United States ,
Environmental Protection
Agency
Great Lakes National EPA-905/6/89-001 (^
Program Office GLNPO Report No. 4
230 South Dearborn Street April 1989
Chicago, Illinois 60604
Water Quality in the
Middle Great Lakes:
Results of the 1985 U.S. EPA
Survey of Lakes Erie,
Huron and Michigan
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WATER QUALITY IN THE MIDDLE GREAT LAKES:
RESULTS OF THE 1985 USEPA SURVEY
OF LAKES ERIE, HURON AND MICHIGAN1
David C. Rockwell
U.S. Environmental Protection Agency
Douglas K. Salisbury
Applied Technology Division
Computer Sciences Corporation
and
Barry M. Lesht
Center for Environmental Research
Argonne National Laboratory
lrEhis work was sponsored by the U.S. Environmental Protection Agency,
Great Lakes National Program Office under LAG DW89931897-01-0.
The submitted manuscript has been authorized
by a contractor of the U.S Government under
contract No. W-31-109-ENG-38. Accordingly, the
U.S. Government retains a nonexclusive,
royalty-free license to publish or reproduce
the published form of this contribution, or
allow others to do so, for U.S. Government
purposes.
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DISCLAIMER
The information in this document has been funded wholly by the United
States Environmental Protection Agency (USEEA). It has been subject to
peer review by the USEPA and has been approved for publication. Any
mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
11
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TABLE OF CONTENTS
Page
FIGURES v
TABLES " xiii
AOOXICWLEDGMENrS xvii
FOREWORD xix
ABSTRACT 1
TECHNICAL SUMMARY 3
General Findings 3
Nutrient Concentrations 5
Major Ion Concentrations 9
Other Parameters 13
Trophic Status 14
Response to Loads - Model Comparisons 14
INTRODUCTION 17
Scope 17
General Plan and Rationale 17
METHODS 33
Ship and Sampling Equipment 33
Sampling Procedures 34
Analytical Methods 34
1985 Helicopter Surveys 40
Quality Assurance 40
RESULTS 47
Scope 47
Temporal Variation Within Surveys 48
Spatial Segmentation 49
Water Column Structure 58
Parameter Mean Values by Basin, Survey, and Layer 78
Composited Upper 20-Meter Samples 85
Concentration of Major Ions - Ion Balances 95
Secchi Depth by Basin and Survey 102
DISCUSSION 105
Trophic Status 105
Comparison with 1983 and 1984 Survey Results 111
Detection of Significant Changes 131
Comparison with Recent Historical Data 139
Comparison with Eutrophication Models 165
CONCLUSIONS AND RECXliyENDATIONS 197
LITERATURE CITED 201
ill
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TABLE OF CONTENTS (continued)
Page
Appendix A - Statistical Summary of Survey Data A-l
Appendix B - Raw Data —1985 Great Lakes Surveillance (Microfiche) ... B-l
IV
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FIGURES
Number Page
1. Location of 1985 surveillance stations in Lake Michigan 23
2. Location of 1985 surveillance stations in Lake Huron 24
3. Location of 1985 surveillance stations in Lake Erie 25
4. Surface water temperature in southern Lake Michigan - 1985 59
5. Surface water temperature in northern Lake Michigan - 1985 59
6. Surface water temperature in northern Lake Huron - 1985 60
7. Surface water temperature in southern Lake Huron - 1985 60
8. Surface water temperature in western Lake Erie - 1985 61
9. Vertical profiles of water temperature in southern Lake
Michigan, station 18, during the spring, summer and fall
surveys 62
10. Vertical profiles of water temperature in northern Lake
Michigan, station 41, during the spring, summer and fall
surveys 63
11. Vertical profiles of water temperature in northern Lake Huron,
stations 45 and 43, during the spring, summer and fall surveys. 64
12. Vertical profiles of water temperature in southern Lake Huron,
stations 93 and 15, during the spring, summer and fall surveys. 65
13. Vertical profiles of water temperature in western, station 57;
central, station 78; and eastern, station 15, Lake Erie, during
the spring, summer and fall surveys 66
14. Vertical profiles of turbidity in southern Lake Michigan,
station 18, during the spring, summer and fall surveys 69
15. Vertical profiles of turbidity in northern Lake Michigan,
station 41, during the spring, summer and fall surveys 70
16. Vertical profiles of turbidity in northern Lake Huron, stations
45 and 43, during the spring, summer and fall surveys 71
17. Vertical profiles of turbidity in southern Lake Huron, stations
93 and 15, during the spring, summer and fall surveys 72
18. Vertical profiles of turbidity in western, station 57; central,
station 78; and eastern, station 15, Lake Erie, during the
spring, summer and fall surveys 73
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FIGURES (continued)
19. Vertical profiles of dissolved silicon in southern Lake
Michigan, station 18, during the spring, sunnier and fall
surveys 75
20. Vertical profiles of dissolved silicon in northern Lake
Michigan, station 41, during the spring, summer and fall
surveys 76
21. Vertical profiles of dissolved silicon in northern Lake Huron,
stations 45 and 43, during the spring, summer and fall surveys. 77
22. Vertical profiles of dissolved silicon in southern Lake Huron,
stations 93 and 15, during the spring, summer and fall surveys. 78
23. Vertical profiles of dissolved silicon in western, station 57;
central, station 78; and eastern, station 15, Lake Erie, during
the spring, summer and fall surveys 79
24. Vertical profiles of dissolved nitrate + nitrite nitrogen in
southern Lake Michigan, station 18, during the spring, summer
and fall surveys 80
25. Vertical profiles of dissolved nitrate + nitrite nitrogen in
northern Lake Michigan, station 41, during the spring, summer
and fall surveys 81
26. Vertical profiles of dissolved nitrate + nitrite nitrogen in
northern Lake Huron, stations 45 and 43, during the spring,
summer and fall surveys 82
27. Vertical profiles of dissolved nitrate + nitrite nitrogen in
southern Lake Huron, stations 93 and 15, during the spring,
summer and fall surveys 83
28. Vertical profiles of dissolved nitrate + nitrite nitrogen in
western, station 57; central, station 78; and eastern, station
15, Lake Erie, during the spring, summer and fall surveys 84
29. Vertical profiles of dissolved ammonia nitrogen, total
phosphorus and total dissolved phosphorus in southern Lake
Michigan, station 18, during the spring, summer and fall
surveys 85
30. Vertical profiles of dissolved aimionia nitrogen, total
phosphorus and total dissolved phosphorus in northern Lake
Michigan, station 41, during the spring, summer and fall
surveys 86
VI
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FIGURES (continued)
31. Vertical profiles of dissolved ammonia nitrogen, total
phosphorus and total dissolved phosphorus in northern, station
45; and southern, station 15, Lake Huron, during the spring,
sunmer and fall surveys 87
32. Vertical profiles of dissolved airmania nitrogen, total
phosphorus and total dissolved phosphorus in western, station
57; central, station 78; and eastern, station 15, Lake Erie,
during the spring, sunnier and fall surveys 88
33. Comparison of average chlorophyll-a concentrations determined
from discrete epilimnion samples with those determined from the
composite 20-meter sample - all lakes, all surveys, 1985 97
34. Comparison of average total phosphorus concentrations
determined from discrete epilimnion samples with those
determined from the composite 20-meter sample - all lakes, all
surveys, 1985 97
35. Comparison of average total dissolved phosphorus concentrations
determined from discrete epilimnion samples with those
determined from the composite 20-meter sample - all lakes, all
surveys, 1985 98
36. Comparison of average dissolved ortho phosphorus concentrations
determined from discrete epilimnion samples with those
determined from the composite 20-meter sample - all lakes, all
surveys, 1985 98
37. Comparison of average dissolved nitrate + nitrite nitrogen
concentrations determined from discrete epilimnion samples with
those determined from the composite 20-meter sample - all lakes,
all surveys, 1985 99
38. Comparison of average total Kjeldahl nitrogen concentrations
determined from discrete epilimnion samples with those
determined from the composite 20-meter sample - all lakes, all
surveys, 1985 99
39. Comparison of average total amtonia nitrogen concentrations
determined from discrete epilimnion samples with those
determined from the composite 20-meter sample - all lakes, all
surveys, 1985 100
40. Comparison of average dissolved reactive silica concentrations
determined from discrete epilimnion samples with those
determined from the composite 20-meter sample - all lakes, all
surveys, 1985 100
VI1
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FIGURES (continued)
Page
41. Comparison of average chloride concentrations determined from
discrete epilimnion samples with those determined from the
composite 20-meter sample - all lakes, all surveys, 1985 101
42. Comparison of average sulfate concentrations determined from
discrete epilimnion samples with those determined from the
composite 20-meter sample - all lakes, all surveys, 1985 101
43. Basin average 1985 values of cholorophyll-a in the surface
waters compared with Dobson's (1974) water quality index 109
44. Basin average 1985 values of particulate phosphorus in the
surface waters compared with Dobson's (1974) water quality
index 109
45. Basin average 1985 values of total phosphorus in the surface
waters compared with the International Joint Commission's
(1976a) water quality index 110
46. Basin average 1985 values of 30/Secchi depth compared with
Dobson's (1974) water quality index 110
47. Basin geometrical mean 1985 values of aerobic heterotrophs in
the surface waters compared with Rockwell's (1980) water quality
index Ill
48. Comparison of surface water temperatures 1983, 1984 and 1985 in
the southern basin of Lake Michigan 119
49. Comparison of surface water temperatures 1983, 1984 and 1985 in
the northern basin of Lake Michigan 119
50. Comparison of surface water temperatures 1983, 1984 and 1985 in
the northern basin of Lake Huron 120
51. Comparison of surface water temperatures 1983, 1984 and 1985 in
the southern basin of Lake Huron 120
52. Comparison of surface water temperatures 1983, 1984 and 1985 in
the western basin of Lake Erie 121
53. The change required for the detection of significant
(alpha=0.05) differences using the two-tailed t-test as a
function of the parameter coefficient of variation and the
sample size 133
54. Key to variable width, notched box plots 142
Vlll
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FIGURES (continued)
55. Box plot comparison of spring total phosphorus concentrations
in the southern basin of Lake Michigan, 1976-1985 143
56. Box plot comparison of spring dissolved reactive silica
concentrations in the southern basin of Lake Michigan, 1976-
1985 143
57. Box plot comparison of spring dissolved nitrate + nitrite
nitrogen concentrations in the southern basin of Lake Michigan,
1976-1985 145
58. Box plot comparison of epilimnion depletion of dissolved
reactive silica in the southern basin of Lake Michigan, 1976-
1985 145
59. Box plot comparison of epilimnion depletion of dissolved
nitrate + nitrite nitrogen in the southern basin of Lake
Michigan, 1976-1985 147
60. Box plot comparison of summer Secchi depth in the southern
basin of Lake Michigan, 1976-1985 147
61. Total phosphorus in the surface waters of Lake Huron, spring
1971 to 1985 149
62. Dissolved nitrite + nitrate nitrogen in the surface waters of
Lake Huron, spring 1971 to 1985 149
63. Dissolved reactive silica in the surface waters of Lake Huron,
spring, 1971 to 1985 150
64. Seasonal dissolved reactive silica in the surface waters of
Lake Huron - 1971, 1980, 1983, and 1985 151
65. Total phosphorus in the western basin of Lake Erie - 1970 to
1985 156
66. Total phosphorus in the central basin of Lake Erie - 1970 to
1985 156
67. Total phosphorus in the eastern basin of Lake Erie - 1970 to
1985 157
68. Nitrate + nitrite nitrogen in the western basin of Lake Erie -
1970 to 1985 158
69. Nitrate + nitrite nitrogen in the central basin of Lake Erie -
1970 to 1985 158
IX
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FIGURES (continued)
Number Page
70. Nitrate + nitrite nitrogen in the eastern basin of Lake Erie -
1970 to 1985 159
71. Chlorophyll-a in the western basin of Lake Erie - 1970 to 1985. 160
72. Chlorophyll-a in the central basin of Lake Erie - 1970 to 1985. 160
73. Chlorophyll-a in the eastern basin of Lake Erie - 1970 to 1985. 161
74. Chloride in the central basin of Lake Erie - 1966 to 1985 164
75. Specific conductance in the central basin of Lake Erie-1966 to
1985 164
76. GLMB model simulation of total phosphorus in Lake Michigan 173
77. GLMB model simulation of total phosphorus in Lake Huron 173
78. GLMB model simulation of total phosphorus in the western basin
of Lake Erie 174
79. GLMB model simulation of total phosphorus in the central basin
of Lake Erie 174
80. GLMB model simulation of total phosphorus in the eastern basin
of Lake Erie 175
81. WASP model simulation of chlorophyll-a in the epilimnion of
southern Lake Michigan 181
82. WASP model simulation of chlorophyll-a in the epilimnion of
northern Lake Michigan 181
83. WASP model simulation of total phosphorus in the epilimnion of
southern Lake Michigan 182
84. WASP model simulation of total phosphorus in the epilimnion of
northern Lake Michigan 182
85. WASP model simulation of ortho phosphorus in the epilimnion of
southern Lake Michigan 184
86. WASP model simulation of ortho phosphorus in the epilimnion of
northern Lake Michigan 184
87. WASP model simulation of chlorophyll-a in the epilimnion of
northern Lake Huron 185
x
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FIGURES (continued)
Number
88. WASP model simulation of chlorophyll-a in the epilimnion of
southern Lake Huron 185
89. WASP model simulation of total phosphorus in the epilimnion of
northern Lake Huron 187
90. WASP model simulation of total phosphorus in the epilimnion of
southern Lake Huron 187
91. WASP model simulation of ortho phosphorus in the epilimnion of
northern Lake Huron 188
92. WASP model simulation of ortho phosphorus in the epilimnion of
southern Lake Huron 188
93. WASP model simulation of chlorophyll-a in western Lake Erie 190
94. WASP model simulation of chlorophyll-a in the epilimnion of
central Lake Erie 190
95. WASP model simulation of chlorophyll-a in the epilimnion of
eastern Lake Erie 191
96. WASP model simulation of total phosphorus in western Lake Erie. 192
97. WASP model simulation of total phosphorus in the epilimnion of
central Lake Erie 192
98. WASP model simulation of total phosphorus in the epilimnion of
eastern Lake Erie 193
99. WASP model simulation of ortho phosphorus in western Lake Erie. 194
100. WASP model simulation of ortho phosphorus in the epilimnion of
central Lake Erie 194
101. WASP model simulation of ortho phosphorus in the epilimnion of
eastern Lake Erie 195
102. WASP model simulation of dissolved oxygen in the upper
hypolimnion (17-22 meters) of central Lake Erie 196
XI
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XI1
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TABLES
Page
1. Parameters measured during the 1985 surveillance program 21
2. Station locations and depths — 1985 surveillance program 26
3. Julian day and Greenwich time of sampling in Lakes Erie, Huron,
and Michigan as part of the 1985 helicopter survey related to
the 1985 surveillance program 28
4. Julian day and Greenwich time of sampling in Lake Michigan
during the 1985 surveillance program 29
5. Julian day and Greenwich time of sampling in Lake Huron during
the 1985 surveillance program 30
6. Julian day and Greenwich time of sampling in Lake Erie during
the 1985 surveillance program 31
7. Summary of quality control analyses, winter helicopter surveys,
1985 surveillance program 42
8. Summary of quality control analyses, spring surveys, 1985
surveillance program 43
9. Summary of quality control analyses, summer surveys, 1985
surveillance program 44
10. Summary of quality control analyses, fall surveys, 1985
surveillance program 45
11. Criteria of detection established by analysis of reagent blanks
- 1985 surveillance program 46
12. Comparison of survey legs - Lake Michigan southern basin
epilimnion 50
13. Comparison of survey legs - Lake Huron northern basin
epilimnion 51
14. Comparison of survey legs - Lake Erie central basin epilimnion. 52
15. Comparison of Lake Michigan northern and southern basin
epilimnia 53
16. Comparison of Lake Huron northern and southern basin epilimnia. 54
17. Comparison of Lake Erie western and central basin epilimnia 55
18. Comparison of Lake Erie central and eastern basin epilimnia.... 56
Xlll
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TABLES (continued)
Page
19. Average epilimnion temperature and thermocline depth by survey
and basin, 1985 67
20. Suntner survey estimated layer thickness and the percentage of
total average basin depth in the central and eastern basins of
Lake Erie, 1983, 1984 and 1985 68
21. Comparison of summer survey basin mean values of turbidity,
nutrients, conductivity, and temperature in the hypolimnia and
nepheloid layers of Lakes Michigan, Huron and Erie, 1985 74
22. Parameter means by basin, survey, and layer - Lake Michigan,
1985 89
23. Parameter means by basin, survey, and layer - Lake Huron, 1985. 91
24. Parameter means by basin, survey, and layer - Lake Erie, 1985.. 93
25. Parameter means determined from composited upper 20-meter
samples, averaged by survey and basin - Lakes Michigan, Huron
and Erie, 1985 95
26. Absolute concentrations of major ions in the epilimnion -
summer survey, 1985 102
27. Stoichiometric concentrations of major ions in the epilimnion -
summer survey, 1985 103
28. Secchi depths averaged by basin and survey, 1985 104
29. Classification limits for trophic status 105
30. Survey and basin mean values - water quality index
classification parameters, 1985 107
31. Aerobic heterotrophs in surface samples collected during the
1985 surveillance program 112
32. Comparison of Lake Michigan spring water quality statistics
calculated from subsets of stations similar to those sampled in
1983 with all open-lake stations using 1976 and 1977 intensive
survey data 115
33. Comparison of Lake Erie water quality statistics calculated
from subsets of stations similar to those sampled during 1983
and 1984 with all open-lake stations using 1985 spring survey
data 116
xiv
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TABLES (continued)
Page
34. Monthly mean air temperature at Great Lakes Winter Severity
Index stations in Centigrade - Winter 1984 - 1985 117
35. Observed nutrient depletion in Lakes Michigan and Huron
comparing spring survey (maximum) concentrations with summer
survey (minimum) concentrations 122
36. Inter-year basin comparisons - Lake Michigan spring surface
samples from open-lake stations 123
37. Inter-year comparisons - Lake Huron, both basins, spring
surface samples from open-lake stations 126
38. Inter-year basin comparisons - Lake Erie spring surface samples
from open-lake stations 127
39. Comparison of epilimnion mean values of selected parameters,
spring surveys, 1983-1985 128
40. Summary of statistically significant differences between
epilimnion data collected in 1985 with 1983 and 1984 for
selected parameters 130
41. Minimum difference of means for rejection of null hypothesis,
HO : x1=x2 for all spring samples 134
42. Comparison of standard deviations of selected parameters,
spring survey, all samples, 1983-1985 136
43. Comparison of standard deviations of selected parameters, spring
survey, surface samples, 1983-1985 137
44. Comparison of standard deviations of selected parameters, spring
survey, station averages, 1983-1985 138
45. Lake Erie total phosphorus concentrations, 1970-1985 153
46. Lake Erie nitrate + nitrite nitrogen concentrations, 1965-1985. 154
47. Lake Erie chlorophyll-a concentrations, 1970-1985 155
48. Lake Erie central basin hypolimnion characteristics, 1970-1985. 163
49. Total phosphorus loadings to the Great Lakes 168
50. Annual total phosphorus loadings used for the GLMB model, by
segment 169
51. Constant parameters used for the GLMB model, by segment 169
xv
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TABLES (continued)
Number Page
52. Turbulent exchange coefficients used for the GUXB model, by
segment 170
53. Data used to represent the total phosphorus settling velocity
for the Lake Michigan segment of the GLMB model 171
54. Comparison of biological and nutrient state variables
explicitly modeled by the WASP models of Lakes Michigan, Huron
and Erie 178
55. Annual total phosphorus loadings used for the WASP models 178
xvi
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AOOSiaWLEllGEMENrS
This work was supported by the Great Lakes National Program Office (GLNPO)
of the U.S. Environmental Protection Agency. The authors acknowledge the
contributions made by the Captain and crew of the R/V Roger R. Simons, the
scientists of Bionetics, Inc., the scientific and supervisory staff of the
EPA's Region V Central Analytical Laboratory; and the scientific and
supervisory staff of the Great Lakes National Program Office. Many useful
suggestions for improvement of the text were provided by the following
reviewers: Steven C. Chapra, Laura A. Fay, and Claire L. Schelske.
Remaining errors of fact or interpretation, of course, are the
responsibility of the authors. We also thank Ms. Valeshia Cash, who
skillfully typed the text and tables.
xvi i
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TTTAX
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FOREWORD
The Great Lakes National Program Office (GLNPO) of the United States
Environmental Protection Agency was established in Region V, Chicago,
Illinois to focus attention on the significant and complex natural
resource represented by the Great Lakes.
The GLNPO implements a multidisciplinary environmental management
program drawing on a wide range of expertise represented by universities,
private firms, state, federal, and Canadian governmental agencies, and
the International Joint Commission. The goal of the GLNPO program is to
develop programs, practices, and technologies necessary to achieve a
better understanding of the Great Lakes basin ecosystem and to eliminate
or reduce to the extent practicable the discharge of pollutants into the
Great Lakes system. The GLNPO also coordinates U.S. actions in fulfill-
ment of the Agreement between Canada and the United States of America on
Great Lakes Water Quality of 1978.
This report presents some of the results of the water quality
surveillance program conducted on Lakes Michigan, Huron, and Erie (the
middle Great Lakes) in 1985 by the GLNPO. This surveillance program is a
continuation of the program begun in 1983. The 1983 and 1984 results are
reported by Lesht and Rockwell (1985 and 1987). Since many of the
procedures and protocols, both in sampling and analysis, were similar in
the three years, this report includes much of the same background
information contained in the reports on the 1983 and 1984 survey. The
present report contains an analysis of the 1985 data, which is then
compared with the 1983 and 1984 results.
xix
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WATER QUALITY IN THE MIDDLE GREAT LAKES:
RESULTS OF THE 1985 USEEA SURVEY OF LAKES
ERIE, HURON AND MICHIGAN
by
David C. Rockwell
U.S. Environmental Protection Agency
Douglas K. Salisbury
Applied Technology Division
Computer Sciences Corporation
and
Barry M. Lesht
Center for Environmental Research
Argonne National Laboratory
ABSTRACT
Continuing a limited annual program begun in 1983, the U.S. Environmental
Protection Agency's Great Lakes National Program Office surveyed the
water quality of Lakes Erie, Huron and Michigan (the Middle Great Lakes)
in 1985. A helicopter survey was completed in winter during January and
February, and three ship surveys were conducted in spring, summer, and
fall. The samples were analyzed for the traditional limno logical
parameters and for nutrients. The data were compared with the results of
the 1983 and 1984 surveys. Although many measurements of water quality
were unchanged from 1983 to 1985, the physical conditions, notably
temperature, were much different; 1983 was a mild year, while 1984 and
1985 were much colder. In 1985 the stratification for each lake spanned a
longer period than in 1983 and 1984. All three lakes exhibited a pattern
of nutrient depletion from the epilimnion and concurrent enrichment of the
hypolimnion during the summer. However, in 1985, the magnitude of the
depletion for some parameters was greater than observed in 1983 and 1984.
During the fall survey before and after "fall overturn" measurements of
chemical concentrations were obtained. Concentrations of total phosphorus
continue to be low in Lakes Michigan and Huron, and seem to be declining
in Lake Erie. Nitrate + nitrite nitrogen concentrations are consistently
increasing in all three lakes. Chloride concentrations are increasing in
Lakes Huron and northern Lake Michigan, but continue to decrease in Lake
Erie. The chloride concentration in southern Lake Michigan was unchanged
between 1984 and 1985 which may be a significant change from the previous
years of constant increases. The Great Lakes Mass Balance Model
illustrates how the lakes might be expected to respond to recent
historical changes in phosphorus loading. In Lake Michigan, Lake Huron
and the three basins of Lake Erie predicted concentrations of total
phosphorus decreased over the modeled period.
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TECHNICAL SUMMARY
The water-quality surveillance program begun in 1983 to sample the
open waters of Lakes Michigan, Huron and Erie (the middle Great Lakes)
was continued in 1985. The principal objectives of the program were (1)
to determine the water quality of the three lakes, especially with regard
to the concentration of nutrients in the open waters; (2) to continue the
program of annual sampling so as to provide data necessary for detection
and evaluation of both trends and annual variability in water quality;
and (3) to provide data relevant to the ongoing verification and
modification of the nutrient-based eutrophication models that have been
developed in conjunction with previous Great Lakes surveillance. The
major findings of the 1985 survey are summarized below; the details of the
analyses and statistical summaries (SAS, 1982 and 1985) and tables
presenting the results are included in later sections.
GENERAL FINDINGS
Sampling
The sampling network that had been used in the first two years of the
program (1983 and 1984) was modified in response to recommendations made
by the International Joint Commission's Lake Task Forces (IJC, 1986).
Analysis of historical data, including data from previous intensive
surveys, shows that the 1985 sampling network is comparable to the
1983/1984 network and is representative of the well-mixed, open-lake areas
that the program was designed to sample.
Surveys were conducted during the spring (April-May), summer
(August), and fall (November-December). In general, the lakes were warmer
in 1985 than in 1984 but cooler than in 1983. As expected, Lake Michigan,
Lake Huron and the eastern basin of Lake Erie were isothermal during the
spring survey. However, the western basin of Lake Erie was stratified and
the western part of the central basin of Lake Erie was beginning to
stratify during the spring sampling.
Spatial variability of the sampled parameters during the spring
survey was smaller in 1985 than in 1984 and 1983. This variability was
similar to the analytical uncertainty estimated as part of the quality
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control program in all basins, except western Lake Erie, indicating the
relative homogeneity of the open waters and the adequacy of the sampling
program. The criterion of detection (COD) established using the quality
control data was well below environmental levels for almost all
parameters during every survey. The COD for dissolved reactive
phosphorus was near environmental levels and the COD for dissolved
reactive silicon was above environmental levels during the fall survey.
Spatial Segmentation
The ascription of stations to the traditional lake basins was
essentially the same in 1985 as in previous years. However, in order to
conform more closely with basin definitions used in some numerical models
(Rodgers and Salisbury, 1981a and b; DiToro and Matystik, 1980), two
stations, L. Mich 27 and L. Huron 27, were considered to be in the
southern basins of each lake rather than in the northern basins.
With the exception of Lake Erie, consistent differences in parameter
values in adjacent basins were not found in 1985. This is in contrast to
the findings of the 1984 survey, when all three lakes exhibited consistent
differences in some parameters, notably dissolved reactive silicon and
dissolved nitrate+nitrite nitrogen. The pattern of the differences found
in 1984 suggested that the rate of phytoplankton growth and nutrient
uptake was higher in the southern basins of Lakes Huron and Michigan than
in the respective lakesTs northern basins during the periods of sampling.
In 1985 the southern basins showed slightly higher biomass (chlorophyll-a)
than the northern basins, but lower rates of nutrient uptake (silica and
nitrogen) during the summer and Fall-1 surveys. The observations of basin
differences in many parameters are probably related to the annual patterns
of lake warming, which differ from year to year.
Vertical Segmentation
As was the case in 1983 and 1984, vertical concentration gradients
were observed in all the deeper basins after stratification. Nutrients
were depleted in the epilimnion of each lake during the summer. Simmer
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silica depletion observed in 1985 in Lakes Huron and Michigan was greater
than in either 1983 or 1984.
All of the deep (>50 m) basins developed turbid nepheloid layers
that contained high concentrations of dissolved nutrients and particles.
The concentrations of many nutrients were significantly higher in the
nepheloid layers than in the hypolimnion of Lakes Huron and Michigan
during the summer survey (Table 20), while in Lake Erie's eastern basin
the differences were not as great. The magnitude of dissolved nutrient
enrichment in the nepheloid layer in Lakes Huron and Michigan was greater
in 1985 than in the previous years.
NUTRIENT
Phosphorus
Lake Michigan; The surface concentrations of total phosphorus
measured in the spring in the well-mixed, open waters of Lake Michigan
were 4.8 + 0.7 ug/L south and 5.6 + 1.7 ug/L north (mean + one standard
deviation) ; these values are virtually the same as those measured in the
spring of 1984 (4.8 + 0.9 ug/L south, 6.2 + 3.0 ug/L north). Total
phosphorus concentrations in the epilimnion declined during the year
until the Fall-2 survey when mixing throughout the water column
redistributed nutrients. Increases in the concentration of total
phosphorus in the nepheloid layer mirrored the decreases in the
epilimnion.
Total phosphorus concentrations have remained stable in Lake
Michigan since the late 1970s. Since the inception of the annual
monitoring program in 1983, the spring open lake total phosphorus levels
have been as much as 30% below the International Joint Commission (1980)
target concentration of 7 ug/L in both the northern and southern basins.
Lake Huron; Springtime surface concentrations of total phosphorus
in Lake Huron were 10% to 20% lower in 1985 (3.0 + 0.5 ug/L) than in 1983
(3.6 + 0.7 ug/L)- The 1985 levels are the lowest values measured in the
last fifteen years. Epilimnion concentrations decreased during the
summer to 2.8 ug/L north and 2.3 ug/L south, while the southern basin
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nepheloid layer concentration increased to 4.2 ug/L. During the winter
(January-February 1985) the highest concentrations observed were 3.5 ug.L
north and 4.0 ug/L south. These values are well below the IJC (1980)
target level of 5 ug/L.
Lake Erie; Spring-averaged, volume-weighted (by strata), open-lake
total phosphorus concentrations in all three basins of Lake Erie were
observed at their lowest levels since the start of the annual
surveillance program. On an annualized basis, the 1985 total phosphorus
concentrations were virtually unchanged from 1984 in the western (23.5
ug/L) and central (15.0 ug/L) basins. The concentration in the eastern
basin (11.0 ug/L) was lower than measured in 1984. Assuming a linear
trend, the rates of decrease in total phosphorus concentration over the
last three years in both the central and eastern basins were
statistically significant and estimated to be 0.65 ug/L/yr (central) and
0.95 ug/L/yr (eastern).
Nitrate + Nitrite
Lake Michigan; Springtime nitrate + nitrite nitrogen concentrations
in the surface waters of Lake Michigan were higher in 1985 than in either
1983 or 1984. Mean concentrations in 1985 were higher (alpha = 0.05)
both in the southern (287 ug/L) and northern (297 ug/L) basins than in
1983 (259 ug/L south, 262 ug/L north). There is a step increase in
concentration in 1985 over the apparent rate of increase of 2 ug/L per
year from 1977 through 1984.
In both basins, the 1985 epilimnetic depletion of nitrate + nitrite
nitrogen from spring survey maxima, resulted in a 46% decrease in both
basins (minima were 156 ug/L northern and 159 ug/L southern). During the
summer survey, maximum observed enrichment occurred in the nepheloid
layer in the northern basin (314 ug/L) and in the southern basin (330
ug/L) during the fall survey. In both basins, increased nitrate + nitrite
nitrogen concentrations were observed in the hypoliinnion in the fall
survey.
-------
Lake Huron; The concentration of nitrate + nitrite nitrogen in the
open-lake surface waters of Lake Huron was 302 + 24 ug/L during the spring
of 1985. This is a lower concentration, but is virtually unchanged from
1983 and 1984. Epilimnetic depletion of nitrate + nitrite nitrogen from
observed spring survey concentrations resulted in a 12% decrease in the
northern basin to 267 ug/L and a 9% decrease in the southern basin to 276
ug/L. Maximum observed enrichment of nitrate + nitrite nitrogen occurred
in the nepheloid layer (354 ug/L in the northern basin and 363 ug/L in the
southern basin). Hypolimnion concentration increases were noted in both
basins during the sunmer survey.
Lake Erie: In 1985, spring surface open-lake nitrate + nitrite
nitrogen concentrations in the western and central basins of Lake Erie
were at intermediate values between those found in 1983 and 1984.
Western Lake Erie 1985 annual average (3 ship surveys) concentration was
446 ug/L- This compares with 502 ug/L (1984) and 321 ug/L (1983).
Central Lake Erie 1985 annual average survey concentration was 178 ug/L.
The corresponding concentrations were 219 ug/L in 1984 and 147 ug/L in
1983. Eastern Lake Erie 1985 annual average survey concentration was 256
ug/L. The corresponding annual concentrations were 266 ug/L in 1984 and
219 ug/L in 1983. The spring nitrate + nitrite nitrogen concentrations
were comparable in all basins with the helicopter winter surveys, except
in the western basin. In the western basin the spring average nitrate +
nitrite nitrogen concentration was 699 ug/L, which represents an unusually
high concentration for Lake Erie in 1985. Similar high concentration
levels were observed in spring 1984 (818 ug/L to 962 ug/L).
Silica
Lake Michigan; Concentrations of dissolved reactive silicaa in the
open waters of Lake Michigan in 1985 were slightly higher than 1984 levels
in the southern basin and unchanged in the northern basin. Concentration
levels have stayed within a 0.3 mg/L range (0.9 to 1.2 mg/L) in both
a Analytical determinations of dissolved reactive silicon were made
in 1985. These values have been converted to dissolved reactive silica
when appropriate for comparison with previously reported data.
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8
basins since the late 1970s. Based on spring surface sanples, the 1985
concentrations were found to be 1.21 + 0.04 mg/L (south) and 1.16 + 0.06
mg/L (north). Maximum average observed dissolved reactive silicon was
measured in the Fall-1 survey nepheloid layer inboth basins: 2.49 mg/L in
the northern basin and 2.00 mg/L in the southern basin.
Epilimnetic depletion of dissolved reactive silica was 83% from the
spring survey (1.20 mg/L in the northern basin and 1.21 mg/L in the
southern basin) to the summer survey (0.20 mg/L in the northern basin and
0.21 mg/L in the southern basin). Enrichment of the hypolimnion and
nepheloid layers occurred in both basins.
Lake Huron; Spring surface dissolved reactive silica levels measured
in the open waters of Lake Huron in 1985 (1.66 + 0.04 mg/L) were between
the 1983 levels (1.64 + 0.05 mg/L) and 1984 levels (1.68 + 0.12 mg/L).
These mid-1980 levels are higher (alpha = 0.05) than previously found in
the early 1970s and suggest an annual rate of increase between 0.01 to
0.02 mg/L/year from the early 1970s.
Epilimnetic depletion of dissolved reactive silica was 52% in the
southern basin, with the observed summer survey measured at 0.72 mg/L.
In the northern basin the epilimnetic depletion was 45%, with the
observed summer survey measured at 0.90 mg/L. The nepheloid and
hypolimnion were enriched in both basins with dissolved reactive silica
increasing to a maximum in the nepheloid layer in the Fall-1 survey in
the northern basin (2.21 mg/L) and in the summer survey in the southern
basin (2.27 mg/L).
Lake Erie; Except in the western basin, Lake Erie dissolved
reactive silica concentrations in 1985 were found to be lower than levels
found in 1984. Western basin spring surface samples showed a large
increase averaging 1.30 + 0.28 mg/L in 1985 as compared to 0.80 + 0.60
mg/L in 1984 and 0.89 + 0.59 mg/L in 1983.
-------
Dissolved reactive silica concentrations remained extremely low in
the central basin at 0.02 + 0.01 mg/L in 1985, returning to levels
observed in 1983. The eastern basin average silica concentration of 0.14
+ 0.02 mg/L in 1985 was lower than 1984 (0.22 + 0.06 mg/L) but higher than
1983 (0.04 + 0.01 mg/L)-
Western basin dissolved reactive silica concentrations decreased
during 1985 and were measured during the summer survey at 0.70 mg/L or 48%
lower than spring levels. However, central and eastern basin silica
concentrations increased in the epilimnion as the season advanced.
Evidence of hypolimnion and nepheloid layer enrichment was observed
in both the central and eastern basins. The maximum observed dissolved
reactive silica concentration (3.31 mgA) occurred in the central basin
hypolimnion during summer anoxia and in the eastern basin nepheloid layer
(0.73
MAJOR
ftnions — Chloride f Sulfate, and Carbonate
Lake Michigan; Chloride concentrations in 1985 were observed to be
lower in the surface waters of southern Lake Michigan at 8.72 + 0.23 mgA
from 8.90 + 0.28 mgA in 1984. In the surface waters of northern Lake
Michigan, chloride remained virtually unchanged at 8.83 + 0.41 mgA in
1985 from 8.84 ± 0.22 mgA in 1984. Corresponding values in 1983 were
8.78 + 0.33 mgA southern basin and 8.68 + 0.23 mgA northern basin.
The 1985 spring concentrations of sulfate in Lake Michigan (22.1 +
0.08 mgA southern basin and 22.2 + 0.3 mgA northern basin) were higher
in the southern basin and virtually unchanged in the northern basin
compared to 1983 and 1984. Corresponding mean values in the southern
basin were 21.8 mgA (1984) and 21.4 mgA (1983) and in the northern
basin were 22.2 mgA (1984) and 21.2 mgA (1983).
Alkalinity values were virtually the same in the northern basin at
107.7 ± 1.8 mgA CaCC>3 and in the southern basin at 108.4 + 1.5 mgA
CaC03. Corresponding values were 108.7 mgA (1984) and 108.1 mgA (1983)
-------
10
in the northern basin and 107.7 mg/L (1984) and 109.0 mg/L (1983) in the
southern basin.
Lake Huron; Chloride values continue to be low in Lake Huron. The
mean northern basin concentration (5.39 + 0.11 mg/L) and the mean
southern basin concentration (5.35 ± 0.14 mg/L) are the lowest mean
spring values measured during the annual program since 1983.
Corresponding northern basin values were 5.49 + 0.14 mg/L in 1984 and 5.54
+ 0.25 mg/L in 1983, and southern basin values were 5.87 + 0.34 mg/L in
1984 and 5.79 + 0.36 mg/L in 1983.
As with chloride, both sulfate and alkalinity concentrations were
low in Lake Huron. Spring 1985 sulfate concentrations were 15.89 + 0.41
mg/L and 15.69 ± 0.48 mg/L in the northern and southern basins,
respectively. These are statistically unchanged from the 1984 values of
15.97 + 0.42 mg/L and 16.94 + 2.07 mg/L in the northern and southern
basins, respectively.
Alkalinity values in 1985 averaged 76.50 + 1.05 mg/L and 77.56 +
1.11 mg/L in the northern and southern basins. These can be compared
with 1984 results of 77.45 + 1.71 mg/L and 77.21 + 1.29 mg/L,
respectively. These values remain virtually unchanged from 1983.
Lake Erie; Chloride levels in Lake Erie continue to be the highest
of the three sampled lakes. On an annual basis, volume weighted average
(VWA) concentrations were the lowest and most variable in the western
basin over the last three years 11.74 + 1.95 mg/L (1983), 12.62+ 3.39 mg/L
(1984), and 11.10 + 1.75 mg/L (1985) due to the inflow of Lake Huron
water, which has low chloride concentrations. Concentration levels tend
to increase from west to east during 1983 through 1985. In 1985,
chloride VWA concentrations were not significantly different between the
central (14.65 + 0.02 mg/L) and eastern (14.82 + 0.18 mg/L) basins.
Historical data show a steady decline in chloride concentrations since
1966 (~24.0 mg/L) in the central basin. The 1985 central basin VWA annual
average is lower than the 1984 VWA average (14.80 + 0.12 mg/L).
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11
Sulfate VWA concentrations are virtually unchanged from
concentrations reported in 1984. The 1985 concentration values of 19.14 +
0.81 mg/L, 23.00 + 0.31 mgA and 23.17 + 0.06 mgA in the western,
central, and eastern basins can be compared with 20.35 + 1.71 mgA/ 23.18
±0.13 mg/L and 23.71 mg/L measured in 1984. Sulfate concentrations have
not declined from average levels reported throughout the seventies (22.6
+0.4 mg/L).
Measurements of 1985 VWA alkalinity concentrations of 84.11 + 1.65
mg/L, 92.65 + 0.56 mg/L and 93.30 + 0.89 mg/L in the western, central,
and eastern basins are not significantly lower than 1984 measurements
(86.29 + 2.05 mgA, 93.69 ± 0.77 mg/L and 96.45 ± 0.68
Cations — Calcium, Magnesium, Sodium, and Potassium
Lake Michigan; Cation concentrations were determined during the
summer survey in 1985. The epilimnion concentration of calcium, the
major cation present, was 35.2 + 0.2 mgA and 36.0 + 0.2 mgA in the
northern and southern basins, respectively. Comparable mean values
measured in 1984 were 35.2 mgA in both basins.
Of the other cations measured, magnesium measured 11.2 + 0.1 mgA
and ll.O + 0.00 mgA in the northern and southern basins, respectively
(11.0 mgA in both basins in 1984 and 11.7 mgA north, 12.0 mgA south in
1983). Sodium averaged 5.5 + 0.03 mgA and 5.4 + 0.02 mgA in the
northern and southern basins, respectively (4.8 mgA north and 4.7 mgA
south in 1984 and 5.0 mgA north and 5.2 mgA south in 1983). Potassium
averaged 1.21 + 0.004 mgA and 1.23 + 0.003 mgA in the northern and
southern basins, respectively (1.30 mgA north, 1.29 mgA south in 1984
and 1.20 mgA north, 1.23 mgA south in 1983).
The cation concentrations are little changed from previous years
except for sodium concentrations which were higher in both basins. The
large year-to-year variation in sodium concentrations in the northern and
southern basins was not expected and may be due to analytical problems.
Only calcium appeared to be enriched within the nepheloid layer (35.9
mgA north and 36.4 mgA south).
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12
Lake Huron: Lake Huron's cation concentrations are lower than Lake
Michigan's. Calcium concentrations were 26.2 + 0.3 mg/L and 27.8 + 0.2
mgA in the northern and southern basins, respectively (26.1 mg/L north
and 27.5 mg/L south in 1984 and 28.0 mg/L north and 29.3 south in 1983).
The epilimnion concentrations of the other cations were: magnesium in
1985 was 7.3 + 0.03 mg/L north and 7.4 + 0.04 mg/L south (7.0 mg/L north,
7.4 mg/L south in 1984), (7.3 mg/L north, 7.7 mg/L south in 1983); sodium
in 1985 was 3.4 + 0.02 mg/L north and 3.6 + 0.02 mg/L south (3.0 mg/L
north, 3.3 mg/L south in 1984), (3.2 mg/L north and 3.4 mg/L south in
1983); and potassium in 1985 was 0.87 + 0.01 mg/L north and 0.90 + 0.01
mg/L south (0.93 mg/L north, 0.97 mg/L south in 1984) (0.88 mg/L/ 0.93
mg/L south in 1983).
Cation concentrations in 1985 were intermediate between 1983 and
1984 observations except for sodium concentrations which were higher in
both basins in 1985. All cation concentrations appeared to be elevated
within the nepheloid layer in the northern basin while in the southern
basin there was no apparent enrichment.
Lake Erie; Calcium is the major cation in Lake Erie, as in the
other lakes, with concentrations in the western, central and eastern
basins measured in the epilimnion in summer at 29.9 + 0.4 mg/L 35.0 + 0.1
mg/L, and 35.5 + 0.2 mg/L, respectively. These values were 31.2 mg/L,
34.4 mg/L, and 35.8 mg/L in 1984 and 34.9 mg/L, 38 mg/L, and 34.9 mg/L in
1983.
No consistent patterns were observed in magnesium with 1985
concentrations at 8.1 + 0.7 mg/L, 8.4 + 0.2 mgA, and 8.3 + 0.1 mg/L.
These values in 1984 were at 8.0 mgA, 8.2 mgA, and 8.2 mgA and were at
8.3 mgA, 8.3 mgA and 7.4 mgA in 1983.
Sodium concentrations in 1985 were 6.0 + 0.2 mgA, 8.6 + 0.1 mgA,
and 8.9 + 0.1 mgA. These values in 1984 were 5.9 mgA, 7.6 mgA, and
7.8 mgA and in 1983 were 6.4 mgA 8.0 mgA, and 7.4
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13
Potassium concentrations in 1985 were 1.18 ± 0.03 mg/L, 1.33 ± 0.004
rog/L, and 1.35 ± 0.008 mg/L- These values in 1984 were 1.24 mg/L, 1-42
mg/L, and 1.49 mg/L and in 1983 were 1.20 mg/L, 1.26 mg/L/ and 1.35 mg/L.
IVbst cation concentrations in 1985 were at intermediate levels when
compared to 1983 and 1984 except for sodium which was higher in 1985 in
the central and eastern basin when compared to the two previous years.
OTHER PARAMETERS
Specific Conductance
Combined changes in the concentrations of major ions are reflected
in changes in the measured specific conductance, or conductivity. In
accordance with the small changes in the concentration of major ions,
conductivity measurements in 1985 were virtually unchanged from 1983 and
1984 levels in most basins. Spring mean epilimnetic conductivities were
279.8 ±0.8 uS/cm and 279.3 + 0.9 uS/on in the southern and northern
basins of Lake Michigan, respectively (1984 mean levels were 280.0 uS/cm
and 277.1 uS/cm and 1983 mean levels were 279.1 uS/cm and 278.2 uS/cm);
202.7 ± 1.2 uS/cm in the southern and northern basins of Lake Huron
combined (1984 mean levels were 203.1 uS/cm and 1983 mean levels were
204.2 uS/cm); and 254.5 + 10.5 uS/cm, 276.2 + 2.9 uS/cm, and 276.4 + 1.84
uS/cm in the western, central, and eastern basins of Lake Erie,
respectively (1984 values were 273.0 uS/on, 276.0 uS/cm, and 281.7 uS/cm;
1983 values were 259 uS/cm, 278.1 uS/cm, and 289.1 uS/cm).
Dissolved Oxygen
Historically, anoxia has been a problem both in the western and
central basins of Lake Erie. In the western basin, anoxia events are
episodic, while in the central basin anoxia has occurred regularly. In
August 1985, the average dissolved oxygen concentration was a minimum in
the central basin hypolimnion layer at 1.3 mg/L. This value is much
lower than those measured in 1983 (3.7 mg/L) and 1984 (3.9 mg/L). The
hypolimnion thicknesses in 1985 was estimated at 1.6 meters. Previous
hypolimnion thickness were 4.3 m (1984) and 5.4 m (1983). The anoxic
condition observed in 1985 resulted from the on going oxygen depletion,
the thin hypolimnetic layer, and the longer than normal period of
stratification.
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14
TROPHIC STATUS
Dobson et al. (1974) established a sinple set of criteria for
trophic classification of the Great Lakes. These criteria are based on
the amount of particulate phosphorus and chlorophyll-a in the surface
waters, as well as the Secchi depth. Using the Dobson criteria for the
ship-borne surveys, the open waters of Lakes Michigan and Huron may be
classified as oligotrophic, and Lake Erie waters are evaluated over the
entire range from eutrophic-mesotrophic-oligotrophic depending on the
parameter involved.
The most frequent classification for the western basin is eutrophic
and the most frequent classification for the central basin and eastern
basins is oligotrophic. When other classifications are used
(International Joint Commission, 1976a; Rast and Lee, 1978), the most
frequent classification for Lake Erie's central basin would be either
mesotrophic or oligotrophic. The classifications based on phosphorus,
chlorophyll-a, and Secchi depth are different for some basins than a
classification scheme based on aerobic heterotrophs (Rockwell et al. ,
1980). Using aerobic heterotrophs, the southern basin of Lake Michigan
and the eastern and central basins of Lake Erie would be classified
mesotrophic. The aerobic heterotroph evaluations are not changed from
previous years for most basins. Using this system, the classification of
the central basin of Lake Erie has changed from eutrophic to oligotrophic
in 1983 to mestrophic to oligotrophic in 1985, suggesting overall that the
central basin appears to be improving.
RESPONSE TO LOADS — M3DEL COMPARISONS
Surveillance data were compared to the predictions of two types of
mathematical models, one a sinple, multi-segment, mass-balance model for
total phosphorus (Chapra, 1977), and the other a dynamic eutrophication
model relating several water-quality variables to phosphorus loading
(DiToro and Connolly, 1980; DiToro and Matystik, 1980; Rodgers and
Salisbury, 1981a). The mass balance model, GLMB, was used to hindcast
annual averages of total phosphorus concentrations from 1974 to 1985. The
GLMB model predicts the decreasing long-term trends observed in the
surveillance data very well. The simple GLMB model readily provided the
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15
ability to confirm trends observed in the annual total phosphorus
surveillance data. The dynamic eutrophication model, WASP, was used to
hindcast station averages of ortho and total phosphorus and chlorophyll-a
concentrations collected by the GLNPO during 1983, 1984 and 1985. The
ability of the WASP model to predict the temporal trends and the
concentration magnitudes of the surveillance data varied between the
segments and parameters. The complex WASP model allowed examinations of
the effect on related parameters resulting form varying the settling
velocity of particulate in Lake Michigan and the phosphorus loadings in
Lake Huron.
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16
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17
INIRQDUCTICN
SCOPE
Continuing the open lake surveillance begun in 1983 to establish a
long-term, annual water quality data base for the Great Lakes, the Great
Lakes National Program Office (GLNPO) of the United States Environmental
Protection Agency (USEPA) conducted an optimized program of water quality
monitoring in the relatively homogeneous offshore water of Lakes
Michigan, Huron, and Erie during 1985. This surveillance program is
designed to provide information to evaluate the progress of the
phosphorus remedial control efforts.
The GLNPO program is an outgrowth of the Great Lakes International
Surveillance program (GLISP), (International Joint Conmission (IJC),
1975), which is designed to comply with the provisions of the 1978
Canada-United States Water Quality Agreement that calls for periodic
monitoring of the Great Lakes to determine the degree to which the
objectives of the agreement are being met. More specifically, the 1985
program was intended to collect water quality data for use in
nutrient-based lake eutrophication models and to add to the annual water
quality database for these lakes. The current GLNPO surveillance program
incorporates the major open-lake surveillance features of the 1986 GLISP
plans for Lake Huron and Lake Erie. The GLNPO plan is less extensive
(fewer stations) than the GLISP plan for Lake Huron and less frequent
(fewer surveys) than the GLISP plan for Lake Erie. The GLNPO plan
focuses exclusively on the relatively homogenous waters of each lake
during the isothermal periods and the stable, stratified surrmer period.
By explicitly excluding nearshore areas from consideration and by
limiting the surveys to three distinct periods during the year, the
program makes efficient use of the limited resources available.
GENERAL PLAN AND RATIONALE
The 1985 GLNPO monitoring program follows the general GLNPO survey
design developed for the 1983 program. The major difference of the 1985
plan is the station pattern alteration to include sites recommended by
the Lake Michigan and Lake Erie task forces. The current GLNPO
surveillance plan is conceived as an annual program. This change from
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18
the 1975 GLISP design is based on the recognition that the annual
variability in water-quality observations made in the Great Lakes may far
exceed any trend discernable from less frequent measurements.
This effort is focused on chemical eutrophication and the whole lake
response to changes in phosphorus loading, therefore, sampling is
restricted to lakes considered susceptible to eutrophication (Lake
Superior is not affected by eutrophication) and to the offshore waters.
(Lake Ontario is excluded since Canada conducts annual monitoring of its
water quality.) Resource limitations required a reduction in both the
spatial extent and the within-year frequency of sampling (relative to the
1986 GLISP). For the long-term objectives of the GLNPO plan these are not
serious restrictions. Over a period of years, each lake will be sampled
more frequently under this plan than under the 1975 GLISP.
The GLNPO plan is based on three sampling periods during the year -
spring isothermal, summer stratified, and after the fall water column
overturn. The later sampling period used a ship in late fall/early
winter (November - December) and/or a helicopter in mid-winter
(January-February).
Each of the sampling surveys consists of as many runs (legs) from
the Lake Michigan western end of the survey track (Chicago, ID to the
Lake Erie eastern end (Dunkirk, NY) as are possible in the three-week
period allowed for each survey. Multiple survey legs provide a form of
replication ensuring that some of the data collected is not biased by
transient events. In 1985 a steering motor defect interrupted and
delayed the spring survey for four days. Only two legs were run because
spring wanning had advanced in Lake Erie's central basin causing partial
stratification. As planned, three legs were completed during the summer
survey and two legs were completed in the fall.
The GLNPO surveillance program is unique in that all three lakes
were sampled by one agency, used one vessel, and used one principal
analytical laboratory. Thus, inter lake comparisons based on the data
collected during the program are not complicated by differences in
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19
sampling procedures, collection times, interlaboratory differences, or
analytical techniques.
Although the sampling network used in 1983 and 1984 was modified in
1985 in Lakes Michigan and Erie, and the 1983-1985 program is reduced in
areal scope from previous intensive surveillance programs based on the
original Great Lakes Intensive Survey Plan, the results of 1985 efforts
were comparable with the 1983 and 1984 efforts and the earlier intensive
programs. The 1985 efforts are shown to be representative of the well-
mixed, open-lake areas that the program was designed to sample.
Surveys
Each survey period has a specific purpose within the context of the
objectives of the program. The first ship survey is conducted as early
as possible after ice out conditions in the Straits of Mackinac while the
water column is still isothermal and both vertically and horizontally
well-mixed. This provides data to establish estimates of the initial
concentrations of substances of interest. The second ship survey is
conducted during the summer period of lake stratification to determine
epilimnetic nutrient depletion and hypolimnetic enrichment of nutrients.
The third ship survey, conducted in the fall, is intended to survey
isothermal conditions after fall overturn. This goal was accomplished in
the shallower basins of Lakes Michigan and Huron and in Lake Erie. The
helicopter-borne surveys are conducted to provide data during the
mid-winter when ship-borne sampling is restricted by weather and ice
conditions. The mid-winter data provide estimates of water quality after
"fall overturn" mixing is complete. Nutrient concentrations are
expected to be highest during winter before nutrients are utilized by
diatoms during the spring (Schelske, 1975). The helicopter surveys are
conducted when the annual ice cover is expected to be of the greatest
extent. If the annual ice cover inhibits sediment resuspension due to
winter storm mixing, the water column may be least affected by biological
activity due to low temperatures and outside influences from tributary
loadings.
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20
Parameters
The water quality parameters measured as part of the 1985
surveillance program are listed in Table 1. These parameters were
selected because of their relevance to chemical eutrophication and
because of their importance as indicators of water quality. Several of
the parameters (chlorophyll-a, dissolved ortho-phosphorus, dissolved
reactive silicon, total nitrate + nitrite nitrogen, total ammonia
nitrogen) are used directly as state variables in the nutrient based
eutrophication models (DiToro and Matystik, 1980; DiToro and Connolly,
1980; Rodgers and Salisbury, 1981a) that have been developed for the
Great Lakes.
Other parameters (total Kjeldahl nitrogen, total phosphorus, and
total dissolved phosphorus) are used indirectly along with temperature
and turbidity as calibration and verification variables in the models.
Among the other parameters measured in this program, the conservative
ions, chloride and sulfate, have been noted to be increasing in
concentration in Lake Michigan (Rockwell et al., 1980) and in Lake Huron
(DoIan et al., 1983; MDll et al., 1985). Sodium concentrations in Lake
Michigan have also been increasing and may represent an emerging
environmental problem. These conservative parameters are also useful for
identification of homogeneous water masses. In addition to the
parameters mentioned above, dissolved oxygen was measured near the
bottom in Lakes Huron and Michigan and at all depths in Lake Erie. The
bacteriological parameter "total plate count" was also determined in each
lake as a measure of aerobic heterotroph levels.
Stations
Focusing on the relatively homogeneous open lake water mass is a key
feature of this surveillance plan. Under the 1975 GLISP plan, for
example, 92 stations were sampled in Lake Michigan, 67 in Lake Huron, and
82 in Lake Erie during each survey. The 1985 plan included 11 sites in
Lake Michigan, 10 of 20 stations per leg in Lake Huron, and 17 stations in
Lake Erie.
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21
Table 1. Parameters measured during the 1985 surveillance program.
Parameter
Air temperature
Wind speed
Wind direction
Barometric pressure
Secchi depth
Wave height
Wave direction
Water temperature
Turbidity
Specific conductance
Field pH
Laboratory pH
Total alkalinity (CaC03)
Dissolved oxygen
Aerobic heterotrophs
Chlorophyll-a
Pheophytin-a
Dissolved reactive silicon
Total Kjeldahl nitrogen
Total ND2 + ND3
Total NH3 + NH4
Total phosphorus
Total dissolved phosphorus
Dissolved ortho phosphorus^
Chloride
Sulfate
Calcium
Potassium
Sodium
Magnesium
STORE!
Codea
00020
82127
00040
00025
00078
70222
70220
00010
00076
00095
00400
00403
00410
00300
31749
32209
32213
01140
00625
00630
00610
00665
00666
00671
00940
00945
00916
00937
00929
00927
STORET
Units
degrees C
knots
azimuth
mm of Hg
meters
WM3 code
WM3 code
degrees C
Hach FTU
us/cm
SU
SU
mg/L
mg/L
# per mL
ug/L
ug/L
ug-Si/L
mg-N/L
mg-N/L
mg-N/L
mg-P/L
mg-P/L
mg-P/L
mg/L
mg-SO4/L
mg/L
mg/L
mg/L
mg/L
Surveys13 Depths
1-3
1-3
1-3
1-3
1-3
1-3
1-3
H,l-3
H,l-3
H,l-3
H,l-3
H
H,l-3
H,l-3
1-3
H,l-3
H,l-3
H,l-3
H,l-3
H,l~3
H,l-3
H,l-3
H,l-3
H,l-3
H,l-3
H,l-3
2
2
2
2
_— .
All
All
All
All
All
All
Bottom0
All
All
All
All
All
All
All
All
All
All
All
All
Surface, B2/B1
Surface, B2/B1
Surface, B2/B1
Surface, B2/B1
^ Numerical code used for data retrieval from STORET.
D H = Helicopter mid-winter survey; 1 = early spring survey; 2 = summer
survey; and 3 = fall survey.
c Dissolved oxygen was measured at all depths in Lake Erie.
Often referred to as dissolved (or soluble) reactive phosphorus.
Each of the stations selected for sampling are GLISP stations deemed
to be representative of the open lake (explicitly excluding nearshore
areas). Because it is anticipated that many of the results of this survey
will be expressed in terms of averages of the parameter values, it is
inportant that the individual samples making up the averages come from
-------
22
homogeneous areas of the lakes. Therefore, the sampling stations were
selected within areas identified as homogeneous by analysis of the earlier
GLISP surveys (Kwiatkowski, 1980; Lesht, 1984b; Moll et al. , 1985;
El-Shaarawi, 1984a). The locations of the stations are mapped in Figures
1-3, and the exact locations and approximate station depths are listed in
Table 2. Master stations are those located at the deepest sounding at
which additional samples were taken in the upper fifty meters. Each
station was sampled during each survey leg, except in Lake Huron. In Lake
Huron half of the stations were sampled on each leg because of the large
number and great spacing of the stations. This was accomplished by
surveying the eastern or western sides of the northern and central basin
and in a zig-zag fashion in the southern basin. The helicopter and ship
sampling times (Julian day and Greenwich time) for the 1985 surveys are
shown in Tables 3 through 6.
Sample Depths
Water samples were collected throughout the water column at each
station. The criteria for choosing sampling depths were based on the
thermal structure of the water column. During isothermal conditions,
samples were taken in Lakes Michigan and Huron at the surface (one meter
depth), mid-depth, ten meters above the bottom, and two meters above the
bottom, while in Lake Erie the western and central basins were sampled at
the surface (one meter) mid-depth, and one meter above the bottom. The
western basins was sampled at surface (one meter depth), mid-depth, ten
meters above the bottom, and one meter above the bottom. At sites where
the water column was sufficiently deep, one-hundred meter and two-hundred
meter samples were taken during all surveys.
