This digital dataset defines the model grid, water-balance subregions (WBSs), soil types, and virtual crops for the five land-use time-frames in the transient hydrologic model of the Central Valley flow system. 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, 2006a, b). This simulation is referred to here as the Central Valley Hydrologic Model (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 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). The 21 WBSs initially were identified by the California Department of Water Resources (CA-DWR) and Bureau of Reclamation (BOR) as numbered "Depletion Study Areas" (California Department of Water Resources, 1977). The WBSs are used as accounting units for surface-water delivery and for estimation of groundwater pumpage. The boundaries generally represent hydrographic rather than political subdivisions, particularly in the San Joaquin and Tulare Basins. The soils were simplified into sandy loam, silty clay, and silt from the State Soil Geographic Database STATSGO (U.S. Department of Agriculture Natural Resources Conservation Service, 2005b). The soil type covering the maximum area of each cell was assigned to each cell. The land-use attributes are defined in the model on a cell-by-cell basis and include urban and agricultural areas, water bodies, and natural vegetation. The land use, referred to as "virtual crops," that covered the largest fraction of each 1 square mile model cell was the representative land use specified for that cell. Land-use maps were developed for five different time frames during the 42.5-year simulation period. 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).