SAN FRANCISCO  The vast $320 million desalination plant approved this week by San Diego’s regional water authorities is likely to serve as a test case for whether such a large project can meet its goals while safeguarding its Pacific environment.

The plant, to be built near Carlsbad, north of San Diego, will be the first large-scale desalination operation on the West Coast and the largest in the hemisphere. “If they build it well and it operates well and the price is right, we will see more,” said Peter Gleick, the cofounder and president of the Pacific Institute in Oakland, Calif.

“I think there’s going to be some hesitancy to really expand desalination until this plant is up and running,” he added. “There’s going to be hesitancy on the part of everyone  regulators, water agencies and municipalities.”

Other ambitious desalination projects are being considered along the California coast, from Marin County just north of San Francisco to Santa Cruz, Monterey, Long Beach and Huntington Beach. Cities, water companies and environmentalists are likely to scrutinize how the plant near Carlsbad performs financially and technically and weigh its environmental impact.