WATER-QUALITY ASSESSMENT OF THE UPPER ILLINOIS 

RIVER BASIN IN ILLINOIS, INDIANA, AND WISCONSIN: 

NUTRIENTS, DISSOLVED OXYGEN, AND FECAL-INDICATOR 

BACTERIA IN SURFACE WATER, APRIL 1987 THROUGH 

AUGUST 1990

by Paul J. Terrio

Delmarva 

Peninsula

U.S. GEOLOGICAL SURVEY 

Water-Resources Investigations Report 95-4005

1995
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

For additional information Copies of this report can be

write to: purchased from:

District Chief U.S. Geological Survey-ESIC

U.S. Geological Survey Open-File Reports Section

102 E. Main St., 4th Floor Box 25286, MS 517

Urbana, IL 61801 Denver Federal Center

	Denver, CO 80225-0046
FOREWORD

The mission of the U.S. Geological Survey 

(USGS) is to assess the quantity and quality of the 

earth resources of the Nation and to provide information that will assist resource managers and policymakers at Federal, State, and local levels in making sound 

decisions. Assessment of water-quality conditions and 

trends is an important part of this overall mission.

One of the greatest challenges faced by waterresources scientists is acquiring reliable information 

that will guide the use and protection of the Nation's 

water resources. That challenge is being addressed by 

Federal, State, interstate, and local water-resource 

agencies and by many academic institutions. These 

organizations are collecting water-quality data for a 

host of purposes that include: compliance with permits 

and water-supply standards; development of remediation plans for a specific contamination problem; operational decisions on industrial, wastewater, or watersupply facilities; and research on factors that affect 

water quality. An additional need for water-quality 

information is to provide a basis on which regional 

and national-level policy decisions can be based. Wise 

decisions must be based on sound information. As a 

society we need to know whether certain types of 

water-quality problems are isolated or ubiquitous, 

whether there are significant differences in conditions 

among regions, whether the conditions are changing 

over time, and why these conditions change from 

place to place and over time. The information can be 

used to help determine the efficacy of existing waterquality policies and to help analysts determine the 

need for and likely consequences of new policies.

To address these needs, the Congress appropriated funds in 1986 for the USGS to begin a pilot program in seven project areas to develop and refine the 

National Water-Quality Assessment (NAWQA) Program. In 1991, the USGS began full implementation 

of the program. The NAWQA Program builds upon an 

existing base of water-quality studies of the USGS, as 

well as those of other Federal, State, and local 

agencies. The objectives of the NAWQA Program are 

to:

 Describe current water-quality conditions for a

large part of the Nation's freshwater streams,

rivers, and aquifers.

 Describe how water quality is changing over 

time.

 Improve understanding of the primary natural 

and human factors that affect water-quality 

conditions.

This information will help support the development 

and evaluation of management, regulatory, and monitoring decisions by other Federal, State, and local 

agencies to protect, use, and enhance water resources.

The goals of the NAWQA Program are being 

achieved through ongoing and proposed investigations 

of 60 of the Nation's most important river basins and 

aquifer systems, which are referred to as study units. 

These study units are distributed throughout the 

Nation and cover a diversity of hydrogeologic settings. More than two-thirds of the Nation's freshwater 

use occurs within the 60 study units and more than 

two-thirds of the people served by public water-supply 

systems live within their boundaries.

National synthesis of data analysis, based on 

aggregation of comparable information obtained from 

the study units, is a major component of the program. 

This effort focuses on selected water-quality topics 

using nationally consistent information. Comparative 

studies will explain differences and similarities in 

observed water-quality conditions among study areas 

and will identify changes and trends and their causes. 

The first topics addressed by the national synthesis are 

pesticides, nutrients, volatile organic compounds, and 

aquatic biology. Discussions on these and other waterquality topics will be published in periodic summaries 

of the quality of the Nation's ground and surface water 

as the information becomes available.

This report is an element of the comprehensive 

body of information developed as part of the NAWQA 

Program. The program depends heavily on the advice, 

cooperation, and information from many Federal, 

State, interstate, Tribal, and local agencies and the 

public. The assistance and suggestions of all are 

greatly appreciated.

Robert M. Hirsch 

Chief Hydrologist

Foreword III

CONTENTS

Abstract......................................................................................... 1

Introduction...................................................................................... 2

Purpose and Scope............................................................................ 2

Description of the Upper Illinois River Basin....................................................... 3

Data Collection and Sources......................................................................... 6

Fixed-Station Sampling........................................................................ 6

Synoptic Sampling ........................................................................... 10

Data Compiled From Other Sources.............................................................. 15

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria ................................................ 16

Nutrients ................................................................................... 16

Sources of Nutrients in the Upper Illinois River Basin .......................................... 18

Data Analysis........................................................................... 21

Nutrient Conditions in the Upper Illinois River Basin ........................................... 49

Dissolved Oxygen............................................................................ 61

Fecal-Indicator Bacteria ....................................................................... 67

Summary........................................................................................ 74

References Cited.................................................................................. 77

Figures

1-5. Maps showing:

1. Location of the upper Illinois River Basin .................................................. 4

2. Land use in the upper Illinois River Basin, 1970 ............................................. 5

3. Locations of the eight fixed surface-water stations in the upper Illinois River Basin ................. 7

4. Locations of the low-flow synoptic-survey surface-water sampling sites in the upper Illinois River

Basin, July 25 through August 13,1988.................................................... 13

5. Locations of the 1990 storm synoptic-survey surface-water sampling sites in the Kankakee River

Basin ............................................................................... 14

6. Boxplots showing distribution of nutrient concentrations at the eight fixed surface-water stations in the

upper Illinois River Basin, April 1987 through August 1990......................................... 22

7. Boxplots showing distribution of nutrient concentrations, by land-use classification, in surface-water 

samples collected at the low-flow synoptic-survey sites in the upper Illinois River Basin, July 26 through 

August 13, 1988 ........................................................................... 32

8-17. Maps showing spatial distribution of:

8. Total nitrogen concentrations at the low-flow synoptic-survey surface-water sites in the upper

Illinois River Basin, July 26 through August 13, 1988......................................... 33

9. Dissolved nitrite plus nitrate concentrations at the low-flow synoptic-survey surface-water sites in the

upper Illinois River Basin, July 26 through August 13,1988.................................... 34

10. Dissolved ammonia nitrogen concentrations at the low-flow synoptic-survey surface-water sites in the

upper Illinois River Basin, July 26 through August 13, 1988.................................... 35

11. Total organic nitrogen concentrations at the low-flow synoptic-survey surface-water sites in the

upper Illinois River Basin, July 26 through August 13,1988.................................... 36

12. Total phosphorus concentrations at the low-flow synoptic-survey surface-water sites in the upper

Illinois River Basin, July 26 through August 13, 1988......................................... 37

13. Total nitrogen loads at the low-flow synoptic-survey surface-water sites in the upper Illinois River

Basin, July 26 through August 13, 1988.................................................... 41

14. Dissolved nitrite plus nitrate nitrogen loads at the low-flow synoptic-survey surface-water sites in the

upper Illinois River Basin, July 26 through August 13,1988.................................... 42

15. Dissolved ammonia nitrogen loads at the low-flow synoptic-survey surface-water sites in the

upper Illinois River Basin, July 26 through August 13,1988.................................... 43

Contents V
16. Total organic nitrogen loads at the low-flow synoptic-survey surface-water sites in the upper

Illinois River Basin, July 26 through August 13, 1988......................................... 44

17. Total phosphorus loads at the low-flow synoptic-survey surface-water sites in the upper Illinois

River Basin, July 26 through August 13,1988 ............................................... 45

18. Boxplots showing distributions of nutrient concentrations, by season, at selected fixed surface-water

stations in the upper Illinois River Basin, April 1987 through August 1990 ............................. 48

19. Boxplots showing distributions of streamflow at the eight fixed surface-water stations in the upper

Illinois River Basin, 1987-90 water years ....................................................... 50

20. Graphs showing flow-duration curves at the eight fixed surface-water stations in the upper Illinois

River Basin for the period of record and for the 1987-90 water years.................................. 51

21. Graph showing averaged annual precipitation totals for precipitation monitoring sites in northeastern

Illinois, 1987-90........................................................................... 53

22. Map showing streams in the upper Illinois River Basin designated as secondary-contact waters ............. 60

23. Map showing spatial distribution of dissolved oxygen concentrations at the low-flow synoptic-survey

surface-water sites in the upper Illinois River Basin, July 26 through August 13, 1988 .................... 63

24. Graphs showing variations in temperature and dissolved oxygen concentrations at selected fixed

surface-water stations in the upper Illinois River Basin during 36-hour periods .......................... 65

25. Graphs showing temporal variation of fecal coliform and Escherichia coli densities at the eight fixed

surface-water stations in the upper Illinois River Basin, April 1987 through August 1990.................. 71

26. Map showing spatial distribution of Escherichia coli densities at the low-flow synoptic-survey

surface-water sites in the upper Illinois River Basin, July 26 through August 13,1988 .................... 75

TABLES

1. Selected information for the eight fixed surface-water stations in the upper Illinois River Basin, April 1987

through August 1990 ......................................................................... 8

2. Physical properties, nutrient forms, and bacteria species analyzed in water samples collected in the upper

Illinois River Basin, April 1987 through August 1990 ............................................... 9

3. Names and numbers for surface-water sites sampled during the low-flow and storm synoptic surveys in the

upper Illinois River Basin...................................................................... 11

4. Results of analyses for nutrient concentrations in standard reference samples processed during the 1987 and

1988 low-flow synoptic surveys in the upper Illinois River Basin....................................... 15

5. Results of analyses for nutrient concentrations in sample-processing water (blanks), at 6:00 a.m.,

August 2, 1988 .............................................................................. 16

6. Results of analyses of duplicate surface-water samples collected at Kankakee River near Wilmington, III.,

August 4, 1988 .............................................................................. 17

7. Results of analyses of split surface-water samples collected at Fox River at Montgomery, 111., July 29, 1988..... 18

8. Concentrations of selected nutrient forms in water samples from nearshore locations in southwestern

Lake Michigan .............................................................................. 20

9. Percentage of total nitrogen and total phosphorus concentrations in the upper Illinois River Basin attributed

to specific nutrient forms at the eight fixed surface-water stations ...................................... 23

10. Mean annual nutrient loads and yields at the eight fixed surface-water stations in the upper Illinois River Basin,

April 1987 through August 1990 ................................................................ 24

11. Results of the Spearman rank correlation test for physical properties and nutrient forms at the eight fixed

surface-water stations in the upper Illinois River Basin, April 1987 through August 1990 ................... 27

12. Statistical summary of physical properties and nutrient concentrations from surface-water samples collected

during the low-flow synoptic survey in the upper Illinois River Basin, July 26 through August 13, 1988........ 31

13. Estimated nutrient loads during low flow at the synoptic-survey surface-water sites in the upper Illinois

River Basin, July 26 through August 13, 1988...................................................... 39

14. Results of the seasonal Kendall trend test for nutrient concentrations at the eight fixed surface-water stations

in the upper Illinois River Basin, January 1978 through August 1990 ................................... 46

15. Results of the Spearman rank correlation test for streamflow and total nitrite plus nitrate concentrations during

the 1990 storm synoptic survey at six surface-water sites in the upper Illinois River Basin................... 49

16. Estimated annual nutrient inputs to the upper Illinois River Basin from various sources..................... 55

VI Contents
17. Federal water-quality criteria and State water-quality standards for nutrients in surface water in the upper

Illinois River Basin........................................................................... 59

18. Statistical summary of dissolved oxygen concentrations in surface-water samples collected at the eight fixed

stations in the upper Illinois River Basin, April 1987 through August 1990............................... 61

19. Number of samples collected at the eight fixed surface-water stations in the upper Illinois River Basin and 

number of samples with dissolved oxygen concentrations that were less than the Illinois, Indiana, or 

Wisconsin water-quality standards............................................................... 64

20. Results of the Spearman rank correlation test between dissolved oxygen concentrations and streamflow, 

water temperature, and chlorophyll-a concentrations at the eight fixed surface-water stations in the upper 

Illinois River Basin, April 1987 through August 1990 ............................................... 66

21. Statistical summary of bacteria densities at the eight fixed surface-water stations in the upper Illinois River

Basin, April 1987 through August 1990 .......................................................... 68

22. Relations of Federal water-quality criteria and State water-quality standards to bacteria densities at the

eight fixed surface-water stations in the upper Illinois River Basin, April 1987 through August 1990 .......... 69

23. Escherichia coli densities in water samples collected at selected sites downstream from wastewater-treatment

plants in the upper Illinois River Basin, June 28-30, 1988 ............................................ 70

24. Results of the seasonal Kendall trend test for fecal-coliform bacteria densities at the eight fixed surface-water

stations in the upper Illinois River Basin, 1978-90.................................................. 74

CONVERSION FACTORS AND ABBREVIATED WATER-QUALITY UNITS

Multiply By To obtain

inch (in.) 25.4 millimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

square mile (mi2) 2.590 square kilometer

foot per second (ft/s) 0.3048 meter per second

cubic foot per second (ft^/s) 0.02832 cubic meter per second

million gallons per day (Mgal/d) 0.04381 cubic meter per second

ton, short 0.9072 megagram

ton per acre 0.0002241 megagram per square meter

ton per day (ton/d) 0.0105 kilogram per second

ton per year 0.9072 megagram per second

ton per square mile (ton/mi2) 0.3503 tonne per square kilometer

ton per square mile per year [(ton/mi2)/yr] 0.3503 tonne per square kilometer per year

Temperature is given in degrees Celsius (°C), which can be converted to degrees Fahrenheit (°F) by use of the following equation:

°F=1.8(°C)+32

Abbreviated water-quality units used in this report

col/100 mL colonies per 100 milliliters

mm millimeter

mg/L milligram per liter

um micrometer

[ig/L microgram per liter

uS/cm microsiemen per centimeter at 25° Celsius

Contents VII
Water-Quality Assessment of the Upper Illinois River 

Basin in Illinois, Indiana, and Wisconsin: Nutrients, 

Dissolved Oxygen, and Fecal-Indicator Bacteria in 

Surface Water, April 1987 through August 1990

SyPaulJ. Terrio

Abstract

Data collected during the pilot phase of the 

U.S. Geological Survey's National Water-Quality 

Assessment (NAWQA) program in the upper 

Illinois River Basin were used to describe the 

presence, spatial distribution, and temporal variability of nutrients, dissolved oxygen (DO), and 

fecal-indicator bacteria in selected streams during 

1987-90 and to identify, where possible, factors 

affecting in-stream concentrations and loads of 

these constituents.

Streams in the upper Illinois River Basin 

receive nutrient inputs from many different 

sources within the basin, including wastewatertreatment plants, agricultural runoff, urban runoff, 

ground-water discharge, diversions from Lake 

Michigan, eroded soils, and transported plant 

material.

Nutrient concentrations in the upper Illinois 

River Basin were larger than nutrient concentrations typically found in Midwestern streams, and 

most of the largest nutrient concentrations and 

loads were found in the urban areas of the basin. 

Median concentrations of total nitrogen at eight 

NAWQA fixed stations ranged from 2.2 to 

9.7 mg/L (milligrams per liter). Most of the 

nitrogen in upper Illinois River Basin streams 

was in the form of nitrate, except at two sites 

where either ammonia nitrogen or organic nitrogen comprised a large part of the total nitrogen 

concentration. Median concentrations of total 

phosphorus at the fixed stations ranged from 0.06 

to 0.84 mg/L. The spatial distribution of total

phosphorus concentrations was similar to that 

of total nitrogen concentrations the smallest 

concentrations were present in the agricultural 

Kankakee River Basin and the largest in the urban 

Des Plaines River Basin.

Total nitrogen concentrations were correlated with streamflow at all but one of the fixed 

stations. Positive correlations were found at 

stations in predominantly agricultural basins, and 

negative correlations were found at stations in 

urban areas.

Approximately 252,000 tons of nitrogen 

and 94,000 tons of phosphorus are input to 

streams in the upper Illinois River Basin annually. 

Only 74,730 tons of nitrogen and 3,850 tons of 

phosphorus are exported from the upper Illinois 

River Basin each year via the Illinois River. 

These figures correspond to 30 and 4 percent of 

the nitrogen and phosphorus inputs, respectively. 

During low-flow conditions, the nutrient load in 

streams in the Des Plaines River Basin accounted 

for virtually all of the low-flow nitrogen load in 

the upper Illinois River Basin, with other streams 

contributing a relatively minor load. Upward 

trends in total nitrogen concentrations from 

1978-90 were found at three of the fixed stations, 

and downward trends in total phosphorus concentrations were found at two stations.

Median DO concentrations measured 

at the fixed stations during routine monthly 

sampling (daylight hours) ranged from 3.4 to 

12.2 mg/L. During a low-flow synoptic sampling (measurements made prior to sunrise), 

all DO concentrations in the Fox River Basin

Abstract 1
equaled or exceeded 5.0 mg/L, the Illinois waterquality standard for general-use waters. DO 

concentrations during the low-flow synoptic sampling at 59 percent of the sampled stream sites in 

the agricultural Kankakee River Basin and at 

49 percent of the sites in the Des Plaines River 

Basin were less than 5.0 mg/L. Neither stream 

size nor land use appeared to affect DO concentrations at the synoptic sites significantly. 

Upward trends in DO concentrations were indicated at the two most downstream stations in the 

upper Illinois River Basin. The water quality at 

these two stations represents the aggregate water 

quality of streams draining the entire upper 

Illinois River Basin.

The NAWQA program used both fecal 

coliform and Escherichia coll to indicate bacterial 

contamination. Fecal-coliform densities at the 

fixed stations ranged from 1 to 45,000 colonies 

per 100 milliliters. Median fecal-coliform densities were one or two orders of magnitude larger 

at two stations in the Des Plaines River Basin 

than at the other fixed stations. From 30 to 

100 percent of the stream-water samples collected 

at stations in the Des Plaines River Basin had 

Escherichia coll densities greater than the Federal 

criteria for a single sample for infrequently used, 

full-body-contact water. Trend analyses for 

bacteria indicated significant downward trends 

in bacteria densities at three fixed stations: 

Iroquois River near Chebanse, 111., Fox River at 

Algonquin, 111., and Fox River at Dayton, 111.

INTRODUCTION

Beginning in 1986, the Congress appropriated 

funds for the U.S. Geological Survey (USGS) to test 

and refine concepts for a National Water-Quality 

Assessment (NAWQA) program. The goals of the 

program are to 

1. Provide a nationally consistent description of 

current water-quality conditions for a large part 

of the Nation's water resources;

2. Define long-term trends (or lack of trends) in 

water quality; and

3. Identify, describe, and explain, as possible, the 

major factors that affect observed water-quality 

conditions and trends. 

Information from this program will be obtained

on a continuing basis and will be made available to

water managers, policy makers, and the public. This 

information will provide an improved scientific basis 

for evaluating the effectiveness of water-qualitymanagement programs and for predicting the likely 

effects of contemplated changes in land- and watermanagement practices. A detailed description of 

the goals and concepts of the NAWQA program is 

presented by Hirsch and others (1988).

At present, the program is completing a pilot 

phase that lasted about 4 years. The upper Illinois 

River Basin in Illinois, Indiana, and Wisconsin was 

one of four surface-water basins selected to test and 

develop assessment concepts. The other surfacewater pilot project areas were the Yakima River Basin 

in Washington, the lower Kansas River Basin in 

Kansas and Nebraska, and the Kentucky River Basin 

in Kentucky.

Some of the water-quality issues of concern in 

the upper Illinois River Basin are the presence and 

distribution of nutrients, dissolved oxygen (DO), and 

fecal-indicator bacteria. Nutrients discussed in this 

report include nitrogen and phosphorus compounds 

that are required for plant production. These nutrients can also stimulate excessive algal growth and 

subsequent eutrophication if present in excessive concentrations. Sampling efforts were conducted to 

address the following questions:

1. Where do these constituents present problems in 

the upper Illinois River Basin and what are the 

causes of these problems?

2. What are the concentrations and loads of nutrients 

and the concentrations of DO and fecal-indicator 

bacteria in the upper Illinois River Basin, and 

what are the effects of these concentrations and 

loads on the aquatic ecosystem and uses of the 

stream water?

3. How have the distributions and concentrations of 

these constituents changed over time in the upper 

Illinois River Basin?

4. How do the various point and nonpoint sources in 

the upper Illinois River Basin affect the concentrations of these constituents?

Purpose and Scope

This report describes the presence, spatial distribution, and temporal variability of nutrients, DO, and 

fecal-indicator bacteria in streams in the upper Illinois 

River Basin during 1987-90, and identifies, where

2 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
possible, factors affecting in-stream concentrations 

and loads of these constituents. Monthly data collected during April 1987 through August 1990 at 

8 fixed-station sampling sites and data collected during synoptic surveys in 1988 and 1990 at approximately 70 surface-water sampling sites are used to 

determine distributions, seasonality, and variability of 

constituent concentrations and loads. The monthly 

NAWQA data for 1987-90 are combined with 

monthly Illinois Environmental Protection Agency 

(IEPA) data for 1978-86 to analyze long-term trends.

Description of the Upper Illinois River Basin

A brief description of the upper Illinois River 

Basin is presented here, and the reader is referred to 

Mades (1987) for a more complete description of the 

study area. The upper Illinois River Basin is located 

in northeastern Illinois, northwestern Indiana, and 

southeastern Wisconsin. The upper Illinois River 

Basin is drained by the Illinois River at a point just 

downstream from the mouth of the Fox River near 

Ottawa, 111. (fig. 1). The basin includes an area of 

10,949 mi2 and coincides with hydrologic subregion 

0712 as defined by the Water Resources Council 

(Seaber and others, 1987).

The upper Illinois River Basin includes three 

principal streams: the Kankakee, Fox, and 

Des Plaines Rivers. The Kankakee River drains 

5,165 mi2, or 47.2 percent of the upper Illinois River 

Basin area, and flows westerly from its headwaters in 

St. Joseph County, Ind., to its confluence with the 

Des Plaines River. The Kankakee River is 130 mi 

long. In Indiana, the Kankakee River and its tributaries have been dredged and straightened to facilitate 

drainage of wetland areas for conversion to farmland.

The Fox River originates in Waukesha County, 

Wis., and flows southerly for 180 mi where it discharges to the Illinois River near Ottawa, 111. The 

Fox River has a drainage area of 2,658 mi2, or 

24.3 percent of the upper Illinois River Basin.

The Des Plaines River is 130 mi long, and its 

headwaters are in Kenosha County, Wis. The 

Des Plaines River flows southward, through the 

Chicago metropolitan area, to its confluence with the 

Kankakee River. The Des Plaines River Basin 

includes 2,111 mi2, or 19.3 percent of the upper 

Illinois River Basin. Included in the Des Plaines 

Basin is the Calumet River system, which historically

drained to Lake Michigan but was altered in the early 

1900's to drain to the Des Plaines River. The 

Chicago Sanitary and Ship Canal (CSSC), which conveys water diverted from Lake Michigan, is included 

in the Des Plaines River Basin.

The Illinois River originates at the confluence of 

the Kankakee and Des Plaines Rivers. The Illinois 

River flows south and southwest for 273 mi where it 

discharges to the Mississippi River; only the most 

upstream 33 mi are included in the upper Illinois River 

Basin. The area drained directly by the Illinois River 

includes 1,015 mi2, or 9.2 percent of the upper Illinois 

River Basin.

The major land uses in the upper Illinois River 

Basin are agricultural (77 percent), urban and industrial (18 percent), and forest (5 percent). Figure 2 

shows level I land-use classifications in the upper 

Illinois River Basin, as defined by Anderson and 

others (1976). Most of the upper Illinois River Basin 

is used for row-crop agriculture, primarily the production of corn and soybeans. Some areas in the northern part of the basin are used for pasture. The two 

principle urbanized areas in the upper Illinois River 

Basin are the greater Chicago metropolitan area and a 

corridor of urban development along the middle reach 

of the Fox River. The Kankakee River Basin is 

90 percent agricultural, 5 percent urban, and 5 percent 

forest. The Fox River Basin is 85 percent agricultural and 15 percent urban. In contrast to the 

Kankakee and Fox River Basins, the Des Plaines 

River Basin is 60 percent urban, 30 percent agricultural, and 10 percent forest.

