This data release codifies and attributes explanatory variables that could potentially influence groundwater quality at 50 groundwater wells used for domestic water supply and 43 groundwater sites used for public water supply in the U.S. Geological Survey’s Priority Basin Project Redding-Red Bluff shallow aquifer (NSV-SA) study unit in 2018-2019 and Northern Sacramento Valley public-supply (NSV-PA) study unit in 2007, respectively. Water quality from domestic and public-supply groundwater sites was assessed as part of the California State Water Resources Control Board’s Groundwater Ambient Monitoring and Assessment (GAMA) program. The NSV-SA and NSV-PA study units include domestic and public-supply wells within sedimentary aquifers of the Central Valley province of California in Shasta and Tehama Counties. Study design and site selection for the NSV-SA and NSV-PA study units are detailed by Shelton and others (2020) and Bennett and others (2007), respectively. Potential explanatory factors are attributed to groundwater sites relating to: aquifer lithology, land use (percent agricultural, urban, and natural land use), septic tank and underground storage densities, distance to geothermal sites, hydrologic conditions (aridity index, elevation of the groundwater site), well construction (well depth, depth to the top of the open or perforated interval), groundwater age (tritium, carbon-14 and age classification), geochemical condition (pH, dissolved oxygen, groundwater redox classification). This data release contains a tab-delimited text file containing locations and potential explanatory factors for domestic groundwater sites (Table 1), a tab-delimited text file containing locations and potential explanatory factors for public groundwater sites (Table 2), and a data dictionary. These data support the following publications: Harkness, J.S.., 2022, Status and understanding of groundwater quality in the northern Sacramento Valley domestic-supply aquifer study unit, 2018–19—California GAMA Priority Basin Project: U.S. Geological Survey Scientific Investigations Report

The U.S. Geological Survey collected groundwater samples from 50 wells used for domestic and small system drinking water supplies in Shasta and Tehama Counties, California in 2018-2019. The wells were sampled for the Redding-Red Bluff Shallow Aquifer Study Unit of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project’s assessment of the quality of groundwater resources used for domestic and small system drinking water supplies. Domestic and small-system wells are commonly screened at shallower depths than public-supply wells. Wells in the study unit generally tap unconsolidated to moderately consolidated coarse and fine-grained sediments derived from the northern Coast Ranges to the west and the Cascade Range to the east. The Redding-Red Bluff Shallow Aquifer study unit included 11 groundwater subbasins of the Sacramento Valley groundwater basin (California Department of Water Resources, 2003) and was divided into two study areas: Redding (Enterprise, Millville, South Battle Creek, Bowman, Rosewood, and Anderson) and Red Bluff (Bend, Antelope, Dye Creek, Los Molinos, and Red Bluff). In each study area, the collective area of all one-mile square sections estimated to contain domestic wells (Johnson and Belitz, 2015) was divided into equal-area grid cells, and a well was sampled in each cell: Redding, twenty-five 48-square kilometer cells, and Red Bluff, twenty-five 43 square kilometer grid cells. Groundwater samples from all 50 wells were analyzed for field water-quality parameters and microbial indicators, volatile organic compounds, pesticides and pesticide degradates, major ions and trace elements, chromium (VI), perchlorate, nutrients, gross alpha and gross beta particle activities, carbon-14 in dissolved inorganic carbon, stable isotopic ratios of water, tritium, sulfur hexafluoride, and noble gases. Groundwater levels were measured in 41 of the 50 wells. All results are presented in this data release, except results for sulfur hexafluoride and noble gases. This data release supports the following publication: Groundwater quality in the Redding-Red Bluff Shallow Aquifer Study Unit of the Northern Sacramento Valley, California: U.S. Geological Survey Fact Sheet 2020–3025, 4 p., https://doi.org/10.3133/fs20203025.

