A seamless map of the major groundwater areas used by community public supply wells in the United States was needed in order to describe and compute the number of equivalent people using public supply water. This goal was met by the delineation of hydrogeologic mapping units (HMUs). An HMU is a mapped polygon, within which, all public supply wells have a common source of water. The source of water can be either a national Principal Aquifer (PA) as defined in USGS (2003) or a Secondary Hydrogeologic Region (SHR) as defined in Belitz et al. (2018). Collectively, both PAs and SHRs are referred to as Hydrogeologic Regions (HRs). The common source of water can be a single HR or multiple HRs, as HRs can overlap one another. The proportion of the wells assigned to an HR within an HMU determined the proportion that an HR was assigned to the HMU. In the case of the glacial HR, pumping rates were also used. The boundaries of the HMUs are derived from established PA and SHR boundaries. Likewise, the name of the HMU is derived from the PA or SHR from which it was based. Although an HMU may have been named and derived its boundary from an HR, the public supply wells within it may be getting water from a completely different (overlapping or underlaying) HR. In total, 177 unique HMUs were created. The HMU polygons have several beneficial properties. There are no overlapping polygons. The HMUs are internally consistent with the original source HRs and their buried extents. At least 95% of the wells located within an HMU source their water from HRs within the HMU. The HMU boundary only contains areas where an HR can exist. See the related publication information for more descriptive information about this dataset and the process to create it.

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 U.S. Geological Survey (USGS), in cooperation with the Pennsylvania Department of Environmental Protection (PADEP), conducted an evaluation of data used by the PADEP to identify groundwater sources under the direct influence of surface water (GUDI) in Pennsylvania (Gross and others, 2022). The data used in this evaluation and the processes used to compile them from multiple sources are described and provided herein. Data were compiled primarily but not exclusively from PADEP resources, including (1) source-information for public water-supply systems and Microscopic Particulate Analysis (MPA) results for public water-supply system groundwater sources from the agency’s Pennsylvania Drinking Water Information System (PADWIS) database (Pennsylvania Department of Environmental Protection, 2016), and (2) results associated with MPA testing from the PADEP Bureau of Laboratories (BOL) files and water-quality analyses obtained from the PADEP BOL, Sample Information System (Pennsylvania Department of Environmental Protection, written commun., various dates). Information compiled from sources other than the PADEP includes anthropogenic (land cover and PADEP region) and naturogenic (geologic and physiographic, hydrologic, soil characterization, and topographic) spatial data. Quality control (QC) procedures were applied to the PADWIS database to verify spatial coordinates, verify collection type information, exclude sources not designated as wells, and verify or remove values that were either obvious errors or populated as zero rather than as “no data.” The QC process reduced the original PADWIS dataset to 12,147 public water-supply system wells (hereafter referred to as the PADWIS database). An initial subset of the PADWIS database, termed the PADWIS database subset, was created to include 4,018 public water-supply system community wells that have undergone the Surface Water Identification Protocol (SWIP), a protocol used by the PADEP to classify sources as GUDI or non-GUDI (Gross and others, 2022). A second subset of the PADWIS database, termed the MPA database subset, represents MPA results for 631 community and noncommunity wells and includes water-quality data (alkalinity, chloride, Escherichia coli, fecal coliform, nitrate, pH, sodium, specific conductance, sulfate, total coliform, total dissolved solids, total residue, and turbidity) associated with groundwater-quality samples typically collected concurrently with the MPA sample. The PADWIS database and two subsets (PADWIS database subset and MPA database subset) are compiled in a single data table (DR_2022_Table.xlsx), with the two subsets differentiated using attributes that are defined in the associated metadata table (DR_2022_Metadata_Table_Variables.xlsx). This metadata file (DR_2022_Metadata.xml) describes data resources, data compilation, and QC procedures in greater detail.

