Lake Superior Feeling The Water Pinch

At first glance it's hard to believe Lake Superior could be said to be "disappearing." It's huge. But all along its 1,800-mile coast, you can see land where there used to be water, CBS News correspondent Cynthia Bowers reports.

"All these used to be under water," a police officer said while gesturing at pilings.

At 18 inches below normal, the lake looks different — above and below the water level. Ron and Jackie Polomski are being forced to move their boat from their old marina to one with deeper water.

"We know there is a cyclic up and down of the lake," Ron said. "I mean, history shows you that. But not this low."

Boaters are complaining.

"Two sailboats got hung up and needed to be towed — one guy ran through it and broke his props," boater Mitch Omer said.

But the real complaint comes from commercial shippers. Every inch the water falls forces the freighter fleet to drop another 8,000 tons of cargo. That adds up to a huge loss: $1.5 million annually per ship.

"A vessel is doing just the same amount of work with less tonnage, so they're less efficient." said Adolph Ojard, executive director of the Duluth Seaway Port.

At nearly 32,000 square miles, Lake Superior is the largest freshwater lake in the world. But over the last decade its levels have dropped nearly 2.5 feet — that's 16 trillion gallons of water just gone … enough to give 2,000 gallons or more to every man, woman and child on earth.

But water levels also are down across the entire Great Lakes Basin, and experts are racing to find out why.

Two big factors are a drought that is dumping 20 percent less rain into the lake, and warmer winter temperatures that mean less ice cover and more evaporation.

It's said that man changes levels by inches; Mother Nature by feet. The question is whether man is affecting nature.

"Within a couple of years, they should be rising again," said Doug Wilcox, ecologist and branch chief of the U.S. Geological Survey Great Lakes Science Center. "If they continue to go lower and lower, that would indicate to me that we're outside the bounds of the natural pattern."

Scientists hope it's just another cycle and that Superior will rise again. But with 16 trillion gallons to replace, it'll take time and patience on the part of those who live, and make a living, on this lake.