The U.S. Geological Survey collected groundwater samples from 50 wells used for domestic and small system drinking water supplies in Shasta and Tehama Counties, California in 2018-2019. The wells were sampled for the Redding-Red Bluff Shallow Aquifer Study Unit of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project’s assessment of the quality of groundwater resources used for domestic and small system drinking water supplies. Domestic and small-system wells are commonly screened at shallower depths than public-supply wells. Wells in the study unit generally tap unconsolidated to moderately consolidated coarse and fine-grained sediments derived from the northern Coast Ranges to the west and the Cascade Range to the east. The Redding-Red Bluff Shallow Aquifer study unit included 11 groundwater subbasins of the Sacramento Valley groundwater basin (California Department of Water Resources, 2003) and was divided into two study areas: Redding (Enterprise, Millville, South Battle Creek, Bowman, Rosewood, and Anderson) and Red Bluff (Bend, Antelope, Dye Creek, Los Molinos, and Red Bluff). In each study area, the collective area of all one-mile square sections estimated to contain domestic wells (Johnson and Belitz, 2015) was divided into equal-area grid cells, and a well was sampled in each cell: Redding, twenty-five 48-square kilometer cells, and Red Bluff, twenty-five 43 square kilometer grid cells. Groundwater samples from all 50 wells were analyzed for field water-quality parameters and microbial indicators, volatile organic compounds, pesticides and pesticide degradates, major ions and trace elements, chromium (VI), perchlorate, nutrients, gross alpha and gross beta particle activities, carbon-14 in dissolved inorganic carbon, stable isotopic ratios of water, tritium, sulfur hexafluoride, and noble gases. Groundwater levels were measured in 41 of the 50 wells. All results are presented in this data release, except results for sulfur hexafluoride and noble gases. This data release supports the following publication: Groundwater quality in the Redding-Red Bluff Shallow Aquifer Study Unit of the Northern Sacramento Valley, California: U.S. Geological Survey Fact Sheet 2020–3025, 4 p., https://doi.org/10.3133/fs20203025.

The U.S. Geological Survey collected groundwater samples from 50 wells used for domestic and small system drinking water supplies in Shasta and Tehama Counties, California in 2018-2019. The wells were sampled for the Redding-Red Bluff Shallow Aquifer Study Unit of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project’s assessment of the quality of groundwater resources used for domestic and small system drinking water supplies. Domestic and small-system wells are commonly screened at shallower depths than public-supply wells. Wells in the study unit generally tap unconsolidated to moderately consolidated coarse and fine-grained sediments derived from the northern Coast Ranges to the west and the Cascade Range to the east. The Redding-Red Bluff Shallow Aquifer study unit included 11 groundwater subbasins of the Sacramento Valley groundwater basin (California Department of Water Resources, 2003) and was divided into two study areas: Redding (Enterprise, Millville, South Battle Creek, Bowman, Rosewood, and Anderson) and Red Bluff (Bend, Antelope, Dye Creek, Los Molinos, and Red Bluff). In each study area, the collective area of all one-mile square sections estimated to contain domestic wells (Johnson and Belitz, 2015) was divided into equal-area grid cells, and a well was sampled in each cell: Redding, twenty-five 48-square kilometer cells, and Red Bluff, twenty-five 43 square kilometer grid cells. Groundwater samples from all 50 wells were analyzed for field water-quality parameters and microbial indicators, volatile organic compounds, pesticides and pesticide degradates, major ions and trace elements, chromium (VI), perchlorate, nutrients, gross alpha and gross beta particle activities, carbon-14 in dissolved inorganic carbon, stable isotopic ratios of water, tritium, sulfur hexafluoride, and noble gases. Groundwater levels were measured in 41 of the 50 wells. All results are presented in this data release, except results for sulfur hexafluoride and noble gases. This data release supports the following publication: Groundwater quality in the Redding-Red Bluff Shallow Aquifer Study Unit of the Northern Sacramento Valley, California: U.S. Geological Survey Fact Sheet 2020–3025, 4 p., https://doi.org/10.3133/fs20203025.

