Update on Lake Superior Outflows and Expected Conditions

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International Lake Superior Board of Control

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 2750 cubic metres per second (m3/s) for the month of October, effective October 2nd. The October outflow is expected to exceed the combined capacities of the hydropower plants on the St. Marys River, which will be approximately 2090 m3/s in October, and most of 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 in October will be reduced to a setting equivalent to approximately four gates open. This will be completed in stages on Tuesday, October 6th and on Wednesday, October 7th in order to accommodate St. Marys Rapids flow measurements. Anglers should continue to be cautious of the potentially hazardous flow and water level conditions in the St. Marys Rapids that will be experienced throughout the month. The four-gate equivalent setting will be achieved by partially lowering Gates #2 to #13 and #15 to a setting of 63 cm each. Gate #16, which was opened 5 cm to facilitate sea lamprey trapping this summer, will now be closed. 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, and Gate #14 will continue to remain closed to facilitate collection of field data measurements.

The October outflow of 2750 m3/s is 80 m3/s less than that prescribed by Regulation Plan 2012, in accordance with the Board’s approved deviation strategy. The Board continues to adjust the outflow of Lake Superior 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. Flows less than Plan 2012 were released in May and June of this year, and this was followed by flows greater than Plan 2012 being released in July and August. The Board again released flows somewhat less than Plan 2012 in September and expects to continue doing so through November.

The monthly mean water level of Lake Superior in September was 183.69 m. This is 16 cm above the long-term (1918-2014) September average, 1 cm lower than the September level last year. The net water supplies into Lake Superior were above average in September. The level of Lake Superior declined 2 cm last month, while on average the lake falls 1 cm in September. The Lake Superior level at the beginning-of-October is 15 cm above average, 3 cm below the level recorded a year ago at this time, and 47 cm above its chart datum level.

The monthly mean water level of Lake Michigan-Huron in September was 176.70 m. This is 20 cm above the long-term (1918-2014) September average, and the highest September level since 1997. The net water supplies to Lake Michigan-Huron were above average in September. The level of Lake Michigan-Huron declined 4 cm last month, while on average the lake falls 6 cm in September. The level of Lake Michigan-Huron is 20 cm above its long-term average beginning-of-October level, 14 cm higher than it was a year ago, and 66 cm above its chart datum level.

The levels of Lake Superior and Lake Michigan-Huron are both expected to continue their seasonal declines in October.

Mr. Jaymie Gadal is the Board Member for Canada. Brigadier General Richard Kaiser 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