Water level predictions illustrates Great Lakes’ complexity

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Capital News Service
LANSING — Recently released Great Lakes water level predictions have Superior, Michigan and Huron on the same page.
But lakes Erie and Ontario flow to the beat of a different drum.
The National Oceanic and Atmospheric Administration and the U.S. Army Corps of Engineers predict that the bigger lakes will drop below the level they were a year ago. Erie and Ontario are set to be higher than a year ago.
How does that work?

“Over the summer and early fall of this year, water supplies to Lake Superior and Michigan-Huron were near average or below average,” said Lauren Fry, a civil engineer for the U.S. Army Corps of Engineers Detroit District. “Outflows, however, have been above average, due to higher than average water levels on both lakes.”
The high levels of the upper lakes are the legacy of the last two winters, which were so cold and snowy that they set the stage for low evaporation and high spring runoff. Those levels mean that outflow, or discharge, to the St. Marys River and to the St. Clair River and Detroit River system will be higher than typical.
With less water coming in than going out, lower water levels are expected for Superior and Michigan-Huron. This winter is also expected to be warmer, which may contribute to lower levels than last year.
Lakes Erie and Ontario just have to be different.
Both lakes can thank heavy June precipitation for higher levels than last year, Fry said. Lake Erie experienced precipitation 95 percent above the long-term average. Lake Ontario got 80 percent more. Both lakes rose rapidly throughout June and July.
“Only very dry conditions would result in levels below last year’s levels,” Fry said.
Because the Great Lakes have the largest surface area of any freshwater system on Earth, the lake surfaces, air and atmosphere interact in ways that uniquely impact the system’s water levels.
Typically, the lake levels fluctuate on a seasonal cycle, rising in spring, peaking in summer and falling in autumn. They fluctuate year to year as well, rising and falling to certain ranges for years at a time. But a number of factors can cause them to depart from the cycle.
Right now, water levels for all the lakes are at or above their averages for this time of year, following a rapid rise that began in 2013.
Marie Orttenburger writes for Great Lakes Echo.

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