It's a sure sign that winter's nearly over: Debate begins anew on the value of the volume of water in the Great Lakes.

Think of Great Lakes as a giant liquid bank account -- an ice-age-old savings plan, but with only a 1 percent interest rate each year. And most of that is already being mostly used up by us for our own use (and some would argue misuse).

Then, imagine climate change continuing to dip deeper into that water volume savings (by evaporation) and realize that even 6 quadrillion gallons of water in five vast lakes shouldn't be touched to slake the thirst of the American Southwest if drought persists.

That's the opinion of a trio of water resources researchers, including an aquatic ecologist from Miami University (Ohio), in an article "Sentinels of Change," published in this month's Science magazine. The full study is available online and in print only by subscription.A review of one-page study in Science, provided to The Plain Dealer and cleveland.com by Ohio researcher Craig E. Williamson, says that "although they make up a small percentage of Earth's surface, lakes and reservoirs act as sentinels by providing signals that reflect the influence of climate change" on a broader scale.

"Lakes and reservoirs aren't often considered in climate change modeling, but they're actually the real hot spots -- for information about what happened in the past and what is happening now," Williamson said in a telephone interview Monday afternoon.

"They also give more clear signals about the changes that are happening than the oceans do," Williamson said.

The article also suggests that a climate-driven hydrologic imbalance led the connecting rivers and Niagara Falls to dry up more than 8,000 years ago, leaving the Great Lakes as separate basins -- and ecologically disastrous scenario we would do well to avoid, the researchers assert.

Williamson was joined on the project by Jasmine E. Saros from the University of Maine and David W. Schindler from the University of Alberta.

Schindler used the bank account metaphor in a recent story in the Montreal Gazette's online site. He warns against draining the lakes to "irrigate the Red River Valley and supply water to the dry American southwest."

Schindler says that Lake Superior, for example, is only renewed at a rate of about two-tenths of 1 percent each year, on average, leaving it vulnerable to withdrawals.

He also noted that there have been attempts to try to take water outside the Great Lakes basin.

Those attempts, of course, were made less likely in the future with the 2008 passage of the Great Lakes Water Compact

A series of stories by The Plain Dealer in 2008 chronicled the history of water grabs from the Great Lakes and laid out the options for water conservation and a new water economy.