These data include groundwater-level data from 59 wells measured from July to August 2017. Measured groundwater data are also available from the USGS National Water Information System (U.S. Geological Survey, 2018) Well locations were selected from three sources: previously reported sites (Kresse and Hays, 2009), site reconnaissance, and driller’s logs obtained from the Arkansas Natural Resources Commission driller database. Reference: U.S. Geological Survey, 2018, USGS water data for the Nation: U.S. Geological Survey National Water Information System database, accessed 1 July 2017 at http://dx.doi.org/10.5066/F7P55KJN.

This dataset contains 50-ft contours for the Hot Springs shallowest unit of the Ouachita Mountains aquifer system potentiometric-surface map. The potentiometric-surface shows altitude at which the water level would have risen in tightly-cased wells and represents synoptic conditions during the summer of 2017. Contours were constructed from 59 water-level measurements measured in selected wells (locations in the well point dataset). Major streams and creeks were selected in the study area from the USGS National Hydrography Dataset (U.S. Geological Survey, 2017), and the spring point dataset with 18 spring altitudes calculated from 10-meter digital elevation model (DEM) data (U.S. Geological Survey, 2015; U.S. Geological Survey, 2016). After collecting, processing, and plotting the data, a potentiometric surface was generated using the interpolation method Topo to Raster in ArcMap 10.5 (Esri, 2017a). This tool is specifically designed for the creation of digital elevation models and imposes constraints that ensure a connected drainage structure and a correct representation of the surface from the provided contour data (Esri, 2017a). Once the raster surface was created, 50-ft contour interval were generated using Contour (Spatial Analyst), a spatial analyst tool (available through ArcGIS 3D Analyst toolbox) that creates a line-feature class of contours (isolines) from the raster surface (Esri, 2017b). The Topo to Raster and contouring done by ArcMap 10.5 is a rapid way to interpolate data, but computer programs do not account for hydrologic connections between groundwater and surface water. For this reason, some contours were manually adjusted based on topographical influence, a comparison with the potentiometric surface of Kresse and Hays (2009), and data-point water-level altitudes to more accurately represent the potentiometric surface. Select References: Esri, 2017a, How Topo to Raster works—Help | ArcGIS Desktop, accessed December 5, 2017, at ArcGIS Pro at http://pro.arcgis.com/en/pro-app/tool-reference/3d-analyst/how-topo-to-raster-works.htm. Esri, 2017b, Contour—Help | ArcGIS Desktop, accessed December 5, 2017, at ArcGIS Pro Raster Surface toolset at http://pro.arcgis.com/en/pro-app/tool-reference/3d-analyst/contour.htm. Kresse, T.M., and Hays, P.D., 2009, Geochemistry, Comparative Analysis, and Physical and Chemical Characteristics of the Thermal Waters East of Hot Springs National Park, Arkansas, 2006-09: U.S. Geological Survey 2009–5263, 48 p., accessed November 28, 2017, at https://pubs.usgs.gov/sir/2009/5263/. U.S. Geological Survey, 2015, USGS NED 1 arc-second n35w094 1 x 1 degree ArcGrid 2015, accessed December 5, 2017, at The National Map: Elevation at https://nationalmap.gov/elevation.html. U.S. Geological Survey, 2016, USGS NED 1 arc-second n35w093 1 x 1 degree ArcGrid 2016, accessed December 5, 2017, at The National Map: Elevation at https://nationalmap.gov/elevation.html.

This dataset contains 50-ft contours for the Hot Springs shallowest unit of the Ouachita Mountains aquifer system potentiometric-surface map. The potentiometric-surface shows altitude at which the water level would have risen in tightly-cased wells and represents synoptic conditions during the summer of 2017. Contours were constructed from 59 water-level measurements measured in selected wells (locations in the well point dataset). Major streams and creeks were selected in the study area from the USGS National Hydrography Dataset (U.S. Geological Survey, 2017), and the spring point dataset with 18 spring altitudes calculated from 10-meter digital elevation model (DEM) data (U.S. Geological Survey, 2015; U.S. Geological Survey, 2016). After collecting, processing, and plotting the data, a potentiometric surface was generated using the interpolation method Topo to Raster in ArcMap 10.5 (Esri, 2017a). This tool is specifically designed for the creation of digital elevation models and imposes constraints that ensure a connected drainage structure and a correct representation of the surface from the provided contour data (Esri, 2017a). Once the raster surface was created, 50-ft contour interval were generated using Contour (Spatial Analyst), a spatial analyst tool (available through ArcGIS 3D Analyst toolbox) that creates a line-feature class of contours (isolines) from the raster surface (Esri, 2017b). The Topo to Raster and contouring done by ArcMap 10.5 is a rapid way to interpolate data, but computer programs do not account for hydrologic connections between groundwater and surface water. For this reason, some contours were manually adjusted based on topographical influence, a comparison with the potentiometric surface of Kresse and Hays (2009), and data-point water-level altitudes to more accurately represent the potentiometric surface. Select References: Esri, 2017a, How Topo to Raster works—Help | ArcGIS Desktop, accessed December 5, 2017, at ArcGIS Pro at http://pro.arcgis.com/en/pro-app/tool-reference/3d-analyst/how-topo-to-raster-works.htm. Esri, 2017b, Contour—Help | ArcGIS Desktop, accessed December 5, 2017, at ArcGIS Pro Raster Surface toolset at http://pro.arcgis.com/en/pro-app/tool-reference/3d-analyst/contour.htm. Kresse, T.M., and Hays, P.D., 2009, Geochemistry, Comparative Analysis, and Physical and Chemical Characteristics of the Thermal Waters East of Hot Springs National Park, Arkansas, 2006-09: U.S. Geological Survey 2009–5263, 48 p., accessed November 28, 2017, at https://pubs.usgs.gov/sir/2009/5263/. U.S. Geological Survey, 2015, USGS NED 1 arc-second n35w094 1 x 1 degree ArcGrid 2015, accessed December 5, 2017, at The National Map: Elevation at https://nationalmap.gov/elevation.html. U.S. Geological Survey, 2016, USGS NED 1 arc-second n35w093 1 x 1 degree ArcGrid 2016, accessed December 5, 2017, at The National Map: Elevation at https://nationalmap.gov/elevation.html.

