This data set represents the extent of the Marshall aquifer in Michigan.

The Willamette Lowland basin-fill aquifers (hereinafter referred to as the Willamette aquifer) is located in Oregon and in southern Washington. The aquifer is composed of unconsolidated deposits of sand and gravel, which are interlayered with clay units. The aquifer thickness varies from less than 100 feet to 800 feet. The aquifer is underlain by basaltic-rock. Cities such as Portland, Oregon, depend on the aquifer for public and industrial use (HA 730-H). This product provides source data for the Willamette aquifer framework, including: Georeferenced images: 1. i_08WLMLWD_bot.tif: Georeferenced figure of altitude contour lines representing the bottom of the Willamette aquifer. The original figure was from Professional Paper 1424-A, Plate 2 (1424-A-P2). The contour lines from this figure were digitized to make the file c_08WLMLWD_bot.shp, and the fault lines were digitized to make f_08WLMLWD_bot.shp. Extent shapefiles: 1. p_08WLMLWD.shp: Polygon shapefile containing the areal extent of the Willamette aquifer (Willamette_AqExtent). The original shapefile was modified to create the shapefile included in this data release. It was modified to only include the Willamette Lowland portion of the aquifer. The extent file contains no aquifer subunits. Contour line shapefiles: 1. c_08WLMLWD_bot.shp: Contour line dataset containing altitude values, in feet, referenced to National Geodetic Vertical Datum of 1929 (NGVD29), across the bottom of the Willamette aquifer. These data were used to create the ra_08WLMLWD_bot.tif raster dataset. Fault line shapefiles: 1. f_08WLMLWD_bot.shp: Fault line dataset containing fault lines across the bottom of the Willamette aquifer. These data were not used in raster creation but were included as supplementary information. Altitude raster files: 1. ra_08WLMLWD_top.tif: Altitude raster dataset of the top of the Willamette aquifer. The altitude values are in meters reference to North American Vertical Datum of 1988 (NAVD88). The top of the aquifer is assumed to be land surface based on available data and was interpolated from the digital elevation model (DEM) dataset (NED, 100-meter). 2. ra_08WLMLWD_bot.tif: Altitude raster dataset of the bottom of the Willamette aquifer. The altitude values are in meters reference to NAVD88. This raster was interpolated from the c_08WLMLWD_bot.shp dataset. Depth raster files: 1. rd_08WLMLWD_top.tif: Depth raster dataset of the top of the Willamette aquifer. The depth values are in meters below land surface (NED, 100-meter). The top of the aquifer is assumed to be land surface based on available data. 2. rd_08WLMLWD_bot.tif : Depth raster dataset of the bottom of the Willamette aquifer. The depth values are in meters below land surface (NED, 100-meter).

The Arbuckle-Simpson aquifer covers an area of about 800 square miles in the Arbuckle Mountains and Arbuckle Plains of South-Central Oklahoma. The aquifer is in the Central Lowland Physiographic Province and is composed of the Simpson and Arbuckle Groups of Ordovician and Cambrian age. The aquifer is as thick as 9,000 feet in some areas. The aquifer provides relatively small, but important, amounts of water depended on for public supply, agricultural, and industrial use (HA 730-E). This product provides source data for the Arbuckle-Simpson aquifer framework, including: Georeferenced images: 1. i_46ARBSMP_bot.tif: Digitized figure of depth contour lines below land surface representing the base of fresh water in the Arbuckle-Simpson aquifer. The base of fresh water is considered to be the bottom of the Arbuckle-Simpson aquifer. The original figure is from the "Reconnaissance of the water resources of the Ardmore and Sherman Quadrangles, southern Oklahoma" report, map HA-3, page 2, prepared by the Oklahoma Geological Survey in cooperation with the U.S. Geological Survey (HA3_P2). Extent shapefiles: 1. p_46ABKSMP.shp: Polygon shapefile containing the areal extent of the Arbuckle-Simpson aquifer (Arbuckle-Simpson_AqExtent). The extent file contains no aquifer subunits. Contour line shapefiles: 1. c_46ABKSMP_bot.shp: Contour line dataset containing depth values, in feet below land surface, across the bottom of the Arbuckle-Simpson aquifer. This dataset is a digitized version of the map published in HA3_P2. This dataset was used to create the rd_46ABKSMP_bot.tif raster dataset. This map generalized depth values into zoned areas with associated ranges of depth. The edge of each zone was treated as the minimum value of the assigned range, thus creating the depth contour lines. This interpretation was favorable as it allowed for the creation of the resulting raster. This map was used because more detailed point or contour data for the area is unavailable. Altitude raster files: 1. ra_46ABKSMP_top.tif: Altitude raster dataset of the top of the Arbuckle-Simpson aquifer. The altitude values are in meters reference to North American Vertical Datum of 1988 (NAVD88). The top of the aquifer is assumed to be at land surface (NED, 100-meter) based on available data. This raster was interpolated from the Digital Elevation Model (DEM) dataset (NED, 100-meter). 2. ra_46ABKSMP_bot.tif: Altitude raster dataset of the bottom of the Arbuckle-Simpson aquifer. The altitude values are in meters referenced to NAVD88. Depth raster files: 1. rd_46ABKSMP_top.tif: Depth raster dataset of the top of the Arbuckle-Simpson aquifer. The depth values are in meters below land surface (NED, 100-meter). The top of the aquifer is assumed to be at land surface (NED, 100-meter) based on available data. 2. rd_46ABKSMP_bot.tif: Depth raster dataset of the bottom of the Arbuckle-Simpson aquifer. The depth values are in meters below land surface (NED, 100-meter). This raster was interpolated from the contour line dataset c_46ABKSMP_bot.shp.

