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.

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 is the raster, in feet, of the potentiometric-surface map, spring 2018, Mississippi River Valley alluvial (MRVA) aquifer. The raster cell size is 1,000 meters; the raster altitude data was referenced to the North American Vertical Datum of 1988 (NAVD 88). The raster was interpolated using (1) most of the available groundwater-altitude data from wells and surface-water-altitude data from streamgages, and (2) potentiometric-surface contours.

This dataset is the raster, in meters, of the potentiometric-surface map, spring 2018, Mississippi River Valley alluvial (MRVA) aquifer. The raster cell size is 1,000 meters; the raster was referenced to the North American Vertical Datum of 1988 (NAVD 88). The raster, in feet, was interpolated using most of the available groundwater-altitude data from wells, surface-water-altitude data from streamgages, and the potentiometric contours. Then the raster altitude data was converted to meters.

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.

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.