The upper Illinois River Basin has a continental 

climate, and significant variations in temperature and 

precipitation can occur in any given year. Summers 

generally are hot and humid, with July temperatures 

averaging around 25°C and humidity often more than 

75 percent. Winters are cold, with an average January temperature of -6°C. An average of 162 days 

spans the time between the last 0°C day in the spring 

and the first 0°C day in the fall.

Average annual precipitation in the upper 

Illinois River Basin varies geographically. The 

average (1951-80) annual precipitation in the northern 

parts of the basin was 32 in., and the average annual 

precipitation for the eastern parts of the upper Illinois 

River Basin was 40 in. (Moody and others, 1986). 

Approximately 50 percent of the annual precipitation 

falls during the growing season, from May through 

October.

Introduction
89° 88°

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EXPLANATION

 . UPPER ILLINOIS RIVER 

BASIN BOUNDARY

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ST JOSEPH^ 1

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§

Base from U.S. Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic Projection

Standard parallels 33° and 45°, central meridian -89°

Figure 1 . Location of the upper Illinois River Basin.

0

r20 40 MILES

20 40 KILOMETERS

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria In Surface Water, April 1987 Through August 1990
/ ^"xSsix \ EXPLANATION

 BASIN BOUNDARY

URBAN LAND 

AGRICULTURAL LAND 

FOREST

'-v - * -/ ' ;- -< / - \ 7 :sfi:1-.i:.-:--^\^

Base from US Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° end 45°, central meridian -89°

40 MILES

20 40 KILOMETERS

Figure 2. Land use in the upper Illinois River Basin, 1970.

Introduction
Several sources of streamflow are found in the 

upper Illinois River Basin, including precipitation and 

runoff, ground-water flow, return flows, and water 

diverted from Lake Michigan. Return flow is water 

discharged to streams after use. An example of 

return flow is ground water withdrawn for domestic 

use and returned to a stream after wastewater treatment. In the upper Illinois River Basin, water is 

diverted or pumped from Lake Michigan for water 

supply, wastewater dilution, and commercial purposes. 

In the Des Plaines River Basin, a large percentage of 

the total streamflow is attributed to return flows and 

Lake Michigan diversions. Over half of the streamflow in the CSSC can be return flow. Streamflow in 

the other river basins, however, is derived primarily 

from runoff and ground-water flow.

DATA COLLECTION AND SOURCES

The upper Illinois River Basin NAWQA program included extensive water-quality-data collection 

at a network of 8 sampling stations (fixed stations) 

and at approximately 70 synoptic-survey sampling 

sites. Sample collection for nutrient, DO, and fecalindicator bacteria analyses began at the fixed stations 

in April 1987 and continued through August 1990. 

Samples were collected at synoptic sites in 1988 

and 1990. Data from the IEPA ambient waterquality-monitoring network were available for 38 sites 

throughout the Illinois part of the upper Illinois River 

Basin for 1978-90. Data on the quality of wastewater-treatment-plant effluent were available from 

individual treatment-plant operators.

Fixed-Station Sampling

The upper Illinois River Basin NAWQA program incorporated a network of eight fixed stations for 

the purposes of 

1. Describing the seasonal variations and the 

frequency of occurrence of selected waterquality constituents;

2. Estimating loads of constituents past the stations 

and attempting mass balances of selected target 

constituents between stations; and

3. Defining long-term trends in water quality.

The eight fixed stations were selected based on 

basin hydrology, land use, geographical location, and

stream characteristics. Most of the fixed stations 

were in a downstream segment of a major river or 

tributary. Two of the fixed stations were selected to 

provide information on stream-water-quality characteristics from specific land-use areas, including areas 

of potential pollution. The locations of the eight 

fixed stations are shown in figure 3, and information 

about each of the stations is given in table 1.

Monthly water-quality samples were collected 

at the eight fixed stations from April 1987 through 

August 1990. Samples were collected on a fixed 

frequency in order to provide a data set suitable for 

trend analysis. The fixed frequency sampling also 

provided samples from low-, medium-, and high-flow 

periods during 1987-90. Water-quality samples collected at the fixed stations were analyzed for physical 

properties and chemical constituents including nutrients, metals, ions, sediment, bacteria, and organic 

compounds. The physical properties and nutrient 

forms analyzed in the fixed-station samples that are 

discussed in this report are listed in table 2.

Except for water used for bacteria analyses, 

water samples for constituents discussed in this report 

were collected using depth- and width-integrating 

techniques (Illinois Environmental Protection Agency, 

1987; Ward and Harr, 1990). These techniques 

provide a sample representative of the entire stream. 

Samples for bacteriological analyses were collected as 

grab samples about 1 ft below the water surface at the 

center of the stream. Physical properties (temperature, DO concentration, pH, and specific conductance) 

were measured in situ with a portable multi-parameter 

water-quality meter.

Several different laboratories were used to analyze the water-quality samples collected at the fixed 

stations. Nutrient concentrations were analyzed by 

both the USGS National Water-Quality Laboratory 

(NWQL) and IEPA laboratories because the agencies 

apply different nutrient preservatives for stream-water 

samples. The USGS preserves nutrient samples by 

adding mercuric chloride to the sample and chilling 

the samples to 4°C (Timme, 1994). The IEPA uses 

sulfuric acid and chilling to 4°C for nutrient sample 

preservation (Illinois Environmental Protection 

Agency, 1987). Except for long-term trend analyses, 

nutrient data in this report were from samples preserved with mercuric chloride. Data used for longterm trend analyses included nutrient data from 

samples preserved with both sulfuric acid and mercuric chloride. Fecal-coliform bacteria analyses were

6 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
EXPLANATION

 BASIN BOUNDARY

SURFACE-WATER STATION 

AND MAP REFERENCE 

NUMBER-See table ~

^/WISCONSIN

LAKE MICHIGAN

\ Chicago Sanitary and 

\ Ship Canal

Base from US Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° and 45°, central maridian -89°

40 MILES

20 40 KILOMETERS

Figure 3. Locations of the eight fixed surface-water stations in the upper Illinois River Basin.

Data Collection and Sources 7
0

Table 1 . Selected information for the eight fixed surface-water stations in the upper Illinois River Basin, April 1987 through August 1990 

[mi2, square mile; ft'/s, cubic feet per second; <, less than]

3 

iIg815'W2*

8

f g

I

3H

Through 1990 water year

Station 

number

05520500

0552600005532500

0553699505540500

055435000555000005552500

Station name and 

latitude and longitude

Kankakee River at Momence, 111.

Lat 41° 09' 36", long 87° 40' 07"Iroquois River near Chebanse, 111.Lat 41° 00' 32", long 87° 49' 27"

Des Plaines River at Riverside, 111.

Lat 41° 49' 20", long 87° 49' 15"

Chicago Sanitary and Ship Canal

at Romeoville, 111.

Lat 41° 38' 26", long 88° 03' 38"

Du Page River at Shorewood, 111.

Lat 41° 31' 20", long 88° 1 1' 35"Illinois River at Marseilles, 111.Lat 41° 19' 40", long 88° 43' 10"

Fox River at Algonquin, 111.

Lat 42° 09' 59", long 88° 17' 25"

Fox River at Dayton, 111.Lat 41° 23' 12", long 88° 47' 26"

Drainage 

area 

(mi2)

2,294

2,091

630

739

324

8,259

1,403

2,642

Years 

surfacewater 

record

75

67

47

6

50

71

75

75

Yeara 

waterquality 

record

1513

8

8

26

1613

13

Mean 

discharge 

(ft3/s)

1,9981,664

508

3,788

270

10,688

863

1,743

Mean 

discharge 1987-90 

(tf/s)

2,224

1,554

680

3,707

330

9,377

950

1,964

Land use 

(percentage of drainage area)

Agriculture

88

964422

51

78

64

74

Urban

3

1

45

65

37

14

13

11

Forest

636

8

4

5

12

8

Other

3

<1

55

83

11

7
Table 2. Physical properties, nutrient forms, and bacteria species analyzed in water samples collected in the upper 

Illinois River Basin, April 1987 through August 1990 

[--, no data]

Constituent 

(WATSTORE1 code)

Streamflow

(00060 or 00061)

Temperature (water)

(00010)

Specific conductance

(00095)

pH

(00400)

Dissolved oxygen

(00300)

Nitrogen, organic, dissolved

(00607)

Nitrogen, ammonia, dissolved

(00608)

Nitrogen, ammonia, total

(00610)

Nitrogen, nitrite, dissolved

(00613)

Nitrogen, ammonia, un-ionized

(00619)

Nitrogen, ammonia plus organic, dissolved

(00623)

Nitrogen, ammonia plus organic, total

(00625)

Nitrogen, nitrite plus nitrate, total

(00630)

Nitrogen, nitrite plus nitrate, dissolved

(00631)

Phosphorus, total

(00665)

Phosphorus, dissolved

(00666)

Phosphorus, orthophosphate, dissolved 

(00671)

Solids, residue on evaporation, 180°C,

dissolved (70300)

Suspended sediment, percent finer than

0.062 mm (70331)

Suspended sediment

(80154)

Carbon, organic, total

(00680)

Carbon, organic, dissolved

(00681)

Carbon, organic, suspended

(00689)

Fecal coliform, 0.45 micron filter

(31616)

Escherichia coli

(31648)

Chlorophyll-a

(32209)

Chlorophyll-a, phytoplankton

(70953)

Fixed 

stations

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

-

Low-flow synoptics

1987

X

X

X

X

X

X

X

X

X

X

X

X

-

X

X

-

X

1988

X

X

X

X

X

_

X

X

_

X

X

X

X

X

X

X

X

-

X

X

Storm-event 

synoptic

X

X

X

_-

X

X

X

X

X

-

-

'National WATer Data STQrage and BEtreival System.

Data Collection and Sources 9
performed either by USGS field personnel or by IEPA 

laboratory personnel. E. Coli analyses were performed only by USGS personnel.

The quality-assurance and quality-control 

(QA/QC) practices used during the fixed-station 

sampling program included duplicate samples, split 

samples, blanks, and standard reference samples. 

Duplicate samples were discrete samples collected 

from the same location at about the same time. 

These samples were used to determine the variation 

in concentrations because of sample-collection and 

field-processing techniques. A split sample was a 

sample that was collected and subsequently divided 

into two separate samples for processing and analysis. 

The results of split samples provided information on 

the variation in concentrations attributed to sample 

processing and laboratory analysis. Blanks were 

samples of the distilled or deionized water used in the 

sample processing. The blank samples were used to 

determine the constituent concentrations in the processing water and the contamination from processing 

equipment. Standard reference samples consisted of 

water prepared by the NWQL with known nutrient 

concentrations. This water was processed and analyzed in the same manner as the stream-water samples. 

The results of standard reference samples were used to 

show whether contamination or constituent loss 

resulted from the processing, shipping, and analysis 

procedures. Sullivan and Blanchard (1994) discuss 

the NAWQA sampling program design, data-collection methods, laboratory analyses, and QA/QC procedures used in the fixed-station sampling program.

Synoptic Sampling

In addition to the fixed-station sampling program, water-quality samples were collected during 

several synoptic surveys. Synoptic surveys were 

designed to collect data from a large number of sites 

throughout the upper Illinois River Basin, or a specific 

part thereof, during a brief period of time and during 

specific flow or climatic conditions. The purposes of 

these synoptic surveys were to (1) provide a finer 

degree of spatial resolution for selected water-quality 

conditions than attainable from the fixed-station sampling network, and (2) document the spatial distribution of concentrations and loads of selected target 

variables in relation to land and water uses and to 

land- and waste-management practices. Hirsch and

others (1988) provide an overview of the concepts for 

the NAWQA program including a discussion of the 

synoptic sampling strategy. ^

Three synoptic surveys were scheduled as part 

of the upper Illinois River Basin NAWQA project. 

These surveys included low-flow surveys in 1987 and 

1988, and a storm survey in the Kankakee River Basin 

in 1990. The 1987 low-flow synoptic survey was 

cancelled because of heavy rainfall after some of the 

sites were sampled. The analyses of water samples 

collected during the 1987 synoptic survey are not 

included in this report, but the 1987 QA/QC results are 

included because they are applicable to sampling 

methods used for the 1988 synoptic survey and the 

fixed-station sampling methods. The low-flow synoptic survey in 1988, which targeted nutrients, DO, 

and fecal-indicator bacteria, was conducted during a 

warm, dry period when problems associated with 

these constituents commonly occur. The sites sampled during the low-flow synoptic survey were 

selected by several criteria, as discussed in Hirsch and 

others (1988). Sites sampled included locations 

along the main stems of the major streams in the upper 

Illinois River Basin, locations downstream from 

known or suspected nutrient-enrichment sources 

(enriched sites), and locations representing the major 

land uses in the basin agricultural, urban, and forest. 

Fifty-nine sites were sampled throughout the upper 

Illinois River Basin from July 25 through August 13, 

1988. The names and station numbers of the synoptic sites are listed in table 3, and the locations of the 

sites are shown in figure 4. The constituents sampled 

during each of the synoptic surveys varied, as shown 

in table 2. Samples collected during the synoptic 

surveys also were collected using documented USGS 

methods (Ward and Harr, 1990). All samples collected during the synoptic surveys were analyzed by 

USGS field personnel or by the NWQL.

The 1990 storm synoptic survey targeted agricultural organic compounds but also included analyses 

for total nitrite plus nitrate concentrations. Samples 

were collected before, during, and after storms to 

determine changes in concentrations related to 

changes in runoff and streamflow. The samples were 

collected from May through July 1990 at 17 sites in 

the Kankakee River Basin (fig. 5; table 3). Samples 

were collected as near as possible to the runoff peak 

and during the duration of the runoff hydrograph at 

stations on the Iroquois River and Sugar Creek. At 

Iroquois River at Chebanse, samples were collected

10 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria In Surface Water, April 1987 Through August 1990
Table 3. Names and numbers for surface-water sites sampled during the low-flow and storm synoptic surveys in 

the upper Illinois River Basin 

[USGS, U.S. Geological Survey]

Map 

reference 

number

1

3

4

5

7

8

10

11

12

13

14

15

16

18

19

20

21

22

23

26

28

29

30

31

32

33

34

37

38

40

41

42

44

45

47

48

51

52

54

55

58

61

62

67

69

USGS 

station 

number

05515000

05515500

05516500

05517000

05517500

05517530

05517890

05518000

05519000

05520150

05520500

05521000

05522500

05523500

05524500

05525000

05525290

05525500

05525540

05525600

05526000

05526130

05526410

05527500

05527800

05528000

05529000

05531175

05531500

05532500

05533020

05534050

05535172

05536000

05536108

05536142

05536290

055363252

05536700

05536995

05538008

05539360

05539900

05540290

05540500

Station name

Kankakee River near North Liberty, Ind.

Kankakee River at Davis, Ind.

Yellow River at Plymouth, Ind.

Yellow River at Knox, Ind.

Kankakee River at Dunns Bridge, Ind.

Kankakee River near Kouts, Ind.

Cobb Ditch near Kouts, Ind.

Kankakee River at Shelby, Ind.

Singleton Ditch at Schneider, Ind.

Singleton Ditch at County Road 52 near Illiana Heights, Ind.

Kankakee River at Momence, 111.

Iroquois River at Rosebud, Ind.

Iroquois River at Rensselaer, Ind.

Slough Creek near Collegeville, Ind.

Iroquois River near Foresman, Ind.

Iroquois River at Iroquois, 111.

Sugar Creek near Stockland, 111.

Sugar Creek at Milford, 111.

Iroquois River near Watseka, 111.

Spring Creek near Oilman, 111.

Iroquois River near Chebanse, 111.

Kankakee River near Bourbonnais, 111.

Rock Creek at Highway 102 near Deselm, 111.

Kankakee River near Wilmington, 111.

Des Plaines River at Russell, 111.

Des Plaines River near Gurnee, 111.

Des Plaines River near Des Plaines, 111.

Salt Creek at Wood Dale, 111.

Salt Creek at Western Springs, 111.

Des Plaines River at Riverside, 111.

Flag Creek at 91st Street near Willow Springs, VI.

Des Plaines River at Lockport, 111.

Skokie River at Happ Road at Northfield, 111.

North Branch Chicago River at Niles, 111.

North Shore Channel at Devon Avenue at Chicago, 111.

Chicago Sanitary and Ship Canal at Forest View, 111.

Little Calumet River at South Holland, 111.

Little Calumet River at Halsted Avenue at Harvey, 111.

Calumet Sag Channel at Sag Bridge, 111.

Chicago Sanitary and Ship Canal at Romeoville, 111.

Des Plaines River above Brandon Road Dam at Joliet, 111.

Des Plaines River below Lock and Dam at Rockdale, 111.

West Branch Du Page River near West Chicago, 111.

Du Page River near Naperville, 111.

Du Page River at Shorewood, 111.

Synoptic Sampling 11
Table 3. Names and numbers for surface-water sites sampled during the low-flow and storm synoptic surveys in 

the upper Illinois River Basin Continued

Map 

reference 

number

70

71

72

73

74

75

76

77

78

79

80

82

86

87

89

90

91

92

95

98

99

100

101

102

103

uses

station 

number

05541498

05541508

05541710

05541745

05542000

05543484

05543500

05543814

05544090

05544315

05544908

05545300

05548280

05549500

05550000

05550500

05551000

05551540

05551937

05552400

05552500

405443087112800

411616087013100

411714086325600

412147086113700

Station name

Illinois River above Dresden Island Dam near Minooka, 111.

Illinois River below Dresden Island Dam near Minooka, 111.

Aux Sable Creek near Morris, 111.

Mazon River near Gardner, 111.

Mazon River near Coal City, 111.

Illinois River above Marseilles Dam at Marseilles, 111.

Illinois River at Marseilles, 111.

Pewaukee River at State Route 164 at Waukesha, Wis.

Mukwonago River at Marsh Road near Mukwonago, Wis.

Fox River near Big Bend, Wis.

Honey Creek at Bell School Road near East Troy, Wis.

White River near Burlington, Wis.

Nippersink Creek near Spring Grove, 111.

Fox River near McHenry, 111.

Fox River at Algonquin, 111.

Poplar Creek at Elgin, III

Fox River at South Elgin, 111.

Fox River at Montgomery, I1L

Big Rock Creek at Route 276 near Piano, 111.

Indian Creek at Route 258 at Wedron, 111.

Fox River at Dayton, El.

Iroquois River above Slough Creek near Rensselaer, Ind.

Reeves Ditch at State Route 49 near Kouts, Ind.

Yellow River above State Route 8 near Knox, Ind.

Yellow River at North Hickory Road near Inwood, Ind.

by an automatic sampler actuated by an increase in 

stream stage. Samples collected by the automatic 

sampler were analyzed only for dissolved nitrite plus 

nitrate.

Quality-assurance and quality-control practices 

implemented during the low-flow synoptic surveys 

were similar to those used for the fixed-station sampling program and consisted of duplicate samples, 

split samples, blanks, and standard reference samples. No nutrient QA/QC samples were collected 

during the 1990 storm synoptic survey. Sample 

collection and processing methods used during the 

synoptic surveys were comparable to the methods 

used for the fixed-station sampling, and the QA/QC 

samples used for the fixed-station program also are 

applicable to the synoptic samples (Sullivan and 

Blanchard, 1994).

The results of the QA/QC samples for the 

1987 and 1988 low-flow synoptic surveys are given 

in tables 4-7. The results of the standard reference

samples processed during the synoptic surveys 

(table 4) showed several dissolved nitrite and nitrate 

concentrations and one dissolved orthophosphate 

concentration slightly below the mean standard reference concentrations for these constituents. This is 

an indication that some of the analyses for these nutrient forms might indicate concentrations slightly less 

than the true concentrations. The blank analyses 

(table 5) indicated that there were some concentrations 

of nitrogen species that were larger than desirable in 

sample-processing water. Other analyses of water 

from the same source were performed as part of the 

NAWQA fixed-station program and did not indicate 

concentrations at these levels. The analysis of the 

sample-processing water during the synoptic survey, 

however, indicated some contamination was present in 

the water or was being introduced by the sampling 

equipment or processing personnel. Depending on 

the stream sample concentration, the contributions of 

nitrogen from the sample-processing water ranged

12 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria In Surface Water, April 1987 Through August 1990
43'

SAMPLING SITE AND 

MAP REFERENCE 

NUMBER-See table 3

Chicago Sanitary and 

Canal

Base from US Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° end 45°, central meridian -89°

20 40 KILOMETERS

Figure 4. Locations of the low-flow synoptic-survey surface-water sampling sites in the upper Illinois River 

Basin, July 25 through August 13,1988.

Synoptic Sampling 13
88° 30'

41° 30'

4V

40° 30*

LAKE MICHIGAN

Base from US. Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parelells 33° and 45°. central meridian -89°

20 40 MILES

20 40 KILOMETERS

EXPLANATION

22

BASIN BOUNDARY

SAMPLING SITE AND MAP 

REFERENCE NUMBER-See table 3

Figure 5. Locations of the 1990 storm synoptic-survey surface-water sampling sites in the Kankakee River 

Basin.

14 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
Table 4. Results of analyses for nutrient concentrations in standard reference samples processed during the 

1987 and 1988 low-flow synoptic surveys in the upper Illinois River Basin 

[mg/L, milligrams per liter]

Constituent

Nitrogen, organic, dissolved (mg/L)

Nitrogen, ammonia, dissolved (mg/L)

Nitrogen, nitrite, dissolved (mg/L)

Nitrogen, nitrate, dissolved (mg/L)

Nitrogen, ammonia plus organic, total (mg/L)

Phosphorus, total (mg/L)

Phosphorus, orthophosphate, dissolved (mg/L)

Nitrogen, organic, dissolved (mg/L)

Nitrogen, ammonia, dissolved (mg/L)

Nitrogen, nitrite, dissolved (mg/L)

Nitrogen, nitrate, dissolved (mg/L)

Nitrogen, ammonia plus organic, total (mg/L)

Phosphorus, total (mg/L)

Phosphorus, orthophosphate, dissolved (mg/L)

Nitrogen, organic, dissolved (mg/L)

Nitrogen, ammonia, dissolved (mg/L)

Nitrogen, nitrite, dissolved (mg/L)

Nitrogen, nitrate, dissolved (mg/L)

Nitrogen, ammonia plus organic, total (mg/L)

Phosphorus, total (mg/L)

Phosphorus, orthophosphate, dissolved (mg/L)

Nitrogen, organic, dissolved (mg/L)

Nitrogen, ammonia, dissolved (mg/L)

Nitrogen, nitrite, dissolved (mg/L)

Nitrogen, nitrate, dissolved (mg/L)

Nitrogen, ammonia plus organic, total (mg/L)

Phosphorus, total (mg/L)

Phosphorus, orthophosphate, dissolved (mg/L)

Mean

standard

reference

concentration

0.62

.67

.07

1.13

1.29

.63

.28

.62

.67

.07

1.13

1.29

.63

.28

.68

.70

.12

.85

1.38

.66

.49

.68

.70

.12

.85

1.38

.66

.49

Standard

deviation

for

reference

samplea

August 24, 1987, at 10:00 a.m.

0.27

.10

.01

.08

.37

.05

.02

August 24, 1987, at 1 1:00 a.m.

.27

.10

.01

.08

.37

.05

.02

July 26, 1988, at 5:40 a.m.

.29

.08

.04

.08

.21

.04

.03

August 4, 1988, at 7:50 a.m.

.29

.08

.04

.08

.21

.04

.03

Measured

sample

concentration

0.49

.71

.07

1.03

1.20

.67

.25

.61

.69

.07

1.13

1.30

.67

.26

.58

.72

.05

.85

1.30

.66

.48

.76

.74

.05

.86

1.50

.66

.48

from almost insignificant to comprising the entire 

concentration determined for the sample. The 

results of the duplicate samples (table 6) showed little 

variation in concentrations that could be attributed to 

sample processing and analysis for most constituents. 

There were some significant differences in the concentrations of total phosphorus and total organic carbon. 

The results of the split sample analyses (table 7) 

showed some small differences in most constituent 

concentration analyses. The largest differences 

between duplicate samples were for those constituents 

associated with particulate matter. Concentrations 

of these constituents are typically more variable than

dissolved forms because they are affected to a greater 

degree by physical differences and forces in the 

streams. None of the differences was considered to 

be so large as to identify any problem in the sample 

collection or analyses.

