There's too little data to say the problem is a product of global warming, he said. It's also a cycle that's been seen before.

Lake levels were nearly this low in December 1964, and it's the March 1964 record that's likely to fall in the next few months.

There is hope, he said. Records dating back to 1918 would seem to indicate a cyclical pattern that could well result in record lake levels in the next few years, he said. Such swings occurred in the 1970s and 1980s after similar low points.

Dredging backlog

But even if the water returns, what would appear to be a more intractable problem looms: Congress.

Groups with interests in the economy of the Great Lakes say Congress has failed to appropriate enough money to keep up with a growing backlog of dredging jobs needed to keep harbors clear for larger boats.

As a result, 17 million tons of sediment -- runoff from farms, mostly -- built up in harbors and other critical areas, said Glen Nekvasil, vice president of the Lake Carriers' Association, a trade association for commercial cargo interests.

Michigan Sen. Carl Levin has been pushing Congress to appropriate an unspent balance of nearly $7 billion in a trust fund designed to pay for such work, but to little avail so far -- much to the chagrin of interests along the lakeshore.

The fund takes in $1.6 billion a year, but only spends $800 million a year nationside, Nevkasil said.

"The money is there," he said. "They just need to use it."

Wasting Away

The concern about lake levels has even spread to Chicago's wastewater treatment program, where a spate of recent media coverage worried that declining lake levels could cause the heavily managed Chicago River to reverse its course and dump sewage into Lake Michigan.

Chicago's Metropolitan Water Reclamation District issued a press released Friday batting down the theory, saying it's just not possible for such a thing to happen.

But it could result in restrictions on river traffic as the agency works with the Corps to ensure problems with low oxygen levels in the river, the agency said in its release.

"We are not in a crisis at this time nor do we anticipate being in a crisis this year even if the drought should continue," the agency said.

Light loads

While the big deepwater ships that carry huge quantities of the nation's iron ore, coal and other goods are able to steam the deep waters of the Great Lakes as they always have, they must carry ever lighter loads to avoid grounding on the increasingly shallow harbors where they unload.

For instance, Nekvasil visited a ship Friday in Indiana Harbor, Indiana that's designed to carry 76,000 tons of iron ore. Because of low water levels and the harbors filing with silt, it can only carry 58,000 tons, he said.

As of now, light-loading is merely a matter of efficency, Nevkasil said. But that's in large part because the fragile economic recovery has not yet put a full burner under the nation's industry.

"We can meet demand now because the economy is not fully recovered," he said. "If demand for all of the cargo we move was at peak levels, we could not."