Seawater desalination plant might be just a drop in the bucket

Dreamers have long looked to the Pacific Ocean as the ultimate answer to California's water needs: an inexhaustible, drought-proof reservoir in the state's backyard. In the last decade, proposals for about 20 desalting plants have been discussed up and down the coast. 

But even with construction about to begin on the nation's largest seawater desalination facility, 35 miles north of San Diego, experts say it is doubtful that dream will ever be fully realized.

"While this Poseidon adventure may work out, I don't look for a lot of that," said Henry Vaux Jr., a UC Berkeley professor emeritus of resource economics who contributed to a 2008 National Research Council report on desalination.

The reasons boil down to money and energy. It takes a lot of both to turn ocean water into drinking water, driving the average price of desalinated supplies well above most other sources.

The purified water produced by the Poseidon Resources plant will cost the San Diego County Water Authority more than twice what it now pays the Metropolitan Water District of Southern California for supplies from Northern California and the Colorado River. Over the authority's 30-year contract with Poseidon, San Diego County ratepayers will pay between $3 billion and $4 billion for the desalted water, which is expected to provide no more than a tenth of their overall supply.

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