This dataset consists of altitudes of 18 springs located throughout the study area which were used in construction of the potentiometric-surface map. Springs were selected from the previously published report by Kresse and Hays (2009), and site reconnaissance. Surface-water features and springs represent the intersection of the groundwater-table with land surface. Spring altitudes were calculated from 10-meter digital elevation model (DEM) data (U.S. Geological Survey, 2015; U.S. Geological Survey, 2016) . References: Kresse, T.M., and Hays, P.D., 2009, Geochemistry, Comparative Analysis, and Physical and Chemical Characteristics of the Thermal Waters East of Hot Springs National Park, Arkansas, 2006-09: U.S. Geological Survey 2009–5263, 48 p., accessed November 28, 2017, at https://pubs.usgs.gov/sir/2009/5263/. U.S. Geological Survey, 2015, USGS NED 1 arc-second n35w094 1 x 1 degree ArcGrid 2015, accessed December 5, 2017, at The National Map: Elevation at https://nationalmap.gov/elevation.html. U.S. Geological Survey, 2016, USGS NED 1 arc-second n35w093 1 x 1 degree ArcGrid 2016, accessed December 5, 2017, at The National Map: Elevation at https://nationalmap.gov/elevation.html.

This dataset consists of altitudes of 18 springs located throughout the study area which were used in construction of the potentiometric-surface map. Springs were selected from the previously published report by Kresse and Hays (2009), and site reconnaissance. Surface-water features and springs represent the intersection of the groundwater-table with land surface. Spring altitudes were calculated from 10-meter digital elevation model (DEM) data (U.S. Geological Survey, 2015; U.S. Geological Survey, 2016) . References: Kresse, T.M., and Hays, P.D., 2009, Geochemistry, Comparative Analysis, and Physical and Chemical Characteristics of the Thermal Waters East of Hot Springs National Park, Arkansas, 2006-09: U.S. Geological Survey 2009–5263, 48 p., accessed November 28, 2017, at https://pubs.usgs.gov/sir/2009/5263/. U.S. Geological Survey, 2015, USGS NED 1 arc-second n35w094 1 x 1 degree ArcGrid 2015, accessed December 5, 2017, at The National Map: Elevation at https://nationalmap.gov/elevation.html. U.S. Geological Survey, 2016, USGS NED 1 arc-second n35w093 1 x 1 degree ArcGrid 2016, accessed December 5, 2017, at The National Map: Elevation at https://nationalmap.gov/elevation.html.

Groundwater potentiometric-surface contours for spring 2022 (April 4 to 8, 2022) and autumn 2022 (October 30 to November 4, 2022) were created for the alluvial aquifer in Big Lost River Valley. The well numbers and station names used to create the potentiometric-surface contours and groundwater-level change maps are provided in this data release. The location, depth to water, and potentiometric-surface altitude for these wells can be accessed on USGS National Water Information System (NWIS) or Idaho Department of Water Resources (IDWR) groundwater portal. The interpreted 20-foot contours of the potentiometric-surface are also provided in this data release. The contours are referenced to the North American Vertical Datum of 1988 (NAVD 88). The potentiometric-surface contours are divided into three water-bearing units - shallow, intermediate, and deep - based on well depth, potentiometric-surface altitude, and hydrogeologic unit. The intermediate and deep units were only identified in the southern portion of the valley near Arco, Idaho. The potentiometric-surface contours ranged from 4,900 to 6,660 feet above NAVD 88. The groundwater-level change at well sites from spring to autumn 2022, spring to autumn 1968, spring 1968 to spring 2022, spring 1991 to spring 2022, and spring 1968 to spring 1991 were calculated and are provided in a shapefile.

