NASA report finds Central Valley is sinking due to drought

A new report out of NASA shows land in the San Joaquin Valley is sinking faster than ever before.

The report, released Wednesday by the Department of Water Resources, found the region is sinking by nearly two inches per month in some locations. 

"Because of increased pumping, groundwater levels are reaching record lows—up to 100 feet lower than previous records," Department Director Mark Cowin said. "As extensive groundwater pumping continues, the land is sinking more rapidly and this puts nearby infrastructure at greater risk of costly damage."  

Gov. Jerry Brown's Drought Task Force has already committed to working with communities affected by the land sink by developing recommendations to reduce the rate of sinking and address risks to infrastructure. 

The DWR will also launch a $10 million program to help communities with stressed groundwater basins, or strengthen local ordinances and conservation plans. The funding comes from the statewide Water Bond approved last year by voters. In the coming days the department said it will post more information on how that funding will be applied. 

For decades California has experienced land sink, known as subsidence, because of excessive ground water pumping during drought conditions. 

But the new NASA report shows the sinking is happening at a faster rate and the risk of damage on surface infrastructure is growing. The data in NASA's report was obtained by comparing satellite images of the Earth's surface over time. 

In eight months, the land near Corcoran in the Tulare basin sank 13 inches, or about 1.6 inches per month. An area in the Sacramento Valley was sinking at half-an-inch per month, which is faster than previous measurements.

Already, the long-term land sink has destroyed thousands of public and private groundwater casings in the San Joaquin Valley. And over time, it could permanently reduce the storage capacity of underground aquifers.

"Groundwater acts as a savings account to provide supplies during drought, but the NASA report shows the consequences of excessive withdrawals as we head into the fifth year of historic drought," Director Cowin said. "We will work together with counties, local water districts, and affected communities to identify ways to slow the rate of subsidence and protect vital infrastructure such as canals, pumping stations, bridges, and wells."

NASA said it will continue to monitor the Central Valley land sink with data from the European Space Agency's recently launched Sentinel-1 mission. That data will also cover a broader area and identify more vulnerable locations. 





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