Agricultural profits are not the only things sinking in the Central Valley. The ground is sinking—in some places as much as two feet per year—because during the drought thirsty residents and desperate farmers have extracted too much ground water from the aquifer beneath the terrain in the region. New data from NASA suggests this practice has led to an unexpected dilemma because infrastructure—from roads, train tracks and bridges—is being placed as risk.
“We are pumping at historic levels and parts of the Central Valley may not be able to sustain this practice for much longer,” said Mark Cowin, head of the California Department of Water Resources. “Because of increased pumping, groundwater levels are reaching record lows. As extensive groundwater pumping continues, the land is sinking more rapidly, and this puts nearby infrastructure at greater risk of failure.”
Researchers say the sinking—also known as subsidence—puts vital infrastructure, like canals and channels, at risk. Scientists at the Jet Propulsion Laboratory measured the new rate of sinking by using satellites and airplanes with the latest data revealing that the rate of subsidence is occurring much more quickly each day. Groundwater levels are reportedly at record lows, with measurements of up to 100 feet lower than previously marked. The Central Valley is home to a large portion of the nation’s food crop and it uses about twice much as much water as is naturally being replaced by rain and snow runoff. NASA has discovered that the massive California Acquifer—a portion of which delivers water to southern California—has dropped eight inches since April.
“It is a vivid picture of what subsidence can do,” said Christopher White, manager of the Central California Irrigation District, which during the past few years, has spent millions to raise canal walls and to erect new bridges, because of the damage caused by sinkage. He said the subsidence has already led to closing of thousands of wells in the San Joaquin Valley. Over time, he added, the phenomenon may permanently reduce underground aquifer capacity by squeezing out storage space for water.
The water resources department is launching a $10 million program to assist counties with stressed groundwater basins to develop conservation policies and strategies. Water officials say this is a long-term proposition because, even with a predicted El Nino and a return to regular storm activity, the water capacity within the ancient aquifer under the Central Valley may never return to normal. As bridges and roads steadily sink downward—and millions of dollars are spent on repairs to infrastructure—experts ranging from geologists to hydrologists don’t presently know what will allow the state to escape a vicious cycle of drought, excessive pumping and ongoing subsidence.
“The NASA report underscores the need for more near-term measures to reduce the effects of over-pumping,” Cowin explained. “If our current drought continues or returns in the near future, we don’t believe we can sustain this kind of pumping and the effects that are occurring.”
