosphorus and nitrogen concentration varied from storm to storm and, over
the courses of individual storms, seldom with any definite pattern. Storms of
short duration tended to show a decline in both phosphorus and nitrogen as they
continued, but this was not without exception, and the downward trend was often
reversed in storms that endured for several hours. Phosphorus was almost
always more concentrated in the unavailable than the available (SRP) form, and
ammonia generally accounted for most of the nitrogen present, rarely being
lower than nitrate (Table 17). Mean concentration of nitrogen was lower in 1975
than in either preceding year, but that of phosphorus higher.
Rain water has been acid to quite acid in reaction, with pH ranging from
5.40 to 3.20. Variation has been common, with values sometimes changing as
much as 0.85 pH during a single storm. Alkalinity has not exceeded 7.5 mg/1,
and hardness has been little higher (10 mg/1), with calcium exceeding magnesium.
All tests for hardness were negative in 1975. Conductivity measurements made
in 1975 ranged from 9.5 to 124 ^imhos/cm, varying from 34 to 79 jumhos/cm in 1
storm.
Nutrient Loads
Table 18 gives load details by date for Lake Sallie, and Table 19 shows
loads contributed to each lake in the upper watershed. The latter are based
upon records acquired near Lake Sallie which are considered reasonably repre-
sentative of the upper watershed.
Phosphorus contributions by precipitation to the total 2,423 hectares of
watershed lake surface were:
42
-------
1973 0.199 kilograms/hectare
1974 0.110 kilograms/hectare
1975 0.318 kilograms/hectare
These quantities are not very impressive when compared with seepage loads
into Lakes Sallie and St. Clair. Precipitation contributed considerably more
nitrogen, and kilograms N/hectare of watershed lake surface were:
1973 4.02
1974 2.07
1975 0.94
which are also rather modest figures with reference to the seepage mentioned
above.
Variation noted in precipitation from storm to storm does not permit an
accurate computation of annual precipitation loads based on mean concentrations
of storms analyzed. These data are considered complete enough, however, to
indicate the general magnitude of nutrient contribution from the atmosphere
and permit comparison with other sources.
Nutrients supplied by summer precipitation to the 12,821 hectare watershed
above Detroit Lake each year were:
Phosphorus Nitrogen
Percent of Total Percent of Total
Metric Tons in Discharge* Metric Tons in Discharge*
1973 2.78 43 53.82 1,987
1974 1.39 39 26.83 741
1975 2.88 29 15.30 398
*Detroit Lake outlet, Station N
Quantity of P dropped on the watershed in summer precipitation was a
fraction of that discharged by Detroit Lake each year, but nitrogen falling in
rain always markedly exceeded the load leaving this lake. The fate of atmos-
pheric N and P on and in the soil of this watershed is unknown. Any that
penetrates to the phreatic zone would be included to some extent in runoff.
43
-------
LAKE CONDITIONS
Lake St. Clair
This small shallow lake (Figure 13) is entirely bordered by cattails which
expand to form a marsh covering peat to the north. The stabilization pond
discharge traverses this marsh enroute to Lake St. Clair. This lake is also
fed by County Ditch #14, which enters from the north and exits to the east, and
the surface outlet from Long Lake. The water level has generally remained
very close to 406.7 m (1,334 feet) above mean sea level, and at this elevation,
volume is 73.7 hm (598 af), surface area 57 ha (141 acres), mean depth 1.3 m
(4.25 feet), and maximum depth 2.29 m (7.5 feet).
Bottom Materials—
In situ, the bottom appeared to be covered with a homogeneous dark, oozy
organic layer which proved to contain varying quantities of marl. Dried
samples from near shore were dark and crumbly with finely divided plant
remnants, snail shells, and sand; but those from near center had the appearance
of gray cement, and their reduction to particle size required grinding in a
mortar. Marl lost to acidification formed 80 - 85% of central lake bottom
deposits but never more than 30% of those near shore.
Nutrient content—Samples (1974) collected near shore contained no
detectable inorganic phosphorus, but those from near lake center had 0.0038 -
0.0225% phosphorus in this form. Total phosphorus, largely organic, comprised
0.185% of littoral sediments and 0.065 - 0.225% of those under deeper water.
Percentage nitrogen was 0.137 - 0.265 for littoral regions and 0.418 - 1.139
for the more highly calcified sediments from the central region. Total phos-
phorus sediment load was 9.80 and total nitrogen was 35.6 metric tons for the
57 ha (141 acres) lake, but only 189 kg of inorganic P (SRP) was present in
bottom materials.
Water Chemistry—
Routine analyses of Lake St. Clair water were from its outlet and are
discussed in other report sections (Station F). Mention shall be made here of
oxygen and pH relationships that appear to accompany algal nitrogen fixation.
Figure 14 shows pH and oxygen levels at Station F over much of 1975 and oxygen
near the lake center from June to August. In March, under ice cover, both pH
and 62 were low, reflecting effects of respiration-decomposition in the absence
of photosynthesis. With the disappearance of ice cover in April, 02 rose to
180% saturation and pH to 8.9, indicating intensive photosynthesis which pro-
duced 02 and increased pH by converting HCOo to CO^. In late May and June,
another pH rise was not accompanied by an equivalent one in £>2 at Station F,
although 02 increase seemed more in line with pH rise at the lake center. In
late June and early July, C>2 decline to winter saturation levels at Station F
did not pull pH down to 8.0, and concentration at lake center was above 100%
saturation. From late July to mid-August, pH level was consistent with that of
02 near the lake center, but 02 at the lake outlet was noticeably below what
would be expected from the indicated photosynthetic effect on pH. In late
August, 02 rose to nearer 100% saturation as pH declined and, thereafter, with
1 exception, followed pH trends. On July 16 and 24, ©2 at the lake center ran
contrary to pH.
44
-------
N
Figure 13
Co. Ditch
From
Long Lake
Co. Ditch #14
To Pelican River
Seepage Collection Areas
0
660' 132Q
Lake St. Clair
8/24/66
Minnesota
Department of Conservation
45
-------
17O-
160-
150-
14O-
13O-
c 120-
o
3ioo-
(55 9O-
i
v
o
80-
50-
4O-
30-
20-
1O-
Figure 14. Oxygen and pH
Lake St. Clair
\—
I I I I I T I I 1 I I I I I
14 21 4 11 25 4 10 23 30 6 12 18 25 2
MAR APR MAY JUN
•9.5
•9.0
•8.5
•8.0
•7.5
•7.0
Q.
9 16 24 28 5 14 19 29 5 12
JUL AUG SEP
1975
3 10 17 24 31 7 14
OCT NOV
-------
5-
CO
E
u
in
O
3-
2-
1-
Figure 15
St. Clair 1975
•fSZ-T
Sa\\\e 1974
6/6 6/11 6/18 6/25 7/2 7/9 7/16 7/24 7/288/5 8/14 8/19 8/258/29 1975
Mean C Fixed Per Hour-8:30AM -2:30PM CDT
Phytoplankton
-------
Since pH normally reflects the relative intensity of photosynthesis and
respiration-decomposition, rising with 02 as the former gains ascendancy and
falling with 0? as dominance swings toward the latter, decline in 02 that is
unaccompanied by an equivalent one in pH indicates oxygen consumption without
or with much reduced C02 production. Since this anomalous pH-02 relationship
has been observed over a number of years only when the autotrophic population
has been dominated or nearly dominated by blue-green algae (usually hetero-
cystous forms), it has been assumed that 02 loss without equivalent pH
suppression reflects 02 consumption in nitrogen fixation. Plankton samples
collected at weekly intervals at Station F over the period May 30 - November 14,
1975, showed dominance by heterocystous blue-green algae (Aphanizomenon and
Anabaena, individually or together) from May 30 through August 14; a slight
dominance by green algae (Closterium and Chlorococcum) August 19, with
Aphanizomenon still abundant; regained dominance by blue-greens from August 29
- September 12; and dominance by greens and diatoms thereafter except for
Aphanizomenon on October 17. These plankton studies will be dealt with in
detail in a forthcoming M.S. thesis and are mentioned here only to verify
involvement of blue-green algae in aberrant pH-02 relationships. If this type
of relationship truly reflects 02 loss to nitrogen fixation (and there seems
no other process to account for it), Lake St. Clair was subject to considerable
nitrogen fixation, which over the years may play a large role in nitrogen
accumulation in bottom sediments. Since routine analyses did not include
procedures for organic nitrogen in water samples, St. Clair N contributions to
County Ditch #14 cannot be estimated.
Primary Production—
This measurement, conducted only for phytoplankton in 1975, indicated a
quite productive situation (Figure 15). Light and dark bottles were suspended
within the 7.0' contour (Figure 13) where 02 levels, at least at 2-hour
intervals, were generally more in accord with pH than at Station F. Nitrogen
fixation may have exaggerated 02 loss to respiration and obscured its gain in
net computations. These 2 sources of error may be compensating, but that
appears speculative at this time.
Macrophytes and their attached algae have produced the largest quantities
of photosynthate in this lake, but their primary production has not been
measured. Navigation through the dense weed growth has been possible only with
a light canoe.
Lake Sallie
Morphometric data for this lake appearing in the 1973 report (1) contained
erroneous measurements that apparently stemmed from planimetering an off-scale
photocopy. Corrected measurements, which also appear in the watershed descrip-
tive section of this report, are as follows:
Area 503 hectares (1,242 acres)
Volume 2,552 hectare meters (20,689 acre feet)
Maximum depth 17 meters (55 feet)
Mean depth 5 meters (17 feet)
A contour map of Lake Sallie is presented here as Figure 16. For other
48
-------
From Fox
Lake
Musk rat
Lake
0 660 1320
SCA N FEET
0 250 5OO
SCALE IN METERS
[Seepage Collection Areas
Figure 16. Hydrographic Map of
Lake Sal lie, Minnesota
-------
morphometric and geological details, the reader is referred to the 1973
report (1).
Thermal Stratification—
Volumes corresponding to plotted contour intervals, and rounded off to the
nearest volume unit, were as follows:
Depth Interval
Meters
0.00 -
1.52 -
3.04 -
4.56 -
6.08 -
9.12 -
12.16 -
15.20+
1.52
3.04
4.56
6.08
9.12
12.16
15.20
Feet
0 -
5 -
10 -
15 -
20 -
30 -
40 -
50+
5
10
15
20
30
40
50
Volume
Hectare Meters
701
563
461
409
371
41
5
1
Acre Feet
5,683
4,564
3,739
3,317
3,010
331
41
8
Thermocline development was usually intermittent. It persisted for longer
periods in 1973, beginning in June, than in 1974 or 1975, but even then was
removed by wind action 3 times before disappearing for good in September. In
1974 a thermocline was present 14 days and in 1975 8 days, beginning in early
July each year. It was usually characteristic for thermoclines to form at or
above mid-depth and then move deeper prior to disappearing. This may be
illustrated by changing volume of hypolimnion shown in Table 20. In 1973,
August and September thermoclines were each of very few days' duration.
