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Water levels rise less than typical in April in Lake Superior

May 03, 2020 11:23AM ● By Editor

The St. Mary's River is the outflow of Lake Superior.  Photo:  Soo Today


From the International Lake Superior Board of Control - May 3, 2020


Conditions across the Great Lakes were generally drier this past month and the water levels of both Lake Superior and Lake Michigan-Huron rose less than they typically do in April.

Nonetheless, an exceptional volume of water remains in the system. Water levels are expected to remain high over at least the next several months and further record highs are possible if wet conditions return.

As a result, there will continue to be a significantly increased risk of shoreline erosion, lakeshore flooding and coastal damages over the next several months. The International Lake Superior Board of Control (Board) advises all those that may be affected to prepare for potentially severe coastal impacts, especially during periods of strong winds and high waves.

Lake Superior rose .78 inches (2 cm) over the course of the month, while on average the water level rises 2.75 inches (7 cm) in April. At the beginning of May, Lake Superior is 4.7 inches (12 cm) below the record-high beginning-of-month level set in 1986. The level is currently 12.2 inches (31 cm) above average (1918 – 2019) and 7 cm below the level recorded at this time last year.

Lake Michigan-Huron rose 2.3 inches (6 cm) over the course of the month, while on average the water level rises 4.3 inches (11 cm) in April. Lake Michigan-Huron is currently 3.5 inches (9 cm) above the previous record-high beginning-of-month level set in 1986. The level is 35.4 inches (90 cm) above average, and 10.2 inches (26 cm) above last year’s beginning-of-May level.

The Board expects the total outflow to be 2,290 m3/s in May, which is as prescribed by Lake Superior Regulation Plan 2012. The gate setting of the control structure will be maintained at the current setting equivalent to one-half gate fully open (Gates #7 through #10 each open 20 cm). 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.

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