toledoblade.com --

The cold snap has been a blessing to the Great Lakes, because it has frozen much of the water south of Lake Superior and has sealed off the lower lakes from further evaporation at a critical time of year.

But officials are leery about the summer outlook, predicting an eight-inch decline in Lake Erie's water level this June and proportionate declines elsewhere.

They blame roller-coaster temperatures that led up to the recent blast of arctic-like weather, plus a long drought in the upper lakes that replenish Erie. The Great Lakes region had a relatively dry fall. Those in the region may have shoveled a fair amount of snow this winter, but, in some parts, much of what's fallen is viewed by hydrologists as a mirage because it was lake-effect.

That is snow formed by cold air masses that rob moisture from the lakes before they freeze over, Cynthia Sellinger, a National Oceanic and Atmospheric Administration hydrologist in Ann Arbor, explained. The lakes do not get that water back in a quick snow-and-melt cycle: Unless it is part of a snow-pack that thaws gradually, the stuff usually evaporates before it can replenish a water body, she said.

The good news to her and other Great Lakes watchers is that the evaporation cycle has been broken by the cold snap.

"Absolutely," Ms. Sellinger said. "[Having Lake Erie freeze] is the best thing that could have happened."

The bad news: The National Weather Service is predicting above-average temperatures and below-average precipitation in the coming months. If that proves to be true, she said, lake levels will invariably be lower than they were last summer - the only questions will be by how much and what effect that will have on recreational boaters and the shipping industry, both vital cogs to the region's economy.

"There could be a tremendous amount of boat repairs from boaters hitting old hot-water tanks and other debris that all of a sudden are in propeller range because the water level dropped," predicted Macomb County marina owner George Czeisperger.

Chuck Brockman, a Lake St. Clair boater for 50 years, said he copes with changing levels by reading charts more carefully and avoiding unfamiliar spots. "Experienced boaters will be OK. The newer boater will have to learn," he said.

Shippers must haul lighter loads when lake levels decline, which increases costs.

The driving force of the Great Lakes is Lake Superior, by far the deepest lake. It is so deep that its temperature fluctuates only a few degrees, despite its northern latitude.

Ray Assel, a NOAA physical scientist who has spent years studying Great Lakes ice patterns, said he cannot cite a single year in which Superior has formed a thick block of ice across the lake. "I would hesitate to say it ever freezes over completely," he said.

A lot of what happens to Lake Erie this summer depends on how much ice forms and snow falls in the upper Great Lakes the rest of the winter, he said.

"It's been very dry in the Michigan-Huron [lakes] basin the past six months," said Marie Strum, water resources engineer with the U.S. Army Corps of Engineers in Detroit.

This report includes information from the Associated Press.

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