Groundwater potentiometric-surface contours for spring 2022 (April 4 to 8, 2022) and autumn 2022 (October 30 to November 4, 2022) were created for the alluvial aquifer in Big Lost River Valley. The well numbers and station names used to create the potentiometric-surface contours and groundwater-level change maps are provided in this data release. The location, depth to water, and potentiometric-surface altitude for these wells can be accessed on USGS National Water Information System (NWIS) or Idaho Department of Water Resources (IDWR) groundwater portal. The interpreted 20-foot contours of the potentiometric-surface are also provided in this data release. The contours are referenced to the North American Vertical Datum of 1988 (NAVD 88). The potentiometric-surface contours are divided into three water-bearing units - shallow, intermediate, and deep - based on well depth, potentiometric-surface altitude, and hydrogeologic unit. The intermediate and deep units were only identified in the southern portion of the valley near Arco, Idaho. The potentiometric-surface contours ranged from 4,900 to 6,660 feet above NAVD 88. The groundwater-level change at well sites from spring to autumn 2022, spring to autumn 1968, spring 1968 to spring 2022, spring 1991 to spring 2022, and spring 1968 to spring 1991 were calculated and are provided in a shapefile.

This dataset contains groundwater-altitude (GWA) data from wells that were used or considered (indicated by the field USE_2020) to create a potentiometric-surface map for the Mississippi River Valley alluvial aquifer (MRVA) for spring 2020. The GWA data was referenced to the North American Vertical Datum of 1988 (NAVD 88). Most of the wells were measured annually, but some wells were measured more than one time in a year and a small number of wells were measured continuously. GWA data were from wells measured in spring 2020. To best reflect hydrologic conditions in the MRVA, the GWA data used to create the 2020 potentiometric surface would be measured in a short-time frame of days or a week and there would be available data (for example from sets of wells with short-screen (about 5 to 10 feet or 1.5 to 3 meters) installed near the top, in the middle, and near the bottom of the aquifer) to indicate vertical flow components. However, most wells screened in the MRVA were measured before the potentiometric-surface map of the MRVA was planned and therefore the timing of each well's measurement(s) was determined by the needs and schedules of the entities doing the measurements. Also, many of the measured wells had longer screens (from greater than 10 feet or 3 meters and covering a substantial part of the aquifer thickness), therefore their water-level measurements represent an average head in the aquifer for that location. The resultant potentiometric-surface contours and raster represents the generalized central tendency for spring 2020, but it would not be useful for some purposes, such as for calibration of a groundwater-flow model for early April 2020 or for some local scale assessments.

A potentiometric surface map for spring 2016 was created for the Mississippi River Valley alluvial (MRVA) aquifer, which was referenced to the North American Vertical Datum of 1988 (NAVD 88), using most of the available groundwater-altitude data from wells and surface-water-altitude data from streamgages. Most of the wells were measured annually or one time, after installation, but some wells were measured more than one time in a year and a small number of wells were measured continually. Streamgages were typically operated continuously. The potentiometric surface map for 2016 was created as part of the U.S. Geological Survey (USGS) Water Availability and Use Science Program to support investigations that characterize the MRVA aquifer. The potentiometric contours ranged from 10 feet to 340 feet above NAVD 88. The regional direction of groundwater flow was generally towards the south-southwest, except in areas of groundwater-altitude depressions, where groundwater flows into the depressions, and near rivers, where groundwater flow generally parallels the flow in the rivers. There are large depressions in the potentiometric surface in the lower half of the Cache region and in most of the Grand Prairie and Delta regions.

This dataset contains groundwater-altitude (GWA) data from wells that were used or considered (indicated by the field USE_2020) to create a potentiometric-surface map for the Mississippi River Valley alluvial aquifer (MRVA) for spring 2020. The GWA data was referenced to the North American Vertical Datum of 1988 (NAVD 88). Most of the wells were measured annually, but some wells were measured more than one time in a year and a small number of wells were measured continuously. GWA data were from wells measured in spring 2020. To best reflect hydrologic conditions in the MRVA, the GWA data used to create the 2020 potentiometric surface would be measured in a short-time frame of days or a week and there would be available data (for example from sets of wells with short-screen (about 5 to 10 feet or 1.5 to 3 meters) installed near the top, in the middle, and near the bottom of the aquifer) to indicate vertical flow components. However, most wells screened in the MRVA were measured before the potentiometric-surface map of the MRVA was planned and therefore the timing of each well's measurement(s) was determined by the needs and schedules of the entities doing the measurements. Also, many of the measured wells had longer screens (from greater than 10 feet or 3 meters and covering a substantial part of the aquifer thickness), therefore their water-level measurements represent an average head in the aquifer for that location. The resultant potentiometric-surface contours and raster represents the generalized central tendency for spring 2020, but it would not be useful for some purposes, such as for calibration of a groundwater-flow model for early April 2020 or for some local scale assessments.