Rain barrel supplies list.
Gallons of water per square foot of roof.
If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year.
Or maybe a low pressure cell has been napping overhead and your arm is hurting from holding that umbrella while you watch your basement fill up with water.
To get an idea how much water the roof of your own house might yield use the rainfall harvest calculator above.
To calculate the runoff from any given rainfall.
Take a guess what is the volume of water that runs off a 1 000 square foot roof during a 1 rain storm.
Either way you would like to know how much rain has fallen how many gallons have come down from the skies onto your roof yard block or town.
Understanding how many gallons are within a square foot of water is useful in determining the amount of water required to fill a structure such as a pool or a pond.
So if they drain 23 million gal.
For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain.
When you look at the numbers it s surprising how much water you can collect every time it rains.
Take the dimensions of the footprint of your roof and convert them to inches.
The answer is about 623 gallons.
1 inch of water over a 5000 acre area equals 135 771 500 gallons.
So a 50 x 20 roof is 600.