Update on Lake Superior Outflows and Expected Conditions

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International Lake Superior Board Of Control

Following wet conditions in October, drier and more seasonable conditions returned in November. Nonetheless, water levels of Lake Superior and Lake Michigan-Huron remain well above average. The monthly mean level of Lake Superior in November was 183.78 m, the 3rd highest on record (1918 – present) and the highest since November 1985. Lake Michigan-Huron’s mean November level was 176.85 m, the 12th highest on record and the highest since 1997. The high levels coupled with strong winds and waves have resulted in shoreline erosion and coastal damages across the upper Great Lakes system. Additional shoreline erosion and coastal damages may occur this fall and winter should active weather continue.

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 2,510 cubic metres per second (m3/s) for the month of December, effective December 4th. The December outflow is 100 m3/s more than that prescribed by Regulation Plan 2012. In consideration of the continuing high water levels in the upper Great Lakes and to accommodate expected maintenance at the hydropower plants in 2018, the Board recently received approval from the IJC to temporarily deviate from Plan 2012 this winter to continue to reduce the potential for adverse consequences of high and fluctuating flows in the St. Marys Rapids. Over the winter months, the Board will release slightly more flow through the control structure at the head of the St. Marys Rapids by maintaining a gate setting equivalent to one gate fully open instead of the typical winter setting equivalent to one-half gate open.

The gate setting of the control structure will be maintained at the current setting (eight gates open 26 cm each) which is equivalent to approximately one gate fully open. The gates were lowered to this setting over 28-29 November. 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.

The net water supplies to Lake Superior were below average in November. The level of Lake Superior fell 9 cm last month, while on average the lake declines 5 cm in November. The Lake Superior level at the beginning-of-December is 29 cm above average, 15 cm above the level recorded a year ago at this time and the 5th highest on record. The level of Lake Superior is expected to continue its seasonal decline in December.

The net water supplies to Lake Michigan-Huron were also below average in November. The level of Lake Michigan-Huron fell 6 cm last month, while on average the lake declines 4 cm in November. The level of Lake Michigan-Huron is 47 cm above its long-term average beginning-of-December level, 26 cm higher than it was a year ago and the 12th highest on record. The level of Lake Michigan-Huron is expected to continue its seasonal decline in November.


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

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