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Higher gate settings planned for St. Marys Rapids

The settings will be maintained this winter to minimize the impact of ongoing maintenance at the Canadian hydropower facility
2017-01-14 Whitefish Island DMH-11
File photo. Donna Hopper/SooToday

Higher than usual gate settings are planned this winter along the St. Marys Rapids.

The International Lake Superior Board of Control announced the decision on Friday with hope that it will minimize the impact of ongoing maintenance at the Canadian hydropower facility.

"The gates of the Compensating Works at the head of the St. Marys Rapids have been set to an equivalent of two gates fully open (Gates No. 6 through No. 16 partially open 26 cm (10 in) each)," a release noted. "A setting equivalent to one-half gate open (Gates No. 7 through No. 10 open 20 cm (8 in) each) is typically used during the winter months."

The Board anticipates that the total St. Marys River flow will be 2,060 m3/s (72.7 tcfs) in December, which is 350 m3/s (12.4 tcfs) less than the flow prescribed by Regulation Plan 2012.

The expected December flow deficit will add approximately 1 cm (0.4 in) to the water level of Lake Superior and reduce the water level on Lake Michigan-Huron by less than 1 cm (0.4 in).

In November, Lake Superior rose by 5 cm (2 in) and the lake-wide water level is 17 cm above the seasonal long-term average. It is 30 cm above the level it was a year ago.

The outlook for Lake Superior is that lake-wide water levels are expected to decline through the winter months. Depending on weather and water supply, Lake Superior may decline by as much as 14 cm in December.


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