Snow, ice cover could help lake levels
Written by The Muskegon Chronicle   
Tuesday, 12 February 2008 06:10

If winter has you signing the blues, consider this: Above average snowfall and brutally cold temperatures in recent weeks could keep Lake Michigan's sinking water level from hitting a record low this summer.

Above average precipitation in January and extensive ice cover on Lake Michigan caused water levels to rise three inches last month, according to the U.S. Army Corps of Engineers.

Great Lakes water levels typically drop in the fall and winter as surface water runoff decreases and evaporation increases; the lake's water level is still two feet below its long term average.

The water level rose as hydrologists were predicting Lake Michigan could dip below its record low water level this spring or summer. Now, some federal officials are predicting the lake's water level will be at least six inches above the record low, recorded in 1964, through August.

"If you have a hard winter with a lot of ice cover it means less evaporation; the ice acts as a lid on evaporation," said Cynthia Sellinger, a hydrologist at the National Oceanic and Atmospheric Administration's Great Lakes laboratory in Ann Arbor.

Ice currently covers about 40 percent of Lake Michigan's 23,000 square miles of surface area, according to NOAA monitoring data. Ice cover on the lake has increased dramatically since Jan. 24, according to NOAA ice charts.

The lake is far from freezing over but has much more ice cover than last year, according to government data. Lake Michigan last froze over in 1979, along with three of the four other Great Lakes: Huron, Superior and Erie.

The latest NOAA ice charts, which show extensive ice cover around the Lake Michigan shoreline, were based on data gathered before last weekend's deep freeze. Sub-zero air temperatures Sunday should add to the lake's ice cover and further reduce evaporation.

Adding to the lake's good fortune in January was above average precipitation. The amount of rain and snowfall in the drainage basins of lakes Michigan and Huron -- which are geographically one lake -- was 50 percent above average in January, according to Corps data.

The total volume of water flowing into lakes Michigan and Huron last month, which included water from Lake Superior, was 3.5 times above average, according to the Corps of Engineers.

Sellinger said ice cover on the water and snow pack on land surrounding the Great Lakes are the two main factors that determine summer water levels. She said it would be best for lake water levels if snow already on the ground stayed until at least March 15.

Most snow that melts in the middle of winter, when the ground is still frozen, evaporates before it flows into streams that feed the Great Lakes, Sellinger said.

"Even though we're getting quite a few more snow storms this year the snow isn't staying on the ground," Sellinger said. "If we have a thaw now, the only melting snow that will reach the lakes is snow near the edge of the lakes and streams."

The water level of lakes Michigan-Huron dipped below the record low for one day in December. But that one day reading didn't constitute a new record because it wasn't the average water level for the month.

Though this winter has been colder and produced more snow than last winter, average air temperatures to date have been about 1 degree above the long-term average, said Bill Marino, a National Weather Service meteorologist.

"Temperatures have been significantly cooler than last year, by about 2.2 degrees, but we're still warmer than normal," Marino said.

He said a strong La Nina effect, caused by shifting currents in the Pacific Ocean, created optimum winter conditions in the Great Lakes region. Translation: Above average snowfall. Muskegon's snowfall this winter, as of Monday, was 79 inches, according to the weather service.

"Because of the strength of La Nina, it's not allowing the jet stream to move," Marino said. "So the storms keeping coming over the same place. It's like a train that keeps going down the same tracks."
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