When the water column was thermally stratified in Lake Michigan and
Huron, samples were taken at the surface (one meter depth), within the
lower epilimnion, one meter above the knee of the thermocline, at the
thermocline in the upper hypolimnion, one meter below the knee of the
thermocline, ten meters above the bottom, and two meters above the bottom.
In Lake Erie, the sampling regime added a mid-thermocline sample and moved
the bottom sample to one meter above the bottom as required by the Lake
Erie GLISP.
-------
23
H
Surveillance Stations
1985
Master Station
Helicopter Station
Located differently
From ship station
Green Bay
Harbor Springs
Milwaukee
SCALE
0 25 50 Miles
I I ' I I1
0 25 50 75 Kilometers
Benton Harbor
Chicago
Michigan City
Hammond
Figure 1. Location of 1985 surveillance stations in Lake Michigan.
-------
24
CANADA
H
Master Station
H«licopt*r Station
Located diff«r«ntlv
From chip station
I I . .'
I I I I
SO Miles
25 50 75 Kilometers
Figure 2. Location of 1985 surveillance stations in Lake Huron.
-------
®
Surveillance Station*
1985
H
Mailer Station
Helicopter Station
Located differently
From ship station
LAKE ONTARIO
Toledo
Detroit
Cleveland
Erie
SCALE
Buffalo
50 Miles
_J
25 50 75 Kilometers
Figure 3. Locations of 1985 surveillance stations in Lake Erie.
-------
26
Table 2. Station locations and depths—1985 surveillance program.
STOKET
Station
Designation3-
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
MICH
MICH
MICH
MICH
MICH
MICH
MICH
MICH
MICH
MICH
MICH
MICH
MICH
MICH
MICH
MICH
MICH
MICH
11
11H8502
17
18
18H8502
19
23
23H8502
27
27H8502
32
34
34H8502
40
41
41H8502
47
47H8502
HURON 06
HURON
HURON
HURON
HURON
HURON
HURON
HURON
HURON
HURON
HURON
09
09H8501
09H8502
12
15
15H8501
15H8502
27
29
32
HURON 32H8501
HURON
HURON
HURON
HURON
HURON
HURON
HURON
HURON
HURON
HURON
HURON
HURON
HURON
HURON
HURON
32H8502
37
37H8501
37H8502
38
43
45
45H8501
45H8502
48
53
54
54H8502
57
57H8502
Latitude
(north)
42
42
42
42
42
42
43
43
43
43
44
44
44
44
44
44
45
45
43
43
43
43
43
44
44
44
44
44
44
44
44
44
44
44
44
45
45
45
45
45
45
45
45
45
45
23
23
44
44
43
44
08
08
36
36
08
05
05
45
44
44
10
10
28
42
38
37
53
00
00
00
11
22
27
38
27
45
53
45
44
00
08
09
08
16
27
31
31
40
39
00.
06.
00.
00.
48.
00.
00.
12.
00.
00.
24.
24.
00.
36.
12.
36.
42.
46.
00.
00.
00.
42.
24.
00.
00.
06.
54.
00.
12.
24.
02.
42.
25.
43.
24.
48.
12.
00.
14.
42.
00.
00.
02.
00.
56.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Longitude Approximate Depth
(west) (meters)
87
86
87
87
86
86
87
87
86
86
87
86
86
86
86
86
86
86
82
02
82
82
82
82
82
82
82
81
82
83
82
82
83
82
82
82
82
83
82
82
82
82
83
83
83
00
38
25
00
36
35
00
00
55
55
14
46
46
58
43
43
22
22
00
01
13
12
03
21
37
20
30
50
20
07
38
47
05
46
03
00
59
03
58
27
54
25
24
43
44
00
18
00
00
18
00
00
24
00
00
00
00
00
00
18
48
30
20
00
00
00
48
24
00
07
55
12
00
30
00
50
00
41
59
36
30
00
24
59
06
54
00
48
36
20
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
.0
136
66
107
168
97
86
100
89
116
94
159
160
160
160
251
260
186
190
46
59
60
60
86
66
68
68
50
137
73
51
51
73
70
70
137
219
101
113
113
115
90
91
15
132
75
-------
27
Table 2. (Continued) Station locations and depths—1985 surveillance
program.
STORET
Station
Designation3
L. HURON 61
L. HURON 61H8502
L. HURON 90
L. HURON 90H8501
L. HURON 90H8502
L. HURON 91
L. HURON 92
L. HURON 93
L. ERIE 09
L. ERIE 09H8501
L. ERIE 09H8502
L. ERIE 10
L. ERIE 15
L. ERIE 15H8501
L. ERIE 15H8502
L. ERIE 18H8501
L. ERIE 18H8502
L. ERIE 30
L. ERIE 31
L. ERIE 32
L. ERIE 36
L. ERIE 37
L. ERIE 38
L. ERIE 42
L. ERIE 43
L. ERIE 55
L. ERIE 55H8501
L. ERIE 55H8502
L. ERIE 57
L. ERIE 57H8501
L. ERIE 57H8502
L. ERIE 60
L. ERIE 60H8501
L. ERIE 60H8502
L. ERIE 63
L. ERIE 73
L. ERIE 73H8501
L. ERIE 73H8502
L. ERIE 78
L. ERIE 78H8501
L. ERIE 78H8502
L. ERIE 79H8501
L. ERIE 79H8502
Latitude
(north)
45 45 00.0
45 45 02.0
43 24 00.0
43 24 00.0
43 22 00.0
43 42 00.0
43 48 00.0
44 06 00.0
42 32 18.0
42 32 11.0
42 32 19.0
42 40 48.0
42 31 00.0
42 31 00.0
42 31 04.0
42 25 11.0
42 25 01.0
42 25 48.0
42 15 12.0
42 04 54.0
41 56 06.0
42 06 36.0
42 16 54.0
41 57 54.0
41 47 18.0
41 44 18.0
41 44 18.0
41 44 02.0
41 49 54.0
41 49 54.0
41 49 47.0
41 53 30.0
41 53 30.0
41 53 27.0
42 25 00.0
41 58 40.0
41 58 40.0
41 58 04.0
42 07 00.0
42 07 00.1
42 07 01.1
42 15 00.0
42 14 48.0
Longitude Approximate Depth
(west) (meters)
83 55 00.0
83 54 59.0
82 18 00.0
82 18 00.0
82 18 24.0
82 01 00.0
82 22 00.0
82 07 00.0
79 37 00.0
79 37 00.0
79 37 13.0
79 41 30.0
79 53 36.0
79 53 22.0
79 54 14.0
80 04 29.0
80 04 43.0
81 12 18.0
81 06 24.0
81 00 42.0
81 28 42.0
81 28 42.0
81 40 18.0
82 03 30.0
81 56 42.0
82 44 00.0
82 44 00.0
82 44 03.0
83 01 06.0
83 01 06.0
83 01 10.0
83 11 48.0
83 11 48.0
83 11 55.0
79 48 00.0
81 45 25.0
81 45 15.0
81 45 33.0
81 15 00.0
81 15 00.0
81 15 05.0
80 48 00.0
80 48 04.0
120
88
42
37
37
75
62
91
50
42
42
32
64
42
42
31
31
20
21
22
22
24
20
22
22
9
9
9
9
9
9
7
7
9
42
24
24
24
24
24
24
20
20
~i --w «• — »» ^_j. -^ »*^_«*ii£xj-»^_i. J-'j .IJA^JL J.\_w^/i^^;j. j.11 OCUiUCLL V _L ,/OZJ •
Stations designated H8502 were sampled by helicopter in February 1985,
-------
28
Table 3. Julian day and Greenwich time of sampling in Lakes Erie, Huron,
and Michigan as part of the 1985 helicopter survey related to
the 1985 surveillance program.3
Stations
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
ERIE
ERIE
ERIE
ERIE
ERIE
ERIE
ERIE
HURCN
HURCN
HURCN
HURCN
HURON
HURCN
HURCN
HURCN
HURCN
MICH
MICH
MICH
MICH
MICH
MICH
MICH
09H
15H
78H
73H
55H
60H
57H
90H
09H
15H
34H
37H
45H
54H
57H
61H
11H
18H
23H
27H
34H
41H
47H
Survey 8501
Julian
Day Time
013
013
013
013
014
014
015
015
015
015
015
015
016
- 16:
- 17:
- 20:
- 21:
- 14:
- 15:
- 14:
- 17:
- 18:
- 19:
- 21:
- 15:
- 15:
29
06
55
32
55
39
40
44
14
05
22
06
35
Survey 8502
Julian
Day Time
049
049
048
048
048
048
048
041
041
041
041
041
040
040
040
040
038
038
039
039
039
040
040
- 14:
- 14:
- 17:
- 17:
- 14:
- 14:
- 13:
- 18:
- 17:
1 "7 •
- 14:
- 13:
- 21:
- 20:
- 20:
- 19:
- 21:
- 21:
- 20:
- 21:
- 21:
- 15:
- 15:
54
26
48
12
52
19
51
02
38
02
28
55
10
36
05
42
10
54
32
10
52
00
44
aL. ERIE 18H L. ERIE 79H, L. MICH 06H and L. MICH 57H were also sampled
(see Lesht and Rockwell, 1987).
Discrete samples were collected for phytoplankton analysis at one,
five, ten, and twenty meters, and composited to represent the upper twenty
meters at each station. For the shallow western basin of Lake Erie, the
sample at one meter above the bottom replaced the ten meter depth, and the
twenty meter depth was not taken. For the central basin of Lake Erie, the
sample at one meter above the bottom replaced the twenty meter depth. The
composited sample represented four equal aliquots from available samples
within the upper 20 meter layer (or three samples if less than 20 meters
deep).
-------
29
Table 4. Julian day and Greenwich time of sampling in Lake Michigan during
the 1985 surveillance program.a
Station
Southern Basin
L. Michigan 11
L. Michigan 17
L. Michigan 18*
L. Michigan 19
L. Michigan 23
L. Michigan 27
Northern Basin
L. Michigan 32
L. Michigan 34
L. Michigan 40
L. Michigan 41*
L. Michigan 47
Spi
Leg 1
106
13:50
106
10:00
110
22:44
111
01:39
111
05:30
111
09:10
111
15:49
111
13:00
111
20:44
111
22:45
112
03:13
"inq
Leg 2
122
10:55
122
16:11
122
13:46
122
07:33
121
03:52
122
00:30
121
18:02
121
20:59
121
13:35
121
11:31
121
07:44
Leg 1
232
18:18
232
14:45
232
11:15
232
08:30
232
04:20
230
20:56
230
02:00
230
16:25
229
20:30
229
18:00
229
13:30
Summer
Leg 2
233
19:40
233
23:20
233
01:50
234
04:23
234
08:24
234
12:29
234
19:33
234
16:40
235
00:05
235
02:00
235
05:54
Leg 3
244
13:30
244
20:30
244
16:40
244
09:00
244
04:30
243
23:59
243
16:45
243
19:35
243
11:30
243
09:00
243
04:45
Fal]
Leg 1
318
16:00
318
11:45
318
20:00
318
23:27
319
04:05
319
08:30
319
16:00
319
13:00
319
21:25
319
23:30
320
04:20
L
Leg 2
338
07:00
338
19:00
338
10:15
338
01:30
338
02:19
337
22:40
337
19:22
334
21:23
334
10:52
334
13:40
| 333
02:30
aStations are ordered along the survey track and grouped into basins.
*Asterisks denote master stations.
One station within each lake basin was identified as a master station.
These stations were generally located at the deepest sounding within the
basin. Additional samples were taken at the master stations through the
first 50 meters at 5, 10, 20, 30, 40 and 50 meters to provide better
vertical resolution of the sampled parameters. The master stations are
identified by an asterisk in Tables 4 through 6.
-------
30
Table 5. Julian day and Greenwich time of sampling in Lake Huron during
the 1985 surveillance program.3
Spring
Station
Northern
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
Huron
Huron
Huron
Huron
Huron
Huron
Huron
Huron
Huron
Huron
Huron
Southern
L.
L.
L.
L.
L.
L.
L.
L.
L.
Huron
Huron
Huron
Huron
Huron
Huron
Huron
Huron
Huron
Basin
61
57
54
53
48
45*
43*
38
37
32
29
Basin
27
93*
15*
92
12
91
09
90
06
Leg 1
112
18:11
112
22:57
113
01:55
113
05:30
113
08:50
113
12:15
113
15:00
113
18:02
113
20:19
113
23:14
Leg 2
120
16:30
120
14:10
120
01:03
120
00:34
119
21:19
119
19:10
119
17:15
119
15:11
119
12:57
119
11:16
Leg
228
21:50
228
17:14
228
14:00
228
10:07
228
05:50
228
02:30
227
23:30
227
20:40
227
18:20
227
15:15
Summer
l Leg 2
235
20:30
235
23:50
236
03:45
236
20:30
237
00:20
237
02:50
237
05:00
237
07:30
237
10:05
237
12:10
Leg 3
242
05:15
242
00:45
241
21:45
241
14:00
241
15:10
241
12:20
241
09:00
241
06:10
241
03:00
241
01:15
Fall
Leg 1
322
01:00
322
11:00
322
14:15
322
17:20
322
20:26
323
00:04
323
03:30
323
07:10
323
09:30
323
12:40
Leg2
332
05:01
332
01:54
331
22:06
331
18:55
331
14:45
331
11:40
331
09:07
331
05:50
331
03:15
331
01:17
aStations are ordered along the cruise track and grouped into basins.
*Asterisks denote master stations.
-------
31
Table 6. Julian day and Greenwich time of sampling in Lake Erie during
the 1985 surveillance program.3
Sorina
Station
L.
L.
L.
Erie
Erie
Erie
Central
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
L.
Erie
Erie
Erie
Erie
Erie
Erie
Erie
Erie
Erie
Erie
stern
Erie
Erie
Erie
Erie
60
57*
55
Basin
42
43
73
36
37
38
78*
32
31
30
Basin
15*
10
09
63
Leg l
114
20:50
114
22:28
115
00:17
115
06:33
115
04:50
115
08:15
115
09:50
115
11:30
115
13:33
115
16:00
115
17:38
115
19:23
116
03:54
116
05:50
116
07:25
116
02:16
Leg 2
118
16:29
118
15:08
118
13:30
118
07:20
118
08:45
118
05:35
118
04:05
118
02:41
118
01:18
117
22:49
117
21:25
117
19:55
117
11:55
117
09:25
117
08:00
117
13:05
Leg 1
218
05:40
218
07:55
218
09:45
218
16:35
218
14:45
218
18:40
219
00:45
218
22:55
218
21:03
219
02:45
219
04:25
219
06:30
219
09:00
220
04:40
220
07:35
220
09:30
220
03:00
Summer
Leg 2
226
10:10
226
08:50
226
06:55
226
00:25
226
02:10
225
22:40
225
20:55
225
19:10
225
17:35
225
14:45
225
13:10
225
11:30
225
10:00
225
01:05
224
23:10
224
21:25
225
02:45
Fall
Leg 3
238
07:00
238
08:30
238
10:30
238
16:00
238
15:08
238
18:40
239
04:40
238
20:15
239
02:35
239
00:50
238
23:00
Leg 1
325
03:20
325
04:40
325
11:05
325
13:30
325
11:45
325
15:15
325
16:45
325
18:19
325
20:05
326
01:50
326
03:30
326
00:31
325
22:52
326
21:10
326
22:58
327
00:28
326
19:30
Leg 2
329
05:35
329
04:27
329
02:37
329
20:21
328
21:54
328
18:83
328
16:40
329
14:40
329
12:20
328
05:30
328
03:44
328
07:00
328
08:50
327
19:50
327
17:58
327
15:15
327
21:09
aStations are ordered along the cruise track and grouped into basins.
Asterisks denote master stations.
-------
32
Helicopter Survey
A continuing problem in lake surveillance has been the difficulty of
obtaining data during the winter. Ice conditions and bad weather
generally preclude ship borne sampling. This problem was overcome as
part of the 1983 survey by using a helicopter as a sampling platform.
The helicopter sampling survey was expanded as part of the 1984 program
to include two separate sampling periods, in January and February 1985,
as well as sampling from deeper depths than in February 1984. The
sampling locations for the helicopter surveys are shown in Table 2.
These sanpling locations differ from ship survey sites due to ice
conditions or safety requirements preventing flight to offshore sites. A
reduced parameter set (Table 1) was sampled by collecting water from two
depths at each helicopter station and returning the samples to a
land-based laboratory after each flight. The day and time of sampling
(Greenwich Time) are given in Table 3. These data were also reported in
Lesht and Rockwell (1987) for the 1984 station network and have been
modified to report results for the 1985 station network.
-------
33
METHODS
SHIP AND SAMPLING EQUIPMENT
The methods used in this surveillance program corresponded to
well-established accepted protocols for water quality sampling (USEPA,
1983). All sampling was conducted from the R/V Roger R. Simons, a former
Coast Guard vessel built in 1939 as a lighthouse tender. The ship is 122
ft long, has a beam of 27 ft, a draft of 7 ft at maximum displacement,
and displaces 342 tons.
Loran-C and radar ranges and bearings were used to navigate and to
establish the ship's position on station. As a precaution against
contamination of surface samples no overboard discharge of laundry,
shower, or galley waste was allowed 5 minutes before the ship reached a
sampling station until after sampling was completed.
A 12-attachment Rosette sampler system (General Oceanics Model
1015-12-8)a was used to collect the water samples. This system consists
of a steel frame with 11 sampling bottles and an electrobathythermograph
(EBT, Guildline Model 8705) mounted at one collector position. The
sampling array is controlled using 500 m of multi-conductor cable run
through the ship's A-frame to a 5-horsepower variable-speed winch. The
Rosette sampling array can accommodate any of the General Oceanics rigid
PVC 1010 Niskin sampling bottles up to the 8-L size. The sampling
bottles mounted on the Rosette were sequentially closed by remote
control from the deck of the ship while the sampling array was submerged.
Because sampling depths were determined in relation to the thermal
structure of the water column, the standard procedure was to use the EBT
on the Rosette to measure the temperature profile of the water column as
the sampling array was lowered to the bottom, and then collect the water
samples at the appropriate depths as the Rosette was returned to the
surface. The EBT was factory calibrated and checked before each survey
by immersion in an ice-water bath.
aMention by U.S. Environmental Protection Agency of commercial products
in this report does not connote recommendation of products to the
exclusion of other products that may be suitable.
-------
34
SAMPLING PROCEDURES
The protocol used for removing the water samples from the collection
bottles and distributing them to the various sample-storage bottles was
designed to minimize the possibility of contamination. Each Niskin
bottle was emptied into the sample bottles as soon as possible after
collection. This was normally done within 1 minute and never later than
10 minutes after the Rosette was brought back on deck. All the chemistry
sample bottles were rinsed once with the sample before filling. New
1-gallon polyethylene containers were used to hold the sample for the
onboard analysis and preparations.
To reduce possible contamination from atmospheric dust, the empty
bottles were capped during preparation for sampling. The caps were
replaced immediately after collection or after the addition of
preservative (when preservation was required). Sample transfers from one
bottle to another were avoided when possible. Smoking was not allowed in
the laboratory, preparation room, wet laboratory, microbiological
laboratory, or on the deck during sampling operations.
ANALYTICAL METHODS
A complete analytical wet laboratory was installed on the vessel and
was operated almost continuously during the sampling surveys. The
laboratory included eight Technicon Autoanalyzers (System II) configured
for analysis of ammonia, nitrate + nitrite, dissolved orthophosphorus,
dissolved reactive silicon, chloride, sulfate, total dissolved
phosphorus, and total phosphorus. The quality control plan for onboard
analysis required that all samples be analyzed for all unacidified and
unstable parameters within 2 to 48 hours of collection. If the
analytical time limit was violated (which occurred rarely) the sample
data were discarded.
To minimize sample-degradation problems, many of the water-equality
analyses were conducted onboard the ship immediately after collection of
the samples. Samples for those procedures that could not be conducted
onboard (e.g., those that required digestion) were preserved immediately
after collection. The analytical procedures that were used in this
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35
program are summarized below; an indepth coverage of the procedures has
been reported by Rockwell (1983).
0 Water Temperature—The temperatures recorded using the Electro-
bathythermograph were verified using a mercury thermometer
readable to 0.1°C. Water temperature was read within 1 minute of
sampling and recorded to the nearest 0.1°C.
0 Air Temperature—Air temperature was determined with a dial scale
bimetallic helix thermometer (Weston 4200) that was allowed to
stabilize in the shade in an open area on deck. Air temperature
was recorded to the nearest 0.5°C.
° Wind Speed and Direction—Wind speed and direction were measured
with a permanently mounted Danforth Marine Wind Direction and
Speed Indicator while the ship was stopped for sampling. Wind
direction was recorded to the nearest 10 degrees (to the right of
true north), and wind speed was measured and recorded to the
nearest nautical mile per hour.
0 Wave Height—Average wave height (to crest distance) was estimated
to the nearest 0.5 ft by the senior crew member on the bridge at
each sampling location. Wave heights were recorded to the
nearest 0.1 m.
0 Turbidity—Turbidity was measured with a Turner Turbidimeter
within 2 hours of sample collection. Before its use, the
turbidimeter was calibrated with a standard within the
anticipated range. The turbidity samples were heated to 25°C to
avoid condensation on the sample cuvette. Readings from 0-1 FTU
were recorded to the nearest 0.01 FTU, and readings from 1-40 FTU
were recorded to the nearest 0.1 FTU.
° Secchi Disc Depth—Secchi disc depths were recorded at all
stations sampled during the daytime by use of a 30-on, all-white
disc. Secchi disc depths were recorded to the nearest 0.5 m.
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36
EH—Analyses for pH were made by electrometric measurement,
typically within 15 minutes of sample collection. The pH meter
(Orion Model 701) was standardized with two buffers, one of pH 7.0
and the other of pH 9.0. The Orion pH meter was equipped with an
automatic temperature compensation probe and was used with a
combination glass membrane silver/silver chloride internal
electrode. The pH readings were recorded to the nearest 0.01 pH
unit.
Chloride—Chloride analyses were made with a Technicon
Autoanalyzer System II using Technicon's industrial method 99-70W
(O'Brien, 1962) adjusted to provide a working range of 0-30 mg/L.
This method is based on the displacement of mercury in mercuric
thiocyanate by chloride to produce un-ionized soluble mercuric
chloride. The thiocyanate, released by this displacement reacts
with ferric ion to produce ferric thiocyanate, which is then
measured photometrically. The raw water samples were stored and
refrigerated in the four-liter polyethylene sample containers and
were analyzed within 1 week of collection.
Sulfate—Samples were analyzed for sulfate with a Technicon
Autoanalyzer System II using Technicon's industrial method
118-71W (Lazrus et al. , 1965). The working range was 0-30 mg/L.
In this procedure, the sample is passed through a cation-exchange
column to remove interferring cations. The sample is then mixed
with an equimolar solution of barium chloride and methyl thymol
blue (MIB). The sulfate reacts with the barium, reducing the
amount of barium available for reaction with the MB. The free
MB is then measured photometrically. The raw water samples were
stored, refrigerated, in the four liter polyethylene container and
analyzed within 1 week of collection.
Specific Conductance—Specific conductance or conductivity was
determined within 2 hours of sample collection. Determinations
were made with a Bamstead model FM70CB conductivity bridge and a
conductivity cell (YSI 3401 or YSI 3403). An immersion heater
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37
connected to an electronic temperature controller was used to
heat the sample in a 250-mL polypropylene beaker to 25°C. The
temperature was monitored with a mercury thermometer with 0.1 °C
divisions. The sample was stirred during heating. The apparatus
was standardized daily using a 0.15-g/L KC solution (Lind et al.,
1959).
Total Alkalinity—Total alkalinity as CaC03 was determined within
2 hours of sample collection by titration of a 100-mL aliquot to
pH 4.5 with commercial 0.02 N sulfuric acid. The pH
controller/meter (Cole Farmer model 5997 with combination
electrode) was standardized daily with pH 4 and pH 7 buffers, each
prepared from Fisher Scientific concentrates.
Alkaline Earths and Alkali Metals—Analyses for calcium,
magnesium, and sodium were conducted by inductively coupled argon
plasma emission spectroscopy. The potassium determinations were
done by flame atomic absorption. All the samples were preserved
immediately upon collection by addition of 5 mL/L concentrated
nitric acid.
Dissolved Oxygen—Dissolved oxygen determinations were made using
the azide modification of the Winkler test (U.S. Environmental
Protection Agency, 1979) or with a YSI-5720 self-stirring BOD
bottle probe that was calibrated daily against the modified
Winkler test. The analysis of dissolved oxygen was performed
imnediately after sample collection when the YSI probe was used.
The dissolved oxygen sample aliquot was obtained by inserting an 8
to 10-inch length of flexible plastic tubing (e.g., Tygon) into
the Niskin bottle outlet plug and running directly to the bottom
of a 60 mL glass BOD bottle. Flow from the outlet plug was
regulated so as to minimize turbulence; two to three bottle
volumes were allowed to flow through the bottle before closure and
subsequent addition of reagents to fix the dissolved oxygen.
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38
Dissolved Nutrients—Samples for analysis of dissolved nutrients
were prepared by vacuum filtration of an aliquot from the
Polyethylene collection containers. The samples were filtered
within at most 2 hours of collection (in most cases within 30
minutes). A 47-mm diameter, 0.45-um membrane filter (HAWP 04700)
held in a polycarbonate filter holder (Millipore XX 11 04710) was
used with a polypropylene filter flask prewashed with 100 to
200-mL of either demineralized or sample water. New 125-mL
polyethylene sample bottles with linerless closures, rinsed once
with the filtered samples, were used to hold the filtrate for
subsequent analysis.
Dissolved Reactive (ortho) Phosphorus—Filtered samples were
analyzed for orthophosphate using a Technicon Autoanalyzer System
II and Technicon's industrial method 155-71W (Murphy and Riley,
1962). This is the single-reagent ascorbic acid reduction method
in which a phosphate-molybdenum blue complex is measured
photometrically at 880 nm. Analyses for dissolved orthophosphate
were conducted onboard within 2 to 24 hours of sample collection.
Total Phosphorus and Total Dissolved Phosphorus—Samples for
analysis of total phosphorus and total dissolved phosphorus were
transferred to acid washed screw cap digestion tubes as soon as
possible after collection. The digestion procedure that converts
the various forms of phosphorus to orthophosphate is an adaptation
of the acid persulfate digestion method (Gales et al., 1966).
After addition of the sample, and digestion solution, the
digestion tubes were heated in a forced air oven to 150°C for 30
minutes. The samples were then cooled and analyzed for
orthophosphate using the Technicon Autoanalyzer System II. The
orthophosphate method used for the digested total phosphorus and
total dissolved phosphorus analyses was similar to that described
above for analysis of dissolved orthophosphate, except that the
sulfuric acid concentration in the color reagent was reduced to
500 mL to compensate for the acid in the digestion
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39
tubes. These analyses were also conducted onboard within 24 to 48
hours of sampling.
Dissolved Reactive Silicon—The Technicon Autoanalyzer System II
was used with Technicon's industrial method 186-72W/Tentative to
analyze the filtered samples for reactive silicon. This method is
based on the reduction of a silicomolybdate in acid solution to
molybdenum blue by ascorbic acid. Oxalic acid is added to the
sample to eliminate interference from phosphorus. These analyses
were also conducted onboard within 2 to 24 hours of sampling.
Nitrate + Nitrite Nitrogen—Filtered samples were analyzed for
nitrate + nitrite nitrogen with the Technicon Autoanalyzer System
II and Technicon's industrial method 158-71W (Armstrong et al.,
1967). In this procedure, nitrate is reduced to nitrite in a
copper cadmium column, which is then reacted with sulfanilamide
and N-l-napthylethylenediamine dihydrochloride to form a reddish
purple azo dye. Analyses for nitrate + nitrite were performed
onboard within 2 to 24 hours of sample collection.
Ammonia Nitrogen—Unf i Itered samples were analyzed for ammonia
using a modification of Technicon's industrial method
154-71W/Tentative. The sample pump tube rate for this method is
0.80 mL/min, complexing agent tube 0.42 mL/min, alkaline phenol
tube 0.23 mL/min, hypochlorite 0.16 mLAun, nitroprusside 0.23
mL/min, and flow cell 1.00 mL/min. The ammonia determinations
were performed onboard as soon as possible after sample
collection, usually within 2 hours and no longer than 24 hours.
Total Kjeidahi Nitrogen—The water samples collected for analysis
of total Kjeldahl nitrogen were preserved by addition of 0.40 iriL
of sulfuric acid (300 mL/L) to each 125 mL. The preservative was
added within 30 minutes of sample collection. The analyses were
made using an "ultramicro semi-automated" method (Jirka et al.,
1976), in which a 10-mL sample is digested with a solution of
potassium sulfate and mercuric oxide in a thermostated 370°C block
-------
40
digester. After cooling and dilution with water the satrple is
neutralized and a determination for ammonia is made using the
Technicon Autoanalyzer System II. The analyses for total
Kjeldahl nitrogen were made within 180 days of sample collection
at the U.S. EPA Central Regional Laboratory.
0 Chlorophvll-a and Pheophytin—Samples used for chlorophyll-a and
pheophytin determinations were filtered at <7 psi vacuum along
with 1 to 2 mL of magnesium carbonate suspension (10 gL), usually
within 1 hour of sample collection. The filter (Gelman type AE)
was retained at -10 °C in a capped glass tube containing 10 mL of
90 percent spectrograde acetone. Before analysis, the tubes were
placed in an ultrasonic bath for at least 20 minutes and allowed
to steep for at least 24 hours while refrigerated at less than
4°C. The flucre-metric analyses were performed using an Aminco
dual monochromator spectrofluorometer (Strickland and Parsons,
1965).
1985 HELICOPTER SURVEYS
During January and February 1985, the three lakes were sampled using
a helicopter as the sampling platform. Water was collected with an 8-L
Niskin bottle from two depths at each helicopter station. Aliquots were
distributed among preiabeied bottles iirmediately after collection and
were filtered and preserved (when appropriate) upon landing after the
collection flight. The time between collection and filtration was less
than 3 hours (usually less than 2 hours).
After filtration and preservation, the samples were shipped in ice
via air freight to the USEPA's Region V Central Regional Laboratory in
Chicago. All analyses were completed within 48 hours of sample
collection. The raw results of these analyses are included in
Appendix B.
QUALITY ASSURANCE
The analyses conducted onboard the research vessel and those done at
EPA's Central Regional Laboratory were subject to quality control
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41
procedures that consisted of (1) analysis of stable check standards,
(2) analysis of reagent and sample blanks, (3) analysis of duplicate
unknowns, and (4) analysis of spiked samples. These procedures were
performed both to monitor the precision and accuracy associated with each
analytical method and to ensure that both the onboard and central
laboratories were in a state of statistical control at all times.
The quality control procedures were conducted as part of the regular
analysis. One depth at each regular (i.e., not master) station was
randomly designated as a quality control depth. The sample taken at this
depth was split both at collection and again in the laboratory. The
regular array of analyses were run on all four subsamples. At master
stations one sample was randomly chosen for a laboratory split; analyses
were run in duplicate on these samples.
Estimates of the analytical variance associated with each procedure
were used to establish control limits for the check standards, reagent
blanks, and duplicate ranges. If any determination or sequence of
determinations indicated a probability of less than one in one hundred
that the procedure is in control (i.e., violated the control limits for
the procedure), the processing of samples was stopped until the method
was brought back under control. Samples that were in the analysis stream
when the control limits were violated were reanalyzed.
The estimates of procedure variance obtained from the analysis of
the reagent blanks were also used to establish a criterion of detection
for each parameter. For this study, "criterion of detection" is defined
as the minimum concentration that must be obtained in an analysis for the
analyst to state, with some prespecified degree of confidence, that the
concentration of the material of interest in the sample is different from
zero. Criterion of detection is calculated here as the mean of the
reagent blanks plus two standard deviations. This corresponds to a
confidence interval of approximately 95 percent.
The results of the quality control analyses for several parameters
for each survey are shown in Tables 7 through 10. The values of both the
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Table 7. Surtmary of quality control analyses, winter helicopter surveys, 1985 surveillance program.
Parameter
Total phosphorus (ug/L)
Total dissolved
phosphorus (ug/L)
Dissolved reactive
phosphorus (ug/L)
Dissolved reactive
silicon (ug/L)
Total ammonia nitrogen
(ug/L)
Total nitrate + nitrite
nitrogen (ug/L)
Chloride (mg/L)
Sulfate (mg/L)
Alkalinity (mg/L)
Specific conductance
(us/on)
pH
Check3-
Standard 1
5.6 + 0.4 (5.6)
N= 14
5.9 + 0.4 (5.6)
N = 11
3.6 + 0.3 (4.2)
N= 15
113 + 25 (93)
N= 14
6.9 + 2.6 (4.4)
N= 15
71.4 + 12.3 (72)
N= 15
1.88 + 0.25 (2.0)
N= 15
2.87 + 0.51 (3.0)
N= 15
50.3 + 0.5 (50)
N= 13
198.3 + 2.1 (197)
N = 14
6.85 + 0.04 (6.86)
N = 14
Check?
Standard 2
30.0 + 1.2 (28)
N= 14
29.8 + 1.0 (28)
N = 11
18.6 + 1.1 (21)
N = 15
486 + 31 (473)
N= 14
46.9 + 3.8 (44)
N = 15
703 + 75 (720)
N= 15
7.99 + 0.19 (8.0)
N = 15
15.2 + 0.22 (15.0)
N= 15
100.4 + 0.7 (100)
N= 13
295.1 + 1.9 (293)
N- 14
9.26 + 0.03 (9.18)
N= 14
Field13,6
Blank
2.9 + 4.0 «1)
N = 14
5.2 + 5.2 (<1)
N = 11
1.2 + 1.3 (<1)
N= 15
13 + 47 «4)
N = 15
-0.15 + 2.3 «3)
N= 13
4 + 8 «7)
N = 15
0.41 + 0.61 «0.4)
N = 15
0.79 + 1.09 «0.2)
N= 14
2.5 + 3.2 «0.5)
N= 14
7.0 + 8.7 «2.23)
N = 14
4.60 + 0.95 «5)
N = 14
Duplicate0
Audit
0.39 + 0.45 «6)
N= 14
0.33 + 0.32 «6)
N= 11
0.57 + 0.69 «2)
N = 8
5 + 5 «30)
N= 9
1.9 + 1.5 «5)
N = 8
6.7 + 14.1 «20)
N = 9
0.14 + 0.13 «0.53)
N= 8
0.36 + 0.35 «0.7)
N= 8
0.29 + 0.25 «1.5)
N= 14
0.5 + 0.5 «3)
N= 14
0.04 + 0.03 «0.16)
N = 14
Laboratory^
Blank
0.13 + 0.30
N= 14
0.03 + 0.12
N= 11
0.13 + 0.28
N= 15
12.3 + 24.5
N= 15
0.46 + 1.63
N= 15
0.13 ± 0.50
N = 15
0.05 + 0.12
N= 15
0.25 + 0.20
N= 15
0.39 + 0.34
N= 14
1.98 + 1.40
N= 13
4.08 + 0.56
N = 13
aCheck standards are stable solutions of known concentrations, target values in parentheses.
^-Acceptable level of reagent blanks in parentheses.
cAverage difference between duplicates - laboratory split.
^Acceptable level of reagent blanks in parentheses as in field blanks.
eQaitaminated reagent water taken on survey.
ro
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Table 8. Suimary of quality ocntrol analyses, spring surveys, 1985 surveillance
Parameter
Total phosphorus (ug/L)
Total dissolved
phosphorus (ug/L)
Dissolved reactive
phosphorus (ug/L)
Dissolved reactive
silicon (ug/L)
Tbtal antmia nitrogen
(ug/L)
Total nitrate + nitrite
nitrogen (ug/L)
Chloride (irg/L)
Sulfate (mg/L)
Turbidity (ITU)
Mtelinity (ug/L)
Specific ccndLctaTce
(us/on)
FH
Dissolved oxygen (mg/L)
Check3
Standard 1
4.6 + 0.4 (5.6)
N= 74
4.6 + 0.4 (5.6)
N= 74
3.8 + 0.5 (4.2)
N= 74
89 + 5 (93)
N= 74
7 + 2 (4.4)
N= 72
66 + 8 (70)
N= 74
5.5 + 0.2 (5.6)
N= 74
2.5 + 0.2 (2.4)
N= 74
0.35 + 0.03 (0.4)
N= 29
79.7 + 0.9 (80)
N= 30
196.6 + 0.6 (196.5)
N= 28
6.84 + 0.05 (6.86)
N= 29
Check? Field0
Standard 2 Blank
25.5 + 0.9 (28) -0.
N = 74
25.0 + 0.8 (28) 0.
N = 74
19.4 + 0.7 (21) 0.
N= 74
468 + 13 (467) 1.
N = 74
45+3 (44) 1.
N= 72
705 + 51 (720) 0.
N= 74
17.5 + 0.3(17.3) 0.
N= 74
19.9 + 0.5(20.5) 0.
N= 74
7.87 + 1.1 (10) 0.
N= 29
99.0 + 1.2 (100) 0.
N= 30
292.5 + 1.1 (293) 1.
N= 28
9.27 + 0.07 (9.18)
N= 29
16 + 0.33 «1)
N= 73
06 + 0.52 «1)
N = 73
34 + 0.31 «1)
N= 73
3 + 8.6 «4)
N= 72
8 + 1.6 «3)
N = 73
7 + 2.8 «7)
N= 71
19 + 0.11 «0.4)
N= 71
02 + 0.06 (<0.2)
N= 73
05 + 0.05(<0.22)
N= 64
41 + 0.32 «0.5)
N= 64
40 + 0.43«2.23)
N = 64
«5)
Duplicate0 Laboratory'3
ftudit Blank
0.9 + 1.5 «6) -0.
N= 74
0.4 + 0.4 «6) -0.
N= 74
0.3 + 0.3 «2) -0.
N= 74
3 + 3 «30) 0.
N= 73
1 + 2 «5) 0.
N= 72
5 + 5 «20) 0.
N = 73
0.07 + 0.08 0.
N = 73 «0.53)
0.2 + 0.2 «0.7) 0.
N= 74
0.11 + 0.20 «0.4)
N= 71
0.6 + 0.9 «1.5)
N= 73
0.5 + 0.8 «3)
N= 73
0.06 + 0.06 «0.16)
N= 65
(£0.28)
04 + 0.38
N= 73
05 + 0.60
N= 73
03 + 0.18
N= 74
15 + 1.83
N= 74
9 + 0.6
N= 72
58 + 2.5
N= 74
19 + 0.11
N= 74
01 + 0.06
N= 74
Nb data
Nb data
No data
No data
Kb data
aCheck standards are stable solutions of know concentrations, target values in parentheses.
btoceptable level of reagent blanks in parentheses.
Average difference between duplicates - laboratory split.
level of reagent blanks in parentheses as in field blanks.
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Table 9. SLmrary of quality control analyses, sumner surveys, 1985 surveillance program.
Farameter
Ibtal ptiosEfiorus (ug/L)
Ibtal dissolved.
phosphorus (ug/L)
Dissolved reactive
phosphorus (ug/L)
Dissolved reactive
silicon (ug/L)
Ibtal anmcnia nitrogen
(ug/L)
Total nitrate + nitrite
nitrogen (ug/L)
Cnloride (mg/L)
Sulfate (mg/L)
Turbidity (FIU)
Alkalinity (mg/L)
spacific conductance
(us/cm)
EH
Dissolved oxygen (mg/L)
Creek3
Standard 1
5.3 + 2.1 (5.6)
N= 118
4.9 + 1.4 (5.6)
N= 118
4.7 + 0.7 (4.2)
N = 116
94 + 3 (93)
N= 116
8 + 3 (4.4)
N = 118
65+6 (70)
N = 116
5.4 + 0.2 (5.6)
N = 118
2.4 + 0.2 (2.4)
N = 118
0.31 + 0.08 (0.4)
N= 33
78.9 + 0.8 (80)
N= 38
197.2 + 0.8(1%. 5)
N = 40
6.88 + 0.03(6.86)
N= 41
Oieck3
Standard 2
27.5 + 2.7 (28)
N= 118
27.7 + 3.3 (28)
N = 118
23.8 + 2.0 (21)
N = 116
471 + 8 (467)
N= 116
46+5 (44)
N= 118
729 + 25 (720)
N = 116
17.4 + 0.3 (17.3)
N = 118
20.4 + 0.5 (20.5)
N = 118
8.24 + 1.67 (10)
N = 36
98.6 + 0.9 (100)
N= 38
292.9 + 0.7 (293)
N= 40
9.21 + 0.04 (9.18)
N= 41
Field13
Blank
-0.04 + 0.87 «1.2)
N= 92
0.24 + 1.67 «1.6)
N = 93
0.44 + 0.70 «1)
N = 93
5 + 19 «4)
N= 93
0.6 + 1.3 «3)
N= 93
0.3 + 1.1 (<7)
N = 93
0.23 + 0.19 «0.4)
N = 93
0.06 + 0.20 «0.2)
N = 93
0.07 + 0.02 «0.22)
N= 90
0.60 + 0.40 «0.5)
N = 87
1.14 + 0.37 (<2.23)
N= 91
5.54 + 0.25 (<5.0)
N= 91
Duplicate0
Audit
2.0 + 4.1 (<6)
N = 114
1.3 + 2.2 (<6)
N= 116
1.0 + 1.9 «2)
N= 115
24 + 94 «30)
N = 116
2 + 9 «5)
N = 118
6 + 27 «20)
N= 116
0.1 ± 0.1«0.53)
N = 118
0.2 + 0.4 «0.7)
N = 118
0.07 + 0.13 «0.4)
N = 108
0.3 + 0.4 «1.5)
N = 109
0.4 + 0.9 (<3)
N= 109
0.02 + 0.02 «0.16)
N= 109
0.4 + 0.5 (<0.28)
N= 100
Laboratory'1
Blank
0.11 + 0.87
N= 118
0.31 + 1.20
N= 118
0.43 + 0.97
N = 117
0.5 + 1.8
N= 118
0.8 + 1.2
N= 118
0 + 0.88
N = 118
0.22 + 0.16
N= 118
0.06 + 0.19
N= 118
Nb data
Kb rfcrt-a
No data
No data
ND data
aCheck standards are stable solutions of knowi concentration.
Eftoceptable level of reagent blanks in parentheses.
Average difference between duplicates - laboratory gplit.
^Acceptable level of reagent blanks in parentheses as in field blanks.
-------
Table 10. Sunrary of quality control analyses, fall surveys, 1985 surveillance program.
ISraroeter
Total phosphorus (ug/L)
•total dissolved
phosphorus (ug/L)
Dissolved reactive
phosphorus (ug/L)
Dissolved reactive
silicxn (ug/L)
Ibtal cunciiia nitrogsn
(ug/L)
Total nitrate + nitrite
nitrogen (ug/L)
QUoride (mg/L)
.Silfate tog/L)
Turbidity (BTU)
Alkalinity (itg/L)
Specific ocndjctarce
(uS/on)
EH
Dissolved oxjgen (mg/L)
Check3
Standard 1
5.8 + 0.8 (5.6)
N= 75
5.4 + 1.1 (5.6)
N= 75
3.8 + 0.8 (4.2)
N= 76
99 + 9 (93)
N= 76
6 + 2 (4.4)
N= 76
68+4 (70)
N= 76
5.4 + 0.2 (5.6)
N= 76
2.2 + 0.2 (2.4)
N= 76
0.40 + 0.07 (0.4)
N= 26
79.1 + 0.7 (80)
N= 27
197.2 + 0.6 (196.5)
N= 25
6.87 + 0.06 (6.86)
N= 27
Check3
Standard 2
27.3 +1.4 (28)
N= 75
26.9 + 2.0 (28)
N= 75
19.8 + 2.2 (21)
N= 76
470 + 17 (467)
N= 76
42 + 2 (44)
N= 74
713 + 21 (720)
N= 76
17.5 + 0.4 (17.3)
N= 76
19.6 + 1.0 (20.5)
N= 76
9.96 + 0.14 (10)
N= 26
98.7 +1.1 (100)
N= 27
293.3 + 0.7
N= 26 (293)
9.21 + 0.04 (9.18)
N= 27
Field0
Blank
0.1 + 0.4 (<1 )
N= 60
0.2 + 0.5 «1)
N= 60
-0.1 + 0.6 «1)
N= 60
45 + 86 «4)
N= 60
0.3 + 0.8 «3)
N= 60
0.1 + 0.6 «7)
N= 60
0.15 + 0.15 (<0.4)
N= 60
0.06 + 0.13 «0.2)
N= 60
0.05 + 0.03 «0.22)
N= 58
0.05 + 0.47 «0.5)
N= 59
1.34 + 0.28 «2.23)
N= 58
5.3 + 0.37 (<5)
N= 57
Duplicate0 Laboratory^
?udit Blank
7 + 0.9«6) 0.1 + 0.4
N = 76 N = 75
0.4 + 0.5 «6) 0.1 + 0.4
N = 76 N = 75
0.4 + 0.5 (<2) 0.0 + 0.4
N = 76 N = 76
6 + 6 «30) 0 + 2
N = 76 N = 76
2 + 11 «5) 0 + 0.4
N = 11 N = 75
10 + 19 «20) 0 + 0
N = 76 N = 76
0.1 + 0.1«0.53) 0.1 + 0.2
N = 76 N = 76
0.3 + 0.3 «0.7) 0.0 + 0.1
N = 76 N = 76
0.16 + 0.52 «0.4) ND data
N= 75
0.3 + 0.4 «1.5) Ifcdata
N= 75
0.6 + 1.0 «3) Ifcdata
N= 75
0.01 + 001 «0.16) Nb data
N= 74
0.7 + 0.5 «0.28) Nbdata
N= 74
^Check standards are stable solutions of knovn concentration.
tpcceptable level of reagent blanks in parentheses.
Average difference between explicates - laboratory spilt.
"-Acceptable level of reagent blanks in parentheses as in field blank.
-------
46
check standards and the procedure variances changed from survey to
survey, and as a result, the criteria of detection also varied. The
calculated criteria of detection are listed in Table 11. The data were
entered into the U.S. EPA STORE! Water Quality Database, with values
below the criterion of detection recorded as real values flagged witn the
code letter "T" as suggested by Clark (1980). All data in this report
are reported as quantitated by analytical instrumentation. Values
reported below the criteria of detection have not been flagged in this
report. Concentrations below the criteria of detection (Table 11) may
not be accurate or precise.
Table 11. Criteria of detection established by analysis of reagent blanks
- 1985 surveillance program.a
Parameter Winter
Total phosphorus (ug/L)
Total dissolved phosphorus (ug/L)
Dissolved reactive phosphorus (ug/L)
Dissolved reactive silicon (ug/L)
Total airmonia (ug/L)
Total nitrate + nitrite
nitrogen (ug/L)
Chloride (mg/L)
Sulfate (mg/L)
Turbidity (FTU)
Alkalinity (mg/L)
Specific conductance (uS/cm)
2.3
2.0
1.3
11
13
12
0.3
0.6
0.14
0.9
1.9
Sprina
0.8
1.0
l.O
21
5
7
0.4
0.1
0.17
1.1
2.3
Summer
1.5
3.6
1.8
10
3
3
0.6
0.5
0.11
1.3
1.9
Fall
1.0
1.1
1.3
22013
2
1
0.5
0.3
0.10
1.4
1.9
aAll data in this report are reported as quantitated by analytical
instrumentation. Values reported below the criteria of detection have
not been flagged in this report. The reader is cautioned that
concentrations below the criteria of detection listed above may not be
accurate or precise.
deionized water cartridge on the ship failed. Laboratory blanks
using distilled water were found to have a criteria of detection level of
14 ug/L.
-------
47
RESULTS
SCOPE
The analysis of the data collected during the 1985 surveillance
program follows closely the analysis done on the 1983 and 1984
surveillance data (Lesht and Rockwell, 1985 and 1987). The data
collected during 1983 through 1985 were intended to answer fairly
specific and limited questions concerning the water quality of Lakes Erie,
Huron, and Michigan. Because the design of the surveillance program was
based on the assumption of horizontal uniformity of constituent
concentrations within major lake basins, issues related to the spatial
distribution of the measured parameters within a basin were not addressed.
Similarly, the three surveillance surveys were not timed so as to provide
the data required to resolve the temporal structure of the annual nutrient
cycles within these lakes. Thus, the results presented here often are not
(and were not intended to be) as encompassing as those presented in the
several reports that have been published about the GLISP surveys (Rockwell
et al., 1980; Herdendorf, 1984; Mall et al., 1985).
From the inception of this survey program, the investigators
anticipated that most of the results would be reported as basin averages.
This accounts for the emphasis placed on sampling of water masses expected
to be relatively homogeneous. Such sampling helps ensure that the sample
variance associated with the calculated averages is dominated by random
sampling error rather than by the more systematic error that results from
spatial effects inherent in sampling an unknown (necessarily) spatial
distribution in a Great Lake. This dominance of random sampling error is
required for the application of many of the statistical tests often
applied to limnological data.
Although the sampling program was designed to reduce statistical
artifacts due to horizontal variations, the investigators recognized that
temporal and vertical variations might also bias statistical calculations
based on simple, unsubsetted populations. Experience with the 1983 and
1984 surveillance data suggested that temporal variation within surveys
would be small and that horizontal variation between adjacent lake basins
would be most evident in Lake Erie. However, the actual periods of
-------
48
sampling conducted in spring 1984 were found to be sufficiently different
to warrant separation of the two runs of the spring survey. Therefore,
the first step taken in the analysis of the 1985 data was to search for
the occurrence of natural subsets that could be used to classify the
samples. The initial subsets chosen were based on locations (lake basin),
time (survey and leg), and position within the water column relative to
the thermal structure.
TEMPORAL VARIMTCN WITHIN SURVEYS
The Student's t-test was used to evaluate the difference in basin
means calculated for adjacent legs within each survey. The lake basins
were defined in a manner similar to 1983 and 1984 and the two-tailed
t-test was conducted under the assumption that the variances associated
with the sample populations were unknown and not necessarily equal. The
stations associated with each basin are found in Tables 4-6. In some
basins, the sampling of adjacent legs was completed within 24 hours, a
period that must be considered synoptic by limnological standards. In
other cases, however, adjacent legs were sampled two weeks apart. Because
we anticipated pooling all the data for each survey for analysis, the
t-tests were used to evaluate the magnitude of any error or bias that
might result.
The question of pooling data separated in time and space is more
complicated than is usually appreciated. It is impossible to do truly
synoptic water sampling on the Great Lakes (remote sensing excepted);
therefore, samples separated in space are also separated in time.
Furthermore, samples taken at the same location over time (i.e.,
Eulerian) may be considered as spatially separated, since the water itself
will have moved between samplings. The proper approach is, therefore, to
design the sampling scheme in such a manner that it provides data that can
be used to answer the questions being posed by the monitoring program. In
this case, we are interested in parameter estimates representative of the
major lake basins during particular periods of the year. Because these
values are dependent on both space and time, the best that can be done is
to calculate sample averages.
-------
49
The results given in Tables 12 through 14 show that except for the
two legs of the fall survey in Lake Michigan and Lake Huron, the
differences between adjacent survey legs are insignificant (alpha = 0.05)
and that the data may be pooled by survey. The two legs of the fall
survey in Lake Michigan and Lake Huron, however, had too many significant
differences, related to the occurrence of the fall overturn between the
surveys, to justify pooling the data for many analyses. Thus, in the
remainder of this report many of the analyses are presented with these
data as subsets in which these legs are referred to as surveys Fall-1 and
Fall-2.
SPATIAL SEGMENTATION
We also used the Student's t-test to examine the differences between
parameter means calculated for subsets of the surveillance data based on
station location within the major lake basins. As before, the t-test was
conducted under the assumption that the variances associated with the
sample populations were unknown and not necessarily equal. The purpose of
this analysis was to determine the degree to which the open lake regions
differed from one another and whether these differences were consistent
throughout the year. Since we restricted the comparisons to data
collected within the epilimnion and compared the basin subsets on a
survey-by-survey (season-by-season) basis, the fundamental criterion
required for strict application of the t-test (i.e., that the data be
random samples from independent, normally distributed populations) was
satisfied. This would not have been the case if the comparisons had
been based on data known to be distributed non-normally (e.g. , data from
all surveys combined). Since we were interested in spatial gradations
within the data, the comparisons were done in a pairwise manner using
adjacent basins only. The results of these analysis for several water
quality parameters are shown in Tables 15-18.
In 1983 only Lake Erie showed consistent differences between basins;
in 1984 all three lakes had several parameters that were significantly
different between basins. In Lake Michigan, for example, during 1983 only
temperature and conductivity were consistently different between basins.
In 1984 the northern and southern basins of Lake Michigan were
-------
Table 12. Ccnparison of survey legs - lake Michigan southern basin epiliitnion.a
b
Spring _ Sattmer _ _ Fall _
Parameter Leg i Leg 2 Leg 1 Leg 2 Leg3 Leg 1 Leg 2
X 2.3 2.8 20.8 20.6 20.6 8.3 5.4
Teiiparature t -8.29 0.90 -0.03 12.35
(°C) result < = = >
X 0.31 0.49 0.40 0.44 0.60 0.25 0.45
Turbidity t -6.32 -0.63 -3.15 -4.76
(FTU) result < = < <
x 280.4 279.5 277.7 278.4 277.0 282.0 279.6
Oanductance t 5.10 -0.89 2.27 7.89
(uS/on) result > > >
X 4.6 5.3 2.7 2.6 2.2 4.0 5.5
Total piTOSphorus t -3.10 0.05 1.29 -5.34
(US3/L) result < = <
Total dissolved x 2.3 2.4 1.6 1.7 1.0 2.4 2.8
phosptorus t -0.69 -0.24 2.65 -1.63
(ug/L) result = >
Dissolved X 569 564 101 88 103 389 610
reactive t 1.03 2.21 -2.64 -12.60
silicon result = > < <
(ug/L)
Nitrate + nitrite x 299 286 167 160 149 249 290
nitrogen t 0.80 1.20 1.94 - 7.80
(ug/L) result = = <
X 0.33 1.57 0.94 1.18 1.24 0.56 0.32
Chlorpphvll-a t -13.0 -3.68 -0.94 5.68
(ug/L) result < > >
aCanparisons are based on twD-tailed t-test with alpha = 0.05. x is the sample average, t is the Student's
t value, synfcols < > denote statistically significant differences, syntol = denotes no statistical difference.
ing epilimnicn denotes entire water colom.
-------
Table 13. Corparison of survey legs — lake Huron northern basin epilimnicn.a
I&rameter
Temperature
(°C)
Turbidity
(FEU)
Specific
conductance
(uS/on)
Total phosphorus
(ug/L)
Total dissolved
phosphorus
(ug/L)
Dissolved
reactive
siliccn
(ug/L)
Nitrate + nitrite
nitrogen
(ug/L)
Chtorophyll-a
(ug/L)
b
Sprincr Suimer Fall
Leg 1 Leg 2 Leg 1 Leg 2 Leg 3 Leg 1 Leg 2
x 1.4 1.5 17.7 17.6 17.7 7.9 6.2
t -1.43 0.53 0.47 12.49
result < = >
x 0.34 0.89 0.22 0.20 0.20 0.21 0.43
t -1.24 0.76 -0.25 -6.26
result = = <
x 202.9 202.3 200.3 196.8 199.4 205.0 201.9
t 2.14 1.24 -0.94 3.62
result > = >
x 3.4 5.6 4.7° 2.2 1.6 2.9 3.8
t -0.88 0.66 2.00 -3.07
result = = <
x 1.3 1.2 3.16- 1.1 0.8 1.1 0.9
t 0.85 0.44 1.18 1.01
result = = =
x 782 760 491 355 414 632 747
t 5.19 4.64 -1.80 -6.13
result > > <
x 323 274 286 240 271 308 301
t 15.4 5.72 -3.95 1.77
result > > < >
x 0.30 1.42 1.06 1.02 0.92 0.58 0.30
t -21.3 0.15 0.88 5.87
result < = >
aGarparisons are based on two-tailed t-test with alphaO.05. x is the sanple average, t is Student's t value,
symbols < > denote statistically significant differences, synbol = denotes no statistical difference.
*}$Ting epilimnion denotes entire water colum.
clncludes two values (17.7 and 18.2), which are an order of magnitude greater than remaining values. Without
these values x=2.1.
dlncludes two values (15.3 and 16.9), which are an order of magnitude greater than remaining values. Without
these values x=1.3.
-------
Table 14. Coriparison of survey legs — lake Erie central basin epiliimicn.a
larameter
Taiperature
(°C)
Turbidity
(FIU)
Specific
ocnductance
(•uS/cm.)
Tbtal phosphorus
(ug/L)
Tbtal dissolved
phosphorus t
(ug/L)
Dissolved
reactive
silicon
(ug/L)
Nitrate + nitrite
nitrogen
(ug/L)
Chlorophyll-a
(ug/L)
b
Sprincr Suraier Fall
Leg 1 Leg 2 Leg l Leg 2 Leg 3 Leg 1 Leg 2
x 5.0 5.1 22.0 22.4 22.2 10.9 10.3
t -0.52 -9.15 4.82 8.71
result = < > >
X 1.73 1.80 0.44 0.40 0.41 2.48 2.26
t -0.34 1.77 -0.50 1.65
result = > = =
x 276.2 276.7 276.2 275.9 273.8 278.6 278.4
t -0.77 0.45 3.21 0.15
result = = > =
x 12.4 13.1 8.0 8.6 10.0 21.5 21.2
t -1.10 -0.70 -1.32 0.30
result = =
x 4.0 3.6 3.1 3.4 5.0 9.9 9.8
1.88 -0.63 -2.44 0.15
result = = < =
x 8.7 10.4 108 143 177 76.6 81.2
t -1.11 -2.26 -1.66 -0.55
result = < =
x 207 203 193 201 180 120 137
t 0.67 -1.22 2.92 -3.35
result = > <
x 1.60 3.64 3.10 3.07 3.34 2.84 2.39
t -10.7 0.08 -0.98 2.31
result < = >
aGaiparisons are based on two-tailed t-test with alpha =0.05. x is the sanple average, t is Students's
value, symbols < > denote statistically significant differences, symbol = denotes no statistical
difference.
^Spring epiliitnion means entire water column.
-------
Table 15. Corparisan of Lake Michigan northern and southern basin epiliimia.a
Winter 213 Spring13 Slimier Fall 1 Fall 2
Rarameter North. South North South North South North South North South
Temperature (°C) x 1.5 2.0 3 2.5 2.6 18.5 20.7 8.1 8.3 6.5 5.4
t -0.74 -0.53 -9.79 -0.51 8.13
result = < = >
Turbidity (FIU) X 0.34 0.40 0.36 0.48 0.23 0.25 0.26 0.45 0.26 0.45
t NO Data -1.52 -3.18 -0.65 -5.11
result < = <
Specific cmictance X 283.5 281.6 279.8 279.9 276.6 277.7 281.1 282.0 278.7 279.6
(US/on) t 1.56 -0.96 -3.05 -2.79 -1.91
result < <
Total phosphorus X 5.6 5.8 5.2 4.9 4.5 2.5 3.2 4.0 4.3 5.5
(ug/L) t -0.31 0.95 3.10 -2.67 -5.05
result > < <
Total dissolved x 4.1 4.7 2.8 2.4 1.2 1.4 2.1 2.4 3.0
phosphorus (ug/L) t -2.12 2.70 -1.31 -1.00 1.46 °°
result >
Dissolved reactive X 545 574 563 566 93 97 338 389 410 610
reactive silicon t -1.65 -0.47 -0.95 3.36 -8.15
(ug/L) result <
Nitrate + nitrite X 290 293 286 293 156 159 232 249 246 290
nitrogen (ug/L) t -0.23 -0.79 -0.92 -2.94 -4.85
result < <
Oilorcphyll-a (ug/L) x 0.89 0.79 0.75 0.95 1.00 1.12 0.78 0.56 0.32 0.32
t 0.57 -1.32 -2.10 3.14 0.04
result < >
aParameter values are means of sanples taken within the epiliirnia. Carpariscns are based en two-tailed t-test
with alpha= 0.05.
