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Great water loss

Two of the Great Lakes have hit their lowest water levels ever recorded, the U.S. Army Corps of Engineers said Tuesday, capping more than a decade of below-normal rain and snowfall and higher temperatures that boost evaporation.

Measurements taken last month show Lake Huron and Lake Michigan have reached their lowest ebb since record keeping began in 1918, and the lakes could set additional records over the next few months, the corps said. The lakes were 29 inches (74 centimetres) below their long-term average and had declined 17 inches (43 centimetres) since January 2012.

The other Great Lakes — Superior, Erie and Ontario — were also well below average.

"We're in an extreme situation," said Keith Kompoltowicz, watershed hydrology chief for the corps district office in Detroit.

The low water has caused heavy economic losses by forcing cargo ships to carry lighter loads, leaving boat docks high and dry, and damaging fish-spawning areas. And vegetation has sprung up in newly exposed shoreline bottomlands, a turnoff for hotel customers who prefer sandy beaches.

The corps' report came as shippers pleaded with Congress for more money to dredge ever-shallower harbours and channels. Shippers are taxed to support a harbour maintenance fund, but only about half of the revenue is spent on dredging. The remainder is diverted to the treasury for other purposes. Legislation to change that policy is pending before Congress.

"Plunging water levels are beyond anyone's control, but the dredging crisis is man-made," said James Weakley, president of the Cleveland-based Lake Carriers' Association.

Kompoltowicz said the Army corps might reconsider a long-debated proposal to place structures in a river to reduce the flow of water away from Lakes Huron and Lake Michigan, which are connected.

Scientists say lake levels are cyclical and controlled mostly by nature. They began a steep decline in the late 1990s and have usually lagged well below their historical averages since then.

But studies have shown that Huron and Michigan fell by 10 to 16 inches (25 to 40 centimetres) because of dredging over the years to deepen the navigational channel in the St. Clair River, most recently in the 1960s. Dredging of the river, which is on the south end of Lake Huron, accelerated the flow of water southward from the two lakes toward Lake Erie and Lake Ontario, and eventually into the Atlantic Ocean.