The Central Oklahoma aquifer underlies an area of about 2,900 square miles in central Oklahoma. The aquifer is in the Central Lowland Physiographic Province and consists of Garber Sandstone and the Wellington Formation, which are part of the Sumner Group of Permian age. The maximum thickness of the aquifer is about 1,000 feet with a saturated thickness ranging from 150 to 650 feet. The aquifer is an important source of water for public, domestic, and commercial use (HA 730-E). This product provides source data for the Central Oklahoma aquifer framework, including: Georeferenced images: 1. i_27CNRLOK_bot.tif: Digitized figure of altitude contour lines representing the bottom of the Central Oklahoma aquifer. The original figure was from the Hydrologic Atlas 74, Plate 2, Figure 4 (HA_724_P2_F4). Extent shapefiles: 1. p_27CNRLOK.shp: Polygon shapefile containing the areal extent of the Central Oklahoma aquifer (OFR_96-454). The extent file contains no aquifer subunits. (Special Note) Other aquifer datasets included in the Brackish Water Project (PP1833) used the 'Ground Water Atlas of the United States' (HA 730-E) as a source for aquifer extents (Central_Oklahoma_AqExtent). This project sourced the extent from Open-File Report 96-454 (OFR_96-454) as it better matched the included top and bottom altitude of aquifer contour datasets. Contour line shapefiles: 1. c_27CNRLOK_top.shp: Contour line dataset containing altitude values, in feet reference to National Geodetic Vertical Datum of 1929 (NGVD29), across the top of the Central Oklahoma aquifer (OFR_96-454). These data were used to create the ra_27CNRLOK_top.tif raster dataset. 2. c_27CNRLOK_bot.shp: Contour line dataset containing altitude values, in feet reference to NGVD29, across the bottom of the Central Oklahoma aquifer (HA_724_P2_F4). These data were used to create the ra_27CNRLOK_bot.tif raster dataset. Altitude raster files: 1. ra_27CNRLOK_top.tif: Altitude raster dataset of the top of the Central Oklahoma aquifer. The altitude values are in meters reference to North American Vertical Datum of 1988 (NAVD88). This raster was interpolated from the c_27CNRLOK_top.shp dataset. 2. ra_27CNRLOK_bot.tif: Altitude raster dataset of the bottom of the Central Oklahoma aquifer. The altitude values are in meters reference to NAVD88. This raster was interpolated from the c_27CNRLOK_bot.shp dataset. Depth raster files: 1. rd_27CNRLOK_top.tif: Depth raster dataset of the top of the Central Oklahoma aquifer. The depth values are in meters below land surface (NED, 100-meter). 2. rd_27CNRLOK_bot.tif: Depth raster dataset of the bottom of the Central Oklahoma aquifer. The depth values are in meters below land surface (NED, 100-meter).

