Great Lakes drain away

Light snowfalls, dry summer leave Lakes Michigan, Huron near historic low levels

By James Janega
Tribune staff reporter
September 3, 2006,1,2724906,print.story

A decade of warm winters with sporadic snowfall has failed to refill the snow-dependent Great Lakes, with falling water levels bringing the top ever closer to the bottom in Lakes Michigan and Huron.

The ebb has raised cries to dredge harbors, cost lake freighters small fortunes and meant trouble for breakwaters, which can survive the fiercest storms but won't suffer exposure to the air.

As the lake floor unexpectedly peers up through shallow spots, experts and observers say the situation has offered a dramatic lesson in the ancient machinery that empties and refills the Great Lakes.

It is gravity, and in the lakes, it is working on a massive scale.

A billion years ago, North America tried to tear itself apart, and the leftover rift became the Great Lakes. Dying mountains and sprawling mud flats filled it with sand and shale.

A continentwide glacier tamped it down next, then filled what remained as it melted 10,000 years ago. That water has been replaced 100 times over, continuously shoved out by more recently melted snows.

The system is time-tested and works well, provided it's fueled properly.

When snows are small and sporadic, problems arise, said Scott Thieme, chief of Great Lakes hydraulics and hydrology for the Army Corps of Engineers in Detroit. Last winter's spotty snowfalls are a good example.

"It [was] just melting in pieces instead of one big slug in the spring," Thieme said. "We just didn't get a huge spring ride--it wasn't doing bad in the April-May time period, but it did suffer in the summer time period."

Not too long ago, the lakes were brimming with water. Levels sloshed far above average in 1986 and 1997 in Lakes Michigan and Huron--technically considered the same lake because they rise and fall together.

The snow that supplies them blankets forests in central Ontario and Interstate Highway 70 in western Ohio. From Minnesota nearly to Montreal, the land works to feed the lakes. Yet because the area is so big, the lower lakes sometimes live separately from the lakes upstream.

Lakes Ontario and Erie are flourishing at average levels this year, after a series of dying tropical storms dumped what was left of their water on them in 2005. Lake Superior, on the other hand, is in drought, as is northern Lake Michigan, and the upper lakes are suffering accordingly.

Dry summer didn't help

A dry summer exacerbated last year's mediocre winter, whose meltwater trickled out as quickly as it could sprinkle in. The disappointing result is a level at about the low reached in 2000--and not far from other historic lows in the 1960s and the Dust Bowl era.

As of late August--typically the high point of the lakes' annual swelling--Lake Michigan is 2 inches lower than it was two months ago. It's down 2 inches from 2005 and is 19 inches below its long-term average.

"It's just been waffling around the low point," said Cynthia Sellinger, lakes hydrologist with the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory in Ann Arbor, Mich. "Does it matter that the lakes are low? Yeah, it matters."

It matters to sailboat owners obliged to polish piloting skills around once-submerged sandbars, and to lake freighters running with partly empty holds to clear the bottom.

And around older harbors, like Chicago, the low water has brought an unexpected threat to the wooden pilings beneath breakwaters: rot.

"You would expect to develop problems after a big storm event, or after a major problem with ice," said Steve Hungness, chief of operations for the Army Corps of Engineers in Chicago. But mild winters make an unlikely and potent enemy.

The curving cement crescent most people think of as Chicago's breakwater is actually just a concrete cap. Beneath it, a 20-foot stack of lumber holds it up, vestiges of virgin Wisconsin and Michigan forests felled in the 1880s. Protected by rubble, it has rested in watery comfort, impervious to the elements.

Until now.

Low water since 2000 has let airborne bacteria flourish, weakening the wood and compromising the breakwall, Hungness said. Three 60-foot sections of the wall have dropped a few feet in recent years, and repairs are needed soon.

Smaller cargo ship loads

The menace for cargo ships is not air, but fear of grounding. Thousand-foot freighters now move so nerve-rackingly close to the bottom that crews aren't loading them as full.

"Every inch we lose, we would lose 120 tons of cargo capacity" to make it down the St. Lawrence Seaway, said Dennis Mahoney, president of the United States Great Lakes Shipping Association. The lost cargo's value translates to between $6,000 and $12,000 per voyage, he said.

A pinch is also felt for carriers on the upper lakes, said Glen Nekvasil, vice president of the Lake Carriers' Association. Loads are being reduced by 500 tons to navigate locks between Lake Superior and Lake Michigan at Sault Ste. Marie.

Still, loads bring the massive ships to within inches of the bottom at the locks and in destination harbors.

In harbors, marina managers say shallower spots have been closed or rented for inflatable dinghies and jet skis. Wilmette workers have had to move boats around, and boat owners have paid to dredge the harbor twice in the last year.

In Saugatuck, Mich., yachtsmen leery of a sandbar in Lake Kalamazoo have taken to following the Star of Saugatuck--the theory being that if the paddle-wheeler can make it, they can. Only a few have gotten stuck in a lake that locals are convinced can be navigated on foot if one knows where to walk.

It all boils down to one visceral and unforgettable image--an up-close look at what long has lain beneath. It's the bottom, they say, and they shudder.

"It's mucky. It's silty," said Wilmette Harbor Association Executive Director Sabine Herber, whose north suburban marina is often at odds with Lake Michigan and its moods.

"Eventually, it's a clay bottom," she said. "But there's a lot of muck on top of that."

Copyright © 2006, Chicago Tribune

Informant: binstock


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