People in California and the Southwest are getting stingier with water, a story that’s told by the acre-foot.

For years, water use has generally been described in terms of acre-foot per a certain number of households, keying off the image of an acre-foot as a football field a foot deep in water. The long-time rule of thumb: One acre-foot of water would supply the indoor and outdoor needs of two typical urban households for a year.

The acre-foot yardstick has been a reliable standby for water agency officials to explain water use to the public, said Bill McDonnell, water efficiency manager with the Metropolitan Water District of Southern California, but “it was not super science.” 

Science or not, it’s a description that’s stuck. But that acre-foot, equal to about 325,000 gallons, is being stretched amid increased water conservation in an urban landscape that has been buffeted by drought and squeezed for mandatory reductions.

Tim Quinn, executive director of the Association of California Water Agencies and a former deputy general manager with MWD, said it may be time to recalibrate the thinking on how much water is delivered to homes and businesses.

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