The U.S. Geological Survey collected groundwater samples from 50 wells used for domestic and small system drinking water supplies in Shasta and Tehama Counties, California in 2018-2019. The wells were sampled for the Redding-Red Bluff Shallow Aquifer Study Unit of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project’s assessment of the quality of groundwater resources used for domestic and small system drinking water supplies. Domestic and small-system wells are commonly screened at shallower depths than public-supply wells. Wells in the study unit generally tap unconsolidated to moderately consolidated coarse and fine-grained sediments derived from the northern Coast Ranges to the west and the Cascade Range to the east. The Redding-Red Bluff Shallow Aquifer study unit included 11 groundwater subbasins of the Sacramento Valley groundwater basin (California Department of Water Resources, 2003) and was divided into two study areas: Redding (Enterprise, Millville, South Battle Creek, Bowman, Rosewood, and Anderson) and Red Bluff (Bend, Antelope, Dye Creek, Los Molinos, and Red Bluff). In each study area, the collective area of all one-mile square sections estimated to contain domestic wells (Johnson and Belitz, 2015) was divided into equal-area grid cells, and a well was sampled in each cell: Redding, twenty-five 48-square kilometer cells, and Red Bluff, twenty-five 43 square kilometer grid cells. Groundwater samples from all 50 wells were analyzed for field water-quality parameters and microbial indicators, volatile organic compounds, pesticides and pesticide degradates, major ions and trace elements, chromium (VI), perchlorate, nutrients, gross alpha and gross beta particle activities, carbon-14 in dissolved inorganic carbon, stable isotopic ratios of water, tritium, sulfur hexafluoride, and noble gases. Groundwater levels were measured in 41 of the 50 wells. All results are presented in this data release, except results for sulfur hexafluoride and noble gases. This data release supports the following publication: Groundwater quality in the Redding-Red Bluff Shallow Aquifer Study Unit of the Northern Sacramento Valley, California: U.S. Geological Survey Fact Sheet 2020–3025, 4 p., https://doi.org/10.3133/fs20203025.

This data release codifies and attributes explanatory factors that could potentially impact groundwater quality at 49 groundwater sites used for domestic water supply in the Sacramento Metropolitan Domestic-Supply Aquifer Study Unit (SacMetro-DSA). Water quality from domestic groundwater sites in the SacMetro-DSA was assessed as part of the California State Water Resources Control Board’s Groundwater Ambient Monitoring and Assessment (GAMA) program in 2017. The SacMetro-DSA study unit includes domestic wells within three Department of Water Resources defined groundwater subbasins; the North American, the South American, and the Cosumnes. Study design and site selection for the SacMetro-DSA study unit are detailed by Bennett and others (2019). Potential explanatory factors are attributed to domestic groundwater sites relating to: land use (percent agricultural, urban, and natural land use), underground storage and septic tank densities, hydrologic conditions (aridity index, elevation of the groundwater site), well construction (well depth, depth to the top of the open or perforated interval, well depth classification), groundwater age classification, and geochemical condition (groundwater redox classification, pH, dissolved oxygen). This data release contains a tab-delimited text file containing locations and potential explanatory factors for domestic groundwater sites in the SacMetro-DSA (Table 1). Additionally, an extensible markup language (XML) metadata file is included detailing process steps and references for attribution of potential explanatory factors to the groundwater sites. Bennett, G.L., V., Shelton, J.L., Watson, E., Johnson, T.D., and Jasper, M., 2019, Groundwater-quality data in the Sacramento Metro shallow aquifer study unit, 2017: Results from the California GAMA Priority Basin Project: U.S. Geological Survey data release Available at https://doi.org/10.5066/P9BPGEGH. These data support the following publications: Bennett, G.L. V, 2022, Status and Understanding of Groundwater Quality in the Sacramento Metropolitan Domestic-Supply Aquifer Study Unit, 2017: California GAMA Priority Basin Project: Geological Survey Scientific Investigations Report 2022–5021, 52 p., https://doi.org/10.3133/sir20225021.

