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Study helps satellites to measure Great Lakes

Ohio State University engineers are helping satellites form a clearer picture of water quality in the Great Lakes. The study — the first ever to rate the effectiveness of various computer models for monitoring the Great Lakes — might also aid studies of global climate change.

As algae flourishes in the five freshwater lakes every summer, satellite images show the water changing color from blue to green, explained Carolyn Merry, professor of civil and environmental engineering and geodetic science.

When algae levels are too high, water takes on a foul taste and odor that isn’t easily removed by traditional treatment methods. Some forms of algae, such as one called microcystis, are toxic when consumed in large quantities. Though it can be filtered out of drinking water, microcystis can kill fish and birds, and coastal communities often have to ban swimming and water skiing in the summer when the algae blooms.

Computer models enable scientists to measure the color of light reflected from the water to gauge how much algae is present in a lake, and where. But the problem is all the available models of this type were originally designed for sea water, not lake water.

“They’ve got it down pat for the ocean,” Merry said of the various models developed by NASA and other agencies over the years. “But lakes are shallower and have different water conditions that affect the wavelengths of light collected by the satellites, so we can get erroneous measurements.”

Merry and master’s degree student Raghavendra Mupparthy reported the results of an initial study of Lake Erie May 25 in Denver at the meeting of the American Society for Photogrammetry & Remote Sensing. They determined which four of the top ocean models may perform well for studies of the Great Lakes.

Most scientists look for evidence of climate change in the oceans rather than in lakes, but that may change in the future, the engineers said.

“Lakes are important because they respond much faster to climate change than oceans do,” Mupparthy said.

The National Oceanic and Atmospheric Administration’s Cooperative Institute for Limnology and Ecosystems Research funded this study. Merry and Mupparthy have applied for funding to collect water samples from more sites, with the hope of customizing a model for Lake Erie.