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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.
Below are news stories associated with this project.
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).
This year, groundwater levels in many wells in California’s Central Valley are at or below historical low levels. In addition, from 2007 through 2015...