LOS ANGELES (Reuters) - With a recent flurry of winter storms doing little to dampen California’s latest drought, the nation’s biggest public utility voted on Tuesday to impose water rationing in Los Angeles for the first time in nearly two decades.

Under the plan adopted in principle by the governing board of the L.A. Department of Water and Power, homes and businesses would pay a penalty rate -- nearly double normal prices -- for any water they use in excess of a reduced monthly allowance.

The five-member board plans to formally vote on details of the measure next month.

The rationing scheme is expected to take effect in May unless the City Council acts before then to reject it -- a move seen as unlikely since Mayor Antonio Villaraigosa called for the measure under a water-shortage plan last week.

The only other time such penalty pricing was imposed to force conservation in the nation’s second biggest city was a rationing system put into effect for a year starting in March 1991, at the height of California’s last statewide drought.

That measure cut citywide water use by about 25 percent, DWP spokesman Joseph Ramallo said.

The DWP board also voted unanimously to restrict lawn sprinkler use to two days a week, as urged by the mayor. Outdoor irrigation accounts for 40 percent of residential water use in the city, DWP officials say.

The agency is the largest municipal utility in the United States, supplying water and electricity to some 3.8 million households and businesses in Los Angeles.

San Diego and other cities throughout California are weighing similar measures to cope with a water shortage that is adding to the woes of a state beset with rising unemployment, high mortgage foreclosure rates and a budget crisis.

DROP IN THE BUCKET

The snowpack in the Sierra Nevada mountain range, one of the state’s chief sources of fresh surface water, is far below normal, and reservoirs fed by Sierra runoff are badly depleted as well, due to a statewide drought now in its third year.

State water managers have said the current dry spell could prove to be the worst ever in California, owing to rising demands from steady population growth.

Recent heavy rains, and mountain snowfall, have provided a welcome respite from California’s driest January on record, but “this latest set of storms did not get us out of the woods by any means,” water manager James McDaniel told the DWP board.

Complicating matters are federal court restrictions on water that can be pumped from the Sacramento-San Joaquin Delta in northern California, which furnishes much of the state’s irrigation and drinking supplies, in order to protect endangered fish species.

As a result, state water managers have cut the amount of delta water they provide to irrigation districts and cities around the state to 15 percent of their usual contracted allotment for the year and may curb those deliveries further.

Another major source of imported water to Southern California, the Colorado River basin, is emerging from an eight-year drought, but its reservoirs remain low.