Groundwater basins in California are used as local reservoirs to supplement water supplies. Water managers need information on the relationship between water extraction and land subsidence. Two studies are being conducted in the San Joaquin Valley to provide important information to manage and minimize the impacts of land subsidence to water-conveyance infrastructure, including the California Aqueduct. The studies use conventional and persistent scatter InSAR remote sensing data and GPS data to measure land surface elevation changes between 2003 and 2010, and compare those data to information on groundwater levels. A large area of subsidence was detected that includes parts of the Delta-Mendota Canal, the San Joaquin River, and the Eastside Bypass where maximum subsidence rates approach about 300 millimeters per year (1 ft) during 2008-2010.