SAN FRANCISCO (KCBS)  -- The millions of homes and businesses in San Francisco and three other counties that depend on Hetch Hetchy will have to use less water, or the water system will not be able to meet the Bay Area’s future needs.

The utility that now supplies about 265 million gallons a day will only be able to meet customers’ growing needs through conservation, according to an eight-volume environmental impact report on the Hetch Hetchy rebuild released Tuesday.

  KCBS' Barbara Taylor reports

Demand is expected to increase another 35 million gallons a day over the next decade, but PUC General Manager Ed Harrington said no mandatory rationing is planned over the long-term.

Environmentalists worry expanding the capacity of the water system along with the seismic retrofit could ultimately drain too much of the watershed in the high Sierra. The water system crosses five active faults.

The 2.5 million homes and businesses served by Hetch Hetchy now are already being asked to cut back ten percent.

Demand is expected to reach 300 million gallons a day by 2018.

(jro)