Site data contained in the ScrIntrvls_AllSrcRefs_AllWellsRev.csv dataset define the top and bottom altitudes of well screens in 64,763 irrigation wells completed in the Mississippi River Valley alluvial aquifer (MRVA) that constitute a production zone in the Mississippi Alluvial Plain (MAP) extending across the midwestern and southern United States from Illinois to Louisiana. Each well entry contains an Enumerated Domain Value of the Attribute Label SrcRefNo to identify the state environmental agency that contributed to the database, and enumerated values are associated with specific state agencies by using the Enumerated Domain Value Definition. Screen-top and -bottom altitudes and land surface are referenced (corrected) to the National Elevation Dataset (NED) 10-meter digital elevation model (DEM; https://nationalmap.gov/elevation.html). The dataset identifies 50,103 screen-bottom altitudes and 50,457 screen-top altitudes that were used in subsequent geostatistical estimation after spatial analytics filtered out duplicate-coordinate wells, geographic and stratigraphic outliers, and incongruities of screen-top and -bottom altitudes compared with DEM land-surface altitude and the published digital surface of the bottom altitude of the MRVA (https://doi.org/10.3133/sim3426). Well entries are indexed in the dataset to identify use in four regional geostatistical models that collectively encompass the MAP extent and provide gridded estimates of screen-top and-bottom altitudes and estimation uncertainty (estimation variance) associated with each gridded altitude estimate. Digital surfaces of screen-top and -bottom estimates and estimation variances are represented as raster datasets that were converted to netCDF format and conform with the previously published National Hydrologic Grid (https://doi.org/10.5066/F7P84B24) at one-kilometer resolution. This dataset contains high-quality map images for gridded estimates of MRVA screen-top and -bottom altitude and for corresponding gridded estimation variances saved in the Tagged Image File (.tif) format.

Bottom altitudes of the Mississippi River Valley alluvial aquifer (MRVA) were compiled from interpretations of subsurface geophysical logs (log picks) at about 10,000 boreholes and wells located throughout the Mississippi Alluvial Plain (MAP) that were available from previous investigations. Five sources of the bottom altitude data are listed numerically in the Cross Reference section (below) and correspond with the Ref_code listed in the .shp dataset. Borehole geophysical data (log picks) were referenced (corrected) to the National Elevation Dataset (NED) 10-meter digital elevation model (DEM; https://nationalmap.gov/elevation.html). Log picks that required a DEM correction of less than 20 feet were retained for use in a subsequent geostatistical estimation of the MRVA bottom altitude, after additional filtering to remove duplicate log picks yielded a MRVA bottom-altitude dataset of 9,292 data points, described in this data release. Values of MRVA thickness were prepared by subtracting bottom altitudes from DEM values at the data locations. A second filtering of MRVA bottom-altitude data based on results of geostatistical analytical procedures and analysis of updated log picks in the Mississippi Delta region from Cross Reference 3 generated the 6,604-element dataset of MRVA bottom altitude and thickness described in this data release.

Bottom altitudes of the Mississippi River Valley alluvial aquifer (MRVA) were compiled from interpretations of subsurface geophysical logs (log picks) at about 10,000 boreholes and wells located throughout the Mississippi Alluvial Plain (MAP) that were available from previous investigations. Five sources of the bottom altitude data are listed numerically in the Cross Reference section (below) and correspond with the Ref_code listed in the .shp dataset. Borehole geophysical data (log picks) were referenced (corrected) to the National Elevation Dataset (NED) 10-meter digital elevation model (DEM; https://nationalmap.gov/elevation.html). Log picks that required a DEM correction of less than 20 feet were retained for use in a subsequent geostatistical estimation of the MRVA bottom altitude, after additional filtering to remove duplicate log picks yielded a MRVA bottom-altitude dataset of 9,292 data points, described in this data release. Values of MRVA thickness were prepared by subtracting bottom altitudes from DEM values at the data locations. A second filtering of MRVA bottom-altitude data based on results of geostatistical analytical procedures and analysis of updated log picks in the Mississippi Delta region from Cross Reference 3 generated the 6,604-element dataset of MRVA bottom altitude and thickness described in this data release.

The Mississippi River Valley alluvial aquifer (MRVA) in eastern Arkansas is a major source of groundwater for public, industrial, agricultural, and aquaculture uses. Estimated withdrawals from the MRVA increased from 1,063 million gallons per day in 1965 (Halberg and Stephens, 1966) to 7,252 million gallons per day in 2005 (Holland, 2007). Potentiometric-surface maps, which represent the altitude at which water would stand in tightly cased wells completed at any location within in the study area, are produced to track water level changes over time (Schrader, 2010). This dataset contains 19 collections of digitized potentiometric surfaces, represented as potentiometric contours and rasters derived from those contours, from the early 1900s to 2008, and is loosely confined to the Mississippi River Valley alluvial aquifer extents inside Arkansas.

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.

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 the contours, in feet, of the potentiometric-surface, spring 2018, Mississippi River Valley alluvial (MRVA) aquifer. The contours are referenced to the North American Vertical Datum of 1988 (NAVD 88). The contours were derived from most of the available groundwater-altitude data from wells and surface-water-altitude data from streamgages, measured in for spring 2018. The potentiometric contours ranged from 10 to 340 feet (3 to 104 meters) 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.

This dataset contains the contours, in feet, of the potentiometric-surface, spring 2018, Mississippi River Valley alluvial (MRVA) aquifer. The contours are referenced to the North American Vertical Datum of 1988 (NAVD 88). The contours were derived from most of the available groundwater-altitude data from wells and surface-water-altitude data from streamgages, measured in for spring 2018. The potentiometric contours ranged from 10 to 340 feet (3 to 104 meters) 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.

This dataset contains surface-water-altitude (SWA) data from streamgages that was used or considered to create a potentiometric-surface map for the Mississippi River Valley alluvial (MRVA) aquifer for spring 2018. The surface-water-altitude data was referenced to the North American Vertical Datum of 1988 (NAVD 88). The streamgages are measured continuously. The streamgage measurement that was used was from early April 2018 and is an estimate of the groundwater altitudes at the gage location. The resultant potentiometric-surface contours and raster represents the generalized central tendency for spring 2018, but it would not be useful for some purposes, such as for calibration of a groundwater-flow model for early April 2018 or for some local scale assessments.

This dataset contains surface-water-altitude (SWA) data from streamgages that was used or considered to create a potentiometric-surface map for the Mississippi River Valley alluvial (MRVA) aquifer for spring 2018. The surface-water-altitude data was referenced to the North American Vertical Datum of 1988 (NAVD 88). The streamgages are measured continuously. The streamgage measurement that was used was from early April 2018 and is an estimate of the groundwater altitudes at the gage location. The resultant potentiometric-surface contours and raster represents the generalized central tendency for spring 2018, but it would not be useful for some purposes, such as for calibration of a groundwater-flow model for early April 2018 or for some local scale assessments.