STANFORD, Calif. (KGO) -- Surveying the Central Valley from the air, the landscape looks level about as far as the eye can see. But in a newly released study, researchers from Stanford have confirmed that not only are sections of the Valley sinking, but it may take more to reverse the damage than previously believed.
Lead author Matt Lees followed a long trail winding back decades.
"So we went out there, and we looked for every water level measurement we could find. And in the end, what we ended up with is a continuous record from 1950s, right through til present day. And we found over 20 feet of subsidence happens due to the water level declines over that period," says Lees.
Twenty feet over recent decades -- the sinking and its link to aggressive pumping of California's groundwater is well documented.
But the Stanford teams says what's just as problematic is what's happening deep underground as the water levels drop. That's where they say layers of sediment are being squeezed, something like a sponge, and may not pop back into shape quickly without being recharged with moisture.
"We found that if you keep the water levels at the same level, the subsidence will continue for 10, 20, maybe even 30 or more years," Lees adds.
And some experts believe that once collapsed, the underground aquifers could become more difficult to re-charge, or lose a percentage of their natural water storage capacity. Sinking, or subsidence as it's known, can also damage the massive canals that carry water up and down the state, slowing the flow and causing leaks.
The Delta-Mendota canal, which supplies water to millions of Californians, is slated for repairs.
Lead study author, professor Rosemary Knight, believes a long-term solution to subsidence is achievable, but says it will require more aggressive recharging of the groundwater basins
"Much of the modeling that's been done in preparation of groundwater sustainability plans throughout the state assumes that if you stop the water level going down, the subsidence is going to stop. But that's wrong, because there's a delay between the water level going down and the clay's responding," she explains.
Stanford models suggest it may require raising the water table 30 feet or more. But they say the good news is that if water levels do rise from rain, recharge and tighter controls on pumping, the sinking could begin to be controlled relatively quickly.