Sharing Is Caring, and Profitable, in Southern California Water

Three Southern California water agencies signed a first-of-its-kind inter-agency water transfer deal using existing infrastructure

7 Apr 2026

Southern California just rewrote the rulebook on regional water sharing, and it didn't need a single new pipeline to do it.

On March 19, 2026, the San Diego County Water Authority and the Western Municipal Water District signed a landmark long-term transfer agreement, facilitated by the Metropolitan Water District of Southern California. Western committed to purchasing at least 10,000 acre-feet per year from the Water Authority over 21 years, delivered entirely through existing Metropolitan infrastructure. No new construction required.

At $1,350 per acre-foot, the deal is structured to generate roughly $13.5 million annually for the Water Authority, with an estimated $100 million flowing back to San Diego County ratepayers over the first five years. Western also secured about 30,000 acre-feet of pre-purchased future supply, locking in long-term certainty for its service area across western Riverside County.

What makes the agreement genuinely historic is its mechanism. Both agencies are Metropolitan members, but water has never before moved directly from one to another through MWD's aqueduct system. MWD board president Adan Ortega called it a first of its kind. Water Authority general manager Dan Denham was blunter: it had simply never been done before.

The deal converts San Diego's carefully built water surplus into a revenue-generating regional asset. Years of supply diversification, anchored by the Carlsbad Desalination Plant, gave the Water Authority more capacity than it currently needs. Rather than letting that resource sit idle, the agreement channels it toward a neighboring utility facing real supply pressure in Riverside County.

For the broader US water sector, the model matters. As climate stress tightens supply across the Colorado River Basin and infrastructure costs keep climbing, inter-agency transfers built on existing networks could become a powerful template for low-cost regional resilience. Smart water management, it turns out, increasingly means rethinking how water is allocated and shared, not just how it is monitored.