Water Factoids

Units of measuring water

One gallon of water weighs approximately 8.34 pounds.

Acre-inch (ac-in)
One acre-inch is the volume of water necessary to cover an acre 1 inch deep or the amount of water falling on an acre in a 1-inch rain. One acre-inch equals 3,630 cubic feet or 27,154 gallons.

Acre-foot (ac-ft)
One acre-foot is the volume of water necessary to cover an acre 1 foot deep. One acre-foot equals 43,560 cubic feet, 325,851 gallons or 12 acre-inches.

Gallons per minute (gpm)
One gallon is exactly 231 cubic inches. The gallons per minute measurement is the amount produced by a pump, stream, or pipeline in one minute.

Cubic feet per second (cfs)
One cubic foot per second is a flow of water equivalent to a stream 1 foot wide and 1 foot deep flowing at a velocity of 1 foot per second.

1 cfs = 450 gpm = 1 ac-in/hour = 2 ac-ft/day

Head (H)
Head is a depth of water, usually in feet. It can also mean pressure; a volume of water exerts a pressure on the bottom of a container, lake or stream that is proportional to the depth of water above the bottom. One foot of water (head) exerts a pressure of 0.43 pounds per square inch on the bottom surface. Or, 1 pound per square inch is equivalent to 2.31 feet of head.