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Great Lakes Outflows and Regulation

This page contains information on Great Lakes regulation, including Lake Superior outflow and compensating works gate settings, in addition to information on connecting channel discharge measurements and conveyance change monitoring.

Great Lakes Regulation

Serving as an international border between the United States and Canada, the Great Lakes are jointly regulated by the two countries. The International Joint Commission (IJC) is a bi-national organization established under the Boundary Waters Treaty of 1909 and is responsible for overseeing projects that affect water levels and flows across the boundary. Outflows from two of the five Great Lakes (Lake Superior and Lake Ontario) are regulated by water control structures. Outflows from Lakes Michigan-Huron and Erie are not regulated and are controlled exclusively by the hydraulic characteristics of their outlet rivers. The U.S. Army Corps of Engineers Detroit District provides technical support to the IJC for the regulation of Lake Superior outflows, measurements of connecting channel discharge, and conveyance change monitoring.  

Outflow from Lake Superior through the St. Marys River is regulated near the twin cities of Sault Ste. Marie, Michigan and Ontario. Water flows through a collection of structures that stretch across the river, including hydropower plants, navigation locks, and a gated dam at the head of the rapids known as the Compensating Works. The International Lake Superior Board of Control (ILSBC) was established by the IJC and maintains responsibility for setting Lake Superior outflows and overseeing the operation of the various control works. Lake Superior outflows are established on a monthly basis in accordance with the current regulation plan (Plan 2012).

Outflow and Compensating Works Gate Settings (IJC ILSBC) St. Marys Shippers Memo (Expected Monthly Flow Schedule) Additional Lake Superior Regulation Information (IJC ILSBC)

Outflows from Lake Ontario are established on a weekly basis by the International Lake Ontario-St. Lawrence River Board (ILOSLRB). The principal control structure is the Moses Saunders Dam. Lake Ontario outflow is set in accordance with the current regulation plan (Plan 2014). This mission is supported by the U.S. Army Corps of Engineers Buffalo District.

Additional Lake Ontario Regulation Information (IJC ILOSLRB)

Great Lakes Outflows

St. Marys Infographic
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The discharge of a river is defined as the volume of water flowing past a particular point in unit time. The U.S. Army Corps of Engineers collects flow data (discharge) in the connecting channels (the St. Marys River, the St. Clair River, the Detroit River, and the Niagara River) and the international section of the St. Lawrence River to develop and verify ratings for water level gauges, to analyze hydraulic structures, and to calibrate hydraulic models. Discharge data are also used operationally in navigation, hydropower production, lake regulation, water level forecasting, water apportionment, monitoring of compliance with agreements and treaties and in a wide range of studies.

Conveyance Change Monitoring

The St. Clair River is a naturally occurring dynamic river system which plays a role in conveying water from Lake Huron to Lake St. Clair and eventually Lake Erie. Any change in the shape of the river can influence the level of the Great Lakes.

Sediment entering the St. Clair River from Lake Huron, dredging the navigation channel, ice jams, and other natural processes can all result in changes to the rivers ability to move water through the system. The U.S. Army Corps of Engineers Detroit District monitors changes in the St. Clair River by measuring the shape, or bathymetry, of the river and computing how the changes affect the amount of water that can pass through the system.

Explore Great Lakes Water Management

This page contains monthly mean lakewide water levels (from 1918 to present) including long-term averages, maximums minimums, and monthly means. It also includes daily Great Lakes water levels and real-time gage data for connecting channels water levels. Water Level Data
Water Level Data
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Forecasts Forecasts
Forecasts
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Great Lakes water levels reaching peaks for the year Basin Conditions
Basin Conditions
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All Great Lakes Water Management data contained herein is preliminary in nature and therefore subject to change. The data is for general information purposes ONLY and SHALL NOT be used in technical applications such as, but not limited to, studies or designs. All critical data should be obtained from and verified by the United States Army Corps of Engineers Detroit District, Engineering and Construction Division, Hydraulics and Hydrology Branch, 477 Michigan Avenue, Detroit, MI 48226. The United States of America assumes no liability for the completeness or accuracy of the data contained herein and any use of such data inconsistent with this disclaimer shall be solely at the risk of the user.

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