Snow And Ice Cover Will Boost Great Lakes Levels

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Great LakesTRAVERSE CITY, Mich.  — Water levels in the Great Lakes are expected to continue a steady recovery this year, courtesy of widespread ice cover that is slowing evaporation and snowfall that has approached record amounts in some cities, federal experts said Wednesday.

The siege of polar air that has gripped the region this winter has caused the most extensive freeze-over of the lakes since the record-setting year of 1979, when nearly 95 percent of their surface area solidified. On Tuesday, the ice cover reached its highest point since then – 91 percent, said George Leshkevich, a physical scientist with the federal Great Lakes Environmental Research Laboratory in Ann Arbor.

Meanwhile, the towering snowpack rimming the watershed will melt this spring and much of the water will flow into the lakes or the streams that feed them. The runoff is expected to be so bountiful that some areas will be in danger of flooding, a prospect that could be worsened by ice jams on swollen rivers.

Great Lakes levels dropped sharply in the late 1990s and have remained mostly below normal since. Scientists blame a warming climate, which promotes evaporation and limits ice cover, and occasional dry spells.

But the last 14 months have seen a long-awaited comeback, fueled by plentiful snow and rain. Superior and Michigan-Huron’s seasonal rises were almost double their average gains in 2013.

And the signs continue pointing upward. The snow’s water content is the highest in a decade on Lakes Superior, Michigan and Huron. The snowpack is the equivalent of 9.5 inches of water around Lake Superior. It holds 4 to 8 inches of water in the Huron-Michigan basin, 3.8 inches around Lake Ontario and 1.8 inches around Lake Erie.

Ice cover has prevented evaporation and could keep water temperatures cool enough to delay the next period of heavy water loss to the atmosphere.

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