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The Great Lakes Water Balance Introduction | Hydrological Information | Forecasts and Summary Diversions Chicago Diversion The canal system at Chicago draws water from Lake Michigan for water supply, navigation and to dilute effluent from various water reclamation plants. This water is diverted into the Des Plaines and Calumet rivers in the upper Mississippi River basin (figure 12). The total authorized annual diversion has varied historically, though it is has been set at an annual average of 3200 cfs (90.61 cms) since 1967. Actual annual flows have at times exceeded this amount, though since 1994 diverted flows have been reduced below 3200 cfs in an effort to maintain a long term average of 3200 cfs or less. The accounting system for the Chicago Diversion is maintained by the Chicago District of the US Army Corps of Engineers (USACE). The USGS measures all open channel Chicago Diversion flows and assures the quality of these data. Flows are measured using an acoustic Doppler current profiler, and then a velocity / discharge relationship is established. Flows through the diversion are based on these velocity / discharge measurements. The USACE Chicago District performs the diversion accounting analysis for each water year. For accounting purposes, diverted flows are considered to be a combination of direct water pumpage for municipal and industrial use, the actual diverted water, and diverted runoff that is prevented from flowing into Lake Michigan. All hydrologic diversion data are available from the Chicago District USACE in the annual reports titled, "USACE Chicago District, Lake Michigan Diversion Accounting Water Year XX - Annual Report." Other Diversions Two other major diversions of Great Lakes water also exist; the Welland Canal (figure 9) and the New York State Barge Canal (NYSBC, figure 10). The Welland Canal transfers significant amounts of water from Lake Erie to Lake Ontario and permits shipping around Niagara Falls. Diverted flows are also used for hydroelectric power generation. Welland Canal flows do affect the Lake Erie water balance by increasing the outflow. However, Welland Canal flows are generally considered part of Lake Erie outflow and are not treated the same as a diversion in water balance accounting. The New York State Barge Canal, which is comprised of Champlain, Erie, Oswego, and Cayuga-Seneca Canals, takes water from the Niagara River and returns all of it to Lake Ontario. This canal is used primarily for shipping. The New York State Barge Canal is relatively small, and does not affect the amount of water flowing out of lake Erie or into Lake Ontario. Therefore, the NYSBC is not significant to the Great Lakes water balance. Data relating to the Welland and New York State Barge Canals are reported alongside Niagara River flows and are dealt with in the connecting channels - Niagara River and Welland Canal section of this report.
References
This report is prepared by USGS in cooperation with the Great Lakes Commission.
The Great Lakes Commission is a multi-agency, multi-disciplinary, multi-faceted team approach to addressing the science and policy of a Great Lakes water management regime will produce such application-oriented products as a water use web site, updated annual water use inventories, ecological evaluations of the system, and an integrated binational role for future Great Lakes-St. Lawrence endeavors. Comments or questions about the Water Resources Management Decision Support System for the Great Lakes? Contact Thomas Crane at tcrane@glc.org
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