Lowering of the Illinois River - Supreme Court Ruling

In 1930, the United States Supreme Court hears a case filed by the States of Wisconsin, Minnesota, Ohio, Pennsylvania, Michigan, and New York against the State of Illinois and the Sanitary District of Chicago (281 U.S. 696). The issue involves the amount of water being diverted from Lake Michigan to the Chicago River and into the Illinois River. These states argue that the amounts should be reduced. The court rules the following:

• After July 1, 1930, the State of Illinois and Sanitary District of Chicago were to divert no more than an annual average of 6,500 cubic feet per second.
• After December 31, 1935, the State and Sanitary District could divert no more than an average of 5,000 cubic feet per second.
• The most significant reduction is to take place on December 31, 1938 when the annual average diversion could not exceed 1,500 cubic feet per second (Find Law Legal News and Commentary).

The limitation of diversion from Lake Michigan to1,500 cubic feet per second in 1938 results in a reduction of the water depths of the Illinois River. At Havana, for example, the depth of the water dropped 24 inches in the middle section of the river.