Researchers in Michigan report new evidence that water levels in the Great Lakes, which are near record low levels, may be shrinking due to global warming. Their study, which examines water level data for Lakes Michigan and Huron over more than a century, is scheduled for the Dec. 15 issue of ACS’ Environmental Science & Technology.
In the new study, Craig Stow and colleagues point out that water levels in the Great Lakes, which supply drinking water to more than 40 million U.S. and Canadian residents, have fluctuated over thousands of years. But recent declines in water levels have raised concern because the declines are consistent with many climate change projections, they say.
To evaluate the factors behind this decline, the scientists examined water level data for Lakes Michigan and Huron from 1860 to 2006, including precipitation, evaporation and runoff data. The results reveal an underlying gradual decline in water levels since 1973. This underlying drop may be due to an increase in evaporation levels, they say.
“We cannot be certain that the present observed water level drop is caused by factors related to global climate change, or that it portends a long-term problem,” the study states. But the ongoing decline in water levels make it “prudent to include lower lake levels in future management planning,” the researchers note.
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