More than 461 billion—and counting. This striking figure, prominently displayed on the Orange County Water District’s (OCWD) website, represents the gallons of potable water produced by the Groundwater Replenishment System (GWRS) since it became operational in 2008. As the world’s largest advanced water purification system for indirect potable reuse, the GWRS stands out as a visionary project that takes a once-wasted resource, wastewater, and purifies it into high-quality drinking water—a remarkable feat that reflects innovation, leadership and sustainability.
OCWD’s visionary leadership in water recycling dates back to the 1970s, when it built and operated one of the region’s first advanced wastewater reclamation facilities, Water Factory 21. Building on this legacy, OCWD expanded upon the partnership with its neighbours at the Orange County Sanitation District (OC San) to develop a solution that would prioritise water reuse and redefine regional water reliability.
A joint initiative of the two agencies, GWRS began producing purified wastewater at an initial capacity of 70 million gallons of water per day (MGD). A 2015 expansion increased that figure to 100 MGD. With its final phase completed in 2023, the system now recycles 100 per cent of OC San’s reclaimable wastewater flows, producing up to 130 MGD—enough to serve one million people. It's an impressive milestone that sets a new standard in the industry for large-scale potable reuse.
The system now recycles 100% of OC San’s reclaimable wastewater flows, setting a new standard in the industry for large-scale potable reuse
The purified water is then injected into wells located near the Pacific Ocean coastline to protect seawater intrusion into the Orange County Groundwater Basin, directly injected into the basin, and sent to recharge basins to allow for percolation into the basin. Managed by OCWD, the groundwater basin is the primary drinking source for 2.5 million people in north and central Orange County.
Getting to this final phase didn’t happen overnight. It took strategic planning, technical expertise and community outreach – all necessary ingredients to a successful project. For the final expansion, innovation and new technologies also played a crucial role, whether it was testing and developing new membranes to optimize performance, reducing energy usage and maximizing water output, building new pipelines and infrastructure to get more wastewater to the facility or evaluating the quality of the new source water that was coming into the plant.
When OCWD and OC San launched the GWRS, it marked a bold step toward investing in and securing a resilient water supply. Today, that vision has paid off many times over. Not only is GWRS less expensive and less energy-intensive than importing water from northern California or the Colorado River, but it also offers local reliability and reduced dependency on increasingly strained external sources. It’s a solution that continues to benefit both partners and the communities they serve.
The final completion of GWRS comes at a critical time. As many parts of the world face the impacts of extreme weather cycles, the need for sustainable water solutions is more urgent than ever. Recently finalised regulations in California supporting direct potable reuse provide an opportune time for other water agencies to explore advanced water recycling strategies, and, for those agencies pursuing indirect potable reuse or direct potable reuse projects, they can look to the GWRS as a model.
Water reuse has proven to be a successful investment for OCWD and its communities and reflects our commitment to explore all possible water supply solutions. Even with the success of GWRS, OCWD continues to innovate and test new technologies to identify more opportunities to enhance operations and support our diversified water supply portfolio. We are always looking ahead as we remain committed to our mission to bring reliable, high-quality water to our communities.