Hypolimnions seldom amounted to noteworthy percentages of lake volume.
Reference to the depth-volume table above will indicate approximate depth of
the hypolimnion on each listed date. In early June, 1973, its upper surface
fell from 5 to 11 meters and from late June to mid-July from 4 to 7 meters.
Winter stagnation occurred each year in the usual fashion. Full circula-
tion usually began with the end of ice cover in April and endured until June
or July.
Bottom Materials—
The bottom of Lake Sallie is composed of sand overlaid with varying
quantities of organic materials and marl. In deeper areas (Figure 17) sand
comprises 25% or less of superficial sediments (upper 15 cm) whereas along the
lake margins it makes up 75%.
50
-------
Muskrat Lake
]>75 % Sand
ll<25 % Sand
Figure 17. Bottom Sediments
in Lake Sallie
51
-------
Nutrient Loads—In 1974 sediment samples represented the upper 15 cm (6")
and 4 depth
Depth
m
0-3.04
3.04-6.1
6.1-9.14
9.14-12.2
12.2-15.2
15.2+
Totals
zones .
Zone
Feet
0-10
10-20
20-30
30-40
40-50
50+
Details and nutrient loads wei
ha
181
68
225
26
2
1
503
Acres
447
169
556
63
5
2
1,242
Mean Weight per
0.093 m2 (1 ft2)
2.49 kg
1.39 kg
0.94 kg
-
-
0.69 kg
—
Metric Tons
N Total P SRP
111 30 6
69 61
77 14 3
0.02
257
0.037 0.007
50 10
In terms of quantity per hectare, Lake Sallie had 82% of the N and 58% of
the total P sediment loads of Lake St. Clair; however, its inorganic P (SRP)
was 6 times as great.
Specific gravity of bottom sediments declined with depth as organic matter
and marl became more prominent constituents. Concentration of soluble reactive
phosphorus (SRP) was greatest where sediment density was lowest and organic
debris highest and lowest in areas of intermediate density where marl was most
common. Total P was most concentrated in regions with largest marl deposits
and less abundant near shore and in deepest lake regions. This makes it appear
that calcium, or processes related to its deposit, reduce phosphorus availabil-
ity and that C02 production enhances it. Percent total N, total P, and SRP in
sediments of each of the 4 lake regions was:
Depth Zone
0.00-3.04 m
3.04-6.10 m
6.10-9.14 m
15.20+ m
Percent
Total N
0.23
0.068
1.15
0.904
Percent
Total P
0.026
0.08
0.08
0.033
Percent
SRP
0.015
0.012
0.011
0.053
Predominant
Bottom
Constituent
Sand
Marl
Marl
Organic debr
Nitrogen appeared to accumulate more in deeper lake sediments and did not seem
influenced by marl.
52
-------
Weed growths-Weed growth declined in 1971 following initial harvest in
1970 (1) and again in 1972 following 1971 harvest. In 1973 and 1974, the
weed harvester recovered such small quantities that it was operated only for a
few days each year, but in 1975 higher water level permitted it to operate in
lake areas it had previously been unable to enter, and a sizable quantity of
weeds was removed. During all 4 years attempts were made to relate weeds
removed to the areas shown in Figure 18. This was successfully done for the
first 3 harvest years; but in 1975, Areas 2 and 3, 5 and 6, and 7, 8 and 9
were harvested together. This was dictated largely by economic factors, and
the groupings used confined operations to a definite lake region in each case.
Quantities removed from each area each year in kilograms were:
Area
1
2
3
1970
97,853
138,119
105,351
1971
6,578
1,928
31,477
1972
2,645
1,418
24,523
1975
2,080
15,837
5,770 1,850 0 2,702
5
6
7
8
9
19,856
47,430
673
3,336
9,616
54,711
14,520
0
0
0
12,191
18,711
0
0
0
19,700
420
Total 428,004 111,064 59,488 40,739
Since a large part of the area harvested in 1975 was too shallow to be reached
by the harvester in preceding years, the full effects of suppression by
previous harvests are masked.
The most productive area (Area 2) in 1970 exhibited a sharp decline in
1971 and 1972 and probably fared no better in 1975. The more productive areas
of 1971 and 1972 retained this status in 1975, and Areas 4, 7, 8, and 9 pro-
duced weeds in 1975 after being barren for 1 or 2 of the previous harvest
years. Kilograms of phosphorus removed in weeds showed a steady decline over
the 6-year period, despite the fact that new areas were included in the 1975
harvest. Mean total phosphorus concentration varied from 0.25 - 0.39% of dry
weed weight and mean total N concentration from 0.27 - 0.29%. Values for N
appearing in the 1973 report (1) have not been repeated; and, in view of the
reproducibility of later analyses, now appear too high. Kilograms of P and N
53
-------
Muskrat
Lake
From Fox
Lake
Pelican
River
Figure 18. Weed Harvest Areas
in Lake Sal lie
-------
removed with each year's harvest were:
P N
1970 100
1971 26
1972 17 11.56
1975 10 8.50
As previously indicated (1), weed harvest offers no promise as a nutrient
reducer, but it does appear to exercise long-term control over weed growth.
Continued weed removal was associated with some qualitative changes in the
macrophyte population. Potamogeton crispus L., which occurred only as isolated
individuals in 1969-71, grew densely in pure stands over large bottom areas in
1972 and later. Vallisneria and Ruppia were conspicuous during early harvest
years, but the former became quite rare in 1972 and the latter in 1975. In
1972 and 1975, harvester hauls were dominated by CeratophyHum, Myriophyllum,
and Potamogeton pectinatus, and relative abundance of these 3 varied in
different areas.
Water Chemistry—
pH—As mentioned previously (1), surface water in the limnetic zone has
been characterized by a high pH over most of the year. This has been largely
attributed to a high summer photosynthetic level and the low volume of decom-
position zones in Lake Sallie, but photosynthesis under ice has also been
noted. In February, 1973, pH and oxygen both indicated the occurrence of
photosynthesis in the upper limnetic zone (Figure 19) . This was not suggested
by data for the next 2 winters when pH was noticeably lower (Figures 20 and 21) .
Weekly records may often fail to show peak conditions, and it appears that in
the past photosynthesis was not awarded due credit for higher pH levels under
ice.
Oxygen—Very low or 0.0 oxygen values have been noted only in deep waters
of the limnetic zone during summer and winter stagnation periods. In 1973,
0.0 concentration occurred in the hypolimnion in July and August, but the
winter minimum observed was 0.25 mg/1 in early March. In 1974, 0.0 was ,noted
in July and 0.25 mg/1 in late March, but in 1975 there were no 0.0 values
recorded, and the winter minimum was 1.21 mg/1.
Association of generally high pH with some low oxygen records in summer of
1974 and 1975 indicate the occurrence of algal nitrogen fixation in the limnetic
zone and lake outlet (Figures 20 and 21), with the discrepancy more marked in
1975. It is believed that sampling at hourly intervals would be much more
diagnostic of this phenomenon.
Intra-lake nitrogen, phosphorus, hardness, and alkalinity relationships
were similar to those given in 1973 (1) and will not be detailed here.
55
-------
9.0-1
8.CH
E
o.
a.
6
1O-
5-
Sta. 8
Sta. 4
0-
Figure 19. Oxygen and pH, Lake Sallie
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV
1973
-------
o
130-1
120-
110-
100-
90-
80-
(/)
60-
50-
40-
30-
20
10
0
Sta. 4 pH
Sta. 8 O2
Sta. 8 pH
Figure 20. Oxygen and pH, Lake Sal lie
v
9.0
SO
75
CO
V
I
a
•7.0
18 1 12 20 26 5 11 18 12 18 26 3 10 19 24 31 8 14 21 28 22 29 6 20 28
JAN MAR APR MAY JUN JUL AUG NOV DEC
1974
-------
9.0-
8.5-
8.0-
7.5-
00
140-]
13CH
§120,
jo 110-
B 100-
M 90-
^ 80-
81 70-
§ 60-
50-
40«
Figure 21. Oxygen and pH, Lake Sallie
Sta. 4-1
Sta. 8
24 31 14 21 7 14 28 4 13 20 26 3 10 17 23 29 7 15 21 30 5 13
JUL AUG SEP
1975
JAN FEB MAR MAY JUN
4 11 18 25 1
OCT
8 15 22 28 5
NOV DEC
-------
Primary Production<~~
Lake Sallie had a lower rate of carbon fixation by phytoplankton than
Lake St. Clair and generally had a higher rate in 1975 than in 1974 (Figure 15).
Greater carbon fixation in July and August of 1975 may have resulted from
lowered competition provided by removal of weeds and attached algae in June and
July. Measured rates indicate a quite productive phytoplankton situation each
year.
WATERSHED PHYTOPLANKTON
Quantitative aspects of individual phytoplankton analyses covering the
period May 30 - November 21, 1975, appear in Table 21 . Station 4-1 is surface
water near the center of Lake Sallie.
In order of declining production the stations may be ranked A, F, 4-1, 8,
B, P, N, and M. Productivity of the aeration pond (A) was as would be expected
from its nutrient content, and its greater average depth; but phytoplankton in
the stabilization pond (B) failed to closely approach its nutrient potential
until November when high concentrations coincided with high density in A. Study
of Table 21 will suggest that B's long period of low productivity did not result
from growth in A, and this appears true since plankton in B was suppressed by an
extensive and luxuriant growth of duckweed (Lemna minor and L_. trisulca) which
was invaded in some areas by an alga (Rhizoclonium sp.) in late August. Density
of this surface cover was great enough to form a firm walking surface for shore
birds and smaller waterfowl. About 85% of the total surface area was occupied,
and interference with light penetration was very great.
Lake St. Clair (F) did not live up to the phytoplankton potential inherent
in its nutrient loading, but there plankton had to compete with a very dense
weed growth. Very dense and extensive growths of weeds, Chara, and other
attached algae present in Detroit Lake were considered to be its primary auto-
trophic populations.
Phytoplankton productivity in Muskrat Lake, measured at Station 1, also
seemed to be overshadowed by dense growths of rooted and attached vegetation, and
its plankton increase above that of inflowing water (at P) speaks for its basic
high productivity. Phytoplankton in Lake Sallie, although at times achieving
rather respectable numbers as compared to the aeration pond (A), had to contend
with light occlusion by dense surface drifts of blue-green algae that persisted
for weeks. Competition from attached vegetation was reduced by weed harvest
over the period June 28 - July 29, 1975, which included areas previously too
shallow for operation of the harvester. The wind-accumulated blue-green algae
produced nuisance conditions, but they also lowered photosynthate production.
