Update on Lake Superior Outflows and Expected Conditions

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The International Lake Superior Board of Control, under authority granted to it by the International Joint Commission (IJC), has set the Lake Superior outflow to 3260 cubic metres per second (m3/s) for the month of August, effective August 4th.

The outflow is expected to exceed the combined capacities of the hydropower plants on the St. Marys River, which will be approximately 2310 m3/s in August, and the excess flow will be released through the control structure at the head of the St. Marys Rapids.

The gate setting of the control structure for the month of August will be maintained at the current setting equivalent to approximately five gates open. Gates #2 through #15 will be maintained at a setting of 84 cm open. There will be no change to the setting of Gate #1, which supplies a flow of about 15 m3/s to the channel north of the Fishery Remedial Dike. Gate #16 will remain at 5 cm open to facilitate sea lamprey trapping. Anglers need to remain cautious of the higher flows and levels that will be experienced in the rapids in August.

Some flooding of low-lying areas of Whitefish Island is expected to continue this month and some recreational trails and features in these areas will likely be inundated. Users are encouraged to use extreme caution.

The August outflow is 410 m3/s more than that prescribed by Regulation Plan 2012. The Board expects to continue to adjust the outflow of Lake Superior in accordance with the approved deviation strategy to accommodate expected maintenance at the hydropower plants and reduce the potential for adverse consequences of high and fluctuating flows and water levels in the St. Marys Rapids.

The net water supplies to Lake Superior were below average in July. The level of Lake Superior rose 1 cm last month, while on average the lake rises 5 cm in July. The Lake Superior level at the beginning-of-August is 22 cm above average, 5 cm above the level recorded a year ago at this time, and 55 cm above its chart datum level.

The net water supplies to Lake Michigan-Huron were above average in July. The level of Lake Michigan-Huron rose 3 cm last month, while on average the lake remains stable in July. The level of Lake Michigan-Huron is 44 cm above its long-term average beginning-of-August level, 17 cm higher than it was a year ago, and 100 cm above its chart datum level.

The level of Lake Superior is expected to remain stable in August, and the level of Lake Michigan-Huron is expected to begin its seasonal decline.


Mr. Jean-François Cantin is the Board Member for Canada. Brigadier General Mark Toy is the U.S. Board Member.

For further information, please contact Mr. Jacob Bruxer, Canadian Regulation Representative, International Lake Superior Board of Control, by phone at (613) 938-5862 or by e-mail at [email protected]

Additional information can also be found at the Board’s homepage: http://ijc.org/en_/ilsbc
Or on Facebook at: https://www.facebook.com/InternationalLakeSuperiorBoardOfControl

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