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.

Groundwater-quality data collected between 1993 and 2015 were compiled from the U.S. Geological Survey (USGS) National Water Information System (NWIS) database for 722 wells in the San Joaquin Valley (SJV). Groundwater-quality data retrieved included lab analyses of complete major ion data (calcium, magnesium, sodium, potassium, chloride, sulfate, nitrate, alkalinity, bicarbonate, carbonate, silica, and TDS) for 613 samples, and an additional 109 samples with measured values of specific conductance. Most of these wells were sampled as part of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project or the USGS National Water Quality Assessment (NAWQA) Program. In addition to GW quality data, the dataset includes well depths, measured or interpolated water levels, summary land-use information, and a tritium-based groundwater age classification. Each well was assigned to a geospatial grid cell in one of six SJV regions (https://www.sciencebase.gov/catalog/item/5892423ee4b072a7ac145e06). These data support the following publication: Hansen, J.A., Jurgens, B.C, Fram, M.S., Quantifying Anthropogenic Contributions to Century-Scale Groundwater Salinity Changes, San Joaquin Valley, California, USA: Science of the Total Environment, vol. XX, no. X, pp. XX-XX, 2018.

Groundwater-quality data collected between 1993 and 2015 were compiled from the U.S. Geological Survey (USGS) National Water Information System (NWIS) database for 722 wells in the San Joaquin Valley (SJV). Groundwater-quality data retrieved included lab analyses of complete major ion data (calcium, magnesium, sodium, potassium, chloride, sulfate, nitrate, alkalinity, bicarbonate, carbonate, silica, and TDS) for 613 samples, and an additional 109 samples with measured values of specific conductance. Most of these wells were sampled as part of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project or the USGS National Water Quality Assessment (NAWQA) Program. In addition to GW quality data, the dataset includes well depths, measured or interpolated water levels, summary land-use information, and a tritium-based groundwater age classification. Each well was assigned to a geospatial grid cell in one of six SJV regions (https://www.sciencebase.gov/catalog/item/5892423ee4b072a7ac145e06). These data support the following publication: Hansen, J.A., Jurgens, B.C, Fram, M.S., Quantifying Anthropogenic Contributions to Century-Scale Groundwater Salinity Changes, San Joaquin Valley, California, USA: Science of the Total Environment, vol. XX, no. X, pp. XX-XX, 2018.

Mendenhall and others (1916) assessed groundwater resources in California's San Joaquin Valley in 1910 to estimate the availability of groundwater of suitable quality for agricultural, industrial, and drinking water supplies. They inventoried nearly all existing wells, compiled depth-to-water at 4,002 wells, and collected water-quality data at 485 wells. Samples were collected from 114 wells for laboratory analysis of total dissolved solids (TDS), chloride, sulfate, bicarbonate, carbonate, calcium, magnesium, sodium+potassium, and silica (Mendenhall and others. 1916; Dole, 1909). Field assays were used to measure TDS, chloride, sulfate, bicarbonate, carbonate, and total hardness in samples from 371 wells (Mendenhall and others. 1916; Leighton, 1905). Samples from 32 wells were analyzed using both laboratory and field assay methods. These data have been transcribed into a modern database format for use in future groundwater research.

Mendenhall and others (1916) assessed groundwater resources in California's San Joaquin Valley in 1910 to estimate the availability of groundwater of suitable quality for agricultural, industrial, and drinking water supplies. They inventoried nearly all existing wells, compiled depth-to-water at 4,002 wells, and collected water-quality data at 485 wells. Samples were collected from 114 wells for laboratory analysis of total dissolved solids (TDS), chloride, sulfate, bicarbonate, carbonate, calcium, magnesium, sodium+potassium, and silica (Mendenhall and others. 1916; Dole, 1909). Field assays were used to measure TDS, chloride, sulfate, bicarbonate, carbonate, and total hardness in samples from 371 wells (Mendenhall and others. 1916; Leighton, 1905). Samples from 32 wells were analyzed using both laboratory and field assay methods. These data have been transcribed into a modern database format for use in future groundwater research.

This report provides a full digitization of historic groundwater-quality and depth-to-water data from Mendenhall and others (1916) Water Supply Paper 398, “Ground Water in San Joaquin Valley, California” in a modern format suitable for further analysis of California’s water supply resources. Included are geochemical data for over 400 wells collected by Mendenhall in the fall of 1910, as well as depth-to-water and well construction information from over 4000 wells compiled by his team from over 15 years of well surveys throughout the San Joaquin Valley. Additionally, these data provide geospatial and geochemical data for sampled wells in California's San Joaquin Valley (SJV) in support of the publication: Hansen, J.A., Jurgens, B.C, Fram, M.S., Quantifying Anthropogenic Contributions to Century-Scale Groundwater Salinity Changes, San Joaquin Valley, California, USA, Science of the Total Environment, vol. XX, no. X, pp. XX-XX, 2018.

This report provides a full digitization of historic groundwater-quality and depth-to-water data from Mendenhall and others (1916) Water Supply Paper 398, “Ground Water in San Joaquin Valley, California” in a modern format suitable for further analysis of California’s water supply resources. Included are geochemical data for over 400 wells collected by Mendenhall in the fall of 1910, as well as depth-to-water and well construction information from over 4000 wells compiled by his team from over 15 years of well surveys throughout the San Joaquin Valley. Additionally, these data provide geospatial and geochemical data for sampled wells in California's San Joaquin Valley (SJV) in support of the publication: Hansen, J.A., Jurgens, B.C, Fram, M.S., Quantifying Anthropogenic Contributions to Century-Scale Groundwater Salinity Changes, San Joaquin Valley, California, USA, Science of the Total Environment, vol. XX, no. X, pp. XX-XX, 2018.