^^pilirtnia in the winter and spring surveys denote the entire water column.
-------
lable 16. Caiparison of Lake Hiran northern and southern basin epilimnia.a
Winter lb Winter 2° faring0 Sunnier Fall 1 Eall 2
Parameter North. South North South North South North South North South North South
Temperature x 1.8 2.0 0.8 0.2 1.5 1.8 17.7 19.7 7.9 8.3 6.2 6.9
(°O t - 0.75 2.27 -4.33 -14.10 -4.54 -5.36
result = > < < < <
Turbidity x 0.39 0.53 0.21 0.25 0.21 0.31 0.43 0.42
(FIU) t NO Data No Data -2.68 -1.99 -5.52 0.39
result < < <
Specific X 206.5 206.0 202.6 205.2 202.7 203.4 198.9 206.5 205.0 207.0 201.9 204.4
conductance t 0.62 -2.44 -3.05 -4.54 -3.46 -5.29
(uS/cm) result = < < < < <
Total phosphorus x 3.0 4.8 3.7 5.0 3.3 3.6 2.8 2.3 2.9 3.0 3.8 3.7
(ug/L) t -3.06 -0.70 -0.76 0.80 -0.64 0.43
result < = = = = =
Total dissolved x 2.1 3.0 2.3 2.0 1.3 1.3 1.9 1.3 1.1 0.8 0.9 2.1
phosphorus t -1.47 1.66 -0.31 1.03 2.68 -4.79
(ug/L) result = = > <
Dissolved x 769 713 801 799 773 782 422 338 632 716 747 741
reactive t 16.3 0.31 -2.91 4.23 -4.22 0.33
silicon result > = < > <
(ug/L)
Nitrate + nitrite x 335 331 304 329 302 301 267 276 308 328 301 297
nitrogen t 1.56 -1.77 0.24 -1.75 -2.02 0.73
(ug/L) result = = =
Chlorophyll-a x 0.89 0.85 0.80 1.30 0.78 1.09 1.00 1.36 0.58 0.60 0.30 0.40
(ug/L) t 0.50 -3.75 -2.79 -2.71 -0.32 -2.46
result = < < < = <
aParameter values are means of samples taken within the epilimnia. Comparisons are based on two-tailed t-test with
alpha=0.05.
ilinnia in the winter and spring surveys denotes the entire water column.
-------
Table 17. Gcnparison of lake Erie western and cental basin epiliimia.a
Winter lb Winter & Spring Sumner Ball 1
Parameter West Central West Central West Central West Central West Central
Terrperature (°C) x 0.0 2.0 0.0 0.0 12.0 5.1 22.5 22.2 7.0 10.6
t 21.46 1.75 -14.39
result < = > = >
Turbidity (FIU) x No Data No Data 6.39 1.77 4.17 0.42 12.02 2.37
t 11.61 13.36 5.82
result > > >
Specific conductance X 260.2 290.8 263.8 283.8 256.1 276.5 234.0 275.4 244.6 278.5
(US/on) t -5.02 -18.62 -6.25
result < < < <
Total phosphorus x 16.8 42.9 8.2 9.5 20.7 12.8 17.9 8.8 32.6 21.4
(ug/L) t 7.32 4.39 4.06
result < > > >
Total dissolved x 4.0 7.5 No Data No Data 3.9 3.8 4.2 3.7 6.9 9.9
phosphorus (ug/L) t 0.29 1.08 -2.98
result < <
Dissolved reactive x 710 75 638 36 633 10 329 140 743 79
silicon (ug/L) t 13.98 5.10 11.67
result > > > >
Nitrate + nitrite X 511 217 457 221 699 204 181 192 433 128
nitrogen (ug/L) t 11.27 -0.44 10.91
result > > > = >
OLLorqphyll-a (ug/L) x 3.49 4.57 2.14 2.47 5.85 2.75 10.84 3.16 1.72 2.62
t 3.39 5.34 -3.61
result = > > <
aParaneter values are means of satrples taken within the epiliimia. Conrparisons are based on two-tailed t-test with alpha=
0.05.
ilimnia in the winter and spring surveys denotes the entire water colum.
-------
liable 18. Coiparison of Lake Erie central and eastern basin epilimnia.a
b b b
Winter 1 Winter 2 Spring Suttmer Fall 1
Parameter Central East Central East Central East Central East Central East
Taiperature (°C) x 2.0 3.5 0.0 0.0 5.1 2.1 22.2 21.8 10.6 10.4
t 19.54 4.96 2.51
result > > >
Turbidity (F1U) x No Data No Data 1.77 2.63 0.42 0.48 2.37 4.10
t -5.56 -0.62 -2.57
result < = <
Specific OCnilCtarice X 290.8 290 283.8 289 276.5 278.2 275.4 280.2 278.5 283.5
(US/on) t -3.75 -12.19 -9.14
result < < <
Total phosphorus x 42.9 16.4 9.5 11.6 12.8 12.8 8.8 5.7 21.4 15.3
(ug/L) t -0.19 6.28 +4.55
result > >
on
Total dissolved x 7.5 8.4 No Data No Data 3.8 6.2 3.7 2.3 9.9 6.6 ^
phosphorus (ug/L) t -18.20 4.15 11.26
result < > >
Dissolved reactive x 75 62 36 68 10 72 140 75 79 90
silicon (ug/L) t -32.69 6.60 -1.49
result < > <
Nitrate + nitrite x 217 263 221 274 204 287 192 185 128 205
nitrogen (ug/L) t -19.75 1.09 -16.89
result < = <
Chlorqphyll-a (ug/L) X 4.57 1.92 2.47 1.06 2.75 0.49 3.16 1.39 2.62 0.82
t 13.80 11.88 15.34
result > > >
aBarameter valuesd are means of samples takm within the epiliirnia. Coiparisons are based on tw>-tailed t-test
with alphaF 0.05.
^Epilimnia in the winter and spring surveys denotes the entire water column.
-------
57
significantly different in nitrate + nitrite nitrogen (all surveys),
dissolved reactive silicon, chlorophyll-a, and turbidity (spring-2 and
sunnier surveys). Both dissolved reactive silicon and nitrate + nitrite
nitrogen were significantly different in the northern and southern basins
of Lake Huron during all of the 1984 surveys. Lake Erie continued to
exhibit the most pronounced differences between basins although the
contrast between the western and central basins in 1984 was less than in
1983.
In 1985, fewer consistently statistically significant differences
(alpha = 0.05) were observed in Lakes Michigan and Huron than in 1984.
Lake Erie exhibited many significant differences between the western and
central basins in all surveys for the eight parameters tracked (Table 17).
Similarly the central and eastern basins were different with the exception
of the spring survey when only total phosphorus (out of the eight
parameters) was different (Table 18). Lake Michigan basins were not
different during the winter for these reported parameters, but total
dissolved phosphorus showed a marked decrease in the spring as well as
significant basin differences. Lake Huron also showed a marked decrease
in total dissolved phosphorus between the winter and spring surveys. A
corresponding increase in biological activity can be noted in higher
chlorophyll levels in southern Lake Huron.
Following the procedures used in analysis of the 1983 and 1984
surveillance data, most of the analyses were conducted basin-by-basin
rather than for all basins combined. This was done to facilitate
historical comparisons, and in recognition of the fact that t-test results
represent only the sample data that are used for calculation and not the
populations that the samples are intended to represent. Although we
assume that our sample was representative of the population, a t-test
result indicating that the difference between sample means is not
significantly different from zero (i.e., accept the null hypothesis) does
not necessarily imply that the underlying population means are the same,
only that we have insufficient evidence to conclude that they are
different. Given the uncertainty associated with limnological
-------
58
observations, the t-tests used here can only suggest that basin means are
different, not that they are equal.
WATER COLUMN STRUCTURE
Temperature
One goal of the surveillance program was to sample the three lakes at
three distinct times during the annual thermal cycle. The desired times
were (1) spring after ice out and before stratification, (2) summer, at
maximum stratification, and (3) fall, after turnover.
Figures 4 through 8 (ISSCO, 1984) depict the average basin surface
water temperature measured during each survey leg along with the time
series of daily average surface temperature measured by the National Data
Buoy Office buoys (Hamilton, 1980) deployed in Lakes Erie, Huron, and
Michigan. These figures show how the surveillance sampling periods
related to the annual thermal cycle in these lakes. In Lake Michigan and
Lake Huron, the spring survey was completed on May 2. This survey occurred
well before the lakes began warming above 4°C, which occurred in late May
to mid-June. During June, rapid warming was observed in each lake basin
resulting in epilimnetic water temperatures near maximum by July. Peak
surface temperatures occurred in each basin during August or September.
As a result, the 1985 summer survey occurred later in the stratified
period than in 1983 and 1984. As in 1984, surface temperatures began to
decline in September and all lakes had cooled substantially by the fall
survey. Lake Erie was completely turned over while Lakes Michigan and
Huron had cooled to 9°C or lower temperatures.
The vertical distribution of temperature in each lake basin is
plotted in Figures 9 through 13. The data for these plots were taken from
the basin master stations listed in Table 2. These figures show that the
first survey (16 April to 2 May) was conducted while the deeper basins of
the middle Great Lakes were still stably unstratified, with slightly
warmer water near the bottom. All sites visited in Lake Erie's western
basin were stratified during the first sampling of the spring survey
(April 24-25) and had 'turned over' to a nearly isothermal temperature
structure by April 28th. The central basin had begun to stratify, with
-------
59
CJ
LJ
Q_
LJ
25-
20-
< 15-
10-
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV DEC
Figure 4. Surface water temperature in southern Lake Michigan - 1985.
Survey basin means (squares) are compared to NDBO buoy 45007
data (line) showing the relationship between surveillance
periods and the annual thermal cycle.
25-
o
^ 20-
15-
ce:
LJ
CL
LJ 10-
I—
ce:
LJ
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
Figure 5. Surface water temperature in northern Lake Michigan - 1985.
Survey basin means (squares) are compared to NDBO buoy 45002
data (line) showing the relationship between surveillance
periods and the annual thermal cycle.
-------
60
,0,
LJ
25-
20-
^A
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
Figure 6. Surface water temperature in northern Lake Huron - 1985.
Survey basin means (squares) are compared to NDBO buoy 45003
data (line) showing the relationship between surveillance
periods and the annual thermal cycle.
o,
LJ
DC:
LJ
Q_
S 10-
h-
LJ
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
Figure 7. Surface water temperature in southern Lake Huron - 1985.
Survey basin means (squares) are compared to NDBO buoy 45008
data (line) showing the relationship between surveillance
periods and the annual thermal cycle.
-------
61
30-
CJ,
Ld
c£
a:
o_
LJ
o-
F*
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
Figure 8. Surface water tenperature in western Lake Erie - 1985. Survey
basin means (squares) are compared to NDBO buoy 45005 data
(line) showing the relationship between surveillance periods
and the annual thermal cycle.
several of the western most sites being stratified, while the remainder
of the basin was isothermal. The water temperatures in all basins did
not change appreciably during the spring survey in Lake Michigan and
Huron. The maximum basin temperature increase observed was 0.4°C (about
0.07°C/day) in the southern basin of Lake Huron during the 6-day interval
between sampling visits. This rate of increase was almost twice as fast
as the 1984 rate where a 0.04°c/day increase was observed between the
spring sampling periods.
As designed, the summer survey was completed during the stable
stratified period (August 6 - September 1). Summer epilimnion
temperatures were cooler and thermocline depths (Table 19) were deeper
when compared to 1983 (Lesht and Rockwell, 1985) with epilimnion
temperatures 5 to 10% lower and thermocline depths 10 to 30% greater.
In 1985, Lake Erie's central basin hypoliinnion (1.6m) was about 1/3
as thick as in 1983 and 1984 (Table 20). This thin layer and a larger
than usual oxygen depletion rate (Fay and Rathke, 1987) resulted in an
-------
62
WATER TEMPERATURE (C)
SPRING SUMMER FALL
L MICH. 18 (SOUTHERN BASIN)
0 10 20 0 10 20 0 10
UJ
100
200
300
400
500
20
i i
600 L
Figure 9. Vertical profiles of water temperature in southern Lake
Michigan, station 18, during the spring, summer and fall
surveys. The observed data of the first runs of the spring,
summer and fall surveys are shown as open squares with a solid
smoothing curve. The observed data of the second runs of the
spring and fall surveys as well as the third run of the summer
survey are shown as xs with a dashed smoothing curve.
anoxic hypolimnion. The release of nutrients from the sediments can be
seen in a dramatic increase in phosphorus concentration. In 1985, average
phosphorus concentrations were six times greater for total phosphorus and
twenty seven times greater for ortho phosphorus in the hypolimnion and
nepheloid layer when compared to epilimnion concentrations.
The 1985 fall survey (November 14 - December 4) was conducted two
weeks earlier than the 1984 fall survey and two weeks later than the 1983
fall survey. During this survey, the southern basin of Lake Michigan
-------
63
WATER TEMPERATURE (C)
SPRING SUMMER FALL
L MICH. 41 (NORTHERN BASIN)
0 10 20 0 10 20 0 10 20
UJ
ui
0-
Ul
Q
• i
100
200
300
400
500
600
700
800
900 L
Figure 10. vertical profiles of water temperature in northern Lake
Michigan, station 41, during the spring, sunnier and fall
surveys. The observed data of the first runs of the spring,
summer and fall surveys are shown as open squares with a solid
smoothing curve. The observed data of the second runs of the
spring and fall surveys as well as the third run of the sunnier
survey are shown as xs with a dashed smoothing curve.
turned over between sampling runs providing a quantitative picture of
chemical concentrations before and after turnover. Lake Michigan's
northern basin remained stratified. The stratification in northern Lake
-------
64
0
WATER TEMPERATURE (C)
SPRING SUMMER FALL
a.) L. HURON 45 (NORTHERN BASIN)
0 10 20 0 10 20 0 10 20
100
LJ
x 200
OL
UJ
Q
300
400 L
i i I I
b.) L. HURON 43 (NORTHERN BASIN)
0
100
200
300
ul 400
500
600
Figure 11. Vertical profiles of water temperature in northern Lake Huron,
stations 45 and 43, during the spring, summer and fall
surveys. See Figure 12 for a detailed explanation.
-------
65
0
WATER TEMPERATURE (C)
SPRING SUMMER FALL
a.) L. HURON 93 (SOUTHERN BASIN)
10 20 0 10 20 0 10 20
200
300 L
b.) L. HURON 15 (SOUTHERN BASIN)
100
200
i r
300 L
Figure 12. Vertical profiles of water temperature in southern Lake Huron,
stations 93 and 15, during the spring, summer and fall
surveys. In a). the observed data of the second runs of the
spring, summer and fall surveys are shown as open squares with
a solid smoothing curve. In b). the observed data of the
first runs of the spring, summer and fall surveys are shown as
open squares with a solid smoothing curve. Also in b)., the
observed data of the third run of the summer survey are shown
as xs with a dashed smoothing curve.
Michigan during the Fall-2 was much weaker than in Fall-1 and much deeper
with surface to bottom temperature differentials at the master station
being reduced from 3.7°C to 2.5°C.
Turbidity
Turbidity profiles observed at the master stations during each
-------
66
LJ
CL
LJ
Q
WATER TEMPERATURE (C)
SPRING SUMMER FALL
a.) L. ERIE 57 (WESTERN BASIN)
0 10 20 0 10 20 0 10 20
\J
LJ
LJ
1 1
x' 25
Q.
LJ
Q
SO
'J" '
- n
I 1 1 Ivr
J
n
i
'1
- J
1 1 i >
b.) L. ERIE 78 (CENTRAL BASIN)
u
LJ
LJ
1 1
^ 50
CL
1 1 1
U-LJ
Q
100
•
-
'If I I I I
r
I
t
I I I I i
1
/
&-*r
~i
i i
-
i
i i i i
i
i
i
c.) L. ERIE 15 (EASTERN BASIN)
100
200
i i i i i
LJB
Figure 13. Vertical profiles of water temperature in western, station 57;
central, station 78; and eastern, station 15, Lake Erie,
during the spring, summer and fall surveys. The observed data
of the first runs of the spring, summer and fall surveys are
shown as open squares with a solid smoothing curve. The
observed data of the second runs of the spring and fall
surveys as well as the third run of the summer survey are
shown as xs with a dashed smoothing curve.
survey are plotted in Figures 14 through 18. These profiles suggest the
presence of a benthic nepheloid layer (Bell et al. , 1980) in the deeper
basins of each lake after thermal stratification. Data from the spring
survey suggest that similar high turbidity layers may exist in all deep
basins near the bottom during the winter, too, when the lake is again
-------
Table 19. Average epiliimion tenperature and thenrocline depth3 by survey and basin, 1985.
Ebilitmion tenperature (°C)
Surveys Winter 1
January
Basins
lake Michigan
South -13
North
Lake Huron
North 1.7
South 2.0
Late Erie
West 0.0
Central 2.0
East 3.2
Winter 2 Spring Summer Fall 1 Fall 2 Sunnier Fall 1 Fall 2
February
2.0 2.5 20.7 8.3 5.4 20.5 + 3.0 (18) 51.6 + 5.7 (5) *°
1.5 2.5 18.5 8.1 6.5 20.8 ± 3.7 (15) 60.1 + 11.4 (5) 91.2 ± 20 (5)
0.8 1.5 17.6 7.9 6.2 17.1 + 2.6 (17) 56.4 + 10.7 (6) *
0.2 1.8 19.7 8.2 6.9 19.6 ± 1.8 (13) 59.0 + 11.8 (3) 68.9 (1)
Fall 1 & 2 Fall 1 & 2
0.0 12.0 22.5 7.0 - *
0.0 5.1 22.2 10.6 19.7 + 1.5 (27) *
0.0 2.1 21.8 10.4 20.2 + 0.9 (8) *
alhennocline depth + one standard deviation with number of stations in parentheses.
t>»-» indicates no data.
CH*H indicates isothermal conditions.
-------
68
Table 20. Summer survey estimated layer thickness (meters) and the
percentage of total average basin depth in the central and
eastern basins of Lake Erie, 1983, 1984 and 1985.
Central Basin
Epilimnion Thickness
Mesolimnion Thickness
Hypolimnion Thickness
Total Depth
Eastern Basin
Epilimnion Thickness
Mesolimnion Thickness
Hypolimnion Thickness
Total Deptha
1983
1984
Thickness
meters (%)
12.6
4.2
5.4
22.2
(57)
(19)
(24)
Thickness
meters (%)
14.4
10.5
22.2
47.0
(31)
(22)
(47)
Thickness
meters ( % )
14.7
3.5
4.3
22.5
(66)
(15)
(19)
Thickness
meters (%)a
15.2
8.2
47.3
(32)
(17)
(50)
1985b*
Thickness
meters (%)
18.8
1.5
21.9
(86)
(07)
(07)
Thickness
meters (%)
17.8
6.3
19.7
43.8
(41)
(14)
(45)
aTotals and % may not add up due to rounding.
^Station network expanded to IJC 1986 Lake Erie GLISP recommended
locations.
thermally stable. Nepheloid layers in the Great Lakes have been a
subject of interest (Sandilands and Mudroch, 1983; Eadie et al. , 1984)
because of the high concentrations of many chemical species associated
with the particulate matter forming that layer. Table 21 shows the
contrasts between parameter concentration within the benthic nepheloid
layer (here defined as the BIO and B2 samples in Lakes Michigan and Huron
and BIO and Bl in Lake Erie) and the hypolimnion in Lakes Michigan, Huron,
and Erie.
Nutrients
Vertical profiles of major nutrient concentrations measured at 1985
master stations are plotted in Figures 19 to 28. These profiles show
epilimnetic depletion of dissolved silicon and nitrate + nitrite nitrogen
during the summer survey, along with hypolimnetic and nepheloid
enrichment. These nutrients are reintroduced after "fall overturn" into
the eplimnetric waters resulting in a generally isoclinic concentration.
-------
69
TURBIDITY (HACH FTU)
SPRING SUMMER
L MICH. 18 (SOUTHERN BASIN)
0 2.0 4.0 2.0 4.0
FALL
2.0
4.0
Lul
100
200
300
o.
Q 400
500
\\
600 L L
Figure 14. Vertical profiles of turbidity in southern Lake Michigan,
station 18, during the spring, summer and fall surveys. The
observed data of the first runs of the spring, suirmer and fall
surveys are shown as open squares with a solid smoothing
curve. The observed data of the second runs of the spring and
fall surveys as well as the third run of the summer survey are
shown as xs with a dashed smoothing curve.
Stations LM18, LH43, and LH93 sampled on Fall-1 before the fall overturn
and stations LM18, LH45, and LM15 sampled on Fall-2 after overturn clearly
demonstrate the breakdown of the deep thermocline and effect of the "fall
overturn." The Fall-2 profiles are similar to corresponding spring
profiles while Fall-1 profiles are similar to summer profiles. Fall-2
overturn concentrations are generally equal to or lower than the
corresponding spring concentrations for nitrate + nitrite nitrogen, while
Fall-2 dissolved silicon concentrations are generally equal to or higher
than corresponding spring concentrations. These patterns are also
-------
70
TURBIDITY (HACH FTU)
SPRING SUMMER FALL
L MICH. 41 (NORTHERN BASIN)
0_ 2.0 4.0 2.0 4.0 2.0 4.0
UJ
o
k ' '
i i \
«
•\
100
200
300
400
500
600
700
800
900
Figure 15. Vertical profiles of turbidity in northern Lake Michigan,
station 41, during the spring, summer and fall surveys. The
observed data of the first runs of the spring, summer and fall
surveys are shown as open squares with a solid smoothing
curve. The observed data of the second runs of the spring and
fall surveys as well as the third run of the summer survey are
shown as xs with a dashed smoothing curve.
observed in eastern Lake Erie and western Lake Erie. Central Lake Erie
differs in that epilinmetic nutrient enrichment occurred during the August
survey (when compared to spring nutrient levels) due to reintroduction of
-------
71
0
TURBIDITY (HACH FTU)
SPRING SUMMER
a.) L HURON 45 (NORTHERN BASIN)
0 2.0 4.0 2.0 4.0
FALL
2.0 4.0
ui
UJ
Q.
ui
O
100
200
300
400 L
b ) L. HURON 43 (NORTHERN BASIN)
0
^
UI
Q
£' I I '
100 -
200
300
ui 400
500
600 L
Figure 16. Vertical profiles of turbidity in northern Lake Huron,
stations 45 and 43, during the spring, summer and fall
surveys. See Figure 17 for a detailed explanation.
I I I I
-------
72
LJ
LU
U.
Ld
LI-
TURBIDITY (HACH FTU)
SPRING SUMMER
a.) L. HURON 93 (SOUTHERN BASIN)
0 2.0 4.0 2.0 4.0
FALL
2.0
4.0
100
a. 200
LJ
O
300
i i
b.) L HURON 15 (SOUTHERN BASIN)
100
1 I I I
n i i
ui 200
300 L
Figure 17. Vertical profiles of turbidity in southern Lake Huron,
stations 93 and 15, during the spring, sumner and fall
surveys. In a). the observed data of the second runs of the
spring, summer and fall surveys are shown as open squares with
a solid smoothing curve. In b). the observed data of the
first runs of the spring, summer and fall surveys are shown as
open squares with a solid smoothing curve. Also in b)., the
observed data of the third run of the summer survey are shown
as xs with a dashed smoothing curve.
soluble nutients from the anoxic hypoliimion.
Because the nepheloid layers were so distinct after stratification,
samples taken within them are included as a separate subset in the
statistical summaries that follow. These subsets differ from 1983 and
1984 analyses (Lesht and Rockwell, 1985 and 1987) in that only Bl, B2
-------
73
0.
Ul
Q.
Ul
Q
0
TURBIDITY (HACH FTU)
SPRING SUMMER FALL
a.) L. ERIE 57 (WESTERN BASIN)
0 10 20 10 20 10
20
-i
!i
i;
- 1 /
b.) L ERIE 78 (CENTRAL BASIN)
U
Ul
Ul
U.
^ 50
0.
1 i 1
LLJ
Q
mn
i i i i i
i i i i
9f
_
I I I I
i
c.) L. ERIE 15 (EASTERN BASIN)
0
100
200
Figure 18. Vertical profiles of turbidity in western, station 57;
central, station 78; and eastern, station 15, LaKe Erie,
during trie spring, surmer and fall surveys. The observed data
of the first runs of the spring, simmer and fall surveys are
shown as open squares with a solid smoothing curve. The
observed data of the second runs of the spring and fall
surveys as well as the third run of the sumner survey are
shown as xs with a dashed smoothing curve.
and/or BIO depths are included in the nepheloid layer if the depths were
below the thermocline. If the theromocline was deeper than BIO or if
the water column was isothermal, these depths were not included in the
nepheloid layer.
-------
Table 21. Conparison of sinner survey basin mean values of turbidity, nutrients, conductivity, and temperature in the
hypolimnia and nepheloid layers of Takes Michigan, Huron and Erie, 1985. a,b
Parameter
Turbidity (FIU)
Dissolved reactive silicon
Nitrate + nitrite nitrogen
Total phosphorus
Total dissolved phosphorus
Dissolved ortho phosphorus
Conductivity (uS/cm)
Temperature (°C)
Turbidity (FIU)
Dissolved reactive silicon
Nitrate + nitrite nitrogen
Total phosphorus
Total dissolved phosphorus
Dissolved ortho phosphorus
Conductivity (uS/on)
T&iperature (°C)
Turbidity (FIU)
Dissolved reactive silicon
Nitrate + nitrite nitrogen
Total phosphorus
Total dissolved phosphorus
Dissolved ortho phosphorus
Conductivity (uS/on)
Temperature (°C)
Southern lake Michigan
Hypoliimion Nepheloid tc
0.32 + 0.18 (34)
431 + 204 (34)
274 + 23 (34)
3.5 + 1.4 (34)
1.6 + 1.1 (34)
0.6 + 0.7 (22)
281.1 ± 0.81 (34)
4.9 + 0.7 (34)
Hypoliimion
0.34 + 0.13 (19)
767 + 133 (19)
334 + 21 (19)
2.9 + 0.8 (19)
1.2 + 0.5 (19)
0.5 + 0.3 (19)
205.9 + 1.84 (19)
5.7 + 0.8 (19)
Hypolimnion
1.59 + 0.40 (10)
303 + 83 (10)
346 + 35 (10)
7.1 + 2.4 (10)
2.5 + 0.8 (10)
2.5 + 0.9 (10)
286.6 + 1.4 (10)
5.8 + 1.1 (10)
0.88 + 0.45 (35)
906 + 298 (36)
316 + 18 (36)
6.0 + 3.2 (35)
3.7 + 2.7 (36)
2.6 + 2.2 (23)
283.1 + 0.96 (36)
4.1 + 0.3 (36)
Southern Lake Huron
Nepheloid
1.14 + 0.67 (25)
1061 + 161 (25)
363 + 19 (25)
4.1 + 1.4 (25)
1.1 + 0.3 (25)
0.7 + 0.3 (25)
206.8 + 1.65 (25)
4.8 + 0.6 (25)
Eastern Lake Erie
Nepheloid
1.92 + 0.33 (16)
341 + 59 (16)
349 + 28 (16)
7.5 + 2.6 (16)
3.4 + 2.1 (16)
2.8 + 0.6 (15)
287.0 + 1.3 (16)
5.7 + 1.2 (16)
-6.82*
-7.80*
-8.48*
-4.33*
-4.21*
-5.22*
-8.31*
5.74*
t
-5.84*
-6.49*
-4.85*
-3.47*
+0.76*
-2.01*
-1.53
4.45*
t
-2.29*
-1.34*
-0.25*
-0.36
-1.49
-1.17
-0.81
+0.33
Northern Lake Michigan
Hypolimnion Nepheloid t
0.20 + 0.10 (37)
420 + 97 (37)
283 + 15 (37)
3.4 + 1.6 (36)
1.6 + 1.0 (36)
0.9 + 0.7 (37)
281.4 + 0.79 (37)
4.5 + 0.6 (37)
Hypolimnicn
0.29 + 0.09 (29)
685 + 90 (29)
323 + 21 (29)
2.8 + 1.1 (29)
1.5 + 0.8 (29)
0.4 + 0.4 (29)
204.4 + 1.21 (29)
5.1 + 0.8 (29)
0.75 + 0.27(30) -10.76*
1004 + 199 (30) -14.72*
314 + 15 (30) -
8.0 + 2.3 (30) -
5.7 + 2.3 (30) -
4.0 + 2.6 (30) -
283.1 + 1.11 (30) -
3.8 + 0.1 (30) +
Northern Lake Huron
Nepheloid
0.92 + 0.55 (34) -
8.36*
9.71*
9.08*
6.36*
7.08*
6.87*
t
6.61*
977 + 127 (34) -10.37*
354 + 14 (34) -
3.3 + 1.6 (34) -
1.3 + 0.5 (34) +
0.6 + 0.5 (34) -
204.8 + 0.92 (34) +
4.1 + 0.2 (34) +
6.73*
1.34*
0.84*
1.67*
1.62*
6.18*
Values given are means + cne standard deviation with the number of samples in parentheses.
^kll nutrient concentrations are in ug/L-
°t value significant to reject null hypothesis that hypoliimion and nepheloid values are equal, alpha= 0.05.
-------
75
DISSOLVED SILICON (/ig/L)
SPRING SUMMER FALL
L. MICH. 18 (SOUTHERN BASIN)
0 1000 2000 1000 2000 1000 2000
UJ
100
200
300
400
500
600 L
Figure 19. Vertical profiles of dissolved silicon in southern Lake
Michigan, station 18, during the spring, sunnier and fall
surveys. The observed data of the first runs of the spring,
summer and fall surveys are shown as open squares with a solid
smoothing curve. The observed data of the second runs of the
spring and fall surveys as well as the third run of the summer
survey are shown as xs with a dashed smoothing curve.
Vertical profiles of some of the other nutrient concentrations
measured at selected master stations during 1985 are plotted in Figures 29
to 32. These profiles show (1) the deep thermocline maxima of ammonia
nitrogen which occurs in the summer; (2) the general low concentration of
total and total dissolved phosphorus throughout the water column with
summer and fall elevated concentrations in the hypoliinnion and nepheloid
layers; and (3) the dramatic increase in phosphorus concentrations in the
central basin of Lake Erie during the stratified period when anoxic
conditions occur.
-------
76
DISSOLVED SILICON (/*g/L)
SPRING SUMMER FALL
L MICH. 41 (NORTHERN BASIN)
0 1000 2000 1000 2000 1000 2000
CL
LJ
O
100
200
300
400
500
600
700
800
900 L
Figure 20. Vertical profiles of dissolved silicon in northern Lake
Michigan, station 41, during the spring, summer and fall
surveys. The observed data of the first runs of the spring,
summer and fall surveys are shown as open squares with a solid
smoothing curve. The observed data of the second runs of the
spring and fall surveys as well as the third run of the summer
survey are shown as xs with a dashed smoothing curve.
-------
77
ui
ui
DISSOLVED SILICON
SPRING SUMMER
a.) L HURON 45 (NORTHERN BASIN)
0 1000 2000 1000 2000
100
X 200
£
LU
a
300
400 L
b.) L. HURON 43 (NORTHERN BASIN)
0
100
200
300
ui 400
Q
500
600 L
Figure 21. Vertical profiles of dissolved silicon in northern Lake Huron,
stations 45 and 43, during the spring, sunnier and fall
surveys. See Figure 22 for a detailed explanation.
FALL
1000 2000
-------
78
DISSOLVED SILICON (/xg/L)
SPRING SUMMER FALL
a.) L HURON 93 (SOUTHERN BASIN)
0 1000 2000 1000 2000 1000 2000
UJ
I
100
200
1 I
b.) L HURON 15 (SOUTHERN BASIN)
i i i i
0
100
EJ 200
a
300 L
Figiire 22. Vertical profiles of dissolved silicon in southern Lake Huron,
stations 93 and 15, during the spring, summer and fall
surveys. In a). the observed data of the second runs of the
spring, simmer and fall surveys are shown as open squares with
a solid smoothing curve. In b). the observed data of the
first runs of the spring, summer and fall surveys are shown as
open squares with a solid smoothing curve. Also in b). , the
observed data of the third run of the summer survey are shown
as xs with a dashed smoothing curve.
PARAMETER MEAN VALUES BY BASIN, SURVEY, AND LAYER
The surveillance data were edited before final statistical analyses
were performed. The editing procedure consisted primarily of correcting
data entry errors that occurred when the raw data were entered into the
STORET Water Quality Database and of eliminating a few data outliers.
-------
79
0-
Ul
Q
ui
ui
OL
ui
Q
ui
ui
u.
a.
UI
0
25
50
DISSOLVED SILICON
SPRING SUMMER
a.) L. ERIE 57 (WESTERN BASIN)
0 1000 2000 1000 2000
FALL
1000 2000
b.) L ERIE 78 (CENTRAL BASIN)
0 •
50
100
0
100
200
c.) L ERIE 15 (EASTERN BASIN)
Figure 23. Vertical profiles of dissolved silicon in western, station 57;
central, station 78; and eastern, station 15, Lake Erie,
during the spring, sunnier and fall surveys. The observed data
of the first runs of the spring, sunnier and fall surveys are
shown as open squares with a solid smoothing curve. The
observed data of the second runs of the spring and fall
surveys as well as the third run of the sunmer survey are
shown as xs with a dashed smoothing curve.
Outliers were identified in the course of the initial statistical
processing. Bctreme values were checked against the original survey and
analysis logs and kept unless there was evidence of either contamination
or analytical error. Since data values determined to be below the
criterion of detection for a particular parameter were entered into the
-------
80
NITRATE+NITRITE-NITROGEN (mg/L)
SPRING SUMMER FALL
L. MICH. 18 (SOUTHERN BASIN)
0 0.2 0.4 0.2 0.4 0.2 0.4
u
100
200
P
LJ
g 300
X
Q.
Q 400
500
ROD
i i '
- 1
-
-
- t
~
; 1
i i
—
-
~
\
*
i i
~
i-
~
-
•('
\
i
Figure 24. Vertical profiles of dissolved nitrate+nitrite nitrogen in
southern Lake Michigan, station 18, during the spring, summer
and fall surveys. The observed data of the first runs of the
spring, simmer and fall surveys are shown as open squares with
a solid smoothing curve. The observed data of the second runs
of the spring and fall surveys as well as the third run of the
sunnier survey are shown as xs with a dashed smoothing curve.
database as real values rather than "less than" values, these values were
included in the statistical summary. This is in accordance with the
recommendations of the International Joint Commission's Data Quality Work
Group (Clark, 1980).
Tables 22 through 24 present mean parameter values for each basin,
survey, and layer, when applicable. During spring isothermal periods
prior to stratification all samples are called "epilimnion" (STQRET
profile codes 50, 450.5, and 505). During stratified periods the
-------
81
NITRATE+NITRITE-NITROGEN (mg/L)
SPRING SUMMER FALL
L MICH. 41 (NORTHERN BASIN)
0 0.2 0.4 0.2 0.4 0.2 0.4
o.
Lul
O
100 -
200 -
300 -
400 -
500
600
700
800
900 L
Figure 25. Vertical profiles of dissolved nitrate+nitrite nitrogen in
northern Lake Michigan, station 41, during the spring, simmer
and fall surveys. The observed data of the first runs of the
spring, surrmer and fall surveys are shown as open squares with
a solid smoothing curve. The observed data of the second runs
of the spring and fall surveys as well as the third run of the
sunnier survey are shown as xs with a dashed smoothing curve.
epilimnion includes samples taken from the surface and including the
sample at the upper knee of the thermocline (STORET profile codes 100-
200), and the mesolimnion includes samples taken at the thermocline
-------
82
NITRATE+NITRITE-NITROGEN (mg/L)
SPRING SUMMER FALL
a.) L. HURON 45 (NORTHERN BASIN)
0 0.2 0.4 0.2 0.4 0.2 0.4
100
200
300
400 L
I 1 I
b.) L HURON 43 (NORTHERN BASIN)
0
100
200
300
400
500
ii isi i i i s i
\
Figure 26. Vertical profiles of dissolved nitrate+nitrite nitrogen in
northern Lake Huron, stations 45 and 43, during the spring,
summer and fall surveys. See Figure 27 for a detailed
explanation.
-------
83
NITRATE+NITRITE-NITROGEN (mg/L)
SPRING SUMMER FALL
a.) L. HURON 93 (SOUTHERN BASIN)
0 0.2 0.4 0 0.2 0.4 0 0.2 0.4
100
200
1 ' 1
i r
T i
b.) L. HURON 15 (SOUTHERN BASIN)
Ul
L^
X
100
200
i i i
300 L
Figure 27. Vertical profiles of dissolved nitrate+nitrite nitrogen in
southern Lake Huron, stations 93 and 15, during the spring,
summer and fall surveys. In a). the observed data of the
second runs of the spring, sumner and fall surveys are shown
as open squares with a solid smoothing curve. In b). the
observed data of the first runs of the spring, summer and fall
surveys are shown as open squares with a solid smoothing
curve. Also in b)., the observed data of the third run of the
summer survey are shown as xs with a dashed smoothing curve.
(STORET profile code 300). The hypoliinnion includes all samples taken at
and below the lower knee of the thermocline which are not in the
nepheloid layer (profile code 350-400), and the nepheloid layer is defined
as including samples taken within 10 m of the bottom (profile codes 450-
500) and below the thermocline. Samples taken within 10 m of the bottom
but not in the nepheloid layer are placed in appropriate layers. S1DKET
-------
84
Ul
Ul
u.
CL
O
UJ
UJ
u.^
IE
a!
LU
Q
NITRATE+NITRITE-NITROGEN (mg/L)
SPRING SUMMER FALL
a.) L. ERIE 57 (WESTERN BASIN)
0 0.4 0.8 0 0.4 0.8 0 0.4 0.8
50
b.) L ERIE 78 (CENTRAL BASIN)
50
100
0
100
200
c.) L. ERIE 15 (EASTERN BASIN)
L H
Figure 28. Vertical profiles of dissolved nitrate+nitrite nitrogen in
western, station 57; central, station 78; and eastern, station
15, Lake Erie, during the spring, sunnier and fall surveys.
The observed data of the first runs of the spring, summer and
fall surveys are shown as open squares with a solid smoothing
curve. The observed data of the second runs of the spring and
fall surveys as well as the third run of the summer survey are
shown as xs with a dashed smoothing curve.
profile codes 451.5, 452, and 520 are epilimnion samples. STQRET profile
codes 453, 530 are mesolimnion samples. STORET profile codes 453.5 and
535 are hypolimnion samples. These codes are used primarily in Lake Erie
where the thermocline is generally located within 10 meters of the Lake
-------
85
AMMONIA-N (mg/L) TOTAL P (mg/L) DIS P (mg/L)
L MICH. 18 (SOUTHERN BASIN)
0 0.02 0.04 0 0.02 0.04 0.01 0.02
LJ
Lu
CL
LJ
O
100
200
300 &/
400
7
i i
/
I
fl
r
\
500 "k- * •«
600 L
Figure 29. Vertical profiles of dissolved ammonia nitrogen, total
phosphorus and total dissolved phosphorus in southern Lake
Michigan, station 18, during the spring, summer and fall
surveys. The observed data of the second run of the spring
survey are shown as solid squares with a solid smoothing
curve. The observed data of the third run of the summer
survey are shown as open squares with a dashed smoothing
curve. The observed data of the second run of the fall survey
are shown as solid dots with a short-dashed smoothing curve.
bottom during August.
Appendix A.
A complete statistical summary is included in
CCMPOSITED UPPER 20-METER SAMPLES
In addition to the water samples taken at discrete depths, one
composite sample composed of equal volumes of water taken from several
depths in the upper twenty meters of the water column (i.e., at l, 5, 10,
and 20 meters) was obtained at each station where the water column
-------
86
0
AMMONIA-N (mg/L) TOTAL P (mg/L) DIS P (mg/L)
L MICH. 41 (NORTHERN BASIN)
0 0.02 0.04 0 0.02 0.04 0.01 0.02
100
200
300
400
uJ 500
o
600
700
800 .
i l l
i l l
\
[ \
,4
•
900
Figure 30. Vertical profiles of dissolved ammonia nitrogen, total
phosphorus and total dissolved phosphorus in northern Lake
Michigan, station 41, during the spring, summer and fall
surveys. The observed data of the second run of the spring
survey are shown as solid squares with a solid smoothing
curve. The observed data of the third run of the summer
survey are shown as open squares with a dashed smoothing
curve. The observed data of the second run of the fall survey
are shown as solid dots with a short-dashed smoothing curve.
-------
87
AMMONIA-N (mg/L) TOTAL P (mg/L) DIS P (mg/L)
a.) L. HURON 45 (NORTHERN BASIN)
0 .004 .008 0 0.02 0.04 0.01 0.02
\J
100
.J-X
UJ
LJ
U.
^r 200
0.
UJ
Q
300
4nn
i
— *
i
1
_ i
*
<
i
"~ f
•
i
t
_ *
i
f
«
i
•
-
o
i
I
J
I I I I
b.) L HURON 15 (SOUTHERN BASIN)
0
LJ 100
Ld
U-,
1.
£ 200
Q
1 1
Figure 31. Vertical profiles of dissolved ammonia nitrogen, total
phosphorus and total dissolved phosphorus in northern,
station 45; and southern, station 15, Lake Huron, during the
spring, sunnier and fall surveys. The observed data of the
second run of the spring survey are shown as solid squares
with a solid smoothing curve. The observed data of the second
run of the sunnier survey are shown as open squares with a
dashed smoothing curve. The observed data of the second run
of the fall survey are shown as solid dots with a short-dashed
smoothing curve.
equaled or exceeded twenty meters. Equal aliquots were taken from the
prescribed samples depths for stations with less than twenty meters of
water in Lake Erie's western basin. This sample, intended primarily for
-------
88
0.
UJ
Q
AMMONIA-N (mg/L) TOTAL P (mg/L) DIS P (mg/L)
a.) L. ERIE 57 (WESTERN BASIN)
0 0.04 0.08
0 0.02 0.04
0.01 0.02
u
UJ
UJ
u_
*= 25
t—
QL
1 1 1
LLJ
Q
50
f\* ' ' '
\
y
1 ry ' '
T\
a I
ff^ l l 1
1
I
I
b.) L. ERIE 78 (CENTRAL BASIN)
u
UJ
UJ
u.
x' 50
| —
CL
1 i 1
LLJ
Q
mn
IT11
•
* &
• ^
i
i ^^
i
i •
J: ' •
«
^
^
, ;
\ i
*
J'V
f
f ^
-1
f
. I
1*1 1
;
;'
vsf
' ^^
\ B
c.) L. ERIE 15 (EASTERN BASIN)
0
100
200
i r
r1?
\
\'
*
i i
Figure 32. Vertical profiles of dissolved ammonia nitrogen, total
phosphorus and total dissolved phosphorus in western, station
57; central, station 78; and eastern, station 15, Lake Erie,
during the spring, sunrner and fall surveys. The observed data
of the second run of the spring survey are shown as solid
squares with a solid smoothing curve. The observed data of
the first (c) or third (a and b) run of the summer survey are
shown as open squares with a dashed smoothing curve. The
observed data of the second run of the fall survey are shown
as solid dots with a short-dashed smoothing curve.
the analysis of plankton, was also analyzed for chlorophyll-a, nutrients,
chloride, and sulfate. The mean values of these constituents averaged
over the survey and basin are shown in Table 25.
-------
Table 22. Parameter means by basin, survey, and layer — Lake Michigan, 1985.
Chloro-
Survey/layer Tsnperature Turbidity phyii-a
(°C) (FHJ) (ug/L)
WLnter-2
E^ilimnicn
Scaring
E£>iliinnion
Sunnier
EJpiliirnion
IVfesoliimian
H^limnion
Nepheloid
Eall-l
Epilimnicn
Lfesolirtnion
Hypoliimion
Neptheloid
Eall-2
E£iliirinicn
Mesolimnion
B^politmion
Neciieloid
Winter-2
Bpilimnian.
Spring
E^iliirnion
Sunnier
EJpilimion
J^fesoliirnion
Hypolimion
Nefineloid
Fall-1
EjDilirmion
IVfesolimion
H^linriion
Nepheloid
Fall-2
E£dlinnion
1.5
2.5
18.5
12.3
4.5
3.8
8.1
6.6
4.3
3.9
6.5
5.2
4.2
4.2
a
0.34
0.36
0.28
0.20
0.75
0.23
0.19
0.20
0.84
0.26
0.32
0.34
0.74
0.89
0.75
1.00
1.32
0.74
0.44
0.78
0.14
0.05
0.08
0.32
0.13
0.04
0.06
Pheqphytin
(ug/L)
Total Total
Total dissolved Qrtho ND2 + ND3 KH3 Kjeldahl
Hiosphorus Phosptorus PhosfiTorus Nitrogen Nitrogen Nitrogen
(ug/L) (ug/L) (ug/L) (ug/L) (ug/L) (ug/L)
Northern Basin
-0.12 5.6
-0.01
0.12
0.30
0.24
0.28
0.23
0.12
0.10
0.27
0.11
0.09
0.06
0.10
5.2
4.5
5.6
3.4
8.0
3.2
2.2
3.3
9.0
4.3
4.4
6.4
8.3
4.1
2.8
1.2
1.3
1.6
5.8
2.1
1.8
3.2
6.9
3.0
4.0
5.6
6.9
1.8
0.9
0.4
0.6
0.9
4.0
-0.3
-0.3
1.4
4.2
0.4
1.0
2.6
3.5
290.5
286.3
155.6
195.8
282.7
313.7
232.1
279.0
293.1
310.9
246.4
276.3
288.6
294.8
4.4
1.6
3.6
9.9
3.5
1.0
1.4
0.8
0.6
1.0
1.5
1.5
1.2
1.4
200.0
80.5
183.7
177.3
127.4
132.2
102.5
112.0
73.8
107.0
46.7
73.0
46.1
26.2
Southern Basin
2.0
2.6
20.7
13.9
4.9
4.1
8.3
6.7
4.7
4.3
5.4
-
0.40
0.48
0.45
0.32
0.88
0.25
0.32
0.30
0.80
0.45
0.79
0.95
1.12
1.23
1.07
0.71
0.56
0.22
0.13
0.09
0.32
-0.07
0.05
0.19
0.28
0.37
0.39
0.16
0.10
0.06
0.13
0.10
5.8
4.9
2.5
3.5
3.5
6.0
4.0
2.7
3.4
4.9
5.5
4.7
2.4
1.4
1.7
1.6
3.7
2.4
1.5
2.1
3.3
2.8
2.6
0.9
0.4
0.4
0.6
2.6
0.2
0.6
0.8
2.6
0.0
293.0
292.5
159.1
193.6
274.2
316.0
248.9
289.4
310.0
331.4
289.7
4.5
3.0
2.3
14.0
5.6
0.5
2.4
1.4
3.3
1.0
1.2
96.2
118.9
213.4
205.7
170.6
160.0
168.0
186.0
207.1
223.0
67.2
00
a"-" indicates no data.
-------
Table 22. (Continued) Parameter means — lake Michigan, 1985.
Aerobic
Dissolved Specific Dissolved
Survey/layer reactive pH Alkalinity Conductance Oxygen ci~ S042~ Ca2+ Mj2+ Na+ K+ Hsterotropii
silicon (mg/L) (uS/on) (mg/L) (mg/L) (mg/L) (ng/L) (mg/L) mg/L mg/L (Count/ML)
(ug/L)
Winter-1
Epilimnion
Spring
Epilimnion
Sunnier
Epilimnion
I\fesoliimion
Hypoliimion
Nepheloid
Fall-1
Epilimnion
IVfesolirmion
HypoliitTiion
Nepheloid
Fall-2
Epilimnion
IVfesoliimion
Hypolimnion
Nepheloid
Winter-2
Epiliirnion
Spring
Epilimnion
Sumner
Epiliinnion
IVfesolimnion
Hypoliimion
Nepheloid
Fall-1
Epiliinnion
IVfesoliimion
Hypolinrdon
Nepneloid
Fall-2
Epilinmion
545.2
562.8
92.9
144.9
420.2
1003.6
337.6
409.2
588.5
162.5
410.4
623.8
765.9
922.7
574.4
566.0
97.1
110.2
431.5
906.1
389.0
509.2
669.3
935.3
609.6
8.03
8.17
8.54
8.45
8.18
8.08
8.36
8.20
8.18
8.10
8.19
8.16
8.16
8.04
8.05
8.12
8.58
8.48
8.16
8.07
8.34
8.19
8.14
8.09
8.12
109.5
107.9
108.0
108.4
108.3
109.0
107.2
107.4
107.8
108.5
107.1
107.0
107.7
107.6
109.4
108.5
108.1
108.6
108.4
108.9
107.0
107.0
107.8
108.3
107.7
283.5
279.8
276.6
279.0
281.4
283.1
281.1
282.8
283.1
285.0
278.7
279.6
281.3
281.6
281.6
279.9
277.7
279.4
281.4
283.1
282.0
283.0
283.3
284.8
279.6
Northern
12.8
12.7
9.9
12.3
12.6
11.9
10.8
11.0
11.4
10.8
12.0
12.2
12.2
12.1
Southern
12.8
12.4
9.5
11.8
12.3
11.9
9.9
10.1
10.4
10.0
11.4
Basin
9.0
8.8
8.6
8.5
8.5
8.5
8.6
8.6
8.6
8.6
8.9
8.9
8.9
8.9
Basin
10.1
8.7
8.8
8.7
8.6
8.6
9.0
8.9
9.0
9.1
8.7
22.4 -
22.3 -
21.6 35.2 11.0 5.4 1.2
21.8 -
22.0 -
22.0 35.9 11.0 5.4 1.2
21.7 - - -
21.8 - - -
22.0 - - -
21.7 - - -
21.8 - - - -
21.9 - - -
21.9 - - -
22.0 - - -
20.1 - - -
22.0 - - - -
21.7 36.0 11.2 5.5 1.2
21.8 - - -
21.6 - -
21.7 36.4 11.1 5.3 1.2
22.0 - - - -
21.6 - - -
21.8 - - - -
21.9 - - -
23.2 - - -
—
1.4
101.5
129.4
99.8
16.9
_
20.0
16.4
—
—
_
-
_
2.0
37.1
190.0
94.8
95.0
27.9
—
47.2
76.8
-
10
o
-------
Table 23. Parameter means by basin, survey, and layer — Lake Hurcn, 1985.
Survey/layer Taiperature TUrbidity
("O (FIU)
WLnter-1
Epilinnicn
wtnter-2
QDiliimicn
faring
EjDilimnicn
Sunner
E}?i.linni.cn
tfe9olinru.cn
Hypoliimicn
Nefneloid
Eill-1
Efdlinriicn
Masolinnicn
Ifypolirmicn
Nefteloid
Rall-2
EJpilinnicn
Winter-l
EJpilinrrion
Winter-2
Efcdlinnicn
Spring
Epilijmicn
Sunrner
EJpilinriicn
Masolirmion
Hypoliimicn
Nsfteloid
EeLLl-1
Efiliimicn
Mssoliimion
Hypoliimion
NejiielQid
Eall-2
E£>ilinnicn
Mssolinnicn
Hypolmrd.cn
Nefheloid
1.8
0.8
1.5
17.7
12.1
5.1
4.1
7.9
6.3
4.6
4.3
6.2
a
-
0.39
0.21
0.24
0.29
0.92
0.21
0.24
0.36
0.57
0.43
Oiloro-
fiiyll-a
(ug/L)
Tbtal
Hieophytin Hnsphorus
(ug/L) (ug/L)
Data!
dissolved
Hnsphorus
(ug/L)
Ttrtal
Ortln ND2 + ND3 Mi3 Kjeldahl
Hnsphorus Nitrogen Nitrogen Nitrogen
(ug/L) (ug/L) (ug/L) (ug/L)
Northern Basin
0.89
0.80
0.78
1.00
1.61
1.47
0.66
0.58
0.23
0.14
0.07
0.30
-0.02
-0.10
0.02
0.17
0.21
0.36
0.42
0.09
0.13
0.04
0.11
0.08
3.0
3.7
3.3
2.8
2.9
2.8
3.3
2.9
2.3
2.2
3.1
3.8
2.1
2.4
1.3
1.9
1.1
1.5
1.3
1.1
1.1
1.4
1.4
0.9
0.8
0.8
0.3
0.3
0.3
0.4
0.6
0.0
0.3
0.3
0.7
0.0
335.5
303.8
302.1
266.8
284.0
323.2
353.8
308.0
338.0
355.6
362.8
300.7
0.8
3.2
2.2
1.8
2.3
3.3
2.2
2.5
2.0
1.4
1.9
2.0
213.3
148.3
76.3
159.0
188.8
129.1
124.2
88.3
56.7
62.0
64.6
119.9
Southern Basin
2.0
0.2
1.8
19.7
13.8
5.8
4.8
8.3
6.9
5.6
5.3
6.9
6.5
5.2
5.1
-
-
0.53
0.25
0.28
0.34
1.14
0.31
0.45
0.57
0.71
0.42
0.42
0.63
0.72
0.85
1.30
1.09
1.36
2.77
0.94
0.88
0.60
0.27
0.20
0.15
0.40
0.20
0.00
0.10
0.02
-0.21
-0.04
0.13
0.25
0.29
0.30
0.15
0.13
0.17
0.17
0.05
0.00
0.20
0.05
4.8
5.0
3.6
2.3
3.0
2.9
4.1
3.0
2.5
3.2
3.9
3.7
3.0
3.3
3.7
3.0
2.0
1.3
1.2
1.2
1.2
1.1
0.8
0.6
1.8
1.5
2.1
2.1
1.7
3.3
1.9
0.9
0.5
0.5
0.6
0.5
0.7
0.5
0.3
0.6
0.5
-0.5
-0.9
-0.3
0.0
331.3
329.3
300.9
276.4
297.2
334.2
362.1
327.5
339.3
348.3
353.2
2%. 9
341.0
360.0
361.0
1.5
6.7
2.6
1.4
3.6
2.1
1.0
3.1
1.7
1.3
1.5
2.5
1.0
1.0
1.0
116.7
138.3
112.4
198.4
195.8
171.6
181.7
98.1
80.0
46.7
87.5
132.4
130.0
240.0
80.0
a"-11 indicates no data.
-------
Table 23. (Continued) Kirameter means — Lake Huron, 1985.
Survey/layer
Winter-1
Epdlimnion
Winter-2
Epilimnion
Spring
Epiliimion
Sumner
E£>ilimnicn
Mssolimnion
Hypolimnion
Nepheloid
Rall-1
Epilimnion
Mssolimnion
Hypolimnion
Nspheloid
Eall-2
Epilimnion
Winter-1
Epilimnion
Winter-2
Epllimnion.
Spring
Epilimnion
Summer
Epdlimnion
I^fesolimnion
Hypolimnion
Nepneloid
Fall-1
Epalimnion
Mssolimnion
HvpDlimnion
N=pheloid
Fall-2
Epilimnion
I^soliimian
Hypolimnion
Ixfepheloid
Dissolved
reactive pH
silicon
(ug/L)
Alkalinity
(mg/L)
Specific Dissolved
Conductance Oxygen Cl~ SO42~ Ca2+ Mg2"1" Na+ K+
(uS/oti) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L)
Aerobic
Heterotroph
(count/mL)
Northern Basin
768.8
801.3
772.8
421.7
495.9
684.7
976.6
631.7
800.3
958.1
1032.0
747.0
8.03
7.96
8.00
8.42
8.42
8.13
7.98
8.09
7.96
7.90
7.85
7.95
78.6
77.2
76.5
75.1
75.6
76.2
76.6
76.1
76.3
76.1
76.2
76.4
206.5
202.6
202.7
198.9
201.0
204.4
204.8
205.0
205.8
205.8
205.5
201.9
13.2
13.3
13.4
9.8
12.3
12.6
11.9
11.3
11.7
11.9
12.0
12.5
5.3
5.6
5.4
5.2
5.2
5.3
5.4
5.2
5.2
5.2
5.2
5.4
16.0 - -
16.1 - -
15.9 - -
15.7 26.2 7.1 3.3 0.87
15.9 - -
16.0 - -
16.1 26.9 7.3 3.4 0.89
15.8 -
15.8 -
15.8 -
15.7 -
16.7 - - -
—
-
1.4
12.6
—
9.8
8.2
5.2
—
25.4
9.7
—
Southern Basin
712.8
798.7
782.4
338.2
479.4
766.7
1061.9
716.2
971.7
1074.0
1110.0
740.7
944.0
1104.0
1138.0
8.08
7.91
8.03
8.44
8.30
8.01
7.85
8.07
7.83
7.77
7.76
8.01
7.89
7.75
7.74
78.6
78.4
77.6
77.6
77.2
76.6
76.6
76.5
76.5
76.0
76.2
77.3
78.0
78.8
78.0
206.0
205.2
203.4
206.5
207.0
205.9
206.8
207.0
207.0
207.3
207.6
204.4
200.0
206.5
205.3
12.4
13.6
13.5
9.4
11.4
11.8
10.9
11.2
11.0
10.9
11.0
10.8
10.2
11.0
9.8
5.3
5.7
5.4
5.6
5.6
5.5
5.5
5.4
5.3
5.3
5.2
5.4
5.5
5.4
5.5
15.9 - - - -
16.5 - - - -
15.7 - - - -
16.1 27.8 7.4 3.6 0.90
16.0 - -
15.8 - -
16.0 27.4 7.4 3.5 0.90
16.3 - - - -
16.1 - - - -
16.1 - - -
15.8 - - - -
16.6 - - - -
15.6 - - - -
15.9 - _ _
15.6 - -
-
—
3.1
29.5
—
27.5
27.0
9.8
~
4.5
7.7
—
~
—
10
ro
a"-" indicates no data.
-------
Table 24. Parameter means by basin, survey, and layer — Late Erie, 1985.
Chloro-
Survey/layer Tarperature Turbidity ptyll-a
(°c) (Fan
Winter-1
Efctilirrnicn
Winter -2
EJpilirrnicn
faring
Qsilinnicn.
rfesoliimicn
ffypoliimicn
Nepteloid
Sonrer
Epiliimicn
Rail
Efaliimicn.
