The water levels of four Great Lakes are higher than they were one year ago, and all except for Lake Ontario should be at or above last year's levels by the start of the 2010 boating season, according to a six-month outlook issued on December 17 by the U.S. Army Corps of Engineers.
The Army report notes that Lakes Huron and Michigan are presently 10 inches higher than they were last year, while Lake Superior is up by four inches, and Lakes Erie and St. Clair are both one inch higher than 2008 levels. Lake Ontario is presently one inch below last year's level. The report goes on to predict that by May 2010, Lakes Michigan and Huron should still be higher than they were in May 2009, while Lakes Superior, St. Clair and Erie are expected to be at about the same level as the previous year.
Actual spring water levels will depend on a combination of precipitation and how much of the lakes' surface freezes over this winter, a factor that limits water loss by evaporation. Recent cold air has allowed ice to form on many protected areas of the lakes, reducing evaporation.
The Great Lakes have been slowly returning toward long-term averages after recording near-historic low water levels in the middle part of the decade.
Surface levels can have a significant impact on the cost of Great Lakes shipping – higher levels mean freighters can carry heavier loads. And shifts of just a few inches can mean changes of hundreds of feet on shoreline property and affect recreational boaters and tourism.