Lake Michigan Diversion Accounting Program

Chicago District
Published Jan. 9, 2024
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Background Information:

The diversion of water from the Lake Michigan watershed is of major importance to the Great Lakes states and to the Canadian province of Ontario. The states and province that border the Great Lakes have concerns with both diversions during periods of low lake levels, as well as the long term effects of diversion. To insure that the concerns of these interested parties are considered, the U. S. Army Corps of Engineers has been given the responsibility for the accounting of flow that is diverted from the Lake Michigan watershed.


An annual report is traditionally published once a year. The annual report will usually contain a diversion accounting report for one or more of the previous years, depending on when the diversion accounting data was ready to be reported. In addition to the annual report, a technical committee report is also published every 5 years.

Agency Responsibility:

The Corps of Engineers, Chicago District, is currently responsible for monitoring the measurements and the computation of the diversion of Lake Michigan water by the State of Illinois. In the past, other agencies have been responsible for this task; as a result, some of the reports presented on this website were not prepared by the Corps. For example:

  • The diversion accounting calculations for water years (WY) 1981 and 1982 were made for the Illinois Department of Natural Resources - Office of Water Resources (IDNR-OWR), formerly known as the Illinois Department of Transportation - Division of Water Resources (IDOT-DWR), by the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC), formerly known as the Metropolitan Sanitary District of Greater Chicago (MSDGC).
  • The computations for WY 1983, 1984, and 1985 were performed by the Northeastern Illinois Planning Commission (NIPC) for IDNR-OWR. The Corps reviewed, modified, and updated the WY 1984 and 1985 diversion accounting performed by NIPC.
  • The computations for WY 1986 were performed jointly by NIPC (under contract to the Corps of Engineers) and the Corps of Engineers. Computations since then have been performed solely by the Corps of Engineers, with the exception of those for WY 1991 and 1992 which were performed jointly with Christopher B. Burke Engineering, and those for WY 1998 and 1999 which were performed jointly with Mead & Hunt.
  • The diversion accounting reports for WY 2000 and WY 2001 were jointly produced by CTE (now AECON) and the Corps of Engineers.

    If you need reports from years not listed on this page, please contact the Public Affairs Office at and let us know what report you are looking for.