This data release codifies and attributes explanatory factors that could potentially impact groundwater quality at 49 groundwater sites used for domestic water supply in the Sacramento Metropolitan Domestic-Supply Aquifer Study Unit (SacMetro-DSA). Water quality from domestic groundwater sites in the SacMetro-DSA was assessed as part of the California State Water Resources Control Board’s Groundwater Ambient Monitoring and Assessment (GAMA) program in 2017. The SacMetro-DSA study unit includes domestic wells within three Department of Water Resources defined groundwater subbasins; the North American, the South American, and the Cosumnes. Study design and site selection for the SacMetro-DSA study unit are detailed by Bennett and others (2019). Potential explanatory factors are attributed to domestic groundwater sites relating to: land use (percent agricultural, urban, and natural land use), underground storage and septic tank densities, hydrologic conditions (aridity index, elevation of the groundwater site), well construction (well depth, depth to the top of the open or perforated interval, well depth classification), groundwater age classification, and geochemical condition (groundwater redox classification, pH, dissolved oxygen). This data release contains a tab-delimited text file containing locations and potential explanatory factors for domestic groundwater sites in the SacMetro-DSA (Table 1). Additionally, an extensible markup language (XML) metadata file is included detailing process steps and references for attribution of potential explanatory factors to the groundwater sites. Bennett, G.L., V., Shelton, J.L., Watson, E., Johnson, T.D., and Jasper, M., 2019, Groundwater-quality data in the Sacramento Metro shallow aquifer study unit, 2017: Results from the California GAMA Priority Basin Project: U.S. Geological Survey data release Available at https://doi.org/10.5066/P9BPGEGH. These data support the following publications: Bennett, G.L. V, 2022, Status and Understanding of Groundwater Quality in the Sacramento Metropolitan Domestic-Supply Aquifer Study Unit, 2017: California GAMA Priority Basin Project: Geological Survey Scientific Investigations Report 2022–5021, 52 p., https://doi.org/10.3133/sir20225021.

The U.S. Geological Survey collected groundwater samples from 49 wells used for domestic and small system drinking water supplies in Amador, Placer, Sutter, and Sacramento Counties, California in 2017. The wells were sampled for the Sacramento Metropolitan (SacMetro) Shallow Aquifer Study Unit of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project’s assessment of the quality of groundwater resources used for domestic and small system drinking water supplies. Domestic and small-system wells are commonly screened at shallower depths than public-supply wells. The SacMetro study unit consisted of three “study areas” corresponding to three California Department of Water Resources groundwater subbasins: the North American and South American subbasins of the Sacramento Valley groundwater basin, and the Cosumnes subbasin of the San Joaquin Valley groundwater basin. Wells in the SacMetro study unit were in alluvial aquifers composed of sediments derived from the Sierra Nevada Mountains east of the study unit. The study unit was divided into 56 approximately 58 square kilometer grid cells, and a domestic or small-system well was sampled in 49 of those cells. Groundwater samples from all 49 wells were analyzed for field water-quality parameters, volatile organic compounds, pesticides and pesticide degradates, nutrients, major ions and trace elements, arsenic speciation, chromium (VI), perchlorate, gross alpha and gross beta particle activities, sulfur hexafluoride, tritium, carbon-14 in dissolved inorganic carbon, noble gases, stable isotopic ratios of water and dissolved nitrate, and microbial indicators. Groundwater levels were measured in 44 of the 49 wells. All results are presented in this data release, except results for pesticide and pesticide degradates. In 2017, the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program sampled 22 monitoring wells located in the SacMetro study unit as part of ongoing NAWQA studies of groundwater quality in different land-use settings. Of the 22 wells, 21 were part of an urban land-use network and 1 was part of a rice land use network. Results for analyses of perchlorate, chromium (VI), and stable isotopic ratios are presented in this data release, and results for analyses of field water-quality parameters, volatile organic compounds, pesticide and pesticide degradates, nutrients, major ions and trace elements, dissolved organic carbon, and tritium will be presented in a data release to be published separately by NAWQA. This data release supports the following publication: Groundwater Quality in the Sacramento Metropolitan shallow aquifer, California: U.S. Geological Survey Open-File Report 2019-1047, 4p., https://doi.org/10.3133/ofr20191047.