This data release includes grids representing the depth and thickness of drinking-water withdrawal zones, polygons of hydrogeologic settings, an inventory of sources of well construction data, and summaries of data comparisons used to assess the depth of groundwater used for drinking-water supplies in the United States. Well construction data sources are documented in Table1_DataSources.xlsx. Data comparisons using the Mann-Whitney test to assess similarity between hydrogeologic settings were used to justify combining data where they were sparse (compare_neighbors_all_domestic.txt and compare_neighbors_all_public.txt). Water-supply-well depth varies geographically by water use and the type of well, which illustrates the need to identify the depth of domestic drinking water withdrawal and depth of public supply drinking water withdrawal zones. Water-supply-well depth also varies by aquifer; therefore median values were calculated for each Principal Aquifer (PA), Secondary Hydrogeologic Region (SHR) between PAs and PA or SHR associated with overlying sediment polygons, where present, including glacial (G), coarse glacial (GC), and stream-valley alluvium (AV) polygons (all termed hydrogeologic settings here). A polygon shape file of hydrogeologic settings is included in this data release (HG_Settings.zip) and includes well counts and median thicknesses and depths for each area. This data release documents an inventory of well construction data sources and thickness and median top and bottom of drinking water depth zones by aquifer for domestic and public supplies. This data release includes equations used for estimating information for wells missing information on the depth to the top/length of the open interval. This data release contains: HG_Settings.zip --Shape file with well counts and median depth and thickness for hydrogeologic setting areas compare_neighbors_all_domestic.txt --results of Mann-Whitney tests to assess domestic-supply well construction data similarity between hydrogeologic settings compare_neighbors_all_public.txt --results of Mann-Whitney tests to assess public-supply well construction data similarity between hydrogeologic settings Depth_of_Drinking_Water_Supplies_Metadata03162021.xml --Metadata NonReferencedDomestic.txt --An inventory of domestic-supply well data that are not published elsewhere NonReferencedPublic.txt --An inventory of public-supply well data that are not published elsewhere Table1_DataSources.xlsx --An inventory of databases, references, state web sites, and individual state contacts for data sources. The logic behind data extraction algorithms is also defined for each data source. A tab delimited text version with the same name is also available. Lithology_OpenIntervalLengthFit.txt --Parameters for equations used for estimating open intervals by lithology, overlying sediment, and well type HydrogeologicSetting_OpenIntervalLengthFit.txt --Parameters for equations used for estimating open intervals by hydrogeologic setting and well type domestic_grids.zip contains: domestic_bottom_dist_to_5.asc --Grid of domestic-supply well open interval bottom depth data density, distance to reach 5 wells with information on the bottom of the open interval domestic_open_dist_to_5.asc --Grid of domestic-supply well open interval length data density, distance to reach 5 wells with information on open interval length domestic_bottom_open.asc --Grid of domestic-supply well depth to the bottom of the open interval domestic_len_open.asc --Grid of domestic-supply well open-interval length domestic_top_open.asc --Grid of domestic-supply well depth to the top of the open interval public_grids.zip contains: public_bottom_dist_to_5.asc --Grid of the public-supply well open interval bottom depth data density, distance to reach 5 wells with information on the bottom of the open interval public_open_dist_to_5.asc --Grid of the public-supply well open interval length data density, distance to reach 5 wells with

Well construction data for 11,917 domestic and 2,390 public-supply wells in the Central Valley were compiled as part of the U.S. Geological Survey (USGS) National Water Quality Assessment Project (NAWQA) and California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP). Data were compiled for wells reported in the USGS National Water Information System (NWIS) database and from well information reported to the SWRCB Department of Drinking Water (SWRCB-DDW). Driller’s log data were transcribed from scanned images of well completion reports filed with California Department of Water Resources (DWR). The wells reported in this data release were filtered by water use to select domestic and public-supply wells and omit other water uses. The compilation was then assumed to be representative of the total population of domestic and public-supply wells in the Central Valley. The wells in the compilation were constructed between 1911 and 2008 but are not grouped or separated by date. The data were used to produce two point data sets containing well location and construction information (depth from land surface to the top and bottom of the well screen, hereafter well-screen tops and bottoms; and screen length), and 12 interpolated GIS raster surfaces created by using Empirical Bayesian Kriging on a 1600 by 1600 meter (1 square-mile) grid. The tables are also included in csv format. The 12 rasters comprise predicted values for well screen tops and bottoms and their 10th and 90th quantile values. The interpolated surfaces may also be used to calculate volumes of water-supply in the Central Valley defined by the well-screen tops and bottoms.