Phytoplankton has varied qualitatively with location and season, In 1975
dominance in the aerated pond alternated between green and non-heterocystous
blue-green algae (Chroococcus) over the year; the stabilization pond plankton
was dominated by green algae and diatoms except on 2 dates when blue-greens
were predominant; Lake St. Clair, with 1 exception, had heterocystous blue-
green algae greatly outnumbering all other groups; the Pelican River above
Detroit Lake (Station M) had diatoms predominant in all samples; in Detroit Lake
59
-------
dominance varied among diatoms, green algae, and Chrysophyceae, except on 3
dates when Chroococcus gained slight numerical superiority; in Muskrat Lake
diatoms and greens were most numerous until June when heterocystous blue-greens
assumed and retained dominance until October 4, except for a brief period in
August when they were briefly replaced by diatoms, and diatoms and greens came
to the fore again from October - December; and Lake Sallie was dominated by
heterocystous blue-greens from early July until December, with greens and dia-
toms predominant from January - June. The 2 Floyd Lakes were dominated by hetero-
cystous blue-green phytoplankton in 8 weeks spread over July, August and October.
TROPHIC STATE INDEX
A criterion that will reliably indicate lake productivity level or trophic
state is being sought. Articles on the subject tend to either offer a number
of choices (12) or to be limited to the activity of a single biotic segment
(13). Productivity is regulated by nutrient supply, but conditions in a water
body may forestall attainment of productivity inherent in available nutrients.
A workable trophic state index (TSI) would need to reflect total autotrophic
activity realized over a given time period, which would entail encompassing
the activities of all 3 autotrophic populations, plankton, macrophytes, and
periphyton, or as many as are present.
Development
For more than 20 years this author has noted a reversal of normal back-
ground Mg/Ca quotients in highly productive standing water bodies. This was
especially noticeable in raw sewage lagoons or stabilization ponds where a
sewage Mg/Ca quotient of 0.40 - 0.50 would change to 2.00 or more in the very
actively photosynthesizing pond liquor. The increased ratio in the ponds came
about through reduction of calcium, which precipitated as CaCOo when much or
all bicarbonate was converted to normal carbonate by phytoplankton. Magnesium
carbonate, being much more soluble, left solution to a much lesser extent;
magnesium concentration of sewage generally showed little change in ponds.
Calcium and magnesium (hardness) were considered not particularly relevant to
objectives of stabilization pond experiments and were measured only occasion-
ally, despite their relationship to photosynthetic accomplishment. The Mg/Ca
quotient was kept in mind, however, and later used as an indication of produc-
tivity level in comparison of 2 or more lakes.
Work on the Detroit Lakes area eutrophication project, after expansion
from Lake Sallie, has shown that the Mg/Ca ratio may be used to develop a TSI
that so far has -reflected productivity conditions in the lakes and ponds
involved. This index was developed as follows.
The stabilization pond, Lake St. Clair, Lake Sallie, and Detroit Lake all
had higher mean Mg/Ca quotients in their outflows than in their major inflows,
regardless of events in the preceding water body(ies). Figures 22, 23, 24 and
25 show that higher Mg/Ca values characterized outflows from these water bodies
"at all times in the case of Detroit Lake and practically all the time in the
other 3. The stabilization pond, Lake St. Clair, and Lake Sallie all received
inflow from situations that frequently or generally supported intense photo-
synthesis, yet they continued to reduce calcium and increase the Mg/Ca quotient.
60
-------
2.0
CT (TJ
M u
1.5
D)
1.0
Q5
Figure 22. Mg/Ca Quotient Variation,
Aeration and Stabilization Ponds
Stabilization^ Pond
Aeration Pond
JFMAMJJASOND
1975
-------
2.0-
(TJ
-------
2.0
1.5
OJ
U
O)
1.0
O5
V>X.s_J
Figure 24. Mg/Ca Quotient Variation,
Detroit Lake Inlet and Outlet
JFMAMJJASOND
1975
-------
2.0
cu
u
1.5
D)
1.0
Q5-
Figure 25. Mg/Ca Quotient Variation,
Lake Sallie Inlet and Outlet
Lake Sallie Outlet
M
M
J J
1975
O N D
-------
Increase of the Mg/Ca quotient thus appeared to reflect level of photosynthate
formation during residence and this led to application of the following
formula :
= TSI
In which: 0 = Mean Mg/Ca quotient in outflow
I = Mean Mg/Ca quotient in inflow
R = Residence or detention time in years
Experience with these lakes suggests that means desirably should be based on 12
consecutive months' data, to include all annual events such as stratification,
full circulation, ice cover, etc. Our data show variation from week to week
to be the general pattern, and it appears that sampling every 2 weeks would be
near the minimum frequency for best results. Delay in annual funding caused a
gap of 2 months in 1974 data (September - October), but records acquired that
year indicated similar Mg/Ca relationships to those acquired at weekly inter-
vals in 1975. Routine collection of Ca and Mg data began in June, 1974, and
continued through August, 1976; but since discharge data are available only
through June, 1975, the period June, 1974 - June, 1975, is alone considered in
computation of TSI's. Detention time in each lake is based upon volume of
outflow.
Values for the stabilization pond (Station B) were:
0 0.54
I 0.48
R 0.09 years
Thus: 0.54 - 0.48 = Q ,?
0.09
TSI's for the 4 bodies were;
Stabilization pond 0.67
Lake St. Clair 2.90
Detroit Lake 0.27
Lake Sallie 0.27
When TSI's were computed from the means of chemical records for the 18
month period, June, 1974 - December, 1975, and average water residence times
over the period January, 1973 - June, 1975, the following values were obtazned:
Stabilization pond 2.67
Lake St. Clair 2.80
65
-------
Detroit Lake
0.35
Lake Sallie
0.27
Relationship to Nutrient Loading and Local Conditions
TSI values appearing above were not consistent with nutrient loading as
shown below, but they were indicative of relative amounts of photosynthate
produced in each lake. From its nutrient loading, the stabilization pond
would be expected to be much more productive than Lake St. Clair, but during
most of the growing seasons of 1974 and 1975 up to 85% of its surface was
densely covered with duckweed which restricted light supply to underlying
water and largely limited photosynthate production to neuston over most of the
growing season. Plant growth was also deterred by frequent water level changes
in 1975. Duckweed in Lake St. Clair was minimal along margins and had no
noticeable effect on macrophyte and plankton growth.
Nutrient Loading, kg/ha/day
Stabilization Pond Lake St. Clair Detroit Lake
1973
1974
1975
P
3.54
1.81
6.74
N
5,77
3.90
5.81
P
0.50
0.34
0.58
N
0.36
0.54
0.56
P
0,016
0.012
0.045
N
0.008
0.012
0.026
P
0.069
0.062
0.104
CJcliiifci
N
0.042
0.069
0.117
q,-n -K nutrient loadings, had a higher TSI than Lake
Sallie but during 1974 and 1975 Lake Sallie exhibited dense accumulations of
drifted blue-green algae that blocked light penetration through extensive areas
of water surface and was also subjected to weed harvest that removed consider-
So far11^1^ TV a"ached veSetati™ by the middle of the 1975 growing season.
fin* ; K T T" produced bl«e-green phytoplankton in any noticeable
quantity but, as previously mentioned, has produced dense growths of rooted and
attached plants.
The earth fill dam which forms the 26-hectare (65-acre) impoundment known
and whiTh %,1S ^"f "f ^ S6epage that WaS measured in UPP^ Lake SalUe
and which has often produced wet surface soil on land areas below the dam
Measurement of Ca and Mg was rather spotty at the Muskrat Lake inlet (Station P)
^ ,1 ,* N WaS r°Utine W±th °ther stations ** 1975. Nutrient loadings
(kg/ha/day) were: &
N
1973
1974
1975
1.49
1.21
1.01
1.24
1.32
0.91
66
-------
Mean detention time was 0.016 years, and the Muskrat Lake TSI for 1975 based
on this figure was 1.875. Most growth was by macrophytes and attached vege-
tation. Mean phytoplankton density was about 33% of that in Lake Sallie.
Since this method of indicating productivity level embraces all auto-
trophic elements, plankton, periphyton, and macrophytes, it is hardly
justifiable to check its validity against the development and/or activity of a
single autotrophic population, e.g., phytoplankton. However, in the 2 lakes
subjected to detailed study (Sallie and St. Clair) primary production by phyto-
plankton was considerably more intense with the higher TSI (Figure 15).
Relation to Varying Hardness
May the Mg/Ca quotient system be applied to lakes with greater Mg and Ca
with like results? In the Pelican River watershed annual mean hardness has
ranged from 20A to 302 mg/1. In 1972 mean annual hardness in Main Bay of the
recently rewatered Devils Lake chain in North Dakota was 1,045 mg/1. With a
calculated water residence time of 6.3 years its TSI was 0.55, which appears
reasonable when its TSI and biota are weighed against those in the Pelican
River lakes. Its phytoplankton was quite dense (mean concentration 30,000
cells/ml) and its weed growth was comparable to 1974-75 populations in Detroit
Lake, in which mean phytoplankton density in 1975 was 395 cells/ml. Over the
years Main Bay has produced great quantities of fish food (15).
Another question is: Does the Mg/Ca based TSI hold true when noncarbonate
compounds of Mg and Ca (noncarbonate hardness) greatly exceed Ca and Mg
carbonates? The answer appears to be yes. In Lake Sallie in 1975 noncarbonate
hardness exceeded carbonate hardness by only 16 mg/1, but in Main Bay of Devils
Lake in 1972 noncarbonate was 557 mg/1 greater than carbonate hardness. Within
these ranges, at least, use of the Mg/Ca ratio seems to discount such
differences.
General Considerations
It has been pointed out elsewhere in this report that about a year is
required for groundwater to appear in surface streams and lakes in this study
area. In 1973-74 mean Mg concentration in PC well sites, omitting No. 27, was
114 mg/1, and in 1975 its mean concentration in the Lake Sallie outlet was
115 mg/1; whereas mean calcium was 214 mg/1 in 1974 for the wells and 91 mg/1
in the Lake Sallie outlet. This illustrates removal of Ca and lack of change
in Mg. Since evaporation exceeds precipitation by about 25 cm (10 in.) per
year, it is assumed that groundwater values represent general inflow into lakes.
The stabilization pond, Lake St. Clair, and Muskrat Lake are 3 highly
trophic situations with nutrient loadings that are probably rarely if ever
duplicated in larger water bodies. Their very high TSI's are considered beyond
the range of natural or the great majority of culturally enriched lakes; and,
while TSI's in their range would indubitably indicate water bodies with severe
eutrophication, problem lakes are produced with TSI's of a much lower level.
