This data release provides several data files representing groundwater levels reported through driller's reports for the State of Louisiana Department of Natural Resources (Louisiana Department of Natural Resources, 2023) within or near the Mississippi Alluvial Plain (MAP) and (or) associated with the Mississippi River Valley alluvial aquifer (MRVA). First, a retrieval of data from the State of Louisiana was made and manual preparatory filtering including complete information of location, date, water level (depth below land surface) and water level altitude in feet, and general association with the MAP or MRVA. Further manual and digitally-assisted inspection was made to confirm that the data were not already within the U.S. Geological Survey (USGS) National Water Information System (NWIS) (U.S. Geological Survey, 2023). The agency code for the water levels has been assigned "LA018" (Louisiana Department of Natural Resources) in accordance with the https://help.waterdata.usgs.gov/codes-and-parameters/code/agency_cd_query?fmt=html (accessed February 28, 2023). Use of the LA018 agency code is consistent with historical and current USGS storage practices in NWIS when in collaboration with the State of Louisiana. This first data file is titled "LADNR_drillers_working.csv" (6,374 records). Second, that data file was processed through data structure conversion software (infoGW2visGWDB) (Asquith and Seanor, 2019) and in particular removal of well locations plotting outside the MAP boundary (Painter and Westerman, 2023) was made. The resultant but transient data structure of 4,855 of the original 6,374 records was given over to quality-control and assurance using statistical modeling (visGWDBmrva software) (Asquith and others, 2019, 2020). The statistical analyses result in formation of a regional statistical time series models using generalized additive models (GAMs) and support vector machines (SVMs). Some 18 records by horizontal position having a missing altitude of the bottom of the MRVA and zero records having water-level altitudes below the bottom of the MRVA when digitally working with the Torak and Painter (2019) surface of the MRVA bottom. These 18 records are retained through the workflow described herein to avoid potential scientific interpretation of hydrogeologic framework. In summary, for each of the 4,855 well-water-level records (or rather in detail, each unique well identifier), the visGWDBmrva software isolated all water levels for the MAP/MRVA from USGS (2023) within 16 kilometers radial distance. This means that the driller's dataset is being internally compared to itself and USGS MAP/MRVA data. The visGWDBmrva software computed a "pseudo water level" from a blending of GAM and SVM model predictions for the date of the driller's recorded water level. These computations are all created on-the-fly. A residual was computed from the pseudo water level (as altitude) to that water-level altitude reported for the well-water-level record of the driller's dataset. These statistical results are listed the file titled "LADNR_retained_levels.csv" (4,744 records) for which records were retained LADNR_drillers_working.csv if the absolute value of the residual of the well-water-level record and the pseudo water level was less than or equal to 20 feet. This threshold resulted from exploratory review of the statistical computations and is consistent with Smith and others (2020) and Weber and others (2021) for a similar driller's reported dataset for the Missouri part of the MAP/MRVA. The results listed in file LADNR_retained_levels.csv are deemed especially suitable for greater statistical modeling of groundwater levels in the MRVA (Asquith and Killian, 2022).

This dataset contains the final water-level records (334) that met all threshold criteria and had an absolute residual (ABS_PSEUDO_LEV) of less than 20 feet. The threshold of 20 feet was selected based on water-level changes of the U.S. Geological Survey groundwater site 363551090152801 Qulin, in the Mississippi River Valley alluvial aquifer. This final dataset is considered a best representation of the true water-levels in the aquifer.

This dataset contains the final water-level records (334) that met all threshold criteria and had an absolute residual (ABS_PSEUDO_LEV) of less than 20 feet. The threshold of 20 feet was selected based on water-level changes of the U.S. Geological Survey groundwater site 363551090152801 Qulin, in the Mississippi River Valley alluvial aquifer. This final dataset is considered a best representation of the true water-levels in the aquifer.

An objective review (Asquith and others, 2018 and 2020) of the distribution of the first two significant figures of a water-level measurement (depth below land surface) was done on the 10,295 measurements (one per well) that met the threshold criteria. The purpose of this review was to ascertain the degree to which substantial rounding of values might exist in the dataset. It was evident that the dataset has a large number of values rounded to the nearest integer foot with a tendency for more rounding towards even integers. For values between 10 and 99 feet, there is a large number of values rounded to the even 10 feet and for values less than about 35 feet, there are an excessive number of values rounded the nearest. There are also numerous values of 12 and 14. This suggests that considerable estimation or rounding of water levels have been made probably by use of apparatus other than graduate tapes. Systematic review of original data sources is not possible and insufficient metadata exist for a manual of each value in the data set. However, the database is large and offers an opportunity for data mining and machine learning to foster further review. A large, objective, technically-demanding, and rigorous spatial-temporal review of the water-level data, expressed in altitude, was made for the 10,295 water level records comprising this data release.

