Environment & Science

California Central Valley land sinking faster due to drought groundwater pumping, NASA report says

A bridge at the Delta-Mendota Canal, where the land sank enough for the bridge to nearly touch the water.
A bridge at the Delta-Mendota Canal, where the land sank enough for the bridge to nearly touch the water.
NASA

New research by NASA scientists shows vast areas of California's Central Valley are sinking faster than previously thought as massive amounts of groundwater are pumped during the historic drought.

The research released Wednesday says that in some places the ground is sinking nearly two inches a month.

Mark Cowin, head of the California Department of Water Resources, says the sinking land is causing costly damage to major canals that deliver water up and down the state.

"What this NASA report underscores for us is the need for more near-term measures to reduce the effects of over-pumping," Cowin said. "If our current drought continues, we don't believe we can sustain this kind of pumping and the effects that are occurring."

The report says land near the city of Corcoran sank 13 inches in eight months and part of the California Aqueduct has sunk eight inches in four months last year.

The Department of Water Resources preliminarily identified 21 groundwater basins and subbasins that have been significantly overdrafted due to excessive pumping the DWR announced in a statement Wednesday after presenting draft findings at a California Water Commission meeting. See a map of the basins below.

Other effects of the excessive pumping include seawater intrusion and lowered groundwater levels.

Under groundwater management laws enacted in 2014, basins identified as overdrafted by DWR must have groundwater sustainability plans in place less than five years from now.

DWR will hold a public meeting to explain its draft findings and solicit public comment Aug. 25 at the Clovis Veterans Memorial District Auditorium in Clovis, California. 

NASA report