Just a year after warnings that the upper Great Lakes were too low, Lake Superior rose double its normal amount in May and now sits a half-foot above its usual June 1 level.
The International Lake Superior Board of Control reported Wednesday that unusually high water supplies to the lake led to an 8-inch rise in May, putting the big lake 6 inches above normal for June 1 and 13 inches above the level at this time last year.
Lake Superior also hit its highest May average level since 1997.
Lakes Huron and Michigan are continuing an even more remarkable comeback, from nearly 3 feet below normal and record low levels in recent years to just 7 inches below normal on June 1 this year. The lakes hit their all-time lowest mark in January 2013.
The lakes rose 6 inches during May, double their usual 3 inches, and now sit 13 inches higher than the June 1 level in 2013.
The rapid increase has been underway for about a year, reversing a decade-long trend of below-normal water levels.
The lakes are going up thanks to an unusually high water supply, mostly because of high inflow from streams that’s the result of a late and heavy snowmelt and persistent spring rainfall. There’s also more water in the lakes thanks to the long ice cover and cooler weather, reducing evaporation that increases during open water periods.
So much water is flowing out of Lake Superior now that the board of control has received special permission to adjust gates on the St. Marys River.
The board said, “The outflow of Lake Superior continues to be adjusted over the next several months to reduce the risk of unusually high flows expected in the St. Marys Rapids this summer.”