Data recorded here suggest that troublesome or potentially troublesome quanti-
ties of photosynthate are being produced when the TSI approaches 0.25, but the
limited number of lakes represented dictates that caution be exercised at this
67
-------
time in assigning critical thresholds. TSI's based on Mg/Ca quotients show a
broad positive relationship to nutrient loading in these water bodies, e.g.,
those with a P loading of 0.47 - 4.03 kg/ha/day have considerably higher TSI's
than those within the 0.024 - 0.078 kg/ha/day range. However, there was
variation within each of these ranges that suggests influences of conditions in
individual water bodies.
Data on these waters indicate that lake conditions are overshadowed by
loading differences approaching an order of magnitude, but Working Paper No.
474, compiled by the U.S. Environmental Protection Agency, November, 1975 (16),
suggests that loading is much less influential. P loadings reported for 168
lakes and reservoirs placed in 4 trophic level categories were as follows:
Loading Range
Category No. Lakes gms P/m^/yr
Hypereutrophic 8 0.19 - 261.49
Eutrophic 128 0.06 - 817.68
Mesotrophic 21 0.04 - 1.34
Oligotrophic 11 0.03 - 0.51
Several lakes included in the EPA report lacked loading data. Minimum P
loading noted for the Pelican River lakes, 0.024 kg/ha/day, is equivalent to
0.876 gms/nrVyr. Since the 4 trophic categories used by the EPA tend to reflect
opinion more than a calculable relationship, loading may be more influential
than their data indicate.
An impression gained from the Pelican River data is that other elements
may become more limiting than N and P to photosynthesis. When wastewater
effluent is involved, these elements are usually more abundant with N and P,
and their influences may erroneously suggest positive effects of N and P with
increases above their influential range. Muskrat Lake's having a higher P
loading and a lower TSI than Lake St. Clair lends support to this impression,
as inflow into Muskrat Lake has a much lower percentage of the wastewater
effluent, despite its higher P loading, much of which has come from Detroit
Lake.
No attempt is being made at this time to assign TSI values or ranges to
denote historical trophic state designations, e.g., eutrophic, mesotrophic, etc.
This may not be desirable, since, if the TSI considered here proves generally
applicable, a single number will suffice to show productivity level. Regardless
of its general applicability, this TSI is expected to be very valuable in
assessing productivity changes in these lakes, and it should find similar uses
elsewhere. It may not be generally useful to indicate specific state of degrad-
ation since this frequently depends upon type as much as quantity of plant life;
however, it appears applicable to ascertainment of potential.
Procedural modifications may be required for (1) lakes with large and
persistent hypolimnia in which full circulation could restore much photosynthet-
68
-------
ically precipitated calcium, (2) reservoirs with extended hypolimnion
discharges, and (3) lakes lacking surface outlets. In the first instance an
acceptable evaluation may possibly be gained by considering only the time
interval from the beginning of spring circulation to just before the disappear-
ance of the hypolimnion in autumn. For the second and third situations if
residence time can be rather accurately estimated, near surface sampling
within the water body may permit detection of changes helpful in determining
realistic productivity estimates. Groundwater near Long Lake (Figure 1) at
times demonstrated Mg/Ca change indicative of exposure to a photosynthetic
environment, but, although this occurrence could show lake discharge to the
ground, it is questionable that it could be used as a dependable indication of
lake discharge quality. This TSI procedure may also encounter problems in
application to soft water lakes.
69
-------
REFERENCES
1. Neel, J.K., S.A. Peterson, and W.L. Smith. Weed harvest and lake nutrient
dynamics. U.S. Environmental Protection Agency, Report No. EPA-660/3-73-
001, 1973. 91 pp.
2. Miekicki, S.J. Pattern of watershed enrichment and its effects on nutrient
budgets and weed growth in a culturally eutrophied lake. MS Thesis.
University of North Dakota, Grand Forks, North Dakota. 1973. 122 + xii pp.
3. Brakke, D.F. Weed harvest effects on algal nutrients and primary production
in a culturally enriched lake. MS Thesis. University of North Dakota,
Grand Forks, North Dakota. 1974. 83 + x pp.
4. Peterson, S.A. Nutrient dynamics, nutrient budgets, and weed harvest as
related to the limnology of an artificially enriched lake. Ph.D. Disserta-
tion. University of North Dakota, Grand Forks, North Dakota. 1971.
210 + xvii pp.
5. Smith, W.L. Plankton, weed growth, primary productivity, and their relation
to weed harvest in an artifically enriched lake. Ph.D. Dissertation.
University of North Dakota, Grand Forks, North Dakota. 1972. 222 + xv pp.
6. Lee, D.R. Septic tank nutrients in groundwater entering Lake Sallie,
Minnesota. MS Thesis. University of North Dakota, Grand Forks, North
Dakota. 1972. 96 + x pp.
7. Lee, D.R. A device for measuring seepage flux in lakes and estuaries.
Limnol. & Oceanog. 22:155-162. 1977.
8. American Public Health Association. Standard Methods for the Examination
of Water and Wastewater—13th ed. Washington, 1971.
9. Krawczyk, D.F. Analytical techniques for the national eutrophication
research program. Fed, Water Poll. Control Admin., Pacific Northwest Water
Lab. 1969. 141 pp.
10. Strickland, J.D.H. and T.R. Parsons. A manual of seawater analysis.
Fisheries Research Bd. of Canada, Bull. 125. 1965. 185 pp.
11. Mann, W.B. IV and M.S. McBride. The hydrologic balance of Lake Sallie,
Becker County, Minnesota. U.S. Geol. Sur. Prof. Paper 800-D. 1972.
pp. 189-191.
70
-------
12. Hooper, F.F. Eutrophication indices and their relation to other indices
of ecosystem change. Nat'l. Acad. Sci. Symposium, Eutrophication: Causes,
Consequences, Correctives, pp. 225-235. 1969.
13. Carlson, R.E. A trophic state index for lakes. Contribution 141, Limnol.
Res. Center, Univ. Minnesota. 17 pp. 1975.
14. Neel, J.K. Limnological characteristics of the Devils Lake chain,
effects of recent rewatering, and projected influences of Garrison
Diversion. Report to U.S. Bureau of Reclamation. 1974. 51 + vii pp.
45 tables, 64 figures.
15. Young, R.T. The life of Devils Lake, North Dakota. Publication of the
North Dakota Biological Station. 1924. 116 pp.
16. U.S. Environmental Protection Agency. A compendium of lake and reservoir
data collected by the Nat'l. Eutrophication Survey in the Northeast and
Northcentral U.S. Working Paper No. 474. 1975. 210 pp.
17. Stambaugh, J.W., Jr. Phytoplankton variation over the upper Pelican River
watershed, Becker County, Minnesota. MS Thesis. University of North
Dakota, Grand Forks, North Dakota. 1977. 114 + x pp.
18. West, W.M. Chlorophyll densities and plankton counts as measurements of
phytoplankton biomass. MS Thesis. University of North Dakota, Grand
Forks, North Dakota. 1977. 55 + viii pp.
71
-------
APPENDIX
University of North Dakota
MS Thesis
Pattern of Watershed Enrichment and Its Effects on
Nutrient Budgets and Weed Growth in a
Culturally Eutrophied Lake
Stanley J. Miekicki
Abstract
This study localized major nutrient sources along the Pelican River and
evaluated their effect on nutrient budgets in Lake Sallie, Minnesota. Conse-
quences of weed harvest on nutrient removal were also studied. Data included
chemistry of water, sediments, and aquatic macrophytes.
Weekly analyses from June 1972 - May, 1973, showed nutrients to be most
concentrated at stations below entry of sewage effluent from the city of
Detroit Lakes, Minnesota. Nitrogen concentrations were lowest during the
growing season with highest levels occuring from December to March. Levels
fell in March and April when warm weather returned. Phosphorus levels were
also lowest in summer. A steady increase in both ortho- and total phosphorus
occurred from December to March. This buildup was also depleted when warm
weather and photosynthesis increased.
Sediment samples taken from June - August, 1972, in Lake Sallie showed
phosphorus and nitrogen to be most concentrated under deep water.
Over the period July 11 - September 18, 1972, 15 kg of phosphorus and
12 kg of nitrogen were removed in 59,487 kg of weeds harvested in Lake Sallie,
quantities far below those removed in 1970 and 1971. Cost per kilogram of
nutrients removed was greater than in 1971, and weeds contained less nitrogen
than in 1970 or 1971.
Macrophyte growth in harvest areas declined over 1970, 1971, and 1972,
and abundance of some individual species changed. Lesser amounts of nitrogen
entered the lake in July, 1972, which could have slowed weed growth.
72
-------
Removal of weeds and fish appears inadequate to reduce nutrients to any
meaningful extent in a lake unless more nutrients than enter the lake are so
removed. This has not been possible in Lake Sallie, and the major hope for
recovery of this lake is curtailment of nutrients it receives via the Pelican
River.
73
-------
University of North Dakota
MS Thesis
Weed Harvest Effects on Algal Nutrients and Primary Production
in a Culturally Enriched Lake
David F. Brakke
Abstract
This study evaluated lake chemical and physical conditions and primary
production by phytoplankton during and following large-scale aquatic plant
removal. Data cover the final year of weed harvest (1972) and the first year
following (1973).
Summer stagnation developed, disappeared and reformed each year. The
photosynthetically important limit of light penetration moved upward from June
to August, 1972, when it was at 2 meters or less. Red light reached greater
depths than green in early summer and less thereafter. Incident radiation
varied between 20 and 484 langleys/day. Phosphorus levels were higher in 1973;
total phosphorus maximum at 9 meters was 2.30 mg/1. Ammonia was depleted in
surface water each summer; maximum concentration (3.10 mg/1) was reached at 9
meters under ice. Anoxic conditions developed under stable thermoclines and in
deeper water in winter.
Phytoplankton photosynthesis and respiration increased from 1972 to 1973.
Both were greatest in August. Maximum gross primary production was 780 mg
C/nr/hr. Considerable daily and seasonal variation was found at all depths.
Production increase in 1973 was greatest at 0.5 meters. Photosynthetic decline
at mid—day was common on clear days; increases were frequent with overcast.
Greatest photosynthetic efficiency, mgC/m /hr
langleys/hr, was in August (maximum, 34.98)
when bloom conditions developed and incident radiation declined.
74
-------
University of North Dakota
MS Thesis
Phytoplankton Variation Over the Upper Pelican River
Watershed, Becker County, Minnesota
John W. Stambaugh, Jr.
Abstract
Those parts of the upper Pelican River watershed, Minnesota, that have
been affected by wastewater elements have experienced nuisance growths of
blue-green algae from time to time. This study considers growth of phyto-
plankters in lakes and stream reaches of the upper watershed in 1975 and
relates their composition and abundance to nitrogen and phosphorus concentra-
tions. Phytoplankton biomass expressed as numbers generally agreed with its
volume but did not in computing percent composition of the major algal groups.
