The Mississippi River Valley alluvial aquifer (“alluvial aquifer”) is one of the most extensively developed aquifers in the United States. The alluvial aquifer is present at the land surface in parts of southeastern Missouri, northeastern Louisiana, western Mississippi, western Tennessee and Kentucky near the Mississippi River, and throughout eastern Arkansas. Historical (1940–2006) and recent (2019–20) aquifer-test datasets were compiled to model transmissivity and hydraulic conductivity of the alluvial aquifer from recent (2018–19) airborne electromagnetic (AEM) survey data. This data release contains the aquifer-test and geophysical data along with computer codes written in Matlab version R2014a syntax used to process the data as described in the corresponding journal article (Ikard and others, 2022). The computer codes were designed to use the datasets contained in comma-separated values (.csv) and ASCII text (.txt) files to: (1) calculate the longitudinal conductance, transverse resistance, and mean electric resistivity frameworks of the alluvial aquifer to depths of 125 meters within the Mississippi Alluvial Plain (MAP) physiographic province from the electric resistivity framework mapped by frequency-domain airborne electromagnetic (AEM) induction surveying along 16,816 line-kilometers (km) of flight path covering 95,000 square-kilometers (km2) of the MAP, (2) correlate the mean electric resistivity at discrete points within the MAP to a database of 160 spatially distributed historical values of alluvial-aquifer transmissivity, quantified by aquifer tests performed in the MAP between 1940 and 2006, and (3) apply user-defined log-linear electric–hydraulic (e–h) relations, defined from the correlation data produced in (2), to 2,364 line-kilometers of separate high-resolution AEM resistivity data covering the 1,000 km2 Shellmound, Mississippi study area (“Shellmound grid”) to calculate alluvial-aquifer transmissivity and hydraulic conductivity where aquifer test data are sparse. The datasets contained herein were extracted from larger parent datasets that are published in a series of U.S. Geological Survey data releases and Scientific Investigation Reports to support the Hydrogeologic Framework component of the MAP Regional Water Availability Study, and citations and web-links to each parent dataset are provided in the metadata record.

During the spring and summer of 2020, the U.S. Geological Survey, Lower Mississippi – Gulf Water Science Center, conducted single well slug tests on selected wells within the Mississippi Alluvial Plain of Arkansas and Mississippi to estimate hydraulic conductivity (K) and transmissivity (T) values for the aquifers in which the wells are screened. A total of 324 test were conducted on 48 wells. The computer software AQTESOLV for Windows (Duffield, 2007) was used to interpretate the slug test data to estimate K and T values. Mean estimates of K for the 44 wells completed in the Mississippi River Valley alluvial aquifer ranged from 3 to 401 feet per day (ft/day) and mean estimates of T ranged from 285 to 80,559 square feet per day (ft2/day). Mean estimates of K for the 4 wells completed in the Sparta Sand or 500-foot Sand (Memphis Aquifer) that make up part of the middle Claiborne aquifer of the Mississippi embayment aquifer system ranged from 0.14 to 183 ft/day and mean estimates of T ranged from 55 to 67,913 ft2/day. This Data Release contains the following data and supporting metadata: 1. A PDF document with calibration information for the mechanical slugs used for testing. 2. A zipped file of the 48-site files folders containing: 1. The site’s slug test field form (pdf). 2. Digital images of the site (jpg). 3. Water-level pressure transducer log files (csv), 4. Excel files(s) of transducer data with Time vs. Water Depth plots and the selected Time – Displacement data used for analysis. 5. The AQTESOLV solution report files (aqt) for each slug test. 3. A summary data file in two formats (csv & GIS shape file) including the following information for each site: 1. Site information [site name, agency code, USGS National Water Information System (NWIS) site number] 2. Location information (latitude, longitude, state, county). 3. Well construction information [well depth and diameter, casing diameter, top and bottom of opening (screen), and opening (screen) length]. 4. Aquifer information (local and national aquifer codes, and aquifer thickness). 5. Slug test information (test date and static water-level). 6. Estimates information (minimum, mean, median, and maximum K and T values and the solution method). 4. An equipment documentation file (csv) listing the water-level tape, transducer, and slug used at each site. 5. A water-level documentation file (csv) listing the before and after testing water-level measurements for each site. 6. A model input file (csv) listing the values input into the model for each test. 7. A model solutions file (csv) listing both the “Visual” and “Auto” match solution estimates for the slug tests at each site. Additional information, including discussions of the hydrogeologic setting, well descriptions, slug testing and analysis methods, and a summary of the slug test results are available in the Open File Report associated with this Data Release (Pugh, 2021). This dataset was collected and analyzed as part of the U.S. Geological Survey, Mississippi Alluvial Plain Regional Water-Availability Study.

