Most of the Great Lakes saw their highest July monthly mean water level, and some of the lakes could also top those marks in August, according to the U.S. Army Corps of Engineers Detroit District.

Lakes Superior, St. Clair, Erie, and Ontario all eclipsed their averages for the month dating back to 1918, when record-keeping began, the Corps' data said. The latest figures follow lakes Erie and Ontario reaching their highest levels ever recorded this summer, thanks to months of abnormally wet weather keeping stream flows into the Great Lakes well above average. 

Superior’s mean was 603.22 feet, besting its record of 603.08 set in 1950, the army corp data shows. St. Clair averaged 577.56, above the 577.20 record set in 1986. 

Erie’s mean was 574.57, topping the 574.25 mark notched in 1986 and Ontario averaged 248.69, beating the 248.33 record reached in 2017.

Lakes Michigan-Huron averaged 581.92 feet in July, which came close to the record 581.99 set in 1986.

The records were broken, even with some of the Great Lakes reporting less precipitation than average last month, Army Corps data found.

“Lake Erie received above average precipitation at 110% of average. The rest of the lakes received less than average precipitation, at 73% to 85% of average,” its monthly bulletin said.

“While precipitation was below average, water supplies were near average for Superior, Michigan-Huron and Erie, and above normal for Ontario. The Lake Michigan-Huron basin and Erie basin predominately experienced above normal runoff, while Superior and Ontario experienced near normal runoff.”

In June, new record high monthly mean water levels were set on Superior, St. Clair, Erie and Ontario, the Army Corps said.

More records could be broken this month, as well.

“The current 6-month forecast indicates monthly mean water levels for August will meet or surpass record high August levels on Lakes Superior, St. Clair and Erie,” the Corps’ bulletin said.

The Corps' weekly update for Aug. 2 found that water levels continue to be “considerably above average” with forecast levels for Lakes Superior, St. Clair, Erie and Ontario for that period exceeding their record high August monthly mean levels by 1 to 6 inches. Lake Michigan-Huron’s projected level for Aug. 2 was 2 inches shy of its record high August monthly mean, the Corps’ report said. 

The lakes all were expected to begin their seasonal decline, but Erie's monthly mean level is projected to persist at record high levels for August and September before falling below record highs in October, according to a Corps summary.

The high water levels this summer coincide with concerns about damaged shorelines from Saulte Ste. Marie to western New York, and uncertainty as the water levels continually rise. Higher lake levels are a boon for the shipping industry, which only six years ago was complaining of low water levels. Higher water levels allow ships to carry more cargo through shallow passage areas.

But they come at the expense of eroding shorelines, which affect lakeshore residents and recreation. Around the Great Lakes, beaches have disappeared and docks have been submerged.

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