Great Lakes Environmental Research Laboratory: October 10, 2014
This time of year is normally the season when Great Lakes lake levels begin to fall. Typically evaporation is greater than precipitation and runoff from rivers and streams. So there is normally less water going into Lakes Michigan, Huron, and Superior at this time of year. On Lakes Michigan-Huron July is typically the high water month. Lake Superior usually sees peak water level in July or August.
This year is different.
Lakes Michigan-Huron, and Lake Superior have continued to rise, even up to now.
Lakes Michigan-Huron have risen 3.1 inches since July. Normally those lakes would have dropped 2.8 inches since July. Lake Superior has risen 1.8 inches, while normally dropping 1.2 inches since July.
When we look at the current rise in levels on Lake Michigan-Huron versus the normal fall, we may have just gained almost six inches. In other words, if all of the rest of fall and winter go exactly normal, Lake Michigan-Huron will start next season’s water rise six inches higher than last spring. And that’s if everything is normal.
Lake Michigan-Huron is heading toward its peak water level in this month of October. If Lake Michigan-Huron peaks this month, it will be only the fifth time in the last 155 years the high water mark is in this fall month, according to the Great Lakes Environmental Research Laboratory.
Lake Michigan-Huron has never had its high water mark in November. If that happens, we really know we have a bizarre weather pattern.
Last weekend’s rain was big
In looking at the lake levels over the last seven days, Lake Michigan-Huron has risen 1.3 inches and Lake Superior 1.4 inches. The rise is due to the widespread heavy rain received late last week and this past weekend. Look at the rainfall map. All of the surface of Lake Michigan had over one inch of rain in the past week. Northern Lake Michigan had over three inches of rain on it. That’s a quick way to bring water levels higher.
The addition of 1.3 inches of water in Lake Michigan-Huron represents 1.4 trillion gallons of water. The 1.4 inches of new water on Lake Superior equals 770 billion gallons.
With another widespread rain system coming early next week, Michigan’s Great Lakes water levels should hold steady, or even rise more.