During the spring and summer of 2020, the U.S. Geological Survey, Lower Mississippi – Gulf Water Science Center, conducted single well slug tests on selected wells within the Mississippi Alluvial Plain of Arkansas and Mississippi to estimate hydraulic conductivity (K) and transmissivity (T) values for the aquifers in which the wells are screened. A total of 324 test were conducted on 48 wells. The computer software AQTESOLV for Windows (Duffield, 2007) was used to interpretate the slug test data to estimate K and T values. Mean estimates of K for the 44 wells completed in the Mississippi River Valley alluvial aquifer ranged from 3 to 401 feet per day (ft/day) and mean estimates of T ranged from 285 to 80,559 square feet per day (ft2/day). Mean estimates of K for the 4 wells completed in the Sparta Sand or 500-foot Sand (Memphis Aquifer) that make up part of the middle Claiborne aquifer of the Mississippi embayment aquifer system ranged from 0.14 to 183 ft/day and mean estimates of T ranged from 55 to 67,913 ft2/day. This Data Release contains the following data and supporting metadata: 1. A PDF document with calibration information for the mechanical slugs used for testing. 2. A zipped file of the 48-site files folders containing: 1. The site’s slug test field form (pdf). 2. Digital images of the site (jpg). 3. Water-level pressure transducer log files (csv), 4. Excel files(s) of transducer data with Time vs. Water Depth plots and the selected Time – Displacement data used for analysis. 5. The AQTESOLV solution report files (aqt) for each slug test. 3. A summary data file in two formats (csv & GIS shape file) including the following information for each site: 1. Site information [site name, agency code, USGS National Water Information System (NWIS) site number] 2. Location information (latitude, longitude, state, county). 3. Well construction information [well depth and diameter, casing diameter, top and bottom of opening (screen), and opening (screen) length]. 4. Aquifer information (local and national aquifer codes, and aquifer thickness). 5. Slug test information (test date and static water-level). 6. Estimates information (minimum, mean, median, and maximum K and T values and the solution method). 4. An equipment documentation file (csv) listing the water-level tape, transducer, and slug used at each site. 5. A water-level documentation file (csv) listing the before and after testing water-level measurements for each site. 6. A model input file (csv) listing the values input into the model for each test. 7. A model solutions file (csv) listing both the “Visual” and “Auto” match solution estimates for the slug tests at each site. Additional information, including discussions of the hydrogeologic setting, well descriptions, slug testing and analysis methods, and a summary of the slug test results are available in the Open File Report associated with this Data Release (Pugh, 2021). This dataset was collected and analyzed as part of the U.S. Geological Survey, Mississippi Alluvial Plain Regional Water-Availability Study.

