How low will lake levels go?
Written by Ludington Daily News   
Monday, 14 January 2008 17:10

While many people are enjoying the winter warmup, it may not be the best of all conditions for the Great Lakes’ water levels.  Sure, there’s above-average precipitation feeding the lakes so far this month and that’s expected to continue through February. Ludington averages 1.15 inches of precipitation in January and has received .97 inches since Sunday.
But what happens if it gets cold like it usually does?

Last year, lakes Michigan and Huron lost about eight inches of water when arctic cold descended on the warm lakes. Actually, it happens every year, just not to that extent.

“To prevent evaporation, (you’d like) an ice cover that is allowed to form before large outbreaks of arctic air arrive,” said Keith Kompoltowicz, a meteorologist with the U.S. Army Corps of engineers. “Ice is like putting a top on a stovepot. It basically keeps the water in the lake rather than allowing it to be pulled into the atmosphere.”

Of course, Lake Michigan hardly freezes at all anymore. According to the Michigan Environmental Council, where Grand Traverse Bay once froze about 85 percent of the time, it now only freezes about 20 percent of the time. A Michigan State researcher analyzed 150 years of ice-cover records for West Grand Traverse Bay to come up with the figures.

Right now Lake Michigan is almost completely ice-free and is two feet below long-term average — just two inches above record lows. The Accuweather 15-day forecast calls for some single-digit temperatures in the next two weeks.

It might look like a recipe for disaster, but even with relatively warm lakes and little ice cover, Kompoltowicz is predicting the lakes will most likely stay above record lows through January and February and then pull away from the record lows of 1964 as the spring progresses.

Why? Because the NOAA Climate Prediction Center’s three-month forecast calls for above-average chances for above-average precipitation.

“Based on the conditions we’re expecting — and there were some forecasts calling for a wetter-than-average January, Michigan-Huron is still expected to stay two feet or so below its long-term average. The way it’s looking right now, it’s not looking like we’ll set a new record (for low water levels.),” Kompoltowicz said.

What would it take for the lakes to come up significantly?

Spring brings them up every year, but winter can dictate how much.
“For the lakes to start coming up what you need to see is a good snowpack in the wintertime and as that snowpack melts, runoff into the rivers combined with spring rainfall,” Kompoltowicz said. “That’s what really drives the lakes’ seasonal rise.”

At last weekend’s Sea Grant Regional Fisheries Workshop, Mark Breederland of the agency’s Traverse City office noted that on a graph of all-time lows and highs, very high lake levels seem to follow most of the historic lows.
“That just speaks to how dynamic the system is,” Kompoltowicz said. “All of the lakes have been much higher than they are now. Michigan-Huron has been lower than they are now.”

Another factor driving water levels in Lakes Michigan and Huron is Lake Superior’s water level. When Lake Superior is near a record low, the Lake Superior Board of Control, which is appointed by a joint commission of U.S. and Canadian agencies and interests, must disregard the lakes downstream and keep more water back for Lake Superior. The arrangement is dictated by a treaty that was originally with the government of Great Britain.

Earlier this year, Lake Superior touched a record low, but after a ridiculously wet fall, it’s back above its long-term average.
Should Lake Superior fall again, Lakes Michigan and Huron would again see their supplies from the north cut.

So far, local interests haven’t been affected to a point of distress — ships can still use the local commercial harbors as long as they receive their scheduled dredgings and the local rivers are still seeing good runs of salmon and fair runs of steelhead.
 
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