Jim Bruckbauer (left) and Larry Mohrs check the propeller on their boat after they hit something in shallow water near a boat ramp in Ellison Bay. Credit: John Klein

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Lake Michigan kissed its record low water level for October on one day last week, and federal officials now predict the world's fifth largest lake is likely going to plunge into never-seen-before levels in the coming months.

The U.S. Army Corps of Engineers reported on Monday that on one day last week, water levels were essentially at the lake's official record low for October, a monthly average that was set in 1964. The weekend rains brought a slight rebound of about an inch, though the long-term forecast calls for the level to continue dropping in the coming months into areas never seen since modern records began in 1918.

If the prediction holds, "We would tie the record low for November and December and then go below it from January through March," said Keith Kompoltowicz, chief of the Army Corps' watershed hydrology branch for the agency's Detroit district.

Water levels are tracked daily, though records are based on monthly averages. That means even if Lake Michigan dropped below its record low for October for a day or even a week, it would not be considered by the Army Corps to be a record low until the monthly average for October is tallied - and that average would have to be lower than the record set in 1964.

Water levels on the Great Lakes fluctuate seasonally by inches and by as much as several feet over a period of years, depending on long-term weather patterns. But marina operators, shoreline property owners and shippers have always been able to take solace in the notion that no matter how low the water looked, it wasn't any lower than during the record low months of 1964.

Below average for years

Lakes Michigan and Huron, which are actually one body of water connected at the Straits of Mackinac, have been below their long-term average since the late 1990s.

Weather patterns are a big driver in how much water is in the lakes on any given day, but so are humans. The St. Clair River, which is the main outflow for the lakes, has been heavily dredged over the past century, and that has increased the amount of water that can flow out of Michigan and Huron, into Lake Erie, over Niagara Falls and, ultimately, out to the Atlantic Ocean.

It's long been accepted that human manipulation of the St. Clair River dropped the long-term average of the two lakes by about 16 inches, but a recent study funded by the U.S. and Canadian governments reported that unexpected erosion in the St. Clair since the last major dredging project in the early 1960s cost the lakes an additional 3 to 5 inches from their long-term average.

That has prompted calls from conservation groups and property owners, as well as the region's mayors, for the governments of U.S. and Canada to begin exploring some type of remediation project in the St. Clair River to slow the flows and gradually restore the lakes to more closely match their historic averages.

Not everyone supports the idea. They contend it could have negative impacts on downstream lakes Erie and Ontario, and it could have severe consequences if record high water levels return. The record high was set in 1986, when Lake Michigan was about 6 feet higher than it is today.

Kompoltowicz said the Lake Michigan/Huron surface level last week was measured at 175.70 meters above sea level, about equal to the record low average in October 1964. The all-time average low for any month was recorded in March 1964 at 175.58 meters above sea level.

All lake level numbers are considered preliminary until final numbers for the whole year are posted in early 2013.