How much snowmelt? REALLY?

The Gratiot River Watershed contains 11,098 acres. All of the precipitation that falls within that acreage/ perimeter flows into the Gratiot River. Anything that falls outside ends up in different rivers and streams. (Asterisk: some is absorbed into the soil, some evaporates, some is used by vegetation, some goes into groundwater.)

When you start to calculate water volumes, the numbers are almost unbelievable. For example, 1 acre-foot of water (1 acre, 1 foot deep) contains 325,851 gallons!

One gallon of water weighs 8.34 pounds,. One cubic foot of water contains 7.48 gallons and weighs 62.4 pounds. But how much water is in snow? The rough rule is that 1" of rain = 10" of snow. For light fluffy lake-effect snow it might be 14". But even lake-effect snow melts and compacts over the season into dense snowpack. Plus in 2025-2026, we've had lots of heavy wet snow.

Right now, there is, conservatively, 3 feet of heavy wet condensed snowpack in the Keweenaw. Each cubic foot weighs around 35 lbs and therefore contains about 4.2 gallons of water.

Now for the fun math. One acre = 43,560 ft2. The snowpack is 3 feet deep (at least!). So the Watershed currently contains, in snow, 11,098 acres x 43,560 ft2 per acre x 3 feet deep = 1,450,286,640 ft3 of snow, with each cubic foot containing 4.2 gallons of water. SO, there are currently 6.1 BILLION GALLONS of water waiting to melt into the river in the next month or so. At least.

And every time it rains 1" (one inch!), another 300 MILLION GALLONS are added to the Watershed. The mind, it boggles!