Diversity, as number of genera, could not be correlated with nutrients of
wastewater origin, because it was influenced by many variables.
Nitrogen/phosphorus ratios, calculated for all sample sites, were usually
very low, around 1. Correlations claimed for low N/P ratios and growth of
heterocystous blue-green algae by Schindler were not substantiated by this
study.
75
-------
University of North Dakota
MS Thesis
Chlorophyll Densities and Plankton Counts
As Measurements of Phytoplankton Biomass
William M. West
Abstract
Water bodies in the Pelican River watershed, Minnesota, showed seasonal
trends in phytoplankton populations over 1975-76. Lake Sallie was dominated
by green algae in late spring, diatoms in early summer, blue-greens from July
through early winter, and a mixed diatom and green algae population from late
winter through early spring. Blue-greens were poorly represented in samples
from sewage aeration and stabilization ponds. Errors associated with plankton
counting were found to be about 10%. The pigment extraction method does not
permit computation of a percentage error. Comparison of plankton counts and
chlorophyll densities indicates that the latter may not be depended upon for
accurate biomass estimates on any given date. There are a number of problems
in chlorophyll procedures that need be remedied.
76
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TABLE 1. MAGNITUDE FEATURES OF LAKES AND PONDS
Maximum
Surface Area Volume Depth Mean Depth
Hectares
Floyd Lake
Little Floyd Lake
Detroit Lake
Lake St. Clair
Long Lake
Muskrat Lake
Lake Sallie
Aerated pond
Stabilization pond
397
83
1,185
57
172
26
503
1
10
Acres
980
206
2,928
140
426
65
1,242
3
25
Hectare
Meters
1,554
434
5,648
74
897
42
2,552
2
3-8
Acre
Feet Meters
12,604
3,520
45,800
598
7,277
341
20,689
20
23-69
11
11
24
2
15
5
17
—
—
Feet
36
35
80
7
50
15
55
—
—
Meters Feet
4
5
5
1
5
2
5
2
<:L
13
17
16
4
17
5
17
7
1-3
Values are to nearest whole units.
One hectare meter equals 10,000 m3 or I hectare x 1 m (8.10835 acre feet).
77
-------
TABLE 2. DISCHARGES AT SELECTED POINTS IN THE UPPER PELICAN RIVER WATERSHED
1973
1974
1975
Totals
hm
af
hm
af
hm
af
hm
af
A
143
1,156
127
1,030
63
508
333
2,694
B
100
810
89
723
44
357
233
1,890
F
622
5,044
752
6,095
457
3,703
1,831
14,842
N
2,514
20,383
2,544
20,629
1,450
11,755
6,508
52,767
F + N
3,136
25,427
3,296
26,724
1,907
15,458
8,339
67,609
1
2,650
21,491
3,240
26,275
2,365
19,179
8,255
66,945
8
3,155
25,580
3,446
27,942
2,552
20,691
9,153
74,213
hm = hectare meters
af = acre feet
1975 records January - June only
78
-------
TABLE 3. INDIVIDUAL WELL FEATURES
VO
Well
PC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Bottom
Kiev.
38.74
24.33
34.09
37.59
25.48
25.66
16.69
38.72
45.29
44.11
34.34
47.34
51.59
46.21
38.49
31.89
29.46
Mean
Water
Level
Elev.
43.77
51.22
43.57
41.19
42.68
42.29
41.95
40.30
49.37
46.19
47.52
51.15
56.15
49.08
44.91
39.52
51.50
Mean Depth
Water Column
Feet Meters
5.03
26.89
9.48
3.60
17.20
16.63
25.26
1.58
4.08
2.08
13.18
3.81
4.56
2.87
6.42
7.63
22.04
1.53
8.20
2.89
1.10
5.24
5.07
7.70
0.48
1.24
0.63
4.02
1.16
1.39
0.88
1.96
2.33
6.72
Length
Above
Feet
10
30
20
10
20.5
20
5
10
10
10
17.5
6
6
10
12
10
28
Screen
Bottom
Meters
3.04
9.15
6.10
3.04
6.25
6.10
1.52
3.04
3.04
3.04
5.33
1.83
1.83
3.04
3.66
3.04
8.54
Water Column In:
Brown over gray till
Sand and gravel over sand over sand
gravel
and
Sand over gravel over brown and gray till
Brown and gray clayey till
Gravel over sand and gravel over gray till
Sand and gravel, lower 0.76 m gray
till
Sand and gravel, lower 0.3 m gray till
Tan and gray till
Tan and gray till, gray clayey
Sand and gravel over gray till
Sand and gravel over gray till
Sand and gravel over silt and brown
gray till
Brown silt over gray till
Sandy silt over brown and gray till
Sand and gravel over gray till
Sand and gravel over gray till
Sand over fine sand over gray till
and
(continued)
-------
TABLE 3. (continued)
oo
o
Well
PC
18
19
20
21
22
23
24
25
26
27
28
29
30
Bottom
Elev.
45.47
50.74
25.56
19.37
32.42
26.59
25.68
21.70
26.39
19.09
16.67
10.90
28.84
Mean
Water
Level
Elev.
55.14
53.46
52.07
51.39
50.97
43.13
42.64
39.72
39.42
34.55
36.12
36.48
44.19
Mean
Water
Feet
9.67
2.72
26.51
32.02
18.55
16.64
16.96
18.02
13.03
15.46
19.45
25.58
15.35
Depth
Column
Meters
2.95
0.83
8.08
9.76
5.66
5.04
5.17
5.49
3.97
4.71
5.93
7.80
4.68
Length
Above
Feet
10
10
30
34
25
26
20
22
18
20
20
27
20
Screen
Bottom
Meters
3.04
3.04
9.15
10.36
7.62
7.93
6.10
6.70
5.49
6.10
6.10
8.23
6.10
Water Column In:
Sand and gravel over brown silt over gray
till
Gray till
Silt over sand and gravel over sand over
gravel over gray till
Silt over gravel over sand over sandy
gray till
Sandy gravel and silt over gray fine sand
over gray till
Sand and gravel over gray till
Dirty sand and gravel over gray till
Dirty sand over sand and gravel over brown
and gray till
Sand and gravel over clay with snail shells
Clay mixed with sand, pebbles and snail
shells
Sand and gravel over gray clay
Gravel over sand and gravel over clay and
silt over gray till
Gravel over cobble and gravel over sand
over gray till
(continued)
-------
TABLE 3. (continued)
Well
PC
31
32
33
Bottom
Elev.
41.83
34.94
6.66
Mean
Water
Level
Elev.
51.81
40.41
39.00
Mean
Water
Feet
9.98
5.47
32.34
Depth
Column
Meters
3.04
1.67
9.86
Length Screen
Above Bottom
Feet
20
15
15
Meters
6.10
4.57
4.57
Water Column In:
Brown clay over gray
Sand and gravel over
Clay and shells over
till
gray till
gravel over clay
and shells over gravel with limestone
cobbles over gravel over gray till
oo
-------
TABLE 4. TEMPERATURE AND PRECIPITATION RECORDS, DETROIT LAKES, MINNESOTA, 1973-75
CXI
Mean Air Temperatures
1973
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
Year
DN*
°C
-12.25
- 9.88
1.83
5.22
12.04
18.10
19.80
22.00
14.26
10.37
- 2.94
-11.32
5.60
+ 1.60
OF
9.9
14.2
35.3
41.4
53.7
64.6
67.7
71.7
57.7
50.7
26.7
11.6
42.1
+ 2.9
1974
°C
-16.60
-11.60
- 6.10
4.90
10.32
17.10
22.14
17.54
11.87
8.30
- 1.39
- 7.10
4.10
+ 0.10
OF
2.1
11.1
21.0
40.8
50.6
62.8
71.9
63.6
53.4
47.0
29.5
19.2
39.4
+ 0.4
1975
°C
-12.90
-12.90
- 9.16
0.72
12.65
16.76
21.36
17.76
10.71
8.44
- 1.22
-10.21
3.50
- 0.50
op
8.7
8.7
15.5
33.3
54.8
62.2
70.5
64.0
51.3
47.2
29.8
13.6
38.3
- 0.7
1973
cm
0.41
0.20
1.70
2.87
4.95
12.62
19.15
9.78
15.79
9.98
3.28
2.92
83.65
+23.79
inches
0.16
0.08
0.67
1.13
1.95
4.97
7.54
3.85
6.22
3.93
1.29
1.15
32.94
+ 9.37
Precipitation
1974
cm
1.95
1.07
3.00
3.17
11.68
4.39
13.56
9.55
1.07
5.03
3.55
1.24
59.28
- 1.52
inches
0.77
0.42
1.18
1.25
4.60
1.73
5.34
3.76
0.42
1.98
1.40
0.49
23.34
- 0.60
1975
cm
6.55
3.89
1.80
4.98
5.46
22.61
6.53
10.97
5.64
3.45
1.63
0.33
73.83
+13.03
inches
2.58
1.53
0.71
1.96
2.15
8.90
2.57
4.32
2.22
1.36
0.64
0.13
29.07
+ 5.13
"Departure from normal.
-------
TABLE 5. PELICAN RIVER DISCHARGE NEAR FERGUS FALLS, MINNESOTA,
WATER YEARS 1973-75
1973
October
November
December
January
February
March
April
May
June
July
August
September
Total
Hectare
Meters
413
359
324
348
344
826
877
664
339
200
179
388
5,261
Acre
Feet
3,350
2,910
2,630
2,820
2,790
6,700
7,110
5,380
2,750
1,620
1,450
3,150
42,730
1974
Hectare
Meters
654
741
694
705
665
730
1,220
1,880
2,051
916
652
408
11,316
Acre
Feet
5,300
6,010
5,630
5,720
5,390
5,920
9,890
15,240
16,630
7,430
5,290
3,310
91,750
1975
Hectare
Meters
329
350
232
229
286
469
1,512
2,046
1,709
1,813
1,251
1,017
11,243
Acre
Feet
2,670
2,840
1,880
1,860
2,320
3,800
12,260
16,590
13,860
14,700
10,140
8,250
91,170
83
-------
TABLE 6. MEAN ANNUAL NUTRIENT CONCENTRATIONS, mg/1, WATERSHED STATIONS
00
Aer.
Pond
Stab.
Pond
Long
Lake
Lake
St.
Clair
Sta.
G
Sta. Campbell Floyd
H Creek Lake
Little
Floyd
Lake
Sta.
L
Sta.
