Update on Lake Superior Outflows and Expected Conditions


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 2800 cubic metres per second (m3/s) for the month of September, effective Sep 3rd. The September outflow is expected to exceed the combined capacities of the hydropower plants on the St. Marys River, which will be approximately 2030 m3/s in September, 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 September will remain at the existing setting equivalent to approximately five gates open, and 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 five‐gate equivalent setting will be achieved by maintaining Gates #2 to #13 and #15 partially opened a total of 76 cm each. 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. Furthermore, Gate #14 will continue to remain closed to facilitate collection of field data measurements, and Gate #16, which was opened 5 cm to facilitate sea lamprey trapping through June and July, will remain at this setting until a later date.

The September outflow of 2800 m3/s is 30 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 expects to release flows somewhat less than Plan 2012 again in September through November.

The monthly mean water level of Lake Superior in August was 183.68 m. This is 15 cm above the long‐term (1918‐2014) August average and the highest August level since 1997. The net water supplies into Lake Superior were above average in August. The level of Lake Superior remained about the same last month, while on average the lake rises 1 cm in August. The Lake Superior level at the beginning‐of‐September is 16 cm above average, 1 cm above the level recorded a year ago at this time, and 49 cm above its chart datum level.

The monthly mean water level of Lake Michigan‐Huron in August was 176.72 m. This is 17 cm above the longterm (1918‐2014) August average, and the highest August level since 1998. The net water supplies to Lake Michigan‐Huron were above average in August. The level of Lake Michigan‐Huron declined 2 cm last month, while on average the lake falls 4 cm in August. The level of Lake Michigan‐Huron is 18 cm above its long‐term average beginning‐of‐September level, 20 cm higher than it was a year ago, and 70 cm above its chart datum level.

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

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


  1. Up date:
    Well, September is half over and Lake Superiors water level did not go down as predicted by the Commission, it went up. I watched the shore caving in last night, wondering how much more erosion we can endure. No insurance will cover any of the damage to the homes, many of which have been here since the early 1900’s. Not many can afford the outlandish cost to place giant stone armourment which is the only type of shore protection allowed by the Michigan Department of Natural Resources. With November storms coming I don’t have much faith that anything can be done to help. I am very disappointed in Government!

  2. I find it interesting that the ILSBC , IJC are concerned that “ANGLERS” may have problems fishing while there is NO concern for the lakefront homeowners on Michigans Whitefish Bay who are losing their homes!
    Come on, let some water out!
    Have the shipping interests $$$$ gotten to you!

Comments are closed.