The Rush Springs aquifer resides in west-central Oklahoma with an area of about 1,400 square miles. The aquifer consists of the Rush Springs Sandstone and the Marlow Formation which are part of the Whitehorse Group of Permian age (HA 730-E). The Rush Springs Sandstone has a maximum thickness of about 300 feet and the Marlow Formation has a maximum thickness of about 125 feet. The aquifer is primarily and extensively used for irrigation (HA 730-E). This product provides source data for the Rush Springs aquifer framework, including: Georeferenced images: 1. i_26RSHSPG_bot.tif: Scanned figure of altitude contour lines representing the bottom of the Rush Springs aquifer. The original figure was from the Water-Resources Investigations Report 98-4081 (WRIR, 98-4081) figure 6. Extent shapefiles: 1. p_26RSHSPG.shp: Polygon shapefile containing the areal extent of the Rush Springs aquifer (Rush_Springs_AqExtent). The extent file contains no aquifer subunits. Contour line shapefiles: 1. c_26RSHSPG_top.shp: Contour line dataset containing altitude values, in feet reference to National Geodetic Vertical Datum of 1929 (NGVD29), across the top of the Rush Springs aquifer. This dataset was sourced from Rush_Springs_AqExtent and was used to create ra_26RSHSPG_top.tif raster dataset. 2. c_26RSHSPG_bot.shp: Contour line dataset containing altitude values, in feet reference to NGVD29, across the bottom of the Rush Springs aquifer. This dataset was sourced from WRIR, 98-4081 and was used to create ra_26RSHSPG_bot.tif raster dataset. Altitude raster files: 1. ra_26RSHSPG_top.tif: Altitude raster dataset of the top of the Rush Springs aquifer. The altitude values are in meters reference to North American Vertical Datum of 1988 (NAVD88). This raster was interpolated from the c_26RSHSPG_top.shp dataset. 2. ra_26RSHSPG_bot.tif: Altitude raster dataset of the bottom of the Rush Springs aquifer. The altitude values are in meters reference to NAVD88. This raster was interpolated from the c_26RSHSPG_bot.shp dataset. Depth raster files: 1. rd_26RSHSPG_top.tif: Depth raster dataset of the top of the Rush Springs aquifer. The depth values are in meters below land surface (NED, 100-meter). 2. rd_26RSHSPG_bot.tif: Depth raster dataset of the bottom of the Rush Springs aquifer. The depth values are in meters below land surface (NED, 100-meter).

This geospatial dataset represents a prototype of a finer-scale representation of the principal aquifers of the United States, using four original principal aquifers in the Upper Midwest, United States, which were re-analyzed and condensed into three updated principal aquifers. The original principal aquifer definitions and extents were published in the Ground Water Atlas of the United States at a scale of 1:5,000,000. The updated version in this dataset are based on a reinterpretation of the original definitions using geologic data from the U.S. Geological Survey (USGS) State Geologic Map Compilation (v 1.1, 2017), which contains published state data at scales from 1:50,000 to 1:1,000,000. This shapefile includes fields describing the original principal aquifer definitions and data links as well as ages, major and minor lithologies, and source data for the updated aquifer unit polygons. A detailed description of the process followed to evaluate the old definitions of the principal aquifers in the Ground Water Atlas of the United States in the context of the State Geologic Map compilation datasets can be found in the related primary publication.

