The Chicago River is a major source of diversion from Lake Michigan.
Before the 20th century, the Chicago River flowed into Lake Michigan. Flow was reversed by the city in 1900 to flow out of Lake Michigan towards the Mississippi River. The great Lakes states created a consent decree in 1967 regulating Chicago River diversion that was later modified in 1980. Under the decree, the state of Illinois may not divert more than 3200 cubic feet per second from Lake Michigan. The 1980 modification allowed for use to be extended to additional communities.
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