Data Compiled From Other Sources

The IEPA has operated an ambient waterquality-monitoring network throughout the State since 

1975. This network includes 38 sites in the upper 

Illinois River Basin where water-quality samples are

Data Compiled From Other Sources 15
Table 5. Results of analyses for nutrient concentrations 

in sample-processing water (blanks), at 6:00 a.m., 

August 2, 1988 

[mg/L, milligrams per liter]

Concentration 

_______Constituent_____________(mg/L)

Nitrogen, organic, dissolved 0.17

Nitrogen, ammonia, dissolved .03

Nitrogen, nitrite, dissolved .01

Nitrogen, nitrate, dissolved .09

Nitrogen, ammonia plus organic, dissolved .20

Nitrogen, ammonia plus organic, total .30

Nitrogen, nitrite plus nitrate, dissolved . 10

Phosphorus, total .02

Phosphorus, dissolved .02

Phosphorus, orthophosphate, dissolved .02

Carbon, organic, total .20

NUTRIENTS, DISSOLVED OXYGEN, AND 

FECAL-INDICATOR BACTERIA

This section presents results of analyses and 

interpretation of nutrient, DO, and fecal-indicator bacteria data from the upper Illinois River Basin NAWQA 

program, April 1987 through August 1990. Sources 

of nutrients, DO, and bacteria in the upper Illinois 

River Basin are identified, and contributions of the 

constituents from these sources to streams in the upper 

Illinois River Basin are estimated. Characteristics of 

these constituents and water-quality conditions in the 

upper Illinois River Basin related to the constituents 

are examined.

collected on a 6-week frequency using sample-collection methods comparable to those used by the USGS. 

As mentioned, the IEPA uses sulfuric acid to preserve 

nutrient samples, whereas the USGS uses mercuric 

chloride. Six of the eight NAWQA fixed stations 

were located at IEPA water-quality-monitoring sites. 

Because data were available at these stations since 

1978, the IEPA data were combined with the data collected through the NAWQA program to determine 

long-term trends in nutrient concentrations. The 

IEPA incorporates standard QA/QC procedures into 

the ambient water-quality-monitoring program, 

including equipment blanks, duplicate samples, sample splits, QC field visits, and standard-reference 

samples. A discussion of the lEPA's field QA/QC 

practices is included in IEPA (1987).

Approximately 180 wastewater-treatment plants 

are located in the upper Illinois River Basin. Requests for treatment-plant-effluent flow rates and 

water-quality data for periods coinciding with the 

1988 synoptic survey were sent to personnel at each 

treatment plant. Approximately two-thirds of the 

personnel at the treatment plants responded. The 

data aided in assessing the effect of effluents on 

stream-water quality during low-flow periods. The 

available data generally were limited to those constituents required for the treatment plant to fulfill regulatory requirements and seldom included any associated 

in-stream water-quality data. Because data from the 

wastewater-treatment plants were used only for background information and were not used in calculations 

or computations, the QA/QC information for these 

data were not determined.

Nutrients

Nutrients affect aquatic environments because 

they are required for plant growth. Aquatic plants 

provide food, oxygen, and habitat for fish and other 

aquatic fauna and are required for a healthy aquatic 

system. Excessive nutrient levels, however, can 

cause prolific algal growth and eutrophic conditions, 

resulting in subsequent decomposition of plant and 

organic matter, increased oxygen demand, foul odors, 

and fish kills.

The nutrients of primary importance in most 

stream environments are nitrogen and phosphorus. 

Carbon, silica, and trace elements also function as 

nutrients, but these elements usually are available in 

sufficient quantities to meet the metabolic needs of the 

aquatic organisms. Both nitrogen and phosphorus 

are found in the environment at several oxidation 

states and in several different forms.

Nitrogen is present in water as nitrite and nitrate 

anions, in cationic form as ammonium, and at intermediate oxidation states as part of organic solutes (Hem, 

1985). Organic nitrogen includes nitrogen present in 

peptides, proteins, nucleic acids, urea, and synthetic 

organic materials. The sum of organic nitrogen and 

ammonia may be determined analytically and is 

referred to as kjeldahl nitrogen. Wastewaters may 

contain other forms of nitrogen, such as cyanide.

Nitrite is an intermediate state of nitrogen, 

present either during the oxidation of ammonia to 

nitrate or during the reduction of nitrate. Nitrite generally is detected only in trace quantities in surface 

waters. Nitrate is easily leached from soils and can 

be found in large concentrations in agricultural areas

16 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
Table 6. Results of analyses of duplicate surface-water samples collected at Kankakee River near 

Wilmington, III., August 4, 1988

[ft3/s, cubic feet per second; mg/L, milligrams per liter; NO2+NO3, nitrite plus nitrate; diam., diameter; %, percent; mm, millimeters; 

Hg/L, micrograms per liter, USOS, U.S. Geological Survey; <, less than; Numbers in parentheses are National Water Data Storage 

and Retrieval System parameter codes]

Number of 

Streamflow sampling Gage 

Agency Agency instantaneous points height 

Time collecting analyzing (ftVs) (count) (feet) 

(hour) sample sample (00061) (00063) (00065)

0545 

0715

USGS USGS 

USGS USGS

E420 

E414

10 

10

0.62 

.62

Nitrogen, 

ammonia 

dissolved 

(mg/L as N) 

(00608)

0.07 

.07

Nitrogen, 

nitrita 

dissolved 

(mg/L as N) 

(00613)

0.01 

.01

Nitrogen, 

ammonia + 

organic 

dissolved 

(mg/L as N) 

(00623)

0.3

.2

Nitrogen, 

ammonia + 

organic 

total 

(mg/L as N) 

(00625)

0.3

.2

Nitrogen, 

NO2 + NO3 

dissolved 

(mg/L as N) 

(00631)

<0.1 

.1

Phoephorus 

total 

(mg/L as P) 

(00665)

0.18 

.18

Phosphorus 

dissolved 

(mg/L as P) 

(00666)

0.11 

.12

Phosphorus 

ortho, 

dissolved 

(mg/L as P) 

(00671)

0.09 

.09

Sediment 

Carbon, suspended 

organic sieve 

totsl diam. % finer 

(mg/L ss C) than .062 mm 

(00680) (70331)

6.5 

7.0

92 

99

Chlorophyll-a 

phytoplankton 

chromofluorom 

fcg/L) 

(70953)

11 

11

Chlorophyll-fa 

phytoplankton 

chromofluorom 

(MI/L) 

(70954)

1.9 

2.1

Sediment, 

suspended 

(mg/L) 

(80154)

18 

15

E, Estimated

where nitrogen fertilizers are used. Ammonium, on 

the other hand, adsorbs to soil particles and clays 

because of its positive charge and is not leached 

readily from soils (American Public Health Association and others, 1985). Ammonium and organic 

nitrogen are converted to nitrite and nitrate by nitrifying bacteria, and the presence of these nitrogen forms 

generally indicates a nearby pollutant source.

Phosphorus is not as abundant in the environment as nitrogen and often is the limiting element for 

plant growth in aquatic systems (Hem, 1985). 

Phosphorus is usually found as phosphate (fully 

oxidized phosphorus) in natural waters. For most 

stream waters, the H2PO4 and HPC>4 orthophosphate 

species are the predominant dissolved phosphorus 

forms. Organophosphates (organically bound phosphates) also are common in stream systems. Phosphate is found in solution, as part of detritus, attached

to sediment particles and in the bodies of aquatic 

organisms. Much of the phosphorus in stream systems adsorbs to paniculate matter and is not directly 

available for uptake by plants and algae.

Five nutrient forms were selected to represent 

nutrient conditions in the upper Illinois River Basin: 

total nitrogen as nitrogen (total nitrogen), dissolved 

nitrite plus nitrate as nitrogen (NC>2 + NC^), dissolved 

ammonia nitrogen as nitrogen (ammonia), total 

organic nitrogen as nitrogen (organic nitrogen), and 

total phosphorus as phosphorus (total phosphorus). 

Total nitrogen concentrations were calculated as the 

sum of dissolved NC>2 + NC>3 concentration and total 

organic plus ammonia concentration. Dissolved 

NO2 + NO3 concentrations were used rather than total 

NC>2 + NO3 concentrations because the number of 

dissolved analyses was larger than the number of 

total analyses and the concentrations of dissolved

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 17
Table 7. Results of analyses of split surface-water samples collected at Fox River at Montgomery, III., 

July 29,1988

[ft3/s, cubic feet per second; mg/L, milligrams per liter; NO2+NO3, nitrite plus nitrate; diam., diameter, %, percent; mm, millimeters; 

Hg/L, micrograms per liter; USGS, U.S. Geological Survey; <, less than; Numbers in parentheses are National Water Data Storage 

and Retrieval System parameter codes]

Time 

(hour)

0730 

0731

Agency 

collecting 

sample

USGS 

USGS

Agency 

analyzing 

sample

USGS 

USGS

Streamflow 

Instantaneous 

(tf/s) 

(00061)

E258 

E258

Number of 

sampling 

points 

(count) 

(00063)

11 

11

Nitrogen, 

ammonia 

dissolved 

(mg/L as N) 

(00608)

<0.01 

<.01

Nitrogen, 

nitrite 

dissolved 

(mg/L as N) 

(00613)

<0.01 

<.01

Nitrogen, 

ammonia + 

organic 

dissolved 

(mg/LaaN) 

(00623)

1.2 

1.4

Nitrogen, 

ammonia + 

organic 

total 

(mg/L as N) 

(00625)

2.4 

2.6

Nitrog0n, 

NO2 + NO3 

diasolved 

(mg/L as N) 

(00631)

<0.1 

<.l

Phosphorus 

total 

(mg/L as P) 

(00665)

0.38 

.42

Phosphorus 

dissolved 

(mg/L as P) 

(00666)

0.17 

.16

Phosphorus 

ortho, 

dissolved 

(mg/L as P) 

(00671)

0.13 

.13

Carbon, 

organic 

total 

(mg/L as C) 

(00680)

16 

19

Sediment 

suspended 

sieve 

dlam. % finer 

than .062 mm 

(70331)

92 

94

Chlorophyll-a 

phytoplanMon 

chromofluorom 

(H9/L) 

(70953)

59 

59

Chlorophyll-b 

phytoplankton 

chromofluorom

(nan.)

(70954)

8.9 

8.9

Sediment, 

suspended 

(mg/L) 

(80154)

27 

28

E, Estimated

NO2 + NC>3 were virtually always the same or slightly 

greater or less than corresponding concentrations of 

total NO2 + NO3. Concentrations of nutrients in this 

report are expressed as concentrations of elemental 

nitrogen and phosphorus in milligrams per liter, unless 

otherwise indicated.

Sources of Nutrients in the Upper Illinois River 

Basin

In-stream nutrient concentrations and loads in 

the upper Illinois River Basin are affected by a number 

of sources including wastewater-treatment-plant effluents, agricultural runoff, urban runoff, ground-water 

contribution, diversions from Lake Michigan, soil 

erosion, and plant material. The primary sources of 

nutrients to the upper Illinois River Basin are wastewater-treatment-plant effluents and agricultural fertilizers. In the early 1980's, approximately 46 percent 

of the total nutrient load in upper Illinois River Basin

streams was attributed to point sources and about 

54 percent of the load was from nonpoint sources 

(Gianessi, 1986).

Most domestic and many industrial wastewaters 

have relatively large concentrations of ammonia, 

nitrate, and phosphorus in comparison to stream-water 

concentrations. Approximately 1,815 Mgal/d, or 

about 2,810 ft Is, of effluent is discharged to upper 

Illinois River Basin streams by 181 wastewatertreatment plants (Zogorski and others, 1990). 

Seventy-two of these treatment plants have capacities 

of 1 Mgal/d or more, and three treatment plants have 

capacities greater than 300 Mgal/d. Wastewatertreatment-plant effluents comprised about 30 percent 

of the total streamflow from the upper Illinois River 

Basin in 1988.

The water quality of treatment-plant effluent 

varies, depending on the type of treatment. Discharges from the three largest treatment plants comprised about 75 percent (2,100 f^/s) of the total

18 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
treatment-plant effluent discharged in the upper 

Illinois River Basin. These three plants only provide 

secondary treatment. Flow-weighted average nutrient concentrations of the effluents from the three 

largest treatment plants in the upper Illinois River 

Basin were calculated for 1988. The flow-weighted 

average nutrient concentrations for the treatmentplant effluents for 1988 were derived by multiplying 

the 1988 average nutrient concentration for each treatment plant by the average effluent discharge from the 

treatment plant in 1988, summing the products from 

the three treatment plants, and dividing by the cumulative discharge for all three treatment plants. The 

average nitrogen concentration was 8.40 mg/L, 

and the average phosphorus concentration was 

0.90 mg/L. Jerri Davis (U.S. Geological Survey, 

written commun., 1993) estimated that approximately 

26,000 tons per year of nitrogen and 5,410 tons per 

year of phosphorus are discharged annually to streams 

from treatment plants in the upper Illinois River Basin.

Because nearly 75 percent of the upper Illinois 

River Basin is active agricultural land, the input of 

nutrients to streams from agricultural activities is 

substantial. Gianessi (1986) estimated that nonurban 

(agricultural) land contributed about 55,500 tons per 

year of kjeldahl nitrogen and 7,340 tons per year of 

phosphorus to upper Illinois River Basin streams. 

The water chemistry of runoff from agricultural land 

depends on a number of factors including the specific 

agricultural use, topography, soil type, climate, and 

hydrologic conditions. These factors vary temporally and spatially throughout the upper Illinois River 

Basin. In addition, the quality of water from overland runoff can differ substantially from that of tile 

drainage. Most forms of nutrients are found in agricultural runoff, but, because nitrate is both a relatively 

stable form and soluble in water, it is generally the 

most prevalent form of nitrogen in streams. Concentrations of total nitrogen in agricultural runoff have 

been found to range from 4.9 to 35 mg/L (Dornbush 

and others, 1974; Uttormark and others, 1974; 

Donigian and Crawford, 1976; and Roseboom and 

others, 1990). The same studies found concentrations of total phosphorus in agricultural runoff to 

range from 0.02 to 3.45 mg/L. Nutrient concentrations in feedlot runoff can be orders of magnitude 

larger than concentrations in field runoff. Approximately 132 feedlots of various sizes are located in the 

upper Illinois River Basin. High concentrations of

nutrients in runoff from these feedlots typically are 

found after relatively small, local storms (Roseboom 

and others, 1990).

Application of fertilizers on agricultural fields 

is a major source of nutrients in the upper Illinois 

River Basin. Amounts of nutrients in fertilizers sold 

in Illinois counties in the upper Illinois River Basin in 

1988 were available from the Illinois Department of 

Agriculture (1988a, 1988b). An average quantity of 

nitrogen and phosphorus was calculated for the Illinois 

part of the upper Illinois River Basin, and this average 

was assumed for the parts of the upper Illinois River 

Basin in Indiana and Wisconsin. Assuming that all 

of the fertilizer purchased was applied to fields in 

1988, approximately 215,000 tons per year of nitrogen 

and 87,000 tons per year of phosphorus were introduced into streams draining the upper Illinois River 

Basin through fertilizer application.

Approximately 13 percent (1,425 mi2) of the 

upper Illinois River Basin is urbanized. Urban runoff 

can have large nutrient concentrations. Many factors, including antecedent conditions, local land use, 

drainage-system design, climatic season, and streetcleaning practices affect nutrient concentrations in 

runoff from urban areas. Ammonia and phosphorus 

often are found in urban areas because of their domestic and industrial uses. Results from several studies 

(Uttormark and others, 1974; Donigian and Crawford, 

1976; and Manning and others, 1977) show that concentrations of total nitrogen and total phosphorus in 

runoff from urban areas were found to range from 0.5 

to 33 mg/L and from less than 0.2 to 5.0 mg/L, respectively. Uttormark and others (1974) found that 0.60 

ton/mi2 of nitrogen and 0.88 ton/mi2 of phosphorus 

were exported in runoff from urban areas in Madison, 

Wis. Assuming that these yields apply to urban areas 

of the upper Illinois River Basin, approximately 855 

tons per year of nitrogen and 1,250 tons per year of 

phosphorus are conveyed to upper Illinois River Basin 

streams in runoff from urban areas.

Data for concentrations and loads of nitrate 

and ammonium ions in precipitation were available 

from the National Atmospheric Deposition Program 

for five sites in, or near, the upper Illinois River Basin 

for 1988 (National Atmospheric Deposition Program, 

1989). Concentration and load data from these five 

sites were averaged to obtain values representative 

of the entire upper Illinois River Basin. The average 

concentrations of nitrate and ammonia were 0.37 

and 0.31 mg/L, respectively. Precipitation varies

Nutrients, Dissolved Oxygen, and Fecai-lndicator Bacteria 19
throughout the upper Illinois River Basin both 

spatially and temporally, but 36 in. per year is an 

approximate annual average for the upper Illinois 

River Basin. Atmospheric deposition contributes 

approximately 10,600 tons of nitrate and 8,850 tons 

of ammonia to the upper Illinois River Basin land 

surface each year. How much of the atmospheric 

depositional load of ammonium and nitrate is conveyed to upper Illinois River Basin streams is not 

known, but this deposition could represent a significant contribution of nutrients to the upper Illinois 

River Basin.

In 1985, an average of 650 ft3/s of ground 

water was withdrawn from aquifers in the upper 

Illinois River Basin (Mades, 1987). Ground-water 

withdrawals comprised about 7 percent of the total 

median annual discharge from the upper Illinois River 

Basin. Water-quality data for public water-supply 

wells in Illinois were available for 1985-87 (Voelker 

and others, 1987). Total nitrite plus nitrate concentrations typically were less than or equal to 0.10 mg/L, 

concentrations of total ammonia nitrogen generally 

were about 0.40 mg/L, and phosphorus concentrations 

typically were about 0.02 mg/L. Contributions of 

nutrient loads from ground-water withdrawals are 

included in the estimates for wastewater-treatmentplant effluents. Water also was conveyed to upper 

Illinois River Basin streams through ground-water 

flow. Ground-water flow in the upper Illinois River 

Basin was estimated by two methods. One method 

assumed that streamflow during dry weather conditions (the drought of 1988) at sites unaffected by 

return flows or diversions was derived primarily from 

ground-water flow. Streamflow yields calculated 

for these sites were used to estimate the basin-wide 

ground-water flow. The second method determined 

ground-water flow as the difference between streamflow out of the upper Illinois River Basin and the 

known qualities of ground-water withdrawals (subsequently return flows) and diversions from Lake 

Michigan. These methods derived estimates of 

ground-water flow of 876 and 1,176 f^/s, respectively. 

From the average of these two estimates, groundwater flow contributes about 102 tons per year of 

nitrite plus nitrate, 408 tons per year of ammonia, and 

20 tons per year of phosphorus to upper Illinois River 

Basin streams (unpublished data on file in Urbana 

office of the U.S. Geological Survey, 1989).

Approximately 3,470 ft3/s of water were 

withdrawn or diverted from Lake Michigan during

1981-85 and subsequently contributed to the streamflow in the upper Illinois River Basin (U.S. Army 

Corps of Engineers, 1990). Of this total, about 

1,660 ft3/s were pumped from Lake Michigan for 

water-supply purposes and about 1,810 ft^s were 

diverted from the lake via channels. Approximately 

33 percent of the streamflow at Illinois River at 

Marseilles consists of water diverted or withdrawn 

from Lake Michigan.

Nutrient concentrations in Lake Michigan 

generally are smaller than nutrient concentrations 

at most of the fixed stations. Table 8 shows concentrations of selected nutrient species in water samples 

collected in southwestern Lake Michigan near the 

three principal diversion locations. The concentrations in table 8 and the estimates of Lake Michigan 

diversions were used to derive estimated nutrient loads 

in water diverted from Lake Michigan. Approximately 1,100 tons per year of nitrogen and 180 tons 

per year of phosphorus are conveyed to the upper 

Illinois River Basin in water diverted from Lake 

Michigan.

Soil erosion is a conveyance mechanism for 

the transport of nutrients from the land surface to 

streams. Soil erosion can result wherever soil is 

exposed to wind, rain, or other forms of disturbance. 

Several different forms of erosion convey soil particles to streams in the upper Illinois River Basin, but 

the most important process in terms of the total 

quantity of soil transported is sheet and rill erosion. 

Sheet and rill erosion occurs in almost all agricultural 

areas (U.S. Department of Agriculture, 1980). 

Sediment the erosion, transport, and deposition 

in streams and lakes is a major contamination 

problem in Illinois and is often cited as the primary

Table 8. Concentrations of selected nutrient forms in 

water samples from nearshore locations in southwestern 

Lake Michigan1

[Data from Torrey, 1976]

Concentration, 

in milligrams per liter

Nutrient

Nitrogen, ammonia, total, as N

Nitrogen, nitrite, total, as N

Nitrogen, nitrate, total, as N

Nitrogen, organic, total, as N

Phosphorus, total, as P

Range

0.01 -0.23

.005- .007

.08 - .24

.20 - .50

.01 - .78

Average

0.15

.006

.15

.30

.10

'Data from locations in Lake Michigan near the Wilmette, 

Chicago, and Calumet diversions.

20 Nutrients, Dissolved Oxygen, and Fecai-lndicator Bacteria in Surface Water, April 1987 Through August 1990
nonpoint-source-contamination concern (Illinois 

Environmental Protection Agency, 1992). An 

IEPA assessment found that sediment and turbidity 

were the primary nonpoint-source contaminants in 

85 percent of the assessed streams (Illinois Environmental Protection Agency, 1986).

The Soil Conservation Service estimated 

that the total annual sheet and rill erosion in the 

Illinois portion of the upper Illinois River Basin was 

20,498,000 tons, or 3,052 tons/mi2 (U.S. Department 

of Agriculture, 1980). This estimate corresponds 

with an IEPA estimate of 4.9 tons per acre, or 

3,136 tons/mi2 annually (Illinois Environmental 

Protection Agency, 1979). Using these figures, 

approximately 34,000,000 tons per year of sediment 

are eroded annually in the upper Illinois River Basin.

Reliable estimates of the amounts of eroded 

sediment that is actually conveyed to streams have not 

been made (Illinois Environmental Protection Agency, 

1979). Sediment delivery ratios (the ratio of sediment delivered to a stream in relation to the total 

amount of erosion in the watershed above the particular point in the stream) generally are unknown and 

variable. Delivery ratios for several lakes in central 

Illinois ranged from 0.24 to 0.34 (Illinois Environmental Protection Agency, 1979), but ratios in other areas 

of the State might vary substantially.

Only a rough approximation of the amounts of 

nitrogen and phosphorus delivered to upper Illinois 

River Basin streams can be made. Approximately 

34 million tons per year of sediment are eroded in the 

upper Illinois River Basin. Using a sediment delivery ratio of 0.25, about 8.5 million tons per year of 

sediment are delivered to upper Illinois River Basin 

streams. Manning and others (1977) found that soils 

in the upper Illinois River Basin were about 25 percent 

nitrogen and about 15 percent phosphorus, by weight. 

Using these percentages, about 2.1 million tons per 

year of nitrogen and about 1.3 million tons per year 

of phosphorus are transported to upper Illinois River 

Basin streams with the eroded soil. These figures 

include nutrients that are washed off of agricultural 

fields in association with sediment particles.

Nutrients also can be conveyed to stream water 

from plant material. As plants decompose or are 

consumed by aquatic fauna and microbial organisms, 

nutrients are released to the stream water. Some 

plant materials that might be important in upper 

Illinois River Basin streams are leaf litter, aquatic 

flora, and crop residue. Estimates of the contributions of nutrients to streams in the upper Illinois River

Basin from plant material are unknown and amounts 

likely vary widely from year to year. In addition, 

nitrogen fixation of atmospheric nitrogen by certain 

bacteria and blue-green algae also can contribute to 

the nitrogen in streams in the upper Illinois River 

Basin, although the quantity of nitrogen contributed 

by these processes is undetermined.

Data Analysis

Data collected in the NAWQA program were 

analyzed to determine spatial distributions and temporal variability of nutrient concentrations and loads in 

streams in the upper Illinois River Basin. The effects 

of nutrient sources and other factors on the concentration of nutrients in streams in the upper Illinois River 

Basin was also investigated.

Boxplots of concentrations of the five indicator 

nutrient forms at the fixed stations are shown in 

figure 6. Boxplots graphically summarize and portray the characteristics of one or more data sets. 

Chambers and others (1983) provide a comprehensive 

description of boxplot construction and attributes.

The contributions of individual nutrient forms to 

the total nutrient concentration varied among the fixed 

stations. Approximate percentages of total nitrogen 

and total phosphorus concentrations attributed to 

specific nutrient forms at each of the fixed stations is 

given in table 9.