An objective review (Asquith and others, 2018 and 2020) of the distribution of the first two significant figures of a water-level measurement (depth below land surface) was done on the 10,295 measurements (one per well) that met the threshold criteria. The purpose of this review was to ascertain the degree to which substantial rounding of values might exist in the dataset. It was evident that the dataset has a large number of values rounded to the nearest integer foot with a tendency for more rounding towards even integers. For values between 10 and 99 feet, there is a large number of values rounded to the even 10 feet and for values less than about 35 feet, there are an excessive number of values rounded the nearest. There are also numerous values of 12 and 14. This suggests that considerable estimation or rounding of water levels have been made probably by use of apparatus other than graduate tapes. Systematic review of original data sources is not possible and insufficient metadata exist for a manual of each value in the data set. However, the database is large and offers an opportunity for data mining and machine learning to foster further review. A large, objective, technically-demanding, and rigorous spatial-temporal review of the water-level data, expressed in altitude, was made for the 10,295 water level records comprising this data release.

A potentiometric-surface map represents the altitude at which water would stand in tightly cased wells completed at any location within the study area aquifer. Using the altitude of water levels measured in the study area, the potentiometric-surface map depicts points of equal altitude with contours denoting a given water-level altitude calculated by subtracting the water level measured from the land-surface elevation (National Geodetic Vertical Datum of 1929). The contour lines were created using computer-based program ArcGIS with an interval of 10 feet. The direction of water flow from areas of high elevation to low elevation can be interpreted using potentiometric-surface maps and areas of decreased groundwater levels can be identified. The 2014 potentiometric-surface map shows ten total cones of depressions: two large depressions, five small depressions, and three areas of decreased water levels. As with the 2010 potentiometric-surface map, one large depression begins in southeastern Arkansas County, near the Arkansas and Desha County line, and extends north into Prairie County, west into Lonoke County, and east into the western-most part of Monroe County. Even though the center of the depression had deepened in 2010, the area of the cone in Arkansas County within the southeastern half of the depression had not expanded horizontally. The analysis of the 2014 potentiometric-surface map suggests no horizontal expansion in this area. The additional GIS shapefiles were used to depicts the western extent of the Mississippi River alluvial aquifer in eastern Arkansas on plates 1, 2, and 3 in Rodgers and Whaling (2020).

A potentiometric-surface map represents the altitude at which water would stand in tightly cased wells completed at any location within the study area aquifer. Using the altitude of water levels measured in the study area, the potentiometric-surface map depicts points of equal altitude with contours denoting a given water-level altitude calculated by subtracting the water level measured from the land-surface elevation (National Geodetic Vertical Datum of 1929). The contour lines were created using computer-based program ArcGIS with an interval of 10 feet. The direction of water flow from areas of high elevation to low elevation can be interpreted using potentiometric-surface maps and areas of decreased groundwater levels can be identified. The 2014 potentiometric-surface map shows ten total cones of depressions: two large depressions, five small depressions, and three areas of decreased water levels. As with the 2010 potentiometric-surface map, one large depression begins in southeastern Arkansas County, near the Arkansas and Desha County line, and extends north into Prairie County, west into Lonoke County, and east into the western-most part of Monroe County. Even though the center of the depression had deepened in 2010, the area of the cone in Arkansas County within the southeastern half of the depression had not expanded horizontally. The analysis of the 2014 potentiometric-surface map suggests no horizontal expansion in this area. The additional GIS shapefiles were used to depicts the western extent of the Mississippi River alluvial aquifer in eastern Arkansas on plates 1, 2, and 3 in Rodgers and Whaling (2020).

