GWRS: new water you can count on

The Groundwater Replenishment System (GWRS) is the world’s largest water purification system for indirect potable reuse. The system, which is a joint partnership between the Orange County Water District (OCWD) and the Orange County Sanitation District (OC San), takes highly treated wastewater that would have previously been discharged into the Pacific Ocean and purifies it using a three-step advanced treatment process consisting of microfiltration, reverse osmosis and ultraviolet light with hydrogen peroxide. The process produces high-quality water that meets all state and federal drinking water standards.

130 million

gallons of water a day

1 million

people served

100%

local reclaimable wastewater flows recycled

35%

of total water
demands met

$900 million

investment to
expand water reuse

Since January 2008, the GWRS has created a locally controlled, reliable supply of high-quality water that is drought-resilient. Additional benefits include:

Decreases Southern California’s dependency on costly imported water from the Sacramento-San Joaquin River Delta and the Colorado River
Uses less than half the energy required to transport water from northern to southern California
Uses one-third the energy required to desalinate seawater
Improves groundwater quality by reducing the amount of dissolved solids (salt) in the groundwater basin
Protects Orange County’s groundwater basin from seawater intrusion
Reduces the amount of wastewater discharged to the Pacific Ocean
Protects the environment by reusing a precious resource
Demonstrates a successful partnership between public agencies
Serves as a blueprint for water agencies throughout the world to help solve their local water supply issues

The process

Frequently asked questions

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