Nutrient loads were computed using all data 

collected by the USGS from 1987 through 1990, 

including data from the fixed-station sampling program and the synoptic surveys. Instantaneous loads 

at the fixed stations were calculated as the product of 

concentration and streamflow at the time the sample 

was collected. Regression equations relating instantaneous loads and streamflows were determined for 

each station. The regression equations were then 

used to estimate daily loads from mean daily streamflows. A comprehensive discussion of the procedures and equations used to calculate constituent loads 

at the fixed stations is presented by Smoot and others 

(1991). Some discrepancies between NC>2 + NC>3 

loads and total nitrogen loads were found at Iroquois 

River near Chebanse and Fox River at Dayton. 

These inconqruities might be because total nitrogen 

concentrations were calculated from monthly samples, 

whereas concentrations of dissolved NC>2 + NC>3 were 

determined from monthly samples, plus samples

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 21
20

0<

H g 15

o3= ui ZSfc

2Z J 10

14 28 40 55 69 76 89 99 

MAP REFERENCE NUMBER

EXPLANATION

-Data value(s) exceeding upper 

quartile plus 3 times the 

interquartile range

-Data value(s) exceeding upper 

quartile plus 1.5 times the 

interquartile range but less 

than upper quartile range plus 

3 times the interquartile range

-Largest data value less than or 

equal to the upper quartile plus 

1.5 times the interquartile range

-Upper quartile _____ 

(75th percentile)

- Median 

(50th percentile)

-Lower quartile 

(25th percentile)

Smallest data value greater than or 

equal to the lower quartile minus 

1.5 times the interquartile range

I

INTERQUARTILE 

RANGE

___I

^Maximum detection limit

MAP

REFERENCE 

NUMBER STATION NAME

14 Kankakee River at Momence, III.

28 Iroquois River near Chebanse, III.

40 Des Plaines River at Riverside, III.

55 Chicago Sanitary and Ship Canal at

	Romeoville, III.

69 Du Page River at Shorewood, III.

76 Illinois River at Marseilles, III.

89 Fox River at Algonquin, III.

99 Fox River at Dayton, III.

14 28 40 55 69 76 89 99 

MAP REFERENCE NUMBER

Figure 6. Distribution of nutrient concentrations at the eight fixed surface-water stations in the upper Illinois River 

Basin, April 1987 through August 1990.

22 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bactaria in Surface Wster, April 1987 Through August 1990
Table 9. Percentage of total nitrogen and total phosphorus concentrations in the upper Illinois River Basin attributed to 

specific nutrient forms at the eight fixed surface-water stations

Average percentage of total nitrogen 

concentration from indicated nitrogen form 

Dissolved Total 

nitrite plus Dissolved Total un-ionized

Average percentage of total 

phoaphorus concentration 

from Indicated phosphorus form 

Dissolved

Station name 

(map reference number1 )

Kankakee River at Momence, 111. (14)

Iroquois River near Chebanse, 111. (28)

Des Plaines River at Riverside, 111. (40)

Chicago Sanitary and Ship Canal at

Romeoville, 111. (55)

Du Page River at Shorewood, Dl. (69)

Illinois River at Marseilles, Dl. (76)

Fox River at Algonquin, 111. (89)

Fox River at Dayton, Dl. (99)

nitrate 

nitrogen

69

88

73

56

83

72

27

59

ammonia 

nitrogen

6

2

6

26

2

7

4

2

organic 

nitrogen

22

8

21

16

12

18

60

37

ammonia 

nitrogen

0.1

.03

.1

.2

.08

.1

.3

.2

Dissolved 

phosphorus2

29

54

84

82

88

75

15

29

orthophosphorus

27

44

77

72

84

66

10

26

'See table 3 and figure 4.

2Dissolved phosphorus concentration includes phosphorus present as orthophosphorus.

collected during the low-flow and storm synoptic 

surveys. Inclusion of dissolved NC>2 + NC>3 analyses 

from the synoptic-survey data provided more complete coverage of extreme low-flow conditions and 

conditions during storm runoff. Regrettably, lowflow and storm-runoff data were not available for all 

of the nutrient forms. Estimates of the total nutrient 

loads leaving the upper Illinois River Basin were made 

using the sum of the loads at Illinois River at 

Marseilles and Fox River at Dayton. Mean annual 

loads of nutrients at the fixed stations are given in 

table 10. Treatment of data with concentrations 

below the detection limit can affect computed loads. 

Load estimates in table 10 include estimates when data 

below the detection limit were set to the detection 

limit, to one-half of the detection limit, and to zero.

Yields are defined as the load divided by the 

upstream drainage area. Yields are used to compare 

contributions of constituents from different areas on a 

per-unit basis. In this report, yields are expressed as 

tons per square mile per year. The calculation of 

yields for CSSC at Romeoville was not appropriate 

because most of the streamflow in the CSSC is return 

flow or water diverted from Lake Michigan. The 

mean annual yields at the other fixed stations are given 

in table 10.

Spearman's rank correlation test (Conover, 

1980) was used to determine the extent of mutual 

dependence among the different nutrient forms and

among nutrient concentrations and other properties 

of the stream water. The correlation test identified 

nutrient concentrations and physical properties that 

increased or decreased similarly. A correlation was 

considered significant only if Spearman's rho, rs, was 

greater than or equal to 0.50, if there were at least 

10 data pairs, and if the level of significance of the test 

was less than or equal to 0.10. In all instances when 

rs was greater than or equal to 0.5, the level of significance was much less than 0.1. The results of the 

correlation tests are given in table 11.

Data from the low-flow synoptic surveys provided a greater degree of spatial resolution than the 

fixed-station data but represent nutrient concentrations 

during warm weather and low-flow conditions only. 

Statistical summaries of physical properties and nutrient concentrations in samples collected during the 

1988 low-flow synoptic survey are given in table 12. 

A comprehensive presentation of the data collected 

during the low-flow synoptic survey can be found in 

Coupe and others (1989). Boxplots of nutrient concentrations for synoptic sites representing several 

land-use categories are shown in figure 7. Enriched 

sites are locations downstream from known or suspected sources or inputs of nutrients. The spatial 

distributions for concentrations of the five indicator 

nutrient forms during the low-flow synoptic survey 

are shown in figures 8-12.

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 23
Table 10. Mean annual nutrient loads and yields at the eight fixed surface-water stations in the upper Illinois River Basin, 

[(ton/mi2)/yr, tons per square mile per year; n.a., not applicable; --, no data]

Map 

reference 

number2

Number 

of 

observaStation name tiona

Mean annual load (tona)

Cenaored data 

aet to higheat 

detection limit

Censored data 

aet to one-half 

detection limit

Censored 

data set 

to zero

[(to

Total nitrogen

14 Kankakee River at Momence, 111. 43

28 Iroquois River near Chebanse, 111. 33

40 Des Plaines River at Riverside, 111. 41

55 Chicago Sanitary and Ship Canal 40

	at Romeoville, 111.

69 Du Page River at Shorewood, 111. 41

76 Illinois River at Marseilles, 111. 46

89 Fox River at Algonquin, 111. 33

99 Fox River at Dayton, 111. 33

14 Kankakee River at Momence, 111. 44

28 Iroquois River near Chebanse, 111. 48

40 Des Plaines River at Riverside, 111. 45

55 Chicago Sanitary and Ship Canal 46

	at Romeoville, 111.

69 Du Page River at Shorewood, 111. 47

76 Illinois River at Marseilles, 111. 53

89 Fox River at Algonquin, 111. 46

99 Fox River at Dayton, 111. 45

14 Kankakee River at Momence, 111. 20

28 Iroquois River near Chebanse, 111. 20

40 Des Plaines River at Riverside, 111. 39

55 Chicago Sanitary and Ship Canal 40

	at Romeoville, 111.

69 Du Page River at Shorewood, 111. 29

76 Illinois River at Marseilles, 111. 48

89 Fox River at Algonquin, 111. 34

99 Fox River at Dayton, 111. 34

7,060

21,720

3,528

24,420

2,570

63,420

2,581

9,930

Dissolved nitrite plus nitrate nitrogen

5,440

23,150

2,350

10,840

1,970

48,040

1,215

11,330

Total organic nitrogen

7,067

22,010

3,528

24,420

2,570

63,420

2,579

9,940

7,067

22,010

3,528

24,420

2,570

63,420

2,579

9,940

5,680

25,570

2,350

10,840

1,970

48,040

1,327

13,700

8,616

84,690

2,350

10,840

1,970

48,040

8,688

135,200

1,940

924

4,570

522

11,320

1,345

3,120

1,950

925

4,570

524

11,330

1,353

3,380

1,950

925

4,570

524

11,330

1,353

3,380
Table 10. Mean annual nutrient loads and yields at the eight fixed surface-water stations in the upper Illinois River Basin, A

August 1990 Continued

»

O »'

8 

I

S.

a.

3 

DD

D) 

I

Map 

reference 

number2

Number 

of 

observaStetion name tions

Mean annual load (tona)

Censored data 

set to highest 

detection limit

Censored data 

set to one-half 

detection limit

Censored 

data aet 

to zero

Me

ann

yie

[(ton/m

Total ammonia nitrogen

14 Kankakee River at Momence, 111. 45

28 Iroquois River near Chebanse, 111. 42

40 Des Plaines River at Riverside, 111. 41

55 Chicago Sanitary and Ship Canal 42

	at Romeoville, 111.

69 Du Page River at Shorewood, 111. 46

76 Illinois River at Marseilles, 111. 50

89 Fox River at Algonquin, 111. 43

99 Fox River at Dayton, 111. 43

14 Kankakee River at Momence, 111. 44

28 Iroquois River near Chebanse, 111. 42

40 Des Plaines River at Riverside, 111. 41

55 Chicago Sanitary and Ship Canal 40

	at Romeoville, 111.

69 Du Page River at Shorewood, 111. 44

76 Illinois River at Marseilles, 111. 47

89 Fox River at Algonquin, 111. 40

99 Fox River at Dayton, 111. 43

14 Kankakee River at Momence, 111. 50

28 Iroquois River near Chebanse, 111. 47

40 Des Plaines River at Riverside, 111. 45

55 Chicago Sanitary and Ship Canal 46

	at Romeoville, 111.

69 Du Page River at Shorewood, 111. 50

76 Illinois River at Marseilles, 111. 53

89 Fox River at Algonquin, 111. 46

99 Fox River at Dayton, 111. 48

291

239

290

8,800

92.8

6,040

166

264

231

200

290

8,800

97.6

6,310

166

264

Dissolved ammonia nitrogen

264 228

228 207

284 283

8,790 8,790

99 102

6,420 6,520

166 159

264 241

Total phosphorus

204 204

338 338

441 441

2,680 2,680

282 282

3,390 3,390

126 126

443 443

231

200

282

8,800

97.6

6,310

166

264

228

207

383

8,790

102

6,520

159

241

204

338

441

2,680

282

3,390

126

443

n

4

n

4

0

0

n

4

M

at
Table 10. Mean annual nutrient loads and yields at the eight fixed surface-water stations in the upper Illinois River Basin, 

August 1990 Continued

Map 

reference 

number2

14

28 

40

55

69 

76

89 

99

Station nsme

Kankakee River at Momence, 111.

Iroquois River near Chebanse, 111. 

Des Plaines River at Riverside, 111.

Chicago Sanitary and Ship Canal 

at Romeoville, 111.

Du Page River at Shorewood, 111. 

Illinois River at Marseilles, 111.

Fox River at Algonquin, 111. 

Fox River at Dayton, 111.

Number 

of 

observations

49

46

45

46

50

53

46 

48

Mean annual load (tons)

Censored dsta Censored data 

set to highest set to one-half 

detection limit detection limit

Dissolved

64.2

155 

310

1,800

202 

2,200

28.3 

157

phosphorus

68.9

159 

310

1,800

202 

2,200

26.5 

157

Cenaored 

data set 

to zero

68.9

159 

310

1,800

202 

2,200

26.5 

157

a

y

[(ton

Dissolved orthophosphorus

14

28 

40

55

69 

76

89 

99

Kankakee River at Momence, 111.

Iroquois River near Chebanse, 111. 

Des Plaines River at Riverside, 111.

Chicago Sanitary and Ship Canal 

at Romeoville, 111.

Du Page River at Shorewood, 111. 

Illinois River at Marseilles, 111.

Fox River at Algonquin, 111. 

Fox River at Dayton, 111.

42

44 

42

40

42 

50

41 

41

57.0

137 

279

1,650

191 

2,000

16.7 

128

68.2

142 

279

1,650

191 

2,000

13.7 

130

68.2

142 

279

1,650

191 

2,000

13.7 

130

'Yield computed from load calculated with censored data set to the highest detection limit.

2See table 3 and figure 4.

3Ratio of largest instantaneous discharge used in estimating transport to largest daily discharge observed during data collection.

Includes water diverted from Lake Michigan and ground-water return flows.
Table 11. Results of the Spearman rank correlation test for physical properties and nutrient forms at the eight fixed 

surface-water stations in the upper Illinois River Basin, April 1987 through August 1990

[rs. Spearman's rho; n, number of observations; shading, correlation is significant according to criteria specified in the text; -, insufficient number of 

observations to determine correlation]

Constituent

Total 

nitrogen

Dissolved 

nitrite 

plus 

nitrate 

nitrogen

Totel 

ammonia 

nitrogen

Total 

organic 

nitrogen

Total 

phosphorus

Kankakee River at Momence, 111. (14)

Total rs

nitrogen n

Dissolved rs

nitrite + nitrate n

Dissolved rs

ammonia n

Total organic rs

nitrogen n

Total rs

phosphorus n

Discharge rs

n

Temperature. rs

water n

Specific rs

conductance n

Suspended rs

sediment n

Chlorophyll-fl, rs

phytoplankton n

1.0000

121

^SsSoS 45 

.2432

40

\ "em

66

.2759

121

f

s^i

-.2877

121

-.2580

121

0

_

1

1.0000

85

.4096

85

.3385

21

.0889

81

* !909r 85" *

*,* i- t

*4?"'"';

-.3104

81

.2100

37

-.4030

33

1.0000

86

.1008

21

.2291

82

.3604

86

-.0787

43

-.0087

81

.3236

38

-.0968

34

1.0000

67

l^^fiBf "67"'"'"'

.2469

61

.3271

66

-.2366

67

1

1

1.0000

169

.1141

162

.4430

129

-.3496

164

.2305

35

.4424

32

Iroquois River near Chebanse, III. (28)

Total rs

nitrogen n

Dissolved rs

nitrite + nitrate n

Dissolved rs

ammonia n

Total organic rs

nitrogen n

Total rs

phosphorus n

Discharge rs 

n

Temperature, rs

water n

Specific rs 

conductance n

Suspended rs

sediment n

Chlorophyll-fl, rs

phytoplankton n

1.0000

55

^MOO

40

.0916

40

.1531

37

.1463

55

r

>£" "-" 

,.6932

-.3063

55

-.1415 

55

0

1

1.0000

287

.2534

97

-.2060

25

.0056

93

.4557 

286.

-.4921

57

.1231 

101

.1204

47

-.4729

34

1.0000

97

.0502

25

.3141

93

.2844 

97

-.2373

49

-.0820 

91

.2170

47

%*' ""

1.0000

40

1 -7030

40 ,'

4<j"~-

.2571

38

40,'

2

2

1.0000

158

.3370 

156

.2859

113

" isf " "" "

»-*** ' _,.«

£,-. .S535> RV -: -OT* ,,,,

44

-.0605

33

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 27
Table 11. Results of the Spearman rank correlation test for physical properties and nutrient forms at the eight fixed 

surface-water stations in the upper Illinois River Basin, April 1987 through August 1990 Continued

Constituent

Total 

nitrogen

Dissolved 

nitrite 

plus 

nitrete 

nitrogen

Total 

ammonia 

nitrogen

Total 

organic 

nitrogen

Total 

phosphorus

Des Plaines River at Riverside, 111. (40)

Total rs

nitrogen n

Dissolved rs

nitrite + nitrate n

Dissolved rs

ammonia n

Total organic rs

nitrogen n

Total rs

phosphorus n

Discharge rs

n

Temperature, rs

water n

Specific rs

conductance n

Suspended rs

sediment n

Chlorophyll-a, rs

phytoplankton n

1.0000

43

7 L, 3' 9353 -

.3051

43

.3558

41

f 18038

43

£-3649

.0510

43

1^5522

43

_

0

.4000

4

1.0000

87

.2222

87

.1280

42

£- '35&F

82

8-T"'

-.0578

43

l^&ns*

84

-.4751

40

-.0386

29

1.0000

87

.0333

42

.0805

82

-.0331

87

-.2393

43

.4355

84

-.0065

40

-.4933

29

1.0000

42

.4874

42

-.3094

42 tw

Tp

-.1305

42

1

.9000

5

1.0000

82

'&'?

.3566

43

.2037

80

-.1675

36

.3544

27

Chicago Sanitary and Ship Canal at Romeoville, III. (55)

Total rs

nitrogen n

Dissolved rs

nitrite + nitrate n

Dissolved rs

ammonia n

Total organic rs

nitrogen n

Total rs

phosphorus n

Discharge rs

n

Temperature, rs

water n

Specific rs

conductance n

Suspended rs

sediment n

Chlorophyll-a rs

phytoplankton n

1.0000

43

.3332

42 __

"42"7149

.4979

43

ipw43

-.3558

42

£~w663Q '42'"

5 -.7416

42

0

_

0

1.0000

111

*.-.S3W

104

-.0264

42

.3535

106

-.3746

108

-.4966

41

.3749

84

-.1716

41

-.2007

31

1.0000

104

.3657

42

.1058

99

-.0734

101

-.3381

41 __ ^*!&I85

83

.0226

41

-.1300

31

1.0000

43

.4167

43

.2024

42

-.2325

42

.2338

42

..

0

0

1.0000

107

-.2000

104

-.2905

42

.3229

80

.1130

37

.0905

29

28 Nutrients, Dissolved Oxygen, and Fecai-lndicator Bacteria in Surface Water, April 1987 Through August 1990
Table 11. Results of the Spearman rank correlation test for physical properties and nutrient forms at the eight fixed 

surface-water stations in the upper Illinois River Basin, April 1987 through August 1990 Continued

Constituent

Total 

nitrogen

Dissolved 

nitrite 

plus 

nitrate 

nitrogen

Total 

smmonia 

nitrogen

Total 

orgsnic 

nitrogen

Total 

phosphorus

Du Page River at Shorewood, 111. (69)

Total rs

nitrogen n

Dissolved rs

nitrite + nitrate n

Dissolved rs

ammonia n

Total organic rs

nitrogen n

Total rs

phosphorus n

Discharge rs 

n

Temperature, rs

water n

Specific rs

conductance n

Suspended rs

sediment n

Chlorophyll-a, rs 

phytoplankton n

1.0000

53 9""'90i^

'4<? * ""

.0887

46

-.3318

38

.3511

53

-.3607 

52

-.4258

53

.4788

53

0

-.5000 

3

1.0000

120

.0378

115 "'^m

33

.4092

109

<R$!& 

118

-.3560

59

1P-.5485' 94 ' "~

-.4311

43 ^S5909" 

V " *

1.0000

115

-.2355

33

-.1917

109

.4079 

115

57

-.3623

90

.1894

43

-.2981

34

1.0000

40

.0910

40

.3469 

39

.4202

38

-.4331

40

2

-.5000 

3

1.0000

161

p*-.692lj 160 *

.0992

104

j;~ .5088*

13(5

-.2036

40

.0342 

33

Illinois River at Marseilles, III. (76)

Total rs

nitrogen n

Dissolved rs

nitrite + nitrate n

Dissolved rs

ammonia n

Total organic rs

nitrogen n

Total rs

phosphorus n

Discharge rs

n

Temperature, rs

water n

Specific rs

conductance n

Suspended rs

sediment n

Chlorophyll-a, rs

phytoplankton n

1.0000

143

r

t':-u&i 

*JZiW

69

.3802

67

.3355

137

-.1327

143

.3900

136

&5g5

142

.4153

142

.0553

37

-.6000

5

1.0000

154

.1273

147

.1728

84

-.3685

145

.4469

148

«£ ?. &- ' *

^ m

101

.3567

146

-.0019

82 t'l-j&iti- '~32 "

1.0000

148

-.2190

83

.1436

143

.0002

146

&899

.4596

142

-.3305

80

-.4799

31

1.0000

157

.0285

157

.1897

149

.0144

148

-.0470

152

.2765

51

-.6669

5

1.0000

219

-.4176

211

.0656

174

.0843

212

.0459

99

.2107

32

Nutrients, Dissolved Oxygen, and FecaMndicstor Bacteria 29
Table 11 . Results of the Spearman rank correlation test for physical properties and nutrient forms at the eight fixed 

surface-water stations in the upper Illinois River Basin, April 1987 through August 1990 Continued

Constituent

Total 

nitrogen

Dissolved 

nitrite 

plus 

nitrate 

nitrogen

Total 

ammonia 

nitrogen

Total 

organic 

nitrogen

Total 

phosphorus

Fox River at Algonquin, III. (89)

Total rs

nitrogen n

Dissolved rs

nitrite + nitrate n

Dissolved rs

ammonia n

Total organic rs

nitrogen n

Total rs

phosphorus n

Discharge rs

n

Temperature, rs

water n

Specific rs

conductance n

Suspended rs

sediment n

Chlorophyll-a, rs

phytoplankton n

1.0000

119

HreSop

35

.3024

35

-.1171

113

-.2084

119

.0684

118

-.4501

119

.2917

117

0

1

1.0000

113

.3256

113

E~Myf*

35 '"

'..' 7051

108

.4788

113

KS>?£§!?t 39"

.3556

83

-.4480

41

£-5529

30

1.0000

113

-.1913

35

-.0576

108

-.0014

113

-.4226

59

.3173

83

-.4867

41

-.4245

32

1.0000

122*.&

te *';&)4$ 122

-.3114

121

12V

-.4026

120

0

_

1

1.0000

202

-.3397

200

" ' '^6?55;'l

isb

-.2886

171

.3271

36

.3599

28

Fox River at Dayton, III. (99)

Total rs

nitrogen n

Dissolved rs

nitrite + nitrate n

Dissolved rs

ammonia n

Total organic rs

nitrogen n

Total rs

phosphorus n

Discharge rs

n

Temperature, rs

water n

Specific rs

conductance n

Suspended rs

sediment n

Chlorophyll-0, rs

phytoplankton n

1.0000

117

EX $352

32

.3385

32

-.0591

110

-.1836

117

£3905

117

-.3687

116

-.0574

115

0

_

2

1.0000

86

.3882

85

£' 7546" 34'

§ -3301

80

85"****

I-J7569

55

.2554

84

-.2777

39 '' -'6593*

"34 "

1.0000

85

-.4848

34

-.0079

80

.2369

85

" ^0243

55

.3103

83

-.2606

39

-4735

34

1.0000

120

.3080

120

-.1521

120

HPSyW

T18

-.3939

118

1

1

3

1.0000

179

-.1659

178

.3055

150

-.1046

174

-.1067

34

.1147

31

30 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
D> 

I

Table 12. Statistical summary of physical properties and nutrient concentrations from surface-water samples collected during the low-flow synoptic survey in the

upper Illinois River Basin, July 26 through August 13, 1988[Data less than the detection level were set to the detection level. u,S/cm, microsiemen per centimeter at 25° Celsius; ft3/s, cubic foot per second; mm, millimeters; <, less than or equal to]

Constituent name

Temperature, water (°C)

Specific conductance (jiS/cm)

pH (standard units)

Streamflow (ft3/s)

Dissolved oxygenTotal nitrogen, as N2Dissolved nitrite, as N

Dissolved orthophosphorus, as PDissolved nitrite plus nitrate, as NDissolved ammonia, as N

Total phosphorus, as P

Dissolved phosphorus, as P

Total kjeldahl nitrogen, as N

Dissolved kjeldahl nitrogen, as N

Total organic carbon

Chlorophyli-a, phytoplanktonSuspended sedimentPercent suspended sediment < 0.063mm

Number of 

observations

59

595864

58

606161

60

6164646261

60

5958

58

Percentile1 (milligrams per liter unless otherwise noted)

Minimum

18.0

485

6.6

0

1.6

.30

.01

.01

.10.01.01.01.20.20

1.0

.60

7

15

10

21.82

559

7.29

.66

3.2

.65.01

.01.10

.02

.07

.02.40

.22

4.81

2.20

15

55

25

23.79

648

7.508.855.2

1.10

.01

.03.10.04

.14.05.70

.40

6.70

4.90

2276

50

25.43

714

7.71

56.50

6.73.24

.03

.09

1.06

.10

.29

.14

1.40

.90

8.20

23

45

86

75

27.26

950

8.04

315.50

9.15.70

.09

.35

3.80

.23.80.60

2.00

1.35

11.00

526995

90

28.46

1,200

8.56

3,920

11.110.26

.19

1.18

8.11

.73

1.50

1.35

2.84

1.94

16.90

130123

98

Maximum

30.0

1,816

9.5

4,370

1616.2

.40

2.60

15.0

4.20

4.00

3.80

5.40

5.00

24

390

499

100

'Percentage of samples with values less than or equal to the value shown.