Since the 1940's, hydrologists have used aquifer tests to estimate the hydrogeologic properties near test wells. Results from these tests are recorded in various files, databases, reports and scientific publications. The U.S. Geological Survey (USGS), Lower Mississippi-Gulf Water Science Center (LMG) is aggregating all aquifer test results from Alabama, Arkansas, Louisiana, Mississippi and Tennessee into a single dataset that is publicly available in a machine-readable format. This dataset contains information and results from 2,245 aquifer tests compiled for aquifers located in the LMG-Hydrogeologic Aquifer Test Dataset - December 2020. Descriptive statistics for the December 2020 dataset are presented in Table 1 (below) and in the Summary_Readme.pdf. Additionally, this dataset contains 6 attribute tables (.txt files) with additional information for various fields, a zip file containing the geospatial data, and the companion attribute table as a .txt file. THE LMG-HYDROGEOLOGIC AQUIFER TEST DATASET – DECEMBER 2020 IS AVAILABLE IN TWO FORMATS: 1) a tab delimited text (.txt) UTF-8 file and 2) an ESRI GIS point shapefile. FIELDS INCLUDED IN THE LMG-HYDROGEOLOGIC AQUIFER TEST DATASET – DECEMBER 2020: [a complete list of field names, their definitions and units are listed in the Summary_Readme.pdf file] Location data: USGS site identification number, local identification name, Public Land Survey System number, latitude, longitude, State and county. Well construction data: Construction date, well depth, Diameter of well, diameter of casing, depth to top of opening (screen) interval, depth to bottom of opening interval and length of the open interval. Aquifer data: Local aquifer name and code, national aquifer name and code, top of aquifer (altitude), bottom of aquifer, and thickness of aquifer. Groundwater test data: Test date, yield/discharge, length of time associated with yield, static water-level in feet below land surface, production water-level in feet below land surface associated with yield, drawdown associated with yield. Hydrogeologic data: Specific capacity, transmissivity, horizontal Conductivity, vertical conductivity, permeability and storage coefficient. Ancillary data: Method of test analysis and data source reference. DESCRIPTIONS OF ATTACHED FILES: Summary_Readme.pdf: a Portable Document Format (PDF) file with field names, definitions and units for the aquifer test dataset and the associated attribute tables. This file also contains summary statistics for aquifer test compiled through December 2020. LMG-HydrogeologicAqfrTestDataset_Dec2020.txt: a tab-delimited, UTF-8 text file of the attribute table associated with the LMG-HydrogeologicTestData_Dec2020 geospatial dataset. AtbtTbl_AqfrCd_Readme.txt: an UTF-8 text file containing information from the National Water Information System: Help System web page about USGS groundwater codes. (accessed December 4, 2019 at https://help.waterdata.usgs.gov/codes-and-parameters) AtbtTbl_FipsGeographyCodes.txt: a tab-delimited, UTF-8 text file of FIPS (Federal Information Processing Standards) codes, uniquely identifying States, counties and county equivalents in the United States. Note: to reduce the size of this file, city codes were removed. (accessed January 8, 2020 at https://www.census.gov/geographies/reference-files/2017/demo/popest/2017-fips.html). AtbtTbl_LocalAqfrCodes.txt: a tab-delimited, UTF-8 text file of eight-character string identifying an aquifer. Codes are defined by the "Catalog of Aquifer Names and Geologic Unit Codes used by the USGS. (accessed December 4, 2019 at https://help.waterdata.usgs.gov/aqfr_cd) AtbtTbl_NatAqfrCodes.txt: a tab-delimited, UTF-8 text file of ten-character strings identifying a National aquifer, or principal aquifer of the United States, that are defined as regionally extensive aquifers or aquifer systems that have the potential to be used as a source of potable water. (accessed December 4, 2019 at

Since the 1940's, hydrologists have used aquifer tests to estimate the hydrogeologic properties near test wells. Results from these tests are recorded in various files, databases, reports and scientific publications. The U.S. Geological Survey (USGS), Lower Mississippi-Gulf Water Science Center (LMG) is aggregating all aquifer test results from Alabama, Arkansas, Louisiana, Mississippi and Tennessee into a single dataset that is publicly available in a machine-readable format. This dataset contains information and results from 2,245 aquifer tests compiled for aquifers located in the LMG-Hydrogeologic Aquifer Test Dataset - December 2020. Descriptive statistics for the December 2020 dataset are presented in Table 1 (below) and in the Summary_Readme.pdf. Additionally, this dataset contains 