What causes Lake Erie water levels to change?
A. About 80% of the water flowing into Lake Erie comes through the Detroit River from the Upper Great Lakes. As a result, the level of Lake Erie is determined primarily by precipitation in the watersheds of 5 states and 2 Canadian provinces that drain into the Upper Great Lakes and by evaporation from the surface of the Upper Great Lakes. The volume of water in the Upper Great Lakes and inflow to Lake Erie decrease during periods of lower precipitation and higher evaporation causing the level of Lake Erie to decline. Conversely, the volume of water in the Upper Great Lakes and inflow to Lake Erie increases during periods of higher precipitation and lower evaporation causing the level of Lake Erie to rise. Presently, above normal water levels in Lake Erie are the result of above normal precipitation. During the past 4 months precipitation has averaged above normal in the entire Great Lakes basin and more than 5 inches above normal in the Lake Erie basin. Long-term changes in lake level
