Washington—A new report from NASA’s Jet Propulsion Laboratory indicates that large areas of the Central Valley have subsided close to two feet in the last 18 months. According to the report, land subsidence—when the land actually sinks— is a result of too much groundwater being drawn from underground aquifers, a process that has been exacerbated by the drought.
Key passages from the report:
- Page 3: The effects of subsidence on infrastructure are varied: Roads can be broken by fissures, pipelines have exhumed, and the change in slope of the land can alter drainage patterns.
- Page 11: The highest amounts of subsidence occur at the previously identified localized subsidence bowl located between Huron and Kettleman City directly north of Avenal Cut-off Rd. and Check 20, referred to as the Avenal hot spot [Figure 8]. 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 near the previous maximum subsidence direct 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.
Senator Dianne Feinstein (D-Calif.) released the following statement in response to the report:
“This report from the Jet Propulsion Laboratory documents an alarming trend of land subsidence throughout the Central Valley. 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 more than 50 miles in some regions of the valley.
“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. 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.
“For example, the California Aqueduct dropped more than two feet in the last 18 months. This major aqueduct carries water to 25 million people and a million acres of farmland. As a result of the damage, the aqueduct now carries 20 percent less water than when it was first built.
“I’ve asked for a briefing from the authors at Jet Propulsion Laboratory, and I look forward to working with the state to repair this damage and find ways to prevent it in the future.”