M
Detroit
Lake
Muskrat
Lake
Inlet
Lake
Sallie
Inlet
Lake
Sallie
Outlet
TOTAL P
1973
1974
1975
7.53
5.12
8.62
6.30
4.30
6.40
0.19
0.19
0.37
1.78
0.98
1.30
1.79
1.02
1.35
1.82
0.99
1.37
0.30
0.20
0.85
0.19
0.20
0.35
0.18
0.20
0.38
0.28
0.31
0.45
0.26
0.23
0.46
0.24
0.22
0.47
0.59
0.38
0.66
0.54
0.36
0.41
0.17
0.17
0.32
TOTAL N
1973
1974
1975
13.87
9.89
14.27
7.49
7.20
6.86
0.21
0.22
0.23
1.29
1.68
1.15
1.79
1.16
1.18
1.24
1.25
1.27
1.00
0.27
0.81
0.15
0.26
0.37
0.15
0.28
0.24
0.26
0.24
0.31
0.36
0.40
0.40
0.17
0.21
0.18
0.61
0.68
0.47
0.45
0.39
0.37
0.28
0.32
0.19
-------
TABLE 7. MEAN MONTHLY CONCENTRATIONS TOTAL P, mg/1
00
l-n
A
J 7.92
F 7.26
M 7.92
A 8.25
M 6.00
J 10.23
J -12.00
A -10.90
S *11.22
O 4.62
N * 9.57
D* 4 f\ 9
4 . OZ
T * 4 ^A
J 4 . .) O
F* A 'J '}
O . o,j
M:;; : A /i
D . 44
A* C CO
J . 5 o
M') U c:
Z . Oi)
J 2.96
J 3.43
A 2.50
N 8.78
D 9.13
B
8.58
9.24
6.27
5.00
2.31
8.25
* 5.28
* 8.58
;;; 8.58
4.29
* 5.00
* 4 9 Q
4 . Z 7
* A 9Q
4 . Z V
* A 7 «
4 . / o
-•'• ^ ^ 1
D . o i
'•'•'- '1 1 '3
O . 1 .3
1 7fl
1 . /U
2.34
1.94
1.48
7.84
10.07
E
0.10
0.07
0.10
OJ2
0.22
0.25
*0.43
-0.20
*0.28
0.16
-0.16
0.15
0.20
0. 15
0.18
0.28
F
1.94
2.48
1.98
0.94
0.53
1.71
*1.39
*2 . 94
*3.33
1.00
:;'2.38
*n 77
u . / /
#n Q i
U . 7.1
*n RA
U . 04
!'.: O A A
Z . O4
•:• i 17
1 . 1 /
0/in
. 4U
0.40
0.80
0.78
0.84
0.97
G
1.86
2.43
2.00
0.97
0.62
1.78
*1.45
*3.07
-3.07
1.14
*2.27
*n 84
U . O4
;'; 9 TO
/ . oV
* 1 1 O
J . ly
n 4n
U . 4U
0.37
0.91
0.74
0.95
.1.26
H
1.86
2.29
1.90
0.90
0.65
1.85
*1.68
*4.09
*2.54
1.02
-2.16
*n 09
u . yz.
* 9 An
Z . 4U
:S 1 99
1 . ZZ
07O
• O7
0.35
0.91
0.74
0.84
1 . 03
I
19
0.18
0.24
0.37
0.11
0.11
0.33
*0.36
*0.22
*0.33
0.26
*0.76
19
0.16
0.32
0.21
0.11
0. 18
J
•73
0.09
0.06
0.11
0.13
0. 16
0.17
*0.29
*0.18
*0.17
0.22
*0.48
'74
0.12
0.21
0. 18
0.20
0.42
K
0.06
0.11
0.08
0. 12
0.10
0.18
*0.33
*0.18
*0. 17
0.20
>::0.46
0. 13
0.22
0.16
0.22
0.28
L
0.06
0.07
0.13
0.09
0.22
0.21
*0.90
*0.37
0.20
-------
TABLE 7. (continued)
00
A
J 13.46
F 13.07
M 12.98
A 7.72
M 6.86
J 8.31
J 6.27
A 7.10
Sf> i c;
O. 10
O 6.98
N 7.25
D * 8.13
B
15.22
12.39
15.86
6.52
3.08
1.99
2.74
3.68
Q Oft
O . OU
4.04
5.19
* 7.34
E
0.52
0.19
0.32
0.44
0.56
0.22
0.33
0.45
n o i
U. Zl
0.31
0.46
*0.42
F
3.03
2.45
4.18
1.00
0.43
0.64
1.02
1.30
OCQ
. 37
0.62
0.34
*0.49
G
3.16
2.54
3.54
0.98
0.47
0.73
1.03
1.17
0.57
0.33
*0.31
H
3.18
2.67
4.65
1.61
0.49
0.68
1.15
0.87
0.52
0.30
*0.31
I
15
0.48
0.28
*3.10
3.35
0.34
0.23
0.43
0.39
0.32
0.22
*0.25
J
'75
0.64
0.17
0.75
0.38
0.53
0.21
0.19
0.23
0.31
0.24
*0.21
K
0.54
0.24
0.71
0.83
0.37
0.15
0.20
0.36
0.33
0.27
*0.19
L
0.53
0.34
0.57
1.15
0.44
0.19
0.40
0.40
0.37
0.23
*0.27
M
0.63
0.31
0.56
1.18
0.51
0.22
0.41
0.25
0] 8
. io
0.30
0.39
*0.28
N
0.75
0.22
0.61
1.33
0.43
0.14
0.31
0.41
n o/i
U. iu
0.39
0.37
*0.25
P
0.62
0.65
0.93
2.13
0.29
0.38
0.47
0.57
OQC
0.51
0.43
*0.29
1
0.58
0.63
0.86
0.43
0.29
0.28
0.45
0.34
OOO
0.29
0.26
*0.36
8
0.35
0.18
0.42
0.16
0.34
0.23
0.32
0.48
00£
. JO
0.43
0.33
*0.27
*One sample only.
-------
TABLE 8. MEAN MONTHLY CONCENTRATIONS TOTAL N, mg/1
oo
—I
I
F
M
A
M
J
J
A
S
O
N
I
I
A
N
D
A
20.16
18.34
15.39
14.28
10.94
11.20
*13.55
*13.01
*14.31
11.29
*10.22
13. 85
. u/
HO C
. ob
15. u/
. 35
. 63
3.03
7.65
10.58
8.49
9.26
B
21.64
19.28
11.18
5.81
1.96
6.04
* 1.75
* 2.40
* 5.45
3.59
* 3.00
7. 8b
. uu
i s en
lo. bU
. 5U
. 4U
. 64
1.90
1.09
1.78
5.70
7.51
E
0.28
0.27
0.34
0.22
0.14
0.10
*0.09
*0.09
*0.21
0.18
*0.45
•— _ _ —
— _ _ ~
-_ _ _ _
0.13
0.10
0.06
0.54
0.29
F
3.99
4.51
3.30
0.22
0.18
1.08
*0.07
*0.78
*0.76
0.48
*0.10
#n no
U,U^
2 "7^
. 10
5QM
. 3U
. 44
2/r -7
.O/
. 1U
0.20
0.28
0.06
0.62
0.44
G
4.30
4.75
3.45
0.22
0.09
0.70
*0.09
*0.81
*0.78
0.14
*0.11
iff\ t\\ z
u. DID
* A C '3
4 . o 6
*O ~!f.
iL . /O
01 1
. 11
0.34
0 . 36
0 . 04
0.70
0.44
H
3.44
4.20
3.54
0.26
0.15
0.84
*0.12
*1.14
*0.85
0.17
*0.16
* n n ^
U. U3
* A "71
4. / "1
* 0 Q 7
/ . O /
01 i
. 1 1
0 . 43
0.56
0.06
0.71
0.51
I
19
2.07
3.97
2.79
0.47
0.29
0.31
*0.26
*0.14
*0.31
0.24
*0.20
19
0.08
0.19
0.14
0.64
0.3J
J
73
0.26
0.30
0.28
0.12
0.07
0.06
*0.10
*0.09
*0.21
0.07
*0.12
74
0.09
0.19
0.11
0.67
0.25
K
0.22
0.27
0.28
0.13
0.10
0.09
*0. 12
*0.10
*0. 175
0.08
*0.13
0. 12
0. 18
0. 15
0.63
0.31
L
0.50
0.52
0.55
0.17
0.14
0.17
*0 . 2 1
-0.06
0.13
*0.12
0.02
0.13
o.fs
0.58
0.35
M
0.56
0.62
0.85
0.19
0. 16
0.55
-0.36
*0.14
*0.17
0.17
>;;0.22
0.04
0.17
0 . 50
0.80
0.49
N
0.30
0.35
0.35
0.08
0.12
0.11
-0.14
*0.11
^:0. 10
*0.11
*0.06
n 1 7
n ^i
n 1 1
0.10
0.13
0. 13
0.44
0.25
P
1.42
2.04
1.77
0.11
0.12
0.52
*0.14
*0 . 49
*0.38
*0.13
*0.11
*n 1 9
* Q 1 f.
*o R i
*O Q7
* 1 1 ft
n 1 1
0.12
0.28
0.07
0.24
0.21
1
1.26
1.90
1.48
0.13
0.09
0.17
0. 10
*0.01
0.10
*0.04
0.09
>;• n no
*n "M
>;;n R f
n 04
n 7«
n 1 4
0.15
0.10
0.06
0.33
0.30
8
0.65
0.30
0.30
0.14
0.12
0.09
0. 16
0.08
0.33
0.19
0.75
*0 S4
*0 51
0 47
0 37
0 1 ^
0.12
0.08
0. 13
0.57
0.29
(continued)
-------
TABLE 8. (continued)
00
oo
A
J 16.24
F 17.27
M 16.04
A 13.84
M 15.35
J 16.09
J 12.33
A 15.06
q 1 9 1 Q
O J.Z . J. "
O 11.09
N 12.17
D *13.58
B
14.06
14.95
14.96
10.85
3.28
2.43
1.91
2.35
9 07
£ • U 1
3.04
4.65
* 7.85
E
0.36
0.61
0.22
0.52
0.22
0.06
0.05
0.05
OHA
* UD
0.14
0.15
*0.13
F
2.04
3.41
3.50
1.87
0.19
0.42
0.12
0.22
007
• O /
0.63
0.37
*0.26
G
1.81
3.49
3.39
1.94
0.16
0.46
0.18
0.46
0.59
0.24
*0.27
H
2.00
3.68
3.46
2.11
0.18
0.59
0.36
0.65
0.56
0.23
*0.21
I
19
1.64
1.85
2.00
2.46
0.28
0.17
0.09
0.10
0.08
0.10
*0.21
J
'75
1.33
0.45
0.44
0.55
0.48
0.08
0.13
0.18
0.21
0.13
*0.14
K
0.43
0.35
0.34
0.50
0.24
0.09
0.06
0.07
0.25
0.15
*0.16
L
0.65
0.79
0.46
0.52
0.16
0.10
0.07
0.08
0.24
0.20
*0.19
M
0.76
0.58
1.55
0.53
0.16
0.13
0.10
0.12
Ono
. Uo
0.18
0.26
*0.33
N
0.60
0.28
0.31
0.38
0.13
0.06
0.08
0.07
Ofl4
. U1
0.10
0.07
*0.07
P
0.58
1.13
1.11
0.93
0.12
0.24
0.13
0.24
009
. OZ
0.29
0.20
*0.36
1
0.47
1.04
1.29
0.89
0.11
0.17
0.08
0.05
One
. UO
0.16
0.09
*0.06
8
0.38
0.35
0.23
0.43
0.15
0.06
0.11
0.25
Of\f\
. uo
0.07
0.12
*0.12
*One sample only.
