Los Vaqueros Reservoir in Brentwood would be tripled in size to provide Californians with more insurance against water shortages and drought, under a federal bill introduced Thursday.

Reps. George Miller, D-Martinez, and Jim Costa, D-Fresno, sponsored the bill for the expansion of the reservoir that the Contra Costa Water District just expanded in 2012 to meet local water quality and supply needs.

Enlarging the reservoir south of Brentwood again could provide water for other Bay Area water districts, federal wildlife refuges, farmers and perhaps others, Miller and Costa said in a joint statement.

"The devastating impacts of this drought throughout California highlight the critical need to increase water storage across the state," the representatives said.

The release did not have any cost information.

The bill calls for a phased approach toward expansion with the help of the federal Bureau of Reclamation.

Under the first step, other water districts would lease extra space in the existing 160,000-acre-foot reservoir to store surplus water.

The reservoir later would be enlarged to up to 500,000 acre feet after enough water districts or agencies agreed to become partners in the expansion and share in the costs.

Contra Costa district has supported talks and studies on options for expanding Los Vaqueros Reservoir to help meet water needs in California, said district spokeswoman Jennifer Allen.

"The bill is consistent with what we've been working on with other state, local and federal agencies," Allen said. "We're working toward regional cooperation in water planning."

The big challenge is finding partners willing to pay for an expansion. Before the district built Los Vaqueros Reservoir in 1997, it tried to find partners, but no one else opted to buy into the project.

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