2Total nitrogen calculated as the sum of dissolved nitrite plus nitrate and total kjeldahl nitrogen.
p£

es "-=1 °d£

gfs

20

O1

.0

o;

53

HCC

u.52 CHcc

zz010

&8£Et

«z j 

°u,S ss^

oil

S5

20

Si

10

o£'

- 5

°< o*1

w

Uo. 

ZM 00-

ox

o.

O -«"

og<t §1?

LAND USE

LAND USE

EXPLANATION

o Data yalue(s) exceeding upper 

quartile plus 3 times the 

interquartile range

* Data value(s) exceeding upper 

quartile plus 1.5 times the 

interquartile range but less 

than upper quartile range plus 

3 times the interquartile range

~- Largest data value less than or 

equal to the upper quartile plus 

1.5 times the interquartile range

_

- Upper quartile

(75th percentile)

 Median 

(50th percentile)

~- Lower quartile 

(25th percentile)

INTERQUARTILE 

RANGE

1

 \

^Smallest data value greater than or 

equal to the lower quartile minus 

1.5 times the interquartile range

Maximum detection limit

Figure 7. Distribution of nutrient concentrations, by land-use classification, in surface-water samples collected at the 

low-flow synoptic-survey sites in the upper Illinois River Basin, July 26 through August 13, 1988.

32 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria In Surface Water, April 1987 Through August 1990
89" 88° 67" 86"

43'-n L-iV r

EXPLANATION

BASIN BOUNDARY

CONCENTRATION OF TOTAL 

NITROGEN. IN MILLIGRAMS 

PER LITER

Greater than 10

Base from US Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° end 45°, central meridien -89°

40 MILES

20 40 KILOMETERS

Figure 8. Spatial distribution of total nitrogen concentrations at the low-flow synoptic-survey surface-water 

sites in the upper Illinois River Basin, July 26 through August 13,1988.

Nutrients, Dissolved Oxygen, snd Fecal-Indicator Bacteria 33
43"

BASIN BOUNDARY

CONCENTRATION OF DISSOLVED 

NITRITE PLUS NITRATE, 

IN MILLIGRAMS PER LITER 

Greater than 1O

5 to 1O 

1 to 4.99 

Less than 1

LAKE MICHIGAN 

Chicago Sanitary and

Base from US Geological Survey

1:100,000 Digital Line Graphs

Alters Equal-Area Conic projection

Standard parallels 33° and 45°, central meridian -89°

40 MILES

2O 40 KILOMETERS

Figure 9. Spatial distribution of dissolved nitrite plus nitrate concentrations at the low-flow synoptic-survey 

surface-water sites in the upper Illinois River Basin, July 26 through August 13,1988.

34 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
EXPLANATION

 BASIN BOUNDARY

CONCENTRATION OF DISSOLVED 

AMMONIA NITROGEN. IN 

MILLIGRAMS PER LITER 

A Greater than 1.0

0.50 to 1.0 

0.10 to 0.49 

Less than 0.10

LAKE MICHIGAN

Chicago Sanitary and r-"'~ Canal

MICHIGAN 

' ' INDIANA -

Calumet-Sag 

Channel

Base from US Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° and 45°. centre! meridian -89°

40 MILES

20 40 KILOMETERS

Figure 10. Spatial distribution of dissolved ammonia nitrogen concentrations at the low-flow synoptic-survey 

surface-water sites in the upper Illinois River Basin, July 26 through August 13,1988.

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 35
86°

EXPLANATION

BASIN BOUNDARY

CONCENTRATION OF TOTAL 

ORGANIC NITROGEN. IN 

MILLIGRAMS PER LITER

Greater than 1O

5 to 1O 

1 to 4.99 

Lees than 1

\/WISCONSIN

LAKE MICHIGAN

, : ~'~^< -v S

..-''/; ^ /-'< ^

; f / /Xv. \

Base from US Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° and 45°, central meridian -89°

40 MILES

0 2O 4O KILOMETERS

s

Figure 11 . Spatial distribution of total organic nitrogen concentrations at the low-flow synoptic-survey surfacewater sites in the upper Illinois River Basin, July 26 through August 13,1988.

36 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through Auguat 1990
43° -

EXPLANATION

BASIN BOUNDARY 

CONCENTRATION OF TOTAL

PHOSPHORUS IN MILLIGRAMS

PER LITER

Greater than 1.00

O.500 to 1.00 

O.05O to O.499 

I/WISCONSIN Less than O.O50

^"ILLINOIS j

LAKE MICHIGAN

Chicago Sanitary ana 

Ship Canal

-

'"iNDJANA ~

Calumet-Sag 

.. -v Channel

Base from US Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° and 45°, central meridian -89°

40 MILES

2O 40 KILOMETERS

Figure 12. Spatial distribution of total phosphorus concentrations at the low-flow synoptic-survey surfacewater sites in the upper Illinois River Basin, July 26 through August 13,1988.

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 37
Loads also were computed for samples collected 

during the low-flow synoptic survey. These loads 

were computed from single measurements of concentration and streamflow. The calculation used to compute the instantaneous constituent load was

L = C*Q*K,

where L = constituent load, in tons per day;

C = measured constituent concentration, in

milligrams per liter; 

Q = instantaneous discharge, in cubic feet per

second; and 

K = a conversion factor of 0.002714 to convert

units to tons per day.

The estimated loads at the 1988 low-flow synoptic 

sites for the five indicator nutrient forms are given in 

table 13. The spatial distribution of loads for several 

selected nutrient forms are shown in figures 13-17.

Temporal variability in water chemistry can be 

described in different ways, including abrupt changes, 

long-term changes, diurnal variations, and seasonal 

changes. Because the NAWQA program provided 

only 3 years of data, trend analyses on these data alone 

would have been of little benefit. Consequently, data 

collected monthly at the fixed stations was combined 

with historical (1978-86) data collected through the 

IEPA monitoring program and long-term trend analyses were done using the combined 1978-90 data set. 

Water-quality data were not collected at Des Plaines 

River at Riverside or CSSC at Romeoville prior to 

the NAWQA program, and the trends for these two 

stations represent trends from April 1987 through 

September 1990.

Trends in nutrient concentrations and loads 

were determined using the seasonal Kendall trend 

test (Hirsch and others, 1982). Trends in measured 

constituent concentrations were determined first. 

Regressions between concentrations and streamflow 

were then determined for each constituent. The 

regression was considered statistically significant if 

the p-value was less than or equal to 0.10 and the 

coefficient of determination, R2, was greater than or 

equal to 0.2. If the regressions were significant, the 

regression equations were used to factor out the effects 

of streamflow on concentration and flow-adjusted 

concentrations (residuals) were calculated. Trend 

tests were then done on the residuals. The results of 

the trend analyses are given in table 14.

Changes in climatic season often promulgate 

changes in stream-water quality. The effects of

climatic season on nutrient concentrations can be 

substantially different among land-use areas and 

nutrient sources. Boxplots were used to determine 

whether there were substantial differences in nutrient 

concentrations among the four climatic seasons. 

The four seasons used were defined as groups of 

three consecutive months. Winter included December, January, and February; spring included March, 

April, and May; summer was defined as June, July, 

and August; and fall included September, October, 

and November. Several notable instances of seasonal variation in nutrient concentrations at the fixed 

stations are shown in figure 18.

Summer thunderstorms in the upper Illinois 

River Basin can produce large amounts of precipitation in short periods, resulting in runoff with large 

constituent concentrations. Data from the 1990 

storm synoptic survey were used to examine 

relations between streamflow and nitrite plus nitrate 

concentrations in an agricultural basin during storms. 

Correlations between NC>2 + NC>3 concentrations and 

streamflow were made for six stations where 10 or 

more samples were collected. The results of these 

correlation analyses are given in table 15.

Because streamflow affects in-stream nutrient 

concentrations and the transport of chemical constituents in a stream system, a brief discussion of the 

streamflow characteristics at the eight fixed stations 

during 1987-90 follows. An additional discussion 

of the hydrology of the upper Illinois River Basin is 

provided in Mades (1987).

Boxplots of streamflow at the eight fixed stations for 1987-90 are presented in figure 19. The 

symmetry of the boxes shows that the distribution of 

the streamflow data was not markedly different from a 

normal distribution at the fixed stations. Greater than 

99 percent of the entire upper Illinois River Basin 

drainage area is represented by two stations Fox 

River at Dayton and Illinois River at Marseilles. The 

cumulative streamflows from these two stations are an 

approximation of the total discharge from the upper 

Illinois River Basin. Using these two stations to represent the basin, the median streamflow for the upper 

Illinois River Basin for 1987-90 was about 8,230 ft3/s, 

and the mean annual streamflow was approximately 

11,300 ft3/s. Approximately 50 percent of the total 

upper Illinois River Basin streamflow was from the 

Des Plaines River Basin; the Fox and Kankakee River 

Basins contributed approximately 15 and 35 percent, 

respectively.

38 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
Table 13. Estimated nutrient loads during low flow at the synoptic-survey surface-water sites in the upper Illinois

River Basin, July 26 through August 13,1988

[Loads are expressed as tons per day. Load estimates of 0.00 denote negligible load because of low streamflow, small concentrations, or both]

Map 

reference 

number1

1

7

13

14

18

21

22

23

26

28

29

30

31

32

33

34

37

38

40

41

42

44

45

47

48

51

52

54

55

58

61

62

67

69

70

71

72

73

74

75

76

77

78

79

80

Total 

nitrogen

0.06

.26

.02

(2)

.00

.00

.00

.13

.00

.05

1.2

.00

.39

.00

4.1

1.18

.21

2.22

2.90

.37

6.4

.64

.47

9.0

63

.50

16.99

13.98

48.24

59.55

60.60

.42

3.49

1.89

46.56

49.81

.00

.00

.01

47.06

48.62

.00

.05

1.35

.15

Dissolved 

nitrite 

plus 

nitrate 

nitrogen

0.04

.08

.01

(2)

.00

.00

.00

.01

.00

.00

.09

.00

.11

.00

3.52

1.28

.03

1.94

2.09

.34

3.06

.51

.38

1.74

2.65

.30

9.59

8.52

7.41

2.84

1.79

.38

3.03

1.40

2.48

.56

.00

.00

.00

.99

33.20

.00

.02

.40

.08

Dissolved 

ammonia 

nitrogen

0.00

.06

.00

.04

.00

.00

.00

.00

.00

.00

.44

.00

.07

.00

.04

.01

.01

.01

.38

.00

.24

.00

.01

5.65

2.03

.05

3.28

.67

.08

7.94

6.58

.00

.03

.00

2.38

.87

.00

.00

.00

1.72

1.18

.00

.00

.00

.00

Total 

organic 

nitrogen

0.01

.11

.00

.43

.00

.00

.00

.11

.00

.04

.64

.00

.20

.00

.53

.28

.16

.27

.42

.02

3.08

.12

.08

1.61

8.74

.14

4.11

4.78

.74

8.77

2.22

.04

.41

.48

1.69

11.37

.00

.00

.01

4.35

14.23

.00

.02

.94

.06

Total 

phosphorus

0.00

.15

.00

.06

.00

.00

.00

.02

.00

.00

.31

.00

.20

.00

.56

.21

.37

.49

.31

.06

1.21

.08

.06

.67

2.03

.28

3.28

3.27

4.60

6.47

5.43

.04

.42

.28

4.98

4.33

.00

.00

.00

6.42

4.74

.00

.00

.06

.00

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 39
Table 13. Estimated nutrient loads during low flow at the synoptic-survey surface-water sites in the upper Illinois 

River Basin, July 26 through August 13,1988 Continued

Map 

reference 

number1

82

86

87

89

90

91

92

95

98

99

100

101

102

103

Total 

nitrogen

0.07

.21

.90

1.79

.00

1.92

1.82

.24

.02

.47

.03

.05

.25

.06

Dissolved 

nitrite 

pius 

nitrate 

nitrogen

0.02

.10

.02

.05

.00

.27

.07

.20

.00

.01

.00

.01

.17

.04

Dissolved 

ammonia 

nitrogen

0.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.01

.01

.00

Total 

organic 

nitrogen

0.04

.11

.87

1.73

.00

1.64

1.74

.03

.01

.45

.02

.02

.06

.01

Totai 

phosphorus

0.00

.01

.05

.13

.00

.19

.28

.00

.00

.05

.00

.00

.02

.00

'See table 3 and figure 4.

2Nitrite plus nitrate concentration not determined, load calculation not possible.

During high-flow periods, the relative percentages of total streamflow from the major river basins in 

the upper Illinois River Basin were similar to the percentages during average flow conditions. At low 

flows, however, the Des Plaines River contributed a 

much larger percentage of the total upper Illinois 

River Basin streamflow. During the 1988 low-flow 

synoptic survey, the Des Plaines River Basin contributed about 97 percent of the total streamflow in the 

upper Illinois River Basin. The factors affecting this 

are (1) most of the point sources of return flow in the 

upper Illinois River Basin are in the Des Plaines River 

Basin, and (2) the water diverted from Lake Michigan 

helps to maintain streamflow in the CSSC (a tributary 

to the Des Plaines River) during dry periods.

Streamflow characteristics in the different river 

basins of the upper Illinois River Basin can be 

described by streamflow data from the eight fixed 

stations. Row-duration curves for the fixed stations 

are shown in figure 20. The curves for the period of 

record show the historical streamflow characteristics 

at each station, and the curves for 1987-90 depict the 

streamflow characteristics during the NAWQA fixedstation sampling period. The differences between the

curves show the effects of changes in the drainage 

areas, land use, sources of streamflow, or channel 

modification in recent decades.

The boxplots of streamflow at the fixed stations 

(fig. 19) show that the variability of streamflow 

increased as the quantity of streamflow increased. 

The Iroquois River had a large number of high streamflows. Although streamflow in the CSSC was larger, 

the variability of streamflow in the CSSC was similar 

to that for the stations in the Kankakee and Fox River 

Basins. The relatively small variability in the CSSC 

is likely a result of the comparatively consistent inputs 

from point sources and Lake Michigan diversions that 

comprise a large part of the total streamflow in the 

CSSC. Because streamflow directly affects nutrient 

nonpoint-source input and in-stream concentrations 

and loads, understanding the variability in streamflow 

at the fixed stations will aid in understanding the variability of nutrient concentrations and loads.

Significant variations in climatic conditions 

occurred during 1987-90 (National Oceanic and 

Atmospheric Administration, 1987-90) (fig. 21). 

Mean annual precipitation in northeastern Illinois 

in 1987 was about 5 in. more than the long-term

40 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
43° -

42" -

41° -

S ^ ' .VX

\ftVISCONSIN^-7 

?" II i minic \ /<" ~

LAKE MICHIGAN

Zl_ ~-\fl {.MICHIGAN, 

 ' 'INDIANA

Base from US Geological Survey

1:100.000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° and 45°, central meridian -89°

40 MILES

2O 40 KILOMETERS

Figure 13. Spatial distribution of total nitrogen loads at the low-flow synoptic-survey surface-water sites in the 

upper Illinois River Basin, July 26 through August 13,1988.

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 41
EXPLANATION

BASIN BOUNDARY

LOAD OF DISSOLVED NITRITE 

PLUS NITRATE NITROGEN. 

IN TONS PER DAY 

Greater than 10

1.0 to 10 

0.1 to 0.9 

Less than 0.1

LAKE MICHIGAN

MICHIGAN, _/

Base from US Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° and 45°, central meridian -89°

40 MILES

20 40 KILOMETERS

Figure 14. Spatial distribution of dissolved nitrite plus nitrate nitrogen loads at the low-flow synoptic-survey 

surface-water sites in the upper Illinois River Basin, July 26 through August 13,1988.

42 Nutrients, Disaolved Oxygen, and Fecal-Indicator Bacteria In Surface Water, April 1987 Through August 1990
EXPLANATION

BASIN BOUNDARY

LOAD OF DISSOLVED AMMONIA 

NITROGEN, IN TONS PER DAY

Greater than 5.0

1.0 to 5.0 

0.1 to 0.9 

Less than 0.1

!/WISCONSIN 

f"" I ILLINOIS j

LAKE MICHIGAN

Chicago Sanitary and 

Ship Canal

Calumet-Sag 

Channel

\---v IV

r ^ v- * v ?^-»

Base from US. Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° and 45°, central meridian -89

40 MILES

40 KILOMETERS

Figure 15. Spatial distribution of dissolved ammonia nitrogen loads at the low-flow synoptic-survey surfacewater sites in the upper Illinois River Basin, July 26 through August 13,1988.

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 43
43'

LOAD OF TOTAL ORGANIC 

NITROGEN, IN TONS PER DAY 

Greater than 5.O

1.0 to 5.0 

0.1 to 0.9 

Less than 0.1

Base from US Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° and 45°, central meridian -89°

4O MILES

20 4O KILOMETERS

Figure 16. Spatial distribution of total organic nitrogen loads at the low-flow synoptic-survey surface-water 

sites in the upper Illinois River Basin, July 26 through August 13,1988.

44 Nutrients, Dissolved Oxygan, and Fecal-Indicator Bacteria In Surface Water, April 1987 Through August 1990
EXPLANATION

BASIN BOUNDARY

LOAD OF TOTAL PHOSPHORUS 

IN TONS PER DAY

Greater than 5.O

1.0 to 5.0 

0.1 to 0.9 

Less then 0.1

Base from US. Geological Survey

1:100.000 Digital Line Graphs

Albers Equal-Area Conic projection

Standerd parollels 33° end 45°, central meridien -89°

40 MILES

2O 40 KILOMETERS

Figure 17. Spatial distribution of total phosphorus loads at the low-flow synoptic-survey surface-water sites in 

the upper Illinois River Basin, July 26 through August 13, 1988.

Nutrients, Diesolved Oxygen, and Fecal-Indicator Bacteria 45
z

f

2

ID 

V)

Table 14. Results of the seasonal Kendall trend test for nutrient concentrations at the eight fixed surface-water stations in the upper Illinois River Basin,

January 1978 through August 1990

[Underlining indicates a trend with a p-value less than or equal to 0.1 or a regression with a correlation coefficient greater than or equal to 0.2 and a p-value less than or equal to 0.1;

-, a trend with a p-value greater than 0.2 or a regression with a correlation coefficient less than 0.2 and a p-value greater than 0.1; n.a., regression and flow-adjustment not applicable to discharge, no flow-adjustment done when the regression analysis was not statistically significant]

Concentration

Map reference 

number

14 

28 340 

355 

69 76 89 99

14 

28 

340 355 

69 

76 

89 

99

14 

28 

340 355 

69 76 89 99

Number of 

observations

132 

130 

94 

39 

132 

127 

128 

134

107 

47 

37 

37 

43 

111 

105 

104

41 

41 

40 40 

41 

86 

40 

39

Level of 

significance (p-value)

1

.8724 

.3395 

.5232 

.2515 .2358 

.0057

.0297

1 

.4350 .0865.4705 

.0204

.3452 .0067

.4767

.2751 .2286 .0608.0007.0302.0088.4497 

1

Units 

per 

year 2

-37.2

-63.3

Siope

Percent of 

median 

concentration 

per year

Regression analyses

Coefficient 

of determination (R*)

Discharge

n.a. 

n.a. 

n.a. 

n.a. 

n.a. 

n.a. 

-4.5 n.a.-3.6 n.a.

Total nitrogen

0.3244

.600.469

.088.625

.842

.650.192

~

9.0

5.7

2.9

Dissolved nitrite

14

26

9.0

4.8

.5825.6292

.1961 

.3160

.1432 .0038 

.2174

plus nitrate nitrogen 

.8132.6518.6405.2130

.4537

.2017.3049.4027

Level of 

significance (p-value)

n.a. n.a. n.a. 

n.a. 

n.a. n.a. n.a. n.a.

<0.0001

<.0001

<.0001

<.0001 

<.0001<.0001 

.056 

<.0001

<.0001

<.0001

<.0001

<.0001

<.0001<.0001<.0001

<.0001

Flow-adjusted concentration

Level of 

significance (p-value)

n.a. n.a. n.a. 

n.a. 

n.a. 

n.a. 

n.a. 

n.a.

0.7551 

.0790.2531 

n.a. 

.0111

n.a. 

n.a. 

.1088

1 

1 

.0336.0014

.0039

.0049.0049.4347

Units year2

n.a. 

n.a. 

n.a. n.a. n.a. n.a. n.a. 

n.a.

0.356

n.a. 

.454

n.a. 

n.a.

.311

.568.458.193

.193~

Siope

Percent of 

median 

concentration 

per year

n.a. n.a. 

n.a. n.a. n.a. n.a. 

n.a. 

n.a.

4.2

n.a. 

5.5

n.a. n.a.

7.0

20.0

8.05.0

28
Table 14. Results of the seasonal Kendall trend test for nutrient concentrations at the eight fixed surface-water stations in 

January 1978 through August 1990 Continued

Concentration Regression analyses

Slope

Map 

reference 

number1

14 

28 

340 

355 

69 

76 

89 

99

14 

28 

340 

355 

69 

76 

89 

99

14 

28 

340 

355 

69 

76 

89 

99

Number of 

observations

60 

34 

35 

37 

32 

108 

107 

103

125 

123 

37 

38 

122 

110 

125 

125

114 

98 

40 

40 

85 

126 

122 

125

Level of 

significance 

(p-vaiue)

.6814 

.3348 

1 

.1123 

1 

.4400 

.7857 

.7746

<.0001

 c.OOOl

.7721 

.0097

.5627 

.0003

.0719

.1978

.7398 

.3352 

.0608

.7077 

.9331 

 c.OOOl

.1595 

.0105

Units

Per 2 

year'

Percent of Coefficient 

median of deterconcentratlon mlnatlon 

per year (R2)

Total organic nitrogen

.0243 

.2236

-.20 

.006

.002

-.574

-.061

.005

.001 

.061

-.013

-.004 

-.008

-18

~

.1221 

.2914

.3310

.0573 

.1589 

.1934

Total ammonia nitrogen

35.7 .0220

2.5

-29

-8.6

5.0

2.9 

Total phosphorus

7.1

-3.3

-2.6

-3.2

.0209 

.0676

.0676 

.0303

.0095 

.3221

.5721

.2599

.3600

.2206

.0740 

.1253

Level of 

significance 

(p-value)

<.0001 

<.0001

 cOOOl 

<.0001

<.0001

<.0001 

<.0001 

<.0001

<.0001

.0010 

<.0001

 cOOOl 

<.0001

.0070 

<.0001

<.0001

<.0001

<.0001

 cOOOl

<.0001 

<.0001

Leve

signifi

(p-va

n.a

.12

n.a

.03

.77

n.a

n.a

n.a

n.a

n.a

n.a

n.a

n.a

n.a

n.a

n.a

n.a

n.a

.00

n.

n.

'See table 3 and figure 4.

2Units are cubic feet per second for discharge, milligrams per liter for nutrient concentrations.

'Trends at these stalions are from 1987-90.
2U

o<

"§ 

M

15

"-To-ltc =Jm ZSH

gz-1 10

<KSz'SH h-fiO2 S

UX .

0° 5

85

0

F TOTAL 

IGRAMS

Ro 

ojc

>iH! 8

F* 13

5 C

Cjg-UI 6 

Hfi 0-

U X

z« 4 si

2

8 

_j 

^zo: 6~"J 

i-ast 6

U.UI-1

Ogee Ou

ZOCo.

P5» 4

5 a s<< 1-5=

20°

US

o

0

Q Z~ 8

u£ 

38g 

8SEt

Mg-1 6

Ott

u-t-a. o<

KM

ZtS 4

2z<

5 cog fid

Z°- 2

SL S

ztz

8t 3» n

i f i 

Map reference number 28 

" 11

11 9

'

.

-

.

