The Southern Nevada volcanic-rock aquifers reside in southern-central Nevada. This group of aquifers can be categorized into welded tuff, bedded tuff, and lava flow aquifers. Each of these categories possess different physical characteristics and have varying degrees of welding and number of interconnected joints. The lithology of these aquifers is primarily dependent on mode of eruption and cooling and are highly variable. Because the lithology is so variable, so is groundwater transmission, storage, and yield (HA 730-B). This product provides source data for the Southern Nevada volcanic-rock aquifers framework, including: Extent shapefiles: 1. p_57SRNVDV.shp: Polygon shapefile containing the areal extent of the Southern Nevada volcanic-rock aquifers (SRNVDV_AqExtent). The extent file contains no aquifer subunits. Altitude raster files: 1. ra_57SRNVDV_top.tif: Altitude raster dataset of the top of the Southern Nevada volcanic-rock aquifers. The altitude values are in meters reference to North American Vertical Datum of 1988 (NAVD88). This data was sourced from Sweetkind and others, 2011. 2. ra_57SRNVDV_bot.tif: Altitude raster dataset of the bottom of the Southern Nevada volcanic-rock aquifers. The altitude values are in meters reference to NAVD88. This data was sourced from Sweetkind and others, 2011. Depth raster files: 1. rd_57SRNVDV_top.tif: Depth raster dataset of the top of the Southern Nevada volcanic-rock aquifers. The depth values are in meters below land surface (NED, 100-meter). 2. rd_57SRNVDV_bot.tif: Depth raster dataset of the bottom of the Southern Nevada volcanic-rock aquifers. The depth values are in meters below land surface (NED, 100-meter).

The Roswell Basin aquifer system is located in southeastern New Mexico. It is composed of an alluvial aquifer and an underlying carbonate-rock aquifer. The aquifer covers an area of about 2,200 square miles and the alluvial aquifer covers about 1,200 square miles of the eastern half of this area. The alluvial aquifer primarily consists of Quaternary sediments and the carbonate-rock aquifer consists of the San Andres Limestone. Both aquifers offer highly productive groundwater wells that are extensively used for agricultural, industrial, and municipal use (HA 730-C). This product provides source data for the Roswell Basin aquifer system framework, including: Georeferenced images: 1. i_43RSWLBS_top.tif: Digitized figure of altitude contour lines representing the top of the Roswell Basin aquifer system. The original figure was from the Geohydrologic Framework of the Roswell Ground-water Basin report (Welder, 1983). Extent shapefiles: 1. p_43RSWLBS.shp: Polygon shapefile containing the areal extent of the Roswell Basin aquifer system. This shapefile was sourced from Roswell_AqExtent and was modified based off of (Welder, 1983). The extent file contains no aquifer subunits. Contour line shapefiles: 1. c_43RSWLBS_top.shp: Contour line dataset containing altitude values, in feet reference to National Geodetic Vertical Datum of 1929 (NGVD29), across the top of the Roswell Basin aquifer system. These data were used to create the ra_43RSWLBS_top.tif raster dataset. Altitude raster files: 1. ra_43RSWLBS_top.tif: Altitude raster dataset of the top of the Roswell Basin aquifer system. The altitude values are in meters reference to North American Vertical Datum of 1988 (NAVD88). This file was interpolated from the contour line dataset (Welder, 1983). 2. ra_43RSWLBS_bot.tif: Altitude raster dataset of the bottom of the Roswell Basin aquifer system. The altitude values are in meters reference to NAVD88. Depth raster files: 1. rd_43RSWLBS_top.tif: Depth raster dataset of the top of the Roswell Basin aquifer system. The depth values are in meters below land surface (NED, 100-meter). 2. rd_43RSWLBS_bot.tif: Depth raster dataset of the bottom of the Roswell Basin aquifer system. The depth values are in meters below land surface (NED, 100-meter).

The Roswell Basin aquifer system is located in southeastern New Mexico. It is composed of an alluvial aquifer and an underlying carbonate-rock aquifer. The aquifer covers an area of about 2,200 square miles and the alluvial aquifer covers about 1,200 square miles of the eastern half of this area. The alluvial aquifer primarily consists of Quaternary sediments and the carbonate-rock aquifer consists of the San Andres Limestone. Both aquifers offer highly productive groundwater wells that are extensively used for agricultural, industrial, and municipal use (HA 730-C). This product provides source data for the Roswell Basin aquifer system framework, including: Georeferenced images: 1. i_43RSWLBS_top.tif: Digitized figure of altitude contour lines representing the top of the Roswell Basin aquifer system. The original figure was from the Geohydrologic Framework of the Roswell Ground-water Basin report (Welder, 1983). Extent shapefiles: 1. p_43RSWLBS.shp: Polygon shapefile containing the areal extent of the Roswell Basin aquifer system. This shapefile was sourced from Roswell_AqExtent and was modified based off of (Welder, 1983). The extent file contains no aquifer subunits. Contour line shapefiles: 1. c_43RSWLBS_top.shp: Contour line dataset containing altitude values, in feet reference to National Geodetic Vertical Datum of 1929 (NGVD29), across the top of the Roswell Basin aquifer system. These data were used to create the ra_43RSWLBS_top.tif raster dataset. Altitude raster files: 1. ra_43RSWLBS_top.tif: Altitude raster dataset of the top of the Roswell Basin aquifer system. The altitude values are in meters reference to North American Vertical Datum of 1988 (NAVD88). This file was interpolated from the contour line dataset (Welder, 1983). 2. ra_43RSWLBS_bot.tif: Altitude raster dataset of the bottom of the Roswell Basin aquifer system. The altitude values are in meters reference to NAVD88. Depth raster files: 1. rd_43RSWLBS_top.tif: Depth raster dataset of the top of the Roswell Basin aquifer system. The depth values are in meters below land surface (NED, 100-meter). 2. rd_43RSWLBS_bot.tif: Depth raster dataset of the bottom of the Roswell Basin aquifer system. The depth values are in meters below land surface (NED, 100-meter).

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 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 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 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 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 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).