California is defined by its long coastline and perpetual struggle with water scarcity, creating a paradox: the world’s largest ocean sits next to a region constantly facing drought. Desalination, which removes salt and impurities from seawater, offers a nearly limitless supply, yet it remains a marginal source of water for the state. Widespread adoption is blocked not by technical feasibility, but by extreme financial costs, significant environmental trade-offs, and a complex regulatory framework.
The Significant Financial and Energy Burdens
The primary obstacle to large-scale ocean desalination is the overwhelming financial burden, both in construction and operation. Building a major seawater reverse osmosis plant often requires a capital investment exceeding a billion dollars, an upfront cost far higher than most alternative water supply projects. This initial outlay must be recovered, forcing the resulting desalinated water to be sold at a much higher price point.
Seawater desalination is consistently the most expensive supply option available to California communities. Desalinated water typically costs between $2,100 and \(2,800 per acre-foot to produce, making it two to five times more expensive than established sources like the State Water Project (\)600 per acre-foot). This high cost means local water agencies must exhaust nearly all other options before turning to ocean water.
The operation of a reverse osmosis plant requires immense amounts of energy to force seawater through semi-permeable membranes against natural osmotic pressure. Seawater is more energy-intensive to treat than other sources because its high salinity necessitates greater pumping power. Desalination can require three to ten times more energy than treating and recycling wastewater. This high energy demand creates a large carbon footprint and contributes substantially to the overall operational expense.
The high energy requirement places a strain on the state’s electrical grid, especially in a state prioritizing renewable energy and greenhouse gas reductions. While the energy needed to pump desalinated water is comparable to the energy used to pump imported water over California’s mountain ranges, the total cost of production remains prohibitively high for most communities. Until the cost of this energy-intensive process drops significantly, desalination will remain a last-resort supply option.
Protecting Coastal Ecosystems: Brine Disposal and Intake Issues
A major barrier to desalination is the strict environmental regulations governing how plants interact with the marine environment, specifically concerning water intake and byproduct disposal. To convert seawater into fresh water, a plant must draw massive volumes of ocean water, threatening marine life through entrainment and impingement. Entrainment occurs when small organisms, such as fish larvae and plankton, are sucked directly into the intake pipes and killed. Impingement is the trapping of larger organisms, like fish and invertebrates, against the intake screens by the force of the flowing water.
California’s Ocean Plan requires new or expanded facilities to use the best available technology to minimize marine mortality, strongly preferring subsurface intake systems (SSIs) where feasible. SSIs draw water through the sand or seabed, which naturally filters the water and prevents most marine life from entering the system. Implementing SSIs is complex and costly, and in many locations, the geology makes them technically unfeasible, forcing proponents to find and fund other mitigation measures.
The second major environmental challenge is the disposal of the concentrated salt byproduct, known as brine. The reverse osmosis process typically produces brine that is about twice as salty as the ambient ocean water. If discharged directly, this hypersaline plume is denser than seawater and can sink to the ocean floor, forming a “dead zone” that suffocates bottom-dwelling organisms.
To prevent ecological damage, state regulations often require the brine to be rapidly diffused and diluted before it reaches the environment. One common mitigation strategy is commingling the brine with less-salty wastewater discharge from a nearby treatment plant, which helps dilute the concentration before release far offshore. This regulatory requirement for careful brine management adds substantial engineering complexity and cost to every project.
Navigating California’s Regulatory and Permitting Maze
Even with a technically sound and environmentally compliant design, desalination projects must navigate an exceptionally challenging regulatory landscape unique to California. The California Coastal Commission (CCC) holds significant authority over projects within the coastal zone and can approve or reject them based on the policies of the California Coastal Act. The CCC often prioritizes the protection of coastal resources and marine life, which frequently leads to lengthy delays and project redesigns.
The state’s primary environmental law, the California Environmental Quality Act (CEQA), mandates a comprehensive and often years-long review process for any project that could significantly affect the environment. This process requires extensive studies and provides multiple avenues for public challenge and litigation, extending the timeline for project approval significantly. A project that may take two to three years to permit in other states can easily take a decade or more in California.
This regulatory complexity and the inherent delays create significant financial uncertainty for developers and investors. The unanimous rejection of the large Huntington Beach desalination proposal by the CCC in 2022, despite years of planning, highlighted the high bar for approval and the political risk involved. Only projects demonstrating superior environmental designs, such as the smaller Doheny project that utilized subsurface intakes, have successfully gained approval.
The Physical Challenge of Water Distribution
The final constraint is the physical challenge of moving the newly produced fresh water from the coast to major population and agricultural centers. Desalination plants must be sited directly on the coastline to access the ocean, but many of California’s largest water users are located far inland. The Central Valley, a massive agricultural region, and large portions of Southern California are separated from the coast by significant mountain ranges.
Moving the water from sea level to these inland areas requires extensive new infrastructure, including high-capacity pipelines and powerful pumping stations. Pumping water uphill against gravity adds significantly to the energy consumption of the project, compounding the already high energy costs associated with reverse osmosis. This logistical difficulty further increases the cost of desalinated water for inland users.
Integrating a massive new water source into the existing, complex network of canals, aqueducts, and reservoirs also presents a major engineering hurdle. The geographical reality of California means that desalinated water is most beneficial to coastal communities, which can use it locally to reduce their reliance on imported water. For the state as a whole, the sheer scale of the distribution challenge limits ocean desalination’s role as a primary, statewide water solution.