Measured compaction for 24 extensometers in the Central Valley

This digital dataset contains the compaction data for 24 extensometers used for observations
in the Central Valley Hydrologic Model (CVHM). The Central Valley encompasses an approximate
50,000 square-kilometer region of California. The complex hydrologic system of the Central Valley
is simulated using the USGS numerical modeling code MODFLOW-FMP (Schmid and others, 2006).
This simulation is referred to here as the CVHM (Faunt, 2009). Utilizing MODFLOW-FMP, the CVHM
simulates groundwater and surface-water flow, irrigated agriculture, land subsidence, and other key
processes in the Central Valley on a monthly basis from 1961-2003. The total active modeled area
is 20,334 square-miles. Water levels, water-level altitude changes, and water-level and potentiometric-
surface altitude maps; streamflows; boundary flows; subsidence; groundwater pumpage; water use;
and water-delivery observations were used to constrain parameter estimates throughout the calibration
of the CVHM. Measured compaction from extensometers placed in the valley was used as a subsidence
calibration target. The extensometer locations were obtained from USGS files and GPS locations.
Subsidence monitoring observations can provide valuable information about hydrologic parameters
such as elastic and inelastic skeletal specific storage. The CVHM was adjusted to fit the range of
measured compaction at the extensometer sites utilizing UCODE-2005 (Poeter and others, 2006)
and manual calibration. The calibration target was the measured compaction from several extensometers
in the region. Compaction though delayed drainage and re-pressurizing of aquitards was not simulated.
The CVHM is the most recent regional-scale model of the Central Valley developed by the U.S.
Geological Survey (USGS). The CVHM was developed as part of the USGS Groundwater Resources
Program (see "Foreword", Chapter A, page iii, for details).