Abstract ........................................................ 1
Introduction .................................................... 2
Purpose and Scope ............................................ 6
Approach ..................................................... 9
Methods of Data Collection and Analysis ......................... 9
Field Methods ................................................ 9
Discharge, Water Chemistry, and Suspended Chlorophyll a
Concentrations ............................................ 9
Macroinvertebrates ....................................... 11
Fish ..................................................... 11
Data Summaries .............................................. 11
Watershed Boundaries and Environmental Characteristics ...... 12
Statistical Methods ......................................... 12
Normalization ............................................ 14
Correlations and Regressions ............................. 14
Simultaneous Partial Residualization ..................... 14
Regression-Tree Analysis to Define Thresholds or
Breakpoints .............................................. 15
Redundancy Analysis ...................................... 15
Statistical Differences among Groups ..................... 17
Graphical Techniques ........................................ 17
Water Quality and Its Relations with Environmental
Characteristics in the Watershed ............................... 18
Relations between Water Quality and Environmental
Characteristics in the Watershed ............................ 19
Correlations between Individual Characteristics .......... 19
Effects of Multiple Environmental Characteristics on
Water Quality ............................................ 25
Stepwise Regression ................................... 25
Redundancy Analysis ................................... 30
Environmental Characteristics Most Strongly Related to
Water Quality ............................................ 33
Thresholds in Water-Quality Responses and Responses to
Changes in Land Use ......................................... 33
Reference Water Quality ..................................... 35
Macroinvertebrate Assemblages and Their Relations with Water-
Quality and Environmental Characteristics ...................... 39
Relations with Individual Characteristics ................... 42
Correlations ............................................. 42
Response to Changes in Nutrient Concentrations ........... 42
Effects of Multiple Characteristics on Macroinvertebrate
Indices ..................................................... 47
Stepwise Regressions ..................................... 47
Redundancy Analysis ...................................... 47
Reference Values forthe Macroinvertebrate Indices ........... 49
Fish Assemblages and Their Relations with Water-Quality and
Environmental Characteristics ............................... 53
Relations with Individual Characteristics ................... 53
Correlations ............................................. 53
Responses to Changes in Nutrient Concentrations .......... 57
Effects of Multiple Characteristics on Fish Indices ......... 57
Stepwise Regressions ..................................... 57
Redundancy Analysis ...................................... 61
Reference Values for the Fish Indices ....................... 61
Multiparameter Biotic Indices to Estimate Nutrient
Concentrations in Nonwadeable Rivers ........................... 61
Summary of Results for Nonwadeable Rivers and Wadeable
Streams ........................................................ 65
Water Quality ............................................... 67
Response in the Biotic Communities .......................... 68
Conclusions .................................................... 72
Literature Cited ............................................... 72
Appendixes ..................................................... 76
Figures
1. Maps showing two regionalization schemes considered for
streams and rivers in Wisconsin: A, level III ecoregions
with major land-use/land-cover categories and B,
environmental phosphorus zones ............................. 4
2. Map showing sites on nonwadeable rivers in Wisconsin
included in this study. Water-quality and biological data
for each site are given by site-identification number in
the appendixes ............................................ 10
3. Graphs showing definition of water-quality thresholds in
responses of biotic indices to changes in water quality:
A, biotic indicator with an abrupt threshold and B,
biotic indicator with a broad threshold ................... 16
4-6. Maps showing:
4. Distributions for median monthly total phosphorus and
dissolved phosphorus concentrations for the studied
nonwadeable rivers in Wisconsin, 2003 ..................... 19
5. Distributions for median monthly total nitrogen total
Keldahl nitrogen, dissolved nitrite plus nitrate