Winter-1
Efiliimioa
Winter-2
EJpiliirnicn
firing
QDilirmionb
EpilinnicrP
tfesolinnicn
Ifypoliimiai
JSfepheloid
aimer
Ejpiliimicn
rfesoliimicn
Hypoliimicn
Nepteloid
Fall
Epilinnicn
Winter-1
Efalinnicn
Winter-2
Epilinnicn
faring
EJpiliirnicn
aimer
EJpilirrnicn
Mesoliimicn
Hypoliimicn
Nepheloid
Fall
Efciltanicn
0.0
0.0
12.0
11.0
8.4
7.2
22.5
7.0
2.0
0.0
4.6
6.6
5.8
4.2
4.0
22.2
18.7
15.3
14.1
10.6
3.5
0.0
2.1
21.8
13.8
5.8
5.7
10.4
a
-
6.39
6.81
6.51
6.92
4.17
12.02
-
-
1.85
1.46
1.54
1.55
2.44
0.42
0.72
1.77
1.58
2.37
-
-
2.63
0.48
0.61
1.59
1.92
4.10
3.49
2.14
5.85
2.95
4.26
1.73
10.84
1.72
4.57
2.47
2.82
2.52
2.92
1.32
2.96
3.16
3.56
2.70
0.50
2.62
1.92
1.06
0.40
1.39
1.22
0.37
0.30
0.82
Tbtal
Total dissolved
Rieophytin HnsfiTorus Hnsphorus
(ug/L) (ug/L) (ug/L)
0.81
0.12
0.31
0.25
0.35
0.07
2.95
0.84
2.56
0.08
0.04
0.02
0.15
0.06
0.34
0.93
1.15
1.02
0.50
0.57
0.47
0.12
0.07
0.61
0.60
0.47
0.49
0.35
Western Basin
16.8
8.2
20.7
19.8
19.4
22.3
17.9
32.6
Central Basin
42.9
9.5
13.0
11.8
15.0
13.2
17.0
8.8
15.7
42.2
55.1
21.4
Eastern Basin
16.4
11.6
12.8
5.7
5.3
7.1
7.5
15.3
4.0
-
3.9
3.4
3.9
5.1
4.2
6.9
7.5
-
3.8
3.7
3.8
3.0
3.4
3.7
6.7
21.5
33.0
9.9
8.4
-
6.1
2.3
2.1
2.5
3.4
6.6
Grtho
HTOSftcrus
2.0
1.6
1.0
1.0
1.5
2.1
1.6
3.7
5.6
1.4
0.9
0.9
2.0
0.8
1.2
1.1
3.8
23.7
29.5
4.9
3.6
2.6
2.7
1.1
1.4
2.5
2.8
3.1
Nitrogen
(ug/L)
511.5
457.5
698.7
708.0
767.1
766.7
181.4
432.7
217.2
221.2
206.4
197.7
220.5
230.0
222.5
192.3
208.0
203.1
97.0
128.2
262.7
274.5
287.6
185.2
300.7
346.1
349.2
204.5
Total
r«3 Kjeldahl
Nitrogen Nitrogen
(ug/L) (ug/L)
64.5
14.5
20.5
22.5
54.3
43.7
27.4
37.9
5.8
1.0
3.2
3.5
2.8
5.0
7.3
14.0
30.9
46.7
107.0
17.9
6.0
0.5
6.9
6.6
8.2
11.2
14.5
11.5
71.7
203.3
183.6
142.5
214.0
150.0
350.1
253.9
150.0
147.5
143.6
115.4
100.0
135.0
135.0
299.7
313.7
344.6
320.0
230.2
156.7
127.5
121.7
278.6
169.7
214.0
240.3
178.8
3"-" indicates no data.
klsothermal sites
cStratif iea aitjes
-------
liable 24. (Continued) Parameter means — Lake Erie 1985.
Survey/layer
Winter-1
Epilinnion
Winter-2
Epilirmion
Spring
Epilimion
Mssolinnian
Hypolirtnion
Nepheloid
Sumner
Epilimriion
Fall
Epilimnion
Winter-1
Epilinnicn
Winter-2
Epilinnicn
Spring
Epilinnicn
Mssolinnion
Hypolirrmon
Nepheloid
Sumner
Epilirmicn
lyfesolimian
Hypoliimian
Nspteloid
Fall
Epilimnicn
Winter-1
Epilimnion
Winter-2
Epilinnicn
Spring
Epilimnicn
Sunnier
Epilinnicn
tfesoliimian
Hypoliimian
Nepheloid
EDiliinnian
Dissolved
reactive fH Alkalinity
silicon (ng/L)
(ug/L)
Specific Dissolved
Conductance Oxygen Cl~
(us/on) (mg/L) (mg/L)
Western Basin
710.3
637.7
633.1
679.2
688.2
744.0
329.4
743.4
7.95
8.21
8.30
8.19
8.13
8.10
8.54
8.09
87.0
85.8
86.4
85.5
85.4
86.3
82.8
83.6
260.2
263.8
256.1
250.9
254.2
258.2
234.0
244.6
13.6
14.3
11.7
11.6
11.4
11.7
8.0
10.9
14.0
11.3
13.1
12.0
13.1
13.4
9.5
10.8
S042 Ca2+ Mg2"1" Na+ K+
(mg/L) (mg/L) (mg/L) (mg/L) (mg/L)
a
21.0 - - - -
19.0 - - -
20.4 - - -
19.5 - -
19.7 - - - -
19.8 - -
18.9 29.9 8.1 6.0 1.2
18.5 - - -
?erobic
Hsterotroph
(count/mL)
-
-
366.6
699.5
-
613.3
453.3
10148
Central Basin
75.2
36.0
9.0
12.0
12.5
9.6
30.5
139.8
601.2
1572.1
1360.0
78.8
8.15
-
8.21
8.31
8.20
8.15
8.05
8.55
8.11
7.62
7.53
8.19
97.0
96.6
93.4
93.1
93.1
92.6
93.0
92.2
93.2
96.4
100.0
92.1
290.8
283.8
276.2
277.5
277.6
276.9
278.3
275.4
279.2
284.6
290.0
278.5
12.8
14.0
13.2
12.7
12.3
12.0
12.0
8.3
5.3
1.4
0.2
9.9
17.5
13.4
14.6
14.8
14.9
14.6
14.9
14.7
14.6
14.5
14.6
14.7
25.4 - - - -
23.7 - - - -
23.6 - - -
22.7 - - -
22.7 - - -
22.5 - - - -
22.8 - - -
22.7 35.0 8.4 8.6 1.3
22.6 34.0 8.4 8.6 1.3
22.5 35.8 8.4 8.5 1.4
23.7 37.0 8.4 8.5 1.4
90 1
Z. J . J. —
9.1
7.5
19.0
13.5
13.7
105.8
-
119.6
-
91.7
Eastern Basin
62.3
67.8
71.5
75.5
145.5
303.3
340.6
90.4
8.19
7.97
7.93
8.55
7.96
7.91
7.91
8.10
99.5
98.2
92.4
92.5
93.4
94.2
94.6
94.2
290.0
289.0
278.2
280.2
284.9
286.6
287.0
283.5
13.3
13.4
12.9
8.9
7.9
10.1
9.7
9.4
16.5
15.2
14.9
15.0
14.9
14.8
14.9
14.6
25.8 - - - -
23.8 - - -
23.2 - - -
23.0 35.5 8.3 8.9 1.3
22.7 - - - -
23.3 - -
22.9 36.9 8.3 8.8 1.4
23.2 - - -
-
-
62.8
173.9
-
140.0
337.5
89.2
a"-" indicates no data.
-------
Table 25. Parameter means determined fran composited upper 20-meter samples, averaged by survey and basin- Lates
Michigan, Hurcn and Erie, 1985.
Chloro-
Survey/basin ptyll-a
(ug/L)
faring
late Michigan
South
North
Late Huron
North
South
late Erie
West
Central
East
Sunnier
late Michigan
South
North
Late Hurcn
North
South
Late Erie
West
Central
East
Eall-1
Late Michigan
South
North
Late Huron
North
South
Eall-2
Late Michigan
South
North
Late Huron
South
North
EaJ.1 1/2
Late Erie
Wast
Central
East
1.00
0.63
0.77
0.94
4.83
2.60
0.45
1.07
1.05
0.96
1.52
10.05
3.35
1.40
0.65
0.68
0.57
0.55
0.33
0.36
0.36
0.46
2.02
2.55
0.72
Pheophytin
(ug/L)
0.03
0.07
-0.01
-0.01
0.35
0.02
0.07
0.25
0.17
0.16
0.10
3.20
0.93
0.55
0.20
0.22
0.10
0.12
0.08
0.10
0.12
0.10
0.78
0.54
0.56
Total Dissolved Total Dissolved
Total Dissolved ortho- rt>2 + ND3 1SH3 Kjeldahl Reactive
Phosphorus Phosphorus Phosphorus Nitrogen Nitrogen Nitrogen Silicon Cl
(ugA) (ug/L) (ug/L) (ug/L) (ugA) (ug/L) (ug/L) (mg/L)
4.7
4.4
3.9
3.0
19.5
12.0
12.7
3.0
3.9
2.2
3.0
18.3
11.5
7.0
3.9
2.5
2.9
3.1
5.2
4.8
3.5
3.4
37.2
21.4
12.5
2.1
2.2
1.4
1.1
4.0
3.9
6.6
1.6
1.8
1.2
1.0
5.6
5.6
3.7
1.7
2.0
1.4
0.8
2.5
2.8
1.0
1.7
7.4
9.9
6.4
0.7
0.6
0.6
0.4
1.2
1.0
2.5
0.2
0.5
0.2
0.4
2.7
1.8
1.1
0.3
-0.3
-0.1
0.7
0.0
0.4
-0.3
-0.3
4.4
5.0
3.3
285.3
282.4
300.9
302.7
690.8
210.6
278.9
165.1
161.3
273.0
278.3
193.6
201.2
191.9
240.3
221.4
302.7
325.7
294.0
239.4
294.4
294.0
423.7
129.7
207.5
2.5
1.7
2.2
3.2
28.0
3.2
6.4
3.5
3.9
2.1
2.1
26.2
18.5
7.6
2.9
1.8
3.2
3.5
1.3
1.8
2.6
3.0
50.0
18.1
10.4
108.3
82.0
100.9
111.0
163.3
133.9
118.7
185.0
168.7
135.9
250.0
352.9
290.8
362.5
200.0
72.0
68.3
95.0
93.3
32.0
138.0
156.0
255.0
243.5
146.2
564.2
538.3
771.8
776.7
652.7
9.0
65.8
104.1
98.9
446.1
358.0
347.9
244.5
85.9
376.2
321.6
626.5
821.0
594.8
397.4
693.0
733.4
734.8
81.6
100.8
8.67
8.84
5.37
5.33
12.8
14.7
14.8
8.74
8.50
5.29
5.62
9.36
14.6
14.9
9.02
8.58
5.20
5.40
8.70
8.94
5.38
5.54
11.1
14.7
14.6
ao4
(mg/L)
21.9
22.4
15.9
15.8
20.0
23.3
23.0
21.7
21.7
15.8
16.1
18.6
22.7
23.2
22.0
21.5
15.5
16.0
22.8
21.7
16.1
16.0
18.5
22.7
22.8
VO
in
-------
96
The composite samples provide a means of checking other data taken
within the epiliinnion. Scatter plots of parameter concentrations
determined from the composite samples at each station versus the average
of the concentrations determined from the discrete samples at master
stations (or surface samples at regular stations) show that the general
agreement between the two is quite good (Figures 33 to 42). Parameters
with digestion procedures or ambient concentrations near the criterion of
detection (e.g., total P, total dissolved P, TKN, or dissolved ortho
phosphorus) show the highest scatter. The scatter, however, does not
appear to be biased qualitatively indicating that surface samples and
epiliinnion averages are indeed representative of the upper 20 meters of
the water column. The results reflect the homogeneity of the upper water
column during the three survey periods (early spring, stable summer
stratified, and fall overturn).
CO^EMTRATTON OF MAJOR IONS - ION BALANCES
Concentrations of the major anions (Cl~, S04=, and CO3= + HC03~ as
CaC03 equivalent alkalinity) were determined at every sample depth during
each of the 1985 water quality surveys. Concentrations of the major
cations (Ca++, Mg++, Na+, and K*") were determined at selected depths
during the summer survey. Results (Tables 26 and 27) show little
variation in the anion concentration within basins with either depth or
time. Although basin differences within lakes are generally small, the
three lakes are easily differentiated by both the absolute concentrations
and the stoichiometric ratios of the major ions. Lake Huron has low
concentrations of dissolved solids, while Lakes Michigan and Erie have
relatively higher concentrations. Lake Michigan, however, has higher
alkalinity and lower concentrations of sodium and chloride than Lake Erie.
Basin-average epiliinnion concentrations of the major ions measured
during survey 2 are listed in Table 26. The converted milliequivalent
concentrations of these values are listed in Table 27, along with
approximate ion balances for each basin. There is an excess of cations as
in 1983, but this excess is generally less than 5 percent in all
basins.
-------
97
25
20-
15H
10-
CHLOROPHYLL-A
A '
10
15
20
25
SAMPLE AVERAGE (/*gA) UPPER 20 m
Figure 33. Comparison of average chlorophyll-a concentrations determined
from discrete epilimnion sanples with those determined from
the composite 20-meter sample - all lakes, all surveys, 1985.
0 10 20 30 40 50 60
SAMPLE AVERAGE (/*gA) UPPER 20 m
Figure 34. Comparison of average total phosphorus concentrations
determined from discrete epilimnion sanples with those
determined from the conposite 20-meter sample - all lakes, all
surveys, 1985.
-------
98
16
CT>
C/>
a:
Lul
12-
8-
O
CM
UJ
w 4
O
CL
O
O
TOTAL DISSOLVED P
A ,'
0 4 8 12 16
SAMPLE AVERAGE (/zg/L) UPPER 20 m
Figure 35.
Comparison of average total dissolved phosphorus
concentrations determined from discrete epilimnion samples
with those determined from the composite 20-meter sample - all
lakes, all surveys, 1985.
Figure 36.
SAMPLE AVERAGE (/xg/L) UPPER 20 m
Comparison of average dissolved ortho phosphorus
concentrations determined from discrete epilimnion samples
with those determined from the composite 20-meter sample - all
lakes, all surveys, 1985.
-------
99
Ld
_i
Q.
<
CO 0.6
Qi
O
CN
UI
0.4-
8 0.2
Q.
2
O
O
DISSOLVED NITRATE+NITRITE N
0 0.2 0.4 0.$ 0.8 1
SAMPLE AVERAGE (mg/L) UPPER 20 m
Figure 37. Comparison of average dissolved nitrate + nitrite nitrogen
concentrations determined from discrete epilimnion samples
with those determined from the composite 20-meter sample - all
lakes, all surveys, 1985.
0>
,§
LU
a!
0.8-
CO 0.6-
o
CN
LU
I 0.2
CL
O
C_>
0-
TOTAL KJELDAHL N
A
A
Ax
A A
0 0.2 0.4 0.6 0.8 1
SAMPLE AVERAGE (mg/L) UPPER 20 m
Figure 38. Comparison of average total Kjeldahl nitrogen concentrations
determined from discrete epilimnion samples with those
determined from the composite 20-meter sample - all lakes, all
surveys, 1985.
-------
100
0.20
o>
CO
o;
o.ioH
TOTAL AMMONIA N
0.00
0.00
0.05 0.10 0.15 0.20
SAMPLE AVERAGE (mg/L) UPPER 20 m
Figure 39. Comparison of average total ammonia nitrogen concentrations
determined from discrete epiliimion samples with those
determined from the composite 20-meter sample - all lakes, all
surveys, 1985.
1.2
o>
LJ
0.8-
0.6-
0
CN 0.4-
Ul
2 0.2-
o
o
0.0
DISSOLVED REACTIVE SILICA (SiO,)
0.0 0.2 0.4 0.6 0.8 1.0
SAMPLE AVERAGE (mg/L) UPPER 20 m
1.2
Figure 40. Comparison of average dissolved reactive silica concentrations
determined from discrete epilimnion samples with those
determined from the composite 20-meter sample - all lakes, all
surveys, 1985.
-------
101
20
15-
10-
cn
E
Q_
2
(f>
o
CM
— 5-
O
D.
O
O
CHLORIDE
t
X
0 5 10 15
SAMPLE AVERAGE (mg/L) UPPER 20 m
20
Figure 41. Comparison of average chloride concentrations determined from
discrete epilimnion samples with those determined from the
composite 20-meter sample - all lakes, all surveys, 1985.
30
to
QL
LJ
O
CM
O
0.
2
O
O
25-
20-
10
SULFATE
10 15 20 25 30
SAMPLE AVERAGE (mg/L) UPPER 20 m
Figure 42. Comparison of average sulfate concentrations determined from
discrete epilimnion samples with those determined from the
composite 20-meter sample - all lakes, all surveys, 1985.
-------
102
Table 26. Absolute concentrations (mg/1) of major ions in the
epilimnion — summer survey, 1985.
Basin Alk. Cl~ S04~ Ca++ Mg++ Na+ K+
Lake
Lake
Lake
Michigan
South
North
Huron
North
South
Erie
West
Central
East
108
108
75
77
82
92
92
.13
.04
.09
.58
.78
.24
.52
8.82
8.56
5.23
5.63
9.53
14.67
15.01
21
21
15
16
18
22
23
.71
.58
.74
.08
.88
.68
.05
36.
35.
26.
27.
29.
34.
35.
00
20
25
77
94
97
50
11.17
11.00
7.10
7.38
8.06
8.36
8.35
5.46
5.37
3.34
3.57
6.04
8.64
8.90
1.23
1.21
0.87
0.90
1.18
1.33
1.35
SECCHI DEPTH BY BASIN AND SURVEY
Secchi disc measurements could not be obtained at all stations due to
the 24-hour-a-day operation; however, sufficient data were obtained to
permit calculation of representative basin averages (Table 28). Secchi
depths generally followed the expected pattern of increasing during the
summer when the epilimnion was depleted of nutrients and particulates.
Only in Lake Erie were the spring to sumner changes significant
(alphaO.05).
-------
Table 27. Stoichianetric concentrations (niilliequivalent/L) of major ions in the epilirtnion — sinner survey, 1985.
Basin
Late Michigan
South
North
Late Huron
North
South
Late Erie
West
Central
East
Number of
Sanples
an— cat-
ions1 ions2
43
33
36
29
21
83
25
18
15
16
13
16
29
8
003-
2.16
2.16
1.50
1.55
1.66
1.84
1.85
cr
0.25
0.24
0.15
0.16
0.27
0.41
0.42
S04~
0.45
0.45
0.33
0.33
0.39
0.47
0.48
CE++
1.80
1.76
1.31
1.39
1.49
1.75
1.77
^++
0.92
0.91
0.58
0.61
0.66
0.69
0.69
Na+
0.24
0.23
0.15
0.16
0.26
0.38
0.39
K+
0.03
0.03
0.02
0.02
0.03
0.03
0.03
Ibtal
anions
2.86
2.85
1.98
2.05
2.32
2.73
2.75
Ibtal
cations
2.98
2.93
2.06
2.17
2.45
2.84
2.88
Ratio:
anions
cations
0.96
0.97
0.96
0.94
0.95
0.96
0.96
1anion samples were collected at all depths.
2cation sanples were collected at selected depths.
o
oo
-------
Table 28. Secchi depths (meters) averaged by basin and survey, 1985.a
Helicopter Helicopter Helicopter Survey Fall 1 & 2
Basin January February Average faring Sunnier Fall 1 Fall 2 Average
L. Michigan
Sooth _b _ - 10.2+2.1 (6) 8.4+2.5 (7) 10.0+1.4 (2) 9.2+0.4 (2) 9.6+1.0 (4)
North - 13.8+2.5 (2) 13.8+2.5 (2) 11.6+1.7 (8) 10.8+3.0 (10) 11.0+1.1 (2) 13.2+3.2 (2) 12.1+2.4 (4)
L. Huron
North 12.5+3.5 (2) 12.3+1.0 (3) 12.4+1.9 (5) 11.1+0.9 (7) 12.7+2.7 (11) 11.7+0.6 (3) 9.2+0.4 (2) 10.7+1.4 (5)
South - 11.3+0.8 (3) 11.3+0.8 (3) 9.3+1.3 (9) 10.9+1.2 (5) -
L. Erie
West 1.1+0.1 (3) - 1.1+0.1 (3) 1.6+0.4 (6) -
Central - 3.4+0.8 (7) 7.4+1.0 (12) - - 3.0+0.5 (9)
East 3 (1) 2 (1) 2.5+0.7 (2) 2.4+0.1 (2) 9.2+1.1 (2) - - 3.3+1.5 (6)
a Secchi depths average + one standard deviation. The number of sanples is shewn in parentheses.
b "-" indicates no data.
-------
105
DISCUSSICN
TROPHIC STATUS
Dobson et al. (1974) published a simple indexing system based on a
limited number of water quality variables to classify areas within the
Great Lakes in terms of their trophic status. In this system, Secchi
depth, concentration of chlorophyll-a, and concentration of particulate
phosphorus are used to classify a lake as oligotrophic, mesotrophic, or
eutrophic. Since each of these variables is dynamic, the relationship
between the values of the variables and the classification limits may
change during the year. Thus, classification is still subjective;
however, this simple system provides a convenient method of expressing
the trophic status of a lake. The classification limits used by Dobson
et al. (1974) are shown in Table 29, along with three other
classification schemes. Two of the other systems are based on Secchi
depth and nutrient concentrations made at the surface (Rast and Lee,
1978; International Joint Commission, 1976a); the third is based on the
number of aerobic heterotrophs in the water (Rockwell et al., 1980).
Table 29. Classification limits for trophic status.
System/parameter
Oligotrophic Mesotrophic Eutrophic
Dobson et al. (1974)
Chlorophyll-a (ug/L)
Particulate P (ug/L)
Secchi Depth (m)
30/Secchi Depth (m"1)
Rast and Lee (1978)
Chlorophyll-a (ug/L)
Total Phosphorus (ug/L)
Secchi Depth (m)
<4.4
<5.9
>6.0
<5.0
<2.0
<10.0
>4.6
International Joint Commission (I976a)
Chlorophyll-a (ug/L) <2.4
Total Phosphorus (ug/L) <6.6
Secchi Depth (m) >8.6
Rockwell et al. (1980)
Aerobic heterotrophs (number/mL)
<20
4.4 to 8.8 >8.8
5.9 to 11.8 >11.8
6.0 to 3.0 <3.0
5.0 to 10.0 >10.0
2.0 to 6.0 >6.0
10.0 to 20.0 >20.0
4.6 to 2.7 <2.7
2.4 to 7.8 >7.8
6.5 to 14.1 >14.1
8.6 to 2.9 <2.9
20 to 200 >200
-------
106
Observed basin- and survey-averaged values for these index parameters
are listed in Table 30. The observed values are plotted along with Dobson
et al's. classification limits in Figures 43, 44 and 46, the International
Joint Commission's in Figure 45, and Rockwell et al.'s in Figure 47. The
Fall survey was divided into two runs for Lake Michigan and Lake Huron
only (see Temporal Variation Within Surveys section).
The open waters of Lakes Michigan and Huron satisfied almost all of
the criteria for oligotrophy during the 1985 surveys. Only in Lake Erie
were the eutrophic criteria exceeded, and then primarily in the shallow
western basin. The total phosphorus eutrophic criteria was exceeded in
all the basins of Lake Erie in the fall. The eutrophic criteria based on
chlorophyll-a concentration, however, was reached only during the summer
in western Lake Erie. This may be because of the time lag required to
convert soluble nutrients into particulate biomass or because sampling was
restricted to open-lake waters, which are expected to be less productive
than nearshore areas.
Within-year patterns of the indexing parameters are similar in the
three lakes, except in Lake Michigan. Secchi depth was greatest during
the summer in all basins, except in Lake Michigan (Table 30). As
expected, total and particulate phosphorous concentrations were relatively
low during the summer, except in northern Lake Michigan. The 1985 summer
chlorophyll levels were the highest sampled in all basins in the summer
and lowest in the fall. This pattern may be an artifact of the survey
timing; the spring surveys were conducted before active phytoplankton
growth, and the fall surveys were conducted when the epilimnion had mixed
to great depths in Lakes Michigan and Huron and after autumn turnover in
Lake Erie. As a result, the spring surveys probably are representative of
pre-spring bloom conditions and the fall survey is representative of the
post-fall bloom conditions.
The classification system presented by Rockwell et al. (1980) is
different from the others considering that it is based on the number of
aerobic heterotrophs in the water rather than on nutrient concentrations.
-------
107
Table 30. Survey and basin mean values — water quality index classification
parameters, 1985.a
Basin Chlorophyll-a
(mg/L)
Lake Michigan
South
North
Lake Huron
North
South
Lake Erie
West
Central
East
No Samples
No Samples
0.94
0.80
3.09
4.59
1.85
Total Particulate Secci 30/Secchi
Phosphorus Phosphorus Depth Depth
(ug/L) (ug/L) (m) (m)
Winter-1 (January, 1985)
Collected
Collected
3.1
5.4
17.0
42.2
18.2
0.8
1.9
12.9
35.5
9.9
Winter-2 (February,
Lake Michigan
South
North
Lake Huron
North
South
Lake Erie
West
Central
East
Lake Michigan
South
North
Lake Huron
North
South
Lake Erie
West
Central
East
0.90
0.98
0.90
1.30
2.14
2.64
0.96
0.98
0.67
0.76
1.04
6.22
2.92
0.44
5.7
6.0
3.0
6.7
7.9
9.0
11.3
Spring
4.8
5.6
3.1
2.9
21.0
12.1
13.0
1.4
1.7
0.6
4.7
—
—
-
(April, 1985)
2.3
2.7
1.6
1.7
17.3
8.1
6.5
12.5
-t>
1.1
-
3.0
1985)
—
13.8
12.3
11.3
—
—
2.0
10.2
11.6
11.1
9.3
1.6
3.4
2.4
2.5
—
26.7
—
10.0
—
2.22
2.44
2.65
_
—
15.0
3.02
2.65
2.72
3.30
19.2
9.45
12.5
Concentration values from the surface (1 meter depth) samples.
b II_H indicates no data.
-------
108
Table 30. (Continued) Survey and basin mean values — water quality
index classification parameters, 1985.a
Total
Chlorophyll-a Phosphorus
(mg/L) (ug/L)
Particulate Secchi 30/Secchi
Phosphorus Depth Depth
(ug/L) to) (m-1)
Summer (August, 1985)
Lake Michigan
South
North
Lake Huron
North
South
Lake Erie
West
Central
East
1.05
0.98
0.80
1.25
10.6
3.17
1.31
2.5
4.3
2.8
2.2
18.3
8.6
5.5
1.1
2.6
0.8
1.0
14.1
5.1
3.2
8.4
10.7
12.7
10.9
_b
7.4
9.2
3.90
3.10
2.45
2.78
-
4.12
3.26
Fall-1 (November, 1985)
Lake Michigan
South
North
Lake Huron
North
South
0.68
0.87
0.63
0.68
3.7
3.3
2.8
3.4
1.2
1.2
1.5
2.7
10.0
11.0
11.7
—
3.03
2.75
2.58
—
Fall-2 (November-December, 1985)
Lake Michigan
South
North
Lake Huron
North
South
Lake Erie
West
Central
East
0.38
0.34
0.34
0.42
1.67
2.66
0.76
5.1
4.2
2.9
3.8
Fall 1 and 2
32.5
21.0
12.5
2.4
1.2
2.0
1.8
(November ,
25.4
11.2
5.9 .
9.2
13.2
9.2
—
1985)
-
3.0
3.3
3.25
2.33
3.25
—
-
10.2
11.4
Concentration values from the surface (1 meter depth) samples.
bn_ii indicates no data.
-------
109
12
10
o
I
Q_
§ ^
3
5 2
Eutrophic
Mesotrophic
Oligotrophic
Legend
EZ3 Spring
•I Summer
E3 Fall 1
CH Fall 2
S-LM N-LM N-LH S-LH W-LE C-LE E-LE
aFall-l and Fall-2 surveys are combined for Lake Erie.
Figure 43. Basin average 1985 values of chlorophyll-a in the surface
waters conpared with Dobson's (1974) water quality index.
PARTICULATE PHOSPHORUS (/xg/L)
_• _, N5 NJ O.
D in o in o in c
Eutrophic
Mesotrophic
Fbrfl P*n adl a^h
X
/
/
(
X
\
s
^
3
Legend
7Z\ Spring
•1 Summer
C3 Fall 1
CH Fall 2
a
J
/M\
1
3
S-LM N-LM N-LH S-LH W-LE C-LE E-LE
aFall-l and Fall-2 surveys are combined for Lake Erie.
Figure 44. Basin average 1985 values of particulate phosphorus in the
surface waters conpared with Dobson's (1974) water quality
index.
-------
110
TOTAL PHOSPHORUS (^g/L)
-* K> OJ 4
O O O O C
Eutrophic
Mesotrophic
^W^n^fi
/
^
/
^
\
Q
1
Legend
23 Spring
•1 Summer
C3 Fall 1
d] Fall 2
^
^
s
i\
/^l
a
a
n
R,
'xU^
S-LM N-LM N-LH S-LH W-LE C-LE E-LE
Figure 45.
aFall-l and Fall-2 surveys are combined for Lake Erie.
Basin average 1985 values of total phosphorus in the surface
waters compared with the International Joint Commission's
(1976a) water quality index.
20
D_
UJ
IE
O
O
LJ
15
10
Eutrophic
Mesotrophic
I
S-LM N-LM N-LH S-LH W-LE C-LE E-LE
aFall-l and Fall-2 surveys are combined for Lake Erie.
Figure 46. Basin average 1985 values of 30/Secchi depth compared with
Dobson's (1974) water quality index. See Figure 45. for the
legend.
-------
Ill
CO
X
Q_
O
O
UJ
I
O
CO
O
Od
LJ
200
150
100
50
Eutrophic
Mesotrophic
++
S-LM N-LM N-LH S-LH W-LE C-LE E-LE
aFall-l and Fall-2 surveys are combined for Lake Erie.
Figure 47. Basin geometrical mean 1985 values of aerobic heterotrophs in
the surface waters compared with Rockwell's (1980) water
quality index. See Figure 45. for the legend. (+ value is
1423; ++ value is 810; and +++ value is 3165.)
Ecrpirically derived from data collected in 1977 on Lake Michigan, this
system uses the geometric mean of the aerobic heterotroph count as the
classification criterion. These values are listed in Table 31 along with
survey statistics for each basin. In the spring, the classification
based on this bacteriological criterion is similar to that based on
nutrient concentrations. In contrast, this bacteriological criteria
indicated mesotrophic conditions in Lake Michigan and southern basin Lake
Huron. Observed bacteria counts were the highest during the summer in
Lake Michigan, Lake Huron, and the central and eastern basins of Lake
Erie, while western Lake Erie had maximum levels during the fall survey.
These seasonal changes may reflect a larger available particulate
substrate during the summer.
COMPARISON WITH 1983 AND 1984 SURVEY RESULTS
One of the major objectives of the annual surveillance program is to
collect data sufficient for the evaluation of water-quality trends. The
-------
Table 31. Aerobic heterotrophs (count per niL) in surface sanples collected during the 1985 surveillance program.a
Snrincr— 1
Basin
Late Michigan
South
North
Late Huron
North
South
Late Erie
West
Central
East
Min.
1
1
1
1
98
5
7
Max.
3
2
4
6
6000
21
140
Madian
1
1
1
2.5
4900
8.5
53
Gecm.
mean
1.4
1.1
1.4
2.4
1423
8.8
40.6
Min.
15
26
0.9
4
810
37
75
Suraner-1
Max..
64
150
12
63
810
200
300
Median
32
100
5
32.5
810
59
160
Geom.
mean
33.4
80.0
4.4
21.3
810
76.8
153.3
Min.
8
8
3
3
220
34
42
Max.
45
64
8
16
27200
180
140
Fall-1
Median
33
11
4.5
7.5
5300
83
62
Geom.
mean
22.7
17.9
4.4
7.0
3165
84
69
All data
Gecm.
mean
9.6
11.8
2.9
7.1
-
1849
40
71
m. = mininum; Max. = maxirnm; Geom. = geometric
-------
113
term "trend" iirplies a change in the concentration of a specified water
quality parameter over time. Trends may be indicative of either
inproving or degrading water quality, and changes in trends may provide
information about the efficiency of remedial control programs or other
environmental variations.
Since trends are usually established by comparison across data sets
that often were collected years apart by different agencies using
different techniques, it is important to avoid invalid comparisons. An
annual average, for example, cannot be compared with a seasonal average
for the purpose of establishing a temporal trend, and likewise it would be
inappropriate to compare nearshore data collected one year with open-
lake data collected in another. Therefore, any comparison involving data
collected for different purposes and at different times must be conducted
with extreme care.
As previously mentioned, the GLNPO surveillance program, begun in
1983 was designed to sample only the open waters of the three lakes.
Nearshore areas were specifically excluded. This sampling design was
based on the assumption that the open waters are relatively homogenous
and, therefore, representative sample statistics could be calculated from
a reduced set of sampling locations.
This hypothesis was tested (Lesht and Rockwell, 1985) using the more
extensive survey data collected in Lake Michigan in 1976-1977 and in Lake
Huron in 1971 and 1980. The test consisted of comparing concentration
averages based on all open-lake stations similar to those sampled in 1983.
This analysis was conducted for the means of surface samples taken during
the well-mixed spring period. The results showed that the same subset of
stations chosen for sampling in 1983 and 1984 was representative of open-
lake conditions (as defined by the more extensive data sets), in those
earlier years when the comparison could be made.
Another Lake Michigan test was done comparing the concentration
averages based on all open-lake stations with concentration averages based
-------
114
on data collected at a subset of stations similar to those sampled in!985.
This analysis was conducted for the means of surface samples taken during
the well-mixed spring period. The results, listed in Table 32, show that
the subset of stations chosen for sampling in 1985 was representative of
open-lake conditions in each earlier year where the comparison was made.
A Lake Erie test was also undertaken comparing the 1985 concentration
data from all spring central and eastern basin open-lake stations with
1985 concentration data from the subset of four stations which were also
in the 1983 and 1984 station network. Except for chloride, this analysis
showed (Table 33) no statistically significant differences in the means of
surface samples taken during the well-mixed spring period. The chloride
absolute concentration difference was 0.2 mg/L which is not
environmentally significant. Thus, the additional stations chosen for
sampling in 1985 could be represented by the four stations in the
1983/1984 subset of these sites for the spring of this year. Similar
results are reported by Fay and Rathke (1987) in their analysis of the
1985 Great Lakes open lake water quality data sets for the entire season.
Another measure of the representativeness of the 1985 survey can be
found in comparing the survey frequency. The annual means (Table 45-
1985b) estimated from the three-survey program (USEEA-GLNPO reduced
frequency survey program) can be compared with the annual means (Table 45-
1985c) estimated from the intensive survey program (eight surveys)
recommended by the Lake Erie GLISP. USEEA-GLNPO funded the Center for
Lake Erie Area Research - Ohio University to implement the intensive
program. These annual means differ by only 1.4% in the central basin and
by 9.6% in the eastern basin. Both basin results in the reduced frequency
program are well within the 95% confidence interval associated with the
intensive survey program annual means.
In this section we compare the results of the 1985 surveillance
effort with those obtained in 1983 and 1984. Three years of data may not
be sufficient to establish a trend. This comparison is valuable,
-------
Table 32. Comparison of Lake Michigan spring water quality statistics (mean + standard
deviation) calculated from subsets of stations similar to those sampled in 1983
with all open-lake stations stations using 1976 and 1977 intensive survey data.a
Year/Bas in/Parameter
1976 Southern Basin
Chlorophyll-a (ug/L)
Chloride (mg/L)
Specific conductance (us/cm)
Nitrate + nitrite nitrogen (ug/L)
Total phosphorus (ug/L)
Dissolved reactive silica (mg/L)e
Temperature (°C)
1976 Northern Basin
Chlorophyll-a (ug/L)
Chloride (mg/L)
Specific conductance (us/cm)
Nitrate + nitrite nitrogen (ug/L)
Total phosphorus (ug/L)
Dissolved reactive silica (mg/L)e
Temperature (°C)
1977 Southern Basin
Chlorophyll-a (ug/L)
Chloride (mg/L)
Specific conductance (uS/on)
Nitrate + nitrite nitrogen (ug/L)
Total phosphorus (ug/L)
Dissolved reactive silica (mg/L)e
Temperature (°C)
All
open- lake
stations
(N = 9)
1.81 + 0.90
7.90 + 0.15
272.0 + 1.5
230 + 30
5.2 + 0.9
1.10 + 0.18
7.3 + 1.5
(N = 13)
1.48 + 0.76
7.8 + 0.11
-d
230 + 22
7.3 + 1.44
0.96 + 0.25
3.0 ± 0.4
(N = 9)
1.19 + 0.57
8.2 + 0.19)
275,0 + 2.1
257 + 24
4.6 + 1.8
1.14 + 0.06
2.6 + 0.6
Subset of stations
similar to those
sampled in 1983b
Lake Michigan
(N = 8)
1.48 + 0.96
8.06 + 0.29
272.3 + 1.5
224 ± 32
5.62 + 1.30
0.991 + 0.290
8.8 + 1.7
(N = 6)
1.59 + 0.60
7.83 + 0.082
298.3 + 3.4
233 ± 20
7.83 + 1.72
0.917 + 0.160
2.8 + 0.1
(N = 8)
1.22 + 0.39
8.12 + 0.07
275.0 + 1.4
250 + 15
3.9 ± 0.6
1.12 + 0.09
3.0 + 0.4
Subset of stations
similar to those
sampled in 1985C
(N = 6)
1.75 ± 0.96
7.92 + 0.16
271.7 ± 1.4
230 + 27
5.17 + 0.75
1.09 + 0.21
7.8 + 1.5
(N = 5)
1.10 + 0.25
7.70 + 0.10
298.4 + 3.8
240 + 19
7.60 + 1.52
1.08 + 0.15
3.1 ± 0.2
(N = 6)
1.35 + 0.63
8.17 + 0.19
275.3 + 2.5
258 + 11
5.2 ± 1.9
1.13 + 0.08
2.8 + 0.4
a Table contains mean and standard deviation of spring survey surface samples with number
of samples included in parentheses.
b network defined in Lesht and Rockwell (1985).
c network defined in Table 4.
d "-" data not available.
e Dissolved reactive silica (mg-Si02/L).
-------
Table 33. Comparison of Lake Erie water quality statistics (mean ± standard deviation)
calculated from subsets of stations similar to those sampled during 1983 and
1984 with all open-lake stations using 1985 spring survey data -a
Year/Bas in/Parameter
Spring open-lake
station network
sampled in 1985
Subset of stations
similar to those
sampled in 1983/1984b
1985 Central Basin
Chlorophyll-a (ug/L)
Chloride (mg/L)
Specific Conductance (uS/cm)
Nitrate + nitrite nitrogen (ug/L)
Total phosphorus (ug/L)
Dissolved reactive silica (ug/L)
Turbidity (FTU)
Temperature (°C)
1985 Eastern Basin
Chlorophyll-a (ug/L)
Chloride (mg/L)
Specific Conductance (uS/cm)
Nitrate + nitrite nitrogen (ug/L)
Total phosphorus (ug/L)
Dissolved reactive silica (ug/L)
Turbidity (FTU)
Temperature (°C)
(N = 18)
2.92 + 1.36
14.6 + 0.46
276.2 + 2.9
203 + 25
12.1 + 1.4
7.9 + 3.5
1.60 + 0.53
5.6 + 1.2
(N = 8)
0.44 + 0.25
14.9 + 0.28
76.4 + 1.4
278 + 17
13.0 ± 0.8
67.1 ± 11.2
2.21 + 0.48
2.0 + 0.26
Lake Erie
(N = 8)
3.15 + 1.42
14.4 + 0.17
276.0 + 1.9
213 + 15
12.5 + 1.6
7.6 + 3.5
1.56 ± 0.15
5.6 + 1.1
(N = 4)
0.35 + 0.13
14.9 + 0.31
276.6 + 2.0
280 + 7
13.2 + 0.3
67.5 + 13.9
2.37 + 0.59
1.8 + 0.08
-0.40
2.07C
0.20
-1.13
-0.70
0.21
0.24
-0.20
0.70
0.00
-0.16
-0.19
-0.46
-0.05
-0.51
+1.36
a Table contains mean and standard deviation of spring survey surface samples with number
of samples in parentheses.
b Stations compared in the central basin are LE 42, LE 73, LE 37, and LE 78 (the network in
1983 and 1984 included one more site: LE 79). Stations compared in the eastern basin
are LE 09 and LE 15.
c indicates that the means are statistically different at alpha=0.05.
-------
117
however, as an indication of the annual variability in water quality
measurements when uncertainty due to factors such as sample location,
sample times and analytical technique are minimized.
Thermal Cycle - Sampling Times
The three surveys of 1985 were conducted within a few calendar days
of the surveys of 1984. Both the 1984 and 1985 survey schedule differed
from the 1983 survey schedule in that the fall survey was conducted later
in the year to sample fall "overturn." Lesht and Rockwell (1987)
discussed the effects of the mild, 1982-1983 winter on lake water
temperature. The 1985 spring temperatures were below 3°C, which was
similar to the 1984 spring water temperatures. Similar spring water
temperatures might be expected since the winters of 1983-1984 and 1984-
1985 each had a Great Lakes Winter Severity Index (WSI) (Quinn et al. ,
1978) of -4.9. The winter 1984-1985 value is based on the monthly mean
air temperature data shown in Table 34, where WSI equals the average of
the four monthly mean air temperatures at each of the four stations.
Table 34. Monthly mean air temperature at Great Lakes Winter Severity
Index3 stations in Centigrade (Fahrenheit) - Winter 1984-1985.
_ 1984 _ _ 1985 _
November December January February
Duluth, MM 3.7 (38.6) 1.1 (34.0) -6.4 (20.4) -4.7 (23.5)
Sault Ste. Marie, MI -0.2 (31.7) -6.3 (20.6) -11.2 (11.9) -10.6 (12.9)
Buffalo, NY 2.8 (37.0) 2.0 (35.6) -6.1 (21.1) -4.0 (24.8)
Detroit, MI -2.0 (28.4) -10.4 (13.2) -14.2 (6.5) -11.3 (11.6)
Monthly sum 4.3 -13.6 -37.9 -30.6
Normal monthly sum 7.3 -10.4 -33.9 -28.1
Lakes Winter Severity Index (Quinn et al. , 1978) is the average of
the monthly mean temperatures from November through February at these
four stations. The "normal" value of the index is -4.1 =(7.3-10.4-33.9-
28.1) /1 6, (i.e., the average monthly mean temperature value for these
four cities during the four months).
-------
118
During November, the surface temperatures in all three lakes were
similar in 1983, 1984 and 1985. Figures 48 to 52 show that 1985 spring
survey sampling occured while the surface water temperature was similar to
1984 and one to two degrees cooler than 1983 in Lakes Michigan and Huron.
In contrast, 1985 western basin Lake Erie temperatures were 1 to 6° C
warmer than in 1983 and 1984, respectively. The 1985 lake water column
was vertically more homogeneous than in 1984 (Lesht and Rockwell, 1987),
although there is some sugggestion of residual hypolimnetic (nepheloid)
layer enrichment (Figures 17 and 18). The summer survey of 1985 occurred
during the stable summer stratified period. Although the duration of the
1985 stratified period was compariable to previous years, greater
depletion of silica is evident in all basins of Lakes Michigan and Huron
(Figures 19 to 22, Figures 24 to 27, and Table 35). As planned, the 1985
fall survey was conducted late in the year so that "fall overturn"
conditions would be sampled in all lakes. "Fall overturn" occurred and the
resulting uniform chemical structure was clearly observed in all lake
basins except in northern Lake Michigan (Figures 19 to 22).
Nutrient Concentrations
Spring surface samples; In the analysis of the 1983-1984
surveillance data, Lesht and Rockwell (1985 and 1987) made comparisons of
water quality across years using basin-averaged nutrient concentrations
calculated from samples taken at the surface during the spring. This
subset of the data was chosen for comparison because it was assumed to be
spatially unbiased and representative of the open-lake water column during
spring isothermal conditions. Tables 36 and 37 show these data for Lakes
Michigan and Huron updated through 1985. A comparison of the 1983
through 1985 spring surface nutrient concentrations in Lake Erie is
presented in Table 38.
Due to the early warming in 1985 in Lake Erie, sampling during the
spring of 1985 was reduced to two runs. The number of samples collected
in spring 1985 is generally less than the number of samples collected in
spring 1983 but similar to 1984 where all three spring survey runs were
completed only in Lake Erie. The number of stations in 1985 was increased
-------
119
zo-
o" I
20-
LJ
ct:
ID
tr vs:
LJ
Q_
•^
LJ 10-
I—
fv
LJ
I— c
1 J:
Q
•^VA
x- **-
r—-^
\ *r^^^~Cf —
1983
J
-./•
.7 '
•** "*"
/I
fV
/
-7
//
; /
^ A
/ *
I i
/ /
~j*
/v
'k f
VN''
/ 1
/ /
»V
/
-1984
%
/
A\
M
1 v
"\
x
\
X>V
\
V^-1
I/
ia^
1985-
v\
^1
\
A
V
\
MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 48. Conparison of surface water temperatures 1983, 1984 and 1985
in the southern basin of Lake Michigan. The data are from
NDBO buoy 45007.
25-
cT '-
^ 20-
LJ
Cm
ID
\—
< 15-
cm
LJ
Q_
LJ 10-
I—
Cm ~
LJ
I— c
1 :
n-
>
^- —
1983-
^yv^^
IV
1 1
/
1
/v
I ,
yV'7
r S1
f
My
F
' /'•
/,,•
»//T?
'Jn
'
'V
rv^
-1984
"\
v\
*A
<^
I/N» S^
1985-
\
S^.
^-a,
\
^
v
S;
1983
•\
MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 49. Conparison of surface water tenperatures 1983, 1984 and 1985
in the northern basin of Lake Michigan. The data are from
NDBO buoy 45002.
-------
120
CJ,
LJ
OH
25
20-
< 15-
OH
LJ
Q_
8 10-
_K
MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 50. Comparison of surface water temperatures 1983, 1984 and 1985
in the northern basin of Lake Huron. The data are from NDBO
buoy 45003.
o,
LJ
cn
LJ
Q_
LJ 10
OH
LJ
MAR APR
MAY
JUN
JUL
AUG
SEP
OCT NOV
DEC
Figure 51. Comparison of surface water temperatures 1983, 1984 and 1985
in the southern basin of Lake Huron. The data are from NDBO
buoy 45008.
-------
121
MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure 52. Comparison of surface water tenperatures 1983, 1984 and 1985
in the western basin of Lake Erie. The data are from NDBO
buoy 45005.
in the southern basin of Lake Michigan and in the central and eastern
basins of Lake Erie reflecting recoirrnendations from the respective IJC
Task Forces. This somewhat compensated for reduced survey collections.
The 1984 and 1985 sampling surveys were conducted at about the same time
in the thermal cycle while the 1983 sampling was later in the thermal
cycle. These differences complicate the comparison of the three data
sets.
In general, we found fewer statistical similarities in basin-averaged
values (Tables 39 and 40) than those found between similar 1983 and 1984
comparisons (Lesht and Rockwell, 1987).
The 1985 summer temperature structure, when compared to the two
proceeding years, was found to be significantly (alpha=0.05) cooler.
During the other two surveys (spring and fall), 1985 water temperatures
were intermediate between 1983 and 1984 water temperatures. The 1985
spring survey temperatures were found to be significantly (alpha=0.05)
cooler than 1983 and the fall survey temperatures were found to be
significantly (alpha=0.05) warmer than 1984 water temperatures in all
-------
122
Table 35. Observed nutrient depletion in Lakes Michigan and Huron
comparing spring survey (maximum) concentrations with summer
survey (minimum) concentrations.3
Lake Dissolved Reactive Silicon Nitrate + Nitrite Nitrogen
Basin (ug/L) (ug/L)
By Year 1983 1984 1985 1983 1984 1985
Lake Michigan
Southern Basin Spring
Southern Basin Summer
Absolute Depletion
% Depletion
Northern Basin Spring
Northern Basin Summer
Absolute Depletion
% Depletion
Lake Huron
Northern Basin Spring
Northern Basin Summer
Absolute Depletion
% Depletion
Southern Basin Spring
Southern Basin Summer
Absolute Depletion
% Depletion
571.9
154.7
417.2
73.0
565.0
161.2
403.7
71.5
772.7
518.8
253.8
32.9
758.0
473.4
284.5
37.5
570.5
107.6
463.0
81.1
612.0
157.8
459.2
75.0
812.7
501.5
311.1
38.3
765.3
351.7
413.5
54.0
565.8
95.3
470.5
83.2
562.8
92.9
470.0
83.5
772.8
421.7
351.2
45.4
782.4
338.2
444.2
56.8
271
170
101
37.3
271
150
121
44.7
314
263
52
16.4
299
287
12
4.0
270
168
102
37.7
290
138
152
52.4
312
264
48
15.4
294
282
12
4.1
294
161
134
45.5
286
156
1311
45.6
302
267
35
11.7
301
276
8
8.1
a Station networks as defined by 1985 network and basin definitions.
b Calculation affected by rounding.
basins except Lake Erie. The early spring warming had stratified the
western basin of Lake Erie and had begun to stratify the central basin.
Other statistically significant differences in both 1983 and 1984,
when compared to 1985, in the spring are: higher nitrate + nitrite
concentrations in 1985 in Lake Michigan and the central and eastern basins
of Lake Erie; lower total phosphorus levels in southern Lake Michigan and
central Lake Erie; and higher dissolved reactive silica in southern Lake
Huron and western Lake Erie. Summer epilimnion comparisons showed
statistically significant, lower levels of dissolved reactive silica in
Lakes Michigan and Huron.
-------
123
Table 36.
Inter-year basin comparisons — Lake Michigan spring surface
samples from open-lake stations.3-
Year
]#>
Temperature
Total
Phosphorus
(ug-P/L)
Dissolved
Silica
(mg-Si02/L)
Dissolved
N02 + N03
(ug-NA)
Southern BasinS
1985
1984
1983
1977
1976d
1976f
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
12
12
62
9
5
52
15
7
74
9
6
39
3
1
6
9
6
38
2.5
2.5
2.6
2.2
2.2
2.3
3.8
3.9
3.8
2.6
2.8
2.5
4.5
4.6
4.3
7.3
7.8
5.9
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
± o.
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
+ 1.
+ 1.
+ 1.
32+
30+@
28+
55*
26*
46*
52
39
42
61
42
47
55
22
58
47
71
4.8 +
4.8 +
4.9 +
5.0 +
5.1 +
5-8 +
5.7 +
5.4 +
6.2 +
4.6 +
5.2 +
4.5 +
8.3 +
12.0
7.7 +
5.2 +
5.2 +
5.9 +
0.7+
0.7
1.0+
1.0
0.5
2.0
1.2
0.8
2.9
1.8
1.9
1.3
3.2
3.5
0.8
0.8
1.7
1.20 +
1.20 +
1.21 +
1.12 +
1.17 +
1.17 +
1.12 +
1.21 +
1.15 +
1.14 +
1.13 +
1.16 +
1.32 +
1.32
1.34 +
1.10 +
1.09 +
1.19 +
0.04+@
0.04
0.04
0.10
0.06
0.15
0.14
0.09
0.15
0.07
0.08
0.14
0.07e
e
0.0le
0.18
0.21
0.21
287 +
287 +
293 +
267 +
273 +
263 +
258 +
273 +
261 +
257 +
258 +
258 +
260 +
260
252 +
230 +
230 +
256 +
17+@
17
61+
14
12
18
26
18
25
10
11
12
10
04
24
27
93
Northern Basin
1985
1984
1983
1976^
1
2
3
1
2
3
1
2
3
1
2
3
10
10
62
8
5
47
12
7
67
7
5
49
2.4
2.4
2.5
1.9
1.9
2.2
3.5
3.7
3.6
2.9
3.1
3.1
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
+ 0.
24+<§
24+@
24+<§
41*
38*
57*
30
15
23
41
23
23
5.6 +
5.6 +
5.2 +
5.1 +
5.1 +
6.1 +
5.4 +
6.1 +
5.8 +
7.3 +
7.6 +
6.9 +
1.7
1.7
2.2 @
0.6
0.8
2.0
1.9
1.6
4.0
1.6
1.5
1.1
1.16 +
1.16 +
1.20 +
1.18 +
1.19 +
1.30 +
1.11 +
1.18 +
1.16 +
1.01 +
1.08 +
1.11 +
0.06
0.06
0.11+0
0.14
0.07
0.22
0.15
0.12
0.14
0.17
0.15
0.11
297 +
297 +
286 +
240 +
242 +
257 +
264 +
270 +
270 +
—
-
14+@
14+
15+@
57
57
39
24
22
33
-------
124
Table 36. (Continued) Inter-year basin comparisons — Lake Michigan spring
surface samples from open-lake stations.3
Year
Southern Basinc
l
1985 2
3
1984d
1983
1977
1976d
1976f
Northern Basin
1985
1984
1983
19769
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Chlorophyll-a
(ug/L)
0.98 + 0.75+
0.98 + 0.75
0.95 + 0.73+
0.71 + 0.28*
0.70 + 0.31*
0.66 + 0.34*
2.01 + 0.88
1.60 + 0.56
1.97 + 0.86
1.19 + 0.57
1.35 + 0.63
1.23 + 0.47
1.27 + 0.38
1.02
1.11 + 0.37
1.81 + 0.89
1.75 + 0.96
1.84 + 1.10
0.67 + 0.59
0.67 + 0.59
0.75 + 0.94+@
0.46 + 0.19*
0.36 + 0.11*
0.37 + 0.19*
1.37 + 1.01
0.91 + 0.19
1.15 + 0.81
1.29 + 0.45
1.10 + 0.25
0.91 + 0.26
Turbidity
(FTU)
0.43 + 0.13+
0.43 + 0.13+
0.40 + 0.14+
0.48 + 0.15*
0.41 + 0.12*
0.53 + 0.23
0.64 + 0.19
0.56 + 0.09
0.79 + 0.36
0.67 + 0.12
0.72 + 0.27
1.57 + 1.25
0.70
0.75 + 0.16
1.22 + 0.51
1.08 + 0.49
1.08 + 0.56
0.31 + 0.09+
0.31 + 0.09+
0.34 + 0.29+
0.29 + 0.10*
0.24 + 0.06*
0.38 + 0.33*
0.67 + 0.20
0.65 + 0.21
0.61 + 0.24
—
Chloride
(mg/L)
8.72 + 0.23
8.72 + 0.23
8.69 + 0.25+
8.87 + 0.25
8.82 + 0.33
8.83 + 0.25
8.74 + 0.42
8.81 + 0.27
8.15 + 0.17
8.17 + 0.19
8.12 + 0.16
8.05 + 0.21
8.20
8.04 + 0.19
7.90 + 0.14
7.92 + 0.16
7.89 + 0.15
8.83 + 0.40
8.83 + 0.40
8.84 + 0.31+
8.86 + 0.24
8.90 + 0.25
8.88 + 0.23*
8.70 + 0.36
8.73 + 0.44
8.69 + 0.30
7.73 + 0.10
7.70 + 0.15
7.73 + 0.16
Specific
Conductance
(uS/cm)
279.8 + 0.8
279.8 + 0.8
279.9 + 0.8+
278.4 + 4.8
277.0 + 6.3
278.3 + 5.4
278.9 + 1.6
279.4 + 1.4
275.1 + 2.2
275.3 + 2.5
275.0 + 2.2
273.0 + 1.73
274.0
273.8 + 0.47
271.8 + 1.4
271.7 + 1.4
272.8 + 1.3
279.3 + 0.9
279.3 + 0.9
279.8 + 0.9+0
278.2 + 1.8
278.4 + 2.3
278.2 + 4.4
278.3 + 1.92
279.1 + 1.07
279.2 + 1.38
—
-------
125
(Continued) Table 36 FOOTNOTES
a Values are means + one standard deviation.
b Row 1, N = the surface samples from all stations sampled during the
year. Row 2, N= surface samples from 1985 stations included in the
annual network. Row 3, N= samples from all depths from the stations in
the 1985 annual network sampled.
c Basin definition see Table 4, for 1983 and 1984 all stations numbered
27 and lower were used for the southern basin. See Lesht and
Rockwell (1985 and 1987).
d First survey of 1976; sampled in early May along transect 6; stations
depth of 80 meters or greater (Rockwell et al., 1980).
e SiO2 is total.
f Second survey of 1976; sampled in late May all transects; station depth
of 80 meters or greater (Rockwell et al., 1980).
9 First survey in 1976; sampled in late April by the University of
Michigan; station depth of 80 meters or greater (Rockwell et al. ,
1980).
Denotes that the t value exceeds the critical value to reject the null
hypothesis that 1983 and 1984 means are equal at alpha=0.05.
+ Denotes that the t value exceeds the critical value to reject the null
hypothesis that 1983 and 1985 means are equal at alpha=0.05.
<§ Denotes that the t value exceeds the critical value to reject the null
hypothesis that 1984 and 1985 means are equal at alpha=0.05.
-------
Table 37. Inter-year carper isons — Lake Huron, both basins, spring surface sanples from open-lake stations.3-
Total Dissolved NC^ + ND3 Water Specific
Hrxsphorus Silica Nitrogen Chloride Temperature Turbidity Conductance Chlorophyll-a
Year iP (ug/L) (mg-SiO^) (ug/L) (irg/L) (°C) (ITU) (uS/on) (ug/L)
1985 20 3.0 + 0.5-H9 1.656 + 0.039 302 + 24 5.37 ± 0.12-H§ 1.60 + 0.42 0.38 + 0.08 202.7 + 1.2 0.89 + 0.56-H§
1984C 20 3.6d + 0.7 1.678 ± 0.125 309 + 19 5.68 + 0.32 1.33 ± 0.46* 0.41 ± 0.15* 203.1 ± 2.2 0.51 + 0.23*
1983 30 3.7 + 1.4 1.636 ± 0.050 305 + 17 5.62 + 0.31 3.02 + 0.59 0.59 + 0.16 204.2 + 4.0 1.54 + 0.59
1980 19 4.7 + 1.4 1.529 + 0.074 290 + 12 202.9 + 3.0
1971 14 3.9 + 0.9 1.410 + 0.062 248 + 10 207.9 + 4.4
a Values are means + one standard deviation. Years 1983-1985 use the 1985 sampling network.
b N = number of stations sampled.
c = combined spring data from 1984-1 and 1984-2 (Lesht and Rockwell, 1987).
d Excludes one questionable value (12.0) , with this value 4.0 + 2.0, number of samples = 21.
+ 1985 is significantly different from 1983.
@ 1985 is significantly different from 1984.
* 1984 is significantly different from 1983.
-------
Table 38. Inter-year basin comparisons — Lake Erie spring surface samples from open-lake stations.1
Year
Total
i- Phosphorus
N° (ug/L)
Dissolved
Silica
(mg-Si02/L)
N02 + N03
Nitrogen
(ug/L)
Chloride
(mg/L)
Water
Temperature
fO s~i \
Turbidity Conductance Chlorophyll-a
(FTU) (uS/cm) (ug/L)
Western Basin
1985
1984C
1983
Central
1985
1984C
1983
Eastern
1985
1984C
1983
•Sl — s^s — =
6 21.0
9 31.4
9 25.6
, Basin
18 12.1
15 13.1
15 13.4
Raisin
8 13.0
9 15.0
9 14.9
+ 3.9
± 16. 5d
+ 17.9
± 1-4
+ 3.3
+ 6.0
+ 0.8(9
± 1-5
+ 10.3
1.297
0.802
0.886
0.017
0.029
0.018
0.144
0.218
0.037
± 0.283
+ 0.600
+ 0.591
+ 0.008©
± 0.016*
± 0.011
+ 0.024-H9
+ 0.056
+ 0.011
683 +
874 +
497 +
203 +
129 +
151 +
278 +
216 +
239 +
147*
370*
107
25+<§
27
49
17-H9
20
9
12.9 ± 2.0@
16.7 + 1.6
14.2 + 4.9
14.6 + 0.5*
14.5 + 0.4*
15.5 + 0.5
14.9 + 0.3*
15.0 ± 0.5
16.8 + 0.8
12.28 +
6.87 +
8.31 +
5.55 +
3.14 +
5.42 ±
1.99 +
1.26 +
4.23 ±
1.21+©
1.58
1.65
1.16(9
1.02*
0.82
0.26+@
0.75
0.74
5.98
19.02
9.90
1.60
1.78
1.53
2.21
2.96
2.33
+ 1.84@
+ 16.95
± 5.96
+ 0.53
+ 1.37
+ 0.43
+ 0.48(§
+ 0.44
± 0.55
254.5 + 10.5(9
273.0 + 19.1
259.4 + 35.3
276.2 + 2.9
276.0 + 3.5
28.1 + 4.5
276.4 + 1.4*
281.7 + 4.4
289.1 + 2.4
6.22 +
4.21 +
5.60 +
2.92 +
1.45 +
4.61 +
0.44 +
0.72 +
2.13 +
3.76(9
1.35
2.76
1 . 35+<9
0.48*
0.97
0.25-H9
0.19*
0.69
•r vcixutii) cLxe iiiecULb 3 uiie auciiiucLLU ut;viciu±uii.
