Quality assurance of water levels in the Mississippi River Valley alluvial aquifer in Louisiana from the Louisiana Department of Natural Resources' Strategic Online Natural Resources Information System (SONRIS)

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_que… (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).