Great Lakes levels on the rise
Lakes Michigan and Huron water levels have rebounded from their record low of a year ago, and United States Army Corps of Engineers hydrologists expect them to keep rising.
The snowy winter and wet spring of 2013 made for a rapid rise in lake levels, and this winter’s snow is expected to provide another boost, Corps of Engineers Detroit District’s chief of watershed hydrology Keith Kompoltowicz said. The two lakes, considered one because of their connection at the Straits of Mackinac, typically rise around a foot each spring and summer, but jumped by nearly 20 inches last year. That’s after breaking records for low water levels in December 2012 and January 2013.
“We had very low levels a year ago as a result of minimal snow the prior winter and much warmer water temperatures, which led to much more evaporation,” he said.
That drop was compounded by a dry spring in 2012, Kompoltowicz said. The following year was much the opposite: the winter of 2012-13 had more snow, leading into a soggy spring. The runoff from the snow melt and spring rains brought lake levels up to an average of 577.72 feet over the International Great Lakes Datum in July, according to Great Lakes Environmental Research Laboratory data. That’s measured in feet above a point at Rimouski, Quebec-roughly equivalent to sea level.
In December 2013, Lakes Michigan and Huron’s mean level was 577.33 feet above datum, according to provisional data from the Corps of Engineers. Compare that to 576.15 feet in December 2012, as lake levels dipped below a record low set in 1964.
The Corps of Engineers forecasts Lakes Michigan and Huron to rise to higher levels than last year. There’s plenty of snow around the Great Lakes, especially in the Lake Superior and Michigan-Huron basins, Kompoltowicz said, and there’s a chance for above-average precipitation through the rest of the winter.
“Our forecasts take into account that we have a good amount of snow on the ground, with the potential for more snow to come,” he said, adding another spring with above-average precipitation should lead to even higher water levels.
Even still, the lakes won’t come surging back to their old levels. Corps of Engineers forecasts show that even under the best-case scenario, Lakes Huron and Michigan will fall just short of their long-term average in June 2014. Mean levels were more than a foot below average levels in December.
“They’re likely to remain below average over the next six months, but again, they’ll be higher than we were a year ago,” he said.
While snowfall can boost lake levels, the best kind is from storms that pick up their moisture from outside the Great Lakes, Kompoltowicz said. Lake-effect snow can lower lake levels over the long term, since it takes moisture from the lakes that may end up soaking into the ground or running into inland lake basins.
Researchers also are looking into how ice cover affects lake levels, Kompoltowicz said. The popular theory used to be that ice-free lakes led to above-average evaporation during the winter.
“That’s not necessarily the case,” he said. “We have had winters with no ice cover where evaporation isn’t very much more than normal.”
The major factor is the difference between water temperatures and air temperatures, Kompoltowicz said. Arctic air, like what much of Michigan is experiencing right now, over relatively warm water causes above-average evaporation. At the same time, that cold air forms ice.