BAKERSFIELD -- A federal study says the San Joaquin Valley has lost millions of acre-feet of water since the early 1960's.

The U.S. Geological Survey's study says about 60 million acre-feet of water have been pumped from the Valley's underground aquifer without being replenished. That's about 19.6 trillion gallons, enough water to service every home in the state for ten years, according to the study.

The current drought as well as the ongoing legal battle over the Delta smelt in the Sacramento river delta have reduced water shipments, forcing local groups to pump more groundwater.

"Our groundwater users are pumping a tremendous amount of water to meet demands in Kern County, and that's been an historic pattern especially the past few years," said Jim Beck, general manager of the Kern County Water Agency.

But the groundwater pumping is renewing concerns that the Valley is sinking, as much as 30 feet in some places. Officials fear that subsidence could severely damage California's vital infrastructure, including the California aqueduct. Fixing it doesn't come cheap, as the estimated repair costs are at least $1 million a mile.

"We monitor the subsidence very closely and the Department of Water Resources has plans to implement repair strategies should they become necessary," Beck said. "The best thing to do of course is to avoid that altogether, and that could be done by reducing the need for areas to pump groundwater."

Water experts say the study highlights the need for a better solution to deliver water to Kern County.

"We're at a crisis point," Beck said. "People have lost their jobs, we're seeing tremendous economic impacts throughout the Valley, and unfortunately at this point we don't have a clear solution in place."

The aqueduct delivers water to 20 million Californians. Several groups that use the aqueduct to deliver water to those residents recently signed an agreement with the USGS to see how much subsidence has occurred along the aqueduct on a 70-mile stretch from Merced to Kings counties.