This dataset describes public-supply groundwater use by aquifer type within the glaciated conterminous United States between 2005 and 2014. All or part of 24 states within this glaciated region were included. The US Safe Drinking Water Act defines a "public water system" as an entity that provides water for human consumption through pipes or other constructed conveyances to at least 15 service connections or serves an average of at least 25 people for at least 60 days out of the year (United States Environmental Protection Agency, 1998). Water may be used for several purposes such as for commercial, industrial, and residential use, or may be used only for one specific purpose such as for residential use. This dataset includes public-supply water systems that furnish their own groundwater supply, purchase groundwater from a neighboring water system, or are mixed water systems that use both ground- and surface water. Groundwater sources include wells, springs, and cross-connections to another public groundwater system. Systems that use exclusively surface water are excluded from this dataset. The surface-water sources and withdrawals of mixed water systems are excluded; however, some population served values might include persons served surface water. Groundwater-use data that were collected from various agencies and resources spanned 2005-14, with a target year of 2010. Of the compiled withdrawal records, 95 percent were within the last five years, 2009-14, and 79 percent were from 2010. The year 2010 was chosen because it is the most recent year the USGS 5-year compilation report was published in United States Geological Survey (USGS) Circular 1405 (Maupin and others, 2014). The goal was to differentiate groundwater withdrawals from unconsolidated sediments of the Quaternary Period, glacial sand and gravel deposits and stream-valley alluvium, from other non-Quaternary aquifers, mostly bedrock aquifers. There are five aquifer types defined in this study, which are Quaternary, Cretaceous (unconsolidated deposits of the Cretaceous Period), Bedrock, Mixed, and Unknown. The water-use records include data from the United States Environmental Protection Agency (USEPA) and state agency databases. These records include 1) identifiers for the water system in the USEPA's Safe Drinking Water Information System (SDWIS) database, 2) type of public water supply system, 3) location, 4) population served by the system, 5) withdrawal rates, 6) well construction information, and 7) aquifer used. Most water systems and water sources were identified and located from the Safe Drinking Water Information System (SDWIS) (USEPA, 2013). Information on withdrawal rates, aquifer source, and well construction were compiled and cross-referenced from state and federal databases. Every water system and groundwater source had a withdrawal rate calculated or estimated. 90 percent (64,151 of 71,566 records) of the water system records had aquifer type assigned (either matched by associated records or estimated), and 41 percent (42,861 of 103,688 records) of the groundwater source records had well depth matched or inferred. The glacial aquifer system is an important source of water supply for the United States. Around 2010, total population served by groundwater from public water systems within the glaciated region is 42.9 million persons, and around 2010, total public-supply withdrawal is around 5,367 cubic hectometers per year (hm3/yr) or 3,884 million gallons per day (Mgal/d). Exactly half of the total public-supply withdrawal was from Quaternary sediments, more if some part of the withdrawals from mixed and unknown aquifer types is included.

The Groundwater Usage for Public Supply dataset contains attributes pertaining to groundwater use in the glaciated conterminous United States summarized by county. The attributes were computed from total groundwater usage by county compiled by Maupin and others (2010), and from inventories of water-use records for 71,267 public water-supply systems by Buchwald and others (in press). Source aquifers (Quaternary sediments or bedrock) were assigned for the public water-supply systems based on reported data (e.g., well construction records, aquifer delineation maps), or based on well depth and the Quaternary sediment thickness. Water usage rates are reported on an average annual, areal basis in units of millimeters per year, to facilitate comparison with estimated recharge rates from Westenbroek and others (in press).

The Groundwater Usage for Public Supply dataset contains attributes pertaining to groundwater use in the glaciated conterminous United States summarized by county. The attributes were computed from total groundwater usage by county compiled by Maupin and others (2010), and from inventories of water-use records for 71,267 public water-supply systems by Buchwald and others (in press). Source aquifers (Quaternary sediments or bedrock) were assigned for the public water-supply systems based on reported data (e.g., well construction records, aquifer delineation maps), or based on well depth and the Quaternary sediment thickness. Water usage rates are reported on an average annual, areal basis in units of millimeters per year, to facilitate comparison with estimated recharge rates from Westenbroek and others (in press).

This dataset provides the calculated proportion of people using publicly supplied groundwater (PSGF) for each county in the conterminous U.S. The county boundaries and the PSGF represent the year 2015.

This dataset provides the calculated proportion of people using publicly supplied groundwater (PSGF) for each county in the conterminous U.S. The county boundaries and the PSGF represent the year 2015.

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.

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.

This data release describes water service areas (WSA) for community water systems (CWS) within the conterminous United States, representing areas of active service between 2010 and 2020. A WSA is defined by a delineated polygon that contains all customers served by a water system. WSAs are represented by an ArcGIS shapefile. The U.S. Safe Drinking Water Act defines a CWS as a type of public-water system that serves at least 15 service connections used by year-round residents or regularly serves at least 25 year-round residents. Water may be used for several purposes (such as for commercial, industrial, and residential uses) or may be used only for one specific purpose (such as for residential use). This data release includes CWS that operate their own infrastructure and furnish water through their own water sources, purchase water from a neighboring water system, or are diversified in that they serve water from a combination of their own sources and purchases. This dataset also includes communities that do not operate a water system but receive water services by way of contract; in other words, an adjacent water system’s infrastructure extends their waterlines across boundaries from which residents connect to, are supplied, and directly billed from this neighboring water system.

This data release describes water service areas (WSA) for community water systems (CWS) within the conterminous United States, representing areas of active service between 2010 and 2020. A WSA is defined by a delineated polygon that contains all customers served by a water system. WSAs are represented by an ArcGIS shapefile. The U.S. Safe Drinking Water Act defines a CWS as a type of public-water system that serves at least 15 service connections used by year-round residents or regularly serves at least 25 year-round residents. Water may be used for several purposes (such as for commercial, industrial, and residential uses) or may be used only for one specific purpose (such as for residential use). This data release includes CWS that operate their own infrastructure and furnish water through their own water sources, purchase water from a neighboring water system, or are diversified in that they serve water from a combination of their own sources and purchases. This dataset also includes communities that do not operate a water system but receive water services by way of contract; in other words, an adjacent water system’s infrastructure extends their waterlines across boundaries from which residents connect to, are supplied, and directly billed from this neighboring water system.

The population using public supply drinking water was mapped in two ways: the census enhanced method (CEM) evenly distributes the population across the census block-group, and the urban land-use enhanced method (ULUEM) distributes the population only to certain urban land use designations in order to more precisely locate public supply users. This dataset consists of the estimated population using public supply groundwater distributed across census block-groups.