This digital dataset is comprised of two separate data files that contain total dissolved solids, well construction, and well identifying information for 1,131 petroleum wells used to map salinity in and around 31 southern and central California oil fields. Salinity mapping was done for 27 fields located in the southern San Joaquin Valley of Kern County (North Belridge, South Belridge, Canfield Ranch, North Coles Levee, South Coles Levee, Cymric, Edison, Elk Hills, Fruitvale, Greeley, Jasmin, Kern Bluff, Kern Front, Kern River, Lost Hills, Mount Poso, Mountain View, Poso Creek, Rio Bravo, Rosedale, Rosedale Ranch, Round Mountain, San Emidio Nose, Tejon, Ten Section, Wheeler Ridge, and Yowlumne), 3 fields in the Los Angeles (LA) Basin of Los Angeles County (Montebello, Santa Fe Springs, and Wilmington), and 1 field in the central coast area of Santa Barbara and San Luis Obispo Counties (Santa Maria Valley). Only petroleum wells that were located within the administrative boundaries of these 31 fields were used for salinity mapping. The dataset includes total dissolved solids (TDS) analyses from 1930 to 2015. TDS data for each well varies from a single analysis to multiple analyses for different sample dates and (or) collected from different depths within the same well. For wells having multiple analyses TDS represents the median value. There are 159 wells in the dataset each having 2-4 TDS analyses, including 15 wells having TDS values from different depths. This dataset also includes ancillary data in the form of top perforation depth, land-surface elevation at the well head, and well location and identifier information. For petroleum wells missing top perforation depth (3 percent), the median top perforation depth for all wells within the field having top of perforation depth is provided as an approximation for the purpose of vertical plotting. Summary data about each well used for salinity mapping is contained in the file called Petroleum_Wells_Summary_Data. Detailed information about all individual TDS values including those used for determining median TDS values, are contained in the file called Petroleum_Wells_All_Data.

This digital dataset is comprised of three separate data files that contain total dissolved solids, well construction, and well identifying information for 3,546 water wells used to map salinity in and around 31 southern and central California oil fields. Salinity mapping was done for 27 fields located in the southern San Joaquin Valley of Kern County (North Belridge, South Belridge, Canfield Ranch, North Coles Levee, South Coles Levee, Cymric, Edison, Elk Hills, Fruitvale, Greely, Jasmin, Kern Bluff, Kern Front, Kern River, Lost Hills, Mount Poso, Mountain View, Poso Creek, Rio Bravo, Rosedale, Rosedale Ranch, Round Mountain, San Emidio Nose, Tejon, Ten Section, Wheeler Ridge, and Yowlumne), 3 fields in the LA Basin of Los Angeles County (Montebello, Santa Fe Springs, and Wilmington), and 1 field in the central coast area of Santa Barbara and San Luis Obispo Counties (Santa Maria Valley). Unlike petroleum wells, water wells both within and adjacent to oil fields of interest were used for salinity mapping. Water wells within an area (buffer) of 2-miles from the administrative field boundaries, with the exception of the Wilmington oil field with a buffer of 1-mile, were used for salinity mapping. Water wells located within overlapping buffer areas of adjacent oil fields were assigned to multiple fields for the purpose of being able to map salinity on a field-by-field basis. The dataset includes total dissolved solids (TDS) analyses from 1927 to 2016. Many of the analyses represent TDS concentrations that were calculated, as part of the salinity mapping, from specific conductance (SC) in lieu of reported TDS concentrations. Approximately 30 percent of the mapped water wells are wholly or partially derived from SC. In addition, approximately 50 percent of the water wells have TDS or SC analyses from more than one unique sample date. For wells having multiple analyses TDS represents the median value for the entire period of record, irrespective of whether it is from reported, calculated, or a combination of both TDS types. This dataset also includes ancillary data in the form of bottom perforation depth, well depth, or hole depth, land-surface elevation at the well head, and well location and identifier information. Bottom perforation depth was missing for about 65 percent of all water wells used for salinity mapping and were assigned a alternative value for plotting purposes. Where available, well depth or hole depth were used in lieu of bottom perforation depth. For water wells lacking bottom perforation, well depth, or hole depth (40 percent), the bottom perforation was estimated based on screen length when available (5 percent), or when the median bottom perforation or median well depth for all wells associated with an individual field is provided as an approximation for the purpose of vertical plotting (35 percent). Summary data about each well used for salinity mapping is contained in the file called Water_Wells_Summary_Data. Detailed information about all individual TDS values including those used for determining median TDS values, are contained in the file called Water_Wells_All_Data. Data used for the development of linear regression equations for calculating TDS from specific conductance in lieu of reported TDS values are contained in the file called Water_Wells_Regress_Data.

