The San Diego County Water Authority has locked in a 21-year deal to sell surplus water to the Western Municipal Water District, a transaction that turns San Diego’s years of investment in supply diversification into a revenue stream worth an estimated $100 million over its first five years.
Under the agreement, SDCWA will deliver a minimum of 10,000 acre-feet of water per year to WMWD, which serves roughly 1 million people across western Riverside County. An acre-foot, about 326,000 gallons, is enough to supply two to three Southern California households for a year. The deal also includes an upfront purchase of approximately 30,000 acre-feet for roughly $40 million, giving SDCWA an immediate cash infusion and giving WMWD guaranteed supply it can plan around before annual deliveries begin.
All water will move through the Metropolitan Water District’s existing conveyance system, which already connects both agencies. No new pipelines, pumps, or treatment plants are needed, a detail that allowed the project to bypass a full environmental impact review under the California Environmental Quality Act.
Why San Diego has water to sell
A decade ago, this deal would have been unthinkable. San Diego County was one of the most import-dependent urban areas in the western United States, buying roughly 90 percent of its water from the Metropolitan Water District. That vulnerability drove a deliberate diversification campaign: the Claude “Bud” Lewis Carlsbad Desalination Plant, the nation’s largest ocean desalination facility, came online in 2015. A long-term transfer agreement with the Imperial Irrigation District, secured through the landmark Quantification Settlement Agreement, delivers Colorado River water directly to San Diego. And the region has expanded recycled water and conservation programs steadily.
The result is a portfolio with surplus capacity, at least under current conditions. That surplus is what SDCWA is now monetizing through the WMWD exchange.
Why Riverside County is buying
Western Riverside County faces the opposite pressure. The region’s population has grown rapidly over the past two decades, and its water agencies are navigating tightening supplies on the Colorado River alongside uncertainty about future State Water Project allocations. For WMWD, a 21-year contract with a defined minimum volume offers planning certainty that spot purchases on the open market cannot match.
No direct statements from WMWD leadership have appeared in the primary records reviewed for this article. The joint announcement framed the agreement as a partnership between Southern California water leaders, but individual comments from WMWD executives are absent from available documentation. How the district plans to integrate this supply into its existing portfolio, and whether it views the deal as a structural shift or a supplement, remains unclear.
Deal terms and what the documents show
Two primary records anchor the reporting. A joint announcement from the agencies confirmed the minimum annual volume, the 21-year duration, the pre-purchase terms, and projected revenue of approximately $13.5 million per year. A Notice of Exemption filed with the California Governor’s Office of Land Use and Climate Innovation, carrying state clearinghouse number 2026030889, identifies SDCWA as the lead public agency and describes the action as an agreement authorizing long-term exchange and delivery of surplus water using existing facilities and current operational protocols.
The CEQA exemption is significant because it defines the project’s legal boundaries. If the agencies later sought to build new infrastructure for this exchange, they would need a separate environmental review. The exemption effectively locks the deal into the existing system.
Several important details remain undisclosed. The per-acre-foot price is not published in either record. The $40 million pre-purchase and $13.5 million annual revenue figures allow rough estimates, but the actual pricing structure, including whether rates escalate over time or include drought-year adjustments, has not been made public. Revenue allocation within SDCWA is also unspecified: whether the projected income will go toward debt service, capital reserves, or rate relief for San Diego County customers is not addressed in available filings.
What could change the math
The revenue projections are forward-looking estimates, not guaranteed outcomes. Actual returns will depend on how much water SDCWA delivers above the 10,000 acre-foot annual minimum, whether drought conditions reduce surplus availability, and how pricing terms perform across a 21-year horizon. Southern California’s water landscape is shifting rapidly: the Colorado River basin remains under stress, state and federal negotiations over post-2026 river operating guidelines are ongoing as of spring 2026, and climate variability adds uncertainty to every long-range supply forecast.
The CEQA exemption also raises a monitoring question. No post-agreement environmental oversight plan or impact assessment schedule appears in the state’s public records for this filing. Whether ongoing environmental review is built into the contract or handled through other regulatory channels is not addressed in the documents currently accessible.
What ratepayers in both districts should watch next
For residents of San Diego County or western Riverside County, the most direct way to track how this agreement affects water rates or supply reliability is through board meeting agendas and financial disclosures from both SDCWA and WMWD. Rate changes tied to this deal, if any, would typically surface in each agency’s annual budget process, which for most California water districts runs through spring and early summer.
The CEQA filing number, 2026030889, provides a searchable reference for any future amendments or environmental actions tied to the exchange. And the deal’s real test will play out over years, not months: whether San Diego’s surplus holds up under changing climate conditions, whether Riverside County’s growth demands outpace the contracted volume, and whether the financial terms prove durable across two decades of Southern California water politics.
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*This article was researched with the help of AI, with human editors creating the final content.
