Upcoming Gate Adjustments on Wednesday, July 26


Anglers and other users of the St. Marys Rapids, please be advised that the gates of the Compensating Works at the head of the St. Marys Rapids will be adjusted on Wednesday, July 26, 2023. Gates #14 and #15 will be closed, Gate #16 will be lowered to a setting of 5 cm (2 in) and Gate #13 will be lowered to a setting of 86 cm (34 in). Gates #6 through #12 will remain partially open and Gate #1 will remain at its typical setting, which supplies a flow of about 15 m3/s to the channel north of the Fishery Remedial Dike. Overall, the gate setting will be equivalent to approximately five gates fully open.

On Wednesday, the flow through the St. Marys Rapids will decrease from approximately 1,200 m3/s (42,380 cfs) to 780 m3/s (27,500 cfs). At this flow, some low-lying areas of Whitefish Island including recreational trails may still be flooded. Users are encouraged to use extreme caution.

The goal of this gate movement and decrease in the St. Marys Rapids flow is to compensate for the increase in outflow through the Canadian hydropower plant. Major repairs have been completed and the outflow of the Canadian hydropower plant is returning to full capacity. Maximum flows also continue to be released through the two hydropower plants in the United States. The total St. Marys River flow is expected to be approximately 3,100 m3/s (109,480 cfs) for the rest of July.

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: https://ijc.org/en/lsbc or on Facebook at: https://www.facebook.com/InternationalLakeSuperiorBoardOfControl