This digital dataset defines the spring 1961 hydraulic head in the lower pumped zone of California's Central Valley. It was used to initiate the water-level altitudes for the lower 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, 2006). 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 digital dataset defines the well locations, perforated intervals, and time series of hydraulic-head observations used in the calibration 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 U.S. Geological Survey (USGS) numerical modeling code MODFLOW-FMP (Schmid and others, 2006b). 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 USGS and CA-DWR maintain databases of key wells in the Central Valley that are web-accessible (http://waterdata.usgs.gov and http://www.water.ca.gov/waterdatalibrary/, respectively). These data were combined to form a database of available water levels throughout the Central Valley from 1961 to 2003. More than 850,000 water-level altitude measurements from more than 21,400 wells have been compiled by the USGS or CA-DWR and have been entered into their respective databases. However, only a small portion of these wells have both sufficient construction information to determine the well-perforation interval and water-level measurements for the simulation period. For model calibration, water-level altitude data were needed that were (1) distributed spatially (both geographically and vertically) throughout the Central Valley; (2) distributed temporally throughout the simulation period (years 1961-2003); and (3) available during both wet and dry climatic regimes. From the available wells records, a subset of comparison wells was selected on the basis of perforation depths, completeness of record, climatic intervals, and locations throughout the Central Valley. Water-level altitude observations (19,725) for 206 wells were used as calibration targets during parameter estimation. 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 defines the well locations, perforated intervals, and time series of hydraulic-head observations used in the calibration 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 U.S. Geological Survey (USGS) numerical modeling code MODFLOW-FMP (Schmid and others, 2006b). 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 USGS and CA-DWR maintain databases of key wells in the Central Valley that are web-accessible (http://waterdata.usgs.gov and http://www.water.ca.gov/waterdatalibrary/, respectively). These data were combined to form a database of available water levels throughout the Central Valley from 1961 to 2003. More than 850,000 water-level altitude measurements from more than 21,400 wells have been compiled by the USGS or CA-DWR and have been entered into their respective databases. However, only a small portion of these wells have both sufficient construction information to determine the well-perforation interval and water-level measurements for the simulation period. For model calibration, water-level altitude data were needed that were (1) distributed spatially (both geographically and vertically) throughout the Central Valley; (2) distributed temporally throughout the simulation period (years 1961-2003); and (3) available during both wet and dry climatic regimes. From the available wells records, a subset of comparison wells was selected on the basis of perforation depths, completeness of record, climatic intervals, and locations throughout the Central Valley. Water-level altitude observations (19,725) for 206 wells were used as calibration targets during parameter estimation. 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 defines the well locations for hydraulic-head observations used in the calibration 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 USGSs numerical modeling code MODFLOW-FMP (Schmid and others, 2006). This application 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 USGS and DWR maintain databases of key wells in the Central Valley that are web-accessible (http://waterdata.usgs.gov and http://www.water.ca.gov/waterdatalibrary/, respectively). These data were combined to form a database of available water levels throughout the Central Valley from 1961 to 2003. More than 850,000 water-level altitude measurements from more than 21,400 wells have been compiled by the USGS or DWR and have been entered into their respective databases. However, only a small proportion of these wells have both sufficient construction information to determine the well-perforation interval and water-level measurements for the simulation period. For model calibration, water-level altitude data were needed that were (1) distributed spatially (both geographically and vertically) throughout the Central Valley, from the valley trough to the foothills; (2) distributed temporally throughout the simulation period (1961-2003); and (3) available during both wet and dry climatic regimes. From the available wells records, a subset of comparison wells was selected on the basis of perforation depths, completeness of record, climatic intervals, and locations throughout the Central Valley. Water-level altitude observations (19,725) for 206 comparison wells were used as calibration targets during parameter estimation. 