“Ground water pumping has increased greatly, water levels are dropping because of the increased pumping and therefore subsidence increases,” Jeanine Jones, the Department of Water Resource’s drought manager, told FOX 40 in Sacramento.
The sinking of ground due to ground water pumping has been observed for 80 years in the Central Valley, but the new measurements show that the rate of sinking has increased as growers turn to ground water to grow crops. Surface water deliveries have been reduced or cutoff because of the drought.
The survey, which used NASA satellite and aircraft radar imaging to measure ground levels, dramatically documents the rising toll the prolonged drought is taking on the Central Valley.
Two areas, one just north and and one just south of Fresno, are affected most. Land there has sunk over a foot in just eight months. There is more rapid subsidence just north of Sacramento as well. Near the community of Yolo, the ground has subsided as much as five inches in a year.
Groundwater levels have dropped to new lows in some parts of the San Joaquin Valley as agriculture has turned in a big way to wells to make up for drought-related cuts in irrigation deliveries. “We're pumping at record levels,” Mark Cowin, director of the state Department of Water Resources, told the Los Angeles Times.
The ground movement threatens the California Aqueduct that transports water to Southern California as well as roads, bridges and wells.
Water officials say, in most cases, the effects are not reversible even if the drought ends.