National Wildlife Federation/ San Diego County

What is an Inch of Water?

Easy Water Conservation Strategy

What is "An Inch of Water"?

When it rains in San Diego, it usually
rains one to two tenths of an inch of water. That's only one to two ounces.
The November rainstorm, however, slowing the October firestorm, was over an inch of water and the runoff caused a lot of damage An "inch of water" is a term often used but seldom
explained. It is used by farmers to irrigate, by some home gardeners, and by the weather persons.

An inch of water is a liquid measurement, a linear measurement, and a measurement over time. It is a
measurement of how much water fell on each and every square foot of surface that it rained on during a 24 hour period. To demonstrate an inch of water, take a 12" by 12" baking pan and pour ten eight-ounce cups of water into it. It will measure one inch deep. An "inch of water" is 80 ounces of water. It weighs over five pounds.

If an inch of water were to fall from the sky at once, it would crush many structures and damage many plants. Water is heavy, as any veteran who every carried a five gallon G.I. water can attest. On a single home of 1500 square feet, for example, an inch of rain will drop over six gallons of water every minute over a 24 hour period. The comforting pitter patter will add up to over 9,000 gallons of
water, weighing over 75000 pounds. The adjacent yard will be inundated. Most of the water will be wasted. It will run off and not linger long enough
to help our parched plants and landscape.

I don't know if its worth our while to try and save the small amount of water that normally rains in San Diego, but all it takes is a rooftop, a tank, and a pump. In some parts of the world it is not only necessary, but it's mandatory.

Mort's figures refer to 1 sq foot of
area. Please add the info about the rain barrels. It just what is needed to
make it current and useful. Its something everyone can do .... if only for one barrel.



"Mort Brigadier"
Habitat Steward