LOS ANGELES, FEB. 14 -- California's drought-stricken farmers received another heavy blow today when the Bureau of Reclamation announced that federal water supplies to them would be reduced by 75 percent.

The announcement in Sacramento confirmed a warning of likely reductions issued last week in an interview by Dennis Underwood, commissioner of the federal bureau.

The cuts are the most severe ever ordered by federal authorities in California and come less than two weeks after farmers who receive water from the State Water Project were told that they will receive no deliveries this year.

California, now late in what promises to be its driest winter in history, is in the midst of a fifth year of drought. Gov. Pete Wilson (R) is scheduled to make an announcement Friday on recommendations from an emergency drought-action team.

Most California cities have adopted mandatory water rationing. But the impact has been greatest on farms, which use four-fifths of the state's water supplies and support a $17 billion agriculture industry.

Today's action, announced by the bureau's regional director Don Paff, means that about 22,000 farmers who receive water from the Central Valley Project (CVP) must find alternative sources of water.

Mike Henry, a spokesman for the California Farm Bureau Federation, said most farmers who normally depend on CVP can survive this year by using ground water and tapping local supplies. But he said farm acreage could be reduced substantially.

As an example, more than 1 million acres planted in cotton last year are expected to be reduced at least to 700,000 acres this year, with further cuts likely. Cotton-planting season begins next month.

Reduced plantings of vegetables, wheat and various grain crops are anticipated, Henry said.

But farmers dependent on CVP water are more fortunate than farmers who are in Kern County in the lower end of the San Joaquin Valley and depend totally on state water supplies for their crops. About 300,000 acres previously devoted to crops may not be planted this year in Kern County, according to early estimates.

The bureau's plan to reduce CVP water by 75 percent contains provisions to allow extra supplies in hardship cases. Priority is to be given to cases where water is needed to preserve fruit trees and vineyards.

The bureau will reduce water by only 50 percent to the scattered small municipalities and districts that depend on federal water for residential use.

But the overall picture is nonetheless becoming bleaker each day.

"It's going to be a very tough year," Paff said in making the announcement.