6 attribute tables (.txt files) with additional information for various fields, a zip file containing the geospatial data, and the companion attribute table as a .txt file. THE LMG-HYDROGEOLOGIC AQUIFER TEST DATASET – DECEMBER 2020 IS AVAILABLE IN TWO FORMATS: 1) a tab delimited text (.txt) UTF-8 file and 2) an ESRI GIS point shapefile. FIELDS INCLUDED IN THE LMG-HYDROGEOLOGIC AQUIFER TEST DATASET – DECEMBER 2020: [a complete list of field names, their definitions and units are listed in the Summary_Readme.pdf file] Location data: USGS site identification number, local identification name, Public Land Survey System number, latitude, longitude, State and county. Well construction data: Construction date, well depth, Diameter of well, diameter of casing, depth to top of opening (screen) interval, depth to bottom of opening interval and length of the open interval. Aquifer data: Local aquifer name and code, national aquifer name and code, top of aquifer (altitude), bottom of aquifer, and thickness of aquifer. Groundwater test data: Test date, yield/discharge, length of time associated with yield, static water-level in feet below land surface, production water-level in feet below land surface associated with yield, drawdown associated with yield. Hydrogeologic data: Specific capacity, transmissivity, horizontal Conductivity, vertical conductivity, permeability and storage coefficient. Ancillary data: Method of test analysis and data source reference. DESCRIPTIONS OF ATTACHED FILES: Summary_Readme.pdf: a Portable Document Format (PDF) file with field names, definitions and units for the aquifer test dataset and the associated attribute tables. This file also contains summary statistics for aquifer test compiled through December 2020. LMG-HydrogeologicAqfrTestDataset_Dec2020.txt: a tab-delimited, UTF-8 text file of the attribute table associated with the LMG-HydrogeologicTestData_Dec2020 geospatial dataset. AtbtTbl_AqfrCd_Readme.txt: an UTF-8 text file containing information from the National Water Information System: Help System web page about USGS groundwater codes. (accessed December 4, 2019 at https://help.waterdata.usgs.gov/codes-and-parameters) AtbtTbl_FipsGeographyCodes.txt: a tab-delimited, UTF-8 text file of FIPS (Federal Information Processing Standards) codes, uniquely identifying States, counties and county equivalents in the United States. Note: to reduce the size of this file, city codes were removed. (accessed January 8, 2020 at https://www.census.gov/geographies/reference-files/2017/demo/popest/2017-fips.html). AtbtTbl_LocalAqfrCodes.txt: a tab-delimited, UTF-8 text file of eight-character string identifying an aquifer. Codes are defined by the "Catalog of Aquifer Names and Geologic Unit Codes used by the USGS. (accessed December 4, 2019 at https://help.waterdata.usgs.gov/aqfr_cd) AtbtTbl_NatAqfrCodes.txt: a tab-delimited, UTF-8 text file of ten-character strings identifying a National aquifer, or principal aquifer of the United States, that are defined as regionally extensive aquifers or aquifer systems that have the potential to be used as a source of potable water. (accessed December 4, 2019 at

Short-term aquifer tests were conducted to estimate hydraulic properties in an alluvial aquifer. Tests included eight single-hole pumping and recovery tests and three slug tests (in a single well). These investigations were conducted in the Wet Mountain Valley, in Custer and Fremont Counties, Colorado. The U.S. Geological Survey (USGS) conducted aquifer tests in May, 2019. These aquifer tests inform the conceptual understanding of the valley-fill aquifer and serve as primary inputs to the numerical groundwater-flow model. Testing was completed in cooperation with the Upper Arkansas Water Conservancy District. This data release contains raw data from aquifer tests, water-level and pumping discharge rate measurements, well logs, graphs of the testing data, and plots of analytical solutions.

Short-term aquifer tests were conducted to estimate hydraulic properties in an alluvial aquifer. Tests included eight single-hole pumping and recovery tests and three slug tests (in a single well). These investigations were conducted in the Wet Mountain Valley, in Custer and Fremont Counties, Colorado. The U.S. Geological Survey (USGS) conducted aquifer tests in May, 2019. These aquifer tests inform the conceptual understanding of the valley-fill aquifer and serve as primary inputs to the numerical groundwater-flow model. Testing was completed in cooperation with the Upper Arkansas Water Conservancy District. This data release contains raw data from aquifer tests, water-level and pumping discharge rate measurements, well logs, graphs of the testing data, and plots of analytical solutions.

