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Low water in North America’s Great Lakes causes worry

July 4, 2006

By Jonathan Spicer

TORONTO (Reuters) – Several massive vessels have run
aground on Michigan’s Saginaw River this shipping season,
caught in shallow waters a few miles from Lake Huron.

The river port is as shallow as 13 feet in a passage that
is supposed to be 22 feet deep, a sign of low water levels in
North America’s five Great Lakes — Superior, Michigan, Huron,
Erie, and Ontario.

Water levels declined in 1998 and have remained low,
forcing ships to take on lighter loads and sparking concern
about shorelines and wetlands in the Great Lakes, the world’s
largest supply of freshwater and a major commercial shipping
route for Canada and the United States. Iron ore and grain are
among the biggest cargoes shipped on the lakes.

“It’s a pretty different mindset to come off 30 years of
above-average water levels and to suddenly, since the late
1990s, have below-average levels,” said Scott Thieme, chief of
the U.S. Army Corps of Engineers’ Great Lakes Hydraulics and
Hydrology Office in Detroit.

Lakes Huron and Michigan, where water levels have declined
the most, are down about 3 feet (one meter) from 1997 and about
20 inches from their 140-year average, according to the U.S.
National Oceanic and Atmospheric Administration’s Great Lakes
Environmental Research Laboratory.

When homeowners on Lake Huron’s Georgian Bay noticed
wetlands were drying up, the Georgian Bay Association funded a
$223,000 report that last year concluded shoreline alterations
such as dredging and erosion in the St. Clair River, at the
bottom of the lake, were responsible.

In partial response, U.S. and Canadian governments approved
funding for a $14.6 million study of the upper Great Lakes by
the International Joint Commission, which resolves border
disputes and was denied funds for a similar study in 2002.

Depending on what it finds, the commission could recommend
changes to the amount of water that flows out of Lake Superior,
the first and largest in the chain of lakes.

NATURAL CAUSES?

Water levels in the Great Lakes have always fluctuated, but
experts point to climate change, dredging, private shoreline
alterations and even lingering effects of glaciers to explain
the latest changes — the decline of Lake Huron and slightly
higher water levels in Lake Erie, into which Huron flows.

The most controversial of several dredging projects was in
1962, when the U.S. Army Corps of Engineers deepened the St.
Clair River channel by 2 feet to accommodate commercial
shipping.

“When they dredge a river, it’s like taking a straw and
widening it,” said hydrologist Cynthia Sellinger, who helped
plan the upper Great Lakes study, which begins this summer.

U.S. and Canadian governments approved the 1960s dredging
on condition that submerged sills be built to compensate for
water lost from Lake Huron, and they started a series of
studies.

But by the time the studies were completed in the 1970s,
water levels in Lakes Huron and Michigan were at record highs,
and no one wanted sills that would raise levels even more.

Experts are unsure why water levels in the upper lakes rose
soon after the St. Clair River dredging. But they say that
major climatic events usually coincide with changes in water
levels.

The 1930s Dust Bowl drought coincided with then-record low
levels in the Great Lakes. And the most recent decline was in
1997, when a strong El Nino brought warm, dry temperatures to
North America, Sellinger said.

In addition, above-average temperatures since 1998 mean
less ice forms on the Great Lakes and the rivers that flow into
it, and more water evaporates away, Sellinger said.

And then there is something called post-glacial rebound, or
the slow rise of the earth’s crust, that could partly explain
declining water levels in Lakes Huron and Michigan.

“The area around Georgian Bay (Lake Huron) is rising faster
than the area around Lake Erie so it may be that the land has
just tilted and more water is flowing out,” Sellinger said.

DECLINING REVENUE

For every inch water levels go down, ships bound for
destinations outside North America forfeit about $8,400 in
freight revenue, said Dennis Mahoney, president of the United
States Great Lakes Shipping Association.

Saginaw and other ports have done emergency dredging to
accommodate ships and barges that can be hundreds of yards
long.

But Lake Superior’s largest American ships carried 3,000
fewer short tons of cargo last year than in 1997, when water
levels were 12 inches higher, according to the Lake Carriers’
Association.

“Obviously water levels are crucially important to this
industry, and we have been in a period of decline,” said Glen
Nekvasil, vice president of corporate communications for the
association.

“When you’re not utilizing your full vessel capacity you
can’t give your customer the best freight rate.”


Source: reuters



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