The International Lake Superior Board of Control advises that the gate setting of the control structure at the head of the St. Marys Rapids is expected to be increased from an equivalent of five gates fully open to an equivalent of seven gates fully open on Wednesday, June 25th. Anglers need to remain cautious of the changing flows and water levels in the rapids on June 25th, and the increased and unusually high flows and levels that will be experienced thereafter. The gate movements will primarily affect water conditions in the main rapids, but additional water will overtop the Fishery Remedial Dike along the north side of the rapids, and may pose a hazard.
In addition, some flooding of low-lying areas of Whitefish Island is expected as additional gates are opened and flows increase. As a result, some recreational trails and features in these areas will likely be inundated and may sustain damage, and users are encouraged to use extreme caution. Batchewana First Nations officials recently met with Board representatives to discuss the flood risk that exists in these low-lying areas. Historically, flooding of lower portions of Whitefish Island has occurred regularly, though regulatory operations in the past century have reduced the frequency and extent of such inundations.
The seven gate equivalent setting will be achieved by further opening Gates #2 through #15 to a partially open setting of 94 cm (37 in.) each. In addition, Gate #16 at the Compensating Works structure at the head of the St. Marys River will also remain partially opened 5 cm (2 in.) to facilitate sea lamprey trapping. Trapping is expected to take place through August. There will be no change to the setting of Gate #1, which supplies water to the channel north of the Fishery Remedial Dike.
The Board, under authority granted to it by the International Joint Commission, continues to adjust outflows this summer to reduce the risk of impacts from high flows in the St. Marys Rapids. The Board last increased the gate setting of the control structure to an equivalent of five gates fully open on May 15th. Significant precipitation received since has resulted in Lake Superior levels rising to 16 cm (6.3 in.) above average. Lake Michigan-Huron levels are currently 14 cm (5.5 in.) below average. To reduce the risk of extremely high water levels on Lake Superior, and to minimize adverse effects of lower water levels on Lake Michigan-Huron, it is necessary to act now by increasing flow through the Compensating Works. Should wet conditions prevail, it may prove necessary to further increase the gate opening settings later this summer.
The Board will continue to assess conditions on an ongoing basis and will issue further announcements to keep the public informed.