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.
An extensometer measures the one-dimensional (1D) change in thickness of a specified depth interval. In other words, it measures the compaction and expansion of the aquifer system to a specific depth. More than two dozen extensometers in the Central Valley were constructed in the 1950s, 1960s, and 1970s by the U.S. Geological Survey in cooperation with the California Department of Water Resources (Ireland and others, 1984), the early group of which represent the first extensometers ever built in the United States. Additionally, several extensometers have been constructed in the San Joaquin Valley more recently. All of the extensometers are constructed as cable or pipe borehole extensometers.
Below are publications relating to the use of extensometers in measuring aquifer compaction in California.
Land subsidence along the California Aqueduct in west-central San Joaquin Valley, California, 2003–10
Water availability and land subsidence in the Central Valley, California, USA
Lithostratigraphic, borehole-geophysical, hydrogeologic, and hydrochemical data from the East Bay Plain, Alameda County, California
Land subsidence in the San Joaquin Valley, California, USA, 2007-14
Land subsidence along the Delta-Mendota Canal in the northern part of the San Joaquin Valley, California, 2003-10
Groundwater availability of the Central Valley Aquifer, California
Land subsidence in the United States
Land subsidence in the United States
Below are news stories associated with this project.
Extensometer Hunters: Searching for Long-Lost Technologies in San Joaquin Valley
San Joaquin Valley: the final frontier. These are the voyages of the U.S. Geological Survey. Its weeklong mission: to explore strange new locations, to seek out abandoned scientific technologies, to boldly go where no scientist has gone before (at least in a few decades).
- Overview
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.
An extensometer measures the one-dimensional (1D) change in thickness of a specified depth interval. In other words, it measures the compaction and expansion of the aquifer system to a specific depth. More than two dozen extensometers in the Central Valley were constructed in the 1950s, 1960s, and 1970s by the U.S. Geological Survey in cooperation with the California Department of Water Resources (Ireland and others, 1984), the early group of which represent the first extensometers ever built in the United States. Additionally, several extensometers have been constructed in the San Joaquin Valley more recently. All of the extensometers are constructed as cable or pipe borehole extensometers.
Extensometers are used in land subsidence studies to measure the compaction and expansion of the aquifer system to some depth. This pipe borehole dual-stage extensometer was built in 2008 in San Lorenzo, CA and measures compaction from 10 to about 300 meters. The illustration highlights the features that can be seen in the photograph. (Public domain.) - Publications
Below are publications relating to the use of extensometers in measuring aquifer compaction in California.
Land subsidence along the California Aqueduct in west-central San Joaquin Valley, California, 2003–10
Extensive groundwater withdrawal from the unconsolidated deposits in the San Joaquin Valley caused widespread aquifer-system compaction and resultant land subsidence from 1926 to 1970—locally exceeding 8.5 meters. The importation of surface water beginning in the early 1950s through the Delta-Mendota Canal and in the early 1970s through the California Aqueduct resulted in decreased groundwater pumWater availability and land subsidence in the Central Valley, California, USA
The Central Valley in California (USA) covers about 52,000 km2 and is one of the most productive agricultural regions in the world. This agriculture relies heavily on surface-water diversions and groundwater pumpage to meet irrigation water demand. Because the valley is semi-arid and surface-water availability varies substantially, agriculture relies heavily on local groundwater. In the southern tLithostratigraphic, borehole-geophysical, hydrogeologic, and hydrochemical data from the East Bay Plain, Alameda County, California
The U.S. Geological Survey, in cooperation with the East Bay Municipal Utility District, carried out an investigation of aquifer-system deformation associated with groundwater-level changes at the Bayside Groundwater Project near the modern San Francisco Bay shore in San Lorenzo, California. As a part of the Bayside Groundwater Project, East Bay Municipal Utility District proposed an aquifer storaLand subsidence in the San Joaquin Valley, California, USA, 2007-14
Rapid land subsidence was recently measured using multiple methods in two areas of the San Joaquin Valley (SJV): between Merced and Fresno (El Nido), and between Fresno and Bakersfield (Pixley). Recent land-use changes and diminished surface-water availability have led to increased groundwater pumping, groundwater-level declines, and land subsidence. Differential land subsidence has reduced the flLand subsidence along the Delta-Mendota Canal in the northern part of the San Joaquin Valley, California, 2003-10
Extensive groundwater withdrawal from the unconsolidated deposits in the San Joaquin Valley caused widespread aquifer-system compaction and resultant land subsidence from 1926 to 1970—locally exceeding 8.5 meters. The importation of surface water beginning in the early 1950s through the Delta-Mendota Canal and in the early 1970s through the California Aqueduct resulted in decreased pumping, initiaGroundwater availability of the Central Valley Aquifer, California
California's Central Valley covers about 20,000 square miles and is one of the most productive agricultural regions in the world. More than 250 different crops are grown in the Central Valley with an estimated value of $17 billion per year. This irrigated agriculture relies heavily on surface-water diversions and groundwater pumpage. Approximately one-sixth of the Nation's irrigated land is in theLand subsidence in the United States
No abstract available.Land subsidence in the United States
This report explores the role of science in defining and understanding subsidence problems, and shows that the optimal use of our land and water resources may depend on improved scientific understanding to minimize subsidence. More than 80 percent of the identified land subsidence in the Nation is a consequence of human impact on subsurface water, and is an often overlooked environmental consequen - News
Below are news stories associated with this project.
Extensometer Hunters: Searching for Long-Lost Technologies in San Joaquin Valley
San Joaquin Valley: the final frontier. These are the voyages of the U.S. Geological Survey. Its weeklong mission: to explore strange new locations, to seek out abandoned scientific technologies, to boldly go where no scientist has gone before (at least in a few decades).