Six-month water level predictions illustrate Great Lakes complexity

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Ipperwash Beach, along Lake Huron. Photo via Wikimedia Commons.

Ipperwash Beach, along Lake Huron. Photo via Wikimedia Commons.

By Marie Orttenburger

Recently released Great Lakes water level predictions have Superior, Michigan and Huron on the same page.

But Erie and Ontario flow to the beat of a different drum.

The National Oceanic and Atmospheric Administration (NOAA) and the U.S. Army Corps of Engineers – Detroit District predict that the bigger lakes will drop below the level they were a year ago. Erie and Ontario are set to be higher than they were 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, civil engineer at 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 they set the stage for low evaporation and high spring runoff. Those levels mean that outflow, or discharge, to the St. Marys River and the St. Clair and Detroit River system will be higher than typical.

With less water coming in than is going out, lower water levels are expected for Superior and Michigan-Huron. This winter is also expected to be warmer, which may also 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.

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