The U.S. Geological Survey collected groundwater samples from 49 wells used for domestic and small system drinking water supplies in Amador, Placer, Sutter, and Sacramento Counties, California in 2017. The wells were sampled for the Sacramento Metropolitan (SacMetro) Shallow Aquifer Study Unit of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project’s assessment of the quality of groundwater resources used for domestic and small system drinking water supplies. Domestic and small-system wells are commonly screened at shallower depths than public-supply wells. The SacMetro study unit consisted of three “study areas” corresponding to three California Department of Water Resources groundwater subbasins: the North American and South American subbasins of the Sacramento Valley groundwater basin, and the Cosumnes subbasin of the San Joaquin Valley groundwater basin. Wells in the SacMetro study unit were in alluvial aquifers composed of sediments derived from the Sierra Nevada Mountains east of the study unit. The study unit was divided into 56 approximately 58 square kilometer grid cells, and a domestic or small-system well was sampled in 49 of those cells. Groundwater samples from all 49 wells were analyzed for field water-quality parameters, volatile organic compounds, pesticides and pesticide degradates, nutrients, major ions and trace elements, arsenic speciation, chromium (VI), perchlorate, gross alpha and gross beta particle activities, sulfur hexafluoride, tritium, carbon-14 in dissolved inorganic carbon, noble gases, stable isotopic ratios of water and dissolved nitrate, and microbial indicators. Groundwater levels were measured in 44 of the 49 wells. All results are presented in this data release, except results for pesticide and pesticide degradates. In 2017, the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program sampled 22 monitoring wells located in the SacMetro study unit as part of ongoing NAWQA studies of groundwater quality in different land-use settings. Of the 22 wells, 21 were part of an urban land-use network and 1 was part of a rice land use network. Results for analyses of perchlorate, chromium (VI), and stable isotopic ratios are presented in this data release, and results for analyses of field water-quality parameters, volatile organic compounds, pesticide and pesticide degradates, nutrients, major ions and trace elements, dissolved organic carbon, and tritium will be presented in a data release to be published separately by NAWQA. This data release supports the following publication: Groundwater Quality in the Sacramento Metropolitan shallow aquifer, California: U.S. Geological Survey Open-File Report 2019-1047, 4p., https://doi.org/10.3133/ofr20191047.

The U.S. Geological Survey collected groundwater samples from 49 wells used for domestic and small system drinking water supplies in Amador, Placer, Sutter, and Sacramento Counties, California in 2017. The wells were sampled for the Sacramento Metropolitan (SacMetro) Shallow Aquifer Study Unit of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project’s assessment of the quality of groundwater resources used for domestic and small system drinking water supplies. Domestic and small-system wells are commonly screened at shallower depths than public-supply wells. The SacMetro study unit consisted of three “study areas” corresponding to three California Department of Water Resources groundwater subbasins: the North American and South American subbasins of the Sacramento Valley groundwater basin, and the Cosumnes subbasin of the San Joaquin Valley groundwater basin. Wells in the SacMetro study unit were in alluvial aquifers composed of sediments derived from the Sierra Nevada Mountains east of the study unit. The study unit was divided into 56 approximately 58 square kilometer grid cells, and a domestic or small-system well was sampled in 49 of those cells. Groundwater samples from all 49 wells were analyzed for field water-quality parameters, volatile organic compounds, pesticides and pesticide degradates, nutrients, major ions and trace elements, arsenic speciation, chromium (VI), perchlorate, gross alpha and gross beta particle activities, sulfur hexafluoride, tritium, carbon-14 in dissolved inorganic carbon, noble gases, stable isotopic ratios of water and dissolved nitrate, and microbial indicators. Groundwater levels were measured in 44 of the 49 wells. All results are presented in this data release, except results for pesticide and pesticide degradates. In 2017, the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program sampled 22 monitoring wells located in the SacMetro study unit as part of ongoing NAWQA studies of groundwater quality in different land-use settings. Of the 22 wells, 21 were part of an urban land-use network and 1 was part of a rice land use network. Results for analyses of perchlorate, chromium (VI), and stable isotopic ratios are presented in this data release, and results for analyses of field water-quality parameters, volatile organic compounds, pesticide and pesticide degradates, nutrients, major ions and trace elements, dissolved organic carbon, and tritium will be presented in a data release to be published separately by NAWQA. This data release supports the following publication: Groundwater Quality in the Sacramento Metropolitan shallow aquifer, California: U.S. Geological Survey Open-File Report 2019-1047, 4p., https://doi.org/10.3133/ofr20191047.