Subsidence Monitoring

Reclamation surveys a network of over 70 control points across the San Joaquin Valley in July and December of each year to monitor ongoing subsidence. Following are the bi-annual survey result tables, maps, and ArcGIS shapefiles. Section 8 of the original control network report, below, includes a description of the control points, locations, and photos. All elevations are in GEOID 03, NAVD 88, and the horizontal datum is NAD 1983, California Coordinate System of 1983, Zone 4, US survey feet. Free or minimally constrained adjustment elevations should be used as they better represent control point movement by removing adjustment distortion.

The California Department of Water Resources has also performed subsidence monitoring along the Lower San Joaquin Flood Control Project levees. This work was combined with Reclamation’s survey network into a subsidence monitoring methodology and status technical memorandum in 2014.

The United States Geologic Survey has done monitoring with InSAR and several extensometers.