We have discussed the massive groundwater depletion that has occurred in California here and here as the drought has lingered for the past four years. It should not surprise anyone that one of the very visible impacts of the groundwater pumping is that some areas of the state are, quite literally, sinking. Groundwater takes a long time to replenish, so even if the drought ended yesterday, the sinking would remain. From the AP:
Vast areas of California’s Central Valley are sinking faster than in the past as massive amounts of groundwater are pumped during the historic drought, NASA said in new research released Wednesday.
The research shows that in some places the ground is sinking nearly two inches each month, putting infrastructure on the surface at growing risk of damage.
Sinking land has occurred for decades in California because of excessive groundwater pumping during drought conditions, but the new data shows it is happening faster.
Mark Cowin, head of the California Department of Water Resources, said the costly damage has occurred to major canals that deliver water up and down the state. In addition, wells are being depleted, he said.
“Because of increased pumping, groundwater levels are reaching record lows — up to 100 feet lower than previous records,” Cowin said in a statement.
The report said land near the city of Corcoran sank 13 inches in eight months and part of the California Aqueduct sank eight inches in four months last year.
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.
As part of an ongoing effort to respond to the effects of the drought, a task force is working with communities to develop short-term and long-term recommendations to reduce the rate of sinking and address risks to infrastructure.
“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 in his statement. “
The Department of Water Resources is also launching a $10 million program to help counties with stressed groundwater basins to develop or strengthen local ordinances and conservation plans.
A record low mountain snowpack has increased pumping of groundwater by farmers and other water users. Scientists used satellite images of the Earth taken over time to measure the sinking land.