Major water agencies in the Southwest along with the U.S. Department of the Interior’s Bureau of Reclamation have launched an effort to explore the feasibility of establishing a framework for interstate desalinated and recycled water exchanges, a move supporters say could spur future investments in new water supply infrastructure and help supplement strained Colorado River supplies.
The memorandum of understanding (MOU) signed June 3 at the Claude “Bud” Lewis Carlsbad desalination plant brings together Reclamation, the San Diego County Water Authority, the Southern California Metropolitan Water District, the Southern Nevada Water Authority, the Arizona Department of Water Resources, the Central Arizona Project and the Salt River Project.
The parties will evaluate how desalinated seawater and recycled wastewater supplies could be integrated into operations in the Colorado River Basin through interchanges of existing infrastructure rather than building new pipelines or other structures.
If implemented, the framework would allow agencies investing in advanced water desalination or recycling to exchange supplies across state lines, potentially improving the economics of the project and avoiding costly new conveyance construction.
According to materials released by the San Diego County Water Authority, the type of interstate transfer pilot envisioned in the agreement has never been implemented in the Lower Colorado River Basin.
Independent policy analyst Sarah Porter, director of Arizona State University’s Kyl Center for Water Policy, said the concept could help address two challenges at once: improving the economics of costly drought-proof supplies while providing additional flexibility in water management to Colorado River users facing future shortages.
In March, Porter told Phoenix public radio station KJZZ that the proposal was “a very neat solution to a very big problem” because San Diego has already invested heavily in desalination infrastructure, while Arizona and Nevada are looking for additional long-term water supplies.
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how it works
Under the concept, San Diego could use desalinated water to reduce reliance on Colorado River supplies and leave some of its river share in the system. Other watershed agencies could pay to access that water through existing Colorado River delivery systems, avoiding the construction of interstate pipelines.
The MOU envisions these agreements as voluntary exchanges that could help fund new water supply projects and allow participating agencies to make better use of available supplies. The agreement is non-binding and does not commit any party to a specific project.
According to Reclamation, storage in the Colorado River system has dropped to about 36 percent of capacity after more than two decades of drought.
“This agreement brings together partners across state lines to explore desalination, water recycling and new ways to move water to where it’s needed most,” Assistant Secretary of Water and Science Andrea Travnicek said in a statement.
The framework could create a pathway for inland users of the Colorado River to benefit from investments in coastal desalination. San Diego water officials highlighted the role of the Carlsbad Desalination Plant, the nation’s largest seawater desalination facility, which produces up to 54 million gallons per day.
The MOU identifies areas for further study, including legal and policy frameworks for interstate exchange, pilot projects, shared agency responsibilities, and potential federal funding.
The agencies say they hope to determine within the next two years whether a pilot framework can be developed.
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Any pilot program would face legal, regulatory and operational hurdles. The MOU instructs participants to review the legal and policy framework for interstate exchanges and emphasizes that future agreements must adhere to water rights, contracts and federal law.
The next phase will assess whether a pilot exchange can be structured under Colorado River rules, involving desalinated seawater from Carlsbad and recycled wastewater, and will assess federal funding needs.
“Next-generation strategies in the face of climate volatility must include interstate partnerships that deliver water where it’s needed most,” San Diego County Water Authority CEO Dan Denham said in a joint agency statement.
“This is an important step in addressing the goal of increasing water supplies from the Colorado River by creating a mechanism to deliver those supplies through an interchange using existing infrastructure,” said Tom Buschatzke, director of the Arizona Department of Water Resources, adding, “It represents the type of innovation that Arizona and its partners in the Lower Basin believe is necessary for the entire Colorado River state to help stabilize the system in the long run.”
The parties said any future exchange would not alter existing water rights and would depend on existing delivery systems.
