Building Local Supplies

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Think Regional, Act Local

Metropolitan’s role in the region has evolved over time. We are builders and planners. We brought water to Southern California, and we look today at the possibilities of local supply development to complement our imported supply investments. Our support of conservation and diverse local resource programs like water recycling, desalination, groundwater recovery and storage have provided over 7 million acre-feet to the region’s resource mix and increased our resiliency and reliability. Local resources are regional resources because they offset regional imported water demands.

It’s not an either-or situation: we’re developing local resources while shoring up our imported supplies. Each piece of our supply portfolio depends on the other. One is insurance against the other’s vulnerabilities. When imports are challenged by drought cycles or natural disasters, local resources and conservation programs can ease the burdens of import demands. In turn, high quality imported supplies are necessary for recycling and groundwater replenishment programs. Working together, these sources provide Southern California with reliable water. Having a mix of water resources to draw from has protected the region from the impact of drought cycles and climate change.


Local Supplies for Regional Reliability

When a local supply is developed, whether it is in Ventura, San Diego, or any community in between, all Southern California benefits. Our regional cooperation and interdependence mean one community’s recycling or groundwater cleanup project decreases the burden on Metropolitan’s system as a whole. That reduces operating costs, frees up conveyance capacity to benefit all system users and helps the region adapt to climate change. That is why Metropolitan supports and incentivizes several beneficial programs and initiatives that help the region act locally. We have invested $1.6 billion in these programs to date. For a rundown of achievements, click here and for the full Achievement Report click here.

The numbers tell a success story. In the 1990s, nearly 60 percent of Metropolitan’s supply portfolio was made up of imported resources from the Colorado River and our contract with the State Water Project. The balance was from local resources. A shift in the supply paradigm shows a 2035 mix of about 36 percent imported supply and 64 percent local resources.

Local Supply Target

Local Resources

Ensuring reliable water for Southern California requires investing in local water supplies from diverse sources and widespread conservation.

Milestones in Recycled Water Use

The past five decades have seen recycled water use in Southern California grow rapidly, for both irrigation and groundwater replenishment.

Here's a look at its history in the region, from the first recycled water plant to the large recycling water projects we see today.



The Sanitation Districts’ Whittier Narrows Water Reclamation Plant becomes the first plant in the U.S. intentionally designed to recycle water, using it to recharge groundwater basins.



As Southern California’s population grows, recycled water lines are constructed alongside new development to irrigate schoolyards, parks and golf courses.



Water Factory 21 begins purifying wastewater in Orange County and using it to replenish and protect groundwater from seawater intrusion. Becomes first plant in the world to use reverse osmosis.



Wastewater treatment plants add processes to produce more recycled water. Purple pipes are adopted as industry standard to distinguish recycled water for irrigation, firefighting and industrial use.


1995 to 2005

Several new water recycling facilities are built that use reverse osmosis. The resulting water is used for groundwater recharge and industrial use.



Orange County embarks on the largest water reuse project of its kind in the world, eventually purifying 130 million gallons of water daily to replenish groundwater supplies used for drinking. Becomes the gold standard for water recycling.



The city of San Diego advances a water recycling program that for the first time in California would use purified recycled water to fill a drinking water reservoir.



Water agencies from Ventura to San Diego continue to take steps toward implementing large recycling projects. The Regional Recycled Water Program will take the rapid growth of recycled water use in Southern California even farther.

Future Supply Actions

Metropolitan is also investing in research to develop future local water supplies through innovative approaches. Through the Future Supply Actions Funding Program, Metropolitan funds member agency pilot projects and technical studies aimed at increasing the potential of recycled water, stormwater, groundwater and seawater desalination. Metropolitan has so far invested $6.5 million in more than two dozen studies.