By Sharon Bernstein

SACRAMENTO, Calif. (Reuters) - California water regulators on Tuesday adopted the state's first rules for mandatory cutbacks in urban water use as the region's catastrophic drought enters its fourth year.
             
The emergency regulations, which require some communities to trim water use by as much as 36 percent, were approved unanimously late Tuesday by the State Water Resources Control Board weeks after Democratic Governor Jerry Brown stood in a drying mountain meadow and ordered statewide rationing.
             
"This is a community crisis," said water resources board chair Felicia Marcus as testimony began in a daylong hearing on the rules on Tuesday. "We want to get this as right as we can."
             
The rules approved Tuesday, which will be reviewed by state legal advisers before going into effect, require cutbacks of 4 percent to 36 percent in water use, with communities that use the most water being asked to enact the deepest cuts.
             
Urban users will be hardest hit, even though they account for only 20 percent of state water consumption, while the state's massive agricultural sector, which the Public Policy Institute of California says uses 80 percent of human-related consumption, has been exempted.
             
Brown, a Democrat, has defended the agricultural exemptions, saying that the state's farmers have already had to make do with less water as the state restricted supplies for irrigation amid environmental concerns in the drought.
             
One of the main aims of the rules will be to cut back water used for ornamental lawns and other outdoor landscaping.
             
San Francisco is required to cut its water use by 8 percent, Los Angeles by 16 percent, San Jose 20 percent and Sacramento 28 percent.
             
At the high end, the cities of Bakersfield and Modesto in the state's San Joaquin Valley breadbasket and the affluent Southern California city of Beverly Hills will have to conserve by 36 percent.
             
At Tuesday's hearing, numerous water districts complained that the regulations were unfair, penalizing residents for water use needed in their communities by agricultural and industrial users.
             
Others said that their residents had paid extra for years to store water for use during dry years, only now to be told that they can't use it.
             
The regulations also require water suppliers to report regularly to the state on their progress. Even the smallest districts would have to collect usage data and limit watering to two days per week.
              
(Reporting by Sharon Bernstein; Editing by Simon Cameron-Moore)