San Diego, Long Most Dependent on Colorado River, Now Has Surplus Water for Sale Thanks to Recycling and Desalination

San Diego, a coastal city that receives barely eight inches of rain in a good year, has historically been at the end of the line for Colorado River water—a three-hour drive from the shrinking river. Now, due to aggressive water recycling, urban and agricultural conservation programs, and a major investment in seawater desalination, the city holds a surplus that neighboring cities and states are eager to tap. Even as California offers to take less water from the drought-shrunken Colorado River, San Diego, long the most dependent on that supply, curiously now has excess water to sell.

Desalination Plant Output and Local Demand

At Carlsbad State Beach north of San Diego, the Claude "Bud" Lewis Carlsbad Desalination Plant pumps roughly 100 million gallons of seawater daily through gravel and sand, treating it via reverse osmosis. About fifty million gallons a day turns into potable water. Since coming online in late 2015 at the site of a former coal-fired power plant, the facility has produced approximately 7-10% of the region's water. Despite the ongoing western megadrought, local demand currently does not require that supply. "We're the only agency that is bringing new water into the system. This is not horse trading Colorado River water. This is really introducing and augmenting the system with new water," said Meena Westford, director of imported water at the San Diego County Water Authority.

Water Exchange Mechanism and Regulatory Approval

No plans exist to build a pipeline to Arizona or truck desalinated water to Las Vegas. Westford described the arrangement as a transfer on paper. If approved by the Department of the Interior, the authority would exchange its existing Colorado River supplies stored in Lake Mead for desalinated water. "So we'd be drinking more desal water here in San Diego and leaving our Colorado River supplies for other folks to use," Westford said. The approach aims to demonstrate a new way to manage the system, even if it cannot save the Colorado River entirely. "I don't think we can save the Colorado River, but what we're looking to do is show that there is an opportunity to manage the system in a new way," Westford added.

Cost, Energy, and Environmental Concerns

Desalinated water is energy intensive and extremely expensive to produce. Water from the San Diego plant costs an estimated five to ten times more than river water. Environmentalists argue that building more desalination plants along the California coast is not a solution to the Colorado River crisis. "The water produced by this massive, biggest in the western hemisphere desalination plant is a drop in the swimming pool compared to the entire Colorado River basin supplies issue," said Patrick McDonough, a senior attorney with San Diego Coastkeeper. Standing by a jetty where undrinkable water gets discharged back into the Pacific from the Carlsbad plant, McDonough noted that aggressive conservation by farms and urban water recycling would go much further toward preventing taps from running dry. He also said the plant has driven up local water bills, even as the city has made dramatic conservation strides since the 1990s, cutting water use while the region's population grew.

Context

In 2023, Arizona, California, and Nevada agreed on a new plan to share Colorado River water amid prolonged drought. Similar debates over desalination costs and environmental impacts have occurred in Texas and Australia, where seawater conversion projects faced scrutiny over energy consumption and marine ecosystem effects.