PETALUMA, Dec. 13, 2007 ? Prolonged water shortages in Marin and Sonoma counties could parch profits in key industries and result in thousands to tens of thousands of job cuts, according to a Sonoma State University economic-impact report presented this morning.

If the supply of water were to fall 10 percent short of demand, it would close the spigot on $199 million domestic product in the two counties and lead to 1,580 lost jobs, according to a report by Robert Eyler, Ph.D., director of the university's Center for Regional Economic Analysis. A 20 percent water deficit would double those figures, and a 30 percent shortfall would lead to exponential economic effects that would result in 33,500 layoffs ? or about 9 percent of jobs ? and $4.36 billion in lost revenue.

"These estimated impacts are annual, for every year of the water shortage," Dr. Eyler wrote. "The full effects may take years to be completely realized."

By comparison, the Sonoma County Water Agency, which serves a half-million customers in Sonoma and northern Marin counties and was a co-sponsor of the report, called for the cities and towns it supplies to cut consumption by 15 percent from June to October because a drier-than-average winter didn't leave enough water in the Russian River Basin for protected fish.

Such regulatory droughts are what water suppliers fear most. Business practices and municipal water-reuse programs otherwise could help water providers meet demand through 2030, Dr. Eyler wrote based on interviews. The water agency has been petitioning the state for more water to be released from Lake Sonoma and also is working on a water-supply system that prepares for endangered fish-related water supply curtailment.

Dr. Eyler presented the 31-page study at the Economic Insight conference put on by study co-sponsor North Bay Leadership Council in Petaluma.

Businesses most affected directly and indirectly by greater conservation efforts and higher water costs and would be wineries, winegrape growers, restaurants, homebuilders, real estate, medical offices and hospitals, grocery stores, banks and automobile repair shops, according to the study.