The regional authority that delivers more than half of Southern California's water has tightened rations for the third time in as many months as it tries to cope with the state's five-year drought.

The order approved Tuesday forces homes and industries to cut water use by 20 percent and farms by 50 percent. The Metropolitan Water District previously had imposed cuts of 10 percent for homes and industries and 30 percent for farmers."Our concern is that even in a normal rainfall we would be right where we are today a few years from now. There's nowhere to move," said Carl Boronkay, the district's general manger. He cautioned that still more stringent conservation measures may be needed if the drought persists.

The board approved the plan by a 46-1 vote with four members absent.

The district provides more than half the water supply for Southern California's 15 million people. It gets its water from the State Water Project, the Colorado River and other sources and supplies it to the Los Angeles Department of Water and Power and 26 other utilities.

The new cuts go into effect March 1, and includes penalties to be implemented April 1 for member utilities that exceed their rations. Agencies will have to pay triple the cost of water used in excess of the limits. But they also would get a 50 percent rebate on the amount of water saved.

The lone dissenting vote Tuesday came from Michael A. Nolan of Burbank, who believes that some water agencies stand to make a lot of money from the rationing.