Sites Reservoir, California’s largest proposed new water storage project, moved closer to construction after the Sites Project Authority said a revised state water right permit can support a viable project. The authority has entered its investment period, and the final permit goes before the State Water Resources Control Board on November 4, 2026.
Key Takeaways
- The Sites Project Authority board voted to advance its “benefits and obligations period,” the step where participating water agencies sign commitment contracts.
- Sites Reservoir is designed to store up to 1.5 million acre-feet, enough to supply more than 4.5 million homes for a year.
- Up to 200,000 acre-feet of stored water would be set aside as a new supply for emergency-declared droughts.
- The project is eligible for $1.363 billion in state Water Storage Investment Program funding from Propositions 1 and 4, including nearly $269 million added in June 2026.
- The revised permit keeps two local creeks, Funks and Stone Corral, under consideration as water sources, which the authority calls key to affordability for the Sacramento Valley.
- The reservoir is projected to draw about 187,000 recreation visitors a year once complete.
Revised Permit Opens a Path Forward for Sites Reservoir
The latest step for Sites Reservoir came from a revised water right decision issued by the State Water Board’s Administrative Hearings Office. It followed a March 2026 draft that the Sites Project Authority had pushed to change. In its response, the authority said the revised terms “can potentially support a viable Project” and that without the revisions, the project would not have been able to advance.
The authority identified three changes that made the difference. First, the permit now treats Sites Reservoir like every other new water right under the anticipated Bay-Delta Plan updates, rather than singling it out for additional requirements. Second, adjusted diversion rules allow the reservoir to draw water from the Sacramento River during high-flow conditions while keeping protections for fish, wildlife and the Delta. Third, Funks and Stone Corral Creeks remain in play as local water sources through a separate hearing process.
The authority urged state regulators to keep those improvements in the final permit, calling them essential to the project delivering its intended public benefits. That makes the November 4 hearing the next critical test.
How Sites Reservoir Would Work
Sites Reservoir differs from California’s traditional dams. It is an off-stream reservoir planned for the Sites Valley west of Maxwell in the Sacramento Valley. Rather than blocking a river, it would divert and store a portion of Sacramento River flows during wet periods, after other water rights and regulatory requirements are met, then release that water in drier years.
Beyond supplying cities and farms, the reservoir is designed to capture flood flows to reduce potential flood damage and to deliver water to wildlife refuges, including the Sacramento National Wildlife Refuge Complex, the Upper Butte Basin Wildlife Area and San Luis National Wildlife Refuge. Its dedicated drought reserve of up to 200,000 acre-feet would create a new emergency supply for years when the state declares a drought.
Sites Project Authority executive director Jerry Brown said in 2024 that nothing like it had been built in California in more than 30 years. That gap reflects how rare major new surface storage has become in the state.
Rising Costs Raise the Stakes for Sites Reservoir
Sites Reservoir’s price tag has climbed as the project moved through permitting. Original estimates put the reservoir at $4.5 billion, but by 2025 the estimate had risen to as much as $6.8 billion, driven by inflation, supply chain pressures and tariffs.
State support has grown alongside those costs. In June 2026, the state added nearly $269 million, bringing Sites Reservoir’s eligibility to $1.363 billion in voter-approved bond funding from Propositions 1 and 4. The project has also secured federal commitments.
Because Sites is a “beneficiary pays” project, the participating water agencies that sign on during the benefits and obligations period will fund their shares and receive a proportional portion of the stored water. The contracts those agencies sign in the coming months will show how much of the project’s capacity is spoken for, and at what cost to their ratepayers.
El Niño Season Adds Urgency to California Water Storage
The Sites Reservoir milestone arrived days after California proclaimed a state of emergency on September 21 to prepare for a potentially historic El Niño season. The proclamation mobilizes state resources to reduce flood risks, stage emergency equipment and protect vulnerable communities and infrastructure ahead of winter storms.
That timing shows the problem Sites Reservoir is meant to address. California increasingly swings between drought and flood, and state water officials project a 10% loss of water supply by 2040 due to hotter, drier conditions, with State Water Project reliability potentially falling by as much as 23%. Heavy storms can deliver large volumes of water that the existing system cannot hold.
Sites Reservoir will not be ready for this winter. But if the final permit is approved on November 4 and the agency contracts come together, the project would move into construction and give California new capacity to capture storm flows in future wet seasons.
FAQs
What Is Sites Reservoir?
Sites Reservoir is a proposed off-stream reservoir in the Sacramento Valley that would store up to 1.5 million acre-feet of water captured from Sacramento River high flows.
When Will the State Water Board Vote on the Sites Reservoir Permit?
The final water right permit for Sites Reservoir is scheduled to go before the State Water Resources Control Board on November 4, 2026.
How Much Will Sites Reservoir Cost?
Cost estimates have risen from an original $4.5 billion to as much as $6.8 billion as of 2025, driven by inflation, supply chain pressures and tariffs.
How Much Water Can Sites Reservoir Hold?
Sites Reservoir can hold up to 1.5 million acre-feet, enough to supply more than 4.5 million homes for a year, with up to 200,000 acre-feet reserved for emergency droughts.