Airborne electromagnetic (AEM), magnetic, and radiometric data were acquired May 25 through August 7, 2021 along 10,706 line-kilometers (line-km) over the Mississippi Alluvial Plain (MAP). Data were acquired by Xcalibur Multiphysics with three different helicopter-borne sensors: the Xcalibur Multiphysics Resolve frequency-domain AEM instrument that is used to map subsurface geologic structure at depths up to 100 meters, depending on the subsurface resistivity; a Scintrex CS-3 cesium vapor magnetometer that detects changes in deep (hundreds of meters to kilometers) geologic structure based on variations in the magnetic properties of different formations; and a Radiation Solutions RS-500 spectrometer that detects the abundance of natural radioelements potassium, uranium, and thorium in the upper 20-30 cm that is used to determine differences in soil constituents. The survey was flown at a nominal sensor flight height of 30 m above terrain. Sixteen rivers were surveyed along their center axes, covering 3,467 line-km. Ten rivers are within the surficial Mississippi River Alluvial aquifer boundary: Black River, White River, Big Sunflower River, Little Sunflower River, Ouachita River, Tensas River, Obion River, Saline River, Little Red River, and Bogue Phalia. Six rivers are within the Chicot aquifer boundary: Vermillion River, Bayou Teche, Mermentau River, Calcasieu River, Sabine River, and Bayou Lacassine. Select levee reaches were surveyed along the Mississippi and Arkansas Rivers along the riverside toe, landside toe, and 91m landward offset from the landside toe for a total of 5,896 line-km. Four grids were flown over gravel bars in the Mississippi River: Prairie Point block, Island 63 block, Crumrod block, White River block, and three short segments along the Mississippi River targeting gravel bars. Three additional grids were flown: (1) Melton site in Mississippi with 100-m spaced north-south flight lines for a total of 23 line-km, (2) optically stimulated luminescence (OSL) core study site in Arkansas with 500m east-west line spacing for a total of 268 line-km, and (3) Raccourci Lake in Louisiana with variable flight lines for a total of 100 line-km. Additional detail on flight line numbers is included in the supplemental section. Also included is a small levee dataset acquired in March 2018 near Greenville, Mississippi during the Shellmound AEM survey https://www.sciencebase.gov/catalog/item/5c9e6c42e4b0b8a7f62f5da6. This dataset does not contain magnetic and radiometric data. The survey includes four lines parallel to and over the levee for a total of 27 line-km. This data release includes laterally-constrained inverted depth sections along all flight lines from the AEM data. Digital data of the laterally constrained inversions are provided and fields are defined in the data dictionary https://www.sciencebase.gov/catalog/item/5d76ba5ce4b0c4f70d01ff94.

Airborne electromagnetic (AEM), magnetic, and radiometric data were acquired May 25 through August 7, 2021 along 10,706 line-kilometers (line-km) over the Mississippi Alluvial Plain (MAP). Data were acquired by Xcalibur Multiphysics with three different helicopter-borne sensors: the Xcalibur Multiphysics Resolve frequency-domain AEM instrument that is used to map subsurface geologic structure at depths up to 100 meters, depending on the subsurface resistivity; a Scintrex CS-3 cesium vapor magnetometer that detects changes in deep (hundreds of meters to kilometers) geologic structure based on variations in the magnetic properties of different formations; and a Radiation Solutions RS-500 spectrometer that detects the abundance of natural radioelements potassium, uranium, and thorium in the upper 20-30 cm that is used to determine differences in soil constituents. The survey was flown at a nominal sensor flight height of 30 m above terrain. Sixteen rivers were surveyed along their center axes, covering 3,467 line-km. Ten rivers are within the surficial Mississippi River Alluvial aquifer boundary: Black River, White River, Big Sunflower River, Little Sunflower River, Ouachita River, Tensas River, Obion River, Saline River, Little Red River, and Bogue Phalia. Six rivers are within the Chicot aquifer boundary: Vermillion River, Bayou Teche, Mermentau River, Calcasieu River, Sabine River, and Bayou Lacassine. Select levee reaches were