° N = Number of samples included in the average.
^ Combined spring data from 1984-1 and 1984-2 (Lesht and Rockwell, 1987).
J Excludes one extreme value (125.0); with this value 41.8 + 34.8.
Denotes that t value exceeds critical value to reject null hypothesis that 1983 and 1984 means are equal at alpha=0.05.
t Denotes that t value exceeds critical value to reject null hypothesis that 1983 and 1985 means are equal at alpha=0.05.
L Denotes that t value exceeds critical value to reject null hypothesis that 1984 and 1985 means are equal at alpha=0.05.
-------
Table 39. Oomparison of epilirmicn mean values of selected parameters, spring surveys, 1983-1985.a
Basin/Year
Lake Mchigan-S
1985
1984 1 & P
1983
Late Mchigan-N
1985
1984 1 & 2
1983
Late Huron-N
1985
1984 1 & 2
1983
Late Huron-S
1985
1984 1 & 2
1983
Late Erie-W
1985
1984 1 & 2
1983
Late Etrie-C
1985
1984 1 & 2
1983
Late Erie-E
1985
1984 1 & 2
1983
Water
Temperature
ro
2.6
2.3
3.8
2.5
2.2
3.6
1.5
1.3
3.0
1.8
1.4
3.1
12.0
6.7
8.2
5.1
3.0
5.4
2.1
1.4
4.2
+ 0.28
+ 0.46
+ 0.42
+ 0.24
+ 0.57
+ 0.23
+ 0.26
+ 0.27
+ 0.32
+ 0.46
+ 0.58
+ 0.57
+ 1.19
± 1-47
+ 1.63
+ 1.06
+ 0.86
+ 0.79
+ 0.39
+ 0.76
+ 0.78
(62)
(52)
(74)
(62)
(47)
(67)
(58)
(57)
(80)
(45)
(45)
(71)
(14)
(21)
(27)
(60)
(48)
(48)
(40)
(48)
(48)
*
t
+3.67*
-21.5*
+4.16*
-24.9*
+ 2.75*
-28.9*
+3.63*
-12.6*
+11.2*
+7.63*
+10.7*
-1.67
+5.82*
-16.3*
Chlorophyll-a
(ug/L)
0.95
0.66
1.97
0.75
0.37
1.15
0.78
0.42
1.30
1.09
0.67
1.88
5.85
4.11
5.47
2.75
1.48
4.48
0.40
0.67
1.98
+ 0.73
+ 0.34
+ 0.85
+ 0.94
+ 0.19
+ 0.81
+ 0.59
+ 0.17
+ 0.48
+ 0.54
+ 0.15
+ 0.51
+ 3.35
+ 1.37
+ 2.65
+ 1.29
+ 0.54
+ 0.99
+ 0.23
+ 0.16
+ 0.50
(62)
(47)
(72)
(62)
(44)
(67)
(58)
(58)
(48)
(45)
(45)
(70)
(14)
(20)
(27)
(60)
(48)
(47)
(40)
(48)
(48)
*
t
+2.70*
-7.39*
+3.09*
-2.60*
+4.49*
-5.64*
+5.12*
-7.98*
+1.83
+0.39
+6.93*
-7.58*
-6.32
-19.4*
Dissolved Reactive Dissolved
Silicon * Nitrate + Nitrite
(ug/L) t Nitrogen (ug/L)
566.0 + 19.2 (62) 292.5 + 61.0
547.1 + 70.2 (50) +1.85 262.9 + 17.7
536.2 + 68.6 (73) +3.55* 260.5 + 25.0
562.8 + 50.0 (62) 286.3 + 15.2
605.4 + 104.9 (47) -2.57* 256.9 + 38.9
540.3 + 64.2 (67) +2.23* 269.7 + 33.3
772.8 + 20.0 (58) 302.1 + 26.5
812.7 + 60.5 (58) -4.76* 311.8 + 20.2
772.7 + 22.4 (79) +0.05 314.3 + 12.6
782.4 + 13.4 (45) 300.9 + 20.5
765.3 + 26.1 (43) +3.86* 293.9 + 19.1
758.0 + 23.3 (49) +6.30 299.0 + 16.7
633.1 + 166.9 (14) 698.7 + 163.8
369.9 + 259.4 (21) +3.35* 856.2 + 330.2
413.9 + 266.6 (24) +2.77* 494.1 + 97.9
9.7 + 5.8 (60) 204.5 + 21.1
13.8 + 7.4 (46) -3.22* 129.6 + 26.7
8.3 + 4.4 (46) +1.30 151.5 + 46.8
71.5 + 11.0 (40) 287.6 + 19.8
97.4 + 25.0 (48) -6.47* 218.2 + 16.0
17.8 + 3.7 (47) 28.1* 237.7 + 10.7
(62)
(51)
(73)
(62)
(47)
(67)
(58)
(58)
(79)
(45)
(44)
(49)
(14)
(21)
(27)
(60)
(47)
(46)
(40)
(48)
(47)
*
t
+3.64*
+3.86*
+4.89*
+4.79*
+2.23*
-3.26*
+1.68
+0.51
-1.86
+4.29*
+16.2*
+7.14*
+18.2*
+13.4*
Values are mean + one standard deviation with number of samples in parentheses. All stations sampled during respective
years.
JDIndicates 1984-1&2 combined spring data from ?pril and May surveys (Lesht and Rockwell, 1987).
*Denotes t value exceeds the critical value to reject null hypothesis that means are equal with alpha=0.05, 1984 t value
compares 1985 to 1984 means, 1983 t value compares 1985 to 1983 means.
ro
00
-------
Table 39. (Continued) Comparison of epilimnion mean values of selected parameters, spring
surveys, 1983-1985a.
Basin/Year
Late Mchigan-S
1985
1984 1 & 2b
1983
Late MLChigan-iNJ
1985
1984 1 & 2
1983
Late Huron-N
1985
1984 1 & 2
1983
Late Huron-S
1985
1984 1 & 2
1983
Late Erie-W
1984 l & 2
1983
Late Erie-C
1985
1984 1 & 2
1983
Late Erie-E
1985
1984 1 & 2
1983
Total
HTOsphorus
(ug/L)
4.9
5.8
6.2
5.2
6.1
5.8
3.3
3.8
4.8
3.6
3.7
4.7
20.7
38.9
25.7
12.8
14.0
13.4
12.8
15.7
11.1
+ 1.0
+ 2.0
+ 4.9
+ 2.2
+ 2.0
+ 4.0
+ 1.8
+ 1.4
+ 3.5
+ 1.7
+ 0.9
+ 3.4
+ 3.9
+ 27.3
+ 19.1
+ 2.3
+ 4.5
+ 5.2
+ 1.3
+ 3.9
+ 5.8
(62)
(51)
(73)
(62)
(47)
(66)
(57)
(58)
(80)
(45)
(44)
(70)
(14)
(21)
(26)
(60)
(47)
(47)
(40)
(48)
(48)
*
t
-2.73*
-3.60*
-2.04*
-1.0
-1.57
-3.38*
-0.53
-2.39*
-3.00*
-1.27
-1.71
-0.78
-4.76*
+2.02*
Total Dissolved
Phosphorus
(ug/L)
2.4
2.3
2.0
2.8
2.8
2.6
1.3
1.4
1.6
1.3
1.4
1.6
3.9
5.0
4.9
3.8
3.9
3.3
6.2
6.5
3.5
+ 0.8
+ 0.8
+ 1.4
+ 1.1
+ 1.8
± 1-5
+ 0.5
+ 0.5
+ 1.1
+ 0.6
+ 0.7
+ 0.9
+ 2.0
+ 3.3
+ 5.7
+ 0.6
+ 0.9
+ 1.5
+ 0.6
+ 1.6
+ 1.8
(62)
(51)
(74)
(62)
(46)
(49)
(57)
(56)
(72)
(45)
(44)
(66)
(14)
(21)
(25)
(60)
(47)
(45)
(40)
(48)
(42)
*
t
+0.29
+1.75
-0.06
+0.82
-1.54
-1.89
-0.63
-2.08*
-1.09
-0.75
-1.04
+1.94
-1.52
+8.66*
Dissolved Reactive
Qrtho phosphorus *
(ug/L) t
0.9 +
0.9 +
0.8 +
0.9 +
1.2 +
1.4 +
0.3 +
0.3 +
0.6 +
0.5 +
0.2 +
0.6 +
1.0 +
1.6 +
1.1 +
0.9 +
0.4 +
0.9 +
2.7 +
2.4 +
1.9 +
0.6
1.2
0.9
0.6 (62)
1.8 (47)
1.4 (45)
0.3 (58)
0.7 (58)
0.6 (54)
0.4 (45)
0.4 (44)
0.5 (45)
1.0 (14)
2.3 (21)
0.5 (23)
0.3 (60)
0.2 (47)
0.7 (45)
0.7 (40)
1.2 (48)
1.6 (47)
-0.16
+0.91
-1.17
-2.13*
-0.55
-3.32*
+3.83*
-0.41
-0.99
-0.35
+10.5*
+0.55
+1.21
+3.07*
Values are mean + one standard deviation with number of samples in parentheses. All stations
sampled during respective years.
Indicates 1984-1&2 coribined spring data from April and May surveys (Lesht and Rockwell, 1987).
Denotes t value exceeds the critical value to reject null hypothesis that means are equal with
alrte=0.05 1QP4 t ™i'-a rr^K-^roc. ]_gpc 4-^ t~p/i ^^
-------
130
Table 40. Suranary of statistically significant differences (two-tailed
t-test, alpha=0.05) between epilimnion data collected in 1985
with 1983 and 1984 for selected parameters.a
W Temp13 Chl-a13 Silicon13 ND^-N13 Total P13 Total DP13 SRP13
83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5
Basin SPRING
LMS- + - + + + + --
LMN - + - + + - + +
LHN - + -+ __.__
LHS - + - + + + - - +
LEW + + + + +
LEG +-+- + + +
T TTTT _l_ _i_ J_ _i_ _i_ _i_ i
I iPJ. —' T ~~ —• T ~~ T- -f- T *~* T ~|~
83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5
Basin SuTVMER
LMS -- + + ---
LMN --+ -- + --
LHN -- + + -- +
LHS-- + + - - - + +
LEW - - + + - +
LEG - + + + - +
Tin? — _i_ _L _i_ j_
I_ ipflPf i T ~~ ^~ ~~ ~~" "T" T
83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5 83-5 84-5
Basin FftLL
LMS- + --+ + + +---
LMN - + -- + -+ -- --
LHN - + -- - + - ____
LHS - + --+ + + --
LEW - + -- + + + + + +
LEG - + --- + + - + + + +
a A plus sign indicates a higher parameter mean in 1985 and a negative
sign indicates a lower mean in 1985.
b W Temp=Water Temperature,
Chl-a=€hlorophyll-a,
Silicon=Dissolved Reactive Silicon,
NOx-ISNDissolved Nitrite+Nitrate-Nitrogen,
Total P=Total Phosphorus,
Total DP=Total Dissolved Phosphorus,
and SRP=Soluble Reactive Phosphorus.
-------
131
DETECTION OF SIGNIFICANT CHANGES
One question of interest when comparing surveillance data across
years is whether there has been a statistically significant change in the
mean value of a parameter over the period of comparison. Statistically,
this question is cast in terms of using an appropriate test to either
reject or accept the null hypothesis that there has been no change. The
value of the test statistic used in most cases will depend on the
difference between sample means, the parameter variance, and the size of
the samples. In the case of the current surveillance program we are
interested in estimating, given observed variances and known number of
samples, how large a mean concentration change would be required to reject
the null hypothesis that there has been no change. Such an estimate is
useful in evaluating both the program design and the application of the
program results to analysis of water quality trends.
If we make the assumption that the true variance of a parameter is
constant across sample periods, we can calculate the difference in means
that would be required for rejection of the null hypothesis from the
expression for the Student's t statistic (Walpole and Myers, 1978):
t =
in which Rj_ are the mean values, do is the true difference being tested
for (in this case do = 0), n± are the number of samples, and Sp is the
pooled standard deviation calculated by
S|5 = ((nx - l)sf + (n2 - DS2.) / (% + n2 - 2) (2)
where the S^ are the sample variances. The appropriate t distribution
has nj^ + n2 - 2 degrees of freedom.
Making the further assumptions that future sampling will follow the
sampling plan used in 1983 and 1984, have an equal number of sampling
points and that the sample variance of a parameter will be unchanged, we
-------
132
can simplify the expression for t (equation 1) to
t = (delta) / (ZtsJ/hi) )V2 (3)
from which, given a confidence level, the required difference, delta, can
be calculated.
This expression for the required difference, delta, can be
generalized by defining
delta = % - x2 = S1t(2/n1)1/2 (4)
and calculating the percent change required for detection of a
significant difference as a function of the parameter coefficient of
variation and the sample size. This may be written
- x2) / xi = (Si/ %) t (Z/h^ (5)
Thus for a given sample size, n^' assumed to be equal in both years,
the percent change required to detect a significant difference is a
linear function of Sj/ xlf the parameter coefficient of variation, which
also is assumed to be constant in this example. This function is graphed
for several sample sizes in Figure 53. Minimum concentration differences
in spring surface parameters are compared by basin in Table 41.
The true variance of any sampled parameter is necessarily unknown,
and the significance of the sampled variance must be considered
carefully. Calculating sample means and variances and using parametric
tests for statistical estimation is based on the assumption that the
samples are independent, random samples from a normal population. For
limno logical data, this assumption translates into sampling from a
homogeneous water mass in which the variable to be measured is spatially
uniform. Thus, sampling and analysis would be the major sources of error
in an individual measurement. Given similar sampling and analysis
techniques, then, we could expect similar sample variances from year to
-------
133
0s-
UJ
X
o
Q
LU
QC
13
O
UJ
cc
100-1
80-
60-
40-
20-
N-tO
-—i—.—i—.—i—•—•—•—i—• •—' r—
20 40 60 80
COEFFICIENT OF VARIATION (%)
100
Figure 53. The change required for the detection of significant
(alpha=0.05) differences using the two-tailed t-test as a
function of the parameter coefficient of variation and the
sample size.
year. Sample variances for selected parameters measured in 1983 through
1985 are compared by basin in Tables 42 to 44.
Tables 42 to 44 show that the parameter variance may not be constant
from year to year. The degree to which this is true depends on the data
subset used. We find that, as may be expected, the subset of all samples
(Table 42) has many more cases of differing parameter variances than does
the subset of spring surface values (Table 43). This occurs because the
degrees of freedom for the first subset increases faster than the sample
variance, thereby increasing the sensitivity of the F-test.
Similarly, we find that the number of cases in which the parameter
variances are statistically different is greater for the subset of spring
surface samples (Table 43) than for the subset of spring station averages
(Table 44). in general, this is due to the reduction in sample variance
resulting from representing each station by an average of several samples
rather than by one sample.
-------
Table 41. MLninun difference of means (delta) for rejection of null hypothesis, Hr,: %=
spring sanples.a
(alpha=0.05) for all
Nunter
Earameter 1983
of Sanples x IVfean of Sanples
1984 1985 1983 1984 1985
s2 Variance of
1983 1984
Sanples
1985
1983 to 1984
d. f . t delta
1984 to 1985
d.f. t delta
lake Michigan Southern Basin
Total Fhos. (ug/L)
Silica (mg-SiC^/L)
ND^HKDyN (ug/L)
Turbidity (FIU)
Conductivity (uS/on)
Chloride (mg/L)
ChLorophyll-a (ug/L)
73
73
73
74
74
72
72
51
50
51
51
51
51
47
62
62
62
58
62
62
62
6.24
1.147
261
0.65
278.9
8.72
1.97
5.79
1.170
263
0.53
278.3
8.83
0.66
4.94
1.211
293
0.40
279.9
8.69
0.95
8.4419
0.0216
0.6
0.0465
1.1494
0.1441
0.7356
4.1927
0.0226
0.3
0.0517
29.301
0.0606
0.1190
0.9771
0.0017
3.7
0.0196
0.6354
0.0602
0.5282
122
121
122
123
123
121
117
1.980
1.980
1.980
1.980
1.980
1.980
1.980
0.935
0.054
8
0.079
1.279
0.120
0.261
111
110
111
107
111
111
107
1.982
1.982
1.982
1.982
1.982
1.982
1.982
0.584
0.040
18
0.071
1.379
0.092
0.228
Total Fhos. (ug/L)
Silica (mg-SiC^/L)
NO2-HXD3^ (ug/L)
Turbidity (FIU)
Ctriductivity (uS/on)
Chloride (mg/L)
Chlorophyll-a (ug/L)
Total Ehos. (ug/L)
Silica (mg-SiC^/L)
N02-HND3-W (ug/L)
Turbidity (FIU)
Conductivity (uS/cm)
Chloride (mg/L)
Chlorophyll-a (ug/L)
Lake Michigan Northern Basin
66
67
67
67
67
66
67
47
47
47
41
45
41
44
62
62
62
62
62
62
62
5.80
1.156
270
0.61
279.2
8.69
1.15
6.07
1.295
257
0.38
278.2
8.88
0.37
5.23
1.204
286
0.34
279.8
8.84
0.75
16.158
0.0189
1.1
0.0567
1.9069
0.0887
0.6514
4.1902
0.0504
1.5
0.1060
19.233
0.0518
0.0363
4.9702
0.0114
0.2
0.0825
0.7742
0.0961
0.8785
111
112
112
106
110
105
109
1.982
1.982
1.982
1.982
1.982
1.982
1.982
1.266
0.067
13
0.108
1.136
0.108
0.246
107
107
107
101
105
101
104
1.982
1.982
1.982
1.984
1.982
1.984
1.984
0.825
0.064
11
0.121
1.132
0.112
0.285
Lake Huron Northern Basin
80
79
79
76
79
78
76
58
58
58
58
58
58
58
57
58
58
56
58
53
58
4.85
1.653
314
0.60
203.3
5.51
1.30
3.78
1.739
312
0.37
203.4
5.49
0.42
3.31
1.653
302
0.39
202.7
5.41
0.78
12.303
0.0023
0.2
0.4008
4.3815
0.0508
0.2315
2.0312
0.0168
0.4
0.0177
3.4618
0.0192
0.1704
3.0913
0.0018
0.7
0.0203
1.3092
0.1448
0.3455
136
135
135
132
135
134
132
1.977
1.977
1.977
1.979
1.977
1.979
1.979
0.964
0.031
6
0.167
0.683
0.066
0.156
113
114
114
112
114
109
114
1.982
1.982
1.982
1.982
1.982
1.982
1.982
0.591
0.035
9
0.051
0.568
0.106
0.187
Lake Huron Southern Basin
Total HlOS. (ug/L) 70 44 45 4.73 3.73 3.57 11.463 0.7500 3.0137 112 1.982 1.034 87 1.987 0.580
Silica (mg-SiC^/L)
ND2-HSD3-N (ug/L)
Turbidity (FIU)
Conductivity (uS/cm)
Chloride (mg/L)
Chlorcphyll-a (ug/L)
49
49
60
71
50
70
43
44
44
44
45
45
45
45
45
45
45
45
1.622
299
0.65
205.0
5.76
1.88
1.637
294
0.58
204.2
5.79
0.67
1.674
301
0.53
203.4
5.38
1.10
0.0025
0.3
0.0346
5.2712
0.1318
0.2593
0.0031
0.4
0.0412
5.5037
0.0453
0.0221
0.0008
0.4
0.1074
1.7387
0.0180
0.2865
90
91
102
113
93
113
1.987
1.987
1.984
1.982
1.987
1.982
0.022
7
0.076
0.880
0.123
0.155
86
87
87
87
88
88
1.987
1.987
1.987
1.987
1.987
1.987
0.019
8
0.115
0.799
0.075
0.165
GJ
a Sanples are from each year's entire network using the 1985 basin definiticns.
-------
Table 41. (Continued) Mirxmum difference of means (delta) for rejection of null hypothesis, HQ: xj_= x2 (alpha=0.05)
for all spring sanples.a
Number
Parameter 1983
Total Phos. (ug/L)
Silica (mg-Si02/L)
NCVrHM^-N (ug/L)
Turbidity (FIU)
Conductivity (us/on)
Chloride (mg/L)
Chlorophyll-a (ug/L)
Total Phos. (ug/L)
Silica (mg-Si02/L)
M32-HXD3-N (ug/L)
Turbidity (FIU)
Conductivity (uS/on)
Chloride (mg/L)
Chlorophyll-a (ug/L)
Total Phos. (ug/L)
Silica (mg-SiC^/L)
ND2-+N03-ftI (ug/L)
Turbidity (FIU)
Conductivity (uS/on)
Chloride (mg/L)
Chlorophyll-a (ug/L)
26
24
27
27
27
27
27
47
46
46
48
48
47
47
48
47
47
48
48
47
48
of Samples x IVfean of Samples
1984 1985 1983 1984 1985
21
21
21
21
21
21
20
47
46
47
48
48
46
48
48
48
48
48
48
48
48
14 25.66
14 0.885
14 494
14 10.20
14 260.6
14 14.48
14 5.47
60 13.41
60 0.018
60 152
60 1.67
60 278.2
60 15.44
60 4.48
40 11.09
40 0.038
40 238
40 2.468
40 289.7
40 16.85
40 1.98
38.87
0.791
856
18.47
270.4
16.60
4.12
14.00
0.030
130
2.05
276.9
14.59
1.48
15.69
0.208
218
3.38
283.7
15.10
0.68
Late
20.71
1.354
699
6.39
256.2
13.11
5.85
Late
12.78
0.021
205
1.77
276.5
14.65
2.76
Late
12.84
0.153
288
2.63
278.2
14.94
0.40
sz Variance of Samples
1983 1984 1985
1983 to
d.f. t
1984
delta
1984 to
d.f. t
1985
delta
Erie Western Basin
365.91
0.3252
9.6
31.951
1204.0
25.148
7.0336
746.42
0.3080
109
246.41
288.80
2.0773
1.8846
15.218
0.1274
26.8
2.1019
227.70
5.7888
11.244
45 2.013
43 2.017
46 2.013
46 2.013
46 2.013
46 2.013
45 2.014
13.661
0.339
135
6.553
16.629
2.277
1.310
33
33
33
33
33
33
32
2.037
2.037
2.037
2.037
2.037
2.037
2.035
15.047
0.342
195
8.613
11.435
1.322
1.691
Erie Central Basin
27.059
0.0001
2.2
0.1984
14.483
0.2524
0.9795
19.993
0.0003
0.7
3.0618
10.221
0.1811
0.2946
5.1752
0.0002
0.4
0.5125
6.0501
0.2009
1.6682
92 1.987
90 1.987
91 1.987
94 1.987
94 1.987
91 1.987
93 1.987
1.988
0.005
16
0.518
1.425
0.192
0.325
105
104
105
106
106
104
106
1.982
1.984
1.982
1.982
1.982
1.984
1.982
1.319
0.005
9
0.492
1.079
0.171
0.395
Erie Eastern Basin
33.815
0.0001
0.1
0.4913
4.3894
0.3848
0.2530
15.288
0.0029
0.3
1.9327
32.509
0.2426
0.0270
1.6040
0.0006
0.4
0.6849
4.1071
0.0574
0.0551
94 1.987
93 1.987
93 1.987
94 1.987
94 1.987
93 1.987
94 1.987
2.010
0.016
6
0.447
1.742
0.228
0.152
86
86
86
86
86
86
86
1.987
1.987
1.987
1.987
1.987
1.987
1.987
1.282
0.018
8
0.497
1.885
0.169
0.085
CO
en
a Samples are from each year's entire network using the 1985 basin definitions.
-------
Table 42. Gcnparison of standard deviations of selected parameters, spring survey, all samples, 1983-1985.a
Total HTosphorus (ug/L) Dissolved Reactive Silica (mg-Si02/L) Nitrate + Nitrite Nitrogen (ug/L)
1983 1984 1985 83/84 83/85 84/85 1983 1984 1985 83/84 84/85 84/85 1983 1984 1985 83/84 83/85 84/85
F*F*F* F*F*F* F*F*F*
Lake Michigan
Southern Basin 2.912.050.99 0.1470.150 0.041 25 18 61
(73) (51) (62) 2.01* 8.64* 4.29* (73) (50) (62) 1.05 12.8* 13.4* (73) (51) (62) 2.00* 5.93* 11.96*
Northern Basin 4.022.052.23 0.1370.2240.107 33 39 15
(66) (47) (62) 3.86* 3.25* 1.19 (67) (47) (62) 2.67* 1.65* 4.41* (67) (47) (62) 1.37 4.79* 6.57*
lake Huron
Northern Basin 3.511.431.76 0.0480.1300.043 13 20 26
(80) (58) (57) 6.06* 3.98* 1.52 (79) (58) (58) 7.26* 1.27 9.20* (79) (58) (58) 2.57* 4.43* 1.72*
Southern Basin 3.390.871.74 0.0500.0560.029 17 19 20
(70) (44) (45) 15.29* 3.80* 4.02* (49) (43) (45) 1.25 3.04* 3.80* (49) (44) (45) 1.30 1.49 1.15
Lake Erie ~~ ~~~~,_.
CO
Western Basin 19.127.3 3.90 0.570 0.5550.357 98 330 164 ^
(26) (21) (14) 2.04 24.0* 49.05 (24) (21) (14) 1.06 2.55 2.42 (27) (21) (14) 11.38* 2.80* 4.06*
Central Basin 5.204.472.27 0.009 0.0350.012 47 27 21
(47) (47) (60) 1.35 5.23* 3.86* (46) (46) (60) 13.5* 1.76 7.69* (46) (47) (60) 3.07* 4.91* 1.60
Eastern Basin 5.823.911.27 0.008 0.0530.024 11 16 21
(48) (48) (40) 2.21* 21.1* 9.53* (47) (48) (37) 45.1* 8.95* 5.04* (47) (48) (37) 2.24* 3.73* 1.66
a Values are sample standard deviations with the number of samples in parentheses. Samples are from each year's entire
network using the 1985 basin definitions.
* F value exceeds the critical value required to reject the null hypothesis that variances are equal (alpha=0.05).
-------
Table 43. Comparison of standard deviations of selected parameters, spring survey, surface sanples, 1983-1985.a
Total Hnsphorus (ug/L) Dissolved Reactive Silica (irg-SiCb/L) Nitrate + Nitrite Nitrogen (ug/L)
1983 1984 1985 83/84 83/85 84/85 1983 1984 1985 83/84 84/85 84/85 1983 1984 1985 83/84 83/85 84/85
F* F* F* F* F* F* F* F* F*
Lake Michigan
1.23 1.02 0.72
Southern Basin
Northern Basin
Lake Huron
Northern Basin
Southern Basin
Lake Erie
Western Basin
Central Basin
Eastern Basin
(15) (8)
1.94 0.60
(12) (8)
1.29 0.38
(15) (10)
1.51 0.85
(14) (8)
17.9 16.6
(8) (8)
6.0 3.3
(15) (15)
10.4 1.5
(9) (9)
(12) 1.45 3.0
1.69
(9) 10.1* 1.3
0.50
(10) 11.8* 6.8*
0.52
(9) 3.1 8.5*
3.8
(6) 1.2 21.6*
1.4
(18) 3.3 19.4*
0.8
(8) 50* 179*
0.137 0.104 0.036
2.0 (15) (9) (12) 1.7
0.152 0.140 0.063
7.7* (12) (8) (10) 1.2
0.048 0.151 0.044
1.7 (16) (11) (11) 10.1*
0.055 0.056 0.029
2.7 (10) (8) (9) 1.01
0.591 0.600 0.283
18.4* (8) (9) (6) 1.0
0.011 0.056 0.008
5.9* (15) (15) (18) 2.1
0.011 0.056 0.024
3.6* (9) (9) (8) 25.5*
14.1* 8.2*
5.7* 4.8*
1.2 11.6*
3.7 3.8
4.4 4.5
2.1 4.3*
4.7* 5.5*
26
(15)
24
(12)
15
(16)
18
(10)
370
(9)
49
(15)
9
(9)
14
(9)
57
(8)
15
(11)
17
(9)
147
(9)
29
(15)
20
(9)
17
(12)
14
(10)
27
(11)
23
(9)
147
(6)
25
(15)
17
(8)
3.
5.
1.
1.
12.
3.
4.
36
57*
00
00
0*
27*
70*
2.22
3.05
3.13*
1.65
1.90
3.94*
3.45
1.64
17.0*
3.12
1.72
6.32
1.20
1.36
a Values are sairple standard deviations with the nurrber of sanples in parentheses. Sanples are fron each year's entire
network using the 1985 basin definitions.
F value exceeds the critical value required to reject the null hypothesis that variances are equal (alpha=0.05).
CO
-------
Table 44. Comparison of standard deviations of selected parameters, spring survey, station averages, 1983-1985.a
Total Riospnorus (ug/L) Dissolved Reactive Silica (mg-SiC^/L) Nitrate + Nitrite Nitrogen (ug/L)
1983 1984 1985 83/84 83/85 84/85 1983 1984 1985 83/84 83/85 84/85 1983 1984 1985 83/84 83/85 84/85
F* F* F" F* F* F* F* F* F*
late Michigan
2.30 1.29 0.61 0.152 0.151 0.041 26 17 36
Southern Basin (15) (10) (12) 3.1914.1* 4.43* (15) (10) (12) 1.0213.8*13.5* (15) (10) (12) 2.30 1.92 4.42*
2.83 1.39 1.71 0.145 0.071 0.067 36 41 12
Northern Basin (12) (8) (10) 4.17 2.74 1.52 (12) (8) (10) 4.17 4.62 1.11(12) (8) (10)1.26 9.17*11.6*
lake Huron
2.79 0.73 0.63 0.048 0.137 0.042 13 17 29
Northern Basin (16) (11) (11) 14.5*19.5* 1.34 (16) (11) (11) 8.23* 1.27 10.46* (16) (11) (11)1.604.49* 2.81
2.23 0.75 0.87 0.057 0.056 0.032 18 17 21
Southern Basin (14) (9) (9) 8.79*6.54*1.34 (10) (9) (9) 1.06 3.23 3.06 (10) (9) (9) 1.131.27 1.43
Late Erie
19.5 32.8 3.13 0.597 0.656 0.351 101 406 158 j-j
Western Basin (9) (6) (6) 2.8438.7* 110 (8) (6) (6) 1.21 2.89 3.50 (9) (6) (6)16.1* 2.436.61* oo
3.11 3.84 1.56 0.009 0.020 0.009 48 28 23
Central (15) (10) (18) 1.53 3.97* 6.09* (15) (10) (18) 5.06* 1.07 4.72* (15) (10) (18) 2.96* 4.61* 1.56
4.03 2.62 1.11 0.009 0.054 0.023 10 19 19
Eastern Basin (9) (6) (8) 2.37*13.1*5.55* (9) (6) (8) 33.4* 5.90* 5.66* (9) (6) (8)3.97 3.93 1.01
Values are sanple standard, deviations with the number of samples in parentheses. Samples are from each year's entire
network using the 1985 basin definitions.
*F value exceeds the critical value required to reject the null hypothesis that variances are equal (alpha=0.05).
-------
139
The sample variance of the station averages (Table 44) is in the
range of the analytical variance of the low and high check standards
(Table 7) (e.g., N02 + NO3 and Si02). A similarity between sample
variances of the station averages and analytical variance would be
expected if the true spatial variability is small relative to the
analytical variability. Comparing basins, the variances of the spring
station averages (Table 44) were similar within a given year in most
basins except for Lake Erie's western basin. Western basin Lake Erie's
variance is one to two orders of magnitude higher than other basins. This
may be because western Lake Erie is very shallow and is a mixing zone for
several significant rivers that pass through large metropolitan areas
resulting in spatial heterogeneity.
COMPARISON! WITH RECENT HISTORICAL DATA
In our reports describing the results of the 1983 and 1984
surveillance program, we compared the data collected in 1983 and 1984
with similar subsets of data collected in earlier years. In this section
we will update these comparisons using the data collected in 1985.
Lake Michigan
Inter-year comparisons based on similar subsets of spring open-lake
surface data collected in Lake Michigan were listed in Table 36. Lake
Michigan was sampled intensively in 1976 (whole lake) and in 1977
(southern basin only). Results of the 1976 sampling are described by
Rockwell et al. (1980) and by Bartone and Schelske (1982). Comparison of
the 1977 data with that from 1976 show a significant (alpha = 0.05)
decline in the concentration of total phosphorus and in turbidity.
Significant increases occurred in nitrate + nitrite nitrogen and chloride
concentrations. The magnitude of the changes shown in Table 36 are
different from those reported in Rockwell et al. (1980) because the subset
of stations used here was different from those used for the earlier
calculations.
Comparison of the 1983 data with the 1977 arid 1976 values showed that
total phosphorus levels in the northern basin and, by extension, the
southern basin were still significantly lower than they were in 1976, but
-------
140
significantly higher than in 1977. The 1984 data showed that levels of
total phosphorus in Lake Michigan continue to be low. The 1985 data show
no change in southern Lake Michigan total phosphorus concentrations from
1984 levels and a return in the northern basin concentration to the 1983
level. Reactive silica and nitrate + nitrite values in 1985 were the
highest measured since 1977. The 1985 chloride values were unchanged in
the northern basin and lower in the southern basin. Previously the annual
rate of increase of chloride between 1976 and 1983 was 0.103 mg/L. This
rate is almost identical to that calculated from chloride measurements
made at water intakes (Rockwell et al., 1980).
From 1983 to 1984 the increase in chloride concentration was 0.12
mg/L in the southern basin and 0.16 mg/L in the northern basin. The
annual rate of increase between 1976 and 1984 was 0.195 mg/L- The rate of
increase appears to have slowed in the northern basin over the last three
years to 0.075 mg/L. In the southern basin the 1985 concentration levels
were lower than the 1983 concentration levels. If real, southern basin
chloride decreases may be due to several causes. Lower road salt usage
may be expected over the last three years since winter snow falls in
Milwaukee (42.6") and Chicago (38.2") have averaged below the average
forty-year snowfalls of 47.2" and 40.4", respectively. Water levels
increased in Lake Michigan by one foot between April 1984 and April 1985
which would contribute 0.37% more volume or at most 0.04 mg/L decrease in
chloride concentrations from the 1984 levels (8.8-8.9 mg/L). Errors in
field data determination are also possible. Table 8 shows a slight
negative bias in the low chloride check standard (5.5 verses the expected
5.6 mg/L). This latter effect would contribute 1.8% decrease or 0.16
mg/L. For a one-year decrease in chloride concentrations of 0.2 mg/L
magnitude in all of Lake Michigan, chloride loading would have to
decrease about 700,000 metric tons. This would represent about a 20%
decrease in total lake loading as compared to the mid-to-late 1970
loadings (Sonzogni et al., 1983).
In addition to inter-year comparisons based on standard statistical
descriptions of the spring surface samples we also used graphical
techniques to examine recent trends in Lake Michigan water quality.
-------
141
Figure 54 shows the variable width notched box plot (JVtGill et al., 1978)
that we used in analysis. The purpose of the box plot is to display many
characteristics of a set of data in a concise format. Based on order
statistics, the variable width, notched box plot gives the viewer a more
complete sense of the data set than is provided by examining just the
simple mean and standard deviation. This is especially important in water
quality analyses where one spurious value often can have a
disproportionate influence on the sample statistics. Box plots have been
applied to water quality data by Reckhow (1980) and Neilson (1983).
As illustrated in Figure 54, the box plots show the mean and median
of the data sets, the maximum and minimum values, and the upper and lower
quartiles. Thus half of the observations fall within the box. The notch
represents the 95% confidence internal for the median, which may, on
occasion, fall outside of either the upper of lower quartiles. Two boxes
with notches which do not overlap have significantly different medians
from each other. The width of the box is proportional to the square root
of the number of observations. These features allow easy comparisons
across data sets.
Figure 55 (DISSPIA software) shows the distribution of total
phosphorus data collected during the spring in Lake Michigan from 1976-
1985. These data show the major decline that occurred between 1976 and
1977 as well as the increase between 1977 and 1983. The spread of data is
much wider in 1984 than in 1983 and 1985, and the 1985 median value is
significantly lower than 1983 and 1984 but comparable to the 1977 levels.
The decline in total phosphorus observed between 1976-1977 has been
hypothesized to represent loss to the sediments. This loss seems to be
related to the extremely harsh winter and extensive ice cover that
occurred on Lake Michigan during the winter of 1976-1977 (Rockwell et al. ,
1980; Rodgers and Salisbury, 1981a). The fact that similar concentrations
of total phosphorus were measured in the northern and southern basins in
1976 by different agencies lends credence to the reported values. The
increase in total phosphorus concentration that seems to have occurred in
-------
142
MAXIMUM VALUE
95% CONFIDENCE LIMIT
OF THE MEDIAN
MEAN
UPPER QUARTILE
MEDIAN
LOWER QUARTILE
MINIMUM VALUE
WIDTH PROPORTIONAL
TO SORT (N)
Figure 54. Key to variable width, notched box plots (McGill et al.,
1978.)
Lake Michigan since 1977 may represent a return of phosphorus from the
sediments.
Recent loadings to Lake Michigan (Table 49) suggest fairly stable
inputs. Model calculations, presented in the following section, suggest
that phosphorus concentrations in Lake Michigan declined from 1976-1977
and have remained fairly stable since then, in rough agreement with these
observations. Thus, these year-to-year changes appear to represent the
normal variability of a oligotrophic system.
Surface Lake Michigan spring silica values seem to have remained
fairly constant since 1977. However, the open-lake spring 1985 values in
the northern basin were higher than the 1984 values. Silica is a
particularly important nutrient in Lake Michigan. Some researchers have
asserted that silica is the limiting nutrient for diatom growth in the
spring (Schelske and Stoermer, 1971), and there has been a continuing
controversy about long-term depletion of silica in the lake (Shapiro and
Swain, 1983; Schelske et al., 1983).
-------
143
O
Q.
V)
O
CL q
t
Figure 55.
g
i/i
i
O)
,
to
T>
0)
_>
O
l/>
b
"73
IJC TARGET
21.0
CONCENTRATION
"73
"51
"55
1976
1977
1983
1984
1985
Box plot comparison of spring total phosphorus concentrations
in the southern basin of Lake Michigan, 1976-1985. The values
shown for 1976 and 1977 intensive surveys represent stations
with depths of 80 meters or greater.
r
•59
"73
"6t
"50
"73
1976
1977
1983
1984
1985
Figure 56. Box plot comparison of spring dissolved reactive silica
concentrations in the southern basin of Lake Michigan, 1976-
1985. The values shown for 1976 and 1977 intensive surveys
represent stations with depths of 80 meters or greater.
-------
144
The distribution of dissolved reactive silica in Lake Michigan during
the spring is shown in Figure 56. These data show a rather steady
increase in the concentration of silica from 1976 to 1985 both in average
as well as median values. Minimum concentrations are at their greatest
concentrations in 1985. It should be noted that these plots include all
of the samples collected during the spring; not just the surface samples,
upon which the statistics presented in Table 36 are based.
Comparison of all dissolved nitrate + nitrite data for the period
1976-1985 (Figure 57) also shows a steady, significant increase in median
concentrations. The mean calculated for 1985 is higher than the 1983
mean. Increases in the concentration of dissolved nitrate and nitrite
have been noted in Lake Huron (Moll et al., 1985; Dolan et al., 1983),
Lake Fjrie (Rathke and Edwards, 1985), and Lake Ontario (Neilson, 1983).
Lesht and Rockwell (1987) suggest that nitrate + nitrite nitrogen is
rapidly cycled during the year in the benthic nepheloid layer and in the
sediment-water interface, thus returning to the water column inorganic
nitrogen that may have been removed earlier by settling detritus. Loading
of nitrogen from atmospheric sources 1982-1985 (Klappenbach, 1986) and
from tributary loads (Lang, 1984) provide sufficient soluble nitrogen
(35000 to 45000 metric tons) to account for the increases.
We also examined summertime epilimnion depletion of nutrients using
box plots. Figure 58 shows the distribution of epilimnion silica during
the spring and summer surveys for 1976-1985. This plot allows us to
compare spring and summer concentrations as well as the difference between
the two. The summer decline of epilimnion silica (SiC>2) was more
extensive in 1985, resulting in the lowest observed mean concentration
(0.199 mg/L) in previous years: 1983 (0.326 mg/L), 1976 (0.213 mg/L), and
1977 (0.235 mg/L). The total depletion in 1985 based on the difference
(1.00 mg/L) between observations made during the spring and summer surveys
is also greater than any of the previous years and greater than in 1984
where it was the largest previously observed depletion (0.973 mg/L). The
spring surveys in 1984 and 1985 were conducted earlier in the thermal
cycle than the 1983 or earlier surveys reported here. The 1985
stratified season was somewhat longer than in 1984 which may account for
-------
145
O)
3.0
O
— O
5°
+ O
S
"39
"73
"73
---&---
"61
"51
1976
1977
1983
1984
1985
Figure 57.
I
O)
E
J-
c7>
XI
M
b
Box plot comparison of spring dissolved nitrate+nitrite
nitrogen concentrations in the southern basin of Lake
Michigan, 1976-1985. The values shown for 1976 and 1977
intensive surveys represent stations with depths of 80 meters
or greater.
73
y ffr-i
33
SP76 SU76 SP77 SU77 SP83 SU83 SP84 SU84 SP85 SU85
Figure 58. Box plot comparison of epilimnion depletion of dissolved
reactive silica in the southern basin of Lake Michigan, 1976-
1985. The values shown for 1976 and 1977 intensive surveys
represent stations with depths of 80 meters or greater.
-------
146
the greater epilimnetic depletion. However, the magnitude of the decline
in 1984 and 1985 is less than the 1.3 mg/L decline reported by Schelske et
al. (1983) as typical of Lake Michigan in the late 1960s and early 1970s.
Nitrogen depletion in the epilimnion is considered to be an
indication of eutrophication (Schelske and Roth, 1973) since nitrogen
depletion increases with eutrophication. Figure 59 shows the distribution
of epilimnion nitrate + nitrite during the spring and sunnier for the
surveillance years since 1976. The levels of spring nitrate + nitrite
nitrogen have increased since 1976 through 1984 and, similarly, summer
nitrate + nitrite nitrogen through 1984. The 1985 summer concentration
levels are lower than 1984 and are similar to the 1983 concentration
levels. The difference between spring and summer concentration levels in
1985 was the largest in the last three years. This would appear to be a
contradiction to the phosphate limitation model, however, this may be
related to the longer stratification period in which greater depletion of
the isolated epilimnetric waters could occur.
One measure of water quality in Lake Michigan that made dramatic
changes in recent years (1976-1984) was summertime Secchi depth. This
parameter may be affected by transient events that affect the clarity of
the surface waters. The increasing clarity observed (Figure 60) through
1984 was reversed in 1985. To a certain extent, the increase in Secchi
depth reflects a decline in the summertime phytoplankton population that
has been observed in Lake Michigan (Kitchell et al., 1988). The causes of
the apparent phytoplankton decline are, as yet, uncertain.
Lake Huron
The most recent intensive survey of Lake Huron was conducted in 1980.
Two reports have been written describing the results of that survey:
Dolan et al., (1983) and Moll et al., (1985). Both of these studies
include comparisons of the 1980 survey data with earlier surveys; Dolan et
al. concentrating on comparison with data collected in 1971, and Moll et
al. including data collected since 1954 with emphasis on changes since
1974. In general, the two studies are in agreement in their
conclusions, although some differences in technique and detail exist.
-------
147
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+ o
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"o
Z o .
o _
q •
d -
'73
'51
37
32
33
SP76
SU76 SP77 SU77 SP83 SU83 SP84 SU84 SP85 SU85
Figure 59.
Box plot comparison of epilimnion depletion of dissolved
nitrate+nitrite nitrogen in the southern basin of Lake
Michigan, 1976-1985. The values shown for 1976 and 1977
intensive surveys represent stations with depths of 80 meters
or greater.
q
(N -
Q_ CO
0)
Q
Lc
o
(J
o>
"to
o
o J
1976
1977
1983
1984
1985
Figure 60.
Box plot comparison of surnner Secchi depth in the southern
basin of Lake Michigan, 1976-1985. The values shown for 1976
and 1977 intensive surveys represent stations with depths of
80 meters or greater.
-------
148
Do Ian et al. found that there had been little apparent change in
total phosphorus concentration from 1971 to 1980 but that concentraions of
nitrate + nitrite nitrogen and dissolved reactive silica were
significantly (alpha = 0.05) higher in 1980 than they were in 1971. This
comparison was based on "only those stations that were uniformly sampled
in both years" and on spring surface values.
Moll et al. report that 1980 concentrations of total phosphorus and
dissolved reactive silica were less than those reported in 1974, and
nitrate + nitrite concentration was greater in 1980 than in 1974. In the
longer term, however, Moll et al. found that the pattern of changes for
about one-half of the parameters they studied was curvilinear or
oscillatory, showing the complexity involved in attempting to determine
unequivocal water quality trends from historical data.
The approach taken as part of the present study is similar to that
adopted by Do Ian et al. in which a year-against-year comparison is made
using similar subsets of data. This approach was not taken in preference
to the techniques used by MDll et al., but only because of its relative
simplicity and aptness to the data collected in 1983 through 1985. Table
37 shows the data used by Dolan et al. for inter-year comparisons
recalculated to correspond to the station subset used in 1983 through
1985. These data are plotted in Figures 61 to 64. Two-sided t-tests were
used to examine the differences in nutrient concentrations from 1983
through 1985. (The t values and degrees of freedom calculated all for
1983-1985 comparisons are shown in Table 39.) Based on these subsets,
total phosphorus concentration in Lake Huron appears to have increased
significantly (alpha = 0.05) from 1971 to 1980 and to have decreased
significantly from 1980 to 1983 and again in 1984 to 1985. There were no
significant changes from 1983 to 1984. Figure 61 shows that the mean
spring surface concentration of total phosphorus in Lake Huron has moved
downward since 1980.
-------
149
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LAKE HURON SPRING SURVEY
SURFACE SAMPLES
i
,14°
H9b
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-29
, M18
1 j 20
aEnvironment Canada (EC) surveys
ku.S. and EC joint surveys
i . , . . i . , , . i
1970
1975
1980
YEAR
1985
Figure 61. Total phosphorus (mean + standard deviation, n) in the surface
waters of Lake Huron, spring 1971 to 1985.
en
300
O
o
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00
CO
250
LAKE HURON SPRING SURVEY
SURFACE SAMPLES
19
I-
aEnvironment Canada (EC) surveys
bu.S. and EC joint surveys
1970
1975
1980
YEAR
r29
1985
Figure 62. Dissolved nitrite+nitrate nitrogen (mean + standard deviation,
n) in the surface waters of Lake Huron, spring 1971 to 1985.
-------
150
Z..U
CM
O
CO
I
en
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< 1.5
O
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LAKE HURON SPRING SURVEY
SURFACE SAMPLES
ii igb
1 14°
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aEnvironment Canada (FjC) surveys
'-'U.S. and EC joint surveys
i i > i 1 i ... 1 ,,
1970 1975 1980
-•19
I29" £20
J-
. . i
1985
YEAR
Figure 63. Dissolved reactive silica (mean + standard deviation, n) in
the surface waters of Lake Huron, spring 1971 to 1985.
The rate of increase of nitrate + nitrite calculated here (3.9 ug-
N/L) , assuming a linear increase from 1971 to 1985, is less than that
calculated by Dolan et al. (1983) (5.4 ug-N/L). The measured increase
from 1983 to 1984 was 4.0 ug-N/L, although we observed a decrease between
1984 to 1985. This behavior is not unexpected given that soluble nitrogen
is not a conservative substance and the ambient concentration is a
function of nutrient uptake as well as loadings. The surface data plotted
in Figure 62 show a gradual increase in nitrate + nitrite concentration.
Silica concentration (Figure 63) also seems to have increased since
1971, although the rate of increase has not been constant during the
period 1971-1985. When data from years between 1971 and 1980 were
included in the analysis by MDll et al. (1985) silica concentration
appears to have peaked in 1974 and to have declined from 1974 to 1980.
-------
151
R"
CM
O 1.8
CO
CH 1-6
E
O
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1.4
CO 1.2
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i i i i i i i
JFMAMJJASOND
Month
Lake Huron
a 1971 -Environment Canada (EC)
o 1980_-EC &_USEPA
A 1983 -USEPA
v 1985 -USEPA
Figure 64. Seasonal dissolved reactive silica (mean) in the surface
waters of Lake Huron - 1971, 1980, 1983, and 1985. After
Lesht and Rockwell, 1985.
In more recent years, soluble reactive silica levels are generally
seen to be increasing throughout the annual cycle (Figure 64) , with the
exception in surrmer 1985 when a longer stratification period may have
permitted greater depletion in surface concentrations.
Lake Erie
Considerable historical information exists for Lake Erie, much of
which has been sunmarized in a series of reports by the Center for Lake
Erie Area Research (CLEAR) of the Ohio State University and in a review of
water quality trends in Lake Erie with emphasis on the 1978-1979 intensive
survey (Rathke and Edwards, 1985). This document, as well as the CLEAR
reports by Fay and Herdendorf (1981), Fay et al. (1982), Herdendorf
(1984), and Fay and Rathke (1987) were used as the source of historical
data for Lake Erie used in comparisons with the 1983 through 1985
surveillance results presented here.
-------
152
Although the data reports presented by CLEAR are extensive, only
average values, rather than raw data, are presented. Therefore, only
limited comparisons with data from the current program were conducted.
The approach taken here is to use averages of the 1983 through 1985 data
that are thought to be at least generally comparable to those presented in
the CLEAR data reports rather than to recalculate the historical values to
account for varying station location and survey times.
Annual average values of total phosphorus, nitrate + nitrite
nitrogen, and chlorophyll-a concentrations in Lake Erie are shown in
Tables 45 to 47. The data are separated into the western, central, and
eastern basins, corresponding to the usual lake division based on
bathymetry. The mean of the 1985 data for each basin has been appended to
the means for the years 1970-1982 already compiled by Herdendorf (1984)
and updated by Lesht and Rockwell (1985 and 1987) for data collected in
1983 and 1984. Graphic representations of the data (also after
Herdendorf, 1984) are presented in Figures 65 through 73, which show the
mean + one standard error and the maximum and minimum of the survey-
averaged values.
Differences between the total phosphorus values plotted in Figure 57
and those listed in Table 45 for the years 1979 and 1982 result from
editing of the spring survey data to eliminate unrepresentative, storm-
dominated values in the western basin data. The data plotted in Figures
65 through 67, therefore, are the more accurate estimates of annual
average conditions in Lake Erie.
The general trend seems to be toward lower concentrations of total
phosphorus. Although there is considerable variability in the data, all
of the annual average values recorded since 1980 are lower than the peak
values reached during the mid-1970s. In the western basin, the average
(edited) values have declined for five consecutive years. In the central
basin the average values have decreased in four of the last five years.
These declines may be explained partially by increased water levels in
the Lake Erie although the relationship between such hydrologic factors
and in-lake nutrient concentrations is not clear.
-------
Table 45. late Erie total phospJnorus concentrations, 1970 -1985.a
Vfestem Basin Central Basin Eastern Basin
Year
1970
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985b
1985C
Min.
(ug/L)
33.4
21.7
22.9
32.4
29.5
33.9
—
19.1
17.7
24.1
23.2
22.6
14.8
17.9
—
Max.
(ug/L)
60.0
48.4
45.9
56.6
67.0
53.3
—
98.0
37.7
55.3
139.7
36.5
29.7
32.6
—
Msan
(ug/L)
44.6
34.7
35.1
42.3
44.9
40.7
—
33.9
28.8
36.7
Std.
error
(±)
3.0
6.9
3.6
3.5
6.7
6.3
—
8.2
2.2
3.1
46.9 15.7
28.1
23.7
23.6
—
4.2
3.0
4.6
—
Surveys
(nuirber)
10
3
6
6
5
3
—
9
9
9
7
3
3
3
—
Min.
(ug/L)
11.6
14.3
13.6
14.6
16.5
12.2
12.0
10.0
4.0
13.4
10.4
10.0
9.5
11.8
9.0
'Max..
(ug/L)
36.0
25.6
20.1
31.7
28.8
33.1
15.7
18.4
23.2
26.0
34.8
22.9
21.7
21.4
25.2
Mean
(ug/L)
20.5
18.5
16.8
20.3
22.5
24.1
14.2
13.4
13.9
19.0
16.3
15.5
14.3
15.0
14.8
Std.
error
(+)
2.5
3.6
1.1
2.8
2.3
3.1
0.5
0.9
2.4
1.4
1.6
3.8
3.8
3.2
2.3
Surveys
(number)
10
3
6
6
5
7
6
8
9
9
7
3
3
3
8
Min.
(ug/L)
8.8
11.8
7.9
14.1
—
13.0
9.9
5.2
9.3
—
—
8.9
10.6
6.3
7.9
Max.
(ug/L)
30.9
68.8
66.8
42.9
—
22.9
16.5
18.6
23.7
—
—
12.2
15.9
15.3
11.7
Mean
(ug/L)
17.5
31.1
20.8
27.6
—
18.3
13.0
10.8
13.8
—
—
10.9
13.3
11.0
10.0
Std.
error
(+)
2.2
11.3
2.8
4.1
—
2.1
1.0
2.4
2.6
—
—
1.0
1.5
2.6
0.7
Surveys
(number)
10
4
4
5
—
4
6
5
5
—
—
3
3
3
5
aAfter Herdendorf, 1984.
^Inis study.
cFay and Rathke, 1987
"-" indicates data not available.
en
GO
-------
Table 46. Lake Erie nitrate + nitrite nitrogen ooncentrations, 1965 - 1985.a
Western Basin
Stfl. Stfl.
Min. Max. Mean error Surveys Min. Max. Mean error Surveys
Year (ug/L) (ug/L) (ug/L) (+) (number) (ug/L) (ug/L) (ug/L) (+) (number)
1965 — — 120 — — — — go— _
1970 53 465 213 47 10 18 135 79 13 10
1973 _____ __ __ _
1974 111 644 275 82 6 46 263 142 30 6
1975 129 575 290 66 6 101 195 142 15 6
1976 _____ __ __ _
1977 _____ __ __ _
1978 42 727 290 86 8 88 238 168 22 7
1979 98 796 368 101 8 68 163 120 12 8
1980 _____ __ __ _
1981 430 1,149 742 98 9 143 369 220 24 9
1982 107 625 336 87 7 124 307 205 25 7
1983 221 494 321 87 3 112 177 147 19 3
1984 314 817 502 159 3 128 328 219 58 3
1985 181 725 446 157 3 128 209 178 25 3
i-ooL.ciii octajji
Std.
Min. Max. Mean error Surveys
(ug/L) (ug/L) (ug/L) (+) (number)
— — 90 — —
57 172 113 12 10
— — — — —
— — — — —
— — — — —
— — — — —
— — — — —
156 232 180 11 7
117 210 164 12 8
— — — — —
— — — — 9
— — — — —
193 238 219 13 3
218 234 226 5 3
205 287 255 25 3
fjl
Herdendorf, 1984.
"-" indicates data not available.
-------
liable 47. Late Erie <±tlorqpiTyll--a concentrations, 1970 - 1985.a
Western Basin
Year
1970
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985b
1985°
Std.
Min. Max. Mean error Surveys
(ug/L) (ug/L) (ug/L) (+) (nunfcer)
3.3
8.3
8.8
4.7
6.4
6.5
5.2
4.6
4.2
4.5
3.1
4.8
3.6
1.7
—
19.3
12.0
17.1
21.1
16.9
15.1
17.8
17.5
12.8
13.0
16.7
5.5
7.3
10.8
—
8.6
10.7
13.4
13.7
12.4
10.8
12.5
11.5
8.4
8.3
8.4
5.2
5.4
5.8
—
2.7
1.2
1.4
2.4
2.1
4.3
1.5
1.7
1.0
0.8
2.1
0.2
1.1
2.7
—
10
3
6
6
5
2
8
7
9
9
7
3
3
3
—
Min.
(ug/Q
2.5
2.4
2.4
2.7
2.5
2.3
2.9
2.5
1.5
2.1
1.5
2.8
1.2
2.5
1.1
Central Basin
Max.
(ug/L)
9.2
7.9
9.4
10.0
8.5
6.0
8.3
7.9
4.6
7.1
5.6
5.7
6.6
3.2
5.9
Std.
Mean error Surveys
(ug/L) (+) (nurrber)
4.5 0.7
4.6 1.7
4.2 1.1
5.9 1.1
5.2 1.1
4.0 0.5
5.2 0.7
5.1 0.6
3.1 0.3
4.9 1.5
3.7 0.6
4.3 0.9
3.7 1.6
2.8 0.2
4.1 1.1
10
3
6
6
5
7
8
7
10
9
7
3
3
3
8
Min.
(ug/L)
1.4
2.8
3.3
2.5
—
2.0
1.7
1.4
1.2
—
—
1.2
0.6
0.4
0.9
Eastern Basin
Max.
(ug/L)
5.4
6.6
7.1
5.9
—
4.4
5.4
3.9
3.6
—
—
2.5
1.8
0.9
1.4
Std.
Mean error Surveys
(ug/L) (+) (number)
3.3 0.4 10
5.1 0.9 4
5.1 0.5 6
3.6 0.6 5
— — —
3.0 0.5 6
3.2 0.5 8
2.7 0.4 5
1.9 0.4 6
— — —
— — —
1.9 0.4 3
1.4 0.4 3
0.7 0.2 3
1.1 0.5 5
en
en
aAfter Herdendorf, 1984.
^This study.
cFay and Rathke, 1987.
-------
156
C7>
80
70
60
50
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CL
CO
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0
Figure 65.
Lake Erie - Western Basin
J L
40
25
20
Q.
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Q_
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Figure 66.
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85
Year
Total phosphorus in the western basin of Lake Erie - 1970 to
1985. Data are annual averages of survey averages. Plots
show mean, maximum, minimum, and one standard error about the
mean with the number of surveys contributing to the average.
After Herdendorf, 1984.
Lake Erie — Central Basin
• 3
1
1
.1°
r3"
1 [
1 t
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 85
Year
Total phosphorus in the central basin of Lake Erie - 1970 to
1985. See Figure 67 for footnote descriptions. After
Herdendorf, 1984.
-------
157
80
^ 70
5 60
¥ 50
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CL
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Lake Erie — Eastern Basin
Figure 67.
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 85
Year
alncludes winter results and spring-1 and spring-2 as
separate surveys for 1984.
tThis study.
cFay and Rathke, 1987.
