Following 15 years of generally dry weather, the four upper Great Lakes – Superior, Huron, Michigan and Erie – are all well above average. Lakes Huron, Michigan and Erie are at their highest levels for this time of year since 1998. Water levels on the Great Lakes rise and fall in response to natural water supplies and levels change from day to day. Outflows from lakes Superior and Ontario are regulated at dams approved by the International Joint Commission, allowing a limited degree of influence over water levels.
Lakes Michigan and Huron, connected by the Straits of Mackinac, rise and fall as a single lake. Lake Superior was near the upper end of its historical range during the winter, but did not rise as much as usual in April. The level as of May 3 is about 1 inch below its level from a year ago. The IJC’s International Lake Superior Board of Control expects Superior to remain above its long-term average the next six months, unless conditions are extremely dry. Regulated outflows from Lake Superior have been above average for the past six months and are expected to remain above average through the summer. Water levels as of May 3 on lakes Michigan and Huron were about 3 inches above their level at the same time last year. Levels are expected to remain above average the next six months, even under extremely dry conditions.