ASK TOM: Lake-effect snow and lake levels

Dear Tom,

The west shore area of Michigan has gotten a lot of lake-effect snow this winter. Could that snow, when it melts, help raise the near record-low lake levels on Lake Michigan, or is it a net zero if lake-effect snow is simply moisture drawn out of Lake Michigan?

–Elizabeth Clark, Chicago and Holland, Mich.?

 
Dear Elizabeth,

At best, it’s net zero because, as you suspect, lake-effect snow consists of moisture from Lake Michigan. Actually, it’s net minus because “net zero” implies that every drop of water released when the snow finally melts will find its way back to Lake Michigan. That’s obviously not the case; some water will evaporate, soak into the ground or “disappear” in other ways. More importantly, some lake-effect snow falls beyond the drainage basin of Lake Michigan.
and that its melt water heads to the Gulf of Mexico via the Mississippi River system.