Cold winter may aid lakes
Ice cap would prevent evaporation
and might stabilize water levels
December 4, 2001
BY DAN SHINE
of Detroit Free Press
A winter forecast for below-normal temperatures and
average precipitation for the Great Lakes basin may mean
an end to declining lake levels come spring.
Meteorologists at the National Oceanic and Atmospheric
Administration predict temperatures will be 5 degrees
below normal this winter, which would provide an ice cap
over the Great Lakes and Lake St. Clair.
The cap would prevent evaporation, one of the main reasons
for declining lake levels during the past four years.
The forecast covers the entire Great Lakes drainage basin.
"The last three to four years, we haven't had sufficient
ice cover," said Cynthia Sellinger, an NOAA hydrologist.
"Last year, the lakes got to their lowest points from
seasonal decline -- and then got lower because of evaporation."
Lakes can lose 1 to 2 inches of water a week from evaporation
during fall and winter, when the water is much warmer
than the air moving across the lakes. Predictions of average
precipitation for this winter do not mean that the lakes
will return to the levels they were before the decline
began. That would take several winters of heavy snowfall
and cold temperatures.
But an ice cap combined with average precipitation would
mean the lakes won't decline further and could possibly
rise in the spring, Sellinger said.
Lake levels have declined steadily during the past four
years, affecting shipping and pleasure boaters.
Lake Superior is 7 inches below its long-term average;
lakes Michigan and Huron are 16 inches below their average;
Lake St. Clair is 10 inches below its average; Lake Erie
is 8 inches below, and Lake Ontario is 2 inches below.