This data set represents the extent of the alluvial and glacial aquifers north of the southern-most line of glaciation. Aquifers are shown in the States of Maine, Vermont, New Hampshire, Connecticut, Massachusetts, Rhode Island, New Jersey, New York, Pennsylvania, Ohio, Indiana, Michigan, Wisconsin, Illinois, Minnesota, Iowa, Missouri, Kansas, Nebraska, South Dakota, North Dakota, and Montana. These data delineate the areal extent of the alluvial and glacial aquifers as defined in The Ground Water Atlas of The United States.

This geodatabase includes spatial datasets that represent the Silurian-Devonian aquifers in the States of Illinois, Indiana, Iowa, Kentucky, Michigan, Missouri, Ohio, Tennessee, and Wisconsin. Included are: (1) polygon extents; datasets that represent the aquifer system extent, and the entire extent subdivided into subareas, (2) raster datasets for the altitude of the top and bottom surfaces of the entire aquifer (where data are available), and (3) altitude contours used to generate the surface rasters. The digitized contours are supplied for reference. The extent of the Silurian-Devonian aquifers is from the linework of the Silurian-Devonian aquifer extent maps in U.S. Geological Survey U.S. Geological Survey Hydrologic Atlas 730, Chapters J and K, (USGS HA 730-J, -K) and a digital version of the aquifer extent presented in the National Aquifer Code Reference List, available at http://water.usgs.gov/ogw/NatlAqCode-reflist.html , "silurian.zip". The extent was then modified for each subarea: Subarea 1 (sa1): Primarily in Ohio and Indiana, subject of U.S. Geological Survey Professional Paper 1423 B (USGS PP 1423B). Subarea 2 (sa2): In Iowa. Digital data were available from the Iowa Geologic Survey. Subarea 3 (sa3): Remaining area in Illinois, Wisconsin, Michigan, and Kentucky. Extent is that part of the National Aquifer Code Reference List polygon that remained when the areas of sa1 and sa2 were removed. The altitude and thickness contours that were available for each subarea were compiled or generated from georeferenced figures of altitude contours in USGS PP 1423B for sa1, digital data from IAGS for sa2. There were no vertical data for sa3. The resultant top and bottom altitude values were interpolated into surface rasters within a GIS using tools that create hydrologically correct surfaces from contour data, derive the altitude from the thickness (depth from the land surface), and merge the subareas into a single surface. The primary tool was an enhanced version of "Topo to Raster" used in ArcGIS, ArcMap, Esri 2014. The raster surfaces were corrected in the areas where the altitude of an underlying layer of the aquifer exceeded the altitude of an overlying layer.

The Mississippi Alluvial Plain (MAP) has become one of the most important agricultural regions in the US, and it relies heavily on a groundwater system that is poorly understood and shows signs of substantial change. The heavy use of the available groundwater resources has resulted in significant groundwater-level declines and reductions in base flow in streams within the MAP. These impacts are limiting well production and threatening future water-availability for the region. This product will help not only scientists in our center, but also at a national level. This product will also be part of a larger study encompassing the Mississippi Alluvial Plain region. The Mississippi Alluvial Plain extent was delineated using GIS tools to represent the geographic extent of the Mississippi Alluvial Aquifer through incorporation of elevation information, geomorphology knowledge, ecological region extent, and previously published extents for part of the MAP region. The current MAP extent represents version 1.0. Future changes to the MAP extent will be tracked through increasing version numbers.

Electrical resistivity results from four regional airborne electromagnetic (AEM) surveys (Burton et al. 2024, Hoogenboom et al. 2023, Minsley et al. 2021, Burton et al. 2021) over the Mississippi Alluvial Plain (MAP) were combined by the U.S. Geological Survey (USGS) to produce three-dimensional (3D) gridded models and derivative hydrogeologic products. The 3D elevation grid was used to quantify across the MAP region 1) the occurrence and thickness of surficial (< 15 meter (m) depth) confining material, 2) the top and bottom elevation corresponding to the surficial confining material, and 3) a metric representing the degree of surface confinement or connectivity that ranges from fully confining conditions to high potential hydrologic connectivity. These products were generated using the updated 12-class facies classifications of the 3D electrical resistivity model. See child item “Mississippi Alluvial Plain (MAP): Electrical Resistivity & Facies Classification Grids” for more details on the facies classes: https://www.sciencebase.gov/catalog/item/5f03a7bc82ce0afb2446e11f. The final surfaces and hydrogeologic metrics were exported as raster images in Georeferenced Tagged Image File Format (GeoTIFF) format. Burton, B.L., Adams, R.F. Adams, Minsley, B.J., Pace, M.D.M., Kress, W.H., Rigby, J.R., and Bussell, A.M., 2024, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, March 2018 and May - August 2021: U.S. Geological Survey data release, https://doi.org/10.5066/P9KPK3UJ. Hoogenboom, B.E., Minsley, B.J., James, S.R., and Pace, M.D., 2023, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, Mississippi Embayment, and Gulf Coastal Plain, September 2021 - January 2022: U.S. Geological Survey data release, https://doi.org/10.5066/P93DO0EO. Burton, B.L., Minsley, B.J., Bloss, B.R., and Kress, W.H., 2021, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, November 2018 - February 2019: U.S. Geological Survey data release, https://doi.org/10.5066/P9XBBBUU. Minsley, B.J., James, S.R., Bedrosian, P.A., Pace, M.D., Hoogenboom, B.E., and Burton, B.L., 2021, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, November 2019 - March 2020: U.S. Geological Survey data release, https://doi.org/10.5066/P9E44CTQ.

Electrical resistivity results from four regional airborne electromagnetic (AEM) surveys (Burton et al. 2024, Hoogenboom et al. 2023, Minsley et al. 2021, Burton et al. 2021) over the Mississippi Alluvial Plain (MAP) were combined by the U.S. Geological Survey (USGS) to produce three-dimensional (3D) gridded models and derivative hydrogeologic products. The 3D elevation grid was used to quantify across the MAP region 1) the occurrence and thickness of surficial (< 15 meter (m) depth) confining material, 2) the top and bottom elevation corresponding to the surficial confining material, and 3) a metric representing the degree of surface confinement or connectivity that ranges from fully confining conditions to high potential hydrologic connectivity. These products were generated using the updated 12-class facies classifications of the 3D electrical resistivity model. See child item “Mississippi Alluvial Plain (MAP): Electrical Resistivity & Facies Classification Grids” for more details on the facies classes: https://www.sciencebase.gov/catalog/item/5f03a7bc82ce0afb2446e11f. The final surfaces and hydrogeologic metrics were exported as raster images in Georeferenced Tagged Image File Format (GeoTIFF) format. Burton, B.L., Adams, R.F. Adams, Minsley, B.J., Pace, M.D.M., Kress, W.H., Rigby, J.R., and Bussell, A.M., 2024, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, March 2018 and May - August 2021: U.S. Geological Survey data release, https://doi.org/10.5066/P9KPK3UJ. Hoogenboom, B.E., Minsley, B.J., James, S.R., and Pace, M.D., 2023, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, Mississippi Embayment, and Gulf Coastal Plain, September 2021 - January 2022: U.S. Geological Survey data release, https://doi.org/10.5066/P93DO0EO. Burton, B.L., Minsley, B.J., Bloss, B.R., and Kress, W.H., 2021, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, November 2018 - February 2019: U.S. Geological Survey data release, https://doi.org/10.5066/P9XBBBUU. Minsley, B.J., James, S.R., Bedrosian, P.A., Pace, M.D., