About The Illinois State Water Survey

Statewide Maps

The Distribution of Water Use in Illinois

More than 1,300 communities in Illinois rely on different sources of water for municipal, industrial, and residential use. Sources of water throughout the state include Lake Michigan, inland surface waters such as rivers and reservoirs, groundwater, or a combination of sources. Communities may also purchase water from other communities or from public water distributors, which include private companies, water commissions, water districts, or water agencies.

This map depicts the complexity of where communities get their water and the network of water purchases throughout the state for the year 2012. Municipalities and public water distributors are colored-coded according to the source of water they use. The purchase network depicts transactions between communities or public water distributors with arrows going from seller to purchaser.

Some communities extract water from their own wells or intakes (withdrawn water), or buy water from another community or public water distributor (purchased water), or may have a combination of withdrawn and purchased water. In 2012, over 1,510 million gallons per day (mgd) were withdrawn for public consumption. Data for this map were gathered by the Illinois Water Inventory Program, which has tracked water use at high-capacity community wells and intakes (over 70 gallons per minute) throughout the state since 1979.

The Distribution of Water Use in Illinois map is available online as a 36" x 54" PDF file (7.2MB). An interactive map of this water use data is available online.

Center Pivot Irrigation in Illinois 2012 and 2014

This map displays center pivot irrigation systems in use in Illinois during the 2012 and 2014 growing seasons. There was a significant increase in irrigation use during 2013 and 2014, likely due to the drought in 2012. The saturated hydraulic conductivity layer represents soils with a value of ≥10 micrometers per second (3.6 centimeters per hour) in the upper 30 inches of soil, a value typical of sandy soils in Illinois. Saturated hydraulic conductivity is a measure of the ease with which water will move through a soil, and values typically increase with the sand content. Traditionally, irrigation is needed where sandy soils are present due to their low water-holding capacity and high hydraulic conductivity. This layer provides a general location for areas that are more likely to require irrigation for a successful crop. The majority of center pivot systems in Illinois are located in alluvial valleys where soils are sandy and where shallow aquifers are available to sustain high capacity wells. In recent years, seed corn contracts that require a guaranteed crop, as well as the positive return on investment for crops under irrigation, have expanded the use of center pivot irrigation.

The map of Center Pivot Irrigation in Illinois 2012 and 2014is available online as a 25.5" x 37.5" PDF file (16.5MB).

Countywide Vertical Datum Conversion Factors in Illinois

This map displays countywide, conversion values to adjust elevations from the National Geodetic Vertical Datum 1929 (NGVD 29) to the North American Vertical Datum 1988 (NAVD 88). Values indicated should be added to current NGVD 29 elevations (not displayed) to obtain the NAVD 88 elevation. Countywide values were calculated using the methodology outlined in the Federal Emergency Management Agency (FEMA) Guidelines and Specifications for Flood Hazard Mapping Partners Appendix B.

Point conversion factors were computed using the CORPSCON utility.

The Countywide Vertical Datum Conversion Factors map is available online as a 11" x 17" PDF file (450k).

Community Surface Water Supplies Year 2000

Community Surface Water Supplies Year 2000 - Community water supplies provide nearly 90% of Illinois’ citizens with water for residential use. The Illinois Environmental Protection Agency (IEPA) defines a “community water supply” as a public water supply that provides potable water to a minimum of 15 service connections used by year-round residents or regularly serves at least 25 year-round residents. The IEPA issues permits for operation of water supplies serving the public. Data from the Illinois Water Inventory Program (IWIP) show that 1998 total withdrawals by all public water supply systems exceeded 1,700 million gallons per day (mgd). Community systems withdrawing surface water accounted for 84% of those withdrawals, with Lake Michigan withdrawals exceeding 1,000 mgd. Other surface water sources include interstate rivers (Mississippi and Ohio), intrastate rivers (Fox, Illinois, Kankakee, Kaskaskia, and Little Wabash), and 96 reservoirs.

Due to Homeland Security issues, we can not freely distribute this map through our website. For a copy, please send a Letter of Intent on your company’s letterhead stating why you would like a copy of this map. This map is prohibited from being displayed publicly. Please include contact information, as we may call to verify the information. Upon receipt of the letter, it will be forwarded to the Survey Director for approval. You may fax it to 217-333-4983 (please include the web address/URL of this page on the FAX cover sheet) or mail it to:

Illinois State Water Survey
2204 Griffith Drive
Champaign, IL 61820-7495

Major Watersheds of Illinois 

This map illustrates general boundaries of major watersheds of Illinois. Shades of blue and green indicate watersheds in the Mississippi River basin. Watersheds with shades of green are located in the Illinois River basin. Shades of yellow and brown indicate watersheds in the Ohio River basin. The Cache River drains to both the Mississippi and Ohio Rivers. Drainage to Lake Michigan is in the Great Lakes basin. Its watershed is shaded pink. A watershed is often considered synonymous with drainage basin, and in this context it is the land area that directly drains to a common stream, river, or lake. Watershed boundaries follow topographic highs. Artificial drainage structures such as canals may convey water across topographic watershed boundaries in some areas shown. Features shown on this map are accurate to the scale at which they were originally developed. Communities are displayed as space allowed.

LaMBert Conformal Conic projection based on standard parallels 30° and 45°.

The  Major Watersheds of Illinois map is available online as a 26" x 38" PDF file (2.1MB).

Illinois River Watershed

The Illinois River watershed (shaded in light blue) is of vital importance to the state of Illinois. This large watershed covers 44 percent of the state and 90 percent of Illinois’ population resides within 55 counties wholly or partially included in the watershed. The Illinois River, one of the major tributaries of the Mississippi River, is part of the only inland waterway linking the Great Lakes to the Gulf of Mexico. The Illinois River watershed has a drainage area of 28,906 square miles or sq mi (75,156 square kilometers or sq km), of which approximately 3,058 sq mi (4,920 sq km) are located in Indiana and 1,070 sq mi (1,722 sq km) in Wisconsin. The watershed contains the drainage basins of several of the Illinois’ major rivers including the Des Plaines, Kankakee, Fox, Vermilion, Mackinaw, Spoon, Sangamon, and La Moine Rivers.

The  Illinois River Watershed map is available online as a 26" x 38" PDF file (6.2MB).

Examples of Other Survey Maps

Estimated Potential Yield of Sand and Gravel Aquifers

Taken from An Analysis of Groundwater Use to Aquifer Potential Yield in Illinois, Wehrmann, H. Allen, Sean V. Sinclair, and Timothy P. Bryant., 2003 Illinois State Water Survey, Champaign, IL, ISWS CR 2004-11. 

Abstract Excerpt: Proper water resource planning and management requires a firm understanding of water use and water resource availability. This report summarizes a comparison of Year 2000 groundwater withdrawals against estimated aquifer potential yields. The comparison is presented as a ratio of groundwater use (withdrawals) to groundwater yield (i.e., potential aquifer yield) on a township basis. Geographical Information System (GIS) technology was used to determine township yield ratios for three aquifer types (sand-and-gravel, shallow bedrock, and deep bedrock). 

This map of the Estimated Potential Yield of Sand and Gravel Aquifers is available online as a 24" x 36" PDF file (800k).