6

: i :

-

.

i

 i i '

g

- ^ r-i15

*

I

Map reference number 55 

Map reference number 55

H 8

*

9 15

o

_ i 

i

T 

I I

I I I

Map reference number 55 

9 

13 8

, | 17

-

-

'4

o< i-jc

"-§°dS IIs

5 a

OC7°U'

zl0-

|i §t

o z

12

10

8 -

6 -

Map reference number 76 

18

WINTER SPRING SUMMER 

SEASON

EXPLANATION

8 Number of observations

o Data value(s) exceeding upper 

quartile plus 3 times the 

interquartile range

* Data value(s) exceeding upper 

quartile plus 1.5 times the 

interquartile range but less 

than upper quartile range plus 

3 times the interquartile range

--Largest data value less than or 

equal to the upper quartile plus 

1.5 times the interquartile range

FALL

Upper quartile

(75th percentile)

Median 

(50th percentile)

Lower quartile 

(25th percentile)

I INTERQUARTILE 

RANGE

I

Smallest data value greater than or 

equal to the lower quartile minus 

1.5 times the interquartile range

 Maximum detection limit

MAP

REFERENCE 

NUMBER STATION NAME

28 Iroquois River near Chebanse, III. 

55 Chicago Sanitary and Ship Canal at

Romeoville, III. 

76 Illinois River at Marseilles, III.

WINTER SPRING SUMMER FALL 

SEASON

Figure 18. Distribution of nutrient concentrations, by season, at selected fixed surface-water stations in the upper 

Illinois River Basin, April 1987 through August 1990.

48 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria In Surface Water, April 1987 Through August 1990
Table 15. Results of the Spearman rank correlation test for streamflow and total nitrite plus nitrate concentrations 

during the 1990 storm synoptic survey at six surface-water sites in the upper Illinois River Basin 

[<, less than]

Station name (map reference number1 )

Iroquois River at Rosebud, Ind. (15)

Iroquois River at Rensselaer, Ind. (16)

Iroquois River near Foresman, Ind. (19)

Iroquois River at Iroquois, Dl. (20)

Sugar Creek at Milford, 111. (22)

Iroquois River near Chebanse, 111. (28)

Number 

of 

samples

12

13

20

25

45

2 102

Correlation 

coefficient

0.9702

.9036

.8476

.6071

-.1282

-.3074

Level of 

significance

<0.0001

<.0001

<.0001

.0006

.2007

.0008

'See table 3 and figure 4.

Correlation done using dissolved nitrite plus nitrate concentrations.

(1951-80) average of 35.37 in. In 1988 and 1989, 

the annual precipitation totals were over 6 in. less than 

long-term average. Total annual precipitation in 

1990 was 10.65 in. more than the long-term average. 

Mean annual temperatures also fluctuated somewhat 

but were within a few degrees of normal each year.

Nutrient Conditions in the Upper Illinois River 

Basin

The upper Illinois River Basin is a large and 

diverse area with numerous factors that affect instream nutrient conditions. These factors interact 

with each other and the processes change spatially 

and temporally. Nutrient concentrations in the 

upper Illinois River Basin generally were larger 

than concentrations typically found in natural waters 

(McNeely and others, 1979; Briggs and Ficke, 1978). 

Large nutrient concentrations were generally found in 

the urban areas of the upper Illinois River Basin the 

Des Plaines River Basin, in particular. Point-source 

inputs often increased nutrient concentrations of 

receiving streams.

Median concentrations of total nitrogen at the 

eight fixed stations ranged from 2.20 mg/L at Kankakee River at Momence to 9.78 mg/L at Iroquois River 

near Chebanse (fig. 6). Total nitrogen concentrations 

in the Des Plaines River Basin ranged from 6.50 to 

13.85 mg/L and generally were larger than in the rest 

of the upper Illinois River Basin, except at Iroquois 

River near Chebanse.

Total nitrogen and dissolved nitrite plus nitrate 

concentrations typically were smallest at Kankakee 

River at Momence and largest at Iroquois River near 

Chebanse (fig. 6). These two stations represent areas

of comparable size and agricultural land use. Fertilizer application rates between the two basins are not 

substantially different. Significant differences in soil 

types, however, are found. Soils in the Kankakee 

River Basin are predominantly sand and gravel; 

whereas till, clay, and silt are found in most of the 

Iroquois River Basin. The sand and gravel in the 

Kankakee River Basin results in adequate field drainage through natural infiltration and percolation to 

drainage ditches. Because of the coarse soils in the 

Kankakee River Basin, precipitation is likely to percolate to ground water or to a stream. Conversely, precipitation in the Iroquois River Basin is more apt to be 

conveyed to the stream as surface runoff or through 

tile-drainage systems after limited percolation through 

the soil. Nitrogen transformation and consumption 

processes reduce concentrations as water passes 

through soil. Field-tile systems, such as those used 

throughout the Iroquois River Basin, provide rapid 

conveyance of water to streams after limited percolation, effectively reducing the transformation and consumption of nitrogen in soils and allowing larger 

concentrations and loads to reach the streams.

Most of the nitrogen in upper Illinois River 

Basin streams is in the form of nitrate. Median 

concentrations of dissolved NC«2 + NC>3 in the upper 

Illinois River Basin ranged from 0.22 mg/L at Fox 

River at Algonquin to 9.80 mg/L at Iroquois River 

near Chebanse (fig. 6). The spatial distribution of 

dissolved NO2 + NC«3 concentrations was similar to 

the distribution for total nitrogen, except at CSSC at 

Romeoville, where ammonium made up a large part 

of the total nitrogen concentration, and at Fox River at 

Algonquin, where organic nitrogen was predominant.

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 49
22,500 

§ 20,000

8

W 17,500

cc

LU

°- 15,000

UJ 

"- 12,500 

O 

ffi

3 10,000

z

>- 7,500

3

 g 5,000

Si

oc

H 2,500

(0

n

 ! , , ..,. , .-, _ . , , ...... , 

*

*

0

o 

o

8

8 

o

J 

!i o : :

0 t

o

" ° * PH "

c=j=] , ,,,1^ , l=p=l ' 

o Da

qu

in

* Dat

q

in

th

3 

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eq

1

Up

(75

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(50

Low

(25

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14 28 40 55 69 76

MAP REFERENCE NUMBER

89

MAP

REFERENCE 

NUMBER S

14 K

28 Ir

40 D

55 C

69 D

76 Il

89 F

99 F

Figure 19. Distributions of streamflow at the eight fixed surface-water stations in the upper Illinois River Basin, 1987-9
10,000

z

I 

o

3 

f

I

8

3 

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T 

I

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1,000

100

10,000

1,000

100

10

Kankakee River at Momence, III. 

(Map reference number 14)

1914-90

Des Plaines River at Riverside, III. 

(Map reference number 40)

1943-90

100,000

10,000

1,000

100

10

100,000

10,000

1,000

20

40 60 80 100 0 20 

PERCENTAGE OF TIME DISCHARGE WAS EQUALED OR 

EXPLANATION

1987-90

PERIOD OF RECORD-Years denoted

DENOTES FLOW DURATION AT TIME WATER-QUALITY 

SAMPLE WAS COLLECTED

Figure 20. Flow-duration curves at the eight fixed surface-water stations in the upper Illinois River Basin for the p

water years.
u:

ID g 

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- - 9- h c|

=8

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g Q.

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o 

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8.

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O 

Ul 

Ul

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oc 

o

o

Ul

o

Ul 1

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8.

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QNO03S d3d 133d 01800 Nl '30dVHOSIQ A1IVQ

0)

o O

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52 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
1987 1988 1989 1990

Figure 21. Averaged annual precipitation totals for precipitation monitoring sites in northeastern Illinois, 1987-90. 

[Data from National Oceanic and Atmospheric Administration, 1987-90]

Nutrients, Dissolved Oxygen, end Fecal-Indicator Bacteria 53
Concentrations of ammonia at the fixed stations 

ranged from less than 0.01 to 7.40 mg/L (fig. 6). 

Ammonia concentrations were largest at Des Plaines 

River at Riverside, CSSC at Romeoville, and Illinois 

River at Marseilles. These larger concentrations 

were likely due to urban land uses and wastewatertreatment-plant effluents. The concentrations at 

Illinois River at Marseilles are likely results of the 

elevated concentrations in the Des Plaines River 

Basin.

Median concentrations of total organic nitrogen 

in the upper Illinois River Basin ranged from 

0.87 mg/L at Kankakee River at Momence to 

1.76 mg/L at Fox River at Dayton (fig. 6). Organic 

nitrogen comprised a larger portion of the total nitrogen concentration in the Fox River than in the other 

major upper Illinois River Basin rivers (table 9). 

Numerous dams are found in the Fox River Basin, 

both on the Fox River and on tributary streams. 

Aquatic plant growth in the pools behind the dams 

might be a cause for the relatively large organic nitrogen concentrations in the Fox River. During the lowflow conditions of the 1988 synoptic survey, stations 

in the Fox River Basin did not have large organic 

nitrogen concentrations, but concentrations as large as 

14.2 mg/L were found in the Des Plaines River Basin 

(fig. IDMedian concentrations of total phosphorus at 

the fixed stations ranged from 0.06 to 0.84 mg/L 

(fig. 6). The spatial distribution of total phosphorus 

concentrations was similar to that for total nitrogen; 

the smallest concentrations were in streams in the 

Kankakee River Basin and the largest concentrations 

were in streams in the Des Plaines River Basin. 

Unlike nitrogen concentrations, however, phosphorus 

concentrations were not large at Iroquois River near 

Chebanse. If tile-drainage systems in the Iroquois 

River Basin provide rapid conveyance of water and 

fertilizer components to streams (as evidenced by 

large NO2 + NC>3 concentrations), correspondingly 

large phosphorus concentrations also might be 

expected because phosphorus also is commonly 

applied to agricultural fields. Large phosphorus 

concentrations, however, were not detected in the 

Iroquois River Basin. Phosphorus adsorption to sediment particles might be one reason why phosphorus 

concentrations in streams in the Iroquois River Basin 

were not large. Phosphorus commonly associates 

with sediment particles and, therefore, is not mobile 

in soils (Hem, 1985; Brown and Johnson, 1993).

Similar adsorption processes take place with in-stream 

sediments and bottom material. Total phosphorus 

and suspended-sediment concentrations were correlated (rho = 0.5535) (table 11) at Iroquois River near 

Chebanse. This correlation was the only significant 

correlation between total phosphorus and suspended 

sediment at any of the fixed stations. Small sediment 

particles have more surface area per unit mass 

(Horowitz, 1991) and more potential sites for phosphorus adsorption. About 97 percent of the suspended sediment at Iroquois River near Chebanse was 

smaller than 63 |lm, the smallest particle size classified as sand. The median suspended-sediment concentration at Iroquois River near Chebanse was 

81 mg/L; almost twice as large as median concentrations at other fixed stations in agricultural areas and 

up to six times the concentration at fixed stations in 

urban areas. The relatively large suspended-sediment concentrations, compared to concentrations at 

other upper Illinois River Basin areas, indicate likely 

substantial adsorption of phosphorus to sediment in 

the Iroquois River Basin and the fine-sized sediments 

in the Iroquois River Basin.

Spatial distributions of nutrient concentrations 

might be considerably different during contrasting 

hydrologic or climatic conditions. The spatial distributions of nutrient concentrations in stream water 

samples collected during the 1988 synoptic survey are 

summarized in figures 8-17. Low-flow nutrient concentrations, in general, were largest in streams in the 

Des Plaines River Basin and smallest in streams in the 

Kankakee River Basin. Many of the largest concentrations were found at enriched sites downstream from 

point sources and often on small tributary streams. 

Large concentrations from point sources or smaller 

streams generally were attenuated in larger streams in 

a relatively short distance downstream. Elevated 

phosphorus concentrations, however, were found to 

persist in the stream system for a longer time and a 

greater distance than concentrations of nitrogen forms; 

possibly because of the association with particulate 

matter.

Total nitrogen concentrations and streamflow 

were found to be correlated at most of the unregulated 

fixed stations (table 11). The streamflow in the 

CSSC is regulated and is composed mostly of water 

diverted from Lake Michigan or of return flows, many 

of which have been routed through wastewatertreatment plants. Streamflow at Illinois River at 

Marseilles, Fox River at Algonquin, and Fox River at

54 Nutrients, Dissolved Oxygen, and FecaMndicator Bacteria in Surface Water, April 1987 Through August 1990
Dayton is affected, to some extent, by dam operations. 

At Algonquin, organic nitrogen comprises a large part 

of the total nitrogen concentration. Organic nitrogen 

is derived primarily from plant and animal matter, and 

dilution of these sources typically occurs during highflow periods. Many physical, hydrologic, biological, 

and chemical processes affect the correlations between 

streamflow and nitrogen concentrations, and these 

processes are different at each station. Positive correlations between streamflow and nitrogen concentrations were indicated at stations in predominantly 

agricultural basins and negative correlations were 

indicated for stations in urban areas, indicating that 

nitrogen is conveyed to streams in agricultural areas 

during storms, whereas point sources are major 

contributors of nitrogen in urban areas. Because 

point-source inputs generally are not affected by 

hydrologic conditions, they have a pronounced effect 

on in-stream concentrations during low-flow periods 

when nonpoint-source inputs are typically reduced. 

Nutrient concentrations at fixed stations in agricultural 

areas increased during high-flow periods but generally 

did not surpass concentrations at stations in urban 

areas.

Phosphorus concentrations were correlated with 

streamflow at five of the fixed stations; the only positive correlation was at Iroquois River near Chebanse.

The positive correlation between phosphorus and 

streamflow in the Iroquois River is probably a result 

of the large concentrations and transport of suspended 

paniculate matter and associated phosphorus during 

high-flow periods. Wastewater-treatment-plant 

effluents, the major source of phosphorus in urban 

locations, typically are diluted during high-flow 

periods. Negative correlations between phosphorus 

and streamflow were found at the three stations in the 

urban areas and the two mixed land-use stations.

Approximately 247,000 tons of nitrogen and 

94,000 tons of phosphorus enter streams in the upper 

Illinois River Basin annually. A summary of the 

estimated contributions of nutrients from the major 

sources in the upper Illinois River Basin is given in 

table 16. These estimates are compiled and extrapolated from the many different data sources referenced 

in a previous section and are meant only to provide a 

gross approximation of the nutrient input to the upper 

Illinois River Basin and to give an indication of the 

relative contributions from the different sources. 

Only 74,730 tons of nitrogen and 3,850 tons of 

phosphorus are exported from the upper Illinois 

River Basin each year via the Illinois River. These 

figures correspond to 30 percent and 4 percent of the 

nitrogen and phosphorus inputs, respectively. The 

mean annual load of total nitrogen discharged from

Table 16. Estimated annual nutrient inputs to the upper Illinois River Basin from various sources 

[--, insufficient data]

Source

Contribution, In tons per yeer

Nitrogen Phosphorus

Wastewater-treatment plants'

Fertilizers2

Urban runoff3

Atmospheric deposition4

Ground water5

Lake Michigan diversions6

26,000

210,000

860

7,500

260

2,100

5,400

87,000

1,200

16

340

Total inputs to upper Illinois River Basin

Exported load in streams estimated from concentration measurements

247,000

74,730

(30 percent of input)

94,000

3,850

(4 percent of input)

Surplus storage in upper Illinois River Basin 172,000 90,000

1 Jerry Davis, U.S. Geological Survey, written commun., 1993.

Illinois Department of Agriculture, 1988a, 1988b.

3Uuormark and others, 1974; Donigian and Crawford, 1976; and Manning and others, 1977.

4National Atmospheric Deposition Program, 1989.

'Mades, 1987; Voelker and others, 1987.

6U. S. Army Corps of Engineers, 1990.

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 55
the upper Illinois River Basin from 1987-90 was 

approximately 74,700 tons per year, and the corresponding nitrogen yield was 6.82 (tons/rm'2)/yr. The 

Des Plaines River Basin contributed about 41 percent 

of the total nitrogen load, and the Kankakee and Fox 

River Basins contributed about 39 and 13 percent of 

the load, respectively (table 10). The large contribution from the Des Plaines River Basin was due to the 

nitrogen load in the CSSC about 24,400 tons per 

year, or 33 percent of the total upper Illinois River 

Basin load. The spatial distribution of total nitrogen 

yields was similar to the distribution for total nitrogen 

concentrations. The distribution of total nitrogen 

loads, however, was considerably different and resembled the distribution of streamflow.

Stream loads during low-flow conditions were 

estimated as the product of measured discharge and 

constituent concentrations for samples collected during the 1988 low-flow synoptic survey. Because 

low-flow loadings represent a temporary condition and 

were based on a single measurement, low-flow loads 

are expressed in units of tons per day. The total 

nitrogen load exported from the upper Illinois River 

Basin under low-flow conditions was about 49 tons/d. 

The Fox and Kankakee River Basins each contributed 

only about 1 percent of the total upper Illinois River 

Basin nitrogen load during the low-flow synoptic 

survey (table 13 and fig. 13). The Des Plaines River 

Basin supplied virtually all of the low-flow nitrogen 

load. The estimated low-flow load in the CSSC was 

about 48.2 tons/d, and the Des Plaines River above the 

mouth of the CSSC provided an additional 8.3 tons/d. 

Some loss of in-stream nitrogen occurs between the 

mouth of the CSSC and Illinois River at Marseilles 

during low-flow conditions (table 13 and fig. 13). 

These losses are likely due to consumptive and 

depositional processes and denitrification.

The mean annual load of phosphorus from the 

upper Illinois River Basin was 3,850 tons per year, 

and the basin-wide yield was 0.35 (ton/mi )/yr. As 

with ammonia, most of the phosphorus load was in 

the CSSC. The spatial distribution of phosphorus 

was similar to that for ammonia, and wastewatertreatment-plant effluents are likely the major source 

of phosphorus to streams in the upper Illinois River 

Basin although agricultural practices are the greatest 

source of phosphorus into the drainage basin. The 

cumulative phosphorus loads from tributaries to the 

Illinois River were larger than the load at Illinois River 

at Marseilles, indicating that not all of the phosphorus

load introduced into the streams is transported through 

the upper Illinois River Basin under normal conditions.

Total nitrogen loads decreased by 70 to 80 percent in the lower reaches of the Fox and Kankakee 

Rivers. Except for NO2 + NC>3, loads for all forms 

of nitrogen and for total phosphorus decreased in the 

lower reaches of these rivers during low-flow conditions (figs. 13-17). Loads of NO2 + NO3 increased 

in the lower Kankakee River.

Temporal variability in water quality can be 

described in different ways, including abrupt changes, 

diurnal variations, seasonal changes, and long-term 

trends. This variability can be caused by many 

factors, but changes in climatic season, constituent 

sources, and land use are the most common causes. 

Long-term trend analyses can provide information on 

changes in water quality over time and can indicate 

future changes or problems.

The trend analyses for the fixed stations indicated significant upward trends in total nitrogen 

concentrations at three stations (table 14). Two of 

the upward trends were for flow-adjusted concentrations and one was for nonadjusted concentrations. 

The drainage areas and hydrologic characteristics of 

these three stations are different, and the causes for the 

upward trends are likely different as well. Iroquois 

River near Chebanse represents a predominantly 

agricultural drainage area with substantial nitrogenfertilizer use and large concentrations of NO2 + NC^. 

Du Page River at Shorewood is in an urban watershed 

with inputs from wastewater-treatment plants 

upstream. Fox River at Algonquin represents a 

somewhat mixed land-use area and a regulated stream 

with large backwater areas. Organic nitrogen is a 

major form of nitrogen at this station (table 9). The 

trends in nonadjusted and flow-adjusted concentrations at Du Page River at Shorewood were comparable, indicating that although there was a correlation 

between total nitrogen concentrations and streamflow, 

streamflow did not have a large effect on the upward 

trends in nitrogen concentrations. Elder (in press) 

found a downward trend in total nitrogen concentrations from 1978-86 at Illinois River at Marseilles and 

an upward trend at Fox River at Algonquin. Many 

causes for the trends in nitrogen and phosphorus in the 

upper Illinois River Basin are possible, including 

increases in fertilizer use, changes in land use (primarily urbanization), the implementation of Chicago's 

Tunnel and Reservoir plan (a combined flood-control

56 Nutrients, Dissoived Oxygen, and Fecsi-indicator Bscteria in Surface Water, Aprii 1987 Through August 1990
and water-quality-improvement project), decreased 

use of phosphate cleaning agents, increases in population, and variations in climatic conditions.

For total phosphorus, downward trends in flowadjusted concentrations at Illinois River at Marseilles 

and in nonadjusted concentrations at Fox River at 

Dayton (table 14) were found. These two stations 

are the stations that collectively represent the entire 

upper Illinois River Basin. The downward trend at 

Illinois River at Marseilles also was found by Elder 

(in press), as was a downward trend at Des Plaines 

River at Riverside.

Trends in NO2 + NO3 concentrations were 

found at five stations; all were upward trends 

(table 14). The largest upward trend in NO2 + NO3 

concentrations was in the Des Plaines River Basin 

(at CSSC at Romeoville). Concentrations of 

NO2 + NO3 in the CSSC increased by 0.568 mg/L 

per year, or 20 percent of the 1978-90 median concentration per year. The upward trends in NO2 + NO3 

concentrations could have resulted from a variety of 

causes, including progressive urbanization. The 

only trend in NO2 + NO3 concentrations identified 

by Elder (in press) was an upward trend in nonadjusted concentrations at Du Page River at Shorewood.

The only significant trend in organic nitrogen 

concentrations was a downward trend at CSSC 

at Romeoville (table 14). The magnitude of this 

trend was -0.13 mg/L per year, or 12 percent of the 

1978-90 median concentration per year. An upward 

trend at Fox River at Algonquin from 1978-86 was 

identified by Elder (in press), but no trend was found 

from 1978-90 at this station.

No flow-adjusted ammonia concentrations were 

determined because there were no statistically significant regressions between streamflow and ammonia 

concentrations at any of the fixed stations. Upward 

trends in nonadjusted ammonia concentrations were 

found for the stations in the Kankakee River Basin and 

for Fox River at Algonquin. Downward trends were 

found at CSSC at Romeoville and at Illinois River at 

Marseilles. The downward trend at CSSC at 

Romeoville contributed to the decrease at Illinois 

River at Marseilles. The only trend in ammonia concentrations found by Elder (in press) was downward at 

Du Page River at Shorewood.

Some of the factors that can change with climatic season and can affect in-stream nutrient concentrations and loads include precipitation, streamflow, 

temperature, water use, biological activity, erosion,

and land-use practices. Several notable instances of 

seasonal variation in nutrient concentrations at the 

fixed stations were noted (fig. 18). Seasonal variations in total nitrogen concentrations were found at 

Iroquois River near Chebanse, CSSC at Romeoville, 

and Illinois River at Marseilles. In all instances, total 

nitrogen concentrations were large in the winter and 

spring and small in the summer and fall. This seasonality was seen in both agricultural and urban drainage areas, showing that land-use activities were not 

the only factor affecting the seasonality of total nitrogen concentrations. Changes in temperature, precipitation, and biological activity associated with climatic 

season were likely the key factors promulgating seasonal changes in total nitrogen concentrations. Most 

agricultural fields in the upper Illinois River Basin are 

barren during the nongrowing season, and nutrient and 

sediment transport from the fields is unrestricted by 

vegetation.

The seasonal variations of NO2 + NO3 concentrations at the fixed stations were similar to those of 

total nitrogen, except at CSSC at Romeoville, where 

concentrations were smallest in the spring (fig. 18). 

The difference between the seasonality of total nitrogen and nitrite plus nitrate was accounted for by the 

seasonality of ammonia. Ammonia comprises a 

large part of the total nitrogen concentration at CSSC 

at Romeoville, and ammonia concentrations were 

largest in the spring and smallest in the summer and 

fall. This seasonality might be a result of reduced 

efficiency of nitrogen transformation processes at cold 

temperatures.

Seasonality of nutrient loads was noted at some 

of the fixed stations and for some nutrient forms. 

Seasonality of nutrient loads typically was caused by 

seasonal variation of streamflow, but differences were 

found among stations. At the stations in agricultural 

basins, the largest loads, streamflows, and nutrient 

concentrations typically were found in the spring and 

also were often large in the winter. At Du Page River 

at Shorewood, a station with substantial upstream 

inputs from treatment plants and urban influences, no 

large seasonal differences in streamflow, nutrient concentrations, or nutrient loads were found. For CSSC 

at Romeoville, streamflow and loads of total nitrogen, 

NC>2 + NO3, and ammonia were larger in the summer 

 the opposite seasonality found at most of the other 

fixed stations.