Total phosphorus in the eastern basin of Lake Erie - 1970 to
1985. After Herdendorf, 1984.
The determination of phosphorus trends in Lake Erie is made more
difficult by the fact that both the western and central basins of the
lake are relatively shallow and the bottom sediments are frequently
subject to physical resuspension. Furthermore, anoxic regeneration of
phosphorus from the sediments usually occurs during the late summer in the
central basin. Thus the bottom sediments act as an uncontrollable
phosphorus source with the potential to mask any changes in water column
concentration that may result from reductions in phosphorus loading.
Total phosphorus data from the eastern basin are more sparse than
from the western and central basins but seem to confirm the pattern shown
by the western and central basin annual averages. The 1985 average was
lower than all previously recorded values except the 1979 and 1983
averages. Although the phosphorus concentration increased in 1984, the
-------
158
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1100
^ 1000
5 900
^ 800
I 700
:£ 600
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+ 400
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2 200
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Lake Erie - Western Basin
-
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70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85
Year
Figure 68. Nitrate + nitrite nitrogen in the western basin of Lake Erie
- 1970 to 1985. After Herdendorf, 1984.
400
350
250
:t± 200
"o 100
i_
-*•;
'Z 50
I I I
Lake Erie - Central Basin
I I I I I I 11 1
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85
Year
Figure 69. Nitrate + nitrite nitrogen in the central basin of Lake Erie
- 1970 to 1985. After Herdendorf, 1984.
-------
159
400
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s[ 300
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0)
.-£ 200
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+ 150
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"o 100
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Lake Erie - Eastern Basin
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85
Year
Figure 70. Nitrate + nitrite nitrogen in the eastern basin of Lake Erie
1970 to 1985. After Herdendorf, 1984.
level has returned to near the minimum levels observed earlier. The
eastern basin total phosphorus concentration remains considerably lower
than either the central or western basin concentrations. Fay and Rathke
(1987), using a more extensive 1985 data set, show concentration levels
that were lower in both the central and eastern basins than found in this
study. Given the large variance in the data, the small concentration
declines recorded are not statistically significant. However, the recent
lower levels both for annual means, maximums, and miniitiums indicate that
there has been some improvement in Lake Erie water quality with respect to
phosphorus since the late 1970s.
Herdendorf (1984) reports that nitrogen (primarily nitrate +
nitrite) is the only major dissolved nutrient to have shown a dramatic
increase in concentration in Lake Erie over the last decade (1970-1980).
Table 46 and Figures 68 through 70 show the annual average values of
nitrate + nitrite nitrogen concentrations for the years 1965-1985. The
increase noted from 1965 to 1982 has not continued in the western and
-------
160
Lake Erie - Western Basin
Figure 71.
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85
Year
ChloroFJiyll-a in the western basin of Lake Erie - 1970 to
1985. After Herdendorf, 1984.
cr>
12
10
8
D
=L 6
_O
6 2
0
10
Lake Erie - Central Basin
6
10
I I
I I I I
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85
Year
Figure 72. Chlorophyll-a in the central basin of Lake Erie - 1970 to
1985. After Herdendorf, 1984.
-------
161
cn
12
10
8
a
=L 6
_c
CL
§ 4
6 2
0
Figure 73.
Lake Erie — Eastern Basin
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85
Year
Chlorophyll-a in the eastern basin of Lake Erie - 1970 to
1985. After Herdendorf, 1984.
central basins. Eastern basin nitrate + nitrite nitrogen concentrations
nave averaged 233 + 19 ug/L during 1983 to 1985. This represents
a statistically significant (alpha=0.05) increase over the levels of 172
+ 8 ug/L observed during 1978-1979. Although both the western and central
basin concentrations were higher than in 1983, only the eastern basin
shows year-to-year increases in concentration (Figure 70). The 1983
concentrations were lower than for the two previous years (1981 and 1982).
The 1983 values were similar to those observed between 1973 and 1980.
One consequence of high nutrient concentrations in Lake Erie is high
algal productivity. Chlorophyll-a concentrations were much higher in
1985 in the western and central basin than in the eastern basin or in
either of the other lakes sampled in 1984. Although again not
statistically significant, year-to-year chlorophyll-a trends in both the
western and eastern basins of Lake Erie seem to be downward (Table 47 and
Figures 71 to 73). When analyzed on the basis of 5-year averages,
Herdendorf (1984) found that concentrations of chlorophyll-a in all three
basins were declining at statistically significant levels.
-------
162
Anoxia has been a persistent problem in Lake Erie's central basin
hypolimnion (Table 48). Dissolved oxygen concentrations typically decline
during the year, reaching a miniinum in August or September (Herdendorf,
1984; Lesht and Rockwell, 1985 and 1987). Anoxic conditions (0.25 mg/L
DO, n=l) were observed in the sunnier survey in 1985 in the nepheloid layer
(Table 24).
DiToro and Connolly (1980) developed a simple, empirical method of
relating basin mean values of hypolimnetic dissolved oxygen concentration
to the occurrence of anoxia. Their method was developed to permit
calculation of basin wide anoxic conditions using large-scale
eutrophication models. The method is based on the assumption that the
basin sample mean value of dissolved oxygen concentrations will decline,
more or less proportionately, as absolute concentrations in the basin
decline. Therefore, at some sample mean value, which is determined
empirically, anoxic conditions, defined as dissolved oxygen concentration
below 0.5 mg/L, will occur somewhere in the basin. Using this method, for
the hypolimnion (17-22 meters) we estimate that 60% the central basin
hypolimnion was anoxic during the second survey (summer) of 1985.
Another statistical method relates the probability of anoxia to total
phosphorus concentration, Lake Erie water level, and hypolimnion
temperatures El-Shaarawi (1984b). Using the data collected in 1985, this
model predicts a 70% probability of anoxia in the central basin
hypolimnion.
In addition to the availability of nutrient and dissolved oxygen
data, a fairly complete record exists for chloride concentration and
specific conductance in the central basin of Lake Erie. In Figures 74 and
75, the 1985 annual average values for these parameters have been appended
to those originally compiled by Fay et al. (1982) for the years 1966-1980,
and updated by Lesht and Rockwell (1985 and 1987) for 1983 and 1984.
Chloride concentrations in the central basin of Lake Erie have been
declining steadily since the late 1960s. Examination of chloride loading
data calculated by Sonzogni et al. (1983) shows a decline in chloride
loads to Lake Erie from the Detroit River. Whyte (1985) observed a
-------
Table 48. Lake Erie central basin hypolimnion characteristics, 1970-1985.a
Wbnth/Char ac t er i st ic s
May
Thickness (m)
Dissolved oxygen (mg/L)
Temperature (°C)
June
Thickness (m)
Dissolved oxygen (mg/L)
Temperature (°C)
July
Thickness (m)
Dissolved oxygen (mg/L)
Temperature (°C)
August
Thickness (m)
Dissolved oxygen (mg/L)
Temperature (°C)
1970
3.0
9.6
7.5
3.9
6.5
8.8
3.1
4.0
10.0
2.7
1.2
11.6
1973
-
-
-
—
5.0
4.9
10.3
4.4
1.6
11.9
1974
-
6.2
9.9
8.8
4.6
5.2
11.8
4.3
2.1
13.5
1975
-
7.7
10.0
6.5
6.7
7.8
7.7
6.8
3.3
10.2
1976
-
6.6
9.6
9.4
-
-
—
3.0
0.7
13.7
1977
-
6,8
8.3
10.4
4.6
5.1
11.0
3.0
2.1
11.9
1978
8.6
12.2
7.0
5.6
11.0
9.3
7.1
7.5
12.5
5.5
5.4
11.5
1979 1980
5.6
12.0
9.8
7.3
9.7
6.7
4.4 6.2
7.2 7.8
14.0 12.7
5.8
4.5
13.1
1981
-
7.4
9.4
9.1
5.2
7.7
9.9
4.3
2.2
12.8
1982
5.7
11.0
6.4
3.9
8.3
8.2
4.7
5.2
10.8
4.0
2.7
11.4
1983 1984 1985
- - -
- - -
- - -
— — —
_ _ _
_ _ _
— — —
5.4 4.3 1.6
3.7 3.9 1.3
10.7 10.5 14.2
cr>
CO
aAfter Henderdorf, 1984.
"-" indicates data not available.
-------
164
25
en
O 20
I
O 15
10
Figure 74.
Figure 75.
LAKE ERIE CENTRAL BASIN
ANNUAL AVERAGE VALUES
1965
1970
1980
1985
1975
Year
Chloride in the central basin of Lake Erie - 1966 to 1985.
Data represent survey mean values + standard deviation from
periods of isothermal lake conditions (March-May and October-
December) .
340
1* 320
(/5s
^ 300
t
O 280
O
8 260
. *
LAKE ERIE CENTRAL BASIN
ANNUAL AVERAGE VALUES
*
i
1965
1970
1975
Year
1980
1985
Specific conductance in the central basin of Lake Erie - 1966
to 1985. Data represent survey mean values + standard
deviation from periods of isothermal lake conditions (March-
May and October-December) .
-------
165
decreasing chloride trend at municipal inlets ranging from 0.47 to 0.88
mg/L/year (mean, 0.7 mg/L/year) for the period between the late 1960s and
the early 1980s. Annual mean values of chloride concentrations from
surveys conducted during isothermal lake water periods (March to May and
October to December) are shown in Figure 74. The chloride decline over
the last two years is consistent with the declines observed by Whyte
(1985).
As is expected, annual average specific conductance (Figure 75) is
well correlated with chloride concentration. Although detailed data are
not available for all of the other major dissolved solids, the decline in
specific conductance would seem to indicate overall reduction in total
dissolved solids over the period of record as well.
COMPARISON WITH EUTROPHICATION MODELS
Several types of numerical models have been developed to investigate
some of the processes affecting nutrient-based eutrophication in the Great
Lakes. These models range from simple single-variable, mass-balance
models (Chapra, 1977; Lesht, 1985) to complex dynamic models involving
many variables (Thomann et al. , 1975; DiToro and Connolly, 1980; DiToro
and Matystik, 1980; Rodgers and Salisbury, 198la). They have been widely
applied to such problems as phosphorus loading and designing optimal
nutrient-control strategies to achieve specific water quality objectives.
All of these models were developed using field data for specification
of numerical coefficients. To assess the validity of the models and to
evaluate their output, frequent comparison with field data is necessary.
Indeed, one of the purposes of the Great Lakes Surveillance Program, as
defined in Annex 11 of the 1978 Water Quality Agreement is to "provide
information which will assist in the development and application of
predictive techniques." This section presents the results of a study in
which water quality predictions made using two types of numerical models
were compared to surveillance data, including some of the results of the
1985 survey. In our reports on the 1983 and 1984 surveillance programs
(Lesht and Rockwell, 1985 and 1987) the output of the models was compared
to surveillance data and found to generally reflect the decreasing or
-------
166
stable trends in total phosphorus concentration observed in the
surveillance data.
The reader should understand that numerical models are necessarily
idealized conceptualizations of the processes that they are intended to
represent. As such, the models are limited by their structure and by the
assumptions that were made when the models were developed. Field data,
on the other hand, are only samples of the integrated result of both the
modeled processes and other processes, not modeled, that may or may not
be significant. Therefore, comparisons must be conducted with the
understanding that both the model output and the surveillance data are
only iirperfect representations of the true state of the lakes.
Since a major goal of the overall surveillance effort is to assess
the effectiveness of remedial measures, the following discussion is
concerned with the response of the lakes to external phosphorus loading
control efforts. The basic questions to be answered are: (1) what lake
responses to phosphorus loading reductions do the models predict and (2)
are those responses in agreement with the surveillance data. The
surveillance data will be examined with two types of models, one a
simple, multi-segment, mass-balance model for total phosphorus (Chapra,
1977), and the other a dynamic eutrophication model relating several
water-quality variables to phosphorus loading (DiToro and Connolly, 1980;
DiToro and Matystik, 1980; Rodgers and Salisbury, 1981a).
Great Lakes Mass Balance Model
The Great Lakes Mass Balance (GLMB) model is an elementary, multi-
segment, mass balance model of total phosphorus concentrations (Chapra,
1977). The Great Lakes are simulated as eleven segments. The GLMB model
treats each segment as a completely mixed reactor connected to adjacent
segments via turbulent transport and/or advective flow. Total phosphorus
concentration is assumed uniform throughout each segment. Concentration
changes occur instantaneously on an annual temporal scale. The GLMB
model computes annual average total phosphorus concentrations for each
segment.
-------
167
The model may be represented as:
k 1
Vi(dPi/dt) = Wj. - (Qi + ViA-^Pi + £(QjPj) + ^(Eij(Pi - Pj)) (6)
j=l j=l
where for segment i and adjacent segment j, V is the volume, P is the
total phosphorus concentration, W is the external total phosphorus
loading, Q is the advective flow rate, v is the net apparent settling
velocity of total phosphorus, A is the surface area, and E is the
turbulent exchange rate. The GOXB model was solved in full time-
dependent form using the technique presented by Lesht (1985).
As can be seen (equation 6), the model is driven by external total
phosphorus loading (W) to each model segment (i). Annual estimates
of total phosphorus loadings to the Great Lakes are compiled by the
International Joint Commission (IJC) and periodically by other agencies.
Total phosphorus loading estimates for each of the Great Lakes for 1974-
1984 (and partial 1985) by the IJC, Great Lakes Water Quality Board,
Surveillance Subcommittee Reports (IJC, 1976b, 1977, 1978, 1979, 1981,
1984 and personal communication, J. Clark, IJC) are listed in Table 49.
For the GLMB model these IJC loading estimates were primarily used. For
the Lake Erie segments, Army Corps of Engineers, Buffalo District
estimates were used for years 1974 to 1980 (Salisbury et al. , 1984;
Yaksich et al., 1982) since the authors felt that these estimates better
reflect total phosphorus trends in the observed data. For the unknown
categories in 1985 (Table 49), 1984 estimates were used. Each total load,
without upstream load, was divided into subbasin loads based on ratios
used by Chapra and Sonzogni (1979). The resulting loads used in the GLMB
model are shown in Table 50.
The GLMB model also requires data to represent segment volumes,
surface areas, flow rates, turbulent exchange rates, total phosphorus
initial conditions and net apparent settling velocities. For most input
parameters constant values used by Chapra and Sonzogni (1979) were used
for the 12-year modeling period of 1974 to 1985 (Tables 51 and 52). Most
values represent Great Lakes conditions of the mid-1970s. Flow rates
-------
168
Table 49. Total phosphorus loadings (metric ton/year) to the Great Lakes. Loads are reported for Water Years
1974-1984 (partial 1985), (IJC estimates, except as noted).
s-
u
P
e
r
i
o-
r
M-
i
c
h
i
g
a-
n
H
u
r
0
n
E
r
i
e
0
n
t
a
r
0
1
2
Discharge Source
Direct Industrial
Direct Municipal
Tributary (Monitored)
Tributary (Unmon. Adj)
Atmospheric
Total (target=34003)
Direct Industrial
Direct Municipal
Tributary (Monitored)2
Tributary (Unmon. Adj)
Atmospheric
Total ( target=56003 )
Direct Industrial
Direct Municipal
Tributary (Monitored)
Tributary (Unmon. Adj)
Atmospheric
Subtotal
Upstream (Sup/Mich)4
Total (target=43603)
Direct Industrial
Direct Municipal
Tributary (Monitored)
Tributary (Unmon. Adj)
Atmospheric
Subtotal
Upstream (L. Huron)
Total (target=110003)
Direct Industrial
Direct Municipal
Tributary (Monitored)
Tributary (Unmon. Adj)
Atmospheric
Subtotal
Upstream (L. Erie)
Total (target=70003)
Figures for 1983 and 1984
1974
93
114
1995
800
3002
45
1088
4967
1000
7100
0
141
3669
620
4430
657
5087
126
6977
8963
560
16626
1080
17706
1185
1858;?
20215
350
4347
56136
9960
1975 1976
97 102
62 59
1397 1708
592
800 1089
2357 3550
61 32
1067 1040
4231 3179
715
1000 1690
6359 6656
129 31
120 123
2330 2490
439
620 1062
3199 4145
657 657
3856 4802
68 275
6632 5731
4903 5553
1658
560 1119
12163 14336
1080 1080
13243 15416
187 80
3091;? 2039
21365 3254
1236
350 473
5763 7082
56136 56136
11376 12695
are DRAFT estimates
r-f 1 Q*7/t =n^l 1 QTt;
1977
108
64
1625
775
1089
3661
50
660
1967
299
1690
4666
181
162
1359
342
1062
3106
657
3763
135
5697
5285
1260
1119
13496
1080
14576
124
2470
2413
557
623
6187
2748
8935
; IJC
1978
73
123
1480
793
3521
5990
46
494
3540
475
1690
6245
1
169
1700
608
2120
4598
657
5255
191
4440
10037
2804
879
18351
1080
19431
117
1913
2297
674
764
5765
3782
9547
1979
45
159
1479
939
3997
6619
13
371
3690
616
2969
7659
6
144
1363
380
2331
4224
657
4881
50
2840
5323
1098
1550
10861
1080
11941
103
2316
2509
691
311
5930
3058
8988
1980
42
143
1109
1121
3997
6412
37
431
2381
756
2969
6574
2
121
1553
643
2331
4650
657
5307
82
2370
8260
1513
1550
13775
1080
14855
62
2060
2383
676
311
5492
3087
8579
1981
36
116
1259
1495
506
3412
42
243
2966
534
306
4091
3
141
1638
429
613
2824
657
3481
55
1843
5582
1163
729
9372
1080
10452
62
1756
1822
613
328
4581
2856
7437
1982
33
128
1338
1008
653
3160
53
246
2808
671
306
4084
5
113
1921
819
1174
4032
657
4689
67
1388
7483
1671
660
11269
1080
12349
54
1589
2581
737
600
5561
3330
8891
19831
51
82
1470
1156
630
3389
19
349
3005
683
475
4531
2
127
1801
772
847
3549
657
4206
54
1710
5406
1065
362
8597
1080
9677
32
1259
1612
480
181
3564
3116
6680
19841
48
93
1505
1197
797
3640
26
239
2220
520
527
3532
9
152
1427
477
846
2911
657
3568
124
1928
7445
1918
392
11807
1080
12887
40
1423
2361
531
242
4597
3464
8061
1985
1258
33937
2704
40167
2692
41767
48337
6753
111157
121957
1685
39217
73857
anticipates revisions.
.
Target load, 1978 Great Lakes Water Quality Agreement.
4 Upper Lakes Reference Group 1974-1975 estimates for Upstream loads.
L. Ontario 1974 and 1975 Municipal and Tributary loads are 95% of IJC figures for L. Ontario
and St. Lawrence River.
Hydroscience 1974 estimates for Upstream loads.
Figures for 1985 are based on 1984 estimates and 1985 tributary (monitored) estimates.
Source: International Joint Commission, Great Lakes Water Quality Board, Surveillance Subcommittee Reports
-------
Table 50. Annual total phosphorus loadings (metric ton/year) used for the GLMB model, by segment.
Model Lake Lower
Year Superior Green
Bay
Upper Lake Georgian Saginaw Lake Western
Green Michigan Bay Bay Huron L. Erie
Bay
Central Eastern Lake
L. Erie L. Erie Ontario
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
3002
2357
3550
3661
5990
6619
6412
3412
3160
3389
3640
3393
1207
1081
1132
793
1062
1302
1118
695
694
770
600
683
213
191
200
140
187
230
197
123
123
136
106
120
5680
5087
5325
3733
4996
6127
5259
3273
3267
3625
2826
3213
842
608
788
590
874
803
884
537
766
674
553
793
1373
992
1285
963
1425
1309
1442
875
1250
1100
902
1295
2215
1600
2073
1553
2299
2112
2325
1412
2016
1775
1456
2088
13208
12747
12734
12644
7602
6433
5935
5717
6874
5244
7202
6780
4230
3841
3588
4366
5139
5091
3517
2343
2817
2149
2952
2779
2045
1660
2336
2305
998
1423
848
1312
1578
1204
1653
1556
4347
5763
7082
6187
5765
5930
5492
4581
5561
3564
4597
3921
Source: International Joint Commission, Great Lakes Water Quality Board, Surveillance Subcommittee;
Army Corps of Engineers, Buffalo District (1974 to 1980 Lake Erie).
Table 51. Constant parameters used for the GLMB model, by segment.
Lake Lower Upper Lake Georgian Saginaw Lake Western Central Eastern Lake
Earameter Units Superior Green Bay Green Bay Michigan Bay Bay Huron L. Erie L. Erie L. Erie Gntario
Volume (tor3) 11920.0
Surface area (km2) 82100.0
Flow rate (kn^/yr)
Initial TP (1973) (ug/1)
Settling velocity (m/yr)
67.2
4.6
9.8
7.5
953.0
5.4
40.0
12.7
55.4
4846.0
665.0
8.1
3260.0 53537.0 15108.0 1376.0
10.8
15.0
11.2
36.0
8.5*
***
17.9
4.5
12.9
4.7
30.9
13.5
2842.0
43086.0
160.8
5.5
12.6
28.0
274.0
166.0
1631.0
3680.0 15390.0 6150.0 18960.0
171.1
34.7**
10.1
177.5
18.5**
33.6
182.0
20.8*
36.7
211.7
21.0
13.9
Sources: Chapra and Sonzogni (1979); * Rousar (1973); and ** Herdendorf (1984).
*** Variable settling velocity values were used for the L. Michigan segment (see Table 52).
-------
170
Table 52. Turbulent exchange coefficients
used for the GLMB model, by
segment.
Exchange rate
Segments (km3/yr)
Lower Green Bay/
Upper Green Bay 20.0
Upper Green Bay/
Lake Michigan 30.0
Lake Michigan/
Lake Huron • 70.0
Georgian Bay/
Lake Huron 100.0
Saginaw Bay/
Lake Huron 25.0
Western L. Erie/
Central L. Erie 140.0
Central L. Erie/
Eastern L. Erie 490.0
Source: Chapra and Sonzogni (1979).
represent long-term averages. For most model segments the initial
concentrations of total phosphorus are from Chapra and Sonzogni (1979) ;
values used for Lake Michigan and the three basins of Lake Erie were
adjusted to better represent the conditions observed in the early 1970s
(Rousar, 1973; Herdendorf, 1984).
For the Lake Michigan segment annual total phosphorus settling
velocity values were allowed to vary as a function of winter ice cover.
Past modeling efforts have shown the need to increase the apparent
settling velocity by eight-fold during periods of extensive (>30% of
surface area of lake) ice cover (Rodgers and Salisbury, I981a; Lesht,
1984b; Lesht and Rockwell, 1985). For this modeling effort a linear
regression was developed between the winter severity index (WSI) (Quinn et
al., 1978) and the number of days with 30% or greater ice cover (ICD),
determined by planimeter, for the model years 1976-1981 (n=6, r2-0.992):
-------
171
ICD = -18.22(WSI) - 55.16
(7)
The number of days with 30% or greater ice cover was then calculated for
each model year from 1974 to 1985 based on this linear relationship
(equation 7). The settling velocity (v) was increased eight-fold during
the period of extensive ice cover, based on work by Rodgers and Salisbury
(1981a), over the long-term average of 12.4 meter/year (Chapra and
Sonzogni, 1979):
v = 0.237UCD) + 12.4 (8)
The resulting settling velocities, as well as the submodel (equations 6, 7
and 8) input values are shown in Table 53.
Table 53. Data used to represent the total phosphorus
(TP) settling velocity for the Lake Michigan
segment of the GLMB model.
Model
Year
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
Winter
Severity
Index*
-4.9
-3.3
-3.6
-7.7
-6.0
-6.8
-4.0
-5.0
-5.8
-2.2
-4.9
-4.9
Days of
Ice Cover
(planimeter)
7
83
56
70
21
35
Days of
Ice Cover
(linear
regression)
34
5
10
85
54
69
18
36
50
0
34
34
TP settling
velocity
(m/yr)
20.5
13.6
14.8
32.6
25.2
28.8
16.7
21.0
24.3
12.4
20.5
20.5
*WSI Source: Quinn et al. (1978).
Comparison of the GLMB model output to surveillance data; The
surveillance data compared to the GLMB computations were compiled from
several sources. The values for this modeling effort for 1983 through
1985 are annual averages of three or four seasonal volume-weighted means
of individual surveys calculated from GLNPO surveillance data stored in
the U.S. EPA STORE! database. The values for Lake Michigan 1976 and 1977
-------
172
are from Rockwell et al. (1980). Those for Lakes Michigan and Huron 1980
are from Lesht and Rockwell (1985). Lake Erie 1974-1982 values are from
Herdendorf (1984) and Lesht and Rockwell (1987). The surveillance data
are represented as means ± standard errors (when available).
The GLMB model was used to hindcast total phosphorus concentrations
from 1974 to 1985, the period for which total phosphorus loading
estimates are available. The model output illustrates how the lakes
might be expected to respond to recent historical changes in phosphorus
loading. In all five model segments, predicted concentrations of total
phosphorus decreased over the modeled period (Figures 76-80). The
magnitude of the predicted decreases varied from segment to segment, from
less than 1 ug/1 in Lake Huron to more than 20 ug/1 in the western basin
of Lake Erie from the mid 1970s to the mid 1980s. The GLMB model predicts
the decreasing long-term trends observed in the field data very well.
However, short-term (year-to-year) variations of the GLMB model are often
in disagreement with the observed data.
Possible origins of these discrepancies between the GLMB model
predictions and surveillance data include unrealistic model input data, an
overly simplistic model structure, or unrepresentative loading and/or open
lake surveillance data. Most of the model input data parameters were kept
constant over the modeled 12-year period and all of the input parameters
are estimated based, in part, on field data. Perhaps a more rigorous
compilation of the input parameters over the 12-year modeling period
would improve the 12-year hindcast. The structure of the GLMB model is
very simple, by design, and, therefore, should not be expected to exactly
reproduce the annual averages of the surveillance data. The annual
averages of the loading and open lake surveillance data are based on
temporally incomplete records of total phosphorus concentrations with
loading errors as much as 20-30% and open lake data based on only three
survey periods.
For Lake Michigan over the 12-year simulation a decreasing total
phosphorus concentration trend is hindcast by the model and observed in
the surveillance data (Figure 76). Although the substantial 2.5 ug/L
-------
173
10 r Lake Michigan
cn
co
Q.
CO
O
_C
Q_
~0
-t—•
,O
8
o
I
Figure 76.
10
73 74 75 76 77 78 79 80 81 82 83 84 85
Year
GLMB model simulation of total phosphorus in Lake Michigan.
Model results (line) are compared to surveillance data (mean
+ 1 standard error).
_ Lake Huron
CP
CO
o
_c
Q_
Q_
~D
8
0
J I I I I I I I
73 74 75 76 77 78 79 80 81 82 83 84 85
Year
Figure 77. GLMB model simulation of total phosphorus in Lake Huron.
-------
174
eo r Lake Erie - Western Basin
en
50
40
30
Q_
CO
O
20
~D
,"0 10
0
I I I I
I I
Figure 78.
73 74 75 76 77 78 79 80 81 82 83 84 85
Year
GLMB model simulation of total phosphorus in the western
basin of Lake Erie.
30 r Lake Erie - Central Basin
en
en
13
CL
CO
O
_c
Q_
"o
25
20
15
10
0
J I
I I I I I I I I I I
73 74 75 76 77 78 79 80 81 82 83 84 85
Year
Figure 79. GLMB model simulation of total phosphorus in the central
basin of Lake Erie.
-------
175
r- Lake Erie - Eastern Basin
CO
Z3
CL
CO
O
_c
Q_
~0
25
20
15
10
J I i i
J L
J I I L
73 74 75 76 77 78 79 80 81 82 83 84 85
Year
Figure 80. GLMB model simulation of total phosphorus in the eastern
basin of Lake Erie.
decrease in total phosphorus between 1976 and 1977 is underestimated by
the model by approximately 1 ug/L, a decrease is simulated. In the 1980s
the model underestimates the total phosphorus concentration. A better
understanding of the effect of winter ice cover on the settling velocity
of total phosphorus is needed.
For Lake Huron, a slowly decreasing concentration trend
(approximately -0.1 ug/L/yr) is hindcast over the 12-year GLMB model
simulation (Figure 77). The observed data suggests that the rate of
decrease was about two times greater (approximately -0.2 ug/L/yr). The
observed total phosphorus decrease from 1984 to 1985 is not predicted by
the model, nor reflected in the increasing load estimate from 1984 to
1985. Perhaps the settling velocity used for this segment has been
underestimated or loading estimates are in error.
For the western basin of Lake Erie, the 12-year trend simulated by
the GLMB is only grossly in agreement with the surveillance data (Figure
-------
176
78). Extremely high concentrations are predicted and observed during 1975
through 1977 and a rapid concentration decrease is predicted and observed
from 1977 to 1979. However, year-to-year model predictions are not in
agreement with corresponding field data. The observed total phosphorus
concentration increases from 1979 through 1981 and decreases from 1981
through 1985 are not reflected in the GLMB model hindcast. These
disagreements suggest that the total phosphorus loading estimates used do
not reflect observed total phosphorus concentrations. The model assumes
net deposition of phosphorus into the sediments in the western basin which
may not be attained each year due to its shallow nature and storm-induced
resuspension (Lesht and Rockwell, 1985).
For the central basin of Lake Erie, the GLMB model hindcasts the
high total phosphorus concentrations observed from 1975 through 1977 and
the lower concentrations observed from 1978 through 1980 (Figure 79).
For the years 1981 through 1985 the model greatly underestimates the
surveillance data. This discrepancy is, in part, due to the
concentration underestimation in the western basin. Further, the model
does not estimate the impact of in-basin phosphorus loading due to anoxic
sediment release of phosphorus to the water column.
For the eastern basin of Lake Erie over the 12-year simulation, a
decreasing concentration trend is hindcast by the GLMB model and observed
in the surveillance data (Figure 80). The predicted concentrations are,
for the most part, in very close agreement with the field data. The very-
high total phosphorus concentrations observed in 1975 appear to be
anomalous.
In conclusion, the GLMB model has been used to hindcast the total
phosphorus concentrations in the middle Great Lakes. Better agreement
between model results and observations are found in Lake Michigan, Huron
and eastern Lake Erie where effects from the non-modeled processes of
resuspension and anoxic release of phosphorus are less of a factor than
in western and central Lake Erie. Further refinement of the GLMB may
improve the predictive capability of the model. Refinement possibilities
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177
include changes to the model segmentation and to the model coefficients.
The segmentation could be refined to separate the southern and northern
basins of Lakes Michigan and Huron. The current input data set could be
refined to use annually varying parameters to model the net apparent
settling velocity as a function of extensive winter ice cover, and storm-
induced sediment resuspension or anoxic phosphorus release as internal
sources of phosphorus.
Dynamic Nutrient-Phytoplankton WASP Models
The Water Quality Analysis Simulation Program (WASP) (DiToro et al.,
1983) is a flexible modeling framework that has been applied individually
to eutrophication analyses of the middle Great Lakes. Complex, dynamic,
mass-balance models have been developed for Lakes Michigan (Rodgers and
Salisbury, 1981a and b), Huron (DiToro and Matystik, 1980) and Erie
(DiToro and Connolly, 1980). These models simulate several biological
and chemical parameters (Table 54) in multiple segments. WASP treats
each segment as a completely mixed reactor connected to adjacent segments
via dispersive exchange and advective flow. Biological and chemical
parameters interact via empirical kinetics. Parameter concentrations are
represented by non-linear partial differential equations. Concentrations
are assumed uniform throughout each segment; the WASP models compute
average concentrations for each segment. For these model simulations the
concentrations of the water quality parameters were calculated on a
twelve-hour temporal scale.
The WASP models are driven by external loadings of each of the
modeled parameters. For the two phosphorus systems (Table 54), IJC
estimates of total phosphorus loading for 1983 to 1985 (Table 49) were
divided into non-living organic and soluble reactive phosphorus. For the
unknown categories in 1985, 1984 estimates were used. Each total load,
including upstream load, was divided into loads for each model segment.
The resulting loads used in the WASP model are shown in Table 55.
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178
Table 54. Comparison of biological and nutrient state variables
explicitly modeled by title WASP models of Lakes Michigan,
Huron and Erie.
State Variable
Non-diatomaceous chlorophyll-a
Diatomaceous chlorophyll-a
Herbivorous zooplankton
Carnivorous zooplankton
Non-living organic carbon
Non-living organic nitrogen
Non-living organic phosphorus
Non-living silica
Ammonia nitrogen
Nitrite nitrogen
Nitrate nitrogen
Dissolved reactive phosphorus
Dissolved reactive silica
Dissolved oxyaen
Lake Michigan
Model
X
X
X
X
X
X
X
X
X
X
Lake Huron
Model
X
X
X
X
X
X
X
X
X
X
Lake Erie
Model
X
X
X
X
X
X
X
X
X
X
X
X
Total number of state variables 11 8 14
Table 55. Annual total phosphorus loadings (metric ton/
year) used for the WASP models.
Model Lake Lake Lake
Year Michigan Huron Erie
1983 4531 4206 9677
1984 3532 3568 12887
1985 4016 4833 12195
Source: International Joint Commission, Great Lakes
Water Quality Board, Surveillance Subcommittee data.
The WASP models also require data to represent segment volumes,
surface areas, flow rates, dispersive exchange rates, water temperatures,
photoperiod, solar radiation, initial conditions, net apparent settling
velocities, and kinetic rates of the modeled parameters. For most of
these model input parameters the values used in the original calibrated
versions were used herein. These values represent Great Lakes conditions
of the early to mid-1970s.
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179
The selection of initial conditions for the WASP models is extremely
inportant. The results of these models are very sensitive to the initial
conditions used (Lesht, 1984b). Initial conditions should be chosen to
realistically represent concentrations of the model parameters. Initial
1983 conditions are based on data collected during the winter surveys of
1984 and 1985, and on comparisons between model results and spring 1983
survey data. This iterative "tuning" of initial conditions improves the
reliability of the model results by reducing the dependency of model
results on the accuracy of individual survey mean concentrations.
Comparison of WASP model results to surveillance data; WASP model
results for selected parameters from 1983 through 1985 are compared to
data collected for the GLNPO's annual surveillance program begun in the
spring of 1983. These data are reported herein and in the earlier
surveillance reports (Lesht and Rockwell, 1985 and 1987). Survey means
plus/minus one standard error are compared to the WASP model results. The
surveillance data are too sparse temporally to perform a rigorous
comparison to the results of the WASP models.
The WASP model of Lake Michigan was developed by Rodgers and
Salisbury (I981a and 1981b) and was thoroughly investigated by Lesht
(1984a and 1984b). Mass balances are calculated by the model for the
variables shown in Table 54. The model is divided into four segments
representing the epiliinnion (upper 20 meters) and the hypolimnion of the
southern and the northern basins.
The Lake Michigan WASP model, like the GLMB model, can be used to
simulate an accelerated settling of particulates during periods of
extensive ice cover. The effect of this hypothetical, ice cover-
induced, accelerated particulate settling on chlorophyll-a, ortho
phosphorus and total phosphorus concentrations is investigated herein.
Lake Michigan was simulated without and with accelerated settling of
particulates. For one simulation, the settling velocities of the
particulates was increased from 0.2 meters/day to 1.6 m/d for the first
34 days of both 1984 and 1985.
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180
The results of the chlorophyll-a simulations in the epilimnion
segments of both basins of Lake Michigan are compared to chlorophyll-a
surveillance data in Figures 81 and 82. The dashed line displays model
output assuming ice cover-induced accelerated particulate settling. The
solid line displays model output assuming a constant particulate settling
rate. Typically, spring (April and May) survey data are over-predicted by
the model simulations; the model predicts an earlier onset of
phytoplankton growth than is supported by the survey data. The model
predictions for the other seasons are closer to observed data.
Surveillance data are too sparse to support or dispute annual predicted
peaks in chlorophyll-a concentration.
The effect of varying the particulate settling rate appears to be
insignificant for the first year; there is only a small change in the
1984 model results between the two simulations. However, for 1985 the
effect becomes greater. For simulations extending for many years the
results would be expected to continue to diverge.
The results of the total phosphorus simulations in the epilimnion
segments of both basins of Lake Michigan are compared to total phosphorus
surveillance data in Figures 83 and 84. The dashed line displays model
output assuming ice cover-induced, accelerated particulate settling. The
solid line displays model output assuming a constant settling rate. In
the southern basin epilimnion the model output is reasonably close to the
1983 survey data. However, the model predictions for 1984 and 1985
greatly underestimate the survey data. Even by eliminating the
accelerated particulate settling the model underestimates the observed
concentrations.
In the northern basin epilimnion both simulations track observations
better compared to the simulations of the southern basin. In 1984 the
ice cover-induced, accelerated particulate settling simulation predicts
the survey data best. In 1985 the survey data is predicated best by
using the constant settling rate simulation for the entire three years.
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181
< 3
cn
3
o
± 2
>s
Q.
O
_0
JZ
(J
-P 1
0
Southern Lake Michigan Epilimnion
1983 through 1985
_L
JMMJSNJMMJSNJMMJSN
Figure 81. WASP model simulation of chlorophyll-a in the epilimnion of
southern Lake Michigan. Model results using a constant
settling velocity (solid line) and using ice cover-induced
accelerated settling of particulates (dashed line) are
compared to surveillance data (mean + 1 standard error).
4 r
3 -
Northern Lake Michigan Epilimnion
1983 through 1985
cn
s '
D
=L 2 -
D.
_o
JZ
O
-p 1 -
MJSNJMMJSNJMMJSN
Figure 82. WASP model simulation of chlorophyll-a in the epilimnion of
northern Lake Michigan.
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182
10
8
§ 6
CL
I 4
CL
Southern Lake Michigan Epilimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
Month
Figure 83. WASP model simulation of total phosphorus in the epilimnion
of southern Lake Michigan.
10
8
co e
D 6
i_
O
CL
CO A
O 4
&
Northern Lake Michigan Epilimnion
1983 through 1985
I \
1 }V
JMMJSNJMMJSNJMMJSN
Month
Figure 84. WASP model simulation of total phosphorus in the epilimnion
of northern Lake Michigan.
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183
These inconsistent results suggest further refinement is needed in
modeling settling rates.
The results of the soluble reactive, ortho phosphorus simulations in
the epilimnion segments of both basins of Lake Michigan are compared to
ortho phosphorus surveillance data in Figures 85 and 86. The dashed line
displays model output assuming ice cover-induced, accelerated particulate
settling. The solid line displays model output assuming a constant
settling rate. In both basins the model predicts the trend found in the
survey data. However, the magnitude is not always predicted. The model
overestimates the extent of the summer depletion in both basins during
each summer for the extent of the simulations. Typically, the model
underestimates the winter peak. There is very little difference in model
results whether the particulate settling rate is constant or time-
variable as a function of ice cover.
The WASP model of Lake Huron was developed by DiToro and Matystik
(1980). Mass balances are calculated by the model for the variables
shown in Table 54. The model is divided into four main lake segments
representing the epilimnion (upper 15 meters) and the hypolimnion of the
northern and southern basins. A fifth segment represents Saginaw Bay.
The Lake Huron WASP model was used to examine the sensitivity of the
output to the amount of phosphorus loadings. Water quality was simulated
using the annual total phosphorus loadings estimated by the International
Joint Commission (Table 55) and, also, using phosphorus loadings at 66.7%
of IJC estimates.
The results of the chlorophyll-a simulations in the epilimnion
segments of both basins of Lake Huron are compared to chlorophyll-a
surveillance data in Figures 87 and 88. The solid line displays model
output assuming IJC phosphorus loading estimates. The dashed line shows
the output assuming 66.7% of the IJC loading level. In general, the
model matches the temporal trend of the survey data, but not the magnitude
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184
4 r
Cn
3
(S)
D
b
en
O
_c
Q.
_
O
Southern Lake Michigan Epilimnion
1983 through 1985
1 ' 0
JMMJSNJMMJSNJMMJSN
Month
Figure 85. WASP model simulation ortho phosphorus in the epilimnion of
southern Lake Michigan.
Northern Lake Michigan Epilimnion
1983 through 1985
CD
a.
c/)
o
_
O
JMMJSNJMMJSNJMMJSN
Figure 86. WASP model simulation ortho phosphorus in the epilimnion of
northern Lake Michigan.
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185
4 r
CD
3
O
=L 2
^
CL
2
_g
JC 1
o
0
Northern Lake Huron Epilimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
Figure 87. WASP model simulation of chlorophyll-a in the epilimnion of
northern Lake Huron. Model results using IJC loading
estimates (solid line) and using 66.7% of IJC loading
estimates (dashed line) are compared to surveillance data
(mean + 1 standard error).
3
D
J= 2
>N
Q.
2
o
:E 1
CJ
o
Southern Lake Huron Epilimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
Month
Figure 88. WASP model simulation of chlorophyll-a in the epilimnion of
southern Lake Huron.
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186
of the concentrations. The WASP model greatly overpredicts the observed
concentrations of chlorophyll-a in the spring (April to May). Lowering
phosphorus loads decreased the magnitude of both the spring and fall
chlorophyll-a concentration peaks, as expected. The effect becomes
greater for each successive peak.
The results of the total phosphorus simulations in the epilimnion
segments of both basins of Lake Huron are shown in Figures 89 and 90.
The solid line displays the model output assuming IJC phosphorus loading
estimates. The dashed line shows the output assuming 66.7% of the IJC
loading level. Both scenarios greatly overpredict observed total
phosphorus concentrations. Further, the temporal trend of the observed
data is not predicted by the model. As observed in the earlier reports
of this annual surveillance program, the epilimnetic depletion of total
phosphorus observed during the summer is not simulated by the WASP model.
The WASP model of Lake Huron apparently does not properly account for the
settling of particulate phosphorus.
The results of the ortho phosphorus simulations in the epilimnion
segments of both basins of Lake Huron are shown in Figures 91 and 92.
The solid line displays the model output assuming IJC phosphorus loading
estimates. The dashed line shows the output assuming 66.7% of the IJC
loading level. The two scenarios differ little. Both scenarios match
the surveillance data in temporal trend and in concentration magnitude.
However, as seen in the chlorophyll-a simulation, the difference between
the two model scenarios becomes more pronounced with each successive
year.
The WASP model of Lake Erie was developed by DiToro and Connolly
(1980). Mass balances are calculated by the model for the variables
shown in Table 54. The model is divided into six epilimnion and
hypolimnion water column segments and four sediment segments. The
western basin is represented by a water column and a sediment segment.
The central basin is represented by an epilimnion, two hypolimnion, and
two sediment segments. The eastern basin is represented by an epilimnion,
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187
10
8
en
i_
o
_c
CL
O
Q_
jg
"o
0
Northern Lake Huron Epilimnion
1983 through 1985
I
JMMJSNJMMJSNJMMJSN
Month
Figure 89. WASP model simulation of total phosphorus in the epiliimion
of northern Lake Huron.
10
8
E 6
b
JC
CL
to 4
O ^
Q.
0
Southern Lake Huron EpSI'ima,
1983 through 1985
FTY
I
on
JMMJSNJMMJSNJMMJSN
Month
Figure 90. WASP model simulation of total phosphorus in the epilimnion
of southern Lake Huron.
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188
cn
3
CO
D
O
.
CO
O
Ql
_
O
Northern Lake Huron Epilimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
Figure 91. WASP model simulation of ortho phosphorus in the epilimnion
of northern Lake Huron.
4 r
CO
L.
o
Q.
CO
O
O
Southern Lake Huron Epilimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
Figure 92. WASP model simulation of ortho phosphorus in the epilimnion
of southern Lake Huron.
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189
a hvpolimnion, and a sediment segment. Exchanges between the water column
and sediment segments are represented in the model.
The Lake Erie WASP model was used to examine the behavior of
chlorophyll-a, total phosphorus and ortho phosphorus in the western basin
and epilimnion segments of the central and eastern basins. Additionally,
dissolved oxygen concentrations in the central basin hypolimnion are
examined. Water quality was simulated using the annual total phosphorus
loadings estimated by the International Joint Commission (Table 55).
The results of the chlorophyll-a simulations in the western basin
and the epilimnion segments of the central and eastern basins of Lake
Erie are shown in Figures 93, 94 and 95. In all three basins, typically,
the observed spring peak of diatomaceous chlorophyll-a is over-predicted
by the model. Further, the model does not simulate a summer peak of non-
diatomaceous chlorophyll-a as seen in the surveillance data and
demonstrated by DiToro and Connolly (1980) in the mid-1970s. These two
inconsistencies are, no doubt, related. Diatomaceous growth is excessive
in the spring, resulting in ortho phosphorus depletion to the extent that
summer growth of non-diatoms is retarded. Perhaps the diatomaceous
growth rate calibrated and verified for the mid-1970s is not appropriate
for conditions in Lake Erie in the mid-1980s. Further research on
phytoplankton growth rates is needed to resolve this issue.
The results of the total phosphorus simulations in the western basin
and the epilimnion segments of the central and eastern basins of Lake Erie
are shown in Figures 96, 97 and 98. In the western basin the model
underpredicts total phosphorus concentrations during 1983. In contrast,
both the magnitude and temporal trend are modeled satisfactorily during
1984 and 1985. The scatter in the surveillance data may be the result of
transient processes not explicitly represented in the model.
In the central basin epilimnion the model tracks the lower total
phosphorus surveillance data throughout the simulation. However, as seen
in the western basin, the variability of the observed data is much
greater than the variability simulated by the WASP model. Again this may
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190
cn
D
14
12
10
8
- c
CL 6
o
I *
O
2
0
Western Lake Erie
1983 through 1985
JMMJSNJMMJSNJMMJSN
Month
Figure 93. WASP model simulation of chlorophyll-a in western Lake Erie.
10
8
cn
-S. 4
2
_g
6 2
Central Lake Erie Epilimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
Month
Figure 94. WASP model simulation of chlorophyll-a in the epiliimion of
central Lake Erie.
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191
10
8
CT>
_
6 2
Eastern Lake Erie Epilimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
Month
Figure 95. WASP model simulation of chlorophyll-a in the epilimnion of
eastern Lake Erie.
be due to the simplified WASP model mathematical structure, which does not
track transient processes.
In the eastern basin epilimnion the model generally underpredicts
total phosphorus concentrations. However, the temporal trend is roughly
simulated. Observed data scatter is much less in the eastern basin than
in both of the other basins of Lake Erie, but is still greater than the
variability of the model predictions.
The results of the soluble reactive, ortho phosphorus simulations in
the western basin and the epilimnion segments of the central and eastern
basins of Lake Erie are shown in Figures 99, 100 and 101. In the western
basin the model reproduces the observed data in 1984 only. The
surveillance data for winter 1984-1985 are extremely low; the model
cannot be expected to simulate this anomalous event. Summer
concentrations are underpredicted by the model, as expected from the
review of problems with the chlorophyll-a simulation.
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192
cn
80
70
60
50
40
CL
CO
O 30
Q_
O 20
? 10
0
Western Lake Erie
1983 through 1985
JMMJSNJMMJSNJMMJSN
Month
Figure 96. WASP model simulation of total phosphorus in western Lake
Erie.
50
40
§ 30
a.
S 20
CL
1 10
Central Lake Erie Epilimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
Month
Figure 97. WASP model simulation of total phosphorus in the epilimnion
of central Lake Erie.
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193
CD
_
O
50
40
30
Q_
8 20
Q_
10
Eastern Lake Erie Epilimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
Month
Figure 98. WASP model simulation of total phosphorus in the epilimnion
of eastern Lake Erie.
In the central basin epilimnion the model does not predict the
temporal trend or magnitudes of ortho phosphorus concentrations. Summer
concentrations are underpredicted by the model. As in the western basin,
this problem may be related to excessive growth of diatoms in the spring.
In the eastern basin epilimnion the model roughly simulates the
temporal trend but not the magnitude of ortho phosphorus concentrations.
Maximum and minimum concentrations are both underpredicted. Perhaps
these results are related to the problem with the excessive growth of
diatoms in the spring.
The results of the dissolved oxygen simulation in the central basin
upper hypolimnion of Lake Erie are shown in Figure 102. The observed
data statistics shown were calculated from samples collected between 56
and 72 feet (17 to 22 m) to correspond to the layer represented by the
WASP model. The model tracks the temporal trend very well throughout the
three-year simulation. The magnitude of dissolved oxygen in the fall,
winter and spring is simulated accurately. Summer survey dissolved
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194
14
cn 12
^ 10
i_
_0 8
CL
I 6
Q_
5 4
-t—i
6 2
0
Western Lake Erie
1983 through 1985
JMMJSNJMMJSNJMMJSN
Month
Figure 99. WASP model simulation of ortho phosphorus in western Lake
Erie.
10 r
Central Lake Erie Epilimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
O
0
Figure 100. WASP model simulation of ortho phosphorus in the epilimnion
of central Lake Erie.
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195
10 r
O
Eastern Lake Erie Epilimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
0
Figure 101. WASP model simulation of ortho phosphorus in the epilimnion
of eastern Lake Erie.
oxygen concentrations are overpredicted by the model by about 1 mg/L.
These discrepancies are important. However, by updating the
environmental variables (i.e., temperature and dispersion) of the model or
by resolving issues concerning chlorophyll-a production, these differences
may be resolvable.
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196
C
0)
CD
>s
X
O
-o
CD
_>
O
CO
CO
Q
14 r
12
10
8
0
Central Lake Erie Upper Hypolimnion
1983 through 1985
JMMJSNJMMJSNJMMJSN
Month
Figure 102. WASP model simulation of dissolved oxygen in the upper
hypolimnion (17-22 meters) of central Lake Erie.
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197
COSOLUSICSXrS MO RECCMyENDATICINIS
The limited program of water-quality surveillance conducted by GLNPO
in the open waters of Lakes Michigan, Huron, and Erie from 1983 through
1985 provides an alternative surveillance strategy to the five year
program described in the original GLISP plan (IJC, 1975). Based on our
analysis of the observations made in 1983 and 1984 we concluded that the
conditions of three lakes have, in general, improved since the last GLISP
intensive surveys. The data collected in 1985 show this trend to be
continuing. Reanalysis of the data collected from Lakes Michigan and
Huron during previous intensive survey years shows that the sampling
scheme used from 1983 through 1985 would have provided representative
values of the water-quality parameters measured in the open waters during
those previous years. Thus, in terms of monitoring the quality of the
open waters of Lakes Michigan, Huron, and Erie, the reduced sampling
scheme used in 1983, 1984, and 1985 seems to provide adequate data. The
disadvantage of losing the spatial and temporal detail provided by the
intensive surveys is offset by the potential advantage of obtaining data
annually for the evaluation of natural variances and trends.
Although many measurements of water quality in the lakes were
unchanged from 1983 to 1985, the physical conditions, notably
temperature, were much different between 1984 and 1985 than in 1983.
While 1983 was a mild year, 1984 and 1985 were much colder. This
difference had a significant impact on both the annual nutrient cycle and
the results of the sampling program since colder spring waters delayed
the onset of biological activity, especially in Lakes Huron and Michigan
in 1984 and 1985. In addition, during 1985 the stratification for each
lake spanned a longer period than in 1983 and 1984. Stratification in
Lake Erie lasted 144 days, which is approximately 30% or 33 days longer
than normal (Fay and Rathke, 1987).
Concentrations of total phosphorus continue below the IJC target
concentrations in Lakes Michigan and Huron, and seem to be declining in
Lake Erie. Nitrate + nitrite nitrogen concentrations, are consistently
increasing in all three lakes. Chloride concentrations are increasing in
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198
Lake Huron and northern Lake Michigan, but continue to decrease in Lake
Erie. The chloride concentration in southern Lake Michigan was unchanged
between 1984 and 1985. Chloride concentrations have consistently
increased about 0.1 mg/L in prior years between 1963 to 1976 and 1983 to
1984 (Rockwell et al., 1980; Lesht and Rockwell, 1987).
The seasonal sampling program consisting of three ship-borne surveys
per year does not provide sufficient temporal resolution within a year to
evaluate the dynamics of the eutrophication models of the three lakes.
The models are only moderately successful at predicting the 1983, 1984
and 1985 observations.
All three lakes exhibited a pattern of nutrient depletion from the
epilimnion and concurrent enrichment of the hypolimnion during summer.
However, in 1985 the magnitude of the depletion for some parameters was
greater than that observed in 1983 and 1984. After stratification, all
of the deeper basins showed evidence of a benthic nepheloid layer, a high
turbidity region near the bottom having high concentrations of both
dissolved and particulate nutrients.
Nutrient concentrations within the nepheloid layer were consistently
higher than within the remainder of the hypolimnion, and the nepheloid
layer persisted through the time of the last regular survey in the fall.
The persistence of the nepheloid layer may imply active exchange between
the surface sediments and the overlying water column.
The Great Lakes water-quality surveillance program represents a
collective opportunity for both monitoring and limnological research. On
the basis of the data collected so far, we present the following
recommendations for future surveillance and surveillance-oriented
research activities.
1. The open-lake water quality surveillance program should be
continued on an annual basis. Data collected annually will be
most valuable for evaluating annual water-quality trends and
for establishing the magnitude of natural annual variations.
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199
Furthermore, annual data are required for evaluation of the
lake response to changes in loading levels.
2. The evaluation of water quality trends, a major surveillance
objective of the Canada-United States Water Quality Agreement,
depends critically on estimates of loadings to the lakes. Load
estimates for phosphorus are required on a year-to-year basis
for 1985-1986 and should be available (updated). Loading
estimates should be refined, if possible, and expanded to
include other substances in addition to phosphorus. Consistent
changes in the amounts of nitrate + nitrate nitrogen, silica,
and chloride in Lakes Michigan, Huron, and Erie, while not
currently a problem, could be investigated further if an
adequate mass balance database were available.
3. The role of the benthic nepheloid layer, and particle removal
in general, on the cycling of nutrients in the Great Lakes
should be studied. Data from the 1983 through 1985 surveys
show that near-bottom waters act as reservoirs of nutrients
that may be mixed into overlying waters during turnover.
4. Modeling efforts based both on simplistic mass-balance and
dynamic eutrophication models should be continued. Historical
simulations that include explicit year-to-year variation in
such functions as water temperature and vertical and horizontal
mixing should be attempted. Experiments in which the dynamic
eutrophication models are restructured to provide a more
realistic picture of particle behavior within both the
epilimnion and nepheloid layer should be conducted. Field data
with greater temporal resolution than the current three surveys
per year will be required for any serious attempt to improve
model performance.
5. Efforts should be continued to incorporate research activity
and methodology into the surveillance program. The goal of
both is a better understanding of the entire Great Lakes
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200
system. No doubt, the performance of the models could be
improved somewhat through a more vigorous modeling effort than
performed herein. However, to improve the confidence and
credibility of model results increased temporal resolution in
field data is needed. Further, inconsistencies between
surveillance data and mathematical model results emphasize the
need to perform both types of research.
6. Comparison of the basin mean results of the Great Lakes
Intensive Surveillance Program (GLISP) to those of the
spatially-reduced GLNPO program reveals that the GLNPO program
is as representative of Great Lakes water quality as the GLISP.
7. Comparison of the results of the GLISP to those of the
temporally-reduced GLNPO program (three surveys/year vs. eight
surveys/year in the GLISP) reveals that the GLNPO program is as
representative of central and eastern Lake Erie annual total
phosphorus concentrations as the GLISP.
-------
201
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-------
A-l
APPENDIX A
STATISTICAL SUMMARY OF SURVEY DATA
The abbreviations and units used in Appendix A are:
ABBREVIATION VARIABLE NAME UNITS
W_TEMP Water Tenperature Centigrade
TURBTY Turbidity Hach FTU
CHLOR_A Chlorophyll-a ug/L
PHPHTJ\ Pheophytin-a ug/L
PHOS T Total Phosphorus mg-P/L
PHOS_D Total Dissolved Phosphorus mg-P/L
DjORTH_P Dissolved ortho Phosphorus mg-P/L
N02ND3T Total Nitrate+Nitrite Nitrogen mg-N/L
NH3NH4T Total Ammonia Nitrogen mg-N/L
KJELJXT Total Kjeldahl Nitrogen mg-N/L
DSICON Dissolved Silicon ug-Si/L
PH pH Standard
LAB_PH Laboratory pH Standard
T_ALK Toatal Alkalinity wg-CaCO^/L
CNDUCT Specific Conductance uSiemen/cm
DO Dissolved Oxygen mg/L
CHLORDE Chloride mg/TL
SULFATE Total Sulfate
CA Total Calcium
MG Total Magnesium mg/L
NA Total Sodium mg/L
K Total Potassium mg/L
T Count Total Plate Count #/mL
1Sorted by lake, basin, survey, and layer.
-------
A-2
L MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT A
PHOS T
PHOS D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB PH
T ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR..A
PHPHT A
PHOS T
PHOS D
D_ORTH_P
NO2N03T
NH3NH4T
KJEL_.N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
8
0
8
8
8
8
8
8
8
8
8
7
8
8
8
8
8
8
0
0
0
0
0
62
58
62
62
62
61
61
61
62
62
61
62
0
62
62
12
62
62
0
0
0
0
18
BHS1IN = A_
1
0
-0
0
0
0
0
0
0
574
8
8
109
281
12
10
20
D a c TN- fl
DM ID _L M — ft
2
0
0
0
0
0
0
0
0
0
564
8
108
279
12
8
22
2
bUUlHtKN
.9500
7875
.0700
0058
0047
.0026
2930
0045
.0962
3750
0471
0212
4375
.6250
.7875
0750
1000
cnilTHFRM
D U U I ii t KfN
5452
4018
.9456
0495
0049
.0023
0009
2851
.0030
. 1189
.9016
. 1185
.4606
.9231
4425
6891
.0427
0000
bUKVLY
0
0
0
0
0
0
0
0
0
29
0
0
0
0
0
1
2
= A_WlNTd,K,
.4140
2276
0849
0010
0006
0014
0035
0038
0192
2034
0509
.0464
.4955
7440
. 2264
. 3414
2071
QIIR\7F*V — R QDD TMf
oUKVr.l-D or K .LINO
0 2805
0 1399
0
0
0
0
0
0
0
0
17
0
1
0
0
0
0
1
.7268
.0840
0008
0008
0005
.0177
.0033
.0467
.0506
.0754
.5148
7971
9497
.2454
.7245
1376
i. LA¥fc
0
0
0
0
0
0
0
0
0
10
0
0
0
0
0
0
0
T fi VC*D
Lin I t,K
0
0
0
0
0
0
0
0
0
0
2
0
0
0
0
0
0
0
K=b KPIL.
1464
0805
0300
0004
0002
.0005
.0012
0013
0068
3250
0192
0164
1752
2631
0800
4742
7803
LMN1ON -
1
0
-0.
0.
0
0.
0
0
0
538
8
7
109.
280
12
8.
17.
.2000
4800
.2000
.0050
.0036
.0008
2870
0010
.0600
0000
.0100
9500
.0000
0000
4000
.7000
.7000
2.
1.
0
0
0
0
0
0
0
616.
8
8.
110
282
13
11
22
.5000
.1000
0500
0079
0055
0047
2960
0110
1200
0000
1600
1100
5000
0000
1500
4000
3000
-B EPILIMNION --
.0356 1.
0184 0
0923
.0107
0001
0001
0001
0023
.0004
.0059
1831
.0096
. 1924
1012
2742
.0312
.0920
.2681
0,
-0,
0
0
0
0
0.
0.
525.
7 .
103.
278.
10.
7.
20.
1.
.9000
1800
.0000
. 2000
0034
0015
0000
2550
.0000
.0400
0000
.9300
.5000
.0000
.6000
8000
9000
0000
3.
