Land Subsidence in California


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Map of land subsidence in the San Joaquin Valley form 1926-1970, shaded by amount of subsidence in meters
December 31, 2013

Land subsidence in the San Joaquin Valley, California, 1926–70

The extensive withdrawal of groundwater from the unconsolidated deposits of the San Joaquin Valley has caused widespread land subsidence—locally exceeding 8.5 meters (m) between 1926 and 1970 (Poland and others, 1975; fig. 2), and reaching 9 m by 1981 (Ireland, 1986). Long-term groundwater-level declines can result in a vast one-time release of “water of compaction” from

map of the central valley with the CVHM grid cells overlaid, and a cross section of the subsurface
December 31, 2009

Central Valley Hydrologic Model (CVHM)

The Central Valley Hydrologic Model (CVHM) is built on knowledge from USGS and other Federal, State, and local studies. The CVHM was constrained by comparing simulated and historically observed groundwater levels, streamflows, and subsidence. The detail and breadth of this hydrologic modeling tool provides a better understanding of valleywide hydrologic processes. This

long fissure in the dry Mojave Desert with the mountains in the background
December 31, 2005

Fissure in the Mojave Desert

Fissure near Lucerne Lake along State Route 247 (visible in background), Mojave Desert, California. The localized subsidence in five areas near dry lake beds was caused by declining water levels in fine-grained (clay and silt) sediments. In the Mojave River and Morongo Groundwater Basins (fig. 2), the combination of variable climatic conditions, tectonic activity, and

Map of land subsidence in the Sacramento-San Joaquin Delta, shaded by feet below sea level
December 31, 2005

Sacramento-San Joaquin Delta Land Subsidence

A map of subsidence in the Delta based on the leveling and observations of transmission-line foundations, circa 1930s-1990s. The subsidence increases stresses on the levee system, and failure of levees would cause salt water to move further up the Delta system by disrupting favorable gradients. This would degrade the quality of water that is the heart of water supply

Illustration of the aquifer compaction process.
December 31, 1999

Aquifer Compaction

Fine-grained sediments (clays and silts) within an aquifer system are the main culprits in land subsidence due to groundwater pumping. Fine-grained sediments are special because they are composed of platy grains. When fine-grained sediments are originally deposited, they tend to be deposited in random orientations. These randomly oriented sediment grains have a lot of room


Modeling Land Subsidence Processes

Diagram showing the relation between surface and subsurface processes before and after land subsidence. The linkages to subsidence deformation are briefly summarized for surface-water, landscape and groundwater flow processes. The potential changes in movement of water before and after the linked effects of subsidence result in redirected or reduced runoff, reduced