2008-2010 Land Subsidence Contours, San Joaquin Valley, California

Land subsidence contours showing vertical changes in land surface in the central San Joaquin Valley area, California, during January 8, 2008-January 13, 2010. The top graph illustrates elevation changes computed from repeat geodetic surveys along Highway 152 for 1972-2004. The bottom graph depicts elevation changes computed from repeat geodetic surveys along the Delta-Mendota Canal for 1935-2001. Subsidence data along Highway 152 were computed from published National Geodetic Survey elevations. Subsidence graph for the Delta-Mendota Canal was obtained from the San Luis and Delta-Mendota Water Authority and the Central California Irrigation District