nitrogen, and dissolved ammonia nitrogen for the studied
nonwadeable rivers in Wisconsin, 2003 ..................... 23
6. Distributions for median monthly suspended chlorophyll a
and Secchi-tube depth for the studied nonwadeable rivers
in Wisconsin, 2003 ........................................ 24
7-11.Graphs showing:
7. Percentages of variance in water quality described by
land-use, basin, soil/surficial-deposit characteristics,
interactions among categories, and unexplained variance
for the studied nonwadeable rivers in Wisconsin ........... 31
8. Percentages of variance in A, suspended chlorophyll
a concentrations and B, Secchi-tube depths described by
nutrients, environmental characteristics, interactions
among categories, and unexplained variance for the
studied nonwadeable rivers in Wisconsin ................... 32
9. Logarithmically transformed total phosphorus and total
nitrogen concentrations as a function of the percentage
of total agriculture in the watersheds of the studied
nonwadeable rivers in Wisconsin, 2003 ..................... 34
10. Logarithmically transformed suspended chlorophyll a
concentrations and Secchi-tube depths as a function of
logarithmically transformed median total phosphorus and
total nitrogen concentrations for the studied
nonwadeable rivers in Wisconsin, 2003 ..................... 36
11. Suspended chlorophyll a concentrations and Secchi-tube
depths in Reference sites and High sites in the studied
nonwadeable rivers in Wisconsin, 2003 ..................... 38
12. Maps showing distributions for four macroinvertebrate
indices for the studied nonwadeable rivers in Wisconsin ... 41
13-17.Graphs showing:
13. Species richness, mean pollution tolerance value,
percentage of individuals from the order Ephemeroptera,
and Hilsenhoff Biotic Index values as a function of
total phosphorus and total nitrogen concentration for
the studied nonwadeable rivers in Wisconsin ............... 45
14. Species richness and mean pollution tolerance value as
a function of dissolved phosphorus, dissolved nitrite
plus nitrate nitrogen, dissolved ammonia nitrogen, and
total Kjeldahl nitrogen concentrations for the studied
nonwadeable rivers in Wisconsin ........................... 46
15. Redundancy analysis results for macroinvertebrate
indices and nutrients, other water-quality, and
environmental characteristics: axis 2 scores are plotted
as a function of axis 1 scores ............................ 50
16. Percentages of variance in 14 macroinvertebrate-index
values described by nutrients, other water-quality
characteristics, environmental characteristics,
interactions, and unexplained variance for the studied
nonwadeable rivers in Wisconsin ........................... 50
17. Species richness, mean pollution tolerance value,
percentage of individuals from the order Ephemeroptera,
and Hilsenhoff Biotic Index values in Reference sites
and High sites in the studied nonwadeable rivers in
Wisconsin ................................................. 52
18. Maps showing distributions for four fish indices for
the studied nonwadeable rivers in Wisconsin ............... 54
19-24.Graphs showing:
19. Wisconsin large-river index of biotic integrity,
percentage of suckers by weight, number of intolerant
fish species, and percentage of individuals that are
riverine species as a function of total phosphorus and
total nitrogen concentration for the studied nonwadeable
rivers in Wisconsin ....................................... 58
20. Wisconsin large-river index of biotic integrity and
percentage of suckers by weight as a function of
dissolved phosphorus, dissolved nitrite plus nitrate
nitrogen, dissolved ammonia nitrogen, and total Kjeldahl
nitrogen concentrations for the studied nonwadeable
rivers in Wisconsin ....................................... 59
21. Redundancy analysis results for fish indices and
nutrients, other water-quality, and environmental
characteristics: axis 2 scores are plotted as a function
of axis 1 scores .......................................... 62
22. Percentages of variance in 11 fish-index values
described by nutrients, other water-quality
characteristics, environmental characteristics,
interactions, and unexplained variance for the studied
nonwadeable rivers in Wisconsin ........................... 62
23. Wisconsin large-river index of biotic integrity,
percentage of suckers by weight, number of intolerant
fish species, and percentage of individuals that are
riverine species in Reference sites and High sites in
the studied nonwadeable rivers in Wisconsin ............... 64
24. Measured and estimated A, total phosphorus and B, total
nitrogen concentrations for the three-parameter
regression models; C, measured phosphorus concentrations
as a function of Biotic Index of total Phosphorus
values; and D, measured nitrogen concentrations as
a function Biotic Index of total Nitrogen values, with
regression equations and coefficients of determination