Data from the 1990 storm synoptic survey were 

used to determine NO2 + NO3 concentrations during

Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria 57
summer storms and to examine relations between 

these concentrations and streamflow in an agricultural 

basin. Correlation analyses of NO2 + NC>3 concentrations and streamflow were done for stations where 

10 or more samples were collected during the storm 

synoptic survey (table 15). The variation explained 

by the correlations, as measured by rho, decreased 

from 0.9702 at Iroquois River at Rosebud, the most 

upstream station on the Iroquois River, to -0.3074 at 

Iroquois River near Chebanse, the most downstream 

station. At the three most upstream stations, concentrations of NO2 + NC>3 increased notably with an 

increase in streamflow. At Iroquois River at 

Iroquois, the correspondence between NO2 + NC>3 

concentrations and streamflow was not as strong. At 

the two most downstream stations on the Iroquois 

River, NO2 + NO$ concentrations decreased at high 

streamflows. It appeared that NO2 + NC>3 concentrations were diluted from streamflows greater than about 

5,000 ftVs at Iroquois River near Chebanse.

Although the correlation tests determine relations between concentration and streamflow, the 

correlation analyses do not distinguish between samples collected from different parts of the runoff 

hydrograph; that is, no distinction was made between 

concentrations for samples collected before, during, 

and after the peak runoff for any particular storm. It 

is generally found that a sample collected before the 

runoff peak has a larger concentration than a sample 

collected after the peak runoff. These characteristics 

might vary at individual sites and might affect the 

strength of the correlations, or the effect of streamflow 

or nutrient concentrations at some sites.

Water-quality standards for Illinois, Indiana, 

and Wisconsin and Federal water-quality criteria for 

several nutrients are given in table 17. Federal 

water-quality criteria do not have a direct regulatory 

use, but they provide a basis for judgment for waterquality considerations (U.S. Environmental Protection Agency, 1976). Water-quality standards adopted 

by State regulatory agencies commonly are based on 

Federal criterion but are modified to reflect local conditions, concerns, and water uses. Except for CSSC 

at Romeoville, the Illinois general-use water standards 

are applicable for the fixed stations. General-use 

waters are suitable for aquatic life, primary (for example, swimming) and secondary (for example, boating) 

contact, agricultural, and industrial uses. The CSSC 

is designated as a secondary-contact water body 

(fig. 22). Secondary-contact waters are designated

for industrial and less than full-body-contact use. 

Synoptic sites were located in all three States as well 

as on streams designated as secondary-contact waters. 

The Illinois water-quality standards are applicable to 

all of the fixed stations, while Indiana and Wisconsin 

standards and Illinois secondary-contact standards are 

applicable for some synoptic sites. For purposes of 

this discussion, however, the Illinois water-quality 

standards will be used.

Only five water samples collected at the fixed 

stations, all at Illinois River at Marseilles, were found 

to have ammonia nitrogen concentrations larger than 

the Illinois general-use standards (table 17). The 

total ammonia concentrations of these samples were 

less than 15 mg/L, but the un-ionized ammonia concentrations were larger than the water-quality standards allow. The large un-ionized ammonia concentrations were likely a result of large concentrations in 

the CSSC upstream from Marseilles.

At each of the fixed stations, from zero to 

five samples contained un-ionized ammonia concentrations larger than the water-quality standard of 

0.04 mg/L. From 90 to 100 percent of the samples 

collected at the fixed stations had un-ionized ammonia 

concentrations that met the water-quality standard.

Phosphorus concentrations generally were 

larger than the Illinois general-use water-quality 

standard of 0.05 mg/L (table 17). The phosphorus 

standard, however, is applicable only to a stream at 

the point where it enters a lake or reservoir. This 

standard is not directly applicable to any of the fixed 

stations. Phosphorus concentrations at the fixed 

stations exceeded 0.05 mg/L in many of the samples 

collected. More than 90 percent of the samples 

collected at stations in the Des Plaines and Fox River 

Basins had phosphorus concentrations larger than the 

Illinois general-use water-quality standard.

Samples collected during the 1988 low-flow 

synoptic survey were collected during warm temperatures and low streamflows, generally considered to be 

indicators of drought conditions. Under these conditions, effects from point-source inputs were enhanced. 

Most of the point sources in the upper Illinois River 

Basin are in the Des Plaines River Basin, and the 

major point sources include several large wastewatertreatment plants that receive both domestic and 

industrial wastewater. No ammonia nitrogen or 

un-ionized ammonia concentrations larger than the 

Illinois general-use water-quality standard were found

58 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
Table 17. Federal water-quality criteria and State water-quality standards for nutrients in surface water in the upper Illinois R

[mg/L, milligrams per liter; --, no applicable criteria or standard]

Illinois1

Nutrient

Ammonia 

nitrogen

Units

mg/L

General 

use

S 1.5-15

Public and 

food-processing 

weter aupply

5 1.5-15

Secondary contact 

and Indigenous 

aquatic life

2.5 April-October 

4.0 March-November

Indiana2

Aquatic 

life

-

Put-and-take 

trout water

-

Fish and 

equatlc 

life

-

Wi

Trout 

water

-

Nitrate nitrogen mg/L 10.0 

Un-ionized 

ammonia

mg/L .04 .04 Criteria depends

on temperature

andpH

Criteria depends

on temperature

andpH

0.04 

warm 

water

0.06 

cold 

water

I

Total phosphorus mg/L 8.05 .05

'Illinois Pollution Control Board, 1982.

Indiana Stream Pollution Control Board, 1977.

'Wisconsin Department of Natural Resources, 1985.

4U.S. Environmental Protection Agency, 1986.

'Dependent upon pH and temperature. Ammonia nitrogen shall not be greater than 1S mg/L. If ammonia nitrogen is greater than or equal to 1.5 m

un-ionized ammonia shall not exceed 0.04 mg/L. Un-ionized ammonia is calculated based upon ammonia nitrogen concentration, pH, and temperature as 

Agency (1990).

"Maximum contaminant level for drinking water.

'Criteria specified in U.S. Environmental Protection Agency (1986).

8For a reservoir of lake with a surface area greater than or equal to 20 acres or any stream at the point where it enters any stem reservoir or lake.

5a

I

j_

a 

o

i

a
88° 05' 87° 45'

42° 05' 

41° 50'

41° 35'

from US Geological Survey 0 5 10 15 MILES

1:100,000 Digital Line Graphs 

Albers Equal-Area Conic projection 

Standard parallels 33° end 45°, central meridien -89°

EXPLANATION

STREAMS DESIGNATED AS SECONDARY 

CONTACT WATERS

II T

0 5 1015 KILOMETERS

\ STUDY 

AREA

Figure 22. Streams in the upper Illinois River Basin designated as secondary-contact waters.

60 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
in samples collected during the synoptic survey. All 

but five phosphorus concentrations at the synoptic 

sites, however, exceeded the Illinois general-use 

water-quality standard of 0.05 mg/L. The largest 

total phosphorus concentration, 4.0 mg/L, was in a 

water sample collected at Salt Creek at Wood Dale, 111.

Dissolved Oxygen

The sustenance of aquatic life depends upon 

the availability of oxygen. Although most anthropogenic water uses do not require large DO concentrations, the usefulness of water may be limited by low 

DO concentrations.

Oxygen is a moderately soluble gas present in 

most natural surface waters. Major sources of DO 

are limited to oxygen release during photosynthesis 

and the atmosphere. The DO concentration in 

streams is affected by plant growth, stream hydraulics, 

salinity, temperature, and barometric pressure. The 

amount of DO that can be stored in stream water 

depends on air pressure and temperature the saturation concentration of DO decreases with decreasing 

atmospheric pressure and with increasing temperature. 

Oxygen is removed from aquatic systems by biological respiration, decomposition of organic material, and 

oxidation of inorganic waste. DO concentrations in 

natural waters typically are less than 10 mg/L 

(McNeely and others, 1979) and may approach zero 

under oxygen-demanding conditions.

Concentrations of DO often fluctuate diurnally 

and seasonally. DO concentrations typically are 

largest during the daylight hours, when sunlight 

is available and plant photosynthesis is producing 

oxygen. Because the ability of water to hold DO 

depends on temperature, concentrations typically are 

larger during the cold season when low temperatures 

increase the saturation level for dissolved oxygen in 

water.

Concentrations of DO vary widely in natural 

waters and in waters affected by anthropogenic 

activities. Statistical summaries of the DO concentrations at the fixed stations for 1987-90 are given in 

table 18. Median DO concentrations ranged from 

3.4 mg/L at CSSC at Romeoville to 12.2 mg/L at Fox 

River at Dayton. Median concentrations at the other 

fixed stations were 8.7 to 9.7 mg/L.

Measurements of DO were typically made during daylight hours at the fixed stations, when plant 

photosynthesis is actively replenishing in-stream DO. 

During the 1988 synoptic survey, DO measurements 

were made just before sunrise, when DO concentrations are typically at the lowest point of the diurnal 

cycle.

The small DO concentrations at CSSC at 

Romeoville reflect the effects of wastewater-treatment-plant effluent and factors related to urbanization. 

As mentioned earlier, discharges from treatment plants 

in the Des Plaines River Basin contribute approximately 54 percent of the streamflow at CSSC at 

Romeoville. Concentrations of DO in the effluent

Table 18. Statistical summary of dissolved oxygen concentrations in surface-water samples collected at the eight 

fixed stations in the upper Illinois River Basin, April 1987 through August 1990

Station name (map reference number2)

Kankakee River at Momence, 111. (14)

Iroquois River near Chebanse, Dl. (28)

Des Plaines River at Riverside, 111. (40)

Chicago Sanitary and Ship Canal

at Romeoville, 111. (55)

Du Page River at Shorewood, Dl (69)

Illinois River at Marseilles, 111. (76)

Fox River at Algonquin, 111. (89)

Fox River at Dayton, El (99)

Number 

of 

observations

475

816

435

615

491

509

618

452

Percentite1 , in milligrams per liter

10

6.9

3.4

5.8

2.0

7.0

6.7

5.0

8.5

25

8.2

6.2

7.0

2.9

8.2

7.6

6.3

10.3

50 

(median)

9.6

8.8

9.1

3.4

9.7

9.7

8.7

12.2

75

11.2

11.4

11.0

4.9

12.3

11.8

11.3

14.2

90

12.1

12.3

12.3

7.0

15.0

13.2

14.8

16.0

'Percentage of total observations with concentrations less than or equal to the value shown. 

2See table 3 and figure 4.

Dissolved Oxygen 61
from the three largest treatment plants upstream from 

Romeoville typically were 6 to 8 mg/L. Although 

the DO concentrations in the effluent were not small, 

the effluent could still have reduced DO concentrations in the CSSC because wastewater-treatment-plant 

effluent typically contains large concentrations of 

organic material, and the decomposition of organic 

matter requires oxygen; the oxygen used by the 

decomposition processes likely reduces the in-stream 

DO concentration. In addition, the physical characteristics of the CSSC are not conducive to large DO 

concentrations. The CSSC is a rectangular channel 

approximately 25 ft deep. Streamflow velocities 

in the CSSC typically are low (less than 1 ft/s). 

Turbulence and atmospheric interaction in the 

CSSC are limited except for that caused by barge 

traffic. The water quality, shipping activity, and 

physical characteristics of the CSSC limit aquaticplant growth in the CSSC and limit associated DO 

production. The median concentration of chlorophyll-a at CSSC at Romeoville was 2.80 mg/L, 

indicating minimal DO production by aquatic plants 

in the CSSC. The relatively large DO concentrations 

at Fox River at Dayton are likely attributed to DO 

production by plants in a large backwater area created 

by a dam just upstream from the station. Although 

DO in this backwater was not measured, similar 

pooled areas along the Fox River had chlorophyll-a 

concentrations of almost 200 mg/L during the lowflow synoptic survey in 1988. Much of the time, the 

DO concentrations at Fox River at Dayton indicate 

that the water is supersaturated with respect to DO. 

With the exception of these two stations, no substantial differences among median DO concentrations 

were found at the fixed stations.

Data collected at the low-flow synoptic sites 

provided additional information on the spatial distribution of DO during warm weather and low-flow conditions (fig. 23). All DO concentrations in the Fox 

River Basin exceeded 5.0 mg/L, the minimum allowed 

by the Illinois water-quality standard for general-use 

waters; some exceeded 9.0 mg/L. The three sites 

where DO concentrations exceeded 9.0 mg/L were 

in or downstream from slow-moving stream reaches 

where plant photosynthesis supplies oxygen to the 

stream water. In the Kankakee River Basin, a basin 

with few urban areas, DO concentrations at 59 percent 

(35) of the sites were less than 5.0 mg/L, and less 

than 3.0 mg/L at 3 percent (2) of the sites. Some, 

but not all, of the stations where DO concentrations

in the Kankakee River Basin were small were a couple 

of miles downstream from wastewater-treatment 

plants. Wastewater-treatment-plant effluents, low 

streamflow, and hot weather are all factors that likely 

contributed to the relatively low DO concentrations in 

the Kankakee River Basin. DO concentrations were 

less than 5 mg/L at 49 percent (29) of the sites in the 

Des Plaines River Basin. Neither stream size nor 

land use appeared to be prevailing factors affecting 

DO concentrations at the synoptic sites. Streamflow, 

channel characteristics, aquatic flora, and local contaminant sources were site-specific characteristics 

that affected DO concentrations.

Federal water-quality criteria for DO are 

temperature and water-use specific. State waterquality standards for DO and the number of DO 

measurements at the fixed stations not meeting the 

water-quality standards are shown in table 19. These 

data include measurements made during the fixedstation sampling, the low-flow synoptic surveys, and 

some storm-runoff-sampling efforts. The Illinois 

water-quality standard for DO in general-use waters 

states that DO shall not be less than 5.0 mg/L at any 

time. This standard is applicable for all of the fixed 

stations except for the CSSC, which is classified as a 

secondary-contact water body.

In 1987, 36-hour sampling efforts were done at 

three of the fixed stations to determine the diurnal 

variation of selected properties, including the DO concentration in the streams. These efforts were done at 

CSSC at Romeoville, Du Page River at Shorewood, 

and Fox River at Algonquin. These stations were 

selected because they represent the variety of drainage 

areas and water-quality conditions in the upper Illinois 

River Basin. The CSSC at Romeoville represents an 

urban drainage area with substantial wastewater input, 

and Du Page River at Shorewood represents a small 

stream that drains an area with mixed land use and 

receives some wastewater. Fox River at Algonquin 

represents a predominantly agricultural basin with 

some urban development and some channel modification. DO concentrations and water temperature measured over 36-hour periods are shown in figure 24. 

DO concentrations at CSSC at Romeoville were small, 

ranging from 1.8 to 4.1 mg/L. Larger DO concentrations (8.1-9.5 mg/L) were measured at Du Page River 

at Shorewood. The DO concentrations measured at 

Fox River at Algonquin were the most variable over 

the diurnal cycle and ranged from 3.8 to 11.9 mg/L. 

The chlorophyll-a concentration measured at Fox

62 Nutrients, Dissolved Oxygen, and Fecsl-lndicator Bacteris in Surface Water, April 1987 Through August 1990
43°

EXPLANATION

BASIN BOUNDARY 

CONCENTRATION OF DISSOLVED

OXYGEN, IN MILLIGRAMS

PER LITER

Greater than 9

LAKE MICHIGAN

Chicago Sanitary and 

Ship Canal

Base from US Geological Survey

1:100,000 Digital Line Graphs

Albers Equal-Area Conic projection

Standard parallels 33° and 45°, central meridian -89

40 MILES

40 KILOMETERS

Figure 23. Spatial distribution of dissolved oxygen concentrations at the low-flow synoptic-survey surfacewater sites in the upper Illinois River Basin, July 26 through August 13, 1988.

Dissolved Oxygen 63
Table 19. Number of samples collected at the eight fixed surface-water stations in the upper Illinois River Basin and 

number of samples with dissolved oxygen concentrations that were less than the Illinois, Indiana, or Wisconsin 

water-quality standards 

[mg/L, milligrams per liter]

Number of samples with concentrations less than 

State water-quality standards for dissolved oxygen

Station name (map reference number)

Kankakee River at Momence, El. (14)

Iroquois River near Chebanse, Dl. (28)

Des Plaines River at Riverside, Dl. (40)

Chicago Sanitary and Ship Canal at

Romeoville, El. (55)

Du Page River at Shorewood, 111. (69)

Illinois River at Marseilles, Dl. (76)

Fox River at Algonquin, EL (89)

Fox River at Dayton, Dl. (99)

Number

of

samples*

55

62

48

48

53

57

48

49

General

use,

5.0 mg/L

minimum

0

2

1

32

1

0

5

0

Illinois1

Secondary-contact

and indigenous

aquatic life,

4.0 mg/L minimum

0

1

0

23

0

0

0

0

Indiana2

Aquatic life,

5.0 mg/L

average

per day

0

2

1

32

1

0

5

0

Wisconsin3

Fish and

aquatic life,

5.0 mg/L

minimum

0

2

1

32

1

0

5

0

'Illinois Pollution Control Board, 1982. 

Indiana Stream Pollution Control Board, 1977. 

'Wisconsin Department of Natural Resources, 1985. 

'Average of multiple measurements made across the stream.

River at Algonquin during the 1988 synoptic survey 

was 200 mg/L, indicating significant plant production 

that might have a substantial effect on the diurnal DO 

variation.

Diurnal variations in DO concentrations at 

CSSC at Romeoville were small, probably because 

of (1) the large percentage (50 percent) of the total 

streamflow composed of treatment-plant effluents,

(2) the lack of aquatic plant life in the CSSC, and

(3) the hydraulics and geometry of the CSSC. 

Similarly, DO concentrations fluctuated little at 

Du Page River at Shorewood for unknown reasons. 

Median total organic carbon concentrations, an 

indicator of oxygen-demanding substances, were 

6.50 to 12.0 mg/L at the fixed stations.

DO concentrations commonly vary seasonally 

with aquatic-plant growth, temperature, streamflow, 

and sunlight. In the upper Illinois River Basin, 

significant seasonal variations in DO concentrations 

were observed at most of the fixed stations. At all 

stations, the largest concentrations were measured 

during the winter months, and the smallest concentrations were measured during the summer months. 

Seasonal variation in DO concentration generally 

was less in the Des Plaines River Basin than other 

parts of the upper Illinois River Basin and was likely 

because of urban factors and the presence of point

sources of surface-water contamination. Streamwater temperature in the CSSC at Romeoville was 

warmer than that in natural streams in the area in the 

winter months because of wastewater-treatment-plant 

inputs.

Correlations were done to determine the relations among DO concentrations and streamflow, 

water temperature, and chlorophylls concentrations. 

The results of the correlation analyses are given in 

table 20. DO concentrations were not correlated 

with streamflow at the fixed stations, with the exception of CSSC at Romeoville where a weak negative 

correlation was indicated. The negative correlation 

is likely caused by small DO concentrations in urban 

runoff, the reduction in DO by organic oxygendemanding wastewater inputs, and by overflows 

from combined-sewer systems during storms.

A negative correlation also was determined 

between concentrations of DO and chlorophylls. 

This result was surprising because the presence of 

plant biomass, estimated from chlorophylls concentration, was assumed to be indicative of plant photosynthesis and DO production. The negative 

correlation might result from a couple of processes: 

(1) Samples collected for the determination of chlorophyll-a concentrations were collected along with the 

water used for the water-quality analyses using depth64 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria In Surface Water, April 1987 Through Auguat 1990
3 

o

1U

o

til

UJ

cc 

o tii

Q

UJ 

CC

CC 

UJ 

D.

s

UJlcc

UJI

19

18

17

16

15

14

13

0600

Chicago Sanitary and Ship Canal at Romeoville, III. 

(Map reference number 55) TEMPERATURE

DISSOLVED OXYGENCONCENTRATION

1200 1800 

APRIL 21

2400 0600 1200 

I APRIL 22

1800

29

28

27

26

25

24

0600

Fox River at Algonquin, III. (Map reference number TEMPERATURE

DISSOLVED OXYGEN 

CONCENTRATION

11

10

9

8

7

6

5

4

1200 1800 

JULY 28

2400 0600 1200 

JULY 29

1800

CC 

UJ

CC 

UJ

a.

CC

o

20

19

18

17

16

15

0600

Du Page River at Shorewood, III. 

(Map reference number 69)

. . TEMPERATURE

DISSOLVED OXYGEN 

CONCENTRATION /'

10.0

oc IIII 

o

z 

o 

o

UJ

o

X

o

Q 

UJ

9.5 O

9.0

8.5

8.0

1200 1800 

SEPTEMBER 22

2400 0600 1200

SEPTEMBER 23

1800

Figure 24. Variations in temperature and dissolved oxygen concentrations at selected fixed surface-water 

stations in the upper Illinois River Basin during 36-hour periods.

Dissolved Oxygen 65
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and width-integrating techniques. The samples, 

therefore, included only suspended and free-floating 

plant matter and did not include biomass from periphyton, macrophytes, or any rooted or attached plants. 

(2) The suspended matter collected was a combination 

of phy toplankton and detached parts of plants and 

might have included both living and dead plant 

material. Some of the measured chlorophyll-a concentration, therefore, might represent decaying plant 

material that could be contributing to the consumption 

of oxygen rather than oxygen production. The 

inverse relation also might represent the effect of 

temperature. Although substantial quantities of DO 

might be produced by plants in the summer, warm 

water temperatures reduce the solubility of the oxygen 

in water.

Chlorophyll-a concentrations also were measured at most of the synoptic survey sites in 1988. 

In general, the largest chlorophyll-a concentrations 

were found in the large streams and were associated 

with low-velocity reaches and pooled areas. These 

environments are suitable for substantial plant growth 

and the production of oxygen. These areas, however, 

also are susceptible to depletion of oxygen from the 

subsequent decay of plant material.

No apparent relations between concentrations 

of chlorophyll-a and DO were found for measurements made during the synoptic survey. At those 

sites where chlorophyll-a concentrations exceeded 

100 |4,g/L, DO concentrations ranged from 3.38 mg/L 

(one of the lowest concentrations measured) to 

11.08 mg/L (one of the largest concentrations measured). Sites where large chlorophyll-a concentrations and correspondingly large DO concentrations 

were found are mostly in the Fox River Basin. Sites 

where large chlorophyll-a concentrations and small 

DO concentrations were found are in the Iroquois 

River Basin. Flow conditions, temperature, and 

channel morphology, as well as differences in the 

types of aquatic plants in the two basins, the stage of 

development and maturity of the plant communities 

at the time the synoptic survey was conducted, and 

differences in the turbidity of the streams also contribute to the differences in river basins. Many lowhead dams are located along the length of the Fox 

River and on other streams in the Fox River Basin, 

but these dams were found to both aerate and deaerate 

the water, depending on local conditions in the pooled 

areas above the dams, dam geometry, and other stream 

characteristics (Butts and Evans, 1978).

66 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria In Surface Water, April 1987 Through August 1990
Trends in DO concentrations at the fixed 

stations from 1978-90 also were determined by 

combining data collected at the fixed stations with 

data collected by the IEPA during 1978-86. Because 

water-quality data were not collected at CSSC at 

Romeoville prior to the NAWQA program, only 

4 years of record were available for this station. 

The ffiPA collected DO-concentration data at CSSC 

at Lockport, 111., about 5 mi downstream from 

Romeoville. Trend analyses for the CSSC were 

done by combining the 1978-90 IEPA data and the 

NAWQA data collected during 1987-90. Because 

regressions between DO concentrations and streamflow were not significant at the 0.10 level at any of the 

fixed stations, flow-adjusted concentrations were not 

used in the trend analyses.

The only statistically significant trends in DO 

concentrations were upward trends at Illinois River 

at Marseilles and Fox River at Dayton. These are 

the two most downstream stations in the upper 

Illinois River Basin, and the water quality at these 

stations represents the composite water quality of 

streams draining the entire upper Illinois River Basin. 

The upward trend at Illinois River at Marseilles had a 

slope of 0.15 mg/L (1.5 percent of the median concentration) per year, and the upward trend at Fox River at 

Dayton had a slope of 0.20 mg/L (1.7 percent of the 

median concentration) per year. The upward trend at 

Illinois River at Marseilles was similar to the trend 

identified by Kammerer and Blanchard (in press) for 

1978-86; they did not find a trend in DO concentrations at Fox River at Dayton.

