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Land-surface Elevation

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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.
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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.
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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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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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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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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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Land Subsidence in the Santa Clara Valley

Throughout the late 1800s and into the 1920s when two thirds of the Santa Clara Valley had been irrigated, water flowed freely from wells. Water-level declines of more than 200 ft occurred in the Santa Clara Valley from the early 1900's to the mid 1960's (Fowler, 1981). Land subsidence was first detected in 1933 (Poland and Ireland, 1988). As the decades passed, groundwater levels continued to...
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Land Subsidence in the Santa Clara Valley

Throughout the late 1800s and into the 1920s when two thirds of the Santa Clara Valley had been irrigated, water flowed freely from wells. Water-level declines of more than 200 ft occurred in the Santa Clara Valley from the early 1900's to the mid 1960's (Fowler, 1981). Land subsidence was first detected in 1933 (Poland and Ireland, 1988). As the decades passed, groundwater levels continued to...
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Extensometers and Compaction

Extensometers measure the compaction and expansion of the aquifer system, providing depth-specific data that can help CAWSC scientists better understand the rate, extent, and at what depths in the system subsidence is occurring.
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Extensometers and Compaction

Extensometers measure the compaction and expansion of the aquifer system, providing depth-specific data that can help CAWSC scientists better understand the rate, extent, and at what depths in the system subsidence is occurring.
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Land Subsidence Along the California Aqueduct

Subsidence is a global problem and, in the United States, more than 17,000 square miles in 45 States, an area roughly the size of New Hampshire and Vermont combined, have been directly affected by subsidence. More than 80 percent of the identified subsidence in the United States is a consequence of human impact on subsurface water.
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Land Subsidence Along the California Aqueduct

Subsidence is a global problem and, in the United States, more than 17,000 square miles in 45 States, an area roughly the size of New Hampshire and Vermont combined, have been directly affected by subsidence. More than 80 percent of the identified subsidence in the United States is a consequence of human impact on subsurface water.
Learn More

Piezometers and Groundwater Levels

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.
link

Piezometers and Groundwater Levels

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.
Learn More

Land Subsidence in the San Joaquin Valley

The San Joaquin Valley is one of the most productive agricultural regions in the nation. Beginning around the 1920's, farmers relied upon groundwater for water supply. Over time, overpumping caused groundwater-level declines and associated aquifer-system compaction and land subsidence that resulted in permanent aquifer-system storage loss.
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Land Subsidence in the San Joaquin Valley

The San Joaquin Valley is one of the most productive agricultural regions in the nation. Beginning around the 1920's, farmers relied upon groundwater for water supply. Over time, overpumping caused groundwater-level declines and associated aquifer-system compaction and land subsidence that resulted in permanent aquifer-system storage loss.
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