An Inch of Rain Equals

by Peter Geiger Updated: December 5, 2020

Natural disasters are never easy to handle but floods are particularly unforgiving and the long term recovery is difficult. In a perfect world we’d have just enough rain to handle our needs but that isn’t always the case. How much is enough rain anyway?

A week ago, parts of the drought ravaged South received an inch of rain. The media “complained” that it didn’t help replace the lost water. But, how much is an inch of rain??

An acre of ground contains 43,560 square feet. Consequently, a rainfall of 1 inch over 1 acre of ground could mean a total of 6,272,640 cubic inches of water. This is the equivalent of 3,630 cubic feet.

As a cubic foot of pure water weighs about 62.4 pounds, it follows that the weight of a uniform coating of 1 inch of rain over 1 acre of surface would be 226,512 pounds or about 113 short tons.The weight of 1 U.S. gallon of pure water is about 8.345 pounds. Consequently, a rainfall of 1 inch over 1acre of ground would mean 27,143 gallons of water.

So, an inch of water over an acre is a lot and spread out over the entire South it is rather significant. There is still tremendous need for water in the ground but it happens 1 inch at a time.