This digital dataset is comprised of three separate data files that contain total dissolved solids, well construction, and well identifying information for 3,546 water wells used to map salinity in and around 31 southern and central California oil fields. Salinity mapping was done for 27 fields located in the southern San Joaquin Valley of Kern County (North Belridge, South Belridge, Canfield Ranch, North Coles Levee, South Coles Levee, Cymric, Edison, Elk Hills, Fruitvale, Greely, Jasmin, Kern Bluff, Kern Front, Kern River, Lost Hills, Mount Poso, Mountain View, Poso Creek, Rio Bravo, Rosedale, Rosedale Ranch, Round Mountain, San Emidio Nose, Tejon, Ten Section, Wheeler Ridge, and Yowlumne), 3 fields in the LA Basin of Los Angeles County (Montebello, Santa Fe Springs, and Wilmington), and 1 field in the central coast area of Santa Barbara and San Luis Obispo Counties (Santa Maria Valley). Unlike petroleum wells, water wells both within and adjacent to oil fields of interest were used for salinity mapping. Water wells within an area (buffer) of 2-miles from the administrative field boundaries, with the exception of the Wilmington oil field with a buffer of 1-mile, were used for salinity mapping. Water wells located within overlapping buffer areas of adjacent oil fields were assigned to multiple fields for the purpose of being able to map salinity on a field-by-field basis. The dataset includes total dissolved solids (TDS) analyses from 1927 to 2016. Many of the analyses represent TDS concentrations that were calculated, as part of the salinity mapping, from specific conductance (SC) in lieu of reported TDS concentrations. Approximately 30 percent of the mapped water wells are wholly or partially derived from SC. In addition, approximately 50 percent of the water wells have TDS or SC analyses from more than one unique sample date. For wells having multiple analyses TDS represents the median value for the entire period of record, irrespective of whether it is from reported, calculated, or a combination of both TDS types. This dataset also includes ancillary data in the form of bottom perforation depth, well depth, or hole depth, land-surface elevation at the well head, and well location and identifier information. Bottom perforation depth was missing for about 65 percent of all water wells used for salinity mapping and were assigned a alternative value for plotting purposes. Where available, well depth or hole depth were used in lieu of bottom perforation depth. For water wells lacking bottom perforation, well depth, or hole depth (40 percent), the bottom perforation was estimated based on screen length when available (5 percent), or when the median bottom perforation or median well depth for all wells associated with an individual field is provided as an approximation for the purpose of vertical plotting (35 percent). Summary data about each well used for salinity mapping is contained in the file called Water_Wells_Summary_Data. Detailed information about all individual TDS values including those used for determining median TDS values, are contained in the file called Water_Wells_All_Data. Data used for the development of linear regression equations for calculating TDS from specific conductance in lieu of reported TDS values are contained in the file called Water_Wells_Regress_Data.

