Vast areas of California’s Central Valley are sinking faster than ever before. NASA experts believe that the massive amounts of groundwater being pumped during the state’s historic drought is to blame.
A new analysis shows that in some places the rate of sinking is close to two inches per month, which is putting infrastructure on the surface at growing risk of damage. Sinking land, also known as subsidence, has occurred for decades in California because of excessive groundwater pumping during drought conditions, but the new data shows that it is happening faster than before.
Every six weeks, Michelle Sneed visits a white shed, checking the pulley system and recording a measurement. The numbers show that the ground beneath her feet is sinking. “We’re measuring the highest rates we’ve ever measured here, among the highest rates ever measured in the entire world,” said Sneed, a hydrologist at the U.S. Geological Survey. Sneed said parts of California’s Central Valley are dropping by one foot each year. Some areas are ten feet lower than they used to be.
Mark Cowin, head of the California Department of Water Resources, which released the report, said costly damage has occurred to major canals that deliver water up and down the state, while wells are also being depleted. “Because of increased pumping, groundwater levels are reaching record lows – up to 100 feet lower than previous records,” he added.
NASA scientists used satellite images of the Earth taken over time to measure the sinking land.
Long-term subsidence has already destroyed thousands of public and private groundwater well casings in the San Joaquin Valley.
Over time, subsidence can permanently reduce the underground aquifer’s water storage capacity.
“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,” Cowin said.
So, what happens when the water is simply gone?