Skip to content

Clear Waters Ahead: How Riverside's desalters transform local and downstream water quality

"Metropolitan is in the undesirable position of having high fixed costs for maintenance of its extensive water system and construction of needed new facilities but low fixed revenue."

Back in 1989, there was a lot of concern that groundwater in the La Sierra area was becoming increasingly saline and contaminated with nitrates by local agriculture. This water was flowing underground toward Prado Basin and then down the Santa Ana River to Orange County, where it percolated into the ground and was later pumped back out to provide drinking water for much of the northern part of the county.  After years of arguing and finger-pointing, the Santa Ana Watershed Water Authority (SAWPA) built a facility to remove salts and nitrates from the groundwater and return the cleaned water to the Santa Ana River.   SAWPA is a Joint Powers Authority comprised of the San Bernardino Valley Municipal Water District, the Inland Empire Utilities Agency, the Eastern Municipal Water District, the Western Municipal Water District, and the Orange County Water District.  The facility, called the Arlington Desalter, is located near Magnolia and Pierce here in Riverside.

The Arlington Desalter uses reverse osmosis to remove contaminants from the groundwater, which is pumped from several local wells.  The concentrated salts, nitrates, and other contaminants removed in the reverse osmosis process are delivered to the Inland Empire Brine Line and, after treatment at the Orange County Sanitation District facilities, discharged to the ocean.  Originally, the Arlington Desalter produced 3.7 million gallons per day of high-quality water, which improved the quality of Orange County’s water supply.

After a few years, Western Water recognized that this water could be converted directly to drinking water by adding a little more technology and that the water would be less expensive than imported water purchased from the Metropolitan Water District.  Western Water took over the facility and began providing high-quality drinking water to the City of Norco.  In 2017, the Arlington Desalter was expanded to produce drinking water at the rate of 6.4 million gallons per day.  Today, the Arlington Desalter provides almost all the water for Norco, some for Corona, and for Western Water’s retail customers in Riverside.  Recent pipeline additions have made Arlington Desalter water available to other nearby agencies should they need it.

With the success of the Arlington Desalter, it became clear that similar facilities could both improve the quality of the water entering the Santa Ana River from the Chino Basin and provide additional high-quality drinking water in the area.  Once again, SAWPA stepped up and, in 2000, built a desalter in the Chino Basin.  The initial desalter provided 14 million gallons per day, but the goal was set at just short of 36 million gallons per day.  The Chino Desalter Authority was formed in 2001 and took over the initial desalter and responsibility for future expansion and additional desalter facilities.  With plant expansions and the construction of a second desalter facility, that goal has been achieved.  Water from the Chino 1 and 2 Desalters is available to the Cities of Chino, Chino Hills, Norco, Ontario, and the Santa Ana River Water Company, the Jurupa Community Services District, the Inland Empire Utilities Authority and beginning in 2009, Western Water.  

The Chino Desalters provide an added benefit by capturing all of the underground flow of high salt and nitrate water before it enters the Santa Ana River at Prado Basin.  This prevents high salt and nitrate level water from flowing down the river to Orange County and degrading their underground water basins.

Although groundwater desalters are energy intensive because the raw water must be pumped through the reverse osmosis membranes, it is still less expensive than imported water, and the desalting process improves local groundwater quality as well as the quality of the water that flows down the Santa Ana River to Orange County.  As time goes on, additional desalters may be built in the Inland Empire to help keep our water costs as low as possible while continuing to provide high-quality water for home, business, and agricultural uses.