The U.S. Geological Survey (USGS) and California State University-Sacramento, in cooperation with the California State Water Resources Control Board and U.S. Bureau of Land Management, compiled and analyzed data for mapping groundwater salinity in selected oil and gas fields in California. The data for the Midway-Sunset (MWSS) oil field includes digitized borehole geophysical data, geochemical analyses of produced water samples from oil and gas wells, core sample analysis from select wells, and groundwater total dissolved solids (TDS) estimations with the related geophysical log data. These data have been compiled from many sources and span several decades. The geochemical data include ion concentrations and TDS which are attributed with the sample date, geological formation, and perforation depths. These data have been in archived scanned pages of historical lab analyses on the Division of Oil, Gas, and Geothermal Resources (DOGGR) website. The borehole geophysical data has been provided by California Division of Oil, Gas, and Geothermal Resources (DOGGR). These data were compiled primarily to create groundwater salinity maps to assist in regional groundwater monitoring as part of the California State Water Resources Control Board's Program of Regional Monitoring of Water Quality in Areas of Oil and Gas Production and the USGS California Oil, Gas, and Groundwater (COGG) program.

The U.S. Geological Survey (USGS) and California State University-Sacramento, in cooperation with the California State Water Resources Control Board and U.S. Bureau of Land Management, compiled and analyzed data for mapping groundwater salinity in selected oil and gas fields in California. The data for the Midway-Sunset (MWSS) oil field includes digitized borehole geophysical data, geochemical analyses of produced water samples from oil and gas wells, core sample analysis from select wells, and groundwater total dissolved solids (TDS) estimations with the related geophysical log data. These data have been compiled from many sources and span several decades. The geochemical data include ion concentrations and TDS which are attributed with the sample date, geological formation, and perforation depths. These data have been in archived scanned pages of historical lab analyses on the Division of Oil, Gas, and Geothermal Resources (DOGGR) website. The borehole geophysical data has been provided by California Division of Oil, Gas, and Geothermal Resources (DOGGR). These data were compiled primarily to create groundwater salinity maps to assist in regional groundwater monitoring as part of the California State Water Resources Control Board's Program of Regional Monitoring of Water Quality in Areas of Oil and Gas Production and the USGS California Oil, Gas, and Groundwater (COGG) program.

This digital dataset contains geochemical and other information for 1,209 samples of groundwater from 343 wells located within 3-miles of the Buena Vista, Elk Hills, Midway-Sunset, and North and South Coles Levee oil fields in the southwestern San Joaquin Valley of central California. Data were compiled by the U.S. Geological Survey (USGS) from preexisting datasets and transferred manually into two separate data files described as follows: 1) a summary data file identifying each well, it's location, basic well construction, the number of chemistry samples and period of record, and data sources; and 2) a data file of geochemistry analyses for selected water-quality indicators, major and minor ions, nutrients, and trace elements, plus parameter code and (or) method, reporting level, reporting level type, and supplemental notes. A data dictionary was created to describe the geochemistry data file and is provided with this data release.

This digital dataset contains geochemical and other information for 1,209 samples of groundwater from 343 wells located within 3-miles of the Buena Vista, Elk Hills, Midway-Sunset, and North and South Coles Levee oil fields in the southwestern San Joaquin Valley of central California. Data were compiled by the U.S. Geological Survey (USGS) from preexisting datasets and transferred manually into two separate data files described as follows: 1) a summary data file identifying each well, it's location, basic well construction, the number of chemistry samples and period of record, and data sources; and 2) a data file of geochemistry analyses for selected water-quality indicators, major and minor ions, nutrients, and trace elements, plus parameter code and (or) method, reporting level, reporting level type, and supplemental notes. A data dictionary was created to describe the geochemistry data file and is provided with this data release.

The U.S. Geological Survey (USGS) compiled and analyzed data for mapping groundwater total dissolved solids (TDS) at the San Ardo Oil Field in Monterey County, California. Data include groundwater TDS and bicarbonate concentration from oil well and groundwater well samples, formation resistivity from borehole geophysical logs, porosity from well logs and rock core samples, temperature from water samples and well logs, selected oil well injection volumes, and geological formation depths. The data reported here are used in an accompanying manuscript (Stephens and others, 2025) that describes methods and results of mapping groundwater TDS. The modeled values from the related manuscript are also provided. A portion of these data were found in archived scanned pages in raster format on the California Geologic Energy Management Division (CalGEM) website (CalGEM, 2022) and have been compiled into machine readable numerical format. Other data, such as the geological layers, were generated during this project by interpreting borehole geophysical data from CalGEM (2022). All the data analyzed are part of the California State Water Resources Control Board Oil and Gas Regional Monitoring Program and the USGS California Oil, Gas, and Groundwater (COGG) program.

