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The Metropolitan Water District of Southern California

Desalination is a process that removes some amount of salt and other minerals from saline water. Salt water is desalinated to produce fresh water suitable for human consumption or irrigation. Along with recycled water, this is one of the few rainfall-independent water sources. 

There are numerous methods for desalting seawater, but the most common involve thermal distillation and membrane separation processes, including Reverse Osmosis, the dominant technology in the United States.

​Metropolitan has been considering seawater desalination as a potential new supply since the 1960s. In the early 1990s Metropolitan developed and pilot tested its own thermal distillation technology. However, the cost of seawater desalination was not competitive with other resources at that time. In the past 10 years, rapid improvements in membrane performance, energy recovery technology and process design have lowered seawater desalination costs to the point where it is now more competitive with other new supply options.

In response to member agency interest, Metropolitan created the Seawater Desalination Program in 2000 to provide financial incentives for its member agencies to develop desalinated water.