Early next year, the Southern California town of Carlsbad will break ground on a plant that each day will turn 50 million gallons of seawater into fresh drinking water.

The $320 million project, which would be the largest desalination plant in the Western Hemisphere, was held up in the planning stages for years. But a protracted drought helped propel the project to its approval in May -- a sign of how worried local authorities are about water supplies.

"Water is going to be very short until you have a new source," said Carlsbad Mayor Claude Lewis. "And the only new source is desalination, I don't care what anybody says."

The desalination plant would use water that flows by gravity from the ocean across a manmade lagoon and into the facility through 10 large pumps. The plant would then blast it through a filter, extracting fresh water and leaving behind highly pressurized salty water. The process would provide enough water for 300,000 people each day.

Government agencies have opposed desalination because of the process's energy consumption. The desalination plant would use nearly twice as much energy as a wastewater-treatment plant available in Orange County. Environmental groups also object because fish and other organisms are likely to be sucked into the facility.