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Science & Environment

Drilling Deeper Wells Contributes To California's Subsidence Problem


Central California is sinking. A new reports shows some parts of the drought-stricken state are dropping almost 2 inches per month as farmers keep drilling deeper to find groundwater for their crops. Here's NPR's Nathan Rott.

NATHAN ROTT, BYLINE: Subsidence is the scientific term for what's happening in California's Central Valley. It's what happens when groundwater is pumped from deep below ground and brought to the surface, causing the layers below to settle and sink, collapsing like a dried sponge. It's happening across wide swaths of the Central Valley, as farmers pump from wells like this one at a vineyard in the southern end of the valley, slurping water from deeper and deeper to make up for the water they're not getting from above because of the drought. Subsidence is nothing new in California. But satellite measuring by NASA shows that it's happening faster than ever before, particularly in two large areas. Jeanine Jones is with California's Department of Water Resources, which commissioned NASA's report.

JEANINE JONES: In the southern part of the valley, looking with two different satellites, they identified a maximum subsidence area of about 3 feet.

ROTT: Land near Corcoran, about an hour south of Fresno, was sinking about 1.6 inches per month. But perhaps most troubling was that land near some parts of the California Aqueduct, which moves water for the northern end of the state to the south, has sunk more than a foot. Mark Cowin is the director of the Department of Water Resources.

MARK COWIN: The sinking of the surfaces can result in significant damage to infrastructure like canals, aqueducts and bridges.

ROTT: Cowin wouldn't say how much damage has already occurred in the state, but his office pointed to a $2.5 million bridge repair job in Mendota County as an example of what subsidence can do. Because of that, many in the state are calling for limits on groundwater pumping, citing that in places, groundwater levels are already 100 feet lower than previous records. The state did approve legislation to do just that last year, requiring local governments to regulate previously unchecked groundwater pumping. But most of those regulations and requirements won't go into effect until 2020. Nathan Rott, NPR News. Transcript provided by NPR, Copyright NPR.