Urban consumers have already cut water use over the past decade, but more can be done.
With drought getting worse, California needs to increase water use efficiency.F. Armstrong Photography / Shutterstock Shutterstock License
California can cut the amount of water used in urban and suburban areas by nearly one-third—or with some extra measures by nearly half—simply by using technology that already exists, according to a new report by the Pacific Institute, an Oakland-based think tank that studies water issues. Residential Californiana have made significant strides toward cutting their water use over the past couple of decades.
Thanks largely to increased efficiency measures, such as mandatory use of low-flow toilets and shower heads, California's urban water consumption dropped from about 9.3 million acre-feet in 2007. Total consumption is now around 7 million per year, even as population numbers have increased.
Even that noteworthy drop is not enough.
Drought conditions from 2000 to 2021 were the worst in the southwestern United States in at least 12 centuries, and California’s ongoing drought is getting worse. As of April 2022, according to the U.S. Drought Monitor, 100 percent of California was under at least “moderate” drought conditions, with 95.75 percent reaching “severe” drought levels and 46.87 percent—almost half of all the territory in California—afflicted by “extreme” drought.
Compare that to one year earlier, when 94.14 percent of the state was under “moderate drought,” and 38.68 percent was listed as “extreme.”
The Sierra snowpack, which supplies roughly 30 percent of all water used in the state, contained just 39 percent of the annual average snow volume as of mid-April 2022, according to Andrew Schwartz, lead scientist and station manager at UC Berkeley’s Central Sierra Snow Lab. That’s a 23 percent drop from the previous year.
Despite Californians’ relieved sighs of “We need the rain!” at any sign of precipitation, increased rain and snow—though obviously essential—won’t help as much as one might expect. Prolonged droughts are self-perpetuating. When the ground becomes excessively dry, it soaks up more water, leaving less to run off into streams and reservoirs. Alternatively, dried-out soil can get so hard that it won’t absorb nearly enough water, causing floods.
That means relatively short bursts of rain or snow can no longer be relied upon to ease the drought. Water conservation efforts, as a result, are more important than ever.
City-dwellers use about 10 percent of all the water consumed in California (“urban” use includes both cities and suburbs). That may not seem like much, but even in a dry year such as 2014, the urban sector used 6.7 million acre-feet of water. A single acre-foot contains about 326,000 gallons, or the amount it would take to cover one acre (that is, roughly the size of a football field) with water one-foot deep. One acre-foot of water has historically been considered the amount required to serve the needs of two average households for one year, according to the Water Education Foundation.
The good news is, urban California water consumers have made significant progress in cutting down their water over the past 50 years or so. According to the Pacific Institute report, the city of Los Angeles consumes 15 percent less water today on an annual basis than in 1970, even though the city had added 1.2 million water users in the interim. The report also cites declines in San Francisco water use since 1965, and a drop in Fresno as well, since 1990, despite a 32 percent population rise.
As a result, the Water Foundation says that an average acre-foot now serves 3.4 households, and in San Francisco, six households can function for a year off a single acre-foot. (The Water Foundation defines an average “household” as containing 3.02 people.)
But as well as urban dwellers have done with water efficiency measures, the new Pacific Institute report identifies even more measures that can be taken to save even more California water.
“California has made real progress in recent years to reduce water use and augment local water supplies,” Heather Cooley, lead researcher on the report, told the Los Angeles Times. “Without those past efforts, our water challenges would be even more severe. But more is needed in the face of climate change and drought.”
The increased efficiency measures cited in the report rely on existing technology—but avoid modifications to personal habits and behavior, such as taking fewer showers, or refraining from watering lawns. On the other hand, the report does note that replacing showerheads and other water-consuming appliances with more efficient, up-to-date models—and replacing lawns altogether with “climate-appropriate plants”—would aid efforts to use water more efficiently in residential settings.
“There’s that kind of sort of turnover of appliances, turnover of fixtures, turnover of housing stock, that is part of this untapped potential,” Pacific Institute co-founder Peter Gleick told the Times.
About 44 percent of urban water is used outdoors, the Pacific Institute estimates, which offers another significant opportunity to increase efficiency. The elimination of lawns could save a cool million acre-feet per year. More “extensive landscape conversion” could push that savings to 1.5 million.
The report also highlights two other areas in which the state can make more water available for use, which in turn increases efficiency. Water reuse could be at least tripled, the report states, “significantly adding to local water supplies.” According to the report, 728,000 acre-feet of municipal wastewater was reused in 2020 throughout California for irrigation, replenishing groundwater and other uses.
That total was up considerably from 50 years earlier, when just 175,000 acre-feet were reused. But the 728,000 acre-feet figure represents only 23 percent of all wastewater generated by the state’s water consumers, according to the report, which estimates that between 1.8 million and 2.1 million acre-feet remain available to be reused. (The difference in estimates is due to legal, water-rights issues that could affect discharged water.)
The third way that California can improve water use, the Pacific Institute says, is through stormwater “capture.” The state does not keep statistics on the volume of stormwater retained by local water suppliers and pumped back into the water supply, so it is impossible to say how far California is falling short.
The Pacific Institute, however, estimates that in a “dry” year there are still 580,000 acre-feet of stormwater—enough to serve the water needs of 192,000 households for a year—that simply go unused. In a year of high precipitation, 3 million acre-feet of stormwater could be captured. That’s enough water, using the Water Education Foundation’s figures, to serve seven of every 10 households in Los Angeles for the full year.
Reusing wastewater and capturing stormwater, as well as converting household appliances and lawns to be more water-efficient, will cost money, but can be done relatively cheaply, according to what Gleick told the Times.
“Investing in these options is going to be cheaper and more effective and quicker than investing in the traditional things that we’ve done statewide in the past,” he told the paper.
Gleick added that the report did not consider the option of adding to the water supply by converting ocean water to fresh water because the process of desalination is “incredibly expensive, it’s energy intensive, [and] it has environmental liabilities.”