Great Lakes levels plunge in February
Written by Muskegon Chronicle   
Tuesday, 13 March 2007 17:23

Water levels in Lake Michigan and Lake Huron dropped six times faster than average in February, a startling plunge that one expert attributed to the region's increasingly bizarre winter weather.

The lakes' water level dropped three inches in February, according to the latest data from the U.S. Army Corps of Engineers. On average, the water level in lakes Michigan and Huron -- which are technically one body of water -- drops a half-inch in February, according to data the Corps of Engineers has tracked over the past century.

The lakes are currently 16 inches below their long-term average for early March, according to federal data. Great Lakes water levels typically fall in the winter and rise in the spring, after the snow melts.

A combination of weather factors that caused water levels to drop in February could mean water levels on Lake Michigan will be lower this summer than in 2006, according to one government forecast. An earlier Corps of Engineers forecast called for Lake Michigan's water level this summer to be about two inches above last year's level.

"Unless we get an unusually large amount of rain from June through August, it's going to be another tough year for the shipping industry," said Cynthia Sellinger, a hydrologist at the National Oceanic and Atmospheric Administration's Great Lakes laboratory in Ann Arbor.

Water levels have dropped nearly four feet in Lake Michigan since 1998. That change is significant because lower lake levels drive up the cost of shipping and can make recreational boating more dangerous.

For each one-inch drop in Great Lakes water levels, freighters have to reduce their cargo by 50 to 270 tons to avoid running aground in shallow channels and harbors, said Glen Nekvasil, a spokesman for the Cleveland-based Lake Carriers Association.

"At the end of last season, when Lake Superior was near its all-time low, our largest ships were loading 10,000 tons below their rated capacity. That's a lot of cargo to leave at the dock," Nekvasil said.

Several weather-related conditions have driven down water levels in Lake Michigan in recent years, according to Sellinger. Among the factors:

* Above-average summer water temperatures in recent years kept the lake warmer during the following winters.
 Milder winters reduced ice cover on the lakes, which increased water evaporation during the winter.

* Warm lake water is more susceptible to evaporation during the cold winter months.

* When dry, cold air flows over the lake in the winter, draws more moisture out of the relatively warm water and triggers larger lake-effect snow showers.

* When snow melts before the ground thaws, most of the water evaporates and is lost from Lake Michigan. Under normal conditions, snow melts slowly in late March and April, is absorbed into the ground and slowly flows back into the lake.

One other possible factor: A 1960s dredging project in the St. Clair River has eroded the river bottom to twice the depth originally intended. Federal officials have estimated the project, which essentially opened a bigger drain hole in a river that lets out water from Lake Michigan and Lake Huron, has lowered water levels in those two lakes by a foot or more.

Sellinger said the weather conditions in West Michigan in February were ideal for evaporating huge amounts of water from Lake Michigan: Extremely cold air flowed over the lake, triggering lake-effect snow showers. That was followed by a sudden thaw that melted much of the snow before the ground could thaw and absorb the water.

"When you have cold air flowing over the basin, taking water out of the lakes and putting it onto the land (in the form of snow), and then you get a warm-up that causes that snow to melt and evaporate, that water is lost to the (Great Lakes) system. That's cause for alarm," Sellinger said.

Drought conditions in northern Wisconsin and the western half of the Lake Superior drainage basin also have contributed to lower lake levels in the last couple of years, according to Corps of Engineers officials.

Lake Superior's water level fell four inches in February, twice the average decline in winter. The lake is close to its lowest water level ever, recorded in 1926, said Carl Woodruff, a hydraulic engineer at the Corps' Detroit office.

Lake Superior's water level this summer could be as much as 8 inches below where it was last summer, Corps officials said. What happens in Lake Superior matters in West Michigan because the massive lake supplies a large quantity of water to Lake Michigan.

Though some lakefront property owners enjoy the larger beaches created by lower lake levels, shipping industry officials lament a trend that has hurt the industry for the past eight years.
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