Two Great Lakes not falling as expected; See what happened with recent heavy rain
Oct 08, 2019 06:35AM
● By Editor
By Mark Torregrossa of mlive.com - October 8, 2019
With the fall season comes a usual lowering of the Great Lakes water levels. That didn’t happen this past month for two of the Great Lakes.
Lake Superior and Lake Michigan-Huron were higher on October 4 than September 4.
The U.S. Army Corps of Engineers says heavy rain over the Great Lakes in September halted the typical lowering of water levels in September for Lake Superior and Lake Michigan-Huron. If we look at the long-term average fall in water levels from September to October is 1.2 inches on Lake Superior and 2.76 inches on Lake Michigan-Huron.
Friday, October 4 data released by the U.S. Army Corps of Engineer forecasts Lake Superior rose one inch from September 4 and Lake Michigan-Huron rose two inches since September 4.
That water level rise may not sound like a large rise in water levels. If we look at what the lakes actually did versus the typical long term average water level fall, it’s a 2.2 inch swing on Lake Superior and a 4.76 inch difference from normal on Lake Michigan-Huron.
The U.S. Army Corps of Engineers rule of thumb is 800 billion gallons of water for each inch of water on Lake Michigan-Huron. The extra almost five inches in Lake Michigan-Huron represents an extra 3.7 trillion gallons of water.
The water levels for October 4 still have all the Great Lakes lower than the record highest level. Lake Superior is one inch below the record level. Lake Michigan-Huron is seven inches below the record October high. Lake Erie is five inches below record levels, and Lake Ontario four inches below record levels.
Even though two of the lakes bucked the trend in September, all of the Great Lakes are expected to continue their typical seasonal water level decline between now and November 4.
While it would be tough for lake levels to rise in fall and winter, any less-than-average fall sets us up for a higher start to the seasonal water rise which starts in March.
The U.S. Corps of Engineers water level forecast typically projects average precipitation amounts. If precipitation amounts turn out extremely abnormal, either wet or dry, the long-range forecast will be off.
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