State transportation officials say they plan to fix broken sprinklers along San Diego County freeways so they spray plants instead of traffic.

Pedro Orso-Delgado, director for the California Department of Transportation's San Diego and Imperial counties district, said Friday that Caltrans also plans to change the timing so sprinklers water at night or early in the morning, instead of during the midday heat.

And Caltrans is preparing to rip out lush and thirsty landscaping that adorns some highways and interchanges, and replace it with native plants that use less water, Orso-Delgado said.

Orso-Delgado made the comments during a San Diego County Water Authority presentation on the state of the local water supply to the San Diego Association of Governments board.

He said Caltrans doesn't want to be seen as wasting water at a time when water providers are warning customers throughout the region to cut back on watering or face sharply higher utility bills,

The board took no action. But a few board members offered suggestions on how to ensure San Diego County has enough water for the future.

Board member Carrie Downey of Coronado suggested water agencies borrow a page out of the electric utilities' playbook and charge customers not only based on how much water they use, but on when they use it. If it cost more for people to water at midday, she said, they would be more likely to sprinkle at cooler times when there is less evaporation and wind.

County Supervisor Bill Horn, who also sits on the board, suggested water providers invest heavily in desalination plants, like the one being pursued in Carlsbad that will take ocean water and remove the salt so people can drink it.

"We ought to have 10 desal plants," Horn said.

County water authority officials are counting on the Carlsbad plant, expected to come online in 2012, to help slake future thirst. They also are exploring building a plant with the Marines on Camp Pendleton Marine Corps Base that would provide additional water for the base and the region as a whole.

Paul Lanspery, deputy general manager for the water authority, said this summer's projected 8 percent reduction in the countywide supply is in essence "the equivalent of a Carlsbad desalination plant."

The area is short because of a third straight dry winter in the Sierra Nevada. The shortage also is the result of environmental-based restrictions for pumping water from the Sacramento-San Joaquin delta, the place where melting Sierra snow ends up.

"The water supply shortage this year was caused by a broken bay delta," said authority board member Mark Muir of the Olivenhain Municipal Water District.

Oceanside Mayor Jim Wood joked that the region ought to invest in a fish farm that raises delta smelt -- the tiny fish that triggered the restrictions -- and send shipments of smelt to the delta.

"We throw humor on it, but let's face it, this is the most important commodity we have here in Southern California," Wood said. "It's like gold."

Contact staff writer Dave Downey at (760) 745-6611, Ext. 2623.