Interferometric Synthetic Aperture Radar-Derived Subsidence Contours for the West-Central San Joaquin Valley, California, 2008-10

Extensive groundwater withdrawal from the unconsolidated deposits in the San Joaquin Valley caused widespread aquifer-system compaction and resultant land subsidence from 1926 to 1970?locally exceeding 8.5 meters. The importation of surface water beginning in the early 1950s through the Delta-Mendota Canal and in the early 1970s through the California Aqueduct resulted in decreased groundwater pumping, recovery of water levels, and a reduced rate of compaction in some areas of the San Joaquin Valley. However, drought conditions during 1976?77, 1987?92, and drought conditions and operational reductions in surface-water deliveries during 2007?10 decreased surface-water availability, causing pumping to increase, water levels to decline, [...]