Update on Lake Superior Outflows and Expected Conditions

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 2900 cubic metres per second (m3/s) for the month of September, effective September 5th. The outflow is expected to exceed the combined capacities of the hydropower plants on the St. Marys River, which will be approximately 1970 m3/s in September, 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 will be maintained at its current position to start the month, but adjustments will be required in the latter half of September to facilitate a construction project that will involve installation of equipment to allow remote operation of Gates #11 to 14 on the U.S. portion of the structure. All U.S. Gates #9-16 will be closed starting on Monday, 18 September, and Gates #11-16 will remain closed throughout the
duration of the project. To offset the effects of the gate closures, additional water will be released by increasing the setting of most of the remaining gates to 127 cm open (Gates #2-8 on 18 September, Gates #9-10 on 20 September). Adjustments are expected to continue in October as the gate automation project proceeds. Note that sea lamprey trapping at Gate #16 has been completed for the season, and 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.

Anglers and other users of the St. Marys Rapids need to remain cautious of the relatively high and changing flows and water levels that will be experienced in the rapids in September. Some flooding of low-lying areas of Whitefish Island is expected to continue this month and some recreational trails and features in these areas will likely be inundated. Users are encouraged to use extreme caution.

The September outflow is 120 m3/s less 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 net water supplies to Lake Superior were above average in August. The level of Lake Superior rose 4 cm last month, while on average the lake rises 1 cm in August. The Lake Superior level at the beginning-of-September is 25 cm above average, 9 cm above the level recorded a year ago at this time, and 59 cm above its chart datum level.

The net water supplies to Lake Michigan-Huron were near average in August. The level of Lake Michigan-Huron fell 4 cm last month, which is the average decline in August. The level of Lake Michigan-Huron is 44 cm above its longterm average beginning-of-September level, 16 cm higher than it was a year ago, and 96 cm above its chart datum level.

The level of Lake Superior is expected to begin its seasonal decline in September, and the level of Lake Michigan-Huron is expected to continue its seasonal decline.

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 [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


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