-------
TABLE 11. MEAN NUTRIENT CONCENTRATIONS IN INDIVIDUAL WELLS
(TOP AND BOTTOM) AND IN GROUNDWATER SUB-AREAS
July, 1973-August. 19/4
Sub-area Well No.
1 2
12
13
17
18
19
20
21
22
31
SAl
2 1
9
10
11
14
23
24
SA2
3 3
4
5
6
/
8
15
32
SA3
4 16
25
26
33
SA4
5 28
29
SA5
6 27
7 30
Total P
0.70
0.91
1.25
0.71
0.68
1.17
0.78
1 . 03
0.95
1.04
0.92
0.82
0.51
0.54
0.64
0.68
0.65
0.61
0.64
0.57
0.62
0.69
0.81
0.66
0.68
0.59
0.89
0.69
1.28
0.64
0.85
1.58
1.09
0.65
0.57
0.62
1. 00
0.57
Total N
5.38
6.15
9.28
6.32
3.86
6.17
5.25
4.71
3.17
5.97
5.63
3.21
3.00
2.72
3.96
3.44
5.22
5.16
3.82
7.31
6.26
6.95
6.19
4. 10
1.34
8.87
1.61
5.33
3.3J
2.83
2.21
2.74
2.77
1.75
1.78
1.77
1.62
1.20
November. 1974-August, 1975
Total P
0.32
0.33
0.33
0.26
0.28
0.33
0.34
0.25
0.31
0.34
0.31
0.30
0.55
0.53
0.51
0.66
0.29
0.34
0.45
0.38
0.35
0.29
0 . 40
0.38
0.28
0.35
0.31
0.34
1.56
0.31
0.45
1.90
1.06
0.35
0.30
0.33
0.41
0.58
Total N
2.87
10.27
9.72
8.83
1.71
6.29
2.10
1.15
0.21
8.98
5.21
1.37
0.62
3 . 48
3 . 55
1 .89
6.10
2.98
2.86
4.04
3.47
9.38
4.63
3.44
0.95
9.71
1.64
4.66
3 . 04
0.81
0.80
3.19
1.96
0.76
2.64
1.70
0.55
0.69
89
-------
TABLE 12. MEAN NUTRIENT CONCENTRATIONS AT TOP AND BOTTOM
OF GROUNDWATER IN INDIVIDUAL WELLS
1973-74
Well
IT
2T
2B
3T
3B
4T
5T
5B
6T
6B
7T
7B
8T
9T
9B*
10T
11T
11B
12T
13T
14T
1ST
15B
16T
16B
17T
17B
1ST
Total P
0.82
0.68
0.71
0.53
0.80
0.62
0.67
0.70
0.84
0.77
0.68
0.64
0.68
0.73
0.39
0.54
0.76
0.51
0.91
1.25
0.68
0.55
0.63
1.14
1.41
0.66
0.76
0,58
Total N
3.21
5.37
5.88
7.25
7.37
6.26
6.03
7.87
6.29
6.09
2.96
5.23
1.34
2.19
3.81
2.72
5.02
2.90
6.15
9.28
3.44
9.49
8.25
3.19
3.42
6.94
5.70
5.19
1974-75
Total P
0.30
0.33
0.30
0.40
0.36
0.35
0.26
0.32
0.39
0.40
0.36
0.39
0.28
0.55
0.53
0.56
0.46
0.33
0.33
0.66
0.35
0.35
0.99
2.13
0.25
0.27
0.24
Total N
1.37
0.37
5.37
3.10
4.98
3.47
4.17
5.21
4.61
4.65
3.52
3.36
0.95
0.62
3.48
3.10
3.99
10.27
9.72
1.89
9.41
10.00
2.67
3.40
8.57
9.08
0.81
* 3 records only
(continued)
90
-------
TABLE 12. (continued)
1973-74
Well
18B
19T
20T
20B
21T
21B
22T
22B
23T
23B
24T
24B
25T
25B
26T
26B
27T
27B
28T
28B
29T
29B
30T
30B
31T
31B
32T
32B
Total P
0.77
1.17
0.61
0.95
0.89
1.24
0.97
0.92
0.65
0.64
0.64
0.57
0.49
0.79
0.90
0.84
0.96
1.05
0.69
0.60
0.63
0.50
0.62
0.52
1.19
0.88
0.72
1.05
Total N
2.53
6.17
7.34
3.16
4.65
4.76
2.22
4.11
5.66
4.77
5.32
5.00
2.52
3.14
1.27
5.36
1.54
1.70
1.51
1.99
1.87
1.69
0.99
1.41
7,08
4.85
1.68
1.53
1974-75
Total P
0.31
0.33
0.33
0.34
0.22
0.27
0.29
0.32
0.29
0.28
0.34
0.34
0.33
0.29
0.48
0.42
0.37
0.44
0.30
0.39
0.31
0.29
0.45
0.70
0.35
0.33
0.32
0.30
Total N
2.60
6.29
3.30
0.89
1.14
1.16
0.25
0.16
6.52
5.65
1.69
4.26
0.78
0.84
0.59
1.00
0.49
0.60
0.59
0.88
2.50
2.77
0.51
0.86
9.43
8.52
1.35
1.92
(continued)
91
-------
TABLE 12. (continued)
1973-74 1974-75
Well Total P Total N Total P Total N
33T
33B
Mean
1.62
1.53
0.80
2.79
2.69
4.31
1.82
1.97
0.46
3.07
3.32
3.44
92
-------
TABLE 13. MEAN CALCIUM AND MAGNESIUM CONCENTRATIONS,
GROUNDWATER, mg/1 AS CaCO3
July, 1973 -August, 1974
PC Well
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
M
Top
Ca
158
225
174
217
162
170
146
193
259
164
175
238
223
138
220
214
236
242
269
168
103
250
228
158
187
214
688
224
166
183
213
238
223
214
Mg
89
77
98
84
94
90
78
106
101
88
106
119
135
106
121
119
113
112
135
97
79
120
106
94
77
104
566
107
116
134
100
87
126
118
Bottom
Ca
...
227
184
177
168
151
—
—
307
226
237
242
355
—
257
166
254
235
164
218
382
716
362
160
190
449
249
228
263
Mg
83
100
105
96
81
—
—
—
168
—
—
—
118
114
122
157
117
120
159
121
95
101
159
632
201
150
197
193
99
118
150
November, 1974- August.
Top
Ca
167
176
147
201
162
168
156
203
175
169
178
179
181
126
218
215
221
166
262
201
89
243
244
166
199
245
773
205
171
171
164
200
237
205
Mg
70
66
75
73
81
86
74
108
67
84
93
89
94
64
85
102
103
79
113
95
67
112
97
67
68
111
743
107
114
163
72
75
106
109
, 1975
Bottom
Ca
202
181
176
167
156
—
—
—
236
216
221
226
295
207
116
245
253
205.