This data release is a compilation of construction depth information for 12,383 active and inactive public-supply wells (PSWs) in California from various data sources. Construction data from multiple sources were indexed by the California State Water Resources Control Board Division of Drinking Water (DDW) primary station code (PS Code). Five different data sources were compared with the following priority order: 1, Local sources from select municipalities and water purveyors (Local); 2, Local DDW district data (DDW); 3, The United States Geological Survey (USGS) National Water Information System (NWIS); 4, The California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment Groundwater Information System (SWRCB); and 5, USGS attribution of California Department of Water Resources well completion report data (WCR). For all data sources, the uppermost depth to the well's open or perforated interval was attributed as depth to top of perforations (ToP). The composite depth to bottom of well (Composite BOT) field was attributed from available construction data in the following priority order: 1, Depth to bottom of perforations (BoP); 2, Depth of completed well (Well Depth); 3; Borehole depth (Hole Depth). PSW ToPs and Composite BOTs from each of the five data sources were then compared and summary construction depths for both fields were selected for wells with multiple data sources according to the data-source priority order listed above. Case-by-case modifications to the final selected summary construction depths were made after priority order-based selection to ensure internal logical consistency (for example, ToP must not exceed Composite BOT). This data release contains eight tab-delimited text files. WellConstructionSourceData_Local.txt contains well construction-depth data, Composite BOT data-source attribution, and local agency data-source attribution for the Local data. WellConstructionSourceData_DDW.txt contains well construction-depth data and Composite BOT data-source attribution for the DDW data. WellConstructionSourceData_NWIS.txt contains well construction-depth data, Composite BOT data-source attribution, and USGS site identifiers for the NWIS data. WellConstructionSourceData_SWRCB.txt contains well construction-depth data and Composite BOT data-source attribution for the SWRCB data. WellConstructionSourceData_WCR.txt contains contains well construction depth data and Composite BOT data-source attribution for the WCR data. WellConstructionCompilation_ToP.txt contains all ToP data listed by data source. WellConstructionCompilation_BOT.txt contains all Composite BOT data listed by data source. WellConstructionCompilation_Summary.txt contains summary ToP and Composite BOT values for each well with data-source attribution for both construction fields. All construction depths are in units of feet below land surface and are reported to the nearest foot.

This data release is a compilation of construction depth information for 12,383 active and inactive public-supply wells (PSWs) in California from various data sources. Construction data from multiple sources were indexed by the California State Water Resources Control Board Division of Drinking Water (DDW) primary station code (PS Code). Five different data sources were compared with the following priority order: 1, Local sources from select municipalities and water purveyors (Local); 2, Local DDW district data (DDW); 3, The United States Geological Survey (USGS) National Water Information System (NWIS); 4, The California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment Groundwater Information System (SWRCB); and 5, USGS attribution of California Department of Water Resources well completion report data (WCR). For all data sources, the uppermost depth to the well's open or perforated interval was attributed as depth to top of perforations (ToP). The composite depth to bottom of well (Composite BOT) field was attributed from available construction data in the following priority order: 1, Depth to bottom of perforations (BoP); 2, Depth of completed well (Well Depth); 3; Borehole depth (Hole Depth). PSW ToPs and Composite BOTs from each of the five data sources were then compared and summary construction depths for both fields were selected for wells with multiple data sources according to the data-source priority order listed above. Case-by-case modifications to the final selected summary construction depths were made after priority order-based selection to ensure internal logical consistency (for example, ToP must not exceed Composite BOT). This data release contains eight tab-delimited text files. WellConstructionSourceData_Local.txt contains well construction-depth data, Composite BOT data-source attribution, and local agency data-source attribution for the Local data. WellConstructionSourceData_DDW.txt contains well construction-depth data and Composite BOT data-source attribution for the DDW data. WellConstructionSourceData_NWIS.txt contains well construction-depth data, Composite BOT data-source attribution, and USGS site identifiers for the NWIS data. WellConstructionSourceData_SWRCB.txt contains well construction-depth data and Composite BOT data-source attribution for the SWRCB data. WellConstructionSourceData_WCR.txt contains contains well construction depth data and Composite BOT data-source attribution for the WCR data. WellConstructionCompilation_ToP.txt contains all ToP data listed by data source. WellConstructionCompilation_BOT.txt contains all Composite BOT data listed by data source. WellConstructionCompilation_Summary.txt contains summary ToP and Composite BOT values for each well with data-source attribution for both construction fields. All construction depths are in units of feet below land surface and are reported to the nearest foot.

This digital data set contains the locations, water-level altitude, and water-level differences of 70 wells selected to document water-level changes between fall 2004 and spring 2005 in the Anza-Terwilliger area of Riverside County, California. The winter of 2005 was one of the wettest periods on record. Links to the U.S. Geological Survey National Water Information Systems Website (NWISWeb) have been established to interactively view recent water-level information via the internet by clicking on a specific well.