Lake Huron & Lake Superior Shrinking

Muter is part of the Georgian Bay Association, a group of cottagers that point to the St. Clair River as the problem. They say that since it was last dredged in 1962 to make way for bigger boats, it has been eroding and draining extra water from Lake Huron to Lake Erie. So what else could be behind Lake Huron's dramatic drop? Some say the lakes are just doing what they've always done – rising and lowering in cycles. "We've had three decades of really wet conditions, so a lot of development has taken place and people got accustomed to the high water levels," says David Fay, manager of Environment Canada's Great Lakes-St. Lawrence regulation office in Cornwall. Others think this is a new, irreversible trend. One theory relates to precipitation. The lower Great Lakes, including Erie and Ontario, have benefited from tropical storms that have run north and dumped water on them. "But, (the storms) don't make it as far north or west to reach the upper lakes," says Cynthia Sellinger, a hydrologist with the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Lab in Michigan. Another theory points to the glaciers which, during the Ice Age, carved out the Great Lakes, pushing down land beneath their bottoms. Since then, most lakes have been gradually "rebounding" at different rates. And then there's global warming, which the International Panel of Climate Change says will lower the levels of all the Great Lakes with less consistent precipitation and greater evaporation in winter. The worst-case scenario calls for a 1.2-metre drop in the average level of lakes Huron and Michigan, says Fay. Then there are other aspects of the St. Clair River. Charts from 1867 show two large sand spits at the base of Lake Huron, pinching the head of the river. Back then, massive tongues of sand and gravel would regularly sweep down the river, moving 10 metres a year, slowing the flow of water, says Nairn. "These tongues are depleting," he says. "There is a lot less sand coming down the system now." If it gets to the point they are not being produced at all, the result would "be very dire, because the river would just get deeper and deeper," Nairn says. Regardless of what the IJC study group concludes, many people – including Michigan Governor Jennifer Granholm – insist the flow of water down the St. Clair River must be lessened. While Lakes Ontario and Superior have dams moderating the amount of water flowing from them, mitigating structures proposed for Lake Huron over the years were never built. Scientists unanimously agree that the dredging and mining of the St. Clair River over the past century has caused Lake Huron to drop by as much as 46 centimetres. The last dredging, which deepened the originally 6-metre-deep river to 8.1 metres, was approved in conjunction with plans for a series of underwater weirs, or speed bumps, which would slow the river's flow and result in a smaller loss of water. But, they were never built, as Roger Gauthier, program manager for the Great Lakes Commission, explains, because the dredging was soon followed by record-high levels of water on Lake Huron. ... http://www.thestar.com/article/273215

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