California, Arizona water agencies partner on drought-proof alternative to Colorado River
As drought and population growth continue to put ever greater pressure on water supplies from the Colorado River, some of the key agencies that rely the most on the critical waterway are partnering in the hopes of developing a large-scale water recycling program in southern California. The goal of the ambitious plan is to develop an alternative water source that will relieve some of the burden on the over-allocated Colorado River.
On October 12, the Board of Directors of the Metropolitan Water District (MWD) approved an agreement with the Central Arizona Project (CAP) and the Arizona Department of Water Resources under which the two agencies will contribute up to $6 million for environmental planning efforts pertaining to the Regional Recycled Water Program.
A partnership of the MWD and the Sanitation Districts of Los Angeles County, the planned $3.4 billion Regional Recycled Water Program would entail the design and construction of a 150 mgd facility for recycling wastewater that currently is discharged from the Los Angeles area to the Pacific Ocean. Begun in 2020, environmental planning for the project will cost approximately $30 million and last three years, according to the MWD’s October 13 news release.
Approximately 25 percent of the water for southern California comes from the MWD’s Colorado River Aqueduct. Although CAP receives its water from the Colorado River, the agency holds a junior priority entitlement to the water and thus is more vulnerable to reductions in the face of shortages. In August, the U.S. Bureau of Reclamation pronounced the first-ever shortage for Lake Mead, the lower reservoir on the Colorado River. The pronouncement triggered an 18 percent reduction of Colorado River water to Arizona in 2022.
Against this backdrop, the MWD views the Regional Recycled Water Program as a collaborative way to alleviate additional shortages in the future. “This project could help the entire Southwest,” said Adel Hagekhalil, the general manager of the MWD, in an October 13 release. “We know that eliminating the supply-demand imbalance that threatens the Colorado River will take both reducing demand, through conservation, and adding new supplies, like recycled water,” Hagekhalil said. “That’s why our partners in the Lower Basin are interested in helping us develop the project.”
The MWD’s agreement with the Arizona entities follows a similar agreement that the department entered into last December with the Southern Nevada Water Authority (SNWA), the wholesale water provider for 2.2 million residents of southern Nevada. The SNWA also agreed to provide up to $6 million for environmental planning associated with the Regional Recycled Water Program. Because of the shortage pronouncement for Lake Mead, Nevada faces a 7 percent reduction in its annual Colorado River apportionment in 2022.
As currently envisioned, the Regional Recycled Water Program would purify treated wastewater discharged from facilities operated by the Sanitation Districts of Los Angeles County. The finished water, ultimately totaling as much as 168,000 acre-ft/yr, could be used to recharge groundwater basins, used for industrial purposes, or potentially even sent to two of the MWD’s drinking water treatment plants.
To test the concept of the Regional Recycled Water Program, the MWD and the Sanitation Districts began operating a 500,000 gal/d demonstration facility in fall 2019. Known as the Advanced Purification Center, the facility accepts treated effluent from the Sanitation Districts’ Joint Water Pollution Control Plant in Carson, California. The Advanced Purification Center employs a three-step treatment process comprising membrane bioreactors, reverse-osmosis membranes, and disinfection by means of ultraviolet light and oxidation.