The San Diego County Water Authority and Western Municipal Water District today announced a historic long-term regional water supply agreement that strengthens water reliability and creates a paradigm shift in how water providers share resources across the region to benefit millions of customers.

Together, the agencies serve communities representing more than 4 million Southern California residents across Riverside and San Diego counties.

“This agreement is a win for San Diego ratepayers, a win for Western, and a win for Southern California,” said Water Authority Board Chair Nick Serrano. “It allows us to maximize the value of the investments San Diego County residents made over decades, strengthen water reliability, and do so in a way that is mindful of affordability and public responsibility. It is exactly the kind of innovative, collaborative approach this moment demands.”

Under the agreement, Western Water will receive a minimum of 10,000 acre-feet of water annually over the next 21 years, enough to supply approximately 30,000 Southern California households each year and strengthen long-term water reliability for the communities it serves. Western Water is also pre-purchasing approximately 30,000 acre-feet of water for future delivery, a nearly $40 million investment that provides added flexibility during drought.

The partnership will generate approximately $13.5 million annually in revenue for the San Diego County Water Authority, with the agreement expected to deliver roughly $100 million over the first five years after accounting for the upfront payments. Those revenues help offset the cost of long-term water supply investments while making efficient use of existing regional water supplies.

The Water Authority’s current draft Urban Water Management Plan confirms that the agency’s diversified portfolio of water supplies, combined with a sustained commitment to water-use efficiency, will meet the region’s water needs through 2050, even during multiple dry years. That means the Water Authority can continue providing reliable water for San Diego County while making the most of long‑term investments through agreements like the one with Western Water. Revenues generated through those agreements help reduce wholesale water rate pressures for San Diego County customers.

“The county’s ratepayers continue to benefit from investments in water conservation that give us flexibility to balance water affordability and reliability,” said Water Authority General Manager Dan Denham. “This agreement would not have been possible without the incredible team at Western Water that shares our commitment to visionary leadership and collaboration in developing a new way to think about water resources.”

For Western Water, the partnership strengthens long-term water supply planning by securing access to highly reliable supplies at one of the most cost-effective opportunities available today.

Western Water serves nearly one million residents across southwest Riverside County, one of California’s fastest-growing regions, where planning ahead for dependable water supplies is essential for community stability and economic growth. By securing access to these supplies, Western Water strengthens drought protection and long-term supply planning without the cost, risk, or timelines associated with developing major new water supply projects.

“Partnerships like this show what is possible when water agencies work together,” said Laura Roughton, president of Western Water’s Board of Directors. “By sharing secured resources, we can strengthen water reliability for our communities while freeing up supplies that are needed elsewhere across the region. It’s a win for our customers, a win for San Diego, and a win for Southern California’s water system.”

Western Water and the Water Authority worked collaboratively to develop the agreement, reflecting a shared commitment to the health and resilience of Southern California’s water system for generations.

“With California’s water landscape shifting due to climate variability, economic and population growth, now is the time to pursue innovative partnerships that strengthen long-term water planning and affordability,” said Craig Miller, general manager of Western Water. “We appreciate the leadership and professionalism of the San Diego County Water Authority in helping make this partnership possible.”

The agreement builds on a series of innovative efforts by the Water Authority to make the most of its long-term water supply investments. Earlier this year, the Water Authority’s Board approved an agreement with the U.S. Bureau of Reclamation to explore a pilot program that could allow desalinated seawater to be exchanged with Colorado River Basin states – another step aimed at strengthening water security across the Southwest while modernizing how regional water resources are managed.

Water purchased by Western Water will be delivered through existing connections within the Metropolitan Water District of Southern California’s regional pipeline system, meaning no new infrastructure is required. Because the water moves through existing facilities, transfers can be carried out efficiently without building new pipelines or treatment plants.

“Southern California is an economic engine for the nation, and its future depends on a secure and sustainable water supply,” said Metropolitan Board Chair Adán Ortega, Jr. “This agreement was made possible by a legal settlement forged last year between Metropolitan and the Water Authority. That settlement gave birth to a new business model allowing the movement of water between our 26 member agencies. The water that is part of this agreement didn’t just fall from the sky. It was conserved by businesses and residents for the benefit of greater Southern California. Together, we are ensuring our region continues to thrive for generations to come and providing a model that can solve other water challenges in the Southwest.”