A town in central California is sinking and it’s not because it’s been flooded by water. No, the ground itself is sinking. The difference is so subtle and covers such a vast area that it can’t be seen with the naked eye. It took a careful look at satellite data to figure out that Corcoran has sunk as much as 11.5 feet in many areas over the past 14 years. The reason why is pretty interesting.
Corcoran is basically a farming town almost exactly between Los Angeles and San Francisco. Being a farming town means that it requires a lot of water for all the crops, so when rivers and rain don’t provide enough, residents tend to turn towards underground reservoirs of water. The New York Times did an extensive report on the situation.
When large amounts of underground water reservoirs are pumped, it creates an empty spot that causes the sediment and soil above to cave in on itself. This process is termed subsidence, which the slow deflation of land from heavy use of water deep underground. The process takes years to notice but in Corcoran, the first floors of two-story buildings have sunk.
No one would have noticed the scale at which it was happening if NASA scientists didn’t take a close look via satellites. The area where the land is sinking is now called the Corcoran Bowl. The area stretches up to 60 miles with Corcoran at the center of it all. Jay Famiglietti, former NASA scientist and now the director of the Global Institute for Water Security at the University of Saskatchewan in Canada was the one who first discovered the Corcoran Bowl.
Jay warned the residents about the sinking as early as 2009 but I guess people didn’t take it seriously. According to him, “There’s no way around it. The scale of the bowl that’s been created from the pumping is large and that may be why people don’t perceive it. But a careful analysis would find there are lots of infrastructures potentially at risk”.
The general manager of the Corcoran Irrigation District, Gene Kilgore, said that “We’re all pumping. Every grower is pumping, every city is pumping, and we all play whatever part there is to subsidence”. The only way to reduce further damage is to reduce pumping and impose better control over groundwater usage. Else a water management agency estimates that the town will sink another six to 11 feet over the next 19 years.
According to Karla Nemeth, director of the California Department of Water Resources, “The plight of Corcoran is the absolute poster child for legacy unmanaged groundwater pumping that is unacceptable in California”.