The Western Interior Plains aquifer system is located in parts of Arkansas, Colorado, Kansas, Missouri, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming and covers an area of more than 220,800 square miles. The thickness of the aquifer system ranges from 500 feet in eastern Colorado (HA 730-D) to as much as 10,000 feet in western Oklahoma (PP_1414B). This aquifer system consists of water-bearing dolostone, limestone, and shale and overlies the basement confining unit in the western part of the Interior Plains physiographic division. This aquifer system consists of the upper aquifer unit (A1), a middle confining unit, and the lower aquifer unit (A2). The aquifer system is overlain by the Western Interior Plains confining system and is underlain by the Basement confining unit (PP_1414B). This product provides source data for the Western Interior Plains aquifer system framework, including: Georeferenced images: 1. i_63WIP_A1_top.tif: Digitized figure of extent and altitude contour lines representing the top of the Western Interior Plains aquifer system upper unit. The original figure was from PP_1414B plate 6. 2. i_63WIP_A1_bot.tif: Digitized figure of altitude contour lines of the top of the confining unit between the upper and lower units of the Western Interior Plains aquifer system. This figure was used to construct the bottom contour lines of the upper aquifer unit. The original figure was from PP_1414B plate 5. 3. i_63WIP_A2_top.tif: Digitized figure of extent and altitude contour lines representing the top of the Western Interior Plains aquifer system lower unit. The original figure was from PP_1414B plate 4. 4. i_63WIP_A2_bot.tif: Digitized figure of altitude contour lines of the top of the basement confining unit of the Western Interior Plains aquifer system. This figure was used to construct the bottom contour lines of the lower aquifer unit. The original figure was from PP_1414B plate 3. Extent shapefiles: 1. p_63WIP.shp: Polygon shapefile containing the areal extent of the Western Interior Plains aquifer system sourced from PP_1414B plates 4 and 6. The extent file contains the upper and lower subunits A1 and A2. Contour line shapefiles: 1. c_63WIP_A1_top.shp: Contour line dataset containing altitude values, in feet reference to National Geodetic Vertical Datum of 1929 (NGVD29), of the top of the Western Interior Plains aquifer system upper unit. These data were used to create the ra_63WIP_A1_top.tif dataset. 2. c_63WIP_A1_bot.shp: Contour line dataset containing altitude values, in feet reference to NGVD29, of the bottom of the Western Interior Plains aquifer system upper unit. These data were used to create the ra_63WIP_A1_bot.tif dataset. 3. c_63WIP_A2_top.shp: Contour line dataset containing altitude values, in feet reference to NGVD29, of the top of the Western Interior Plains aquifer system lower unit. These data were used to create the ra_63WIP_A2_top.tif dataset. 4. c_63WIP_A2_bot.shp: Contour line dataset containing altitude values, in feet reference to NGVD29, of the bottom of the Western Interior Plains aquifer system lower unit. These data were used to create the ra_63WIP_A2_bot.tif dataset. Altitude raster files: 1. ra_63WIP_A1_top.tif: Altitude raster dataset of the top of the Western Interior Plains aquifer system upper unit. The altitude values are in meters reference to North American Vertical Datum of 1988 (NAVD88). This raster was interpolated from contour line shapefile c_63WIP_A1_top.shp. 2. ra_63WIP_A1_bot.tif: Altitude raster dataset of the bottom of the Western Interior Plains aquifer system upper unit. The altitude values are in meters reference to NAVD88. This raster was interpolated from contour line shapefile c_63WIP_A1_bot.shp. 3. ra_63WIP_A2_top.tif: Altitude raster dataset of the top of the Western Interior Plains aquifer system lower unit. The altitude values are in meters reference to NAVD88. This raster was interpolated from contour line shapefile c_63WIP_A2_top.shp. 4.

The U.S. Geological Survey and its partners have collaborated to complete airborne geophysical surveys for areas of the North and South Platte River valleys and Lodgepole Creek in western Nebraska. The objective of the surveys was to map the aquifers and bedrock topography of selected areas to help improve the understanding of groundwater-surface-water relationships to be used in water management decisions. Frequency-domain (2008 and 2009) and time-domain (2010) helicopter electromagnetic surveys were completed, using a unique survey flight line design, to collect resistivity data that can be related to lithologic information for refinement of groundwater model inputs. To make the geophysical data useful for multidimensional groundwater models, numerical inversion is necessary to convert the measured data into a depth-dependent subsurface resistivity model. This inversion model, in conjunction with sensitivity analysis, geological ground truth (boreholes), and geological interpretation, is used to characterize hydrogeologic features. The two- and three- dimensional interpretation provides the groundwater modeler with a high-resolution hydrogeologic framework and a quantitative estimate of framework uncertainty. This method of creating hydrogeologic frameworks improved the understanding of the actual flow path orientation by redefining the location of the paleochannels and associated bedrock highs. The improved models represent the hydrogeology at a level of accuracy not achievable using previous data sets.

This dataset contains locations of aquifer boundaries and types of aquifer confinement.

This data set represents the extent of the Jacobsville aquifer in Michigan.