0.
2.
0.
0.
0.
0
0.
0.
0.
594
8.
112.
281.
13.
9.
23.
5,
.1000
9550
.5000
.2000
.0073
.0053
0021
3320
.0200
.3000
0000
.2500
.0000
.5000
.2000
.4000
.9000
0000
-------
A-3
L. MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB^PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
43
42
43
43
43
43
43
43
43
43
43
43
0
43
43
42
43
43
18
18
18
18
10
18
18
18
18
18
18
16
18
18
18
18
18
0
18
18
18
18
18
0
0
0
0
1
- DA&1H-H_£)UU 1H&K1'
20 6767
0.4815
1.1169
0.1907
0.0025
0 0014
0.0004
0 1591
0.0023
0.2134
97.1395
8.5827
108.1337
277 .7151
9.4530
8 8215
21 7135
36 0000
11.1667
5.4611
1.2283
37.1000
BASIN=A SOUTHERN
13.9222
0.4543
1 2306
0 2847
0.0035
0 0017
0.0004
0.1936
0.0140
0.2057
110.1667
8 4814
108.6250
279.4028
11.8300
8.7486
21.7517
190.0000
0 6342
0 1588
0.2173
0 1757
0 0008
0.0008
0 0005
0.0161
0 0039
0 1047
16 6699
0.0553
0 8870
1 8213
0.7208
0.3555
0.9364
0.6860
0 3835
0 1290
0 0176
21 .6151
SURVEY-C SUMMER
1 7121
0. 1457
0 3121
0 2516
0 0011
0 0010
0 0003
0.0115
0 0084
0 0613
23 2107
0 0911
0.6766
1 .0611
1.2257
0.2483
0.9453
C LiHILK-D C,fl L IMINIUIN
0.0967 19.3000
0.0245
0.0331
0.0268
0 0001
0 0001
0.0001
0 0025
0 0006
0.0160
2.5421
0 0084
0 1353
0.2777
0.1112
0 0542
0.1428
0 1617
0.0904
0.0304
0 0041
0 2400
0 7000
-0. 1000
0.0007
0.0005
-0.0006
0 1340
-0.0010
0 0500
52 0000
8 4300
106.5000
274.0000
8 2000
8 0000
20 0000
35 0000
11 .0000
5.2000
1 .2000
6 8353 11 .0000
LAYER-C ME SOL IMN ION
0.4035 11.3000
0.0344 0.2500
0.0736
0.0593
0.0003
0 0002
0 0001
0 0027
0.0020
0 0145
5.4708
0 0215
0. 1595
0.2501
0.2889
0.0585
0.2228
0.8000
0.0000
0.0008
0.0005
0 0000
0 1740
0.0040
0.0900
75 0000
8.3100
107.5000
278.0000
10.1000
8.4000
20. 2000
190.0000
21 .9500
0 7900
1 .6000
0.6000
0.0048
0.0037
0.0019
0 J 890
0.0200
0 6400
130 0000
8 6750
110 0000
281 .5000
11 2000
9 . 3000
23.3000
37 .0000
12.0000
5.6000
1 2600
71 .0000
17 6000
0 7500
1 7000
0 9000
0.0055
0.0045
0.0010
0.2090
0 0300
0.3100
162.0000
8 6000
109.5000
281 2500
14. 6000
9.2000
23.3000
190.0000
-------
A-4
L. MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W TEMP
TURBTY
CHLOR A
PHPHT A
PHOS_T
PHOS _D
D_ORTH_P
N02N03T
NH3MH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLOPDE
SULFATE
CA
MG
NA
K
T COUNT
W TEMP
TURBTY
CHLOR_A
PHPHT A
PHOS_T
PHOS D
D ORTH P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
34
34
34
34
34
34
34
34
34
34
34
34
0
34
34
34
34
34
0
0
0
0
4
36
35
36
36
36
36
36
36
35
36
36
36
0
36
36
35
36
35
18
18
18
18
5
dtti3lIN-A_t>UUlttd.KlN £
4 9088
0
1
0
0
0
0
0
0
0
431
8
108
281
12
8
21
94
D TV c TM- A
D t\ J 1 IN — t\
4
0
0
0
0
0
0
0
0
0
906
8
108
283
11
8
21
36
11
5
1
95
3167
0684
.3662
.0035
.0016
0006
.2742
.0056
.1706
.4706
1612
. 4488
3676
2571
.6015
.6141
.7500
QniJTMFRM
oUU inc. KIN
1278
8791
7056
3882
0060
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0026
3160
0005
1600
0556
0721
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.1319
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6174
.7457
.3889
.0556
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2311
0000
3UKVt![=L bUMMfcK L
0 7473
0
0
0
0
0
0
0
0
0
203
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0
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0
0
0
0
0
0
0
0
0
0
298
0
0
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0
1
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0
0
0
56
1774
5871
. 2920
0014
0011
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0051
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9653
.0770
5437
8101
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. 2739
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CCHMMFD
burl Fit, K
2742
. 4536
3944
. 1747
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.0027
0022
.0176
0011
.0670
4887
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. 2884
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7775
2357
1043
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jflYtK-U
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0.
0
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0
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0
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0.
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0.
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0.
0
25
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1282
0304
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0501
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0089
9798
0132
0932
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1167
0470
1537
0586
E NEPHELOID
0457
0767
0657
0291
0005
0004
0004
0029
0002
0112
7481
0104
1167
1592
1503
0481
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0034
3298
N ~-
3.
0.
0.
0.
0
0.
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135.
8.
107
279
11
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0
0.
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0
0.
0
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509
7
107
281
10
8
19
35
11
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1
34
8000
0900
2000
0000
0008
0000
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2190
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0700
0000
0200
0000
0000
2000
1000
6000
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1020
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1000
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.0003
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.7500
. 1000
1000
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0000
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2000
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0.
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0
0.
0.
0.
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109.
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9.
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2
1
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0
0
0
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286
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0000
8100
2000
6000
0078
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0036
3220
0170
2900
0000
3700
5000
0000
0000
2000
6000
.0000
6000
1000
6000
.8000
.0139
.0089
.0067
3720
.0040
3500
.0000
1800
1300
0000
.3000
.2000
.2000
.0000
0000
.4000
.2600
.0000
-------
VARIABLE
A-5
L. MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOSJT
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
NO 2ND 3 T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
20
20
20
20
20
20
20
20
20
20
20
20
0
20
20
20
20
20
0
0
0
0
13
5
5
5
5
5
5
5
5
5
5
5
5
0
5
5
5
5
5
0
0
0
0
0
BHbiN=A_bUUTHh;KN SI
8.3100
0.2474
0.5587
0.1637
0.0040
0.0024
0.0002
0.2489
0.0024
0.1680
388.9500
8.3389
107.0175
281.9815
9.8612
9.0362
22.0090
27.9231
R A^TN— B QniiTPPRM CM
DftO i l"i — M OUU1 nil KIN O\,
6.7400
0.3195
0.2250
0. 1000
0.0027
0.0015
0.0006
0.2894
0.0014
0.1860
509.2000
8.1930
107.0400
283.0500
10.0700
8.9400
21.5600
JKVhY=U FALL
1.0010
0.1137
0. 1776
0.1128
0.0011
0.0009
0.0002
0.0168
0.0011
0.0663
45.9983
0.0363
0.7096
0.8370
0.2852
0.2767
0.6005
18.8656
tRWFV — n Fit T
IKVC, i ~u rHJjii
0.5683
0.1993
0.0433
0.1225
0.0006
0.0006
0.0007
0 0084
0.0008
0.0647
83.0855
0.0396
1 .3069
0.4472
0.4894
0.4037
1.5710
1 LAYER=B_EPILIMNION
0.2238 6.4000
0.0254
0.0397
0.0252
0.0003
0 0002
0.0001
0.0038
0.0002
0.0148
10.2855
0.0081
0.1587
0. 1872
0.0638
0.0619
0.1343
0.1400
0.2000
-0. 1000
0.0014
0.0010
0.0000
0.2250
0.0010
0.0800
312.0000
8.2900
105.5000
280.8799
9.3000
8.4000
21 . 1000
5.2324 6.0000
1 T 7VVPD — r* MPCOT TMMTi"lM
1 LA I t,t\ — L MnbUJj J.MM1UN
0.2542 6.0000
0.0891 0.1775
0.0194
0.0548
0.0003
0.0002
0 0003
0.0037
0.0004
0.0289
37. 1570
0.0177
0.5845
0.2000
0.2189
0.1806
0.7026
0. 2000
0.0000
0.0018
0.0009
0.0000
0. 2840
0.0010
0.1000
415.0000
8.1550
105.0000
282.5000
9.4000
8.4000
18.8000
9.3000
0.6600
0 9000
0.3000
0 0056
0.0038
0.0006
0.2740
0.0041
0. 2800
506.0000
8.4100
108.5000
284.0000
10.3000
9.5000
23.4000
65.0000
7.3000
0.6400
0.3000
0.3000
0.0034
0.0024
0.0017
0.3030
0.0029
0. 2800
644.0000
8 2600
108.5000
283.5000
10.7500
9.5000
22.6000
-------
A-6
L. MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W TEMP
TURBTY
CHLOR A
PHPHT_A
PHOSJT
PHOS_D
D_ORTH_P
N02N03T
MH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T^ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W TEMP
TURBTY
CHLOR A
PHPHT_A
PHOSJT
PHOS_D
D ORTH P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
7
7
7
7
7
7
7
7
7
7
7
7
0
7
7
7
7
7
0
0
0
0
5
11
11
11
11
11
11
11
11
11
11
11
11
0
11
11
11
11
11
0
0
0
0
6
Bft£>lIN-rt_b
4.
0.
0.
0
0.
0
0
0.
0.
0.
669.
8.
107.
283.
10.
8.
21.
47.
D A CT W A
D r\ o J. i> — M
4.
0
0
0.
0.
0.
0
0.
0.
0
935.
8.
108.
284.
9.
9.
21.
76.
uuinbKN :
6857
3021
1286
0643
0034
0021
0008
3100
0033
2071
2857
1436
8071
3214
4143
9786
8000
2000
cniTTHFRM
oUU J. n LJ n i >
3091
8918
0886
1318
0049
0033
0026
3314
0010
2230
2727
0891
2527
7727
9755
0818
9091
8333
0.
0.
0.
0.
0.
0.
0.
0.
0.
0
150.
0.
1 .
0.
0.
0.
1.
24
C1IT3WC1 V
DUKV C, I
0
0
0
0
0.
0
0.
0.
0.
0
138
0.
0.
0.
0.
0.
0
73.
U FALL!
5786
1636
0488
0852
0024
0015
0010
0186
0050
1626
0330
0293
0537
8746
5984
3510
3952
6313
DP B T T 1
r AtiL 1
2663
4622
0540
0956
0024
0015
0021
0188
0008
1830
0160
0474
7591
5641
3636
4792
5431
2186
LAYbK-
0
0
0
0
0
0
0
0
0
0
56
0
0
0
0
0
0
11
T Tl VCD
LAY bK
0
0
0
0
0
0
0
0
0
0
41
0
0
0
0
0
0
29
L>_HYFULiMNl(JN --
.2187 4
.0618
.0184
0322
0009
.0006
.0004
.0070
.0019
.0614
7071
0111
3983
.3306
2262
1327
5273
.0154
-E NEPHELOID
0803
.1394
0163
0288
.0007
0005
.0006
.0057
.0002
.0552
.6134
.0143
.2289
.1701
.1096
.1445
.1637
.8914
0
0
-0.
0
0
0.
0
0
0.
415
8
106
281
9
8
18
7
4
0
0
0
0
0
0
0
0
0
731
8
107
283
9
8
21
6
.0000
.1600
.1000
. 1000
.0014
.0007
.0000
.2840
.0010
.0600
.0000
.1100
.0000
5000
.5000
.4000
.8000
0000
.0000
.4800
.0000
.0000
.0016
0011
.0003
.3080
.0000
.0700
.0000
.0100
.0000
.5000
.3000
.4000
. 2000
.0000
5.
0
0.
0.
0.
0.
0.
0.
0.
0.
809.
8.
109.
284.
11 .
9.
22.
74.
4,
2.
0.
0.
0.
0
0
0
0
0
1151
8.
109
285
10
10
22
210
6000
5400
2000
1500
0084
0050
0024
3360
0145
5500
0000
1850
0000
0000
2000
5000
8000
0000
.6000
. 1100
.2000
.3000
.0093
0052
.0060
.3570
.0021
.7300
.0000
.1700
.5000
.5000
.3300
.0000
.7000
.0000
-------
VARIABLE
A-7
L. MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
BftSlN-fl_bUUlHtKN t>UKVt,K-U_f ALL^ LAYKK-b
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS^D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
36
36
35
35
36
36
36
36
36
36
36
36
0
36
36
31
36
36
0
0
0
0
0
DZ
6
0
6
6
6
6
6
6
5
6
6
4
6
6
6
6
6
6
0
0
0
0
0
5
0
0
0
0
0
-0
0
0
0
609
8
107.
279.
11.
8.
23.
.4361
.4493
.3186
.0979
.0055
.0028
.0000
.2897
.0012
.0672
.5833
.1206
.6844
.6100
.3739
6910
1530
i Q T vi — p HO D T t-T C1 D M
ioiN— D rjuKi HE.KN
1.5417
0.
-0.
0.
0.
0.
0.
0.
0.
545.
8.
8.
109.
283
12.
8
22
8900
1200
0056
0041
0018
2905
.0044
.2000
.1667
.0275
.0067
.5000
.5000
.8417
.9667
.4167
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
85.
0.
1.
1.
0.
0.
0.
CUD we1 v —
bUKVt. I —
i .
0.
0.
0.
0.
0.
0.
0.
0.
37.
0.
0.
1.
2.
0.
0.
0.
3826
1691
0856
0573
0007
0007
0001
0197
0003
0524
0282
0536
1458
4112
2191
0930
4650
AU T MTC"D *5
_WJ.N IfcKz
3078
4402
0447
0015
0004
0014
0260
0011
0982
2474
0574
0520
0000
8810
7406
1506
6706
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
14.
0.
0.
0.
0.
0.
0.
LAYER
0.
0.
0.
0.
0.
0.
0.
0.
0.
15.
0.
0.
0.
1.
0.
0.
0.
KPILIMNIUN
0638
0282
0145
0097
0001
0001
0000
0033
0001
0087
1714
0089
1910
2352
0393
0155
0775
4 .
0.
0.
0.
0.
0.
-0.
0.
0.
-0.
484.
8.
106.
277
11.
8.
22.
.6000
.2800
.2000
.0000
.0044
.0019
.0003
2530
.0008
0500
0000
0300
0000
0000
0000
5000
3000
6.
0.
0.
0.
0.
0.
0.
0.
0
0.
803.
8.
109.
282.
11 .
8.
24.
.0000
.8450
.4500
.3000
.0077
.0052
.0000
.3190
.0020
. 1700
.0000
2300
1300
0000
7000
9000
1000
-B EPILIMNION -
5339 0.
1797
0183
0006
0002
0006
0106
0005
0401
2062
0287
0212
4082
1762
3023
0615
2738
0.
-0.
0.
0.
0.
0.
0.
0.
492.
7.
7.
108
280
12
8
21
0000
3500
1800
0045
0036
0005
2550
0030
.1100
.0000
.9500
.9100
.5000
.0000
.1000
.8000
.6000
3
1
-0.
0
0
0
0
0
0
590
8
8
111
287
14
9
23
.0000
.4900
.0700
.0086
.0046
.0043
.3190
.0060
.3200
.0000
.0800
.0600
.0000
.0000
.0000
.2000
.6000
-------
A-8
L. MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS T
PHOS n
D_ORTH..P
N02N03T
NH3NH4T
K.TEL_N
DSICON
PH
LAB^PH
T ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHT,OR_A
PHPHT_A
PHOS_T
PHOS D
D_ORTH_ P
N02N03T
NH3NH4T
KJEL N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
62
62
62
62
62
62
62
62
62
62
62
62
0
62
62
10
62
62
0
0
0
0
19
33
33
33
33
33
32
31
33
33
33
33
33
0
32
33
33
33
33
15
15
15
15
10
DMOJ.1N -D
2
0
0
-0
0
0
0
0
0
0
562
8
107
279
12
8
22
1
D 7\ C T M— R
D l\J i. IN — D
18
0
0
0
0
0
0
0
0
0
92
8
108
276
9
8
21
35
11
5
1
101
IN\JI\ i nc,r\ii oun. v n, i -D or niiNu Lifti nn
.5202
.3396
.7474
.0088
.0052
.0028
.0009
.2863
.0016
.0805
.8387
1691
.9210
.7790
7370
.8363
3456
4211
MnRTHFDW cil
INUKlncKlN ol
4848
.3588
.9955
. 1227
0045
.0012
0004
1556
.0036
1837
.8788
.5444
.0353
.5606
.9202
.5561
.5751
.2000
.0000
.3733
.2073
.5000
0
0
0
0
0
0
0
0
0
0
49
0
1
0
0
0
0
0
IRUFV
JK VCi I
i
0
0
0
0
0
0
0
0
0
22
0
0
1
0
0
0
0
0
0
0
56
.2417
.2873
.9373
.2548
.0022
.0011
.0006
.0152
.0009
0493
.9637
.0632
.4409
.8799
.4822
.3100
.3625
. 6070
.1603
. 1742
. 2879
. 1587
.0036
.0006
0005
0166
.0027
0617
. 1638
.0580
.7330
.3521
. 6913
.3132
. 4922
.7746
.0000
.0961
.0139
.3979
0
0
0
0
0
0
0
0
0
0
6
0
0
0
0
0
0
0
?D T B VCD
LK Jj/\ I CiK
0
0
0
0
0
0
0
0
0
0
3
0
0
0
0
0
0
0
0
0
0
17
- D n, f i LI i miN IUIN
.0307
0365
1190
.0324
.0003
.0001
.0001
.0019
.0001
0063
3454
0080
.1830
.1117
1525
.0394
.0460
2.
0.
0.
-1.
0.
0.
0.
0.
0.
0.
494.
8.
105
278.
11 .
8.
21 .
.1393 1.
— n T71 D T T T MM T (™1M
- D br L Li 1MIN LUlN ~ ~
2020 15.
0303 0.
0501
0276
0006
.0001
0001
.0029
.0005
.0107
.8582
.0101
.1296
.2354
.1203
.0545
.0857
.2000
.0000
.0248
0036
.8346
0.
-0
0
-0.
-0.
0
0
0
57
8
107
274
9
7
20
34
11
5
1
26
1000
1200
0000
5000
0031
0014
0000
2610
0000
0100
0000
0100
0000
0000
9000
4000
4000
.0000
.2000
.1600
.6000
.1000
.0020
.0003
.0003
. 1340
.0010
.0200
.0000
.4500
.0000
.0000
.1000
.9000
.7000
.0000
.0000
.2000
.1900
.0000
3.
2.
5.
0.
0.
0.
0.
0.
0.
0.
752.
8.
Ill .
281
13.
9.
23.
3
19
0
1
0
0
0
0
0
0
0
163
8
109
279
11
9
23
36
11
5
1
200
0000
3700
5000
2000
0161
0054
0028
3190
0040
2400
0000
2800
.0000
5000
.7400
.8000
.1000
.0000
.7000
.8400
.6000
.5000
.0191
.0026
0016
. 1895
.0120
3800
.0000
.6700
.5000
.0000
.8000
.0000
2000
0000
.0000
.5000
.2300
.0000
-------
VARIABLE
A-9
L. MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOSJT
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
15
15
15
15
15
15
15
15
15
15
15
15
0
15
15
14
15
15
0
0
0
0
0
37
37
37
37
37
36
37
37
37
37
37
37
0
37
37
37
37
37
0
0
0
0
5
Bn»iN-B_m
12
0
1
0
0
0
0
0
0
0
144
8
108
279
12.
8.
21.
JKitltKN
.3067
.2850
.3200
.3000
.0056
.0013
.0006
. 1958
.0099
.1773
.9333
.4510
.4167
.0000
.2929
.5300
.8333
RZVQ TH — R MnDTPFDM
D /\ o 1 IN — D INUKlnCj KP1
4.4892
0.2002
0.
0.
0.
0.
0.
0.
0.
0.
420.
8.
108.
281,
12.
8.
21.
129
7365
2378
0034
.0016
,0009
.2827
.0035
1274
.1892
.1802
.3378
,4324
,5730
.5304
.9973
4000
2
0
0
0
0
0
0
0
0.
0.
69
0
0,
1 .
0,
0.
0
QltPVF V — f
oUKvCi I —L
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
97.
0.
0.
0.
0.
0.
0.
85
; bUMMfcK
.0748
. 1354
.3707
. 1852
.0047
.0007
.0005
0130
.0073
.0597
.2732
.0771
.7420
.0177
.6810
.3116
5551
i QIIMVITD
, oupmt.K
5577
0992
7260
2073
0016
0010
0007
0155
0049
.0441
.1559
.0378
7822
.7920
.5146
.3174
.4356
.2690
LAYEK-U
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
17.
0.
0.
0.
0.
0.
0.
T Z VPD — n
iiAz C.K-LJ
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
15.
0.
0.
0.
0.
0.
0.
38.
_MEt>ULit
5357
0350
0957
0478
0012
0002
0001
0034
0019
0154
8863
0199
1916
2628
1820
0804
1433
1NIUN --
6
0.
0.
0.
0.
0.
-0.
0.
0.
0.
47.
8.
107
277 .
11.
7.
20.
.6000
. 1600
.7000
. 1000
.0018
.0005
.0003
.1770
.0000
. 1200
.0000
.3300
0000
.0000
.3000
.9000
.7000
14.
0.
2.
0.
0.
0
0.
0.
0.
0.
275.
8.
109
281
13.
8.
23.
6000
7000
1000
7000
0221
0027
0013
2240
0270
3500
0000
5800
7500
0000
5000
9000
2000
T-lVDnT TMMTOM
n I trUL IMN 1UN ~~
0917 3.
0163 0.
1193
0341
0003
0002
0001
0025
0008
0072
9723
0062
1286
1302
0846
0522
0716
1334
0.
0.
0.
0.
-0.
0
-0.
0
249
8
107
279
11
7
20
48
.8000
.1000
.1000
.0000
.0015
.0000
.0003
.2480
.0010
.0300
.0000
.0900
.0000
.0000
.4000
.9000
.9000
.0000
5.
0.
3 .
1.
0.
0.
0.
0.
0.
0.
592.
8.
110.
283.
13.
8.
23.
240
7000
5700
2000
0000
0096
0050
0022
3210
0200
2200
0000
2700
.0000
0000
,4000
,9000
.2000
.0000
-------
A-10
L. MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DEICON
PH
LAB_PH
T^ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS^T
PHOS_D
D_ORTH_P
N02N03T
NH1NH4T
KJEL_N
DSICON
PH
LAB PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
30
30
30
30
30
30
30
30
30
30
30
30
0
30
30
30
30
30
15
15
15
15
5
14
14
14
14
14
14
14
14
14
14
14
14
0
14
14
14
14
14
0
0
0
0
10
Dtt^lN-D 1
3
0
0
0
0.
0
0
0.
0,
0.
1003.
8.
108
283
11
8
22.
35
11.
5.
1.
99.
pa CTM — H J
D t\ o J. n — D I
8.
0.
0.
0.
0.
0.
-0.
0.
0.
0.
337.
8.
107.
281.
10
8.
21.
16.
*IUK i n&KW
.8367
.7544
.4397
.2847
.0080
.0058
.0040
.3137
.0010
.1322
.6000
.0770
.9673
.0753
.9483
.4992
.0483
9333
.0220
.3933
.2278
.8000
jnRTWI7DM
^UK 1 nC,KN
.1357
.2295
.7804
.2304
.0032
.0021
.0003
.2321
.0014
. 1025
.5714
.3587
.2364
.0536
8275
.5857
.7143
,9000
OUKVC.I
0
0
0
0
0
0
0
0
0
0
198
0
0
1
0
0
0
0
0
0
0
83
0
0
0
0
0
0
0
0
0
0
40
0
0
1
0
0
0
19
.1351
.2676
.2641
.1182
.0023
.0023
.0026
.0146
.0017
0560
.7535
.0585
.7019
. 1051
.6355
.3291
.5051
.7037
.0852
.1163
.0197
.0193
— n P B T T i
— U r ALL 1
.9716
0400
.2333
.0810
.0005
.0007
.0005
.0158
.0009
.0346
.6991
.0266
.3550
. 1015
.6945
.0641
.3207
.3129
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
36.
0.
0
0.
0.
0.
0.
0.
0.
0.
0.
37.
I B VC"D — D
LAYhK-D
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
10.
0.
0.
0.
0.
0.
0.
6.
E._NfcFMfcLUiU
0247
0489
0482
0216
0004
0004
0005
0027
0003
0102
2873
0107
1281
2018
1160
0601
0922
1817
0220
0300
0051
1273
EPILIMNION
2597
0107
0624
0216
0001
0002
0001
0042
0002
0092
8773
0071
0949
2944
1856
0171
0857
1073
3.
0.
0.
0.
0.
0.
-0.
0.
-0.
0.
723.
7.
108.
280.
10.
7.
20.
35.
11.
5.
1.
19.
7.
0.
0
0.
0.
0.
-0.
0.
0.
0.
258.
8.
106.
279.
9.
8.
21.
3.
7000
1200
2000
1000
0017
0012
0019
2797
0005
0200
0000
8900
0000
0000
3000
9000
9000
0000
0000
2000
2100
0000
3000
1800
3000
1000
0019
0007
00] 1
2000
0000
0400
0000
3100
8800
2500
5000
5000
1000
0000
4.
1.
1.
0.
0.
0.
0.
0.
0.
0.
1476.
8.
110.
285.
12.
8.
23.
37
11.
5.
1 ,
230.
9,
0,
1 .
0.
0.
0,
0
0
0
0
378
8
108
283
11
8
22
64
2000
4400
3000
6500
0139
0104
0099
3460
0070
2800
0000
1700
0000
0000
9000
9000
0000
0000
3300
6000
,2800
0000
,9000
,3400
. 1000
.3000
,0039
,0032
0005
.2530
.0030
.1700
.0000
.4200
.0000
.0000
.5000
.7000
.3000
.0000
-------
VARIABLE
A-ll
L. MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOSJT
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJELJJ
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOSJT
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
5
5
5
5
5
5
5
5
5
5
5
5
0
5
5
5
5
5
0
0
0
0
0
10
10
10
10
10
10
10
10
10
10
10
10
0
10
10
10
10
10
0
0
0
0
1
BHSJ.N = B_NUKlHtKN bUKVt][ =
6.6400 0.
0
0
0
0
0
-0
0
0
0
409
8
107
282
11
8
21
.1940
.1400
1200
.0022
.0018
.0003
.2790
.0008
.1120
.2000
. 2040
.4400
.8000
.0100
.5800
.8400
0.
0.
0.
0
0
0.
0.
0.
0.
50.
0.
0.
0.
0.
0.
0.
u_i-ftLLi LAYfc;K-u_Mt;auLir
5899 0.2638
0182
0548
0447
0010
0006
0005
0095
0004
0277
5094
0329
4929
7583
8806
1095
1817
R1QTM— R MnPTHFRM ciTDi/i?v-n r?7vr T
DftG J. IN ~D INUK 1 tlljKlN O
4.3300
0.1975
0.
0.
0.
0
0.
0.
0.
0.
588.
8.
107.
283.
11.
8.
21.
20.
0500
1050
0033
0032
0014
2931
0006
0737
5000
1780
7930
.0630
.4410
.5825
.9800
.0000
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
158.
0.
0.
1.
0.
0.
0.
u r I\LI LI
3974
0544
0486
0919
0010
0013
0010
0074
0008
0557
9530
0346
6773
1039
7921
0817
1398
0
0
0
0
0
0
0
0
0
22
0
0
0
0
0
0
1 T B VC"D — T
1 Lift i CiK-L
0
0
0
0
0
0
0
0
0
0
50
0
0
0
0
0
0
.0081
.0245
0200
0004
0003
.0002
.0042
.0002
.0124
.5885
.0147
.2205
.3391
.3938
0490
.0812
1N1UN --
6
0
0
0
0
0
-0
0
0
0
337
8
107
282
9
8
21
. 1000
.1700
. 1000
.1000
.0006
.0009
.0011
.2720
.0000
.0800
.0000
. 1500
.0000
.0000
.8500
5000
.6000
7.
0
0.
0.
0
0.
0.
0
0.
0.
460
8.
108.
284.
11.
8.
22.
5000
2100
2000
2000
0033
.0026
.0000
2950
.0010
.1500
0000
.2400
.2000
.0000
.8000
7000
0000
1 I4VDOT TMMTflNT
j n I rUL 1MN J.UN ~"
.1257 3.
.0172 0.
.0154
.0291
.0003
.0004
.0003
.0023
.0003
.0176
.2654
.0109
.2142
.3491
.2505
.0258
.0442
0.
0,
0.
0.
0.
0.
0.
-0.
409.
8
106
281
10
8
21
20
,8000
.1500
.0000
.0000
.0019
.0016
.0003
.2847
.0000
.0600
.0000
.0900
.5000
.0000
.4000
.4500
.8000
.0000
5.
0
0
0
0
0
0
0
0.
0
938
8
109
284
12
8
22
20
.0000
.3325
.1000
.3000
0047
0061
.0033
. 3022
.0020
.1300
.0000
.2100
.0000
.5000
.3000
7000
. 2000
.0000
-------
A-12
L MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D ORTH_P
N02N03T
NH3NH4T
KJEL_N
USICON
PH
LAB_PH
T^ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
MA
K
T_COUNT
W_TEMP
TURBTY
OIL OR A
PHPHT A
PROS T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_M
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
10
10
10
10
10
10
10
10
10
10
10
10
0
10
10
10
10
10
0
0
0
0
9
15
15
15
15
15
15
15
15
15
15
15
15
0
15
15
10
15
15
0
0
0
0
0
- DrtttllN-D INUKinCKP
3.9400
0.8380
0.0800
0.2700
0 0090
0.0069
0.0042
0.3109
0 0010
0.1070
1162 5000
8. 1030
108.5100
284 9500
10 8150
8 5750
21 7400
16.4444
p 7\ C T M— O MnDTWPDM
D M b 1 IN - D IN U K 1 H £• KIN
6.5000
0.2567
0 3200
0 1067
0.0043
0.0030
0 0004
0.2464
0.0015
0.0467
410 4000
8. 1867
107.0833
278 7266
12.0180
8.8667
21.7767
t DUKV&I-U rrtbbl
0.1430
0.3517
0.0632
0.2163
0.0017
0.0015
0 0009
0.0128
0.0008
0.1431
188.2824
0.0365
0.7767
0.7619
0.8124
0.0425
0.5562
18.7424
CITDWPV — n 17 B T T ")
bUKVt I — U r ALL ^
0. 5182
0.0966
0. 1373
0.0704
0 0009
0.0004
0.0004
0.0322
0.0004
0.0763
63.7246
0.0516
0.7260
1.7056
0.5074
0. 1397
0.4460
0.0452
0.1112
0.0200
0.0684
0 0005
0.0005
0.0003
0.0040
0 0003
0.0452
59.5401
0.0116
0.2456
0.2409
0 2569
0.0134
0. 1759
6.2475
T 7\ V t1 D — D tTDTTTMIs
LA I C.K-D trlli IMP
0 1338
0.0249
0 0355
0.0182
0 0002
0 0001
0.0001
0.0083
0.0001
0 0197
16 4536
0.0133
0.1874
0.4404
0.1605
0.0361
0.1151
,uiu
3.8000
0.4500
0.0000
0.1000
0.0072
0.0048
0.0031
0.2900
0.0000
0.0200
771 .0000
8.0400
107 .8000
284.0000
9.6000
8 5000
20.6000
3.0000
I TOM
J 1 UIN
5 8000
0.1500
0.2000
0.0000
0.0032
0.0024
-0 .0003
0. 1500
0.0007
-0.0600
353.0000
8.1200
105.8000
275.5000
11.5000
8.5000
21.0000
4. 1000
1.6500
0 2000
0.8000
0.0130
0.0092
0.0061
0.3310
0.0020
0.5000
1384.0000
8.1600
110 0000
286.5000
11.8000
8.6000
22.5000
60.0000
7.2000
0.4800
0.6000
0 2000
0.0064
0.0036
0.0013
0.2800
0.0021
0.2700
541.0000
8.2900
108.0000
280.5000
12.8000
9 1000
22.6000
-------
A-13
L. MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
NO 2ND 3 T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
MA
K
T_COUNT
WJTEMP
TURBTY
CHI,OR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUMT
BHO1IN-B INUKlMtKIN
5 5.2000
5
5
5
5
5
5
5
5
5
5
5
0
5
5
4
5
5
0
0
0
0
0
RZ
Dr
7
7
7
7
7
7
7
7
7
7
7
7
0
7
7
5
7
7
0
0
0
0
0
0
0
0
0
0
0
0
0
0
623
8
107.
279.
12.
8.
21.
.3230
.1300
.0900
.0044
.0040
.0010
.2763
.0015
.0730
8000
.1620
.0360
.6260
2450
8800
9060
BMO D T U IT D H
IN UK 1 nc*Kri
4.1571
0.3411
0.
0.
0.
0.
0.
0.
0.
0.
765.
8.
107.
281.
12.
8.
21.
0429
0643
0064
0056
0026
2886
0012
0461
8571
1636
6614
2828
1760
8929
8686
bUKVt*=U_fAl,i,^
0.3317
0.
0.
0.
0.
0.
0.
0.
0.
0.
219.
0.
1.
1.
0.
0.
0.
CIIDVC" V —
oUKVE. I -
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
164.
0.
1.
1 .
0.
0.
0.
1789
0975
0742
0011
0006
0004
0139
0004
0455
7150
1425
3283
4831
6471
1304
6436
DC1 B T T T
_r ALLz
4036
1924
0535
0476
0013
0009
0010
0149
0002
0196
9843
1907
2427
5627
5717
1018
3876
LAYKK=U MEbULlMNlUN -•
0.1483 4
0
0
0
0
0
0
0
0
0
98
0
0
0
0
0
0
LAYER-
0
0
0
0
0
0
0
0
0
0
62
0
0
0
0
0
0
.0800
.0436
.0332
.0005
.0003
.0002
.0062
.0002
.0203
.2596
.0637
.5941
.6632
.3236
.0583
.2878
0
0
0
0
0
0
0
0
0
457
8
105
278
11
8
21
.9000
.1600
.0000
.0000
.0029
.0033
.0008
.2590
.0007
.0100
.0000
.0200
.3800
.0000
.5800
.8000
.1000
5
0
0
0
0
0
0
0
0
0
1008
8
108.
281.
12.
9.
22.
.6000
.6200
. 2500
.2000
.0057
.0048
.0018
.2960
.0018
.1300
.0000
.4000
.0000
.0000
.8000
1000
.6000
D HYPOLIMNION --
.1525 3.
.0727 0.
.0202
.0180
.0005
.0003
.0004
.0056
.0001
.0074
.3582
.0721
.4697
.5907
.2557
.0385
.1465
0.
0.
0.
0.
0
0
0
0.
499
7.
105.
279.
11,
8
21
.8000
.1100
.0000
.0000
.0038
.0043
.0014
.2620
.0010
.0200
.0000
.9800
.0000
.0000
.6000
.8000
.5000
5.
0.
0.
0
0.
0,
0
0
0
0
982,
8,
109.
283.
12,
9
22
.0000
.7100
. 1000
. 1000
.0082
.0071
.0039
.3050
.0016
0800
.0000
.5250
.0000
.0000
.8000
.1000
.6000
-------
VARIABLE
A-14
L. MICHIGAN DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB^PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
I
10
10
10
10
10
10
10
10
10
10
10
10
0
10
10
10
10
10
0
0
0
0
0
4
0
0
0
0
0
0
0
0
0
922
8
107
281
12
8
22
PIUKinC.KI1 £
.1500
.7390
.0650
.1000
.0083
.0069
.0035
.2948
.0014
.0262
.7000
.0395
.6130
.5810
.0950
.8600
0310
JUKVC. ]
0
0
0
0.
0
0.
0.
0.
0
0.
105.
0.
1.
1
0.
0.
0.
.3951
.4158
.0459
.0635
.0012
.0012
0012
.0130
0004
.0403
6746
.0345
.0744
4603
4487
.1776
4832
UrtXC.K
0
0
0
0
0
0
0
0
0
0
33
0
0
0
0
0
0
-e. iNC.fnc.buiu
.1249
.1315
.0145
.0201
.0004
.0004
.0004
.0041
.0001
.0127
.4172
.0109
.3398
.4618
1419
.0562
.1528
3
0.
0.
0.
0.
0.
0.
0.
0.
-0.
723.
8.
105.
279.
11.
8.
21
8000
.2800
.0000
.0000
.0071
.0047
.0016
.2720
0008
.0300
0000
.0000
.0000
.0000
5000
.5000
4300
4
1.
0.
0.
0
0.
0.
0.
0.
0.
1003.
8.
109,
283,
12.
9
22.
9000
.8000
.1000
.2000
0117
.0084
.0055
.3075
0021
.0700
0000
.1000
.0000
.0000
.7000
.1000
.7000
-------
VARIABLE
A-15
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOSJT
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
6
0
6
6
6
6
6
6
6
6
6
5
6
6
6
3
6
6
0
0
0
0
0
11
0
12
12
12
12
12
12
12
12
12
9
12
11
12
11
12
12
0
0
0
0
0
Bftt>in-ft_[
1
0
-0
0
o
0.
0.
0.
0.
768.
8.
7.
78.
206.
13.
5.
16.
RBCTM— A K
DrtDJ.IN~/l P
0.
0.
-0.
0.
0.
0.
0.
0.
0.
801.
7.
7.
77.
202.
13.
5.
16.
MUKlHfcK
.7500
.8883
.0167
.0030
.0021
.0008
.3355
.0008
.0133
.8333
.0280
.9533
.5833
.5000
.2333
.3333
0500
inDTHFD
»UK1 n&K
7500
7975
0992
0037
0023
0008
3038
0032
1483
3333
9611
9008
2273
5833
2818
5833
1167
N bUKVt*
0
0
0
0
0
0
0
0
0
4
0
0
0
1
0
0
0
H QTTDWI7V-
IN oUKVCi 1 •
0
0
0
0
0
0
0
0
0
26
0
0
0
2
0
0
0
.2739
.1288
.0582
.0003
.0006
.0004
.0060
.0004
.0082
.0208
.0148
.0662
.4916
.9748
.1528
.0816
.1225
ALJTMTC'D O
H1IN 1 CiK^
.5916
.2411
.0896
.0021
.0004
.0002
.0492
.0026
.0422
.6538
.0732
.0329
.9045
.3533
.3783
.2250
.4407
LAYtil
0
0
0
0
0
0
0
0
0.
1
0
0
0
0
0
0
0.
<=B_t;f IL.
.1118
.0526
.0238
.0001
.0003
.0002
.0024
.0002
.0033
.6415
.0066
.0270
.2007
.8062
.0882
.0333
.0500
1MN1UN
1
0
-0
0
0
0
0
0
0
762
8
7
78
204
13
5
15
.5000
.7000
.1200
.0026
.0015
.0005
.3290
.0000
.0100
.0000
.0100
.8800
.0000
.0000
1000
.2000
.9000
2
1
0
0
0
0
0
0
0
772
8
8
79
208
13.
5
16.
.0000
.1000
.0500
.0034
.0033
.0016
.3430
.0010
.0300
.0000
.0500
.0400
.0000
.0000
.4000
.4000
.2000
T SVC"D D I7DTT TUWmKT
LAibK-b tfiLIMNlON
0.1784 0
0.
0.
0.
0.
0.
0.
0.
0.
7.
0.
0.
0.
0.
0.
0.
0.
0696
0259
0006
0001
0001
0142
0007
0122
6943
0244
0095
2727
6793
1141
0649
1272
0
-0
0
0
0
0
0
0
748
7
7
75
198
12
5
15
.0000
.3500
.3000
.0028
.0018
.0005
.2000
.0010
.1000
.0000
.8300
.8600
.5000
.0000
.6500
.3000
.5000
2
1
0
0.
0
0
0
0
0
837.
8.
7.
78.
205.
13.
6
16
.0000
. 2300
.0000
.0103
.0032
.0013
.3360
.0100
.2500
.0000
.0400
.9800
.0000
.0000
.8500
.2000
.7000
-------
A-16
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS T
PHOS^D
D^ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W__TEMP
TURBTY
CHLOR A
PHPHT_A
PHOS T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
58
56
58
58
57
57
58
58
33
57
58
57
0
58
58
1 1
53
58
0
0
0
0
23
36
36
36
36
36
36
36
36
36
36
36
36
0
36
36
36
35
36
16
16
16
16
11
1
0
0
0
0
0
0
0
0
0
772
8
76
202
13
5
15
1
R A CITM— a
D t\ iD J. IN — rt
17
0
0
0
0
0
0
0
0
0
421
8
75
198
9
5
15
26
7
3
0
12
nun i nc,KiN
.4560
.3873
.7814
.0172
.0033
.0013
.0003
.3021
0022
0763
8448
.0000
.4983
6534
3718
4057
.8897
.4348
MDRTHFRM
INUrx i n CjitPt
6500
2082
.9986
.1687
.0028
.0019
.0003
.2668
.0018
1590
.6667
.4247
.0869
9028
.8362
.2264
.7383
.2500
.1000
.3437
.8681
.6273
auKvni
0
0
0
0
0
0
0
0
0
0
19
0
1
1
0
0
0
0
CITDUF V
rJUKV t, I
0
0
0
0
0
0
0
0
0
0
86
0
2
6
0
0
0
1
0
0
0
23
.2616
. 1426
.5878
. 1539
.0018
.0005
.0003
.0265
.0009
.0546
.9638
.0986
0501
. 1442
. 3759
.3805
.4081
.8435
CCIIMMC
bUMMt
7458
0807
6407
1770
.0038
.0035
0003
.0266
.0012
.0583
.0764
.0538
.9268
.8812
.6583
.2533
.6524
. 1255
.2658
. 1153
.0229
.1017
llj LftYtK
0
0
0
0
0
0
0
0
0
0
2
0
0
0
0
0
0
0
^R LAYER
0
0
0
0
0
0
0
0
0
0
14
0
0
1
0
0
0
0
0
0
0
6
= D tfitiinniuiN --
.0343 0.
.0190
.0772
.0202
.0002
.0001
.0000
.0035
0001
.0072
6214
0131
1379
1502
1133
0523
0536
0.
0.
-0.
0.
0.
-0
0.
0.
0.
740
7.
74.
200.
12.
5.
15.
1759 1.
-B FPILIMNI ON - -
.1243 15.
0134 0
1068
0295
.0006
.0006
.0001
.0044
0002
.0097
3461
.0090
4878
.1469
. 1097
0428
. 1087
.2814
.0665
.0288
.0057
.9654
0
-0.
0
0
-0
0
0
0
242.
8.
66.
180.
9.
4 .
13,
24
6.
3
0
0,
9000
2100
,2000
2000
,0022
0000
0002
2440
0010
0100
0000
,8000
5000
0000
8500
2000
2000
0000
7000
1200
4000
1000
0008
0000
0001
2100
0000
0500
0000
,3100
.0000
,0000
,0000
,6000
,5000
.0000
.6000
.1000
.8200
.9000
1.
1.
1.
0.
0.
0.
0.
0.
0.
0.
806.
8.
79.
204.
13
8.
17.
4.
18.
0.
4.
0.
0.
0.
0.
0.
0.
0.
536.
8.
79
205.
11.
5
16
28
7.
3
0
81
8000
1400
8000
9000
0146
0032
0009
3310
0050
2700
0000
2700
0000
0000
8800
0000
0000
0000
8000
5700
2000
6000
0182
0169
0011
.3050
,0040
.3500
,0000
,5100
.0000
.0000
,3000
.6000
.7000
.0000
.5000
.5000
.9000
.0000
-------
A-17
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
WJTEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
17
17
17
17
17
17
17
17
17
17
17
17
0
17
17
17
17
17
0
0
0
0
0
12
0
1
0
0
0
0
0
0
0
495
8
75
201
12
5
15
jKinnKN
.0647
.2384
.6074
.2059
.0029
.0011
.0003
.2840
.0023
.1888
.9412
.4188
.5812
.0147
.2959
.2471
.9265
D 71 C?TM — TV Mr»DTUl7DM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
29
29
29
29
29
29
29
29
29
29
29
29
0
29
29
29
29
29
0
0
0
0
5
oruj-ii — rv m_;r\i IIILIMI
5.0862
0.
1
0
0.
0.
0.
0.
0
0
684
8.
76
204
12
5
16
9
.2866
.4741
.3629
.0028
.0015
.0004
.3232
.0033
.1291
.6552
.1269
.2241
.4097
.5597
.3224
.0500
.8000
SUKVC.X =1
1
0
0
0
0
0
0
0
0
0
78
0
1
4
0.
0.
0.
QTTRWP'V — f
oU K v 1 1 — I.
0.
0.
0.
0.
0.
0
0
0.
0
0
90
0
0
1
0
0
0
5
-_ounnE,K
.0805
.0528
.7079
.3015
.0013
.0006
.0005
.0227
.0013
.0766
.1573
.0834
.7438
.0625
.9846
.2239
.4402
0
0.
0.
0.
0.
0.
0.
0.
0.
0.
18.
0.
0.
0.
0.
0.
0.
._MtbULlWNiUlN --
2621 9.
0128
1717
0731
0003
0002
0001
0055
0003
0186
9559
0202
4229
9853
2388
0543
1068
0.
0.
-0.
0.
0.
-0.
0.
0.
0.
346.
8.
71 .
194.
10.
4.
15.
1000
1600
5000
7000
0011
0000
0001
2530
0010
0700
0000
2200
0000
0000
8000
8000
0000
13.
0.
3.
0.
0.
0.
0.
0.
0.
0
627.
8.
77.
206.
14.
5.
16.
7000
3300
2000
7000
0058
0028
0017
3270
0060
4000
0000
5900
5000
0000
1000
5000
4000
1 SUMMER T RVirr>-r* uvnr>T TUMmM
.7958
.0880
.8129
.2040
.0011
.0008
.0004
.0209
.0021
.0474
.2707
.0953
.9410
.2105
.5529
.1544
.2928
.4037
Lin i c.r\ — L
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
16.
0.
0.
0.
0.
0.
0.
2
i n i rwjj j. rui j. wit
1478 4.
0163
1510
0379
0002
0002
0001
0039
0004
0088
7629
0177
1747
2248
1027
.0287
.0544
.4166
0.
0.
0.
0.
0.
0.
0.
0.
0.
535.
7.
74.
201.
11.
5
15
3
0000
1400
4000
1000
0003
0003
0000
2770
0000
0400
0000
9200
.0000
.0000
.4000
.0000
.3000
.0000
6.
0.
3.
0.
0.
0.
0.
0.
0.
0.
855.
8.
77.
206.
13.
5
16
16
6000
6100
6000
9000
0055
0040
0015
3580
0090
2400
0000
2700
.5000
.0000
.9000
.5000
.6000
.0000
-------
A-18
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W TEMP
TURBTY
CHLOR__A
PHPHT_A
PHOS T
PHOS_D
D^ORTH_P
ND2N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB PH
T ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
K TEMP
TURBTY
CHLOR^A
PHPHT_A
PHOS^T
PHOS_D
D_ORTH_P
N02NO3T
NH3NH4T
KJEI^N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
34
34
34
34
34
34
34
34
34
34
34
34
0
34
34
34
34
34
17
17
17
17
6
J 5
15
15
15
14
15
14
15
15
15
15
15
0
15
15
15
15
15
0
0
0
0
13
EttbllN-rt
4
0
0
0
0
0
0
0
0
0
976
7
76
204
11
5
16
26
7
3
0
8
D 7\ Q TM- A
Drio 1 IN — 1\
i
0
0
0
0
0
0
0
0
0
631
8
76
204
11
5
15
5
1NUK 1ME.KIN
. 1412
.9161
.6625
.4221
.0033
.0013
.0006
.3538
0022
1242
.6471
.9794
.5824
8444
9318
.3757
1250
9412
2706
.3882
.8935
1667
HDRTHPRM
IN UK i rlljKiN
9400
2078
5800
0917
0029
0011
0000
3080
.0025
.0883
.7333
.0875
. 1007
9673
.3187
. 1983
.7560
.1538
SUKVtl
0
0
0
0
0
0
0
0
0
0
126
0
1
0
0
0
0
0
0
0
0
5
CMp\7I7 V
OUKV t. I
0
0
0
0
0
0
0
0
0
0
30
0
0
2
0
0
0
4
2285
.5474
.3350
.3877
.0016
.0005
.0005
.0139
.0016
.0524
.5749
0827
.0689
9184
4749
1439
2711
8269
1263
0928
.0262
8793
— n P Q T T
-LJ r rthL
2131
0302
1612
0890
0007
.0003
0004
.0122
.0013
0535
5929
0713
.4163
.1767
.2298
. 1255
.4366
.4130
0.
0.
0.
0.
0.
0.
0.
0.
0
0
21
0
0.
0.
0.
0
0.
0.
0.
0.
0.
2
1 TflVPD — R
1 Li A 1 1, K ~ D
0.
0
0
0
0
0
0
0
0.
0
7.
0.
0.
0.
0.
0.
0.
1 .
t, Nht'Ht.LUiU
0392
0939
0575
0665
0003
0001
0001
0024
0003
0090
7074
0142
1833
1575
0814
0247
0465
2006
0306
0225
0064
4002
EP I L IMNION
0550
0078
0416
0230
0002
0001
0001
0031
0003
0138
8990
0184
1075
5620
0593
0324
1127
2239
3
0.
0.
0.
0
0.
0
0.
0.
0.
759.
7
74.
203
10.
5
15.
26
7.
3.
0.
3.
7
0
0
0.
0
0
-0
0
0
0
599
7
75
199
11
5
14
2
9000
4125
2000
0750
0013
0003
0000
3275
0000
0300
0000
8200
0000
0000
8000
0000
.3500
0000
.1000
.2000
.8500
.0000
6000
1700
1000
.0000
0018
0005
0003
2922
.0010
.0000
.0000
.9400
.0000
.8800
0900
.0000
.8800
0000
4.
3.
1 .
2.
0.
0.
0
0.
0.
0.
1344.
8
78
207.
12.
5.
16.
28.
7 .
3.
0.
17.
8.
0.
0
0.
0
0
0
0
0
0
687
8
76
207
12
5
16
19
8000
4000
4000
4000
0088
0024
0017
3770
0060
2500
0000
1200
0000
0000
6000
5250
6000
0000
4000
.5000
.9600
.0000
.2000
. 2600
7000
. 2250
0039
.0017
.0009
.3280
.0060
1800
.0000
.1700
.7000
.0000
.0000
.4000
.3000
.0000
-------
A-19
VARIABLE
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
6
6
6
6
6
6
6
6
6
6
6
6
0
6
6
6
6
6
0
0
0
0
0
10
10
10
10
9
9
10
10
10
10
10
10
0
10
10
10
10
10
0
0
0
0
5
• BflblN-A NUKTHEKN
6.3000
0.2417
0.2333
0.1333
0.0023
0.0011
0.0003
0.3380
0.0020
0.0567
800.3333
7.9650
76.3500
205.7500
11 .6833
5.2167
15.8167
D7VCTM — B MflDTHC'DM
Drto J.PJ — 1\ NUK 1 Mt,KN
4.5800
0.3550
0.1400
0.0400
0.0022
0.0014
0.0003
0.3556
0.0014
0.0620
958.1000
7.9000
76.0700
205.8000
11.9400
5.2000
15.8400
25.4000
SUKVEY=D_FALL1
0.7823
0.0585
0.1211
0.0816
0.0005
0.0002
0.0005
0.0221
0.0015
0.0742
81 .7476
0.0596
0.7477
1.3323
0.1169
0 1329
0.3764
CIIDWI7V — n CRT T 1
bUKVhY-U_r ALL1
0.4849
0.1227
0.0699
0.0843
0.0006
0.0006
0.0004
0.0149
0.0010
0.0459
73.5866
0.0359
0.7258
1.1353
0.1265
0.1155
0.3748
41.2953
LAYER=C_MESOLIMNION
0.3194 5.3000
0.0239
0.0494
0.0333
0.0002
0.0001
0.0002
0.0090
0.0006
0.0303
33.3733
0.0243
0.3052
0.5439
0.0477
0.0543
0.1537
0. 1800
0.1000
0.0000
0.0016
0.0007
-0.0003
0.3050
0.0010
-0.0700
707.0000
7.8800
75.0000
203.5000
11 5000
5.0000
15.4000
7.3000
0.3400
0.4000
0.2000
0.0027
0.0013
0.0011
0.3630
0.0050
0.1300
924.0000
8.0300
77.0000
207.0000
11.8000
5.4000
16.3000
LAYER=D_HYPOLIMNION
0.1533 4.1000
0.0388 0.1800
0.0221
0.0267
0.0002
0.0002
0.0001
0.0047
0.0003
0.0145
23.2701
0.0114
0.2295
0.3590
0.0400
0.0365
0.1185
18.4678
0. 1000
-0.1000
0.0012
0.0007
-0.0003
0.3310
0.0010
-0.0300
795.0000
7.8600
75.0000
203.5000
11.8000
5.0000
15.4000
4.0000
5 7000
0.5600
0.3000
0.1000
0.0032
0.0026
0.0008
0.3780
0.0040
0. 1100
1033.0000
7.9700
77.0000
207.0000
12.2000
5.3000
16.5000
99.0000
-------
A-20
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W__TEMP
TURBTY
CHLOR^A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ AI.K
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W TEMP
TURBTY
n-irrt A
PHPHT A
PHOS T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
12
11
12
12
12
12
12
12
12
12
12
12
0
12
12
12
12
12
0
0
0
0
6
26
26
?f>
26
26
26
26
26
26
25
26
26
0
26
26
26
26
26
0
0
0
0
0
4
0
0
0
0
0
0
0
0
0
1032
7
76
205
11
5
15
9
D A C T \1 - A
DrVo 1 IV — M
6
0
0
0
0
0
-0
0
0
0
746
7
76
201
12
5
16
_INUKiHtKr
.2583
.5736
.0729
.1146
.0031
0014
0007
. 3628
.0019
.0646
0000
8508
1542
4775
9833
2250
6792
.6667
N n R T H P P N
INUK J. !1 Ci K.rJ
1808
4310
2962
0827
0038
.0009
0000
.3007
.0020
. 1199
.9615
.9535
.3992
9042
.4704
.3702
.6792
1 bUKVt,
0
0
0
0
0
0
0
0
0
0
25
0
0
0
0
0
0
10
C* II D\7tT V
oUKv t, I
0
0
0
0
0
0
0
0
0
0
86
0
0
2
0
0
0
K-U_fALLJ
.1881
.0881
0445
.0588
.0006
.0004
.0003
0163
.0016
.0652
8668
.0446
.7266
.8585
1801
1138
4186
.5767
DP & T T O
c f\LL Z
6609
1 774
1417
0710
0012
.0008
0010
0130
.0008
.0567
.9025
0752
.8193
.0807
.4221
. 1667
.8311
L LAYER
0
0
0
0
0
0
0
0
0
0
7
0
0
0
0
0
0
4
LAYER"
0
0
0
0
0
0
0
0
0
0
17
0
0
0
0
0
0
.0543
0266
.0129
.0170
0002
.0001
0001
0047
.0005
.0188
.4671
0129
2097
2478
0520
0329
1208
3179
B E P I L
. 1/96
0348
0278
01(9
0002
0002
0002
.0025
0002
0113
0430
.0148
1607
.4081
.0828
.0327
.1630
HELOiU
4 .
0.
0.
0.
0.
0.
0.
0
0.
-0.
991 .
7 .
74.
204.
11 .
5.
15
3.
IMNION
4
0
0
0.
0.
0
-0
0,
0.
0,
643.
7.
75
197.
11.
5.
15.
. 1000
.4000
.0000
.0000
.0023
.0009
.0003
3372
0000
.0400
.0000
.7700
.7500
.2300
.8000
.0000
0000
,0000
7000
2700
1000
.0000
.0017
0000
0009
.2790
.0003
.0400
.0000
.7800
0000
.5000
.8000
1500
.5000
4.
0.
0.
0
0
0
0.
0.
0.
0.
1074
7.
77
207.
12.
5.
16
31.
6.
0.
0.
0
0
0
0
0.
0
0
928
8
78
205
13
5.
17
7000
6800
1000
2000
0045
0021
0011
3890
.0050
. 1400
0000
.9100
0000
.0000
.4000
.3000
3500
.0000
.9000
.9875
.5000
2250
.00Gb
0027
0044
.3330
.0040
.3200
0000
.0300
.2000
.3500
.5000
.7000
.9000
-------
VARIABLE
A-21
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
Hi
6
0
6
6
6
6
6
6
6
6
6
5
6
6
6
3
6
6
0
0
0
0
0
DJ
or
6
0
6
6
6
6
6
6
6
6
6
5
6
6
6
6
6
6
0
0
0
0
0
rtblIN = B bUUTHKKN
2.0000
0.8550
0.0233
0.0048
0.0030
0.0019
0.3313
0.0015
0.1167
712.8333
8.0840
8.0567
78.5833
206.0000
12.4000
5.3333
15.9000
B^nilTHRRM c
DLJU 1 ncKIN L
0.1667
1.3017
-0. 2150
0.0050
0.0020
0.0009
0.3293
0.0067
0. 1383
798.6667
7.9080
7.9517
78.4167
205.1667
13.5583
5.6833
16.5167
bUKVt;Y=A_WiNTERI
0.7746
0.1005
0.0948
0.0014
0.0013
0.0010
0.0027
0.0005
0.1277
7.3598
0.0792
0.0216
0.3764
0.0000
0.2000
0 1033
0.2280
AU THTPD "5
n if4 i C.KZ
0.2582
0 3225
0.1115
0.0044
0.0004
0.0004
0.0060
0.0031
0.0286
9.6885
0.0130
0.0360
0.5845
1.4720
0.3338
0.0408
0.2787
LAYER=B_EPILIMNION
0.3162 1.0000
0.0410
0.0387
0.0006
0.0005
0.0004
0.0011
0.0002
0.0521
3.0046
0.0354
0.0088
0.1537
0.0000
0.1155
0.0422
0.0931
0.7000
-0. 1000
0.0038
0.0022
0.0008
0.3270
0.0010
0.0100
707.0000
7 .9600
8.0300
78.0000
206.0000
12.2000
5.2000
15.5000
2.5000
1.0100
0.1600
0 0075
0.0056
0.0038
0.3330
0.0020
0.2800
722.0000
8. 1500
8.0900
79.0000
206.0000
12.6000
5.5000
16.1000
LAYER-B EPILIMNION
0.1054 0.0000
0.1316
0 0455
0.0018
0.0002
0.0002
0.0025
0.0013
0.0117
3.9553
0.0058
0.0147
0.2386
0.6009
0.1363
0.0167
0.1138
0.8800
-0.4000
0.0028
0 0014
0.0003
0.3200
0.0020
0.1200
788.0000
7.8900
7.9200
77.5000
203.0000
12.9500
5.6000
16.2000
0.5000
1.5800
-0.1000
0 0140
0.0024
0.0015
0.3360
0.0110
0.1800
812.0000
7.9200
8.0200
79.0000
207.0000
13.8500
5.7000
16.9000
-------
A-22
L HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOSJT
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_ COUNT
W_TEMP
TIRBTY
CHLOR_A
PHPHT A
PHOS_T
PHOS D
D^ORTH P
N02N03T
NH3NH4T
KJEL N
DSICON
PH
LAB PH
T^ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
45
45
45
45
45
45
45
45
20
45
45
45
0
45
45
8
45
45
0
0
0
0
16
29
29
29
29
28
29
29
29
29
29
29
29
0
29
29
28
29
29
13
13
13
13
8
DrttJllN-D
1
0
1
-0
0
0
0
0
0
0
782
8
77
203
13
5
15
3
BASIN^B
19
0
1
0
0
0
0
0
0
0
338
8
77
206
9
5
16
27
7
3
0
29
suu i nc,KM
.7867
.5280
.0949
.0414
.0036
.0013
0005
.3009
.0025
1124
4222
0276
.5556
.3956
4512
3800
.6867
0625
CDHTHFRW
GUU 1 ritjKlN
6724
.2498
3560
1276
0023
0013
0005
.2764
.0014
.1984
.2069
.4403
.5821
.5390
.4085
.6336
.0769
.7692
.3769
.5744
.8995
.5000
SUKVC.I
0
0
0
0
0
0
0
0
0
0
13
0
1
1
0
0
0
1
C 1 Ipl/t1 V
o U K V c. I
0
0
0
0
0
0
0
0
0
0
69
0
1
6
0
0
0
0
0
0
0
22
.4578
.3277
.5353
.0973
.0017
.0006
.0004
.0205
.0006
.0571
3714
.0754
1083
.3186
2002
1342
4751
.8786
CCI1MMC
oUriMt
3854
0873
4173
.5346
.0006
.0006
.0004
.0177
.0011
.0895
5672
.1098
.0980
.5558
.7135
.2400
.4583
.7250
. 1363
.0829
.0251
.2133
-------
VARIABLE
A-23
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOSJT
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB^PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T__ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
Dfl
13
13
12
12
13
13
13
13
13
13
13
13
0
13
13
13
13
13
0
0
0
0
0
Df\i
19
19
19
19
19
19
19
19
19
19
19
19
0
19
19
19
19
19
0
0
0
0
4
i&lN = B_bUUlHtKN bUKVfc;Y=l
13.7538 1
0
2
0
0
0
0
0
0
0
479.
