What's draining two Great Lakes?

The Detroit News has this update on the sinking levels of Huron and Michigan:

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.

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.

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.

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.