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Stanford Study Measures Solution to California Sinking, Reveals It May Take More to Reverse Central Valley Damage

STANFORD, Calif. (KGO) – Surveying the Central Valley from the air, the landscape seems flat as far as the eye can see. But in a recently published study, Stanford researchers confirmed that not only are sections of the valley sinking, but it may take more to repair the damage than previously thought.

Lead author Matt Lees has followed a long trail dating back decades.

“So we went out there and looked for all the water level measurements we could find. And in the end, we ended up with a continuous record from the 1950s right up to the present day. And we got found more than 20 feet of subsidence occurs due to the lowering of the water level during this period,” says Lees.

Twenty feet over the past decades – the sinking and its connection to the aggressive pumping of California’s groundwater is well documented.

But the Stanford teams say what’s equally problematic is what happens deep underground when water levels drop. This is where they say the layers of sediment are squeezed together, something like a sponge, and may not spring back into shape quickly without being replenished with moisture.

“We found that if you keep the water levels the same, the subsidence will continue for 10, 20, maybe even 30 years or more,” adds Lees.

And some experts believe that once collapsed, underground aquifers could become harder to recharge, or lose a percentage of their natural water-storage capacity. Sinking, or subsidence as it is called, can also damage the massive canals that carry water up and down the state, slowing flow and causing leaks.

The Delta-Mendota Canal, which supplies water to millions of Californians, needs to be repaired.

The study’s lead author, Professor Rosemary Knight, believes a long-term solution to subsidence is achievable, but says it will require more aggressive recharge of groundwater basins

“A lot of the modeling that’s been done in preparation for statewide groundwater sustainability plans assumes that if you stop the drop in the water level, the subsidence is going to stop. But that’s is false, because there is a delay between the drop in the water level and the clay reacting,” she explains.

Stanford models suggest it may be necessary to raise the water table by 30 feet or more. But they say the good news is that if water levels rise due to rain, recharge and tighter pumping controls, the sinking could start to be controlled fairly quickly.

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