Vast areas of California's Central Valley are sinking faster than in the past as massive amounts of groundwater are pumped during the historic drought, state officials say, citing new research by NASA scientists. The data shows the ground is sinking nearly 2 inches each month in some places, putting roads, bridges, and vital canals that deliver water throughout the state at growing risk of damage. Sinking land has occurred for decades in California—and in cities like Phoenix—because of excessive groundwater pumping during dry years, but the new data shows it's happening faster as the state endures its fourth year of drought.
The NASA data shows land near the city of Corcoran sank 13 inches in eight months, and part of the California Aqueduct dropped 8 inches in four months last year. The aqueduct spans hundreds of miles and provides water to millions of people and vast areas of farmland. "We are pumping at historic levels," says Mark Cowin, the head of the California Department of Water Resources. He adds that groundwater levels are dropping to record levels—up to 100 feet lower than previously recorded. Gov. Jerry Brown signed historic legislation last year that requires monitoring of groundwater pumping, but local officials have until 2020 to write their management plans, so it could take another decade or two before California has a handle on groundwater use, Cowin says.