Fecal-Indicator Bacteria

Stream water often carries pathogenic organisms that can limit the use of the water and cause 

illness to persons contacting or ingesting the water. 

Some illnesses that can be conveyed through water 

include typhoid, cholera, gastroenteritis, hepatitis, and 

dysentery. The presence of pathogenic organisms 

can limit or preclude fish and shellfish consumption, 

recreational activities, and other water uses. The 

determination of the presence of specific pathogenic 

organisms in water is difficult, expensive, and impractical for most monitoring programs. Instead, indicator organisms that are not pathogenic, but are found 

coincidently with many pathogens, are used to identify 

conditions that might pose human-health problems.

The indicator bacteria used to identify potential 

pathogenic pollution are bacteria native to the gastrointestinal tract of humans and other warm-blooded 

animals. The presence of these organisms in stream 

water indicates contamination by fecal matter. Types 

of fecal-indicator bacteria generally used for monitoring and regulatory purposes include several members 

of the coliform group namely, total coliform, fecal 

coliform, and Escherichia coli (E. coli), and the streptococcal group. Some specific sources of these bacteria include wastewater-treatment-plant effluents; 

runoff from feedlots, rendering plants and foodprocessing facilities; and septic drainage.

In the NAWQA program, fecal coliform and 

E. coli arc used to indicate bacterial contamination. 

Fecal coliform is the traditional indicator used by the 

USGS and by many Federal and State monitoring and 

regulatory agencies. E. coli is a subspecies of the 

coliform group and is used as an indicator organism by 

the USEPA and by an increasing number of monitoring agencies. Analyses for E. coli at the fixed stations began in July 1988 in conjunction with the lowflow synoptic survey.

Statistical summaries for fecal coliform and 

E. coli densities in water samples collected at the fixed 

stations are given in table 21. Fecal-coliform densities ranged from 1 to 45,000 col/100 mL at the fixed 

stations. The largest fecal-coliform densities were 

found at urban stations and at Du Page River at Shorewood and CSSC at Romeoville, in particular. The 

median fecal-coliform densities in NAWQA water 

samples collected during 1987-90 were one or two 

orders of magnitude larger at Des Plaines River at 

Riverside and at CSSC at Romeoville than at the other 

fixed stations. The spatial distribution of E. coli 

densities at the fixed stations was similar to that of 

fecal-coliform densities. Some of the largest fecalcoliform densities were found in water samples 

collected in 1987, before E. coli analyses were done.

The Wilcoxon matched-pairs signed-ranks test 

was used to determine whether the fecal-coliform and 

E. coli density data were comparable for samples that 

were analyzed for both species of bacteria. Most of 

the coliforms present were E. coli, and no statistically 

significant differences in the density data from the two 

bacteria tests were found.

Federal water-quality criteria and State waterquality standards for fecal-indicator bacteria differ. 

The Federal criteria are based on E. coli densities,

Fecal-Indicator Bacteria 67
Table 21 . Statistical summary of bacteria densities at the eight fixed surface-water stations in the upper Illinois River Basin, 

April 1987 through August 1990 

[Densities in colonies per 100 milliliters]

Map 

reference 

number2 Mean Minimum Maximum

Number 

of 

samples

10 25

Percent! le1

50 

(median)

75 90

14

28

40

55

69

76

89

99

587

604

8,600

3,970

1,360

216

82

629

Fecal conform (April 1987 through August 1990)

10

4

220

60

3

1

5

9

10,100

9,500

45,000

45,000

14,000

3,100

610

12,182

68

66

58

51

65

85

54

52

40

10

720

284

19

16

9

19

60

22

1,280

430

75

28

11

31

150

93

3,050

1,000

250

60

40

77

Escherichia coll (July 1988 through August 1990)

'Percentage of data less than or equal to the value indicated. 

2See table 3 and figure 4.

260

282

12,000

2,250

860

115

76

175

637

1,760

24,800

12,100

3,880

318

205

664

14

28

40

55

69

76

89

99

514

630

8,150

1,450

2,170

367

90

119

24

8

600

200

3

16

6

10

8,000

8,000

45,000

5,600

15,000

2,916

833

600

22

26

24

23

24

22

23

20

31

11

835

358

11

22

8

15

53

45

1,180

531

36

25

21

30

135

91

2,800

1,060

181

97

37

47

220

422

7,630

1,670

1,480

250

80

162

511

1,660

35,500

4,300

13,300

1,930

198

373

whereas most State standards continue to reference 

fecal-coliform densities.

In the NAWQA program, water samples are 

generally collected at the fixed stations on a monthly 

basis. Because most bacteriological criteria and 

standards are based on analyses of multiple samples 

collected during a specific time period (typically a 

30-day period), most Federal criteria and State standards are not directly applicable to specific samples 

collected as part of the NAWQA program. Table 22 

relates the bacteriological densities at the fixed stations to Federal water-quality criteria and State standards.

Bacteria densities greater than the water-quality 

criteria and standards were measured at all of the 

fixed stations, but densities larger than the criteria and 

standards were found most often at stations in the 

Des Plaines River Basin. All of the water samples 

analyzed for E. coli from Des Plaines River at 

Riverside contained densities that exceeded the 

single-sample criterion for infrequently used fullbody-contact recreation. Approximately 70 percent 

of the water samples from CSSC at Romeoville had

densities exceeding this criterion, as did about 

29 percent of the samples from Du Page River at 

Shorewood. About 5 percent of the water samples 

collected at stations in the Fox River Basin and 

9 to 15 percent of the water samples collected at the 

stations in the Kankakee River Basin exceeded the 

E. coli criterion. Similar percentages were found 

for fecal-coliform densities greater than the Illinois 

general-use water-quality standard of 200 coy 100 mL 

(as a monthly geometric mean of more than five samples), except at CSSC at Romeoville, where the percentage of samples exceeding the Illinois standard for 

fecal-coliform densities was substantially less than the 

percentage of samples exceeding the Federal criterion 

for E. coli densities.

The IEPA (1992) identified municipal wastewater, urban runoff, and combined sewer overflows 

as primary causes for less than full-use support (the 

water body is not suitable for all intended uses) of 

many streams in the Des Plaines River Basin. The 

presence of pathogens, as evidenced by indicator bacteria, was indicated to have been the cause for less

68 Nutrients, Dissolved Oxygen, snd Fecai-lndicstor Bacteria in Surface Water, April 1987 Through August 1990
Table 22. Relations of Federal water-quality criteria and State water-quality standards to bacteria densities at the eight fixed 

upper Illinois River Basin, April 1987 through August 1990

Number of samples with densities greeter than Indicated 

State water-qual

(colon

E. Coll

Station nsme

(map reference number5)

Kankakee River at Momence, 111. (14)

Iroquois River near Chebanse, 111. (28)

Des Plaines River at Riverside, 111. (40)

Chicago Sanitary and Ship Canal at

Romeoville, 111. (55)

Du Page River at Shorewood, 111. (69)

Illinois River at Marseilles, 111. (76)

Fox River at Algonquin, 111. (89)

Fox River at Dayton, 111. (99)

Number

of

samples

22

26

22

23

24

22

23

20

U.S., Environmental Protection

Agency criteria for £ coll

(colonies per 100 mlllllfters)4

 126

15

22

22

21

22

18

19

16

7235

5

9

22

21

11

6

1

3

«296

3

7

22

20

9

4

1

3

9406

2

5

22

20

7

3

1

1

10576

2

4

22

16

7

2

1

1

Number

of

samples

68

66

58

51

65

85

54

52

Illinois1

General-use 

waters

and public

and foodprocessing

water supply11

15

15

40

37

22

9

3

10

D

I

'Illinois Pollution Control Board, 1988. 

Indiana Stream Pollution Control Board, 1987. 

Wisconsin Department of Natural Resources, 1985. 

4U.S. Environmental Protection Agency, 1986. 

5See table 3 and figure 4. 

'Steady-state geometric mean. 

7Designated beach area, single sample. 

8Moderate full-body-contact recreation, single sample. 

'Lightly used full-body-contact recreation, single sample. 

10Infrequently used full-body-contact recreation, single sample. 

"200 col/100 mL monthly average for 5 samples.

12Less than 5,000 col/100 mL monthly average and less than 5,000 col/100 mL in 2 percent of samples and 20,000 col/100 mL in less than 5 percent 

13 1,000 col/100 mL monthly average for 5 samples and 2,000 col/100 mL maximum. 

l4Less than 400 col/100 mL in 90 percent of samples and less than 200 col/100 mL in more than 5 samples per month.

s

o
than full-use support in approximately 45 percent of 

the assessed river miles in the Des Plaines River 

Basin.

Prior to the 1988 low-flow synoptic survey, 

stream-water samples were collected at two sites in the 

upper Illinois River Basin over a 24-hour period to 

determine the extent of diurnal variation in E. coli 

densities. These two sites were downstream from 

known wastewater-treatment-plant discharges and 

were selected to show water-quality conditions at such 

locations. Water-quality samples were collected 

at approximately 2-hour intervals, and continuous 

records of streamflow and discharge from the treatment plants were obtained. The E. coli densities during these sampling efforts are given in table 23. The 

results of these two 24-hour diurnal studies showed 

that bacteria densities in the streams were variable but 

that the variability could not be related to either wastewater-treatment-plant discharge or streamflow at these 

sites.

The ability of bacteria to survive in water 

depends on several critical factors, including 

temperature, energy (food) supply, and toxicity of 

the environment. Changes in climatic season in the 

upper Illinois River Basin affect each of these factors. 

Cold-water temperatures retard bacteriological growth 

and slow down the decay processes that supply food 

to bacteria.

Plots of bacteria densities, by month, at the 

eight fixed stations are given in figure 25. The available data do not provide a conclusive determination of 

the seasonality of fecal-indicator bacteria densities; 

however, densities in urban drainage areas appear to 

be slightly larger in the summer and fall. These large 

densities might result from the intense thunderstorms 

characteristic of this season and the flushing of bacteria from surfaces by runoff.

Little seasonal variation in bacteria densities 

was found at the three stations in predominantly agricultural drainage areas. The variation in densities

Table 23. Escherichia co//densities in water samples collected at selected sites downstream from wastewatertreatment plants in the upper Illinois River Basin, June 28-30,1988 

[ftVs, cubic feet per second]

Time 

Station name (map reference number1 ) Date (hour)

Du Page River at Shorewood, 111. (69) June 28 1430

1600

1800

2000

2200

2400

June 29 0200

0500

0600

0800

1000

1200

Fox River at South Elgin, HI. (91) June 29 1500

1700

1900

2100

2300

June 30 0100

0300

0500

0700

0900

1100

1300

Stream 

discharge 

(ft3/*)

82.4

79.3

79.3

76.1

79.3

79.3

82.4

82.4

79.3

79.3

79.3

82.4

Daily mean

discharge2

= 182 fp/s

Daily mean

discharge2

= 196 f?/s

Wastewater-treatment-plent 

discharge (ftVs)

 Multiple wastewater-treatment

plants upstream, cumulative

discharge is unknown 

20

19

23

17

19

15

9

11

21

17

18

17

Density in 

colonies per 

100 mllliliters

383

97

66

112

410

390

61

440

2,500

270

250

1,333

4,700

460,000

7,670

133,000

380,000

173,000

6,360

69,700

1,790

1,650

2,300

500

'See table 3 and figure 4.

2Daily mean discharge estimated from regression with measured discharge at Fox River at Algonquin, 111. (89).

70 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
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72 Nutrients, Dissolved Oxygen, and Fecal-Indicator Bacteria in Surface Water, April 1987 Through August 1990
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Fecal-Indicator Bacteria 73
among samples collected at these stations typically 

was as large or larger than any seasonal variation in 

densities.

E. coli densities were measured in water samples collected during the low-flow synoptic survey in 

1988. During these conditions, point-source inputs 

and effects of these inputs are enhanced because of 

low natural streamflow and limited dilution potential. 

E. coli densities larger than Federal criteria for moderately and infrequently used full-body-contact recreation were measured at sites in every major river basin 

in the upper Illinois River Basin (fig. 26). The largest densities, up to 54,000 col/100 mL, were measured 

at sites on the secondary-contact designated streams 

and canals in the Chicago area. These large densities 

result from the discharge of wastewater to the streams. 

Although the low-flow synoptic survey was done during drought conditions, streamflow in many of the 

canals is maintained by water diverted from Lake 

Michigan to provide for the dilution of wastewater. 

Most of the sites with large E. coli densities were 

downstream from wastewater-treatment plants, 

although some sites were up to 10 mi downstream 

from some of the smaller treatment plants and the 

effect of the effluent on these densities this far from 

treatment plants is undetermined. At the two most 

downstream sites in the upper Illinois River Basin, 

Fox River at Dayton and Illinois River at Marseilles, 

E. coli densities were among the smallest in the basin. 

The combined streamflows at these two stations 

represent the total stream-water outflow from the 

upper Illinois River Basin, and the measured E. coli

densities indicated that the large densities at some sites 

in the upper Illinois River Basin are attenuated before 

the streamflow leaves the basin.

No significant trends in fecal-coliform densities 

were found for 1987-90 at any of the fixed stations. 

Because E. coli data were not collected until the latter 

part of 1988, no trend analyses of E. coli data were 

done. Fecal-coliform-density data collected during 

the NAWQA program were combined with data collected by the IEPA during 1978-86 to form a data set 

of monthly values for 1978-90. No significant 

regressions between fecal-coliform densities and 

streamflow were found at any of the fixed stations; 

therefore, no flow adjustment of bacteria densities 

was done. Significant downward trends in fecalcoliform densities for this period were identified at 

three of the fixed stations: Iroquois River near 

Chebanse, Fox River at Algonquin, and Fox River at 

Dayton (table 24). Kammerer (in press) found a 

downward trend in flow-adjusted fecal-coliform densities at Iroquois River near Chebanse for 1978-86.

SUMMARY

Data collected by the U.S. Geological Survey's 

(USGS) National Water-Quality Assessment 

(NAWQA) program were used to describe the presence, spatial distribution, and temporal variability of 

nutrients, dissolved oxygen (DO), and fecal-indicator 

bacteria in the upper Illinois River Basin in Illinois, 

Indiana, and Wisconsin from 1987 through 1990.

Table 24. Results of the seasonal Kendall trend test for fecal-coliform bacteria densities at the eight fixed surface-water

stations in the upper Illinois River Basin, 1978-90

[Underlining indicates those test results considered to be statistically significant based on a probability level of 0.1000]

Station name (map reference number1 )

Kankakee River at Momence, DL (14) 

Iroquois River near Chebanse, Dl. (28) 

Des Plaines River at Riverside, 111.2 (40) 

Chicago Sanitary and Ship Canal 

at Romeoville, 111.2 (55) 

Du Page River at Shorewood, 111. (69) 

Illinois River at Marseilles, 111. (76) 

Fox River at Algonquin, Dl. (89) 

Fox River at Dayton, Dl. (99)

Number of 

observations

94 

91 

31

32

91 

62 

104 

92

Probability 

level

0.4959 

.0025

1.0000 

.3407

.1543 

.8643 

.0693

.0082

Units 

per 

year

-6.7 

-20.0

50.0

-335

-11.6 

-1.0

-4.5

-22.8

Percent 

of 

median 

per year

-4.4 

-13.5

1.8 

-33.0

-4.0 

-1.0 

-7.0

-14.2

"See table 3 and figure 4.

2Trends at these stations are from 1987-90.

74 Nutrients, Dissolved Oxygen, snd Fecal-Indicator Bscteria in Surface Water, April 1987 Through August 1990
86°

EXPLANATION

BASIN BOUNDARY

DENSITY OF £ COLl 

BACTERIA. IN COLONIES 

PER 100 MILLILITERS

Greater than 5,000

577 to 5,000 

298 to 576 

Less than 298

_ .,£ ILLINOjS ;

LAKE MICHIGAN

Chicago Sanitary and 

Ship Canal

from US Geological Survey 

1:100,000 Digital Line Graphs 

Albers Equal-Area Conic projection 

Standard parallels 33° and 45°, central meridian -89°

40 MILES

20 40 KILOMETERS

Figure 26. Spatial distribution of Escherichia coll densities at the tow-flow synoptic-survey surface-water sites 

in the upper Illinois River Basin, July 26 through August 13,1988.

Summary 75
Data from 1978 through 1986 were available from the 

Illinois Environmental Protection Agency (IEPA) and 

were used in conjunction with USGS data to assess 

long-term trends in concentrations. Five nutrient 

forms total nitrogen, dissolved nitrite plus nitrate 

(N(>2 + NC>3), total ammonia, total organic nitrogen, 

and total phosphorus were used to represent nutrient 

conditions in the upper Illinois River Basin.

Numerous sources of nutrient inputs to the 

upper Illinois River Basin, including wastewatertreatment plants, agricultural runoff, urban runoff, 

precipitation, ground water, Lake Michigan withdrawals and diversions, soil erosion, and plant material 

were found. These sources supplied an estimated 

247,000 tons of nitrogen and 94,000 tons of phosphorus to streams in the upper Illinois River Basin each 

year. The quantities of nutrients input to upper 

Illinois River Basin streams from these sources is 

unknown. Approximately 74,730 tons of nitrogen 

and 3,850 tons of phosphorus are exported from 

the upper Illinois River Basin each year by the 

Illinois River.

Nutrient concentrations in streams in the upper 

Illinois River Basin generally were larger than concentrations typically found in natural waters. Nutrient 

concentrations in streams in urban areas, particularly 

in the Des Plaines River Basin, generally were larger 

than in streams in other areas of the upper Illinois 

River Basin. Median concentrations of total nitrogen 

at the fixed stations ranged from 2.20 to 9.78 mg/L. 

Small concentrations of total nitrogen were found at 

Kankakee River at Momence, and large concentrations 

were found at Iroquois River near Chebanse. 

Although both of these stations are in agricultural 

areas, differences in soil types between the drainage 

areas necessitate different drainage techniques for 

agricultural fields. Extensive tile drainage in the 

Iroquois River Basin provides efficient field drainage, 

resulting in larger nitrogen concentrations in the 

stream water.

Most of the nitrogen in upper Illinois River 

Basin streams was present as nitrate, and concentrations of NO2 + NO3 ranged from 0.22 to 9.80 mg/L 

at the fixed stations. Median concentrations of 

ammonia at the fixed stations ranged from 0.01 to 

7.40 mg/L. Ammonia concentrations were large at 

sites used to monitor urban drainage areas and at sites 

where substantial upstream inputs from wastewatertreatment plants occur. Organic nitrogen concentrations ranged from 0.87 to 1.70 mg/L at the fixed

stations. Organic nitrogen comprised a large fraction 

of the total nitrogen concentration at the stations in the 

Fox River Basin. During the low-flow synoptic survey, the largest organic nitrogen concentrations (up to 

14.2 mg/L) were found in water samples from streams 

in the Des Plaines River Basin. Point-source inputs 

were the suspected cause of elevated concentrations of 

organic nitrogen in streams in the Des Plaines River 

Basin during low-flow periods.

Median concentrations of total phosphorus 

ranged from 0.06 to 0.84 mg/L at the fixed stations, 

and the spatial distribution of phosphorus concentrations was similar to the distribution for total nitrogen. 

Adsorption of phosphorus to fine-sized sediment particles is suspected as one reason why large phosphorus 

concentrations are not found in the Iroquois River 

Basin.

Total nitrogen concentrations were found to 

be correlated with streamflow at most of the fixed 

stations. Positive correlations of streamflow and 

total nitrogen concentrations were found at most 

stations in agricultural areas, whereas negative correlations were found at most stations in urban areas. 

These correlations indicate that runoff is a major 

source of nitrogen to streams in agricultural areas, 

whereas point-source inputs are a major source of 

nitrogen in urban areas.

Phosphorus concentrations and streamflow were 

negatively correlated at four of the fixed stations and 

positively correlated at Iroquois River near Chebanse. 

This positive correlation was likely related to the 

suspension and transport of sediment-related phosphorus during periods of increased streamflow. The 

negative correlations at the other stations reflect dilution at high streamflow and, in some cases, effects of 

wastewater inputs at low flows.

The Des Plaines River Basin contributed 

approximately 41 percent of the total nitrogen load 

to streams in the upper Illinois River Basin, whereas 

streams in the Kankakee and Iroquois River Basins 

contributed about 34 and 14 percent of the total load, 

respectively. About 30 percent of the total nitrogen 

load in streams in the upper Illinois River Basin was 

measured in the Chicago Sanitary and Ship Canal 

(CSSC).

During low-flow conditions, virtually all of the 

total nitrogen load was found in streams in the 

Des Plaines River Basin. Most of this load was 

attributed to the CSSC, which receives substantial 

wastewater inputs. The CSSC also was found to

76 Nutrients, Dissolved Oxygen, and Fecai-indicator Bacteria in Surface Water, April 1987 Through August 1990
convey most ammonia and phosphorus loads under 

low-flow conditions.

Upward trends in total nitrogen concentrations 

during 1978-90 were found at three of the fixed 

stations: Iroquois River near Chebanse, Du Page 

River at Shorewood, and Fox River at Algonquin. 

Downward trends in phosphorus concentrations were 

found at the two most downstream fixed stations, 

Illinois River at Marseilles and Fox River at Dayton. 

The upward trends might be caused by increases in 

the use of fertilizers and increases in urbanization, 

whereas the downward trends in phosphorus might be 

a result of decreases in the use of phosphate cleansers 

and improvements to wastewater-treatment practices.

Seasonal variations in nutrient concentrations 

were found at several of the fixed stations. Nutrient 

concentrations typically were large in the winter and 

small in the summer. Because these variations were 

detected downstream from different types of land uses, 

changes in physical, chemical, and biological processes associated with climatic season were likely the 

key factors responsible for seasonal changes in nutrient concentrations. In addition, changes in nutrient 

inputs to the streams can vary with climatic season and 

hydrologic conditions.

Median DO concentrations at the fixed stations 

ranged from 3.4 mg/L at CSSC at Romeoville to 

12.2 mg/L at Fox River at Dayton. Median concentrations at the other fixed stations were 8.7 to 

9.7 mg/L. The small DO concentrations in the 

CSSC are due, in part, to the large amount of 

wastewater in the CSSC. The relatively large DO 

concentrations at Fox River at Dayton are likely 

caused by algae and plant photosynthesis in the 

pooled area behind a dam upstream from the station.

During the low-flow synoptic survey, 50 to 

60 percent of the sites in the Des Plaines and 

Kankakee River Basins had DO concentrations 

below the State standard of 5.0 mg/L. All DO concentrations in the Fox River Basin exceeded 5.0 mg/L, 

and some exceeded 9.0 mg/L.

Diurnal variations in DO concentrations were 

examined at three of the fixed stations. Substantial 

variations were found at Fox River at Algonquin, 

some variations were found at Du Page River at 

Shorewood, and no variations were found at CSSC 

at Romeoville. The diurnal changes were driven 

by plant photosynthesis. The sparsity of aquatic 

plants in the CSSC, the hydraulic characteristics of 

the channel, and the large percentage of wastewater

limited DO production and reaeration in the CSSC 

resulted in increases in oxygen demand in the water.

The only significant trends in DO concentrations at the fixed stations during 1978-90 were 

upward trends at Illinois River at Marseilles and Fox 

River at Dayton. Water quality measured at these 

two stations, the two most downstream stations in the 

upper Illinois River Basin, collectively represent the 

water quality in streams in the entire upper Illinois 

River Basin.

In the upper Illinois River Basin NAWQA 

program, fecal coliform and Escherichia coli (E. coli) 

were used to indicate bacterial contamination. Fecalcoliform densities at the fixed stations ranged from 1 

to 45,000 col/100 mL. The largest densities were 

found at stations in urban areas in the Des Plaines 

River Basin. Median densities for Des Plaines River 

at Riverside and CSSC at Romeoville were two orders 

of magnitude larger than the median densities at any 

of the other fixed stations and are likely results of 

wastewater inputs to these streams.

Bacteria densities larger than Federal criteria 

and State standards were found in 30 to 75 percent of 

the samples collected at the fixed stations in urban 

areas. In contrast, only 5 to 20 percent of the water 

samples collected at stations in agricultural areas were 

found to have bacteria concentrations larger than the 

Federal E. coli criteria for infrequently used full-bodycontact recreational waters.

Significant downward trends in fecal-coliform 

densities during 1978-90 were found at three fixed 

stations draining largely agricultural basins: Iroquois 

River near Chebanse, Fox River at Algonquin, and 

Fox River at Dayton. No significant trends were 

found at stations in urban areas for 1978-90.

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