The Condition of Illinois Water Resources 1972-1996

Photo of StreamPurpose

The Condition of Illinois Water Resources, 1972-1996 was prepared by the Illinois Environmental Protection Agency (Illinois EPA) as a summary of the comprehensive Illinois Water Quality Report, 1994-1995 (305(b) Report). The 305(b) Report consists of two volumes which describe in detail water quality conditions throughout the state of Illinois. In contrast, The Condition of Illinois Water Resourcestalks in general about Illinois rivers and streams, inland lakes, Lake Michigan, and groundwater. In addition, a set of 33 fact sheets has been created to look at specific water bodies in major Illinois watersheds.

Photo of Lake

The 305(b) Report

According to Section 305(b) of the federal Clean Water Act (CWA) of 1972, each state is required to prepare and submit to the U.S. Congress and the U.S. EPA a biennial report which includes:

  • an assessment of the water quality for surface and groundwater resources;
  • an analysis of the extent to which such waters provide for the protection and propagation of shellfish, fish, and wildlife as well as allow for recreational activities;
  • an analysis of the extent to which the requirements of the CWA have been achieved;
  • an estimate of the environmental impacts, costs and benefits, and time frame to achieve the requirements of the CWA; and
  • a description of the nature and extent of nonpoint source pollution and recommendations to address this pollution.

Water Quality in Illinois

Photo of Lake and FishersIllinois is blessed with abundant water resources. There are approximately 900 interior streams in Illinois. The state has natural borders to the west and southeast which are formed by the Mississippi, Ohio, and Wabash rivers, respectively. The other major rivers in Illinois include the Des Plaines, Rock, Fox, Kankakee, Illinois, Sangamon, Kaskaskia, Vermilion, Cache, and Big Muddy.

More than 87,600 inland lakes and ponds exist in Illinois (3,041 of which have surface areas of six acres or more). The majority of Illinois inland lakes (75%) are artificial impoundments, including reservoirs ranging up to 26,000 acres in surface area; dammed stream and side channel impoundments; and strip mine, borrow pit, and excavated lakes. Some of these artificial lakes include Lake Shabbona, Lake Le-Aqua-Na, Lake Carroll, Lake Decatur, Lake Shelbyville, Lake Carlyle, Crab Orchard Lake, Lake Springfield, and Lake Sangchris. Natural lakes include glacial lakes found in the northeastern counties, sinkhole ponds in the southwest, and oxbow and backwater lakes found along major rivers. Illinois lakes serve a multitude of purposes such as drinking water, recreation, flood control, industrial process cooling water, and fish and wildlife habitat.

Illinois is also bordered by one Great Lake - Lake Michigan. Illinois has jurisdiction over approximately one million acres of Lake Michigan stretching along the state's northeastern border and the city of Chicago. Lake Michigan is the third largest of the Great Lakes and is the largest body of freshwater totally within the boundaries of the United States. Together, the Great Lakes constitute the largest freshwater system on earth, with the exception of the polar ice caps.

Principal aquifer areas for groundwater in Illinois cover 32,400 square miles or 59 percent of the state. About 11,800 square miles of overlapping areas (aquifers at different depths) are accounted for in this figure. About 18,600 square miles of Illinois (33 percent of the state) are underlain by shallow aquifers with about 8,300 square miles designated as highly susceptible to groundwater contamination.

Water Quality Monitoring

The Illinois EPA has maintained an effective and efficient surface water and groundwater monitoring and assessment program since its inception in 1970. Changes and additions to the monitoring effort have been undertaken to keep pace with technological advances and broadening environmental concerns. Monitoring activities focus on water and sediment chemistry as well as on physiological and biological data (aquatic invertebrates, fish, and habitat). As a result of these monitoring and assessment programs, data from nearly 3,000 stations has been utilized in the assessment of surface water quality conditions. Illinois water resources are either "monitored" or "evaluated." "Monitored" assessments involve water samples taken by professional data collectors and tested by Illinois EPA staff. "Evaluated" assessments consist of volunteer-collected data or monitored data that is five years or more old.

Pie Charts of Stream Water Quality Conditions

The Illinois EPA conducts a wide variety of water quality monitoring programs. Among these are the Ambient Water Quality Monitoring Network, Intensive River Basin Survey, Facility-Related Stream Survey, Biological Stream Characterization, Ambient Lake Monitoring, Clean Lakes Program Intensive, Volunteer Lake Monitoring, Lake Water Quality Assessment, and Ambient Network of Community Water Supply Wells.

The objectives of these monitoring and assessment programs are to:

  • analyze and interpret data/information to evaluate attainment of designated uses (drinking water, recreation, etc.);
  • determine long-term trends in physical, chemical, and biological conditions;
  • identify water quality problems and problem areas and further investigate the extent and causes(s) of the problem;
  • provide a measure of the effectiveness of Illinois' water pollution control programs.

