The U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (State Water Board) compiled and analyzed data for mapping groundwater salinity, characterizing aquifer systems, and documenting the effects of oil field water injection in the Elk Hills Elk Hills, Buena Vista, and Coles Levee Oil Fields, San Joaquin Valley, California. Data provided in this data release include borehole geophysical data, geochemical analyses of water samples, hydrologic data, geological formation depths, and information on observed well log resistivity anomalies—interpreted to be from injection for disposal of produced water from oil wells or from natural causes. The data reported here were used in an accompanying interpretive manuscript describing aquifer salinity and the effects of produced water disposal in the study area. The geochemical data were compiled for water samples from 14 water source wells to supply groundwater for oil and gas operations and one groundwater monitoring well. The constituents compiled from geochemical data sources included water-quality indicators and detected concentrations of major ions, minor ions, and trace elements. The data represent several decades and most originated from oil and gas producers which are archived in scanned pages in raster format on the California Geologic Energy Management Division (CalGEM) website. The data were compiled into computer readable numerical data sets for the related study. Other data, such as interpolated surfaces of geologic layers, were created for the study based on information in drilling records and are provided here. All the data and the associated manuscript are part of the State Water Board Oil and Gas Regional Monitoring Program and the associated USGS California Oil, Gas, and Groundwater (COGG) Program.

The California State Water Resources Control Board (State Water Board) initiated the Oil and Gas Regional Monitoring Program (RMP) to assess effects of oil and gas development on groundwater designated for any beneficial use. The U.S. Geological Survey (USGS) is the technical lead in conducting the RMP through the California Oil, Gas, and Groundwater (COGG) Program, working in cooperation with the State Water Board, and in partnership with other State and local agencies. The USGS collected and analyzed groundwater, surface water, and associated quality control (QC) samples in the Elk Hills study area during June 2017–April 2018. The Elk Hills study area includes the Elk Hills and North Coles Levee Oil Fields and a five-kilometer buffer zone surrounding the administrative boundaries of the two oil fields in Kern County, California. Water samples were collected from twenty-six monitoring wells, four irrigation wells, two public supply wells, and one managed recharge pond. Samples were collected using established groundwater data-collection protocols and procedures. Samples were analyzed for water-quality indicators, major and minor ions, nutrients, trace elements, volatile organic compounds (VOCs), naturally occurring radioactive material, geochemical and age-dating tracers, dissolved organic carbon (DOC) characteristics, dissolved standard and hydrocarbon gases (methane through hexane), and dissolved noble and atmospheric gases. Over 200 constituents and water-quality indicators were measured. Quality-control samples collected as part of this study included replicates, field blanks, equipment blanks, source-solution blanks, and matrix spikes.

The California State Water Resources Control Board (State Water Board) initiated the Oil and Gas Regional Monitoring Program (RMP) to assess effects of oil and gas development on groundwater designated for any beneficial use. The U.S. Geological Survey (USGS) is the technical lead in conducting the RMP through the California Oil, Gas, and Groundwater (COGG) Program, working in cooperation with the State Water Board, and in partnership with other State and local agencies. The USGS collected and analyzed groundwater, surface water, and associated quality control (QC) samples in the Elk Hills study area during June 2017–April 2018. The Elk Hills study area includes the Elk Hills and North Coles Levee Oil Fields and a five-kilometer buffer zone surrounding the administrative boundaries of the two oil fields in Kern County, California. Water samples were collected from twenty-six monitoring wells, four irrigation wells, two public supply wells, and one managed recharge pond. Samples were collected using established groundwater data-collection protocols and procedures. Samples were analyzed for water-quality indicators, major and minor ions, nutrients, trace elements, volatile organic compounds (VOCs), naturally occurring radioactive material, geochemical and age-dating tracers, dissolved organic carbon (DOC) characteristics, dissolved standard and hydrocarbon gases (methane through hexane), and dissolved noble and atmospheric gases. Over 200 constituents and water-quality indicators were measured. Quality-control samples collected as part of this study included replicates, field blanks, equipment blanks, source-solution blanks, and matrix spikes.

The U.S. Geological Survey collected groundwater samples from 38 wells used for domestic and small system drinking water supplies in the south-central Sierra Nevada region, California in 2023 and 2024. The wells were sampled for the Western Slope of the Sierra Nevada domestic-supply aquifer study unit of the California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project's (GAMA-PBP) assessment of the quality of groundwater resources used for domestic and small system drinking water supplies. The North High study area comprises the Eastern San Joaquin Highlands, Modesto Highlands, Turlock Highlands, and Merced Highlands groundwater units along the western slopes of the Sierra Nevada range, and the Mad King study area comprises the Yosemite Valley subbasin, Yosemite Highlands, Madera Highlands, and Kings Highlands groundwater units of the western slopes of the south-central Sierra Nevada range. The study unit was divided into 40 grid cells and one domestic or small system well was sampled to represent 38 of the grid cells; the remaining 2 grid cells had no accessible wells. Groundwater levels were measured in 13 of 38 wells. Table 1 contains sample and site information. Groundwater samples were analyzed for field water-quality parameters, microbial indicators, volatile organic compounds, pesticides and pesticide degradants, nutrients, major ions and trace elements, hexavalent chromium, perchlorate, per- and polyfluoroalkyl substances (PFAS), stable isotopes, and groundwater age tracers. Results from these analyses are reported in Tables 2 through 8. Tables 9 and 10 report results from quality control samples. This data release contains two supplementary tables that define abbreviations (Table 11) and provide additional context for the information presented in Tables 1 through 10 (Table 12). A zip file is included containing geospatial data (study unit boundaries, grid cell boundaries, site locations) as shapefiles.

This point dataset contains water-level information concerning depth to water, potentiometric-surface altitude, and saturated thickness for the shallow groundwater system at selected well and borehole locations in the Lower Gunnison River Basin in Delta, Montrose, Ouray, and Gunnison Counties, Colorado. Depth-to-water data were compiled from measurements reported by the Colorado Division of Water Resources, U.S. Geological Survey, and Bureau of Reclamation. Potentiometric-surface altitude values were computed from the potentiometric-surface altitude raster dataset (potalt). Saturated-thickness values were computed from the saturated-thickness raster dataset (satthk). The U.S. Geological Survey prepared this dataset in cooperation with the Colorado Water Conservation Board.

This point dataset contains water-level information concerning depth to water, potentiometric-surface altitude, and saturated thickness for the shallow groundwater system at selected well and borehole locations in the Lower Gunnison River Basin in Delta, Montrose, Ouray, and Gunnison Counties, Colorado. Depth-to-water data were compiled from measurements reported by the Colorado Division of Water Resources, U.S. Geological Survey, and Bureau of Reclamation. Potentiometric-surface altitude values were computed from the potentiometric-surface altitude raster dataset (potalt). Saturated-thickness values were computed from the saturated-thickness raster dataset (satthk). The U.S. Geological Survey prepared this dataset in cooperation with the Colorado Water Conservation Board.

This data set represents the extent of the Basin and Range aquifers in the states of California, Utah, Arizona, and Nevada.

This data set represents the extent of the Basin and Range aquifers in the states of California, Utah, Arizona, and Nevada.

This data set represents the extent of the Basin and Range carbonate-rock aquifers in the states of Idaho, Utah, Arizona, Nevada, and California.

This data set represents the extent of the Basin and Range carbonate-rock aquifers in the states of Idaho, Utah, Arizona, Nevada, and California.