California scientists say water stored naturally underground in the Central Valley is disappearing at a rapid rate. The likely cause is irrigation.
UC Irvine and NASA scientists monitor tiny month-to-month differences in Earth's gravity field for the Gravity Recovery and Climate Experiment. That gravity field changes, in part, because of where water is and where it moves over the planet.
Figuring out where water weighs more and less over the Earth can tell scientists about climate change's general effects on the water cycle. In California’s Central Valley, they've documented a regionally specific phenomenon.
The scientists are examining aquifers – spaces between rock and sediment underground where water percolates. In the last six years, Central Valley aquifers have lost enough water to fill the equivalent of Lake Mead.
In that part of the state, farming relies on diverted surface water and water pumped from below the surface for irrigation. As surface water has become scarcer, the Central Valley has drunk more deeply from these underground banks.
With water underground under light regulation, and with ongoing climate changes, Irvine scientists point out that the Central Valley will be thirsty for a while.