8.
77.
206.
11.
5.
16.
CTM — D cr
O.L1N-D OL
5.
0.
0.
0.
0.
0.
0.
0.
0.
0.
766.
8.
76.
205.
11.
5.
15.
27.
.2769
.7708
2458
.0030
.0012
.0006
.2972
.0036
1958
.3846
2998
1931
9908
4150
5615
0369
HITHFDK
I\J L nCjKr
7474
3391
9434
2934
0029
0012
0005
3342
0021
1716
7368
0118
6447
9474
7884
5145
7789
5000
0
3
0
0
0
0
0
0
0
69.
0.
1.
1
0.
0.
0.
I QTTDWPV — C
4 oUKVC. 1 -L
0
0.
0.
0.
0.
0.
0
0.
0.
0.
133.
0.
0.
1.
0.
0.
0.
11.
J bUMME
.3270
.0788
.0562
.3665
.0006
.0004
.0003
.0189
.0018
0969
.3380
.1185
1344
9498
7886
2190
3992
1 CHUMP'
. oUPlMt,
8065
1253
3571
6267
0008
0005
0003
0211
0030
0874
2065
1512
9476
8401
6601
1571
5808
1505
K LAYER=C_MESOLIMNION -
0.3681 10
0.
0.
0.
0.
0.
0.
0.
0.
0.
19.
0
0.
0.
0.
0.
0.
D T B VI7D n
K LnYhK-U
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
30.
0.
0.
0.
0.
0.
0.
5.
0219
8822
1058
0002
0001
0001
0052
0005
0269
2309
0329
3146
5408
2187
0608
1107
0
0
-0
0
0
0
0
0
0
358
8.
75.
204.
9.
5.
15.
.8000
.2100
.9000
.4000
.0020
.0008
.0000
.2670
.0010
.0700
.0000
.0700
.0000
.0000
6250
0000
4000
15
0
11
0
0
0
0
0,
0
0.
610.
8.
78.
211
12
5.
16.
.2000
.5150
.4000
.8000
.0042
.0019
.0012
.3325
0080
.3800
.0000
.4600
3800
0000
4300
8000
6000
HYPOLIMNION --
1850 4.
0287 0.
0819
1438
0002
0001
0001
0048
0007
0200
5597
0347
2174
4221
1514
0360
1332
5752
0.
-0.
0.
0.
0.
0.
0.
0.
574.
7.
75.
204.
10.
5.
15.
18.
4000
1800
4000
3000
0015
0005
0000
3090
0000
0700
0000
7600
0000
0000
1000
2000
0000
.0000
6.
0
I .
2.
0.
0.
0.
0
0.
0.
1027.
8.
78.
211.
12.
5.
16.
43
7000
5850
9000
6000
0050
0021
0011
3870
0080
3900
0000
4100
0000
0000
7000
.8000
.8000
.0000
-------
A-24
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
W TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_ COUNT
25
25
25
25
25
25
25
25
25
25
25
25
0
25
25
25
25
25
13
13
13
13
4
17
17
17
17
17
17
17
17
17
17
17
17
0
17
17
17
17
17
0
0
0
0
11
Drt^llN-B
4
1
0
0
0
0
0
0
0
0
1061
7
76
206
10
5
15
27
7
3
0
27
n A q TM - n
D t\ J 1 IN — D
8
0
0
0
0
0
0
0
0
0
716
8
76
207
11
5
16
9
^uuintKiN IDUKVC.):-
.8120 0
.1407
.8760
.3050
.0041
.0011
.0007
.3621
.0010
.1817
8800
8470
.5600
.7552
.9120
.5060
.9920
.3846
. 3692
4615
.8962
0000
QOTITPRPM C
oU U 1 ric-KPt o
2529
3140
5956
. 1515
.0030
.0008
.0005
.3275
.0031
0981
. 2353
.0722
4588
.0259
.2076
.3824
.3059
.8182
0.
0
0
0
0.
0.
0.
0.
0
164.
0
0.
1 .
0.
0.
0.
0.
0.
0.
0
8.
0
0
0
0
0.
0.
0.
0.
0.
0.
75.
0.
0.
0
0.
0.
0.
10.
u_t>uroMti
5869
6712
2962
5739
0014
0003
0003
0184
0015
1170
2235
0760
8578
6457
5659
1781
4020
7679
1251
0870
0299
2462
DP f. T r 1
r ML L 1
1772
0724
1160
1483
0008
0004
0007
0379
0011
0301
8556
1055
6890
7973
1628
1334
7903
1076
< LAYtK
0
0
0
0
0
0
0
0
0
0
32
0
0
0
0
0
0
0
0
0
0
4
LAYER=
0
0
0
0
0
0
0
0
0
0
18
0
0
0
0
0
0
3
1174
.1342
0592
. 1148
.0003
0001
0001
.0037
.0003
.0234
8447
0152
1716
3291
1132
.0556
0804
.2130
.0347
.0241
0083
. 1231
B EPILIMNION
0430
0176
0281
0360
0002
.0001
0002
0092
.0003
.0073
.3977
.0256
.1671
. 1934
.0395
.0324
.1917
.0476
4.
0.
0
-0.
0.
0.
0.
0.
0.
0
735.
7,
75.
204
9.
5
15
26
7
3
0
18
7
0
0
-0.
0
0
0
0
0
0
645
7
75
205.
10.
5
15.
2.
0000
4475
3000
.5000
.0009
.0008
.0003
.3160
.0000
0700
.0000
.7200
.0000
8800
.9000
. 2000
2000
0000
2000
.3000
8600
0000
8000
2400
3000
. 1000
0023
0003
.0000
2820
0010
0400
.0000
8600
.5000
.0000
.9300
.2000
.4500
.0000
6.
3.
1.
2.
0.
0.
0.
0.
0.
0.
1394.
8.
77.
211 .
12.
5.
16
28.
7
3
0.
38.
8
0
0
0
0
0
0
0
0
0
947
8
78
208
11.
5
17
38
2000
3400
5000
6000
0073
.0016
.0014
.3910
,0070
.5100
.0000
.0600
,5000
,0000
, 1000
.8000
.9000
.0000
.6000
.6000
.9400
.0000
.4000
.4600
.8000
4000
.0055
.0017
.0028
.4030
.0050
. 1500
.0000
.4000
.0000
.0000
.6000
.6000
.3000
.0000
-------
VARIABLE
A-25
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
WJTEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
3
3
3
3
3
3
3
3
3
3
3
3
0
3
3
3
3
3
0
0
0
0
0
3
3
3
3
3
3
3
3
3
3
3
3
0
3
3
3
3
3
0
0
0
0
2
• BrtSJ.N = B bUUTHhKN
6.9333
0
0
0
0
0
0
0
0
0
971
7
76.
207.
11 .
5.
16.
.4533
.2667
.1333
.0025
.0006
.0003
.3393
.0017
.0800
.6667
.8333
.5000
.0000
0333
3333
0667
DJVCTKT — R CnilTT-IPDM
BHOiPl — D C)UU 1 fit KIN
5.6000
0.5700
0.
0.
0.
0
0.
0.
0.
0.
1074.
7.
76.
207.
10.
5.
16.
4.
2000
1667
0032
0018
0006
3483
0013
0467
0000
7667
0000
3333
9333
3333
0667
5000
bUKVIiY =
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
130.
0.
0.
0.
0.
0
1.
CTIDWC" V —
bUKV t, i -
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
80.
0.
0.
0.
0.
0.
1.
0.
=U_rALL
2309
2157
1155
2517
0002
0003
0003
0727
0006
0529
8485
0666
0000
8660
2082
1528
0786
DC1 A I T
r ALL
4359
1609
1000
1155
0004
0012
0003
0711
0006
0306
7217
0289
0000
5774
1528
1528
0786
7071
,1 LAYER=C_MESOLIMNION -•
0.1333 6
0.
0.
0.
0.
0.
0.
0.
0.
0.
75.
0.
0.
0.
0.
0.
0.
1 LAYER-D
0.
0.
0
0.
0.
0
0
0.
0.
0.
46.
0.
0.
0.
0.
0.
0.
0.
1245
0667
1453
0001
0002
0001
0420
0003
0306
5454
0384
0000
5000
1202
0882
6227
0
0
-0
0
0
0
0
0
0
869
7
76
206
10.
5
15.
.8000
3000
.2000
.1000
.0023
.0003
.0000
2920
.0010
.0200
0000
.7600
.5000
.0000
.8000
2000
.3000
7
0
0
0.
0.
0.
0.
0.
0.
0.
1119.
7.
76.
207.
11.
5.
17.
.2000
.7000
.4000
.4000
.0027
.0008
.0005
.4230
,0020
.1200
0000
8900
5000
5000
2000
5000
3000
HYPOLIMNION --
2517 5.
0929 0.
0577
0667
0002
0007
0002
0410
0003
0176
6047
0167
0000
3333
0882
0882
6227
5000
0.
0.
0.
0.
0.
0.
0.
0.
984.
7.
76
207.
10
5.
15.
4.
3000
4400
1000
1000
0027
0009
0003
2950
0010
0200
0000
7500
0000
0000
8000
2000
3000
.0000
6.
0.
0.
0.
0.
0.
0.
0.
0.
0.
1140.
7.
76.
208.
11.
5.
17.
5.
1000
7500
3000
3000
0035
0032
0008
4290
0020
0800
0000
8000
0000
0000
1000
5000
3000
0000
-------
A-26
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR^A
PHPHT_A
PHOSJT
PHOS_D
D_ORTH^P
N02N03T
NH3NH4T
KJEL^N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR A
PHPHT_A
PHOS_T
PHOS D
D_ORTH_P
N02N03T
NH3NH4T
K,TEL_N
DSICON
PH
LAB_PH
T_ ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
4
4
4
4
4
4
4
4
4
4
4
4
0
4
4
4
4
4
0
0
0
0
3
23
22
23
23
23
23
23
23
23
23
23
21
0
22
22
23
23
23
0
0
0
0
0
Drti3.Lrt-D
5.
0
0.
0.
0.
0.
0.
0.
0.
0.
1110.
7
76
207.
10.
5
15
7.
R aCTH R Q
DrtO-LlN — D o
6
0
0
0.
0.
0.
-0.
0,
0
0.
740.
8.
77.
204.
10.
5.
16.
auuincnrt
3000
7100
1500
1750
0039
0015
0005
3532
0015
0875
0000
7600
22SO
6250
9500
2500
8000
6667
nilTHFPM
UU 1 ntKlN
9000
4153
4022
0511
0037
0021
0005
2969
0025
1324
6522
0142
2814
4050
8309
4413
6070
aunvc.
0
0
0
0
0
0
0
0
0
0
78
0
0
0
0
0
1
2
QIIDWC1 V
bUKV 1. 1
0
0
0
0
0
0
0
0
0
0
40
0
0
1
0
0
1
.4761
.1344
.0577
.0957
.0003
.0006
.0002
.0472
.0010
.0171
.4049
.0346
2062
.4787
.1291
.0577
.0132
5166
— n IT n T T ">
-U r ALLZ
.1679
.0959
1601
.0827
.0008
.0010
.O005
.0213
.0008
.0344
.1142
.0458
.9947
.1202
.6465
.0973
.1623
L IjAXHK
0
0
0
0
0
0
0
0
0
0
39
0
0
0
0
0
0
1
LAYER -
0
0
0
0
0
0
0
0
0
0
8
0
0
0
0
0
0
.2380
.0672
.0289
.0479
.0001
.0003
.0001
.0236
.0005
.0085
.2025
.0173
1031
.2394
.0645
.0289
.5066
.4530
B E P I Ii
.0350
0204
0334
0173
.0002
.0002
.0001
.0044
.0002
.0072
.3644
.0100
.2121
. 2388
.1348
.0203
.2424
nr.i*uiu
5.
0.
0.
0.
0.
0.
0.
0.
0.
0.
994.
7
76
207.
10.
5.
15.
5.
IMNION
6.
0.
0.
-0.
0
0
-0.
0
0
0
684
7
75
201
10
5
14
0000
6200
1000
1000
0035
0010
0003
3210
0010
0700
0000
7300
0000
0000
8000
2000
1000
.0000
.7000
.2900
.2000
.1000
0028
.0011
.0009
.2570
.0017
.0700
.0000
.9200
.0000
.5000
.2000
.3000
.8000
6.
0.
0.
0.
0.
0.
0.
0.
0.
0.
1166
7
76
208.
11
5
17
10
7
0
0
0
0
0
0
0
0
0
819
8
79
206
12
5
17
0000
9100
2000
3000
0042
.0024
.0008
.4230
.0030
.1100
.0000
.7900
.5000
.0000
.1000
.3000
.3000
.0000
.3000
.6475
.7000
.2000
.0059
.0061
.0004
.3282
.0040
.1800
.0000
.0800
.0000
.0000
.2000
.6000
.9000
-------
A-27
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
0
0
0
0
0
DrtOllN-D :
6
0
0
0
0
0
-0.
0
0
0
944
7
78
200
10.
5
15
P fi C TM — 13 t
DAbiH— D i
5
0
0
0
0
0
-0.
0
0
0
1104
7
78
206
11
5
15
3UU 1HC.K
.5000
.4200
.2000
.0000
.0030
.0021
.0009
.3410
.0010
.1300
.0000
.8900
.0000
.0000
.2000
.5000
.6000
""miTf-IITD
3
-------
A-28
L. HURON DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W^TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOSJI
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
2
2
2
2
2
2
2
2
2
2
2
2
0
2
2
2
2
2
0
0
0
0
0
DftOlH-D
5
0
0
0
0
0
0.
0.
0.
0.
1138.
7.
78.
205.
9
5.
15.
SUU 1 n&KN
.1000
.7150
.1000
.0500
0037
.0033
.0000
.3610
.0010
.0800
.0000
,7400
.0000
.3500
8500
.5000
.6500
3 U K V G I = U_f HL L Z
0.0000
0.
0
0.
0.
0.
0.
0.
0
0
18
0
0
1 .
0.
0.
0
.0636
.0000
.0707
.0006
.0017
.0000
.0057
0000
0141
3848
0283
0000
6263
0707
0000
0707
lifl!(C.K = t Nf.fHe.LULU
0.0000 5
0.
0.
0.
0.
0.
0.
0.
0.
0.
13.
0.
0.
1.
0.
0.
0.
.0450
.0000
.0500
.0004
.0012
0000
.0040
.0000
.0100
.0000
.0200
.0000
.1500
.0500
.0000
.0500
0
0
0
0.
0.
0.
0.
0
0
1125
7
78
204
9
5
15
.1000
.6700
. 1000
.0000
.0033
.0021
.0000
.3570
.0010
.0700
.0000
.7200
.0000
.2000
.8000
.5000
.6000
5.
0.
0.
0.
0.
0
0
0
0.
0
1151.
7,
78.
206.
9.
5
15
.1000
.7600
.1000
.1000
.0041
.0045
.0000
.3650
.0010
0900
.0000
.7600
.0000
.5000
.9000
.5000
7000
-------
A-29
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
STD ERROR
MINIMUM
MAXIMUM
WJTEMP
TURBTY
CHLOR^A
PHPHT_A
PHOS_T
PHOSJ3
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
6
0
6
6
6
6
6
6
6
6
6
5
6
6
6
3
6
6
0
0
0
0
0
6
0
6
6
6
0
6
6
4
6
6
5
6
6
6
6
6
6
0
0
0
0
0
DrtDlH-rt HC.O1C.KN
0.0000
3.4883
0.8117
0.0168
0.0039
0.0019
0.5115
0.0645
0.0717
710.3333
7.9480
7.9667
87.0000
260.1667
13.6000
14.0000
21.0167
BASIN-A WESTERN
0.0000
2.1433
0.1183
0.0082
0.0016
0.4575
0.0145
0.2033
637.6667
8.2080
7.8883
85.8333
263.8333
14.2633
11.3500
18.9833
DUKVCiI-rt V* -UN 1 C. K 1
0.0000
2.5852
0.8377
0.0049
0.0014
0.0014
0.0315
0.0683
0.0631
248.0755
0.1293
0.0468
1.7889
12.2706
0.3123
2.3707
2.0459
CIIDUFV — R UJTMTC'DO
bURvb I -A_WlNln.KZ
0.0000
0.9983
0.0643
0.0033
0.0015
0.0762
0.0130
0.0931
59.0886
0.0887
0.0714
2.3805
20.8654
0.4683
1.7237
1.2156
bttl&K-D GfJ-ljlK
0.0000
1.0554
0.3420
0.0020
0.0006
0.0006
0.0128
0.0279
0.0257
101.2764
0.0578
0.0191
0.7303
5.0094
0.1803
0.9678
0.8352
IW1U1V
0.0000
1.3200
0.0300
0.0098
0.0026
0.0008
0.4720
0.0160
0.0100
413.0000
7.7900
7.9000
84.5000
252.0000
13 .3500
11 .3000
18.5000
0.0000
7.0000
2.2000
0.0223
0.0064
0.0038
0.5430
0. 1640
0. 1600
969.0000
8.0700
8.0200
88.5000
276.0000
13.9500
16.7000
23.3000
T TV VC"D — R C"DTT TMMT riM —
L/ii tK-O tlrlli IMlNlUn
0.0000 0.0000
0.4076
0.0263
0.0013
0.0006
0.0311
0.0065
0.0380
24.1228
0.0397
0.0291
0.9718
8.5183
0.1912
0.7037
0.4963
0.5300
0.0500
0.0036
0.0005
0.3600
0.0010
0.1100
566.0000
8.0900
7.8000
83.0000
244.0000
13.4300
9.1000
17.9000
0.0000
3.3600
0.2200
0.0120
0.0042
0.5510
0.0280
0.3200
703.0000
8.2900
7.9700
89.0000
299.0000
14.6500
12.8000
20.9000
-------
A-30
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOSJD
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T^ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T__COUNT
W__TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS T
PHOSJD
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
B
14
14
14
14
14
14
14
14
12
14
14
14
0
14
14
14
14
14
0
0
0
0
3
R A
Dr\
4
4
4
4
4
4
4
4
4
4
4
4
0
4
4
4
4
4
0
0
0
0
2
ftblIN-n_HC.b JC.KIN bUKVt*-
11.9857 1
6,
5
0
0
0
0
0
0,
0.
633.
8,
86
256
11
13
20
.3929
.8482
.3100
0207
.0039
0010
.6987
.0205
. 1836
.0714
.2984
4321
. 1500
7500
.1089
.3893
3666 0000
^ T M — ft WPCTRRM
i3 1 IN — f\ HLi O 1 C.K1N
11 .0000
6 8125
2
0
0
0
0
0
0
0
679
8
85
250
11
12
19
699
.9500
.2500
.0198
.0034
.0010
.7080
.0225
1425
.2500
. 1950
.5000
.8750
5625
.0500
.5000
.5000
1
3
0
0
0
0
0
0
0
166
0
3
15
0
2
1
3138
CIlD\/pV R
oUKVCi I — D
1
1
1
0
0
0
0
0
0
0
150
0
3
14
0
3
1
849
D bFKJ.N'
.1883
.4498
.3532
.3666
.0039
.0020
.0010
.1638
.0319
.0673
.8682
.2148
.3644
0897
7198
4060
.8793
.5455
CD D T NTP
Or KlINLj
.7263
7609
9227
.2380
0059
.0010
.0005
. 1480
.0192
.0818
.0208
.1047
.9370
.9687
.6343
.1544
.2832
.2352
\ii LflYtK
0
0
0
0
0
0
0
0
0
0
44
0
0
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0
0
0
0
0
0
0
0
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75
0
1
7
0
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0
600
-U_t,f ILIMNIUN --
.3176 10.
.3875
.8962
.0980
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.0005
.0003
.0438
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.5974
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. 1924
.6430
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CMC" C("lT T d
MrLbUL IF
.8631
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9613
1190
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0.
0.
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0.
0.
0.
461.
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82.
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10.
10.
19,
98
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9
4
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0
0
0
0
0
0
0
469
8
81
232
10
8
18
99
7000
8200
0000
3000
0160
0021
0002
4090
0060
1000
0000
9800
5000
,5000
,6000
,4000
.2000
.0000
.3000
.7000
6000
.1000
.0133
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0110
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.0600
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12
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6000
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.8210
.0510
.2300
.0000
.3100
.0000
.0000
.1500
.2000
.4000
.0000
-------
A-31
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
5
5
5
5
5
5
5
5
5
5
5
5
0
5
5
5
5
5
0
0
0
0
0
3
3
3
3
3
3
3
3
3
3
3
3
0
3
3
3
3
3
0
0
0
0
3
DttDlH-rt HtlD 1 C.K1N &UKVC,X=£)
8.4200 1.
6
4
0
0
0
0
0
0
0
688
8
85
254
11
13
19.
.5080
.2600
.3500
.0194
.0039
.0015
.7671
.0543
.2140
.2000
.1305
4000
.2500
4300
0800
.7400
D B C TM — i UFCTTDW
DnOllN — H WCiO 1 CiKIN
7.1667
6.9167
1
0.
0.
0,
0,
0,
0.
0.
744.
8.
86.
258.
11.
13,
19.
613
.7333
.0667
.0223
.0051
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.7667
.0437
.1500
.0000
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.1667
.6667
.4333
8000
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1.
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1
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4237
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or Kirll.
4224
9079
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0.
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' HYPUL1MN1UN --
6367 6
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8212
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1966
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7
81
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11
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120
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7000
.6000
.4000
.2000
.4000
.8000
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.5000
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.0500
.7000
.0000
.0000
-------
A-32
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOSJT
PHOS_D
D ORTH P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB^PH
T ALK
CNDUCT
DO
CHJ.ORDE
SULFATE
CA
MG
NA
K
T_COUNT
W TFMP
TURBTY
CF1LOR A
PHPHT_ A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
21
21
21
21
21
21
21
21
21
19
21
21
0
21
21
16
21
21
16
16
16
16
3
15
14
14
14
14
14
14
14
14
14
14
14
0
14
14
15
14
14
0
0
0
0
6
22.4762
4 1712
10 8357
2.9476
0.0179
0.0042
0 0016
0. 1814
0 0274
0 3501
329 4286
8.5360
82 7800
233.95?4
7 9577
9 5286
18 8821
29.9375
8.0562
6.0437
1 1781
453 3333
BASIN~A WESTERN
7 0400
12 0182
1 .7214
0 8357
0.0326
0.0069
0.0037
0.4327
0.0379
0.2539
743 3571
8 0946
83.5900
244.6329
10 8640
10.7932
18.4921
10148. 3333
0.7389
1.2869
6.5627
2 8282
0.0093
0 0018
0.0012
0 1115
0.021 6
0. 1309
166 6759
0.2018
3 3920
10. 1006
0 3658
1.1975
1.4332
1.7308
0 2828
0.7780
0.1055
350 1904
CHDWtTV — n 17 A T T
bUKVbi-U rALL
0.9295
6. 1928
0.9305
0 5077
0 0102
0.0037
0.0027
0.1040
0.0442
0.0901
212.4685
0.0521
4.4463
20.1825
0.4975
2.7452
2.2947
11759.9599
[ LA*tK=B C.P ILIMINIUIN
0 1612
0. 2808
1.4321
0 6172
0 0020
0 0004
0.0003
0.0243
0 0047
0 0300
36 3717
0.0440
0 7402
2.2041
0 0914
0 2613
0.3127
0.4327
0 0707
0. 1945
0 0264
202 1825
T TVVL'D — E) fDTT TMMTHM
LAlfcK-n trlli 1MIN 1 UIN
0 2400
1 6551
0. 2487
0 1357
0.0027
0 0010
0 0007
0.0278
0.0118
0 0241
56 7846
0.0139
1 1883
5 3940
0.1285
0.7337
0 6133
4800.9835
21 .2000
1.9667
2. 1000
- 5 4000
0.0048
0.0019
0.0004
0.0320
0 0055
0.1700
76 0000
8.1100
78 0000
219 0000
7.3000
7 5000
16.9000
28.0000
7 5000
4.9000
0 9700
110.0000
5 7000
6 8100
0 7000
0 2000
0.0176
0.0021
0.0006
0.2910
0.0062
• o.iooo
390.0000
7 .9875
78.5000
224.5000
10. 1300
7.8000
16.0000
220.0000
23.7000
6.2400
23 5000
7.1750
0 0344
0 0086
0 0059
0.3340
0.0910
0.7050
571 0000
8.7500
90 0000
255.0000
8 6000
11 .5000
21 5000
34.0000
8.5000
7.3000
1.3500
810 0000
8.4000
23.2000
3.6750
1 .9000
0 0442
0.0147
0.0098
0 5960
0. 1500
0.4250
1126 0000
8 1700
92.8000
291 .5000
11.9000
16.9000
23.0000
27200 0000
-------
A-33
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS^D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
4
0
4
4
4
4
4
4
4
4
4
3
4
4
4
2
4
4
0
0
0
0
0
4
0
4
4
4
0
4
4
4
4
4
0
4
4
4
4
4
4
0
0
0
0
0
BflblH-B LtNlKAlj
2.0000
4.5700
2.5650
0.0429
0.0075
0.0055
0.2172
0.0057
0.1500
75.2500
8.1500
8.0675
97 0000
290.7500
12.8500
17.5000
25.4250
BASIN-B CENTRAL
0.0000
2.4750
0.0750
0.0095
0.0014
0.2212
0.0010
0.1475
36.0000
8.0025
96.6250
283 .7500
14.0200
13 .4000
23 .7000
&UKVC.I=A WiNltKl
0.0000
0.5811
0.7964
0.0027
0.0010
0.0036
0.0097
0.0057
0.0183
14. 1510
0.0100
0.0263
0.0000
0 9574
0.0707
0.0816
0.2217
CJTDWITV — 7\ UTMTC'DO
bUKVfci-A WINlhK/
0.0000
0.3979
0.2127
0.0006
0.0005
0.0078
0.0012
0.0126
13.8564
0.0330
0.2500
0.9574
0.4226
1.6753
0.1826
LA*tK=B tflLlPlNlUH
0.0000
0.2905
0.3982
0.0013
0.0005
0.0018
0.0049
0.0029
0.0091
7.0755
0.0058
0.0131
0.0000
0.4787
0.0500
0.0408
0.1109
2.0000
3.9500
1 .7300
0.0391
0.0064
0.0030
0.2080
0.0010
0. 1300
63.0000
8.1400
8.0300
97.0000
290.0000
12.8000
17 .4000
25.1000
2.0000
5.2300
3.6200
0.0452
0.0085
0.0109
0. 2310
0.0140
0.1700
88.0000
8. 1600
8.0900
97.0000
292.0000
12.9000
17 .6000
25.6000
T B V C1 D n ETDTTT MM T OM
Li/\IC*K— D t-rlli 1MN J.U1N
0.0000 0.0000
0.1989
0.1063
0.0003
0.0002
0.0039
0.0006
0.0063
6.9282
0.0165
0.1250
0.4787
0.2113
0.8377
0.0913
2.0000
-0.1600
0.0087
0.0010
0. 2110
0.0000
0.1300
24.0000
7 .9700
96.5000
283.0000
13.4500
11.9000
23.5000
0.0000
2.9300
0.3400
0.0102
0.0021
0.2300
0.0020
0.1600
48.0000
8.0400
97.0000
285.0000
14.4500
14.9000
23.9000
-------
VARIABLE
A-34
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT^A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T^COUNT
W TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
BftSlIN-B_LtINlKttL, t>UKVfiI-B_t>f K1HU1 LHIfcK-
13 6.6000 0.8803 0.
13
13
13
13
13
13
13
13
13
13
13
0
13
13
12
13
13
0
0
0
0
4
RTl C
D/\L
5
4
4
4
4
4
4
4
4
5
4
4
0
4
4
5
4
4
0
0
0
0
2
1.
2.
0.
0.
0.
0.
0.
0.
0,
12.
8.
93.
277 .
12,
14.
22.
7
5
1 ,
2
0
0
0
0
0
0
0
12
8
93
277
12
14
22
19
4615
5231
0231
0118
0037
0009
1977
0035
1154
0000
,3127
1023
.5292
,6883
,8423
,7000
5000
rMTD Zi T
LIN 1 KrtLi
.8200
.5375
.9250
.1500
.0150
.0037
.0019
.2205
.0027
.1000
.5000
.2000
.1250
.6250
.2600
.9000
.7250
.0000
0
1
0
0
0
0
0
0
0
7
0
1
3
0
0
0
1
CITDUC1 V — H
buK V t. I -D
0
0
2
0
0
0
0
0
0
0
12
0
0
4
1
0
0
16
.2163
.1656
.1472
.0019
.0007
.0002
.0270
.0021
.0431
.3144
.0676
.0352
.3598
.8867
7772
6312
.0000
•CD D TMH
of KlrJLi
6419
. 1795
7909
5686
.0068
.0009
.0008
.0177
.0005
.0524
. 2610
0716
.7500
.0492
.0825
.8124
.7274
.9706
0.
0.
0.
0.
0.
0.
0.
0.
0,
2.
0.
0.
0,
0.
0
0
0
1 T B VC*D — f
1 LA I tjK-l
0
0
i
0
0
0
0
0
0
0
6
0
0
2
0
0
0
12
- B _tf 1 L LF.
2442
0600
3233
0408
0005
0002
0001
0075
0006
0120
.0286
,0187
.2871
.9318
.2560
. 2156
.1751
IIN1UN ~-
5.
1.
1.
-0.
0
0.
0.
0.
0.
0.
4.
8.
91
274.
10.
14.
21.
.5000 7.
"• MPCOT TMMTOM
.. Mc,bUL 1MN 1UIN ~"
.2871 5
.0898 1
.3955
.2843
0034
.0005
.0004
.0089
.0002
.0235
.1305
.0358
.3750
0246
.4841
.4062
.3637
.0000
1
-0
0
0
0
0
0
0
4
8
92
274
10
14
22
7
5000
0700
3000
1000
0098
0030
0006
1420
0010
0300
0000
2000
0000
0000
3500
0000
7000
.0000
0000
.2700
.3000
.2000
.0098
.0028
.0010
.1980
.0020
.0400
.0000
.1000
.5000
.5000
.5000
.3000
.2000
.0000
8.
1.
4.
0.
0.
0.
0.
0.
0.
0.
34.
8.
94.
283.
13.
16.
23.
9
6
1
7
1
0
0
0
0
0
0
30
8
94
283
13
16
23
31
2000
8100
9000
3000
0159
0048
0013
2280
0070
1800
0000
4300
1300
0000
4000
3000
9750
.0000
.5000
.6500
. 1000
.0000
.0250
.0046
.0030
.2370
.0030
. 1800
.0000
.2700
.0000
.5000
.4500
. 1000
.8000
.0000
-------
VARIABLE
A-35
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS__D
D_ORTH_P
N02N03T
NH3NH4T
KJEL N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
6
5
5
5
5
5
5
5
5
6
5
5
0
5
5
6
5
5
0
0
0
0
2
6
6
6
6
6
6
6
6
6
6
6
6
0
6
6
6
6
6
0
0
0
0
3
BAbJ.N = B LENTKAL
4.1667
1.5460
1.3200
0.0600
0.0132
0.0030
0.0008
0.2300
0.0050
0.1350
9.6000
8. 1480
92.6000
276.8600
12.0317
14.6000
22.4600
13.5000
RA^TN-R PPMTRAT
DrtOilN — D V- Ci IN .1 I\rt ll
3.9667
2.4350
2.9633
0.3417
0.0170
0.0034
0.0012
0.2225
0.0073
0 1350
30.5000
8.0517
93.0333
278.2666
12.0300
14.9500
22.7667
13.6667
SUKVEY=B_SPRING1
0.3983
0.2360
0 1095
0.0548
0.0050
0.0007
0.0003
0.0306
0.0025
0.0459
3.5777
0.0650
0.5477
3 0246
1.0787
0.5050
0.4980
4.9497
QIIPWPV — R QDD IMP 1
oUKVC.1— 13 orr\.LlNUl
0.2733
0.7845
1 .4582
0.5907
0.0030
0.0007
0.0004
0.0239
0.0038
0.0302
13.9821
0.0902
0.9893
3.5092
0.6461
0.9006
0.7448
4.1633
LAYER=D_HYPOLIMNION
0.1626 3.8000
0.1055
0.0490
0.0245
0.0023
0.0003
0.0001
0.0137
0.0011
0.0188
1 .6000
0.0291
0 2449
1.3526
0.4404
0.2258
0.2227
3.5000
LAYER-E NEPHELOID
0.1116
0.3203
0 5953
0.2412
0.0012
0.0003
0.0002
0 0097
0.0015
0.0123
5.7082
0.0368
0.4039
1.4326
0.2638
0.3676
0.3040
2.4037
1 .2700
1 .2000
0.0000
0.0103
0.0021
0.0004
0. 1920
0.0030
0.0600
4.0000
8 0600
92.0000
274.5000
10 0400
14 3000
22.0000
10.0000
3.7000
1 6700
1 .7000
-0.1000
0 0137
0.0028
0.0008
0. 1940
0.0020
0.0900
12.0000
7.9000
92 4000
275.0000
11 . 1800
14.3000
22.0000
9.0000
4.8000
1.8300
1.5000
0 1000
0.0222
0.0037
0.0012
0.2580
0.0090
0 1800
12.0000
8.2300
93.0000
282 0000
13.0000
15 5000
23.3000
17.0000
4.4000
3.7500
5.1000
1.5000
0.0215
0.0047
0.0018
0 2580
0.0120
0.1800
51.0000
8.1500
95.0000
283.5000
12.9500
16.3000
23.8000
17.0000
-------
A-36
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR A
PHPHT_A
PHOSJT
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL^N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLOPDE
SULFATE
CA
MG
NA
K
T^COUNT
W TEMP
TURBTY
CHLOR_A
PHPHT A
PHOS T
PHOS_D
D_ORTH_P
NO2NO3T
NH3NH4T
KJEL N
DSICON
PH
LAB^PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
TJTOUNT
47
47
47
47
47
47
47
47
47
47
47
47
0
47
47
47
47
47
0
0
0
0
15
83
81
82
82
83
82
80
83
82
77
83
82
0
82
82
82
83
83
29
29
29
29
16
4
1
2
0
0
0
0
0
0
0
9
8
93
276
13
14
23
9
BASIN-B C
22
0
3
0.
0
0.
0.
0
0
0.
139.
8.
92.
275.
8.
14
22
34
8.
8.
1.
105.
.6317
8534
.8191
.0448
0130
.0038
0009
.2064
.0032
. 1436
0426
2107
3898
. 1619
.1923
.5931
5574
.1333
""FNTR A T
-. CIN 1 KM Li
. 1904
4167
1555
.9311
0088
.0037
.0011
1923
0140
2997
8072
5466
2365
4223
2819
6736
6758
9655
3598
6379
3254
8125
0
0
1
0
0
0
0
0
0
0
5.
0.
1
2
0
0.
1
4.
ciipi/c'v-r
o U K v c. I — L
0.
0
1
0
0.
0
0.
0
0
0
71
0
0.
2
0.
0
1 .
0.
0.
0.
0.
60.
3_bf KiNU^
.6268
.7818
. 3289
2917
.0023
.0006
.0003
.0191
0013
0684
.2542
. 1059
.2138
0980
3665
.2939
4176
0860
•> CTIMMITD
oUMritK
2423
0787
0818
4601
0037
0021
0016
0295
0097
0987
0183
2412
8930
8950
5624
4467
3417
7311
1310
2901
0232
0313
LftYtSK =
0
0
0
0
0
0
0
0
0
0
0
0
0
0.
0.
0
0.
1
T B VIT D — t
LA I t-K-t
0.
0
0
0
0
0
0
0
0
0.
7.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
15.
-B_tSfli,lMNiU
.0914
.1140
1938
.0425
.0003
.0001
.0000
0028
.0002
0100
7664
.0155
1771
.3060
.0535
.0429
.2068
0550
3 EPILIMNION
0266
0087
1 195
0508
0004
0002
0002
0032
0011
0112
7953
0266
0986
3197
0621
0490
1473
1358
0243
0539
0043
0078
N --
3
0
0
-0
0
0
0
0
0
0
4
7
91
270
12
14
20
5
21
0
1
0
0
0
-0
0
0
0
54
6
90
270
6
13
19
34
8
8
1
37
.6000
.9700
. 4000
.4000
.0098
.0025
.0002
. 1630
.0015
0400
.0000
.9300
.0000
0000
.3500
.0000
.5000
.0000
.7000
2800
. 3000
1000
0050
0007
.0002
1240
.0020
. 1700
.0000
.5900
.0000
.0000
.2000
.0000
.0000
.0000
. 1000
.2000
.2800
.0000
6
5
5
1
0
0
0
0
0
0
31
8
95
280
14.
15
29
21
22
0
7
2
0
0
0
0
0
0
451
8
94
284
9
15
26
36
8
9
1
210
.0000
.0400
.9000
.3000
.0227
.0054
.0016
.2430
.0080
.3800
.0000
.4050
.5000
.0000
.1500
2000
.6000
.0000
.9000
.6500
. 1000
.4000
.0279
.0170
.0126
.2480
0540
.8100
0000
.7600
0000
.0000
.4000
.4000
.0000
.0000
6000
.4000
.3700
.0000
-------
A-37
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS T
PHOS_D
D_ORTH^P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
28
28
28
28
28
26
27
28
28
25
28
28
0
28
28
28
28
28
1
1
1
1
0
27
27
27
27
26
26
24
26
27
25
26
27
0
27
27
26
27
27
26
26
26
26
7
• BAblN-B LKNTKAL
18.6964
0
3
1
0
0
0
0
0
0
601
8
93
279.
5
14.
22.
34.
8.
8.
1.
.7202
.5634
.1482
.0157
.0067
0038
.2080
.0309
.3137
.2143
.1106
.1836
.1696
.3031
.6091
.5670
0000
.4000
6000
3500
Rfl^TM — R PFWTRB.T
DrtolIN — D <, Ci IN i r\f\ Li
15.2667
1.7682
2.
1.
0.
0.
0.
0.
0.
0.
1572.
7.
96.
284.
1.
14.
22.
35.
8.
8.
1.
119.
6991
0213
0422
0215
0237
2031
0467
3446
0769
6166
4309
5926
3835
5250
4891
8462
4397
5077
3747
5714
bUKVt;Y-C_SUMMER
1 .3054
0
1
0
0
0
0
0
0
0
343
0
1
3
1.
0.
1 .
QITPUPV f"
oUKVC, I -L
1.
0.
2
0.
0.
0.
0
0.
0.
0.
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0.
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1.
0.
1.
0.
0.
0.
0.
44.
.3308
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.7182
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.0080
.0759
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0887
.2596
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.6731
.7614
.7810
.3742
. 1414
1 QIIMMPD
, oUPlPlfcK
4036
8609
8260
6738
0531
0316
0391
1181
0403
1325
4946
1511
5922
2211
2917
3616
4244
8806
1347
2314
0228
5865
LAYER=C_MESOLIMNION --
0.2467 15
0.
0.
0.
0.
0.
0
0
0.
0
64.
0.
0.
0.
0.
0.
0
T B VC"D n
LA I C.K-U
0.
0.
0
0.
0
0.
0.
0.
0.
0.
77.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
16
0625
3274
1357
0027
0017
0015
0143
0052
0177
8700
0562
3162
7108
3366
0707
2157
0
1
-0
0
0
-0
0
0.
0.
67.
7.
89 .
271.
2
13.
20.
34.
8.
8.
1.
.0000
.3100
.2000
.3000
.0059
.0007
.0001
.0860
.0040
.2000
.0000
.6500
5000
5000
0500
7000
3000
0000
4000
6000
3500
21
1
8
2
0
0
0
0
0
0
1312
8
96.
284.
8.
15.
24.
34.
8.
8.
1.
0000
5300
.7000
9000
0746
.0419
.0396
.4645
1080
.5500
.0000
.6500
.3800
.0000
.3000
.4000
.4500
.0000
.4000
.6000
.3500
HYPOLIMNION --
2701 13.
1657 0
5439
1297
0104
0062
0080
0232
0078
0265
5629
0291
4989
4275
2533
0696
2741
1727
0264
0454
0045
8521
0.
-0.
0.
0.
0.
0.
0.
0.
836.
7.
93.
279.
0.
13.
20.
34.
8.
7.
1 .
61 .
3000
7000
1000
6000
0103
0022
0004
0050
0040
2000
0000
4300
0000
2500
2500
9000
3000
0000
2000
9000
3000
0000
19.
4.
12
2.
0
0.
0.
0.
0.
0.
2400.
8.
102.
288.
6.
15.
24.
37.
8.
8.
1 .
180.
.7000
2500
6000
.6000
2552
1544
1735
4500
1430
7300
0000
0600
0000
0000
0000
2000
7000
0000
.7000
.9000
.4100
.0000
-------
A-38
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W^ TEMP
TURBTY
CHLOR^A
PHOS_T
PHOS__D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB^PH
T ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
W TFMP
TURBTY
CHLOrt A
PHPHT_A
PHOS _T
PHOS D
D_ORTH_P
N02N03T
NH3NH4T
KJEL N
DSICON
PH
LAB PH
T ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
TJTOUNT
DftiD 11N -D
1 14
1 1
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 0
1 1360
1 7
0
1 100
1 290
1 0
1 14
1 23
1 37
1 8
1 8
1 1
0
D A c T W R
D t\ o 1 IN — D
67 10
67 2
68
68
68
68
68
68
68
68
68
68
0
68
68
68
68
68
0
0
0
0
30
2
0
0
0
0
0
0
0
78
8
92
278
9
14
23
91
u cn i i\i\Li
. 1000
5800
5000
5000
0551
0330
0295
0970
1070
3200
0000
5300
0000
0000
2500
6000
7000
0000
4000
.5000
3800
r* F M T D fl r
L. r, IN 1 K R L
5910
3744
6200
5656
0214
.0099
.0049
1282
.0179
.2302
8235
1906
. 1075
5129
.9279
6560
0912
.7000
oui\ v c, i -
C IIDWP1 V —
bu Kv fc I -
0
0
0.
0
0
0
0
0
0.
0
34
0
2.
4
0.
0.
1.
43.
u_DurinCjtt ijrtin«-n, HurnnijUiu
14
1 .
0
0
0
0
0.
0
0.
0.
1360.
7
100
290.
0
14
23.
37
8
8.
1
D FALL L A Y E R - B
4673 0
5581 0
8316
2858
0039
0022
0019
0222
0089
1044
3524
0339
8604
3941
6191
5576
0813
4235
0
0
0
0
0
0
0
0
4
0
0
0
0
0
0
7
1000
5800
5000
5000
0551
0330
0295
0970
1070
3200
0000
5300
0000
0000
2500
6000
7000
0000
4000
5000
3800
14
1
0
0
0.
0
0
0.
0
0
1360.
7.
100
290.
0.
14.
23
37
8
8
1
1000
5800
5000
5000
0551
0330
0295
0970
1070
3200
0000
5300
0000
0000
2500
6000
7000
0000
4000
5000
3800
EP I LIMN ION
05;i 9
0682 1
1008
0347
0005
0003
.0002
0027
0011
.0127
. 1658
0041
.3469
.5329
.0751
.0676
1311
.9280
!
-0
0.
0
0
0
0
0
22
8
71 .
270
9
13
20
26
7000
3400
2000
5000
0121
0045
0014
0800
0060
0300
0000
0900
.3300
.0000
.1000
5000
.9000
.0000
11
4
4
1
0
0.
0
0.
0
0
139.
8
95
285
11
15
25
180
4000
0600
9000
2000
0281
0133
01J 6
. 1780
0370
5500
.0000
2700
0000
.0000
.6000
.5000
.5000
.0000
-------
VARIABLE
A-39
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHTJV
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
1
0
3
3
3
3
3
3
3
3
3
2
3
3
3
1
3
3
0
0
0
0
0
4
0
4
4
4
0
4
4
4
4
4
3
4
4
4
4
4
4
0
0
0
0
0
3
1
0
0
0
0
0
0
0
62
8
8
99
290
13
16
25
RTAQTM — r
D t\ o i I "1 — • L.
0
i
0
0
0
0
0
0
67
7
7
98
289
13
15
23
tnt>IC.KIN bUI
.5000
.9200
.4733
0164
.0084
.0036
.2627
.0060
.1567
.3333
.1900
.0967
.5000
.0000
.3000
.5333
.8000
P" fl CTPPW QIIC
tHo 1 C.K1N t»Ur
.0000
.0625
.1225
.0116
.0026
.2745
.0005
.1275
.7500
.9733
.9575
.2500
.0000
.4125
.2000
.8250
0.
0.
0.
0.
0.
0
0.
0.
3.
0.
0.
0.
0.
0.
0.
?WC* V — 7A
CVCi I —f\
0.
0.
0.
0.
0.
0.
0.
0.
3.
0.
0.
0.
1.
0.
0.
0.
_WiNiliKl
1212
1531
0067
0003
0011
0067
0036
0351
0551
0283
0577
5000
0000
0577
1000
UT MTC*D O
WIN 1 tKZ
0000
3181
2645
0010
0004
0066
0006
0250
7749
0252
0263
6455
1547
2529
1155
3304
0.
0.
0.
0.
0.
0.
0.
0.
1.
0.
0.
0.
0.
0.
0.
T B VC"D —
LA I EiK-
0.
0.
0.
0.
0.
0.
0.
0.
1.
0.
0.
0.
0.
0.
0.
0.
b_bf 1L^
0700
0884
0039
0002
0007
0038
0021
0203
7638
0200
0333
2887
0000
0333
0577
1N1ON --
3
1
0
0
0
0.
0.
0.
0.
59.
8.
8.
99.
290.
13.
16.
25.
.5000
.8100
.3800
.0124
.0081
.0028
.2570
.0020
.1200
.0000
. 1700
.0300
.0000
.0000
,3000
.5000
.7000
3.
2.
0.
0.
0.
0.
0.
0.
0.
65.
8.
8.
100.
290.
13.
16.
25.
5000
0500
6500
0241
0086
0049
2700
0090
1900
0000
2100
1300
0000
0000
3000
6000
9000
BC'DTT T MM TOM
Ci IT 1 L 1 MN i UN — *
0000 0.
1590
1322
0005
0002
0033
0003
0125
8875
0145
0131
3227
5774
1265
0577
1652
0.
-0.
0.
0.
0.
0
0.
65
7
7
97
288
13
15
23
.0000
7000
.1300
.0106
.0021
.2680
.0000
.0900
.0000
.9500
.9200
.5000
.0000
.1000
.1000
.4000
0.
1 .
0.
0.
0.
0.
0.
0.
73.
8.
7
99
290
13
15
24
0000
4100
.4800
,0128
.0030
.2830
.0010
, 1400
.0000
.0000
,9800
.0000
.0000
.7000
.3000
.2000
-------
VARIABLE
A-40
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
N MEAN STD DEV STD ERROR MINIMUM
MAXIMUM
W TEMP
TURBTY
CHLOR_A
PHPHT A
PHOS T
PHOS_D
D ORTH P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB^PH
T ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W TEMP
TURBTY
CHLOR A
PHPHT _A
PHOS_T
PHOS D
D ORTH P
N02N03T
NH3NH4T
KJEL N
DSICON
PH
LAB PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T^COUNT
40
40
40
40
40
40
40
40
40
40
40
40
0
40
40
39
40
40
0
0
0
0
13
24
24
24
24
24
23
24
24
24
24
24
24
0
24
24
21
24
24
8
8
8
8
7
BH»11N = U_I
2
2
0
0
0
0
0
0
0
0
71
7
92
278
12
14
23
62
BASIN=C E
21
0.
]
0
0
0
0
0
0.
0
75.
8
92
280
8.
15
23
35
8
8
1 .
173
-Hb i C.K1N
1275
.6334
3966
0674
0128
0062
0027
2876
0068
1217
.5000
9254
3775
2187
.9238
9356
2012
8462
? TV C •P p p M
.../A o L r, rtlN
8042
4790
3906
6135
0057
0023
0011
1852
0066
2786
4583
5528
5156
2292
8845
01 35
0458
5000
3500
9000
3500
8571
bUKVt,Y=l
0
0
0
0
0
0
0
0
0
0
10
0
1
2
0
0
0
41.
PHRVpv f
oU K v c, i - L
0
0
0
0
0.
0.
0.
0
0.
0
28.
0.
0
1 .
0.
0
0
0
0
0.
0
124
1 bFKIN
.3803
.8276
.2347
0555
0013
.0006
.0007
.0198
0019
.0918
9755
.0688
4633
.0266
5577
2395
5374
6010
i QMMMP
oUMMt
3581
4879
4322
1822
0013
0011
0008
0214
0033
1190
7251
1440
7521
1299
4531
3555
8933
5345
1512
1512
0214
5611
U<; LAYKK
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
11
R LAYER
0
0
0
0
0
0
0
0
0
0
5
0
0
0
0
0
0
0
0
0
0
47
=0 tPlLlMNIO
.0601
1309
0371
0088
.0002
.0001
.0001
0031
0003
.0145
7354
0109
2314
.3204
0893
0379
.0850
.5380
B EPILIMNION
0731
0996
0382
0372
.0003
0002
0002
0044
0007
0243
.8635
0294
. 1535
.2306
.0989
.0726
1823
1890
.0535
.0535
0076
.0797
N --
1
1
0
-0
0
0
0
0
0
0
54
7
90
274
10
14
21
14
21
0
0.
0
0
0
0.
0
0
0
39.
8.
91 .
277
7
14
21 .
35
8.
8
1 .
66
7000
.7200
2000
1000
.0109
.0047
0016
2430
.0040
0300
0000
7000
0000
0000
. 1500
5000
9000
0000
.2000
2800
,7000
4000
0037
0008
,0003
1630
0020
1 100
0000
,0700
0000
0000
7000
4000
5000
0000
0000
6000
3300
0000
3
5
1
0
0
0
0
0
0
0
88
8
95
282
13
15
24.
140
22
2
2.
]
0
0
0
0.
0.
0
135
8.
94.
282.
9.
15.
24 .
36
8.
9
1
390.
.1000
. 1500
.0000
2000
0164
0078
0043
.3220
.0110
6200
0000
0400
0000
.0000
. 4000
4000
.4000
,0000
5000
7400
4000
0750
0085
0046
0041
. 2510
,0110
6600
,0000
,6700
.0000
,0000
,8000
,6000
,1000
0000
,5000
1000
4000
0000
-------
A-41
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOSJT
PHOS_D
D_ORTH_P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
8
8
8
8
8
8
8
8
8
8
8
8
0
8
8
7
8
8
0
0
0
0
0
10
10
10
10
10
10
10
10
10
10
10
10
0
10
10
9
10
10
0
0
0
0
1
Bftt>lIN-L_e
13.
0.
1.
0.
0.
0
0.
0.
0.
0
145.
7.
93.
284.
7.
14
22.
^RSltKN
8375
6108
2250
6000
0053
0021
0014
3007
0082
1697
5000
9596
4162
8750
9262
9100
6912
D TV o T M — r1 C1 B C T F D M
D/\b IN— L- c.Hb 1 hKri
5 8400
1.5940
0.
0.
0.
0.
0
0
0
0
303
7
94
286
10
14
23
140
.3700
.4700
.0071
.0025
.0025
.3461
.0112
.2140
.3000
.9060
.1500
.6000
.1000
8100
.2900
.0000
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
93.
0.
0.
1 .
0.
0.
0.
CUD WI7 V — f
bUKvEi I —I.
i .
0.
0.
0.
0.
0.
0
0
0
0
83
0
0
1
1
0
1
; bUMMfcK
8782
2100
6431
2928
0011
0014
0007
0270
0108
0880
0023
1052
6962
6421
8497
3065
9086
0.
0.
0.
0
0.
0.
0.
0.
0.
0.
32.
0.
0.
0.
0.
0.
0.
. MfcbULlMNiUN --
3105 12.
0742
2274
1035
0004
0005
0002
0096
0038
0311
8813
0372
2461
5806
3212
1084
3212
0.
0.
0.
0.
0.
0.
0.
0.
0.
60.
7.
92.
282.
6.
14.
21.
5000
4000
5000
3000
0032
0007
0006
2570
0010
0000
0000
8300
8300
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5000
15.
1 .
2.
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0
0
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95.
287.
9
15
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0000
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3390
0340
3100
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1000
0000
0000
4000
4000
6000
0977
3976
.2406
. 1947
.0024
.0008
.0009
.0349
.0077
.1258
.0529
.0635
.7472
.4298
3219
2558
.1761
IJ/AI Cji\ u n i c uijj. mi xun
0.3471 4.
0.1257 1.
0.
0.
0.
0.
0
0
0
0
26
0
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0
0
0
0
.0761
.0616
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.0003
.0003
.0110
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.0398
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.0201
.2363
.4522
.4406
.0809
.3719
0.
0
0,
0
0.
0
0
0
133
7
93
285
7
14
21
140
.7000
.0400
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. 2000
.0031
.0014
.0015
.2820
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1200
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8.
2
0
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.0000
.0000
.6000
.4000
.3000
.0000
-------
A-42
L. ERIE DESCRIPTIVE STATISTICS, BY BASIN, SURVEY AND LAYER
VARIABLE
MEAN
STD DEV
STD ERROR
MINIMUM
MAXIMUM
W_TEMP
TURBTY
CHLOR^A
PHPHT_A
PHOS^T
PHOS_D
D_ORTH._P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T_ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T COUNT
W_TEMP
TURBTY
CHLOR_A
PHPHT_A
PHOS_T
PHOS^D
D_ORTH P
N02N03T
NH3NH4T
KJEL_N
DSICON
PH
LAB_PH
T ALK
CNDUCT
DO
CHLORDE
SULFATE
CA
MG
NA
K
T_COUNT
16
16
16
16
16
15
15
16
16
16
16
16
0
16
16
14
16
16
8
8
8
8
4
34
33
33
33
33
33
33
33
33
33
33
33
0
33
33
33
33
33
0
0
0
0
13
5
1
0
0
0
0
0
0
0
0
340
7
94
287
9
14
22
36
8
8
1
337
n TV Q T k] _ p
D A 0 I N - L
10
4
0
0
0
0
0
0
0
0
90
8
94
283
9
14
23
89
_tnt>ic,K
.6875
.9213
3016
.4859
0075
.0034
.0028
.3492
.0145
.2403
5625
.9062
6328
0469
.6682
.8672
.8878
8750
3000
.8175
3825
5000
p- i\ c'T'pp
4265
1016
8227
.3485
.0153
.0066
.0031
.2045
0115
1788
.4242
1045
. 1542
5424
.3556
.6100
.2233
1538
n &UKVC.I
0
0
0
0
0
0
0
0
0
58
0
0
1
1
0
1
0
0
0
0
263
M CIlDt/CV
N bUK V 1. 1
0
3
0
0
0
0
0
0
0
0
41
0
0
0
0
0
0
62
-insurant
. 2049
. 3273
1233
1906
.0026
.0021
.0006
.0278
.0089
. 1198
.7469
0650
8702
3173
2907
. 2919
1665
8345
1414
0991
0167
4862
-D FALL
1880
8393
.3423
.1522
.0071
.0008
.0004
.0193
0067
.0514
.4307
0227
.7001
.7947
.2891
3386
.5314
. 1434
0
0
0
0
0.
0
0.
0
0.
0.
14.
0.
0.
0.
0
0.
0
0.
0
0.
0.
131 .
LAYER- B
0.
0
0.
0.
0.
0.
0
0.
0.
0.
7 .
0.
0.
0.
0.
0.
0.
17
t, NfcfHtLUiL
3012
0818
0308
0477
0006
0006
0002
0070
0022
0299
6867
0163
2175
3293
3450
0730
2916
2950
0500
0350
0059
7431
EPILIMNION
0322
6683
0596
0265
0012
0001
0001
0034
0012
0089
2127
0039
1219
1383
0503
0589
0925
2355
4.
1.
0
0.
0.
0.
0.
0.
0.
0
261
7.
92
285.
7 .
14,
21.
36,
8
8
1
180
10
0
0
0
0
0
0
0
0
0
-11
8
93
281
8
14
22
26
7000
4600
1500
1000
.0071
.0011
.0019
.3105
.0040
0900
0000
.7900
7500
.0000
.4250
.6000
.0500
.0000
0000
7000
.3600
0000
0000
.9900
3000
.1000
.0094
.0056
.0020
.1710
.0017
.0700
.0000
0500
0000
5000
.4500
.2000
.3800
.0000
8.
2.
0
0
0
0
0
0
0
0.
438.
8.
96.
289
11 .
15
25.
38
8.
9
1
730
10.
18
1 .
0.
0.
0.
0
0
0
0
141
8
95
284
10
15
24
210
3000
4200
5000
9000
0113
0082
0038
4060
0260
5800
0000
0200
0000
0000
6000
4000
0000
0000
5000
0000
4100
0000
6000
3000
.7000
.8000
.0429
.0080
0039
2440
.0280
.3100
0000
. 1600
.5000
.7000
.1000
.3000
. 2000
.0000
-------
B-l
APPENDIX B
MICROFICHE LISTINGS OF 1985 SURVEILLANCE DATA
The microfiche appended to this report (see pocket on inside of back
cover) contains a listing of the entire 1985 GLNPO STORET Great Lakes
surveillance database. The database is organized chronologically, by
station, that is, all samples collected at station Lake Erie 09, for
example, are followed by all samples collected at Station L. Erie 11, etc.
The letter "V" following sample depth indicates composited samples, the
letter "T" following a parameter values indicates that the measured
concentration is below the criterion of detection for that parameter.
------- |