GIS Data


Well Information

Well construction data for 11,917 domestic and 2,390 public-supply wells in the Central Valley were compiled as part of the U.S. Geological Survey (USGS) National Water Quality Assessment Project (NAWQA) and California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP). Data were compiled for wells reported in the USGS National Water Information System (NWIS) database and from well information reported to the SWRCB Department of Drinking Water (SWRCB-DDW). Driller’s log data were transcribed from scanned images of well completion reports filed with California Department of Water Resources (DWR). The wells reported in this data release were filtered by water use to select domestic and public-supply wells and omit other water uses. The compilation was then assumed to be representative of the total population of domestic and public-supply wells in the Central Valley. The wells in the compilation were constructed between 1911 and 2008 but are not grouped or separated by date. The data were used to produce two point data sets containing well location and construction information (depth from land surface to the top and bottom of the well screen, hereafter well-screen tops and bottoms; and screen length), and 12 interpolated GIS raster surfaces created by using Empirical Bayesian Kriging on a 1600 by 1600 meter (1 square-mile) grid. The tables are also included in csv format. The 12 rasters comprise predicted values for well screen tops and bottoms and their 10th and 90th quantile values. The interpolated surfaces may also be used to calculate volumes of water-supply in the Central Valley defined by the well-screen tops and bottoms.