Despite conservation measures, California is currently using an unsustainable amount of water. Whether the water is sourced from the dwindling Colorado River or largely depleted local groundwater, California cannot access enough water from present stocks to meet demand for decades to come. There are a variety of ways to meet this challenge, including wastewater reprocessing, conservation, elimination of thirsty crops, and desalination.

California’s water policy decisions can have tremendous implications for people living in other states. Fully 25% of Southern California’s water comes from the Colorado River, which also serves people gripped by drought in Mexico and other US states. Lake Mead, the Colorado River reservoir that is tapped to supply people in Southern California, now stands at its lowest level since it was first filled. If its level drops by another 40 feet, which it could well do by 2024, the Hoover Dam hydroelectric power station will no longer be able to operate.

People in other states have no recourse besides the Colorado River. California, however, has the Pacific Ocean. Can the mighty Pacific be the solution?

A natural-color image shows the water level of Lake Mead located in Nevada and Arizona on July 6, 2000. (Lauren Dauphin/NASA Earth Observatory via Pagransen)
A natural-color image shows the water level of Lake Mead located in Nevada and Arizona on July 6, 2022. (Lauren Dauphin/NASA Earth Observatory via Pagransen)

Desalination background 

Desalination has the obvious advantage of being 100% drought-proof; the ocean will never dry up. Unfortunately, desalination produces a gallon of brine (water twice as salty as the source water) for every gallon of pure water. It is currently not economical to extract the salt or minerals from this brine, so it needs to be rejected as waste. To avoid killing aquatic life with the brine, desalination plants typically mix the brine with other wastewater before letting it flow into the ocean.

Although recent improvements in technology have made it more energy-efficient, desalination is also energy intensive. There’s a strong argument to be made that California’s already-overtaxed power grid cannot afford the added burden of more desalination plants. Indeed, Carlsbad desalination plant recently cut output to prevent blackouts.

Existing and planned desalination projects 

At present, California desalinates about 229,000 acre-feet per year (AFY) of water, enough to supply around 500,000 households, according to California’s official water supply strategy. Carlsbad desalination plant in San Diego County, the largest desalination plant, accounts for 56,000 AFY. Other notable desalination plants include a 8,400 AFY plant in Oxnard and the 3,125 AFY Charles E. Meyer facility in Santa Barbara. Most of the existing desalination in the state uses “brackish water” (groundwater too salty to drink) rather than ocean water.

Several new desalination facilities are being approved or are already under construction. A new plant in Antioch would supply 5,500 AFY, and the proposed Doheny desalination plant near Anaheim, which would produce 5,500-6,000 AFY, has thus far won endorsements from all the policymakers who would need to approve it. In response to questions, Albert Lundeen of the California Natural Resources Agency said that “prioritizing locations” for new desalination plants is “one of the tasks the State Water Resources Control Board and other state agencies will be working on.”

Reverse osmosis pressure canisters separate pure water from brine in the Carlsbad desalination plant. (Carlsbad Desalination Plant)

At the same time, the most ambitious desalination projects proposed in recent years have seen little or no public interest. In 2021, Stanford professors floated a proposal to create a desalination plant at Diablo Canyon nuclear power station. This desalination plant would have been even larger than Carlsbad, capable of supplying an estimated 70,000 – 80,000 AFY. However, given that the current legislative plan has Diablo Canyon shutting down for good in 2030 at the latest, it likely would not be economical to build a desalination plant there without the assurance of a replacement source of power. Another ~55,000 AFY project that would have been built in Huntington Beach was not able to go forward chiefly due to environmental concerns raised from several quarters.  

Deepwater Desal, a privately owned firm that had proposed a 25,000 AFY desalination plant in Moss Landing, withdrew its plans in June 2021 due to lack of public buy-in.

Alternatives to desalination 

To some extent, desalination conflicts with wastewater recycling, because the wastewater that is used to dilute the brine could instead be recycled. However, desalinated water is suitable for drinking while recycled wastewater must be treated quite extensively to make it potable. Recycled wastewater is typically only processed enough to make it suitable for landscape irrigation and other uses that don’t require purity.

Another low-cost use for treated wastewater is to inject it back into underground aquifers to replenish groundwater. The revolutionary Groundwater Replenishment System (GWRS) in Orange County has shown that it is possible to get drinking water from wastewater at a reasonable cost. In addition to being cheaper than desalination, the GWRS produces 110,000 AFY of water and has a planned expansion to bring its production up to 143,000 AFY, more than half the combined capacity of all existing and planned desalination projects in the state.

The most obvious way to avoid needing desalination is to simply use less water. Since 80% of human water use in California is agricultural, strategic cuts to agriculture can matter at least as much as deep cuts to urban water use. For example, one pound of cheese can require well over 3,000 gallons of water to produce, while a pound of nuts may require over 2,000 gallons of water. For context, 2.6 billion pounds of almond production are projected for 2022, so almonds alone will likely consume at least 16 million acre-feet of water this year. Alfalfa, which is used almost exclusively to make hay for cattle, uses 12% of California’s water and is grown primarily in Southern California.

Desalination versus cutbacks to agriculture 

Desalination’s cost, environmental issues and inadequacy to meet massive deficits are clear to many environmental organizations. According to Chirag G. Bhakta, director of Food & Water Watch, “desalination is an expensive, inefficient scheme” that “raises the price of water, risks irreparable damage to the environment, and requires massive amounts of energy that frequently call for the use of fossil fuels”. Bhakta recommends that Californians instead “stop siphoning our precious water resources off to extractive industries like industrial agriculture and fossil fuel production”.

Alvar Escriva-Bou of the Public Policy Institute of California is not so strongly opposed to desalination, but believes that its drawbacks mean it should only be a last resort for communities with no other options. Escriva-Bou said that “desalination won’t provide 20% or even 10% of California’s water, but it might be important at the local scale.” He suggested that water recycling might be a more important option, especially for coastal communities who would otherwise discharge their wastewater back into the ocean. As to the utility of cuts to agriculture as a water security measure, Escriva-Bou pointed out that “80-90% of agriculture in California is actually sustainable” and “farmers have been innovating and reducing water consumption over the last few years”.

Denise Davis of the California Chamber of Commerce argued that “desalination should play a key role in California’s future water security policy. As droughts lengthen and increase in frequency, it is important that we have ‘drought-proof’ water sources online”. She pointed out that agricultural land is already being fallowed in response to the drought, and observed that agricultural water in California “is being used to produce high-quality fruits, vegetables, and other specialty crops, many of which can be grown nowhere else in the nation.”

Multiple approaches needed 

While desalination has significant benefits and will remain part of California’s strategy for coping with drought, not even the most ambitious plans for expanding desalination can bring California to water sustainability by themselves. Other measures, like increasing storage, reducing the water demand of agriculture, and improving water recycling, will be necessary to achieve anything close to long-term sustainability. California’s current water supply strategy only envisions new desalination plants providing 80,000 AFY out of 7 million AFY (about 1%) of total water supply increases by 2040.

And in the end, it is clear that someone must pay for our overconsumption of water, be it people living in depleted groundwater basins, Mexican farmers, domestic dairy farmers, foreigners who now buy California almonds, or people living near desalination plants.