Update on Lake Superior Outflows and Expected Conditions - April 2020
Wet conditions returned to the Great Lakes this past month and the water levels of both Lake Superior and Lake Michigan-Huron rose slightly more than they typically do in March. An exceptional volume of water remains in the system and all of the Great Lakes remain near or above record-high water levels for this time of year.
Water levels are expected to remain high over at least the next several months and further record highs are possible if wet conditions continue in 2020. 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 2 cm over the course of the month, while on average the water level declines 1 cm in March. At the beginning of April, Lake Superior is 2 cm below the record-high beginning-of-month level set in 1986. The level is currently 36 cm above average (1918 – 2019) and 4 cm above the level recorded at this time last year.
Lake Michigan-Huron rose 6 cm over the course of the month, while on average the water level rises 5 cm in March. Lake Michigan-Huron is currently 10 cm above the previous record-high beginning-of-month level set in 1986. The level is 95 cm above average, and 40 cm above last year’s beginning-of-April level.
The Board expects the total outflow to be 2,260 m3/s in April, which is as prescribed by Lake Superior Regulation Plan 2012. On Monday, 6 April, the gate setting of the control structure will be lowered from the current setting equivalent to one gate fully open to the equivalent of one-half gate fully open. Gates #5, #6, #11 and #12 will be closed and Gates #7 through #10 will be lowered to a setting of 20 cm open. 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.