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 3020 cubic metres per second (m3/s) for the month of August, effective August 3rd.

The outflow is expected to exceed the combined capacities of the hydropower plants on the St. Marys River, which will be approximately 2338 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 will be increased on Thursday, August 4th, from the current setting equivalent to approximately three gates open to a setting equivalent to approximately four gates open. This will be achieved by partially opening each of Gates #2 to #13 to a setting of 74 cm open. Anglers need to remain cautious of the changing flows and water levels on August 4th and the higher flows and levels that will be experienced in the rapids in August. 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 #14 will remain closed to allow water level measurements to be collected, and Gates #15 and #16 will be closed now that sea lamprey trapping has been completed for the season.

The August outflow is 190 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 Board released flows greater than Plan 2012 in June and July, and expects to again in August, and release less than Plan 2012 in September through November.

The net water supplies to Lake Superior were above average in July. The level of Lake Superior rose 4 cm last month, while on average the lake rises 5 cm in July. The Lake Superior level at the beginning-of-August is 17 cm above average, 1 cm above the level recorded a year ago at this time, and 50 cm above its chart datum level.

The net water supplies to Lake Michigan-Huron were below average in July. The level of Lake Michigan-Huron fell 1 cm last month, while on average the lake remains stable in July. The level of Lake Michigan-Huron is 27 cm above its long-term average beginning-of-August level, 11 cm higher than it was a year ago, and 83 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. Jaymie Gadal is the Board Member for Canada. Mr. Stephen Durrett 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 Jacob.Bruxer@ec.gc.ca

Additional information can also be found at the Board’s homepage: http://ijc.org/en_/ilsbc

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