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Risk of Lake Superior shoreline erosion may continue through winter

Despite seasonal declines in lake levels, Great Lakes remain well above normal
2017-01-14 Whitefish Island DMH-11
File photo. Donna Hopper/SooToday

Lake Superior and Lake Michigan-Huron remain near record-highs for this time of year, and although they are expected to continue their seasonal declines in January, levels are expected to remain high over the next several months and may again exceed record-highs 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 weeks and potentially through the winter.

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 declined 4 cm over the course of the month, while on average the water level declines 8 cm in December.

At the beginning of January, Lake Superior is 2 cm below the record-high beginning-of-month level set in 1986. The level is currently 37 cm above average (1918 – 2018) and 9 cm above its level of a year ago. Lake Michigan-Huron remained relatively stable over the course of the month, while on average the water level declines 5 cm in December.

Lake Michigan-Huron is currently 4 cm above the record-high beginning-of-month level set in 1987. The level is 95 cm above average, and 44 cm above last year’s beginning-of-January level.

In early December, the Board received approval from the International Joint Commission to continue to deviate from Lake Superior Regulation Plan 2012 through this winter. A small amount of additional flow will be released through the St. Marys Rapids this winter to offset expected and potential unscheduled reductions in flows at the hydropower plants that often occur in challenging winter conditions.

This will be achieved by maintaining a gate setting equivalent to one gate fully open over the winter months instead of the typical winter setting equivalent to one-half gate open. Gates are typically maintained at a constant setting in winter to avoid issues with ice, including the potential for ice jams in the St. Marys River.

Additionally, the higher rapids flows from December through April provide an increase in wetted habitat for fish that have already spawned in the rapids or that may over-winter in this area. It is anticipated that this deviation will have a minimal impact on Lake Superior and Lake Michigan-Huron water levels.

In consideration of the above, the Board expects the total outflow to be 2460 m3 /s in January, which is 50 m3 /s more than that prescribed by Lake Superior Regulation Plan 2012. Actual outflows may vary depending on hydrologic and ice conditions, as well as maintenance activities or other unexpected outages at the hydropower plants on the St. Marys River.

Gates #5 through #12 will be maintained at a setting of 26 cm open (equivalent to one gate fully open) through the winter months. 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.