Data for depth of groundwater used for drinking-water supplies in the United States (ver. 2.0, January 2026)

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. The original version targeted the median depth of the well. Version 2.0 added rasters representing the 95th percentile of the well depth. 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) (USGS, 2003), Secondary Hydrogeologic Region (SHR) (Belitz and others, 2018a) 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 shapefile 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. The 95th percentile is used rather than the maximum to eliminate outliers and potentially any errors in the databases from having an undue influence on the final results. The approach for the 95th percentile grid differed from the approach for the median grids in several ways, including a bigger radius to select wells, a higher number of target points, more smoothing, combining domestic and public supply datasets, and using the hydrogeologic regions (Kauffman and Belitz, 2025) rather than the hydrogeologic settings used for the median calculations References cited: Belitz, K., Watson, E., Johnson, T.D., and Sharpe, J.B., 2018a, Data release for secondary hydrogeologic regions of the conterminous United States (ver. 2.0, June 2022): U.S. Geological Survey data release, https://doi.org/10.5066/F7F76BSS. Kauffman, L.J., and Belitz, K., 2025. Hydrogeologic regions of the conterminous United States: U. S. Geological Survey data release, https://doi.org/10.5066/P1F39LHM. U.S. Geological Survey, 2003, Principal aquifers of the 48 Conterminous United States, Hawaii, Puerto Rico, and the U.S. Virgin Islands: U.S. Geological Survey data release, https://doi.org/10.5066/P9Y2HOUJ.

                                            [
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                                            {
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