Update on Lake Superior Outflows and Expected Conditions

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International Lake Superior Board Of Control

Several months of generally wet weather has caused Lake Superior water levels to approach historical highs.

The monthly mean level of Lake Superior in October was 183.81 m, the 4th highest on record (1918 – present) and the highest since October 1985. Water levels of Lake Michigan-Huron are also well-above seasonal averages. Lake Michigan-Huron’s mean October level was 176.87 m, the 15th 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 3,130 cubic metres per second (m3/s) for the month of November, effective November 3rd. The November outflow is as prescribed by Regulation Plan 2012 and is 920 m3/s above the November average (1900-present). The total flow is expected to exceed the combined capacities of the hydropower plants on the St. Marys River, which will be approximately 2,180 m3/s in November. 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 the current setting equivalent to approximately six gates open. During the week of November 27th, the gate setting is expected to be reduced in stages to allow for a gradual reduction in St. Marys Rapids flows and water levels prior to winter. 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 average St. Marys Rapids flow in November will be approximately 937 m3/s. Anglers and other users of the St. Marys Rapids need to remain cautious of the high and changing flows and water levels that will be experienced in the rapids in November. Flooding of low-lying areas of Whitefish Island is expected to continue this month and some recreational trails and features in these areas will be inundated. Users are encouraged to use extreme caution.

The net water supplies to Lake Superior were above average in October. The level of Lake Superior rose 1 cm last month, while on average the lake declines 3 cm in October. The Lake Superior level at the beginning-of-November is 33 cm above average, 20 cm above the level recorded a year ago at this time and the 2nd highest on record. The level of Lake Superior is expected to begin its seasonal decline in November.

The net water supplies to Lake Michigan-Huron were also above average in October. The level of Lake Michigan-Huron remained stable last month, while on average the lake declines 7 cm in October. The level of Lake Michigan-Huron is 49 cm above its long-term average beginning-of-November level, 24 cm higher than it was a year ago and the 11th highest on record. The level of Lake Michigan-Huron is expected to resume 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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