State of Wisconsin v. State of Illinois

Background

A dispute arose between the complainants and the defendants, the State of Illinois and the Sanitary District of Chicago, over how much water could be diverted from the Great Lakes–St. Lawrence system through the Chicago Drainage Canal. The causes were heard on pleadings, evidence, and reports of a Special Master, and the Court issued this decree to carry into effect the conclusions set out in prior opinions announced January 14, 1929, and April 14, 1930.

Reasoning

The Court addressed how much water Illinois and the Sanitary District could divert. It set phased caps: beginning July 1, 1930, an annual average cap of 6,500 cubic feet per second above domestic pumpage; December 31, 1935, a cap of 5,000 cfs; and December 31, 1938, a cap of 1,500 cfs, each in addition to domestic pumpage. The decree defines domestic pumpage as the water the City of Chicago draws into its mains and requires measuring diversion by subtracting city pumpage from flow at Lockport. The Sanitary District must file semi‑annual reports starting July 1, 1930, on construction and operation of sewage treatment plants and on average diversion. The Court retained power to modify the decree, to order further relief on application, and taxed costs against the defendants.

Real world impact

The decree directly restricts how much lake water Illinois and Chicago’s sanitation agency may take through the canal and forces construction and reporting on sewage treatment. The phased reductions give several years for adjustment but end with a substantial cut by 1938, and the Court will review progress through required reports and possible applications for further changes.