Lake Superior beach near Munising. Photo courtesy of Pictured Rocks National Lakeshore.

By Tanda Gmiter of Mlive.com - [email protected] - July 18, 2018

MARQUETTE, MI - Heavy rainfall over Lake Superior in the last month has sent 2.75 trillion gallons of additional water into the largest of our Great Lakes.

In a typical year, Lake Superior will see its water level increase by 3 inches between June 13 and July 13. This year, it rose by 5 inches during that window, according to the National Weather Service in Marquette.

"Several episodes of heavy rain impacted western portions of the Lake Superior basin since the middle of June, resulting in precipitation amounts of 6 to 10+ inches, or 150 to 300 percent of normal," the NWS said. 

"This heavy rainfall helped to raise the Lake Superior water level by 5 inches. This 5 inch rise equates to 2.75 trillion additional gallons of water added to Lake Superior in the last 30 days."

But looking at the big picture, Lake Superior water levels are still running below where they were last year at this time. Right now, the big lake is 4 inches lower than in 2017.

Lake Superior holds roughly 3 quadrillion gallons of water. And the water it takes in, it tends to hang onto.

Its water retention/replacement rate is anywhere from 173 to 191 years, by far the longest in the Great Lakes system.

What does this mean? A drop of water that fell into Lake Superior in 1827 is just making it to the St. Marys River this year, heading to Lake Huron.