Category:

Surface Water

Existing Water Supply Sources

Lake Michigan

Since the flow of the Chicago River was reversed in the early 20th century, water from Lake Michigan that is used in Illinois has been diverted to the Mississippi River watershed. That diversion is governed by a 1967 U.S. Supreme Court decree and a 1980 amendment. The 1967 decree limits the amount diverted to 3,200 cubic feet per second, averaged over 5 years. The 1980 amendment made technical changes to permit Illinois' effective use and management of the permitted diversion, increasing the averaging period to 40 years and adding a goal to reduce withdrawals from the Cambrian-Ordovician (deep bedrock) aquifer.

U.S. Supreme Court Decree (1967) (pdf ~25kb)

U.S. Supreme Court Amendment (1980) (pdf ~27kb)

Compliance Report: Court Decree & Allocation Program (pdf ~35kb)

Global Warming Here At Home: How is Lake Michigan Faring? (pdf ~1.1mb) -- Presented by Chief Derek Winstanley, Illinois State Water Survey, at the League of Women Voters "Climate Matters" Symposium in Glenview on October 20, 2007.

U.S. Army Corps of Engineers Lake Michigan Diversion Accounting Reports

Instream Flow Issues

NE IL Streams: Factors Affecting Distribution & Availability of Streamflow for Water Supply & Instream Needs (pdf ~1.5mb)
Presented by H. Vernon Knapp, Senior Hydrologist, Center for Watershed Science, Illinois State Water Survey, on May 22, 2007 at a meeting of the Northeastern Illinois Regional Water Supply Planning Group at Ryerson Woods, Deerfield, Illinois.

Potential Climate Change Impacts

Water Quality