Image of St. Marys River Control Structures

Update on Lake Superior Outflows and Expected Conditions - June 2020


While conditions around Lake Superior were drier than average in May, conditions were again wetter than average on Lake Michigan-Huron, driven by a couple of significant rainfall events in the middle and at the end of the month. This has resulted in additional record-high water levels, which pose a continued risk of shoreline damages in the coming months.

Lake Superior rose 5 cm over the course of the month, while on average the water level rises 10 cm in May. At the beginning of June, Lake Superior is 15 cm below the record-high beginning-of-month level set last year in 2019. The level is currently 26 cm above average (1918 – 2019).

Lake Michigan-Huron rose 10 cm over the course of the month, while on average the water level rises 8 cm in May. Lake Michigan-Huron is currently 13 cm above the previous record-high beginning-of-month level set in 1986. The level is 92 cm above average, and 18 cm above last year’s beginning-of-June level. 

ILSBC June 2020 Infographic

Water levels are expected to remain high over at least the next several months and further record highs are possible if wet conditions persist. 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.

The Board expects the total outflow to remain at 2,290 m3/s in June, as prescribed by Lake Superior Regulation Plan 2012. The outflow in June is just 100 m3/s above average and the lowest June outflow since 2013, which is in part a reflection of Plan 2012 adjusting to the relatively wetter conditions and higher levels experienced on Lake Michigan-Huron in comparison to Lake Superior in recent months.

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.

Shoreline businesses and property owners are reminded that the Great Lakes – St. Lawrence River Adaptive Management (GLAM) Committee continues to host an online questionnaire to allow for direct reporting on impacts related to recent high water conditions. The 2020 version of the questionnaire is now available: