This data release documents 155 sets of dissolved noble gas analyses (neon, argon, krypton, xenon) and 153 modeled recharge temperatures for groundwater sampled from domestic water supply wells and springs throughout the northern Sierra Nevada foothills as part of the California State Water Resources Control Board’s Groundwater Ambient Monitoring and Assessment (GAMA) Program in 2015-2017. Data from two of the U.S. Geological Survey’s Priority Basin Project Shallow Aquifer Assessment study units are presented here: The Yuba and Bear Watersheds (YB) Shallow Aquifer Study Unit (sampled in 2015-2016) and the Mokelumne, Cosumnes, and American River Watersheds (MCAW) Shallow Aquifer Study Unit (sampled in 2016-2017). The YB and MCAW study units include domestic well and spring sites within watersheds overlying fractured rock aquifer systems of the Sierra Nevada hydrogeologic province of California in Nevada, Yuba, Sierra, Placer, El Dorado, Amador, and Calaveras Counties. Study design and site attributes for the YB and MCAW study units are presented by Jasper and others (2017) and Shelton and others (2018), respectively. This data release contains one tab-delimited text file containing Table 1, which reports the results of dissolved noble gas analyses for environmental samples from 72 sites in the YB study unit in addition to eight field replicates (80 samples total) and environmental samples from 67 sites in the MCAW study unit in addition to eight field replicates (75 samples total). Table 1 also contains groundwater recharge temperatures for 153 samples that were modeled using measured dissolved noble gas concentrations, land surface elevation at the sample site, and sample salinity. Model inputs and outputs including Monte Carlo simulations to estimate model parameter errors are also included in Table 1. Detailed descriptions for Table 1 column fields are provided in an additional tab-delimited text file of Table 1 column definitions. Abbreviations used in this data release are explained in an additional tab-delimited text file of abbreviations. These data support the following publications: Jasper, M., Bennett, G.L., and Fram, M.S., 2017, Groundwater-Quality Data in the Yuba and Bear Watersheds Shallow Aquifer Study Unit, 2015-2016: Results from the California GAMA Priority Basin Project: U.S. Geological Survey data release, https://doi.org/10.5066/F73F4MS9. Levy, Z.F., Fram, M.S., Faulkner, K.E., Alpers, C.N., Soltero, E.M., and Taylor, K.A., 2020, Effects of montane watershed development on vulnerability of domestic groundwater supply during drought: Journal of Hydrology, v. 583, https://doi.org/10.1016/j.jhydrol.2020.124567. Shelton, J.L., Fram, M.S., Goldrath, D.A., Bennett, G.L., V, and Jasper, M., 2018, Groundwater-quality data in the Mokelumne, Cosumnes, and American River Watersheds Shallow Aquifer Study Unit, 2016-2017: Results from the California GAMA Priority Basin Project: U.S. Geological Survey data release, https://doi.org/10.5066/F78G8JXP.

This data release documents three Microsoft Excel tables that contain data for understanding environmental tracer concentrations in groundwater of the Columbia Plateau aquifer system. Results of dissolved-gas modeling using environmental tracer concentrations (tritium, tritiogenic helium-3, and radiogenic helium-4), for the sample network (VPFS, vertical flow path study) are described. Dissolved gas modeling results (ModOut) contains detailed information on the calibration of dissolved gas models to measured dissolved-gas concentrations (neon, argon, krypton, xenon, and nitrogen). Calibration was done using methods described by Aeschbach-Hertig and others (1999 & 2000) with modifications to include nitrogen gas (Weiss, 1970). In most cases, a single set of noble-gas concentrations (neon, argon, krypton, and xenon) was used to solve for recharge conditions (recharge temperature, excess or entrapped air, and fractionation) using the unfractionated excess air (UA) and closed equilibration (CE) models (Aeschbach-Hertig and others, 1999 & 2000). In cases where noble gas data were not available, multiple analyses of nitrogen and argon (collected sequentially on the same sample date) were used to solve for recharge conditions. Environmental tracer results (TrcOut) contains detailed information on calculations of environmental tracer data. Dissolved gas models were paired with measured helium isotope ratios (3He/4He) and helium concentrations to calculate concentrations of tritiogenic helium-3 (the component of 3He derived from tritium decay; Solomon and Cook, 2000) and radiogenic helium-4 (the component of 4He derived from the decay of uranium and thorium in aquifer materials; Solomon, 2000). Tracer concentrations were computed for each combination of measure dissolved gas concentrations when sites had multiple measured gas results and analyses for helium isotopes. Average environmental tracer results (AvgTrcOut) contains average tracer concentrations for a given site used for determination of groundwater ages. Aeschbach-Hertig, W., F. Peeters, U. Beyerle, and R. Kipfer (1999), Interpretation of dissolved atmospheric noble gases in natural waters, Water Resour. Res., 35(9), 2779–2792,https://dx.doi.org/10.1029/1999WR900130. Aeschbach-Hertig, W., F. Peeters, U. Beyerle, and R. Kipfer (2000), Paleotemperature reconstruction from noble gases in ground water taking into account equilibration with entrapped air, Nature, v. 405, Iss. 6790, pg. 1040-1044, http://dx.doi.org/10.1038/35016542 Solomon, D.K., and P.G. Cook. 2000. 3H and 3He. In Environmental Tracers in Subsurface Hydrology, ed. P.G. Cook and A.L. Herczeg, 197-424. Boston: Kluwer Academic Publishers. Solomon, D.K. 2000. 4He in groundwater. In Environmental Tracers in Subsurface Hydrology, ed. P.G. Cook and A.L. Herczeg, 425-439. Boston: Kluwer Academic Publishers. Weiss, R. F., 1970, The solubility of nitrogen, oxygen, and argon in water and seawater, Deep Sea Research, vol. 17, pp. 721-735, https://doi.org/10.1016/0011-7471(70)90037-9.

Groundwater age distribution and susceptibility to natural and anthropogenic contaminants were assessed for selected principal aquifers of the Western United States: the Central Valley aquifer system (CVAL), the Basin and Range basin-fill aquifers (BNRF), the Rio Grande aquifer system (RIOG), the High Plains aquifer (HPAQ), the Columbia Plateau basaltic-rock aquifers (CLPT), and the Colorado Plateaus aquifers (COPL). Groundwater ages were estimated by calibration of environmental tracers (tritium, tritiogenic helium-3, chlorofluorocarbons, sulfur hexafluoride, carbon-14 and radiogenic helium-4) to lumped parameter models (LPMs) for 1,353 samples from 1,182 sample locations. Groundwater samples were collected from wells (mainly drinking-water) in the CVAL between 2004 and 2018 as part of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment Priority Basin Project (GAMA-PBP) and the National Water-Quality Assessment (NAWQA) Project; and in the BNRF in 2013, the RIOG in 2014 and 2015, the HPAQ between 2014 and 2017, the CPLT in 2016, and the COPL in 2017 as part of NAWQA. Table 1 reports the primary results of this assessment and it contains condensed results from dissolved gas modeling and calculated environmental tracer concentrations; results of the tritium age classification, susceptibility index, and mean groundwater age of each sample in this assessment; and water level and well construction information for some wells. Calibrated lumped parameter models provide the optimal mean age and mixing parameter(s) used to compute the distribution of ages that explain the measured tracer concentrations in a sample. Tables 2 and 3 provide results in support of Table 1. Table 2 reports detailed results for the calibration of dissolved gas models to neon, argon, krypton, xenon, and nitrogen. Calibrated dissolved gas models provide the optimal water temperature, excess air, entrapped air, fractionation of gases, and excess nitrogen gas (mainly from denitrification) that explain the measured dissolved gases in a sample. Table 3 reports measured concentrations and the detailed calculations of environmental tracer concentrations derived from the dissolved gas modeling results in Table 2. Calculated concentrations of environmental tracers that can be used in groundwater age calculations are the dry air mixing ratio of sulfur hexafluoride or chlorofluorocarbons, tritiogenic helium-3, which is the concentration of helium-3 from the decay of tritium, and radiogenic helium-4, which is the amount of helium generated from the decay of uranium and thorium in aquifer sediments. In addition to these three tables, two ancillary tables are included to provide more detailed information about the fields and the abbreviations used in tables 1-3.

The availability of groundwater-quality data along with geophysical information for relatively deep wells (wells generally more than 300 feet deep) containing saline water (dissolved-solids concentrations greater than 2,000 milligrams per liter)) is limited throughout the state of Texas. Water-quality samples are important for calibrating estimates of groundwater salinity derived from geophysical well logs. Water-quality samples and geophysical logs were collected from a total of 12 wells completed in selected aquifers (Trinity, Edwards-Trinity (Plateau), Carrizo-Wilcox, Sparta, and Yegua-Jackson) in Texas.

Water and gas chemistry data from: Mariner, R.H., Presser, T.S. and Evans, W.C., 1977. Hot springs of the central Sierra Nevada, California: U.S. Geological Survey Open-File Report 77-559, 37 p., https://doi.org/10.3133/ofr77559. Water chemistry data was digitized for 21 samples. Reported attributes include: Sample name, Type, Reported location, Location description, State, County, Latitude, Longitude, Location resolution, Location error, Temperature, pH (field), Aluminum (Al), Boron (B), Calcium (Ca), Chloride (Cl), Cesium (Cs), Copper (Cu), Fluoride (F), Iron (Fe), Hydrogen sulfide (H2S), Bicarbonate (HCO3), Alkalinity as bicarbonate (HCO3), Mercury (Hg), Potassium (K), Lithium (Li), Magnesium (Mg), Manganese (Mn), Sodium (Na), Ammonium (NH4), Nickel (Ni), Rubidium (Rb), Silica (SiO2), Sulfate (SO4), Zinc (Zn), Cations, Anions, Reported total dissolved solids, Salinity, Charge balance, Isotopic composition of hydrogen (Delta 2H), Isotopic composition of oxygen in water (Delta 18O H2O), Oxygen shift, Digitizer comment. Gas chemistry data was digitized for 12 samples. Reported attributes include: Sample name, Type, State, County, Latitude, Longitude, Location resolution, Location error, Total gas, Oxygen and argon (O2 + Ar), Ethane (C2H6), Methane (CH4), Carbon dioxide (CO2), Nitrogen (N2), Author comment, Digitizer comment. Data was digitized from Tables 1, 3, 4, 5, 7, 9, and 10. The following tables were not digitized: Table 2: age and lithology of the bedrock at each thermal spring. Table 6: the mole ratios of major to minor constituents of thermal springs. Table 8: the equilibrium states of reactions in the thermal springs. Table 11: measured temperatures and estimated reservoir temperatures for the thermal springs.

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.

These data are solubility calculations for dissolved gases in groundwater samples collected to support a U.S. Geological Survey study to estimate the timing and source of recharge to the basalt groundwater system in the Umatilla River basin, Oregon. The software package Dissolved Gas Modeling and Environmental Tracer Analysis (DGEMTA; Jurgens and others, 2020) was used to develop the solubility calculations. DGMETA produces estimates of dissolved gas concentrations during recharge as well as estimates of recharge temperature, excess air, and excess nitrogen gas concentrations by optimizing the solutions of solubility equations for multiple gases dissolved in samples of groundwater. These data were collected during August 26, 2014 – April 16, 2019. Data are in .csv file format. Reference cited: Jurgens, B.C., Böhlke, J., Haase, K., Busenberg, E., Hunt, A.G., and Hansen, J.A., 2020, DGMETA (version 1) - Dissolved gas modeling and environmental tracer analysis computer program: U.S. Geological Survey Techniques and Methods 4-F5, 50 p., https://doi.org/10.3133/tm4F5.

These data represent potential areas of ground-water discharge for selected hydrographic areas in eastern Nevada and western Utah. The data are based on phreatophyte boundaries published by the U.S. Geological Survey (USGS) and on unpublished boundaries mapped by the Southern Nevada Water Authority (SNWA). Selected basins also were mapped by the USGS during an aerial field reconnaissance. The largest phreatophyte extent from all the sources was typically selected as the final boundary where a basin was covered by multiple boundaries. Selected basins were field verified and modified to reflect the ground condition during the summer of 2005. This data set also includes subbasin boundaries identified by Sweetkind and others (2007) (See Source_Information). The table below lists the boundary sources for each valley and whether the data were ground verified. > Valley Sources Field > verified ------------------------------------------------------------------------------------------ >Little Smoky Nichols, 2000; Harrill, 1988 Yes >Newark Nichols, 2000; Harrill, 1988 Yes >Long Nichols, 2000; Harrill, 1988; SNWA Yes >Jakes Nichols, 2000; SNWA Yes >Butte Nichols, 2000; Harrill, 1988; SNWA Yes >Steptoe Nichols, 2000; Harrill, 1988; SNWA No >Tippett Nichols, 2000 No >Spring Nichols, 2000; Harrill, 1988; SNWA Yes >Snake Harrill, 1988; SNWA; Aerial No >Lake Harrill, 1988; SNWA; Aerial Yes >Cave SNWA; Aerial No >White River Harrill, 1988; SNWA; Aerial Yes

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

This U.S. Geological Survey (USGS) data release contains stream water chemistry and streamflow data collected in late August and early September, 2021 from 28 sites located throughout Colorado, USA. The sampled streams all drain high-elevation mountain watersheds in areas where the bedrock is hydrothermally altered and contains abundant sulfide minerals. Most sampled streams are therefore affected by natural acid-rock drainage. All sites had been sampled in prior years so that the 2021 data could be used to evaluate potential changes in stream water chemistry in recent decades. Streamflow was also quantified at most sites using data from a sodium chloride slug addition wherein specific conductivity readings were used as a surrogate for the tracer concentration.