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 2430 cubic metres per second (m3/s) for the month of June, effective June 2nd. The June outflow is 230 m3/s less than that prescribed by Regulation Plan 2012.
The Board recently requested and received approval from the IJC to temporarily deviate from Plan 2012. The outflow of Lake Superior will be adjusted over the next several months 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. To maintain more consistent flow conditions in the rapids and minimize the effects on both Lake Superior and Lake Michigan-Huron water levels, the Board expects that flows less than those prescribed by Plan 2012 will be released during periods of reduced hydropower flow capacity, and that these flow decreases will be offset by releasing flows greater than Plan 2012 during the months when no hydropower flow limitations are expected. At most, the differences in lake levels in any given month due to these changes are expected to be less than 2 cm on either lake, and cumulative differences are expected to be negligible by the end of November.
The June outflow of 2430 m3/s is expected to exceed the combined capacities of the hydropower plants on the St. Marys River, which will be approximately 1840 m3/s in June, and most of the remaining 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 June will be increased on Tuesday, June 6th from the current setting equivalent to approximately two gates open to a setting equivalent to approximately four gates open. This will be achieved by partially opening each of Gates #2 through #15 to a setting of 56 cm open. Anglers need to be cautious of the changing flows and water levels in the rapids on June 6th and the higher flows and levels that will be experienced in the rapids in June. 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 be set to 5 cm open to facilitate sea lamprey trapping.
Based on provisional data, the net water supplies to Lake Superior were above average in May. The level of Lake Superior rose 13 cm last month, while on average the lake rises 10 cm in May. The Lake Superior level at the beginning-of-June is 22 cm above average, 9 cm above the level recorded a year ago at this time, and 43 cm above its chart datum level.
The net water supplies to Lake Michigan-Huron were above average in May. The level of Lake Michigan-Huron rose 12 cm last month, while on average the lake rises 8 cm in May. The level of Lake Michigan-Huron is 35 cm above its long-term average beginning-of-June level, 3 cm higher than it was a year ago, and 86 cm above its chart datum level.
The levels of Lake Superior and Lake Michigan-Huron are both expected to continue their seasonal rise in June.
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 Jacob.Bruxer@canada.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