A combination of discrete and daily-aligned groundwater levels for the Mississippi River Valley alluvial aquifer clipped to the Mississippi Alluvial Plain, as defined by Painter and Westerman (2018), with corresponding metadata are based on processing of U.S. Geological Survey National Water Information System (NWIS) (U.S. Geological Survey, 2020) data. The processing was made after retrieval using aggregation and filtering through the infoGW2visGWDB software (Asquith and Seanor, 2019). The nomenclature GWmaster mimics that of the output from infoGW2visGWDB. Two separate data retrievals for NWIS were made. First, the discrete data were retrieved, and second, continuous records from recorder sites with daily-mean or other daily statistics codes were retrieved. Each dataset was separately passed through the infoGW2visGWDB software to create a "GWmaster discrete" and "GWmaster continuous" and these tables were combined and then sorted on the site identifier and date to form the data products described herein. A sweep through the combined dataset (the "database") was made to isolate duplicate observations, or observations for the same well and on the same day. If a discrete value was present, it was retained as authoritative for the day and in descending order of priority daily-mean, daily-maximum, and daily minimum. Therefore, only a single record for a well and day are present in the dataset. The duplicate search removed 876 records and 31 wells were involved; in total, this is about 0.3 percent of the database. References: Asquith, W.H., Seanor, R.C., 2019, infoGW2visGWDB—An R groundwater data-processing utility for manipulating, checking the veracity, and converting an "infoGW" object to the "GWmaster" object for the visGWDB software with demonstration for the Mississippi River Valley alluvial aquifer: U.S. Geological Survey software release, Reston, Va., https://doi.org/10.5066/P9MK0B6L. Painter, J.A., and Westerman, D.A., 2018. Mississippi Alluvial Plain extent, November 2017: U.S. Geological Survey data release, https://doi.org/10.5066/F70R9NMJ. U.S. Geological Survey, 2020, USGS water data for the Nation: U.S. Geological Survey National Water Information System database, accessed April 2, 2020, at https://doi.org/10.5066/F7P55KJN.

A combination of discrete and daily-aligned groundwater levels for the Mississippi River Valley alluvial aquifer clipped to the Mississippi Alluvial Plain, as defined by Painter and Westerman (2018), with corresponding metadata are based on processing of U.S. Geological Survey National Water Information System (NWIS) (U.S. Geological Survey, 2020) data. The processing was made after retrieval using aggregation and filtering through the infoGW2visGWDB software (Asquith and Seanor, 2019). The nomenclature GWmaster mimics that of the output from infoGW2visGWDB. Two separate data retrievals for NWIS were made. First, the discrete data were retrieved, and second, continuous records from recorder sites with daily-mean or other daily statistics codes were retrieved. Each dataset was separately passed through the infoGW2visGWDB software to create a "GWmaster discrete" and "GWmaster continuous" and these tables were combined and then sorted on the site identifier and date to form the data products described herein. A sweep through the combined dataset (the "database") was made to isolate duplicate observations, or observations for the same well and on the same day. If a discrete value was present, it was retained as authoritative for the day and in descending order of priority daily-mean, daily-maximum, and daily minimum. Therefore, only a single record for a well and day are present in the dataset. The duplicate search removed 876 records and 31 wells were involved; in total, this is about 0.3 percent of the database. References: Asquith, W.H., Seanor, R.C., 2019, infoGW2visGWDB—An R groundwater data-processing utility for manipulating, checking the veracity, and converting an "infoGW" object to the "GWmaster" object for the visGWDB software with demonstration for the Mississippi River Valley alluvial aquifer: U.S. Geological Survey software release, Reston, Va., https://doi.org/10.5066/P9MK0B6L. Painter, J.A., and Westerman, D.A., 2018. Mississippi Alluvial Plain extent, November 2017: U.S. Geological Survey data release, https://doi.org/10.5066/F70R9NMJ. U.S. Geological Survey, 2020, USGS water data for the Nation: U.S. Geological Survey National Water Information System database, accessed April 2, 2020, at https://doi.org/10.5066/F7P55KJN.

Groundwater is a vital resource to the Mississippi embayment region of the central United States. Regional and integrated assessments of water availability that link physical flow models and water quality in principal aquifer systems provide context for the long-term availability of these water resources. An innovative approach using machine learning was employed to predict groundwater pH across drinking water aquifers of the Mississippi embayment. The region includes two principal regional aquifer systems; the Mississippi River Valley alluvial (MRVA) aquifer and the Mississippi embayment aquifer system that includes several regional aquifers and confining units. Based on the distribution of groundwater use for drinking water, the modeling effort was focused on the MRVA, Middle Claiborne aquifer (MCAQ), and Lower Claiborne aquifer (LCAQ)of the Mississippi embayment aquifer system. Boosted regression tree (BRT) models (Elith and others, 2008; Kuhn and Johnson, 2013) were used to predict pH to 1-km raster grid cells of the National Hydrologic Grid (Clark and others, 2018). Predictions were made for 7 aquifer layers (1 MRVA, 4 MCAQ, 2 LCAQ) following the hydrogeologic framework used in a regional groundwater flow model (Hart and others, 2008). Explanatory variables for the BRT models included attributes associated with well position and construction, surficial variables, and variables extracted from a MODFLOW groundwater flow model for the MISE (Haugh and others, 2020a,b). For a full description of modeling workflow see Knierim and others (2020).