Thanks to recent advances in technology, turning ocean water into drinking water is not as energy-intensive as it was a decade ago. And as the cost of treating and conveying water from other sources continues to rise, ocean desalination is beginning to become economically feasible in some coastal areas that rely on imported water supplies.
Many local water agencies are looking at ocean desalination as a way to provide a more reliable supply of water during droughts and to reduce reliance on the Sacramento-San Joaquin Delta and Colorado River.
Thanks to funding made available by recent statewide bond measures, local agencies have secured financial assistance to move ahead with feasibility studies, pilot projects and other research into desalination. Many agencies are exploring ocean desalination as part of their integrated regional water management plans to help meet water resource management goals and objectives in their regions. Such plans usually include water recycling, increased water use efficiency, groundwater storage and conjunctive use and other local strategies.
CalDesal, a non-profit organization composed of water industry leaders, is helping lead efforts to expand ocean desalination where feasible by advocating for funding and policies to promote use of this important technology.
The 1987-1992 drought ignited a wave of interest in desalination, particularly in Central Coast communities that experienced serious water shortages. Although several pilot projects were launched, most did not lead to full-scale desalination plants. More recently, consecutive dry years in 2007, 2008 and 2009, and restrictions on deliveries from two of the state's biggest water supply sources, the Sacramento-San Joaquin Delta and the Colorado River, renewed interest in tapping the Pacific Ocean where feasible to provide a more reliable supply.
According to the Department of Water Resources (DWR), California has seen surge of interest in desalination in the past decade. In addition to several small ocean desalination plants in operation today, there are more than a dozen larger projects in various stages of planning, design and construction. Numerous studies are also under way to investigate the feasibility of seawater desalination up and down the coast. If all or even some of these are eventually built, the state's ocean desalination capacity will increase dramatically and help meet California's urban water needs.
Today, at least 13 ocean water desalination projects are under consideration that together could produce more than 257,000 acre-feet of water each year.
In Southern California, an ocean desalination plant that will produce 56,000 acre-feet of water annually is now under construction near Carlsbad. The project, owned by Poseidon Resources, is considered the first large-scale ocean water desalination plant in California. The San Diego County Water Authority Board of Directors has approved the purchase of the water produced by the plant, which by 2020 will produce enough water to meet about 7 percent of the region's water needs. This will reduce San Diego's dependence on imported water and significantly improve water reliability in the region.
Additional projects are proposed in Huntington Beach, Dana Point, Long Beach and the South Bay region of Los Angeles. Projects are also in various stages of study and approval by Marin Municipal Water District, Cambria Community Services District, the City of Santa Cruz and Soquel Creek Water District, the Monterey area and a potential joint project by the Contra Costa Water District, East Bay Municipal Utility District, Santa Clara Valley Water District and San Francisco Public Utilities Commission.
Most desalination projects use one of two basic technologies. Reverse osmosis (RO) involves forcing ocean water or brackish water through membranes or filters that screen out salt and other minerals. The second method is distillation, in which ocean water is heated to produce steam. The steam is then condensed, and the end product is water with a low concentration of salt and impurities. Most of the recent proposals under consideration in California would use reverse osmosis.
Depending on the technology used, ocean water desalination can produce water of exceptionally high quality. It can also allow coastal communities to reduce their dependence on imported water supplies and provide a reliable source of water even during droughts.
Although the cost and energy requirements of ocean desalination may be coming down, desalination is still costly relative to other supply alternatives. There are also potential environmental impacts associated with the intake of marine organisms and the disposal of the brine produced in the desalination process.
CalDesal believes ocean desalination is one of many strategies that can play a role in boosting the state's water supply and overall reliability. Given the rising cost of building and operating surface water reservoirs and conveyance systems, and recent improvements in desalination technology, ocean desalination is likely to play a larger role in California's future.
CalDesal is a leader in advocating funding and policies that promote the use of desalination where feasible in California.