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The upper reaches of EBMUD's San Pablo Reservoir show low water levels in Orinda, Calif. on Thursday, Feb. 6, 2014. Despite the low water levels, the reservoir opens to the public on Friday, Feb. 7. (Kristopher Skinner/Bay Area News Group)

The board voted 7-0 Tuesday to join the growing number of Bay Area water districts seeking voluntary cuts during a third consecutive dry rain season. Storms of the past few days have produced more water but still left the district worried of the potential for below average runoff into its Mokelumne River water supplies piped in from the Central Sierra foothills.

"The last 12 days have been an improvement, but they don't make up for the seven previous months that were extremely dry," said Eileen White, EBMUD's manager of water operations. With 40 percent of the rain season left, the district would need five more good storms to assure normal water storage levels in reservoirs this September, she said.

The 10 percent conservation goal is a first step this year and can be changed to seek greater savings later this year if the water outlook worsens, said Alexander Coat, the district general manger.

If the shortages are so severe as to warrant rationing, the water board promised it wouldn't base allocations on individual customers' past use -- a practice that could be unfair to households that already have cut back in the last year.

Some customers who practice conservation have said they do not want to be hurt by rationing that penalizes people for saving in past years, water board members said.

District officials said it will take until late March or early April for the district to know enough to make final decisions on its drought response this year.

If its shortages are severe enough EBMUD can for the first time pump Sacramento River water to the East Bay through a $900 million project finished in 2010, said John Coleman, a water board member.

Water district managers said they continue to take preliminary steps toward preparing for possible use of that emergency supply.

EBMUD currently has 483,000 acre feet of water stored in all its reservoirs. That is 63 percent of capacity and 85 percent of normal.

The district joins the Santa Clara Valley Water District and the San Francisco Public Utilities Commission in seeking a voluntary 10 percent savings. Alameda County Zone 7 Water Agency and the Alameda County Water District have sought 20 percent cuts. The Marin Municipal Water District has asked for a 25 percent cut.

The Contra Costa Water District is asking customers to conserve but not toward a specific reduction. The district relies on federal water from the Sacramento-San Joaquin River Delta.

Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff.