Whats draining two Great Lakes?
Written by Detroit News   
Sunday, 12 March 2006 11:03

The U.S. Army Corps of Engineers is disputing some key findings of a controversial report that claims the levels of lakes Michigan and Huron have been on a permanent decline for at least 44 years.

But the Corps is also calling for a detailed study of the apparent drop in those two lakes -- which scientists consider one lake system -- and a corresponding rise in Lake Erie over time.

Environmentalists are sounding alarms, and the International Joint Commission, a U.S.-Canadian governmental group charged with stewardship of the Great Lakes, also is pledging a thorough review.

Michigan and Huron have been steadily draining since a Corps of Engineers dredging project deepened the St. Clair River in 1962 -- and perhaps over a much longer period. So claimed the authors of the 2005 report.

Compiled for a Canadian homeowners association, it said man-made alterations may have set off unending riverbed erosion that lets water from the two lakes spill into Erie, the St. Lawrence Seaway and the Atlantic Ocean faster than it's replenished.

An irreversible drop -- nearly 3 feet in a century and more than expected since the last dredging -- has been costly for wildlife, commercial shipping, recreation and tourism, according to the authors.

Tim Eder, water resources director for the National Wildlife Federation, said officials should fast-track a government-sponsored inquiry.

"The amount being lost through the St. Clair River is far in excess of the Chicago Diversion or any other diversion that could be contemplated," Eder said. "We're making the drain bigger, water is going out faster to the ocean, and it's never coming back."

The Chicago Diversion is a connection built in 1890 from Lake Michigan through the Chicago and Illinois rivers for drinking water and navigation. It sucks more than 200 million gallons of water per day from the base of Lake Michigan and ultimately drains it into the Mississippi.

A key finding of the report is that lakes Michigan and Huron are continuing to go down while Lake Erie is rising. That's based on data tracking the three lakes' comparative levels since 1860.

Lakes Huron and Michigan were supposed to stabilize at lower levels following the 1962 dredging -- not continue shrinking.

The Corps said dredging probably created just part of the problem. The report's authors gave too little consideration to such other factors as rainfall and "crustal rebound" of the earth that has gone on since the region was freed from the weight of the ice-age glaciers that formed the lakes, the Corps said in a formal response.

"There could be a number of reasons why Lake Erie could be rising relative to Michigan and Huron," added Scott Thieme, chief of the Great Lakes Hydraulics and Hydrology Office in Detroit. "Everybody would like to get to the bottom of it and figure out what's going on with Lake Huron and what needs to be done."

The lake level reduction since the mid-1800s has been 32 inches, an amount 28 times the volume of Lake St. Clair, said report writer Rob Nairn. An "ongoing significant drop" since the 1962 dredging was masked by wet weather that caused high lake levels from 1970-98, he added.

His report only heightened concern for members of the sponsoring Georgian Bay Association, who had raised $200,000 to find out why the water has been lower for seven straight years along their far northern stretch of Lake Huron shore. They've watched wetlands disappear and, with them, fish and herons and other wildlife that used to be abundant.

"We think there's some urgency here," said Mary Muter, bay keeper for the association.

The chief evidence of erosion is a 60-foot-deep hole in the St. Clair River bottom near the Blue Water Bridge at Port Huron. The Corps of Engineers said the depression has shown up in data from earlier in the 20th century, but the study's researchers said it has grown longer and wider.

The hole is in an area where the Corps dredged out two feet of bottomlands to deepen the shipping channel down the middle of the upper half of the river from 25 feet to 27 feet. Part of a more extensive revamping of the Great Lakes system to accommodate oceangoing vessels from the St. Lawrence Seaway, the swath is 600-800 feet wide.

Thieme said that was but one of several alterations affecting water levels from the 1860s through the 1960s. There also was dredging to accommodate shipping in the 1930s and extensive sand and gravel excavating between 1915 and 1925.

Authors of the report, W.F. Baird and Associates Coastal Engineers, didn't blame the erosion on the Corps of Engineers because they aren't sure of all the causes. They said other factors could be sea walls built by property owners, shore erosion, wetlands filling and sand mining.

"We really haven't determined -- and I'm not sure if we ever will -- who's at fault," Nairn said.

While key findings are in dispute, they're of sufficient gravity to have gained the attention of the International Joint Commission.

Commission officials said they plan to investigate the Huron-Michigan water losses in the early years of a five-year look at policies governing lake levels. The $14.6 million study will start this spring if the U.S. and Canadian governments come up with the money.

 
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