for the studied nonwadeable rivers in Wisconsin ........... 66
Tables
1. Reference concentrations for total phosphorus, total
nitrogen, and suspended chlorophyll a concentrations, and
turbidity in various ecoregions, Zones from the Upper
Midwest study, and wadeable streams study ................... 7
2. Summary statistics for median monthly water quality
collected in 2003 and environmental characteristics of
the watersheds of the study sites in nonwadeable rivers
in Wisconsin ............................................... 13
3. Median and average monthly concentrations for total,
dissolved, and particulate phosphorus, suspended
chlorophyll a, total nitrogen, nitrite plus nitrate,
ammonia, Kjeldahl nitrogen, and Secchi-tube depth in the
studied nonwadeable rivers in Wisconsin, 2003 .............. 20
4. Spearman correlation coefficients between median total,
dissolved, and particulate phosphorus, total nitrogen,
nitrite plus nitrate, ammonia, and total Kjeldahl
nitrogen concentrations, median Secchi-tube depths,
chlorophyll a concentrations, percentages of urban and
agricultural areas, and specific environmental
characteristics for the studied nonwadeable rivers in
Wisconsin .................................................. 21
5. Spearman correlation coefficients between residualized
logarithmically transformed median total, dissolved, and
particulate phosphorus, nitrogen, nitrite plus nitrate,
total Kjeldahl nitrogen, ammonia, and chlorophyll
a concentrations, median Secchi-tube depths, and specific
residualized environmental characteristics for the
studied nonwadeable rivers in Wisconsin .................... 26
6. Results from forward stepwise-regression analyses to
explain variability in raw and residualized water-quality
concentrations in the studied nonwadeable rivers in
Wisconsin .................................................. 28
7. Results from redundancy analysis between water-quality
and environmental characteristics for the studied
nonwadeable rivers in Wisconsin ............................ 31
8. Thresholds or breakpoints in the response in water
quality to changes in the percentage of agricultural area
in the basin for nonwadeable rivers in Wisconsin ........... 35
9. Reference conditions for water-quality constituents for
nonwadeable rivers in Wisconsin ............................ 37
10. Summary statistics for biotic indices for nonwadeable
rivers in Wisconsin ........................................ 40
11. Spearman rank correlation coefficients between
macroinvertebrate-assemblage indices and median water-
quality, land-use, basin, and soil/surficial-deposit
characteristics for the studied nonwadeable rivers
in Wisconsin ............................................... 43
12. Thresholds or breakpoints in the responses in
macroinvertebrate indices to changes in nutrient
concentrations for nonwadeable rivers in Wisconsin ......... 48
13. Results from forward stepwise-regression analyses to
explain variance in macroinvertebrate indices for the
studied nonwadeable rivers in Wisconsin .................... 48
14. Reference conditions for six macroinvertebrate indices
for nonwadeable rivers in Wisconsin ........................ 51
15. Spearman rank correlation coefficients between fish-
community indices and median water-quality, land-use,
basin, and soil/surficial-deposit characteristics for the
studied nonwadeable rivers in Wisconsin .................... 55
16. Thresholds or breakpoints in the responses of fish
indices to changes in nutrient concentrations for
nonwadeable rivers in Wisconsin ............................ 60
17. Results from forward stepwise-regression analyses to
explain variance in fish indices for the studied
nonwadeable rivers in Wisconsin ............................ 60
18. Reference conditions for six fish indices for nonwadeable
rivers in Wisconsin ........................................ 63
19. Results from forward stepwise-regression models to
explain variances in total phosphorus and total nitrogen
concentrations with biotic indices for the studied
nonwadeable rivers in Wisconsin ............................ 65
20. Reference conditions for water-quality constituents and
biotic indices for nonwadeable rivers in Wisconsin ......... 69
21. Summary of thresholds or breakpoints in the responses of
water quality and biotic indices to changes in nutrient
concentrations for nonwadeable rivers in Wisconsin ......... 71
Appendixes
1. Stream identification, location information, and summary
statistics for flow and water-quality data collected in
2003 for each of the 42 studied nonwadeable rivers in
Wisconsin .................................................. 76
2. Macroinvertebrate indices for each of the 41 studied
nonwadeable rivers in Wisconsin ............................ 78
3. Fish indices and ratings for each of the 41 studied
nonwadeable rivers in Wisconsin ............................ 80
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