The Central California town that keeps sinking
The very ground upon which Corcoran was built is steadily collapsing, a situation caused primarily by agriculture.
In California’s San Joaquin Valley, the farming town of Corcoran has a multimillion-dollar problem. It is almost impossible to see, yet so vast it takes NASA scientists using satellite technology to fully grasp.
Corcoran is sinking.
Over the past 14 years, the town has sunk as much as 11.5 feet in some places — enough to swallow the entire first floor of a two-story house and at times making Corcoran one of the fastest-sinking areas in the country, according to experts with the United States Geological Survey.
Subsidence is the technical term for the phenomenon — the slow-motion deflation of land that occurs when large amounts of water are withdrawn from deep underground, causing underlying sediments to fall in on themselves.
Each year, Corcoran’s entire 7.47 square miles and its 21,960 residents sink just a little bit, as the soil dips anywhere from a few inches to nearly two feet. No homes, buildings or roads crumble. Subsidence is not so dramatic, but its impact on the town’s topography and residents’ pocketbooks has been significant. And while the most recent satellite data showed that Corcoran has sunk only about four feet in some areas since 2015, a water management agency estimates the city will sink another six to 11 feet over the next 19 years.
Already, the casings of drinking-water wells have been crushed. Flood zones have shifted. The town levee had to be rebuilt at a cost of $10 million — residents’ property tax bills increased roughly $200 a year for three years, a steep price in a place where the median income is $40,000.
The main reason Corcoran has been subsiding is not nature. It’s agriculture.
In Corcoran and other parts of the San Joaquin Valley, the land has gradually but steadily dropped primarily because agricultural companies have for decades pumped underground water to irrigate their crops, according to the USGS California Water Science Center.
When farmers fail to get enough surface water from local rivers or from canals that bring Northern California river water into the San Joaquin Valley, they turn to what is known as groundwater — the water beneath the Earth’s surface that must be pumped out. They have done so for generations.
Corcoran’s situation is not unique. In Texas, the Houston-Galveston area has been sinking since the 1800s. Parts of Arizona, Louisiana and New Jersey have dealt with subsidence problems. The foundations of Mexico City churches have famously tilted, and one 2012 study found that Venice was subsiding at a rate of .07 inches per year.
But how Corcoran came to dip nearly 12 feet in more than a decade is a tale not of land but of water, and the ways in which, in ag-dominated Central California, water is power — so much so that many residents and local leaders downplay the town’s sinkage or ignore it entirely. Few in Corcoran are eager to criticize agricultural companies that provide jobs in a struggling region for helping to cause a little-known geological problem no one can see.
“It’s a risk for us,” said Mary Gonzales-Gomez, a lifelong Corcoran resident and chairwoman of the Kings County Board of Education. “We all know that, but what are we going to do? There’s really nothing that we can do. And I don’t want to move.”
Read more: https://www.hcn.org/articles/south-water-the-central-california-town-that-keeps-sinking
