Water Level Second Highest Ever; Ice Cover Up
Posted on: April 3, 2018

The Lake Superior Board of Control says that wet conditions returned to the Lake Superior and Lake Michigan-Huron basins in February and water levels remain well above average.  The monthly mean level of Lake Superior in February was 183.58 m, the 2nd highest on record (1918 – present) and just 5 cm below the record-high set in February 1986.  Lake Michigan-Huron’s mean February level was 176.74 m, the 12th highest on record and the highest since 1997.

National Oceanic and Atmospheric Administration:  Great Lakes Water Level Monitoring Stations

The Board says that the high levels coupled with strong winds and waves have resulted in shoreline erosion and coastal damages across the upper Great Lakes system.  They point out that additional shoreline erosion and coastal damages may occur this spring should active weather continue.

The Board says that Superior outflows have been maximized to the extent possible and are well about normal winter outflows. Additionally, all power plants on the St. Marys River have been directed to operate at peak capacity, thereby spilling more water from Superior.

The Board stresses that hydrologic conditions are the primary driver of water level fluctuations. They say that water levels of the Great Lakes cannot be fully controlled through regulation of outflows, nor can regulation completely eliminate the risk of extreme water levels from occurring during periods of severe weather and water supply conditions.


Lake Superior Ice Cover
Lake Superior Ice Cover on March 30th, 2018. Photo: National Oceanic and Atmospheric Administration — Great Lakes Environmental Research Laboratory

Information posted by the National Oceanic and Atmospheric Administration — Great Lakes Environmental Research Laboratory indicates that Lake Superior ice coverage is up this winter. Mid-March ice cover stood at 50% on Lake Superior. This is 10% greater than the long-term average for mid-March. The average thickness in mid-March was 5.5 inches.

At the beginning of February, only 15% of Lake Superior was covered by ice, rising dramatically to 77% by the middle of the month. This is close to double the long-term average for that period in February.

Ice coverage has fluctuated substantially since February, although staying in a range between 50 and 75% coverage until very recently. Change can be as much as 10% in 24 hours.

If you live at, or near, a particular bay or cove on Lake Superior and are seeing solid ice, conditions across the entire Lake can be much different. At the beginning of April, ice coverage on Superior stood at about 25%. Over this winter, Lake Superior exceeded the expected maxim ice cover of 68%.


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