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.

The U.S. Geological Survey collected water-quality samples from 3,199 sites between May 2004 and April 2022 for the California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP). The GAMA-PBP is a cooperative project with the California State Water Resources Control Board (SWRCB). The primary objectives of the GAMA-PBP are: (1) to assess the quality of groundwater resources used for public and domestic drinking water supplies, (2) to develop understanding of the natural and anthropogenic processes controlling groundwater quality and changes in groundwater quality, and (3) to improve the availability and usefulness of groundwater quality information to public. This data release publishes site type information and a generalized use category for the sites. The dataset comprises 3,053 wells, 81 springs, and 65 other types of sites. The generalized use category is partially derived from, but is not equivalent to, the use of site and use of water fields from the USGS National Water Information System (NWIS) data archive. Of the 2,903 wells and springs from which water is withdrawn for use, 1,651 are classified as production (includes sites used for public, commercial, industrial, institutional, and desalination water supplies), 973 as domestic, 264 as irrigation, and 15 as other water supply uses. Of the remaining sites, 225 are classified as observation wells, 6 are wells and springs from which water is withdrawn and not used, 63 are distribution system taps, and 2 are other types of sites. GAMA-PBP data are also served to the public through the SWRCB's GAMA Groundwater Information System (GAMAGIS), along with data from other federal, state, and local agency sources, and the generalized use categories in this data release are compatible with the use categories in SWRCB GAMAGIS. Prior to publication of this data release, SWRCB GAMAGIS classified all GAMA-PBP sites as "municipal", which resulted in erroneous characterization of approximately half of the sites. The generalized classification provided in this data release greatly improves the accuracy of site characterization, while still complying with Federal policies concerning release of location information for some types of sites. Version 1.0 posted September 29, 2021 Version 2.0 posted August 31, 2022 Changes in Version 2.0 1) A total of 143 sites were added to the data release. Seventy-one (71) sites were sampled for the first time by the GAMA-PBP between July 2021 and April 2022 after publication of Version 1.0 of this data release. Seventy-two (72) sites were sampled prior to publication of Version 1.0, but were inadvertently omitted. 2) A new Site_Type, DISTRIBUTION SYSTEM, was added, and a process step was added to describe how and why it is used. Of the 72 sites omitted from Version 1.0, 63 were distribution system sites sampled in 2012-2013. 3) The GAMAIDs for two sites were corrected. Site 342959117133002 is S8-MOBSU-U09 (given as S8-MOBSU-U10 in Version 1.0), and Site 342959117133003 is S8-MOBSU-U10 (given as S8-MOBSU-U09 in Version 1.0) 4) A second GAMAID was added to seven WELL sites that were also sampled as DISTRIBUTION SYSTEM sites under a different GAMAID but the same USGS Site_Number (363700121500001, 365425121452201, 354000120410001, 354501120413301,354911120452701, 360600121000001, 361631121112001) 5) The USE_CATEGORY for 8 sites was changed for consistency with how use of those sites is described elsewhere. Three natural springs and one unused well were changed from the category OTHER to the category OBSERVATION (413600122240001, 383548122360601, 382925122294901, 373738119045501). Four wells were changed from category WATER SUPPLY, OTHER (364800118110001, 382307122311301) or category OBSERVATION (382702122423701, 365000120450001) to category PRODUCTION to reflect that the sites are standby or not currently in use but when the water is used, the use is in the PRODUCTION category. 6) References were added to the process steps

