Lake Michigan Diversion Accounting


Water Resources Development Act 1986


Beginning with the State of Illinois’ reversal of the flow of the Chicago River in 1900, the other Great Lakes states (Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania and Wisconsin) have been concerned about the diversions of Lake Michigan water out of the basin. Their concern has led to litigation and a series of Supreme Court Decrees, which have regulated the diversion since 1925. The 1967 Decree, modified in 1980, specifies the allowable diversion at 3,200 cubic feet per second (cfs). In accordance with the Supreme Court Decree modified in 1980 and the WRDA 1986, the district continues to hold the responsibilities of diversion accounting computations and diversion certification. The work involves flow measurement at Lemont, hydrologic modeling of the basin and diversion accounting computations.


Total Project Cost:

  $ 1,170,000

Federal Cost:

  $ 1,170,000

Non-Federal Cost:

  $ 0


The Chicago District has completed reports for Lockport Accounting up to Water Year (WY) 2015 and the 8th Technical Committee was completed in 2019. At the end of WY 2015, the State of Illinois’ cumulative diversion deficit was 4,699 cfs-years which is greater than - 2000 cfs-years, the maximum allowable cumulative diversion deficit specified in the decree.

All published accounting reports up to WY 2015 and the Technical Committee’s review reports can be accessed through the USACE Chicago District’s web site.