What’s an Acre-foot?
In the water world, water is commonly measured in acre-feet. But what is an acre-foot? One acre-foot equals about 326,000 gallons, or enough water to cover an acre of land, about the size of a football field, one foot deep. An average California household uses between one-half and one acre-foot of water per year for indoor and outdoor use.
California receives about 193 million acre-feet of water each year as precipitation (rain and snow), but there is great variability between regions. Yearly precipitation on the North Coast is about 90 inches but only 2 inches in Death Valley.
Much of this precipitation evaporates, leaving California with 78 million acre-feet in surface water supply (including Colorado River and Klamath River supplies) in an average year. Of that water: 28 million acre-feet to 35 million acre-feet are used by agriculture; 7.9 million acre-feet are used by cities and industries; and 26 million acre-feet are used for the environment.