203
278
814
387
188
174
189
197
235
240
Mg
82
79
86
84
83
—
—
—
109
—
—
91
105
109
105
106
72
114
109
89
67
117
740
225
110
178
78
82
1 19
131
93
-------
TABLE 14. MEAN ALKALINITIES, GROUNDWATER, mg/1 AS CaCO3
PC Well
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
M
Top
213
240
230
254
199
218
194
282
Til
227
237
321
262
188
275
414
286
293
358
224
139
297
278
225
261
306
819
235
263
321
254
317
412
282
1973-74
Bottom
262
230
—
236
221
206
—
—
—
426
—
—
—
275
447
315
440
—
305
235
331
311
226
292
523
848
285
274
372
566
338
434
350
Top
208
207
185
224
195
212
202
281
214
224
212
194
208
160
231
350
270
210
309
241
124
293
284
201
246
305
653
161
229
327
169
238
413
248
1974-75
Bottom
237
221
222
213
205
—
—
—
294
—
—
—
236
381
268
303
—
248
171
299
315
262
256
361
669
266
248
342
218
255
416
274
94
-------
TABLE 15. OXYGEN RANGES AT GROUNDWATER SAMPLING SITES,
APRIL, 1974 - AUGUST, 1975 (mg/1)
Site
IT
2T
2B
3T
3B
4T
5T
5B
6T
6B
7T
7B
8T
9T
10T
11T
11B
12T
13T
14T
15T
15B
16T
16B
17T
17B
1ST
18B
19T
Q£ Range
2.6 - 9.3
5.7 -11.8
4.7 - 9.5
2.8 -12.1
5.84-11.3
5.0-10.4
6.25-10.4
6.1 - 9.3
5.1 - 8.6
5.2 - 8.7
7.7 - 9.2
6.4 - 8.5
0.6 - 9.8
0.0 - 7.2
5.8 -10.3
1.0 -11.8
0.0 - 6.7
2.5 -10.1
8.5-11.8
4.9 -10.1
2.9 -10.2
7.2 -10.2
0.1 - 4.2
0.0 - 0.8
6.0 - 9.7
1.3 - 9.0
0.96-12.6
0.25-9.7
7.2 - 9.0
Site
20T
20B
21T
21B
22T
22B
23T
23B
24T
24B
25T
25B
26T
26B
27T
27B
28T
28B
29T
29B
30T
30B
31T
31B
32T
32B
33T
33B
02 Range
2.6 -
0.0 -
0.7 -
0.0 -
0.2 -
0.0 -
1.4-
0.81 -
0.99 -
1.2 -
4.6 -
3.8 -
0.3 -
0.1 -
0.0 -
0.0 -
0.1 -
0.0 -
0.3-
0.2 -
0.1 -
0.0 -
4.0-
0.0 -
0.6-
0.3 -
0.0 -
0.0 -
9.8
5.45
7.57
1.5
1.4
1.36
10.2
-9.5
-8.8
7.6
8.2
7.82
6.96
6.86
1.0
1.0
3.27
1.0
10.6
8.0
4.2
4.1
10.1
8.5
10.78
7.45
6.8
0.78
95
-------
TABLE 16. VARIATION IN SEEPAGE VOLUME AND P AND N LOADS
(Quantities/Hectare/Day)
1975
m3
H20
Grams
P
Grams
N
Lake St. Glair
6/11
6/18
7/16
7/24
8/5
8/19
162
11
24
11
104
19
54
36
160
40
90
60
41
—
—
—
94
—
Lake Sallie
6/9
6/17
6/27
7/1
7/11
7/15
7/29
8/6
8/15
8/26
32
31
20
37
27
35
65
128
102
252
110
27
100
200
103
220
230
290
450
500
3
—
0.4
570
590
520
385
730
1,030
4,140
96
-------
TABLE 17. NUTRIENT CONCENTRATION IN RAIN, DAILY MEANS, mg/1
Date
Total
P
Available
P
NH3-N
NO2-N
NO3-N
Total
N
1973
5/24
6/16
6/17
6/25
7/1
7/9
7/22
7/23
7/24
7/29
7/30
8/5
8/7
8/31
9/1
Mean
0.08
0.15
0.25
0.14
0.05
0.03
0.10
0.04
0.03
0.06
0.04
0.05
0.07
0.07
0.05
0.07
0.08
0.09
0.20
0.08
0.04
0.03
0.06
0.03
0.03
0.04
0.04
0.03
0.06
0.06
0.04
0.06
0.20
0.40
1.60
1.00
2.60
1.50
0.53
0.53
0.51
0.90
0.92
1.02
2.05
0.59
1.19
1.04
0.006
0.004
0.010
0.006
0.010
0.004
0.005
0.003
0.003
0.006
0.005
0.004
0.004
0.004
0.006
0.005
0.15
0.28
0.59
0.75
2.05
0.37
0.19
0.18
0.26
0.23
0.17
0.32
0.41
0.17
0.53
0.44
0.36
0.68
2.20
1.75
4.66
1.87
0.73
0.71
0.77
1.14
1.10
1.34
2.46
0.76
1.73
1.48
1974
5/10
7/16
7/21
8/2
8/12
8/15
Mean
0.03
0.22
0.06
0.08
0.02
0.06
0.08
0.02
0.06
0.03
0.01
0.00
0.00
0.02
0.69
1.23
0.65
0.41
0.57
1.04
0.77
0.002
0.004
0.002
0.006
0.003
0.005
0.004
1.43
1.004
0.40
0.30
0.26
1.22
0.77
2.12
2.24
1.05
0.72
0.83
2.26
1.54
1975
6/4
6/11
6/17
6/19
6/30
7/9
8/1
Mean
0.08
0.05
0.11
0.14
0.27
0.14
0.11
0.13
0.03
0.007
0.01
0.02
0.04
0.03
0.02
0.02
0.83
0.46
0.43
0.28
0.43
--
0.34
0.46
0.00
0.002
0.003
0.002
0.003
0.001
0.002
0.75
0.15
0.11
0.11
0.18
—
0.09
0.23
1.58
0.61
0.54
0.38
0.61
—
0.43
0.69
97
-------
TABLE 18. PRECIPITATION AND NUTRIENTS FALLING ON LAKE SALLIE
Date
Total P
*mg/l
Total N
*mg/l
M3 Acre Feet
Rain
Rain
KgP
KgN
Lbs.
P
Lbs.
N
1973
5/24
6/16
6/17
6/25
7/1
7/9
7/22
7/23
7/24
7/29
7/30
8/5
8/7
8/31
9/1
Totals
0.03
0.15
0.25
0.14
0.05
0.03
0.04
0.04
0.03
0.06
0.04
0.05
0.07
0.07
0.05
0.36
0.68
2.20
1.75
4.66
1.87
0.725
0.71
0.77
1.14
1.10
1.34
2.46
0.76
1.73
1,233
93,708
70,281
60,417
44,388
165,222
85,077
59,184
390,861
108,504
14,796
133,164
59,184
170,154
104,805
1,560,978
1
76
57
49
36
134
69
48
317
88
12
108
48
138
85
1,266
0.036
14
18
9
2
5
4
2
12
6
0.45
7
4
12
5
100
0.45
64
155
106
207
309
62
42
301
124
16
179
146
129
181
2,021
0.08
31
39
19
5
11
8
5
26
14
1
15
9
26
12
221
1
141
341
233
456
682
136
93
664
273
36
394
321
285
400
4,456
1974
5/10
7/16
7/21
8/2
8/12
8/15
Totals
0.03
0.22
0.06
0.08
0.02
0.06
1.43
2.24
1.05
0.72
0.83
2.26
157,824
146,727
260,163
24,660
83,844
7,398
680,616
128
119
211
20
68
6
552
5
32
15
2
2
0.45
56
335
329
274
18
70
17
1,043
10
71
34
4
4
1
124
738
725
603
39
154
37
2,296
1975
6/4
6/11
6/17
6/19
6/30
7/9
8/1
Totals
0.08
0.05
0.11
0.14
0.27
0.14
0.11
1.58
0.61
0.54
0.38
0.61
—
0.43
46,854
23,427
44,388
295,920
351,405
30,825
76,446
869,265
38
19
36
240
285
25
62
705
4
1
5
41
95
5
9
160
74
15
24
112
215
—
33
473
8
3
11
91
209
10
19
351
163
32
53
248
473
73
1,042
*Daily means.
98
-------
TABLE 19. NUTRIENTS CONTRIBUTED BY RAIN TO LAKE SURFACES (KILOGRAMS)
St.
Glair Long
Big
Floyd
Little
Floyd Detroit Muskrat
Total
Sallie All Lakes
1973
P 11 34
N 228 687
79
1,597
17 236 5
335 4,770 101
100 482
2,021 9,739
1974
P 6 19
N 118 355
1
P 18 54
N 53 161
44
824
126
374
9 132 3
173 2,461 52
1975
27 378 8
79 1,116 24
56 269
1,043 5,026
160 771
473 2,280
99
-------
TABLE 20. DATES AND VOLUMES OF HYPOLIMNIA APPEARING IN LAKE SALLIE
Date
June 6, 1973
11
13*
27
July 3
10
14*
August 7*
September 26*
July 10, 1974
19
24*
July 3, 1975
11*
Hypolimnion Volume
418 hm
276 hm
47 hm
461 hm
409 hm
360 hm
276 hm
169 hm
26 hm
418 hm
233 hm
47 hm
47 hm
45 hm
Per Cent of Total Volume
16.37
10.80
1.84
18.06
16.02
14.10
10.80
6.60
1.01
16.37
9.13
1.84
1.84
1.76
*Last date thermocline observed
100
-------
TABLE 21. PHYTOPLANKTON CONCENTRATION AT WATERSHED STATIONS,
MAY - NOVEMBER, 1975 (NOS. PER ML)
A
5/30
6/6
6/11
6/17
6/24
7/1
7/8
7/15
7/23
7/27
8/5
8/14
8/19
8/29
9/5
9/12
10/3
10/10
10/17
10/24
10/31
11/7
11/14
11/21
318
186
1
14
49
58
30
23
1
3
5
6
6
31
203
48
164
129
143
43
,336
,558
332
120
,355
,699
,332
,424
,098
,330
124
309
,891
,139
,399
,500
,556
,798
,677
,760
,161
,767
,625
,445
B
450
109
62
27
130
113
243
298
371
589
424
529
755
194
631
370
205
134
157
254
322
17,976
14,567
46,517
13
12
18
17
8
11
19
12
34
37
27
10
1
1
F
,961
,928
,533
,848
,639
,580
,868
,441
,470
,606
,171
,519
720
,935
,461
359
221
101
237
184
254
12
105
170
M
142
39
40
62
76
58
45
105
116
88
67
163
108
72
141
74
86
96
108
328
209
227
194
258
N
189
75
124
189
317
454
429
392
652
648
599
313
306
363
749
642
227
435
500
403
301
259
416
501
P
907
1,573
3,393
2,181
1,232
2,277
2,065
2,789
1,915
2,532
3,907
1,640
800
485
827
328
262
334
172
334
185
320
260
275
1
1,357
14,694
2,664
2,592
1,257
1,506
1,792
1,399
3,645
4,135
49
4,556
3,844
3,560
4,066
3,550
624
359
336
613
1,026
1,034
529
245
4-1
486
165
64
163
178
189
1,830
12,220
8,079
8,612
1,260
6,657
3,618
9,535
11,126
4,295
9,443
11,338
10,962
14,864
9,755
7,721
33,671
1,524
8
869
318
178
247
167
756
5,868
1,728
8,346
4,628
1,071
4,769
8,975
4,889
18,098
9,739
11,098
9,658
8,900
14,256
10,369
6,063
3,735
1,372
101
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-79-046
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
WATERSHED AND POINT SOURCE ENRICHMENT AND LAKE TROPHIC
STATE INDEX
5. REPORT DATE
April 1979 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Joe K. Neel
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Department of Biology
The University of North Dakota
Grand Forks, North Dakota 58202
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
R800490
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research Laboratory—Corvallis
Office of Research and Development
Environmental Protection Agency
Corvallis. Oregon 97330
13. TYPE OF REPORT AND PERIOD COVERED
final 1/1Q7"*—17/1Q7S
14. SPONSORING AGENCY CODE
EPA/600/02
15. SUPPLEMENTARY NOTES
Project Officer: Robert M. Brice, 503-757-4709 (FTS 4204709)
Corvallis, Oregon 97330
16. ABSTRACT
Water in the permeable soils of the upper Pelican River watershed, Minnesota, requires
slightly more than a year to move generally out of the phreatic zone into surface
channels and basins. Its nutrient content seems mainly responsible for the load borne
in surface waters above entrance of a wastewater effluent, and groundwater changes hav ;
been followed a year later by similar ones in surface water. In 1975 P load from nonp
point sources markedly exceeded that from the wastewater effluent. Nutrients in
groundwater are assumed to result from soil surface application, but only quantities
supplied by precipitation have been measured. The most noxious conditions in surface
waters have been occasioned by heterocystous blue-green phytoplankters, but the great-
est plant mass has been produced by rooted and attached vegetation. Blue-green algae
have not been predominant in some water bodies and only intermittently in most others.
Their occurrence appeared controlled by environmental conditions other than nutrient
loading in the ranges encountered here. Groundwater seepage into these lakes contri-
buted more nutrients than precipitation, but the latter supplied what may be signifi-
cant amounts to watershed soils. A trophic state index based on change in Mg/Ca quo-
tient relative to water residence time has reliably depicted relative total producti-
vity levels in 6 lakes or ponds, and its general applicability, at least to natural
lakes, now appears likely.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (Rev. 4-77)
102
•ft U.S. Government Printing Office: 1979—698-322/141
------- |