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Measuring Land Subsidence in California

Collecting Data Above and Below Ground

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Delta-Mendota Canal

Evaluation of Groundwater Conditions and Land Subsidence

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Land Subsidence in California

Land subsidence is a gradual settling or sudden sinking of the Earth's surface due to subsurface movement of earth materials. The main cause of subsidence in California is groundwater pumping. The effects of subsidence include damage to buildings and infrastructure, increased flood risk in low-lying areas, and lasting damage to groundwater aquifers and aquatic ecosystems.

Areas of Subsidence

Map of California with areas of subsidence shaded by cause

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

Explore Subsidence

Drought Indicators

Screenshot of the interactive Central Valley drought indicators map

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

Explore Drought Data

Measuring Land Subsidence

A geodetic bench mark from the Central Valley in California

Land-surface elevations, and elevation changes, are measured with a variety of land- and space-based scientific techniques.

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Science

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continuous GPS mounted on a tripod, located in a field, with a solar panel in the background

Continuous Global Positioning System (CGPS) Stations

Measurements of elevations, aquifer-system compaction, and water levels are used to improve our understanding of the processes responsible for land-surface elevation changes. Elevation or elevation-change measurements are fundamental to monitoring land subsidence, and have been measured by using continuous GPS (CGPS) measurements and campaign global positioning system (GPS) surveying.
By
California Water Science Center, Land Subsidence in California
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Continuous Global Positioning System (CGPS) Stations

Measurements of elevations, aquifer-system compaction, and water levels are used to improve our understanding of the processes responsible for land-surface elevation changes. Elevation or elevation-change measurements are fundamental to monitoring land subsidence, and have been measured by using continuous GPS (CGPS) measurements and campaign global positioning system (GPS) surveying.
Learn More
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Black & white photo of two USGS scientists conducting spirit leveling in the field

Spirit Leveling

Elevation or elevation-change measurements are fundamental to monitoring land subsidence, and have been measured by using interferometric synthetic aperture radar (InSAR), continuous GPS (CGPS) measurements, campaign global positioning system (GPS) surveying, and spirit-leveling surveying. The most precise measurements tend to be made using spirit-leveling surveys and extensometers. Spirit...
By
California Water Science Center, Land Subsidence in California
link

Spirit Leveling

Elevation or elevation-change measurements are fundamental to monitoring land subsidence, and have been measured by using interferometric synthetic aperture radar (InSAR), continuous GPS (CGPS) measurements, campaign global positioning system (GPS) surveying, and spirit-leveling surveying. The most precise measurements tend to be made using spirit-leveling surveys and extensometers. Spirit...
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Illustration of a subsidence cone with an interferogram underneath it.

Interferometric Synthetic Aperture Radar (InSAR)

Interferometric Synthetic Aperture Radar (InSAR) is an effective way to measure changes in land surface altitude. InSAR makes high-density measurements over large areas by using radar signals from Earth-orbiting satellites to measure changes in land-surface altitude at high degrees of measurement resolution and spatial detail (Galloway and others, 2000).Synthetic Aperture Radar (SAR) imagery is...
By
California Water Science Center, Land Subsidence in California
link

Interferometric Synthetic Aperture Radar (InSAR)

Interferometric Synthetic Aperture Radar (InSAR) is an effective way to measure changes in land surface altitude. InSAR makes high-density measurements over large areas by using radar signals from Earth-orbiting satellites to measure changes in land-surface altitude at high degrees of measurement resolution and spatial detail (Galloway and others, 2000).Synthetic Aperture Radar (SAR) imagery is...
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