Federal Options for Large Scale Seawater Desalination

The Carlsbad desalination plant is reportedly operating at half-capacity, basically because it’s less expensive to import water from the Colorado River. That is likely to change, as Arizona’s Department of Water Resources is negotiating with the San Diego County Water Authority to purchase some of the water they get from the Colorado River. The funds from Arizona will defray some of the cost to increase output from the desalination plant.

This is a mutually beneficial exchange that leverages the fact that California cities get water from the Colorado River at a cost that is way below what urban water agencies in Arizona and Nevada are willing to pay. It is a model that can be scaled. As discussed in WC #132, up to 800,000 acre feet per year of California’s withdrawals from the Colorado River could be sold to water agencies in Arizona and Nevada in exchange for those out-of-state agencies paying for construction of seawater desalination plants on the California coast.

At an estimated cost of $15 billion to build 800,000 acre feet per year of freshwater capacity, the financing cost for these desalination plants (4%, 20 years) would be $837 per acre foot. With out-of-state water agencies picking up construction costs via this exchange, ratepayers in California’s coastal cities would only have to pay operating costs for desalinated water. It’s a win-win.

The problem with seawater desalination isn’t affordability. If the construction costs are covered, then the energy costs are manageable even at California’s inflated prices. At $0.30 per kilowatt-hour, based on 3,500 kWh per acre foot of desalinated water, electricity costs $1,050 per acre foot, leaving plenty of room for any other operating costs while staying within retail prices. Treated water from the Metropolitan Water District of Southern California costs around $1,500 per acre foot, and that price is predicted to nearly double within the next ten years. Meanwhile, the cost of electricity in California is bound to drop; the wholesale price is already closer to $0.08 per kWh. At that rate, electricity costs for desalinated water plummet to $280 per acre foot.

With these economics, large scale desalination plants are a compelling option toward Californians achieving not just water security, but water abundance. But standing firmly in the way are state regulatory agencies. Without devoting the paragraphs necessary merely to cite the names of every state and local agency that can veto a desalination plant, it is sufficient to note that the contractor seeking approval for a desalination plant in Huntington Beach spent over 20 years and over $100 million submitting designs and permit applications, only to be shot down while attempting to clear the final hurdle. In May 2022, after all that work, the California Coastal Commission voted unanimously to deny approval, and the project died.

There’s another way to bring large scale desalination to California, however, and that’s for the federal government to construct seawater desalination plants on federally owned land along the California coast. Two pathways exist for Washington to advance desalination on suitable federal coastal sites.

The first relies on existing federal authority. Minor amendments to the Coastal Zone Management Act and its regulations could clarify that federally assisted or authorized projects qualify as federal activities, exempt from state consistency reviews. A streamlined 120 day process could allow the president or Secretary of Commerce to issue early paramount-interest exemptions when national commerce or security is at stake.

Under the Submerged Lands Act, executive or legislative clarification could affirm that paramount rights for interstate and foreign commerce override state proprietary claims for water-related infrastructure. A presidential executive order could direct agencies to prioritize and expedite such declarations, while the Department of the Interior or Navy identifies viable federal parcels, especially at naval bases or harbors where submerged lands exceptions apply. These steps require no new major legislation.

The second option involves congressional action: targeted legislation declaring large-scale desalination on coastal federal lands a matter of national security, interstate commerce, and international trade. Invoking the Supremacy Clause, such a law would preempt conflicting state and local rules on siting, permitting, and operation. A new federal permitting framework would replace the current fragmented system. Complementary reforms could streamline National Environmental Policy Act reviews or Endangered Species Act consultations for critical water projects.

We may hope that aggressive federal action to advance large scale seawater desalination will be welcomed by those politicians and agency bureaucrats in California who recognize the important role that large scale desalination can play in securing adequate water supplies for the state. We may also hope the case for desalination is compelling enough to make it a bipartisan imperative that will retain its momentum at the federal level regardless of which political party controls the U.S. Congress or the White House.

Finally, we must hope that proponents of other water supply options in the state will accept seawater desalination as a vital element in a total state strategy. Everyone knows that the biggest variable affecting California’s water supply for farms and cities is how we manage the Sacramento-San Joaquin Delta. Just modifying how we predict and manage reservoir storage, and regulate pumping to the aqueducts, could add millions of acre feet per year. Investing in cost-effective new projects in the delta with huge potential – for example, dredging the clogged channels and building fish friendly subsurface intake systems – could add additional millions of acre feet per year.

But when it comes to California’s massive coastal cities, home to more than 25 million people and precariously dependent on imported water, seawater desalination is the third leg of the stool, with the other two legs being runoff harvesting and wastewater recycling. Add to that large scale desalination, and our whole state has a much better chance to permanently tip the scales, from chronic water scarcity to enduring water abundance.

Edward Ring is the Director of Water and Energy Policy at the California Policy Center, which he co-founded in 2013. Ring is the author of Fixing California: Abundance, Pragmatism, Optimism (2021) and The Abundance Choice: Our Fight for More Water in California (2022).