The incredible sinking Valley
February 15, 2017
• New report details extent of problem
• “Land subsidence on such a large scale has taken a toll on California’s infrastructure”
Things are getting a little short in and around Corcoran, in the Central Valley. Perhaps 22 inches shorter.
The land, with Corcoran at the center, has subsided – dropped – by as much as 22 inches in a roughly 60-mile radius, says a new report from NASA’s Jet Propulsion Laboratory.
(Download a copy by clicking on the link at the end of this report.)
Between May 2015 and September 2016, pumping of ground water by farmers caused the land to sink.
A second bowl-shaped area of sinking land is centered on the Merced County hamlet of El Nido and is approximately 25 miles in diameter, encompassing most of the East Side Bypass canal, the JPL report says. From May 2015 to September 2016 the land sank by as much as 16 inches southeast of El Nido.
A third area near Tranquility about 10 miles southeast of Mendota, has intensified and subsided about 20 inches between May 2015 and September 2016, the report says.
In the Sacramento Valley, the cities of Davis and Woodland subsided about two inches from March 2015 to June 2016 and an unusually small intense area of subsidence detected in the previous report near Arbuckle showed a maximum subsidence of about 12 inches.
Sierra Valley, an area north of Lake Tahoe not observed in the data acquired for the earlier report showed subsidence of about 6” in an area coincident with lowered water levels in wells.
But there’s worse. The highest amounts of subsidence occur at a previously identified localized subsidence bowl located between Huron and Kettleman City directly north of Avenal Cut-off Road and referred to as the Avenal hot spot. This feature has deepened to 27.6 inches at its maximum and expanded so that the aqueduct has subsidence as much as 25 inches, with the greatest subsidence west of the hot spot center.
The area of impact from the hot spot has dramatically increased with approximately 4.7 miles of the aqueduct experiencing 10 inches or greater subsidence since measurements started in July 2013 and most of that occurring since summer 2014.
“Subsidence has been a problem for quite some time but the recent drought has made it worse due to excessive groundwater pumping. In the past two years, some areas have experienced drops of more than two feet, spanning over hundreds of miles in some regions of the valley,” says U.S. Sen. Dianne Feinstein, D-California.
“Land subsidence on such a large scale has taken a toll on California’s infrastructure, resulting in billions of dollars in damage to wells, levees, bridges and roads,” she says. “Aqueducts and levees have been particularly hard hit, making it more difficult to move water and endangering vital flood protection efforts—an important consideration given the unprecedented rainfall.”