Gate Inspection at the Compensating Works Scheduled for May 23, 2023


Anglers and other users of the St. Marys Rapids, please be advised that the United States Army Corps of Engineers will be performing an inspection on the gates of the Compensating Works at the head of the St. Marys Rapids on Tuesday, May 23, 2023. These inspections are required every five years. Throughout the day, the inspection team will test and operate each gate at varying times. As a result, the flow in the rapids will continuously fluctuate between approximately 1,070 m3/s (37,800 ft3/s) and 1,210 m3/s (42,700 ft3/s), or the equivalents of approximately seven to eight gates fully open.

Once the inspection is complete, the gates at the Compensating Works will be returned to the position set in early May, equivalent to approximately eight gates fully open. Due to the temporary and sequential nature of the inspection, the total flow through St Marys River will remain at 2,890 m3/s (102,100 ft3/s) for the month of May.


The International Lake Superior Board of Control is responsible for managing the control works on the St. Marys River and regulating the outflow from Lake Superior into Lake Michigan-Huron. Under any outflow management plan, the ability to regulate the flow through the St. Marys River does not mean that full control of the water levels of Lake Superior and Lake Michigan-Huron is possible. This is because the major factors affecting water supply to the Great Lakes (i.e. precipitation, evaporation, and runoff) cannot be controlled, and are difficult to accurately predict. Outflow management cannot eliminate the risk of extreme water levels from occurring during periods of severe weather and water supply conditions. Additional information can be found at the Board’s homepage: or on Facebook at: