Lake Superior Outflow & 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 3110 cubic metres per second (m3/s) for the month of October, effective October 3rd. The October outflow will be released by discharging about 2320 m3/s through the three hydropower plants and passing most of the remaining flow through the control structure at the head of the St. Marys Rapids.

The gate setting of the control structure will be reduced to the equivalent of approximately five gates open on October 3rd. As a result, the flow and water levels in the St Marys Rapids are expected to decrease from those experienced last month, but will remain relatively high throughout October. Anglers are advised to continue to be cautious of the high flows and levels in the rapids during October. The five-gate equivalent setting will be achieved by fully closing Gate 2 and maintaining Gates 3 to 15 at their partially open settings of 80 centimetres (cm) each. Gate 16 will remain closed. There will be no change to the setting of Gate 1, which supplies water to the channel north of the Fishery Remedial Dike.

The October outflow is 280 m3/s greater than that prescribed by Plan 1977-A. In April 2014, the Board requested and received approval from the IJC to temporarily deviate from Lake Superior Regulation Plan 1977-A to reduce the risk of unusually high flows expected in the St. Marys Rapids this summer. To offset some of the effects of releasing flows less than Plan 1977-A from June through September, flows greater than Plan 1977-A were released in May, and flows greater than Plan 1977-A are expected for the remainder of 2014, at which time the net effect on lake levels resulting from this deviation strategy is expected to be negligible.

The monthly mean water level of Lake Superior in September was 183.70 m. This is 17 cm above the long-term (1918-2013) September average and the highest September level since 1996.

For the eighth consecutive month, the net water supplies to Lake Superior were again above average in September. The level of Lake Superior rose 2 cm last month, while on average the lake declines 1 cm in September. The Lake Superior level at the beginning-of-October is 18 cm above average, 24 cm above the level recorded a year ago at this time, and 50 cm above its chart datum level.

The monthly mean water level of Lake Michigan-Huron in September was 176.51 m. This is 1 cm above the long-term (1918-2013) September average, the highest September level since 1998, and the first month that monthly mean levels have been above average since December 1998.

As was the case in August, the net water supplies to Lake Michigan-Huron were well above average in September. The level of Lake Michigan-Huron rose 2 cm this past month, while on average the lake declines by 6 cm in September. The level of Lake Michigan-Huron is 6 cm above its long-term average beginning-of-October level, 50 cm higher than it was a year ago, and 52 cm above its chart datum level.

The levels of both lakes Superior and Michigan-Huron are expected to begin their seasonal decline in October.

Mr. Jaymie Gadal is the Board Member for Canada. Ms. Deborah Lee is the Alternate 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
Or on Facebook at: https://www.facebook.com/InternationalLakeSuperiorBoardOfControl