Studies at odds over water levels in Great Lakes
Two new studies have thrown everything we thought we knew about the missing water of the Great Lakes into question, again.
As often happens in big environmental conundrums, ordinary citizens are left wondering which computer model to believe.
And any measure that helps one part of the lakes is pretty much guaranteed to do harm to others up or downstream.
The lakes hold one-fifth of the world's fresh surface water. In the late 1990s, water levels fell sharply in Lakes Huron and Michigan, which are joined at the north end by the Straits of Mackinac. Docks and harbours were suddenly high and dry, and plants invaded former sand beaches.
Residents blamed dredging in the St. Clair River, which drains Lake Huron to the south. Too much dredging to let the big freighters through sucks out water, they claimed, like a bathtub with too big a drain.
A $17-million Canada-U.S. analysis eventually concluded the river is not over-dredged. But in recent days, two new complications came up:
On Thursday, the Sierra Club released an engineering study that says the official report underestimates the real drainage from the lakes by 200 tonnes of water every second.
If so, it says, there's far more water escaping from the central Great Lakes than Canada and U.S. governments are admitting.
On Friday, the International Joint Commission, the Canada-U.S. body advising both countries on the state of the lakes, reported on how to raise water levels Huron and Michigan.
It doesn't recommend either for or against the move, but notes that doing anything — or nothing — will have a chain reaction up and down the lakes and St. Lawrence River.
More water for one lake means less for another, it notes. For instance, the Port of Montreal is chronically short of water, and holding back water upstream would mean less water in the St. Lawrence.
"It is important to note that the impact of the unprecedented thirteen years of sustained low water levels on Lakes Michigan and Huron is significant and includes dried up wetlands and shallow, load-reducing shipping channels," the Sierra Club says.
"Wetland loss is negatively impacting aquatic life and allowing encroachment of the aggressive exotic phragmites reed causing further loss of habitat."
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