surveyed along the Mississippi and Arkansas Rivers along the riverside toe, landside toe, and 91m landward offset from the landside toe for a total of 5,896 line-km. Four grids were flown over gravel bars in the Mississippi River: Prairie Point block, Island 63 block, Crumrod block, White River block, and three short segments along the Mississippi River targeting gravel bars. Three additional grids were flown: (1) Melton site in Mississippi with 100-m spaced north-south flight lines for a total of 23 line-km, (2) optically stimulated luminescence (OSL) core study site in Arkansas with 500m east-west line spacing for a total of 268 line-km, and (3) Raccourci Lake in Louisiana with variable flight lines for a total of 100 line-km. Additional detail on flight line numbers is included in the supplemental section. Also included is a small levee dataset acquired in March 2018 near Greenville, Mississippi during the Shellmound AEM survey https://www.sciencebase.gov/catalog/item/5c9e6c42e4b0b8a7f62f5da6. This dataset does not contain magnetic and radiometric data. The survey includes four lines parallel to and over the levee for a total of 27 line-km. This data release includes laterally-constrained inverted depth sections along all flight lines from the AEM data. Digital data of the laterally constrained inversions are provided and fields are defined in the data dictionary https://www.sciencebase.gov/catalog/item/5d76ba5ce4b0c4f70d01ff94.

Airborne electromagnetic (AEM), magnetic, and radiometric data were acquired May 25 through August 7, 2021 along 10,706 line-kilometers (line-km) over the Mississippi Alluvial Plain (MAP). Data were acquired by Xcalibur Multiphysics with three different helicopter-borne sensors: the Xcalibur Multiphysics Resolve frequency-domain AEM instrument that is used to map subsurface geologic structure at depths up to 100 meters, depending on the subsurface resistivity; a Scintrex CS-3 cesium vapor magnetometer that detects changes in deep (hundreds of meters to kilometers) geologic structure based on variations in the magnetic properties of different formations; and a Radiation Solutions RS-500 spectrometer that detects the abundance of natural radioelements potassium, uranium, and thorium in the upper 20-30 cm that is used to determine differences in soil constituents. The survey was flown at a nominal sensor flight height of 30 m above terrain. Sixteen rivers were surveyed along their center axes, covering 3,467 line-km. Ten rivers are within the surficial Mississippi River Alluvial aquifer boundary: Black River, White River, Big Sunflower River, Little Sunflower River, Ouachita River, Tensas River, Obion River, Saline River, Little Red River, and Bogue Phalia. Six rivers are within the Chicot aquifer boundary: Vermillion River, Bayou Teche, Mermentau River, Calcasieu River, Sabine River, and Bayou Lacassine. Select levee reaches were surveyed along the Mississippi and Arkansas Rivers along the riverside toe, landside toe, and 91m landward offset from the landside toe for a total of 5,896 line-km. Four grids were flown over gravel bars in the Mississippi River: Prairie Point block, Island 63 block, Crumrod block, White River block, and three short segments along the Mississippi River targeting gravel bars. Three additional grids were flown: (1) Melton site in Mississippi with 100-m spaced north-south flight lines for a total of 23 line-km, (2) optically stimulated luminescence (OSL) core study site in Arkansas with 500m east-west line spacing for a total of 268 line-km, and (3) Raccourci Lake in Louisiana with variable flight lines for a total of 100 line-km. Additional detail on flight line numbers is included in the supplemental section. Also included is a small levee dataset acquired in March 2018 near Greenville, Mississippi during the Shellmound AEM survey https://www.sciencebase.gov/catalog/item/5c9e6c42e4b0b8a7f62f5da6. This dataset does not contain magnetic and radiometric data. The survey includes four lines parallel to and over the levee for a total of 27 line-km. This data release includes laterally-constrained inverted depth sections along all flight lines from the AEM data. Digital data of the laterally constrained inversions are provided and fields are defined in the data dictionary https://www.sciencebase.gov/catalog/item/5d76ba5ce4b0c4f70d01ff94.