Gate Changes on Tuesday, September 16, 2025

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 September 16, 2025. This action will compensate for reduced flow through one of the hydropower plants as a result of repairs that are requiring more time than anticipated at the beginning of the month.

Please note that as the gates are adjusted, outflows through the St. Marys River will fluctuate. Low-lying areas of Whitefish Island including recreational trails may experience flooding as the gates are increased. Please take extra caution when recreating and navigating the river and adjacent areas.

As reported in the news release issued September 4, the current gate setting is equivalent to two gates fully open. On Tuesday, September 16, Gates #7 through #11 will each be raised to 155 cm (61 in.). This setting is equivalent to approximately four gates fully open. Gates #2 through #6 and #12 through #16 will remain closed. Gate #1 will remain at its typical setting which supplies a flow of about 15 m³/s (500 ft³/s) to the channel north of the Fishery Remedial Dike. The St. Marys Rapids flow will increase from approximately 360 m³/s (12,700 ft³/s) to approximately 580 m³/s (20,500 ft³/s) after the gate adjustments on September 16.

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 regulation 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.