This digital dataset contains the monthly urban (municipal and industrial use) pumpage for the Central Valley
Hydrologic Model (CVHM) by Water Balance Subregion (WBS). 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 U.S. Geological Survey(USGS) numerical modeling code MODFLOW-FMP
(Schmid and others, 2006). This application 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 on a finite difference grid comprising 441 rows and 98 columns.
Slightly less than 50 percent of the cells are active. The CVHM model grid has a uniform horizontal
discretization of 1x1 square mile and is oriented parallel to the valley axis, 34 degrees west of north
(Faunt, 2009). Groundwater pumpage is a major part of the groundwater budget of the Central Valley,
and is grouped into two categories for this study: agricultural and urban (which includes municipal and
industrial sources))(Diamond and Williamson, 1983). Urban wells were simulated as multi-node wells
(Halford and Hanson, 2002) (Faunt, 2009; fig. C3). In each WBS, a single well was placed in each model
cell where the predominant land use for a given time frame was urban (Brush, 2007). Because the extent
of urban areas changes through time, wells were added and deleted accordingly in the model during the
simulation period. In general, agricultural wells were replaced by urban wells in the model as the land use
changed from agricultural to urban. The single well per model cell represents the composite of all wells in
each square-mile cell and is referred to here as a virtual well. The CVHM is the most recent regional-scale
model of the Central Valley developed by the USGS. The CVHM was developed as part of the USGS
Groundwater Resources Program (see "Foreword", Chapter A, page iii, for details).