Groundwater-quality data were collected from 648 wells as part of the National Water-Quality Assessment Project of the U.S. Geological Survey National Water-Quality Program and are included in this report. Most of the wells (514) were sampled from January through December 2016 and 60 of them were sampled in 2013 and 74 in 2014. The data were collected from seven types of well networks: principal aquifer study networks, which are used to assess the quality of groundwater used for public water supply; land-use study networks, which are used to assess land-use effects on shallow groundwater quality; major aquifer study networks, which are used to assess the quality of groundwater used for domestic supply; enhanced trends networks, which are used to evaluate the time scales during which groundwater quality changes; vertical flow-path study networks, which are used to evaluate changes in groundwater quality from shallow to deeper depths; flow path study networks, which are used to evaluate changes in groundwater quality from shallow to deeper depths over a horizontal distance; and modeling support studies, which are used to provide data to support groundwater modeling. Groundwater samples were analyzed for a large number of water-quality indicators and constituents, including major ions, nutrients, trace elements, volatile organic compounds, pesticides, radionuclides, and some special interest constituents (arsenic speciation, chromium [VI] and perchlorate). These groundwater quality data are tabulated in a U.S. Geological Survey Data Series Report DS-1124 which is available at https://dx.doi.org/XXXXXX and in this data release. Some data from environmental samples collected in 2013-14 and quality-control samples collected in 2012-15 also are included in the associated data release. Data from samples collected in 2016 are associated with networks described in this report and have not been published previously; data from samples collected between 2012 and 2015 are associated with networks described in previous reports in this data series (Arnold and others, 2016a,b, 2017a,b, 2018a,b). There are 23 data tables included in this data release and they are referenced as tables 1-13 and appendix tables 4.10-4.19 in the larger work citation. There are 36 tables that are part of the larger work citation; the 13 tables not included in the data release are summary tables derived from some of the other tables (tables 1.1, 2.2-2.3, 3.1, 4.1-4.9). A version of table 1 is included in both the text and data release. This compressed file contains 23 files of groundwater-quality data in ASCII text tab-delimited format and one corresponding metadata in xml format that describes all the tables and attributes.

The U.S. Geological Survey collected water-quality samples from 3,359 sites between May 2004 and November 2024 for the California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP). The GAMA-PBP is a cooperative project with the California State Water Resources Control Board (SWRCB). The primary objectives of the GAMA-PBP are: (1) to assess the quality of groundwater resources used for public and domestic drinking water supplies, (2) to develop understanding of the natural and anthropogenic processes controlling groundwater quality and changes in groundwater quality, and (3) to improve the availability and usefulness of groundwater quality information to public. This data release publishes site type information and a generalized use category for the sites. The dataset comprises 3,213 wells, 81 springs, and 65 other types of sites. The generalized use category is partially derived from, but is not equivalent to, the use of site and use of water fields from the USGS National Water Information System (NWIS) data archive. Of the 3,063 wells and springs from which water is withdrawn for use, 1,696 are classified as production (includes sites used for public, commercial, industrial, institutional, and desalination water supplies), 1,123 as domestic, 263 as irrigation, and 16 as other water supply uses. Of the remaining sites, 229 are classified as observation wells, 6 are wells and springs from which water is withdrawn and not used, 63 are distribution system taps, and 4 are other types of sites. GAMA-PBP data are also served to the public through the SWRCB's GAMA Groundwater Information System (GAMAGIS), along with data from other federal, state, and local agency sources, and the generalized use categories in this data release are compatible with the use categories in SWRCB GAMAGIS. Prior to publication of this data release, SWRCB GAMAGIS classified all GAMA-PBP sites as "municipal", which resulted in erroneous characterization of approximately half of the sites. The generalized classification provided in this data release greatly improves the accuracy of site characterization, while still complying with Federal policies concerning release of location information for some types of sites. Version 1.0 posted September 29, 2021 Version 2.0 posted September 2, 2022 Version 3.0 posted October 25, 2023 Version 4.0 posted April, 2025