California's Central Valley ranges from the mountain fronts toward a central trough, mainly defined by the San Joaquin and Sacramento Rivers, and the relative distance from trough to valley edges is of interest. This data release provides supplemental data for the USGS Professional Paper 1766, titled Groundwater Availability of the Central Valley Aquifer, California and provides geographic information systems (GIS) datasets containing this relative distance grid and supporting data. Included in this data release are shapefiles used to define the Central Valley study area, the Central Valley trough, and a relative distance grid that may be used to spatially define other GIS data into zones between the edge of the Central Valley and the trough. These relative distances were calculated as part of groundwater availability study documented in the Professional Paper, for a 30 x 30-meter cell size grid for the Central Valley. The edge of the valley was represented by the boundary of the valley fill deposits and was assigned an arbitrary value of 1000. The valley trough was represented by the division of California's Department of Water Resource's groundwater subbasins from west to east, from the intersection of Enterprise, Anderson, and Millville subbasins in the north to the Westside and Kings subbasins in the south with an extended line through historic lakes Tulare, Buena Vista, and Kern. This valley trough was assigned a value of 0 which included the boundaries of the historic lakes.

This digital dataset defines the spring 1961 water-table altitude for the California's Central Valley. It was used to initiate the water-level altitudes for the upper zones of 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, 2009). 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 starting heads are based on the water-table and potentiometric surface developed by Williamson and others (1989). Maps of the spring 1961 water-table and hydraulic head in the lower pumped zone are shown in Figure 31 of Williamson and others (1989). 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 (Faunt, 2009. See "Foreword", Chapter A, page iii, for details).

This data set represents the extent of the Central Valley aquifer system in California.

This digital dataset contains the 9 major areas used to subdivide the Central Valley for the interpolation of the percentage of coarse-grained deposits into the texture model. This texture model was used as input data for the hydraulic properties portion of 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 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). In order to better characterize the aquifer-system deposits, lithologic data from approximately 8,500 drillers' logs of boreholes ranging in depth from 12 to 3,000 feet below land surface were compiled and analyzed. The percentage of coarse-grained sediment, or texture, then was computed for each 50-foot depth interval of the drillers' logs. A 3-dimensional texture model was developed by interpolating the percentage of coarse-grained deposits onto a 1-mile spatial grid at 50-foot-depth intervals from land surface to 2,800 feet below land surface. 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).

This digital dataset contains the 9 major areas used to subdivide the Central Valley for the interpolation of the percentage of coarse-grained deposits into the texture model. This texture model was used as input data for the hydraulic properties portion of 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 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). In order to better characterize the aquifer-system deposits, lithologic data from approximately 8,500 drillers' logs of boreholes ranging in depth from 12 to 3,000 feet below land surface were compiled and analyzed. The percentage of coarse-grained sediment, or texture, then was computed for each 50-foot depth interval of the drillers' logs. A 3-dimensional texture model was developed by interpolating the percentage of coarse-grained deposits onto a 1-mile spatial grid at 50-foot-depth intervals from land surface to 2,800 feet below land surface. 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).

The U.S. Geological Survey (USGS) entered into a cooperative study with the California Department of Water Resources and the Ramona Band of Cahuilla to characterize the hydrogeology of the Cahuilla Valley and Terwilliger Valley groundwater basins and surrounding water-bearing units, with the ultimate goal of developing a calibrated integrated hydrologic model to manage the groundwater supplies on a sustainable basis. A three-dimensional geologic framework model (GFM) was developed to quantify the structural geometry and distribution of water-bearing units in the groundwater basins, using borehole lithology and hydraulic information, geologic maps, and gravity-derived depth-to-basement information. This dataset includes (1) tabular data of selected boreholes with their location and construction information, (2) borehole lithology information, (3) a geographic information systems (GIS) shapefile of a cellular array containing interpolated elevations and thicknesses of modeled geologic units from the GFM in the format of a polygon feature class, (4) and a table of summary textural classes for the alluvial fill unit from borehole logs and summary textural classes used in geologic framework model.