California is one step closer to its largest new reservoir in decades

The U.S. Department of the Interior approved a major California water project on Friday, clearing a key obstacle for a massive new reservoir. 

The proposed 1.5 million acre-foot Sites Reservoir would store water from the Sacramento River and distribute it during droughts to several parts of California, including the Sacramento and San Joaquin valleys, Southern California and the Bay Area. Stretching about 4 miles across and 13 miles north to south, it’s meant to provide water to approximately 24 million people, and it would mark California’s first major reservoir project since 1979, when New Melones Lake was completed.

Jerry Brown, the executive director of the Sites Project Authority, told SFGATE that the new reservoir would capture water that’s mostly “rain-fed” as part of an effort to adapt to a changing climate. 

“So much of our future precipitation is anticipated to come as rain instead of snow, which means it’s going to come fast and it’s going to come flashy, and we have to be prepared with a tool that will allow us to rein in some of that water to the greatest extent,” he said. 

According to a 2022 report from the California Natural Resources Agency, the state could lose 10% of its water supply in the next 20 years. “We will see on average less snowfall, more evaporation, and greater consumption of water by vegetation, soil, and the atmosphere itself,” the report said. 

Sites is part of President Donald Trump’s executive order 14181, which is intended to provide more water resources to the state and help with natural disasters. The federal approval allows the Bureau of Reclamation, which oversees the reservoirs, to fund up to a quarter of the total cost for the project. 

Around $1 billion worth of funding is also set to come from Proposition 1 funding, a water bond in California that was approved in 2014 for water storage projects. Other sources of funding are “project partners,” which are local, public agencies that will benefit from the reservoir, such as county and city water districts. 

The reservoir’s construction was initially set to cost $4.5 billion, but planners increased the cost to up to $6.8 billion to account for inflation. Brown called the project a “generational investment.” 

“This is something that will be here for 100 plus years,” he said. “… We haven’t really made an investment like this in California for decades.”

Jay Lund, a professor at UC Davis and the vice director of the Center for Watershed Sciences, told SFGATE that the reservoir will be “expensive water.” The economics are complicated because it’s mostly going to be used as drought storage rather than regular water supply.

“In this case, the large parts of this reservoir that you get to use only in drought. That means you might only get use out of it any one in five years, maybe 10 years,” Lund said. “But you still have to pay for that capital, that bond, every year. The water is more valuable during a drought.”

Smaller Bay Area water storage projects have faced similar challenges, such as Los Vaqueros Reservoir in Contra Costa County, which was terminated in 2024 because of rising costs. Still, Lund said he believes the Sites Reservoir would be beneficial for the environment. 

“You can move water from the wetter part of the year to the spring, so that might have some environmental use,” he said. 

The next steps in the project are securing water rights from the state and getting local agencies to officially sign off on funding, according to Brown. Construction is expected to start in late 2026, and the reservoir will be fully operational by the end of 2032, the project website shows.

Brown said that as the project moves forward, members of the public should pay attention to where their water comes from. 

“Pay attention to how much it costs, pay attention to the fact that the weather’s changing and our availability of water is precious. We have to do everything we can to save what we got, but what we got is not going to be enough to get us through,” he said.