The Illinois EPA's water quality program is designed to protect the "designated uses" of the water resources of Illinois. Designated uses take into consideration the use and value of the water body for public water supply; for propagation of fish, shellfish and wildlife; and for recreational, agricultural, industrial and navigational purposes. In Illinois, water bodies have been classified for a variety of designated uses that include: general use, public and food processing water supplies, secondary contact, and indigenous aquatic life. Lake Michigan has its own designated uses based upon a set of more stringent standards. The water quality conditions of Illinois waters are described in terms of the degree to which the waters attain the designated uses. For this report and the 33 facts sheets, water quality is rated as either "good," "fair," or "poor." A "good" rating means a river or lake meets the needs of all designated uses. "Fair" means water quality has been impaired and the water body meets the needs of a designated use most of the time. A water body that is rated as "poor" has water quality that has been severely impaired and cannot support a designated use to any degree.

Rivers and Streams

Charts of Causes and SourcesRiver and stream quality in Illinois has improved considerably since 1972, and the number of miles of rivers and streams that are monitored by the Illinois EPA has also increased. Rivers and streams within and bordering Illinois include a total of 87,110 stream miles. For the 1994-1995 305(b) Report, a total of 28,454 river miles (an increase of 14,295 miles since the 1992-1993 305(b) Report) were assessed for overall resource quality. Of the 28,454 miles assessed, 54.3 percent were rated as "good," 44.8 percent were rated as "fair," and 0.9 percent were rated as "poor."

The major causes of water quality problems include nutrients and siltation. The major source of pollution is agriculture. A wide variety of waterborne toxics are monitored in Illinois rivers and streams. Copper, cadmium, lead, mercury, silver, and zinc exceeded the state standards at some monitoring stations. In-stream sediments, elevated concentrations of arsenic, chromium, copper, lead, mercury, zinc, cadmium, chlordane, DDT, dieldrin, or PCBs were identified in approximately 2,000 stream miles. Sport fish consumption advisories were present on 714.1 stream miles (19 percent of the 3,775 miles assessed) due to PCBs or chlordane levels in fish flesh.

Overall, stream water quality has steadily improved over the last 26 years. There has been a downward trend in metal concentrations and other conventional pollutants (such as low dissolved oxygen and total ammonia). Streams are generally impacted by multiple sources. The total miles of streams impacted by point sources (industrial and municipal wastewater discharges) has declined from 24.4 percent to 21.6 percent since 1987. However, increasing amounts of nutrients such as phosphorus and nitrite/nitrate have been identified in some rivers that are likely the result of nonpoint source pollution (mainly from agricultural activities). Further evidence of water quality improvements is the increased species diversity in the Illinois, Rock, and Mississippi rivers.

Water Quality Comparison, 1972 and 1996

Pie Charts of Lake Water Quality Conditions

Inland Lakes

In Illinois, more than 3,000 lakes (more than six acres in size) cover nearly 250,000 acres. Most publicly-owned lakes with 20 acres or more in surface area were assessed for this report, along with public and non-public lakes in the Illinois EPA's Volunteer Lake Monitoring Program. Assessments of these resources by the Illinois EPA have greatly expanded over the past 10 years. Of the 188,243 acres assessed, 30.5 percent of the lake acreage were rated as having "good" overall resource quality; 59.8 percent were rated as "fair;" and only 9.7 percent were classified as "poor."

Some improvements in lake water quality conditions were noticed when looking at current trends. Of the lake acres assessed, 21.5 percent were found to have water quality improvements in 1994-1995, as compared to 12.2 percent in 1992-1993. However, declining water quality trends increased from 16.9 percent of the acreage assessed in 1992-1993 to 19.6 percent in 1994-1995. Major causes of pollution impacting Illinois lakes included suspended solids and siltation; the most prevalent source of pollution is agriculture.

The Volunteer Lake Monitoring Program (VLMP) continues to be an important and successful program administered by the Illinois EPA. Over the past 15 years, this program has provided lake assessment information on over 300 lakes collected by more than 600 citizen volunteers. In this report, the VLMP accounted for 55 percent of the number of lakes assessed and 28 percent of the lake acreage assessed - these are lakes that otherwise would not have been monitored within the state.

Causes and Sources Impacting Lakes

Lake Michigan

Lake Michigan includes a total of 63 shoreline miles (976,640 acres), forming the northeastern portion of Illinois' border. Lake Michigan is protected to a greater degree than other lakes in Illinois by having more stringent water quality standards. Lake Michigan is monitored through a cooperative agreement between the Illinois EPA and the city of Chicago. The Illinois EPA is also required to provide the Illinois General Assembly and the Governor's Office with a separate report describing water quality conditions of Lake Michigan. This report is published in cooperation with the city of Chicago.

