How much rain is falling from the sky?

Posted on Jan-18-2017 at 19:26:00

We talk about how much rain falls in a given area all the time but how much water are we talking about?

Typically, rainfall measured in the United States is done in inches. And while this is certainly useful information, when you put a gallon number to the rainfall total it brings a new meaning to just how much rain has fallen!

Let’s start off by looking at how much rain (in gallons) falls on an acre of land. An acre is essentially the same area on a football field starting at the 10-yard line and ending at the goal line at the other end of the field.

If one inch of rain falls on an acre, it's equivalent to 27,154 gallons of water, according to the U.S. Geologic Survey.

While that may not seem like a lot, considering an Olympic swimming pool holds about 660,000 gallons of water, if we expand the area the total quickly adds up.

For example, the Phoenix valley is roughly 9,071 square miles in size. If one inch of rain falls over the entire Valley, it will total a remarkable 157,640,917,760 gallons of water! That is enough water to fill an Olympic swimming pool 238,849 times!

Given the fact that Phoenix averages about 8 inches of rain a year, that means on average the Valley receives 1,244,160,000,000 gallons of water per year. Yes… that is over 1 trillion gallons of water!

While that sounds impressive, a large portion of that water simply soaks into the ground or evaporates back into the atmosphere.