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 defines the well locations for hydraulic-head observations used in the calibration 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 USGSs numerical modeling code MODFLOW-FMP (Schmid and others, 2006). This application 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 USGS and DWR maintain databases of key wells in the Central Valley that are web-accessible (http://waterdata.usgs.gov and http://www.water.ca.gov/waterdatalibrary/, respectively). These data were combined to form a database of available water levels throughout the Central Valley from 1961 to 2003. More than 850,000 water-level altitude measurements from more than 21,400 wells have been compiled by the USGS or DWR and have been entered into their respective databases. However, only a small proportion of these wells have both sufficient construction information to determine the well-perforation interval and water-level measurements for the simulation period. For model calibration, water-level altitude data were needed that were (1) distributed spatially (both geographically and vertically) throughout the Central Valley, from the valley trough to the foothills; (2) distributed temporally throughout the simulation period (1961-2003); and (3) available during both wet and dry climatic regimes. From the available wells records, a subset of comparison wells was selected on the basis of perforation depths, completeness of record, climatic intervals, and locations throughout the Central Valley. Water-level altitude observations (19,725) for 206 comparison wells were used as calibration targets during parameter estimation. 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 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 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 digital geospatial data set contains the locations, values, and uncertainties of 700 hydraulic-head observations used in the steady-state, prepumped period of the transient model of the Death Valley regional ground-water flow system (DVRFS), a 100,000-square-kilometer region of southern Nevada and California. Hydraulic-head observations, which are the composite of one or more water-level measurements made at a well, are used to calibrate ground-water flow models. To develop hydraulic- head observations for the DVRFS ground-water flow model, nearly all available water levels for the DVRFS region through 2004 were compiled in Ground-Water Site Inventory (GWSI), the ground-water component of the U.S. Geological Survey (USGS) National Water Information System (NWIS) database. Water levels suitable for developing hydraulic-head observations representative of regional, steady-state ground-water flow conditions were identified through analyses. The resulting water levels were averaged for each well to produce one hydraulic-head observation value at each of 700 wells. The uncertainty of each hydraulic-head observation was statistically quantified from the values of uncertainties associated with well altitude and location, nonsimulated transient stress, and measurement accuracy.

This digital geospatial data set contains the locations, values, and uncertainties of 700 hydraulic-head observations used in the steady-state, prepumped period of the transient model of the Death Valley regional ground-water flow system (DVRFS), a 100,000-square-kilometer region of southern Nevada and California. Hydraulic-head observations, which are the composite of one or more water-level measurements made at a well, are used to calibrate ground-water flow models. To develop hydraulic- head observations for the DVRFS ground-water flow model, nearly all available water levels for the DVRFS region through 2004 were compiled in Ground-Water Site Inventory (GWSI), the ground-water component of the U.S. Geological Survey (USGS) National Water Information System (NWIS) database. Water levels suitable for developing hydraulic-head observations representative of regional, steady-state ground-water flow conditions were identified through analyses. The resulting water levels were averaged for each well to produce one hydraulic-head observation value at each of 700 wells. The uncertainty of each hydraulic-head observation was statistically quantified from the values of uncertainties associated with well altitude and location, nonsimulated transient stress, and measurement accuracy.

This digital geospatial data set contains the locations, values, and uncertainties of 700 hydraulic-head observations used in the steady-state, prepumped period of the transient model of the Death Valley regional ground-water flow system (DVRFS), a 100,000-square-kilometer region of southern Nevada and California. Hydraulic-head observations, which are the composite of one or more water-level measurements made at a well, are used to calibrate ground-water flow models. To develop hydraulic- head observations for the DVRFS ground-water flow model, nearly all available water levels for the DVRFS region through 2004 were compiled in Ground-Water Site Inventory (GWSI), the ground-water component of the U.S. Geological Survey (USGS) National Water Information System (NWIS) database. Water levels suitable for developing hydraulic-head observations representative of regional, steady-state ground-water flow conditions were identified through analyses. The resulting water levels were averaged for each well to produce one hydraulic-head observation value at each of 700 wells. The uncertainty of each hydraulic-head observation was statistically quantified from the values of uncertainties associated with well altitude and location, nonsimulated transient stress, and measurement accuracy.