Is seawater desalination right for California?

June 29, 2023
With an unclear future for the state's freshwater sources, California's interest in seawater desalination continues to grow.

Support for desalination in California is growing.

Currently, California has 12 seawater desalination facilities, but only two are of a significant size. Although a key state agency has recently approved plans for two more moderate size facilities, the perception of seawater desalination in the state is quite poor and project proposals face a steep uphill battle. The approval process is lengthy, expensive, difficult, and oftentimes has little public support.

Recently, the California Coastal Commission rejected Poseidon Water’s controversial bid for a 50 million gallon per day (mgd) desalination facility in Huntington Beach, costing the company 20 years and $100 million.

However, with projections that climate change could bring even more extreme droughts in the future, desalination is a topic that comes up often in public and private discourse. Three key factors are driving this change:

  • Diversified water portfolios;
  • Green energy transition; and
  • Environmental benefits may outweigh concerns.

Diversified water portfolios

Climate change increases the need for diversified water infrastructure, and desalination is the only truly “drought-proof” source.

In some regions, it is only turned on when other sources and strategies are insufficient. This approach has been invaluable in locations with a similar climate and drought patterns to California, such as Australia, Spain, and South Africa. California Governor Gavin Newsom said that climate change could shrink the water supply by 10%.

It may seem strange to discuss drought during a year of record rainfall, but climate scientists predict this is California’s future: longer and more frequent droughts alternating with periods of more intense storms. Desalination has a role to play. It will not be the first choice everywhere, but may be the best choice in several coastal communities.

Green energy transition

Water and renewable energy demands are interlinked, and load balancing is becoming more important as renewables become a greater source of our energy supply. Load balancing can make desalination a more sustainable and less costly solution than competing water supplies.

Desalination uses more energy than traditional water supplies (e.g., lakes, rivers, and wells) and most potable reuse projects. However, as potable reuse treatment and associated pumping schemes become complicated due to fewer ideal locations indirect potable reuse, this will change. In some cases, seawater desalination will use less energy than competing direct potable reuse projects.

In contrast with potable reuse, desalination plants do not require diversion when not in use and thus can be easier to power on and off as needed when excess renewable energy is available (a.k.a., load balancing). Operating desalination plants when excess green energy is available also reduces the cost of energy storage needed, which represents a massive value in terms of grid infrastructure investment.

Recent advancements in existing technologies (such as more efficient pumps, energy recovery devices, and membranes) are further reducing the energy needed for desalination. For example, wave power and green hydrogen are starting to show promise in powering facilities in areas where solar and wind energy are not as accessible. Furthermore, the U.S. EPA, Department of Energy, Bureau of Reclamation, and state agencies are actively investing in research and new technology to further reduce the energy and costs of desalination, recognizing its key role as a drought mitigation tool.

Environmental benefits may outweigh concerns

Decades of data show proper plant design and location can mitigate the environmental impact of desalination, while also protecting ecosystems within the same watershed. In California, desalination may be the best option to help restore key aquifers, habitats and salt lakes.

There are many websites that claim desalination as harmful to the environment — many based on a recent study in Science of the Total Environment— but those sites do not provide historical data of success stories or context to properly assess the risks. A nuanced conclusion from the report is that improper design or the wrong location can lead to significant environmental impacts.

The adage, “location, location, location” holds just as true in desalination as it does in real estate. Data from desalination facilities around the world indicate that location and proper design are the two most important factors to minimize environmental impacts and provide benefits to local and distant ecosystems that share the same drinking water source.

Carefully choosing the location of a facility has several benefits. Such considerations include:

  • Choosing an intake location far away from key reproductive areas or one that allows the use of seawater wells to minimize entrainment of eggs and larvae into the intake.
  • Choosing an outfall location with proper mixing allows for infrastructure to create high velocity jets into existing tidal or other mixing areas, such that the impact of the salty brine cannot be measured a few meters away from the discharge and also allows adequate flushing so that excess salt cannot accumulate in that area.
  • Choosing the right plant location minimizes impacts to the coastline and seafloor.

Australia is an excellent example of prioritizing location and optimizing designs. More than a decade of monitoring has shown no measurable impact to the environment from seawater desalination intakes or outfalls in cities. Plants in Israel, Spain, California, and elsewhere have copied this approach to the extent that these types of concerns are only valid if proper siting and design trends are ignored.

Protecting freshwater sources

Additionally, desalination plants are globally becoming more important as a way to offset water diversions from lakes, rivers, and groundwater aquifers as water supplies dwindle. Water scarcity impacts entire ecosystems including wildlife, forests, soils, and natural processes that are taken for granted.

Desalination can restore key aquifers, reservoirs and salt lakes if implemented properly. Historically, agricultural users turn to groundwater during periods of drought — this led to the overdraft of the Central Valley’s aquifer

If urban areas such as the San Francisco Bay Area, San Diego County, Orange County, and Los Angeles County – which share state project water with agricultural users – utilized desalination during droughts, that would provide more water for inland and agricultural users to reduce over-drafting of aquifers. Furthermore, operating desalination at other times may allow for additional recharge of these aquifers to store water, combat land subsidence, and provide other benefits.

Severe drought conditions have threatened to stretch California’s reservoirs to the limit, and it is likely that some towns could run out of water during a future unprecedented drought. Even the Colorado River, which has historically been perceived as an invulnerable source of freshwater, is a source of concern after the U.S. government issued a shortage declaration last summer and required several states reduce their intake. California voluntarily reduced its intake by 9% in 2023.

“The system is approaching a tipping point,” said Camille Calimlim Touton, an official with the U.S. Department of the Interior, of the Colorado River, in an article from Grist by Zoya Teirstein and Jake Bittle. “Without action, we cannot protect the system and the millions of Americans who rely on this critical resource.”

Overdrawing natural freshwater can be disastrous in other ways for nearby communities and wildlife. California’s Salton Sea is a cautionary tale. After it was cut off from its source, the Colorado River, the lake began steadily drying up, growing more saline and toxic due to pollution from nearby agriculture. The lake’s population of fish has been decimated and dead fish wash up on its shores in astonishing numbers.

As the Salton Sea continued to shrink, it created additional environmental impacts, including concern of new die offs of the vast amount of birds and organisms that access its habitat, and rates of asthma 10 times the national average from the toxic dust left behind as the water recedes. A recent state-led report recommended coastal seawater desalination as a potential source of water to restore the Salton Sea, by sending water to the lake instead of coastal urban areas, which could instead be supplied by desalination.

Even with recent record breaking rainfall in California, water will always be an urgent need in California and in the Colorado River watershed. It is vital to protect existing freshwater sources, especially in times of extreme drought.

Australia has faced the same dilemma and turned to desalination as a backup source of water supply. California can utilize this model, but it needs to act more decisively. The recently-approved Doheny Ocean Desalination Project has been in the works for more than 15 years, and will take an estimated three more years to design and build.

Depending on how quickly the next severe drought period occurs, the Salton Sea, aquifers in the Central Valley and perhaps other key parts of California cannot afford to wait another 20 years to build more desalination plants in the appropriate locations and for appropriate reasons.

Just as California has expedited the construction of renewable energy, it should treat water infrastructure the same way. WW

About the Author

Erik Desormeaux

Erik Desormeaux is Energy Recovery’s Director of Application Development. He is a professional civil engineer with over 18 years of low-pressure membrane experience including participating in the planning, design, and construction of multiple brackish desalination and potable reuse projects in California.