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 2650 cubic metres per second (m3/s) for the month of June, effective June 4th. The June outflow is 250 m3/s more than the May outflow.
The June outflow is expected to exceed the capacities of the hydropower plants on the St. Marys River, which will be approximately 1898 m3/s in June. Most of the remaining flow will be passed through the control structure at the head of the St. Marys Rapids. However, the gate setting of the control structure for the month of June will be maintained at the existing setting of 14 gates partially opened 68 centimetres (cm) each, which is equivalent to five gates fully open.
As a result, the actual June flow is expected to be approximately 530 m3/s less than that prescribed by Plan 1977-A, the regulation plan for Lake Superior. The outflow of Lake Superior continues to be adjusted over the next several months to reduce the risk of unusually high flows expected in the St. Marys Rapids this summer. The Board requested and received approval from the IJC to temporarily deviate from Plan 1977-A to allow for these adjustments.
There will be no change to the setting of Gate #1 which supplies water to the channel north of the Fishery Remedial Dike.
The monthly mean water level of Lake Superior in May was 183.47 m. This is 12 cm above the long-term (1918-2013) May average and the highest May level since 1997.
This past month the net water supplies to Lake Superior were well above average. The level of Lake Superior rose 20 cm last month, while on average the lake rises 10 cm in May. The Lake Superior level at the beginning-of-June was 14 cm above average, and 32 cm above the level recorded a year ago at this time. It is 34 cm above its chart datum level. The level of Lake Superior is expected to continue its seasonal rise during June.
The net water supplies to Lake Michigan-Huron were also well above average in May. The level of Lake Michigan-Huron rose 16 cm this past month, while on average the lake rises 8 cm in May. The level of Lake Michigan-Huron is 17 cm below its long-term average beginning-of-June level, but 32 cm higher than it was a year ago. Lake Michigan-Huron is now 33 cm above its chart datum level. The level of Lake Michigan-Huron is also expected to continue its seasonal rise in June.
Mr. Jaymie Gadal is the Board Member for Canada. COL Robert Peterson is the Alternate United States 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 be found at the Board’s homepage: http://ijc.org/en_/ilsbc or on Facebook at: https://www.facebook.com/InternationalLakeSuperiorBoardOfControl