Myths of California Water: Virtual Tour

Seawater desalination may be useful for isolated coastal urban areas cut off from the state’s supply network, and as a reliable partial supply for urban areas dependent of imported water. Reliability is the primary motivation for the planned desalination facilities in San Diego and Orange Counties.

Even with continued technological advances, seawater desalination is likely to remain relatively costly for urban uses, and is unlikely to become viable for directly supplying water for agriculture. The Metropolitan Water District is subsidizing the production of water at the Poseidon Desalination Plant by $250 an acre foot to make it comparable to other new water sources for the region.

Desalination poses environmental problems: trapping marine life at intakes, disposal of brine by-product, and high energy use. The cost of brine disposal and environmental mitigation is expensive in California. The above model portrays the projected discharge of brine byproduct into the ocean by Poseidon. Poseidon’s proposed intake is downstream of the Aqua Hedionda Lagoon, home of several endangered species.

Current use of desalination is limited. Southern California desalinates brackish water (much less saline than seawater) in inland areas. On the coast, Santa Barbara built an emergency desalination plant in response to the 1990-1991 drought, but abandoned its use due to high costs.

Desalination can contribute to California’s water supply solutions, but it is not a cure all because of costs and environmental concerns. In most cases, the money spent on desalination would be better spent on other improvements, such as rehabilitation of aging facilities, improved conveyance, water conservation, and flexibility in operations.