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USGS - science for a changing world
Collage of land subsidence related images. Dr. Joseph Poland posing with a telephone pole indicating land surface elevation in 1925 compared to 1977.  Buckling in the Delta-Mendota Canal due to land subsidence in the area.  Fissures at the Fort Irwin National Training Center.  Hydrologist Michelle Sneed posing at a location in the Central Valley with signs indicating land surface elevation in 1965 compared to 2013.

From left to right: Dr. Joseph Poland posing with a telephone pole indicating land surface elevation in 1925 compared to 1977; buckling of the Delta-Mendota Canal due to land subsidence in the area; land-subsidence fissure at the Fort Irwin National Training Center; hydrologist Michelle Sneed posing at a location in the Central Valley with signs indicating land surface elevation in 1965 compared to 2013.

Land Subsidence in California

What is land subsidence?

Land subsidence is a gradual settling or sudden sinking of the Earth's surface owing to subsurface movement of earth materials. The principal causes are aquifer-system compaction, drainage and decomposition of organic soils, underground mining, oil and gas extraction, hydrocompaction, natural compaction, sinkholes, and thawing permafrost (National Research Council, 1991).

Why is land subsidence a problem?

Effects of land subsidence include damage to buildings and infrastructure such as roads and canals, increased flood risk in low-lying areas, and lasting damage to groundwater aquifers and aquatic ecosystems.


Screenshot of interactive subsidence map of California

Areas Affected by Subsidence

Explore an interactive USGS map to learn more about areas in California affected by subsidence.


Aerial photo of the Sacramento-San Joaquin Delta

USGS Subsidence Studies

The USGS California Water Science Center uses an integrated set of ground- and space-based measuring techniques and mathematical simulations to study land subsidence. Learn more about these studies and how they are providing information to water managers to help them develop, manage, and protect groundwater resources in a sustainable manner.

Screen shot of the interactive Central Valley drought indicators map

Drought Indicators

Drought indicators in the Central Valley include declining groundwater levels and associated land subsidence as measured and estimated via multiple techniques.

continuous global positioning system used in studying land subsidence

Measuring Subsidence

The USGS California Water Science Center measures land-surface elevations, and elevation changes, with a variety of land- and space-based scientific techniques, the most common being Interferometric Synthetic Aperture Radar (InSAR), continuous GPS (CGPS), and land-surface surveying methods.

A raised well casing in a Central Valley almond orchard as a result of the surrounding land subsiding due to groundwater pumping.

Cause & Effect

Land subsidence in California has two primary causes: aquifer compaction due to excessive groundwater pumping, and decomposition of wetland soils exposed to air after wetland conversion to farmland. Effects include damage to aquifers, ecosystems, and infrastructure.

Image looking into a typical collapsed well screen shows the damage caused by compaction. This photograph was made by lowering a light into the well, followed by a camera; the crumpled vertical ribbing of the steel well screen produced this radiating effect.

Simulating Land Subsidence

The USGS California Water Science Center develops and uses integrated hydrologic models to quantify the spatial and temporal extent of historical subsidence, predict future subsidence under various management scenarios, and help optimize surface water and groundwater use.