This dataset consists of 119,494 lines of data consisting of idle well fluid level depth, auxiliary measurements, and well parameters from California oil and gas wells that were reported to the California Department of Conservation, Geologic Energy Management Division (CalGEM). The dataset was provided by CalGEM in March 2018 and includes measurements made from 1976 to 2018. There are 5 sets of operator-reported data: idle well fluid level depth (N=101,734), well clean out depth (N=8,402), depth of base of fresh water (N=108,216), well top perforation depth (N=93,569), and depth reached (N=15,756). These are associated with a well, defined by API number, well number, operator name, test date, township, section, range, and pool code. While detailed metadata for these measurements was not provided by CalGEM, they are thought to be collected under idle well testing regulations. Present regulations broadly define an idle well as one that has not been used for production or injection for 24 months or longer (California Code of Regulations, 2022, Title 14 §1760). Below, a summary of current regulations related to this program are presented; however, regulations at the time of data collection may be different. Once a well is classified as an idle well, a fluid level test using acoustical, mechanical, or other methods must be conducted within 24 months, and every 24 months beyond that, as long as a well is idle, unless the wellbore does not penetrate an underground source of drinking water (USDW) (California Code of Regulations, 2022, Title 14 §1772.1). Currently, within 8 years of a well becoming idle a clean out tag is required. This is done to demonstrate that the well can be properly plugged and abandoned. A clean out tag is done by passing open-ended tubing or a gauge ring of a minimum diameter equal to that of tubing necessary to plug and abandon a well (California Code of Regulations, 2022, Title 14 §1772.1). This testing must generally be repeated once every 48 months as long as a well is classified as an idle well. Freshwater is defined as water that contains 3,000 milligrams/liter (mg/L) or less of total dissolved solids (California Code of Regulations, 2022, Title 14 §1720.1). The base of freshwater is the depth in a well where the overlying water is freshwater. Neither top perforation depth or depth reached is defined by statute. Top perforation is generally the shallowest active perforated interval. It is not clear what depth reached represents. Well elevation and pool name were added from other datasets to aid in analysis. Pools, identified by pool code and pool name, are defined as independent hydrocarbon zones (California Public Resources Code § 3227.6.b). The accuracy of the values reported to CalGEM by oil-field operators is unknown. Unrealistic values were discarded from the data as noted in the process steps. This dataset was compiled and analyzed as part of the California State Water Resources Control Board Oil and Gas Regional Monitoring Program and the U.S. Geological Survey California Oil, Gas, and Groundwater (COGG) program.

The U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board compiled and analyzed data for the purpose of mapping groundwater salinity in selected oil and gas fields in California. The data for the Fruitvale and Rosedale Ranch oil fields include well construction data, digitized borehole geophysical data, geochemical analyses of water samples from oil and gas wells and groundwater wells, geological formation depths, and the groundwater total dissolved solids (TDS) calculations used in an accompanying manuscript. These data have been compiled from many sources and span several decades. The well construction data includes attributes such as the date drilling began (spud date), well depth, the depth of top producing perforation, and borehole orientation. These data have been in archived scanned pages in raster format on the Division of Oil, Gas, and Geothermal Resources (DOGGR) website. Similarly, the borehole geophysical data, measured by oil companies, has been archived in raster format. This project has converted the borehole geophysical data from selected oil and gas wells into a computer readable numerical format. The geochemical analyses have also been archived in scanned formats, but now have been compiled into numerical datasets in additional data releases by Metzger and others (2018) and Gans and others (2018). All of the data compiled and analyzed are part of the California State Water Resources Control Board's Program of Regional Monitoring of Water Quality in Areas of Oil and Gas Production and the USGS California Oil, Gas, and Groundwater (COGG) program.