Since the 1970s, the water quality of Illinois' shore of Lake Michigan has improved substantially. Currently, all 63 shoreline miles were rated as having "good" overall water quality. All 63 miles of Illinois shoreline support drinking water uses. Major sources threatening the water quality of Lake Michigan include atmospheric deposition and contaminated sediments. Illinois' portion of Lake Michigan does have a sport fish advisory for some species of fish that limits their consumption.


Approximately 4.1 million people in Illinois rely on groundwater for their drinking water, which represents nearly 36 percent of the state's population. Other major consumers of groundwater in Illinois are industry and agriculture. These activities consume more than 24 percent of the total groundwater used in the state each year. In other terms, there are 5,534 public water systems in Illinois that utilize groundwater to meet the needs of their customers. Of the total 5,534, 1,195 are community water supplies (CWS). The remaining 4,446 groundwater supplies are non-community wells that serve restaurants, parks, and other businesses. Additionally, there are as many as 400,000 private wells.

Community Water Supplies DataThe Illinois EPA is making considerable progress in groundwater protection through innovative approaches such as the regional groundwater protection planning programs and the Safe Drinking Water Act Monitoring Waiver Program. However, many activities still contribute to groundwater contamination in Illinois. Major sources of water quality problems include leaking above and below ground fuel storage tanks, agricultural chemical operations, salt piles, and landfills.

Since the adoption of the Illinois Groundwater Protection Act in 1987, the Illinois EPA has developed approaches to track and quantify the amount of progress toward groundwater protection. The data for community water supply (CWS) wells in Illinois indicates:

  • 15,041 acres of the unconfined wells (critical resource groundwater that is vulnerable to contamination) have protection measures in place;
  • 149,721 acres of the unconfined wells in the state still lack adequate protection;
  • 64.4% of the recharge areas of unconfined wells are threatened by point and/or nonpoint source pollution.
  • 35.5% of the CWS wells using unconfined aquifers in the state have been impacted by groundwater contamination;
  • A significant number of CWS wells are using fully-protected confine aquifers (groundwater that is protected from pollution by formations of rock and sediment); and
  • Approximately 100 new CWS wells are permitted every year.

Watershed Management Program

Understanding what a watershed is and the particular features of a watershed are the first steps in the protection of water and other natural resources. A watershed is all of the land that drains into a body of water such as a lake, river, or groundwater. The Illinois EPA is developing a program based on enabling and empowering local stakeholders to take charge of the fate of their watersheds. This mission will be accomplished through a comprehensive approach to watershed planning which concentrates on all the resource concerns within a watershed, as well as coordinates local, state, and federal involvement in watershed management activities. The Illinois EPA's "Watershed Management Program" looks holistically at the range of problems that affect a given watershed, taking into account that most watersheds are experiencing an array of interrelated concerns. To be comprehensive, this watershed approach requires consideration of all environmental concerns such as public health (including drinking water), critical habitats, biological integrity, and surface and ground water. Watershed management can help to protect and restore natural resources, while allowing for sustainable economic growth and development.

Nonpoint Source Program

Nonpoint source (NPS) pollution is still a relatively new term in Illinois, as well as throughout the country. The signs and effects of this type of pollution, though, are not new. NPS pollution is the runoff of pollutants from various sources; precipitation moves over and through the ground and picks up pollutants from these sources and carries them into rivers, lakes, and groundwater. The major sources and causes of NPS pollution in Illinois are pesticide and fertilizer runoff from agriculture, construction site erosion, urban runoff, hydrologic modifications, soil erosion and sedimentation, livestock waste, and resource extraction. NPS pollution is the largest contributor to waters of the state failing to meet water quality goals. Illinois has received more than $14 million since 1990 (from Section 319 of the Clean Water Act) for public awareness/education and implementation of best management practices to reduce NPS pollution for both surface and groundwater.

Conservation 2000

A number of Illinois lakes are deteriorating in water quality, and more than $570 million in lake restoration and protection needs exist. A major effort to improve Illinois inland lakes began in 1990 with the establishment of the Illinois Lake Management Program Act. As part of the act, the Illinois EPA, along with other agencies and organizations, developed an "Administrative Framework Plan" which acts as a blueprint for future state activity in comprehensive lake management. The plan incorporates four major components: public education, technical assistance, monitoring and research, and financial incentives. The plan was signed into law by Governor Jim Edgar as part of "Conservation 2000" in June 1995. The Illinois EPA will receive a total of $7 million over six years to implement the recommendations in the Administrative Framework Plan. One of the major programs funded under Conservation 2000 is the "Illinois Clean Lakes Program" which offers matching funds for lake diagnostic-feasibility studies and implementation projects. Because of Conservation 2000, Illinois has one of a handful of state-funded, comprehensive lake management programs in the country.