|ISWS Publications Series: Maps|| |
Click on a map's image to view a larger image of that map. Click on a map's title to view the pdf version of the map, if available. Some maps are not available directly through the web.
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
This map is available online as a 11" x 17" PDF file (450k).
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. To request a paper copy of the Major Watersheds of Illinois map from The Illinois State Water Survey,
please fill out this form. Copies are available free of charge until supplies run out.
Lambert Conformal Conic projection based on standard parallels 30° and 45°
This map is available online as a 26" x 38" PDF file (730k).
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 State Water Survey (ISWS) 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 the World Wide Web. For a copy, you will need to send a Letter of
Intent on your company's letterhead, stating why you would like 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 can fax it (217-333-4983 - Please include the web address/URL of this webpage on the FAX cover sheet) or mail it to:
Illinois State Water Survey
c/o Patti Hill
2204 Griffith Drive
Champaign, IL 61820-7495
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.
This map is available online as a 26" x 38" PDF file (6mb).
Community Water Supply Wells - Illinois has abundant buried groundwater reserves that supply millions of gallons of groundwater per day for public, agricultural, and industrial/commercial use.
These aquifers are unevenly distributed throughout the state. Fortunately, surface water or a combination of groundwater and surface water is available to meet required needs in most cases
where groundwater resources are marginal.
This map depicts community water supply wells in relation to the major aquifer systems in Illinois. A community water supply is defined as "a public
water system which serves at least 15 service connections used by residents or regularly serves at least 25 residents for at least 60 days per year." Only community wells classified as active
in the ISWS Public-Industrial-Commercial Survey database for the Year 2003 are shown.
This map is available online as a 28" x 40" PDF file (3.7mb).
|Examples of Other Survey Maps (Many more are available on our web site, and in our publications and brochures)|| |
1996 Peoria Lake Bathymetry - The bathymetric contours in this map were
derived from a triangulated irregular network (TIN) built using the Z values from the surveyed cross-section points.
Lambert Conformal Conic projection based on standard parallels 30° and 45°.
This map is available online as a 35" x 46" PDF file (3.1mb).
7-Day 10-Year Low Flow Maps - This site provides electronic copies of the paper maps
that are contained in Illinois State Water Survey contract reports ISWS CR 440,
ISWS CR 441, and
ISWS CR 545 . These maps provide
information on low flow conditions that might be expected to occur only during droughts (once in 10 years), and associated effluent
discharges, water withdrawals, and flow regulations for most Illinois rivers and streams. You may view and download the maps at the
7-Day 10-Year Low Flow Maps web site.
A 7-day low flow for a stream is the average flow measured during the 7 consecutive days of lowest flow during any given year. The 7-day 10-year low flow (Q7,10) is a statistical estimate of the lowest average flow that would be experienced during a consecutive 7-day period with an average recurrence interval of ten years. Because it is estimated to recur on average only once in 10 years it is usually an indicator of low flow conditions during drought.
2-Year 7-Day Low Flows - Taken from A Plan for Scientific
Assessment of Water Supplies in Illinois 2001, Illinois State Water Survey, Champaign, IL v, 22 p. : col. Ill, ISWS IEM 2001-03.
View and download a full text version of this publication:
Abstract Excerpt: Demand for water in Illinois is increasing, and water shortages in the Chicago metropolitan area have been projected. There are, however, limits to the availability of clean water at a reasonable cost. Limits to water availability are imposed by a number of factors including droughts, legal requirements to maintain minimum flows in rivers and streams, water recharge rates, and a decree of the United States Supreme Court limiting withdrawal of water from Lake Michigan. In addition, the specter of regional climate change could pose the greatest threat to Illinois water supplies over the long term: some projections show the possibility of persistent floods, whereas other projections show persistent droughts.
Additional sources of water do exist and can be tapped, but the cost of providing clean water increases with the necessity of water treatment, storage, and distribution, and the mitigation of impacts of new withdrawals on existing water supplies. Long lead times also are needed to construct major water projects. Unless the water supplies of Illinois are planned and managed in a comprehensive, regional, and visionary manner--based on the concept of renewable water supply capacity--water shortages could soon occur in some parts of the state. Water supply planning and management should be based on improved understanding and prediction of water supply and demand, and risk assessment.
The goal of this plan is to provide a framework for Illinois State Water Survey (ISWS) water supply programs and to document those studies that ISWS, working with others, needs to conduct to provide Illinois with comprehensive technical data and information, models, and training for water supply planning and management.
This map is available online as an 8.5" x 11" PDF file (450k).
Average Annual Snowfall -
Figure 3-32, left, is from Climate Atlas of Illinois published by the Illinois
Water Survey. The figure reports annual average snowfall for Illinois between the years of 1971 and 2000.
Excerpt: Annual average snowfall (1971-2000) ranges from less than 12 inches in the far south to 30 inches in central Illinois, and 40 inches in the
Chicago metropolitan area (Figure 3-32). Snowfall in the Chicago area is increased somewhat by occasional episodes of lake-effect snow (see Chapter 5). This
occurs when cold easterly to northeasterly winds move across the relatively warmer Lake Michigan waters, absorbing moisture and depositing it as snow along
the shore-line. Figures 3-33a, 3-33b, and 3-33c show average 1971 2000 seasonal snowfall for fall, winter, and spring, respectively. Fall snowfall is usually
light, with averages of less than 1 inch (south) to 2 to 3 inches (north).
Most annual snowfall occurs during the winter (December-February), with averages of 8 inches in the south to 30 inches in the Chicago metropolitan area.
However, snowfall also is common in early spring (March-May) with averages varying from less than 2 inches (south) to more than 6 inches (north). Snow in
May is a rarity.
Details about purchasing a copy of Climate Atlas of Illinois are available on our web site.
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 is available online as a 24" x 36" PDF file (800k).
View and download a full text version of this publication: http://www.sws.uiuc.edu/pubdoc/CR/ISWSCR2004-11.pdf
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The technical content of these maps is the responsibility of the author(s). The user assumes all liability for the interpretation and use of these maps.
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