Groundwater Replenishment System Completion Increases Water Supply Reliability for Orange County

Officials gathered to toast and dedicate the completion of the Groundwater Replenishment System (GWRS). A joint project and a decades-long effort of the Orange County Water District (OCWD; the District) and the Orange County Sanitation District (OC San), the GWRS is the world’s largest indirect potable reuse facility.

This marks an incredible milestone in recycling 100 percent of OC San’s reclaimable wastewater flows and providing up to 130 million gallons of water a day (MGD), enough to serve one million people daily. Operational since January 2008, the GWRS began producing 70 MGD and increased production to 100 MGD after an initial expansion was completed in May 2015. To date, it has produced more than 400 billion gallons of water and counting.

The GWRS takes highly treated wastewater that would otherwise be discharged to the ocean and purifies it using a three-step advanced treatment process consisting of microfiltration, reverse osmosis, and ultraviolet light with hydrogen peroxide. The result is high-quality water that is pumped to recharge basins in Anaheim, where it naturally percolates into the Orange County Groundwater Basin (Basin) and becomes part of the drinking water supply for 2.5 million people in the north and central Orange County.

GWRS water is also sent to injection wells located along Orange County’s coast to create a seawater intrusion barrier that protects groundwater supplies. In addition to reducing the volume of treated wastewater discharged into the ocean, GWRS water improves water quality in the Basin and offers a more cost-effective and energy-efficient alternative than importing water from northern California or the Colorado River.

Over the years, GWRS water has become a primary source used to refill the groundwater basin and has enabled OCWD’s 19 cities and local water retailers to pump more water from the Basin and become more locally sustainable. The GWRS has garnered global attention for its innovative approach and use of technology and continues to serve as a blueprint for other agencies around the world. For more information, visit