Do two households actually consume an acre foot of water a year?

by Robert Marcos

An oft-cited metric that claims that an acre foot of water is enough to supply two average households for a year, is wrong. Yet innumerable government agencies, academics, and news agencies continue to reference this obsolete metric, even though plenty of recent studies show that modern households use far less water than they did a generation ago.¹

It’s bad enough that “40 million people” are reported to depend upon the Colorado River, while agriculture – which uses 80% of that water isn’t mentioned, another frequently used anecdote claims that households are using more water than they are. The fact is that while the populations of cities have increased, per capita water use has fallen dramatically.

Here are current metrics showing actual residential water use in six western cities –

DENVER, Colorado Average annual residential water use is between 0.25 – 0.28 AF per year. Residents of Denver practice moderate outdoor summer watering balanced by high indoor winter efficiency. Single-family residential customers average about 50 gallons per person per day for indoor use, with overall annual use split roughly 50/50 between indoor and outdoor needs. ²

LAS VEGAS, Nevada Average annual residential water use is between 0.28 – 0.35 AF. Las Vegas’ single-family homes approach 0.40 AF, but extensive multi-family recycling drops the citywide household average. averages about 0.106 AF per person per year, placing its per-capita consumptive water footprint efficiently among major desert metros due to strict turf restrictions and comprehensive indoor water recycling. Under regional water management rules, the vast majority of Las Vegas single-family homes consume under 0.50 AF total per household annually.³

TUCSON, Arizona Average annual residential water use is between 0.20 – 0.22 AF per year. The city of Tucson has dramatically reduced residential water usage during the past two decades. Tucson residential customers average about 74 to 76 gallons per person per day, ranking among the lowest per-capita residential consumers in the desert Southwest. The city of Tucson has been proactive in encouraging water conservation by offering a wide range of rebates and incentive programs to residential and commercial customers. ⁴

SALT LAKE CITY, Utah Average annual residential water use is between 0.75 – 0.80 AF per year. Driven by larger average household sizes and substantial summer landscape irrigation needsState and regional municipal data indicate residential and indoor/outdoor mixes run considerably higher than the national average, though overall municipal and industrial per capita targets across Utah hover around 223–242 gallons per day (which includes commercial and institutional sectors alongside residential footprints). ⁵

SAN DIEGO, California Average annual residential water use is between 0.22 – 0.24 AF per year. Multi-family housing density and strong baseline state efficiency standards. County-wide residential water use averages approximately 76 gallons per person per day, down from historical averages due to ongoing state and local efficiency standards. ⁶

PHOENIX, Arizona Average annual residential water use is between 0.29 – 0.45 AF per year. Large variations between newer low-water developments and older properties with pools and grass lawns. City residents average between 100 and 155 gallons per person per day total residential use, with the majority consumed outdoors via landscaping and pools. ⁷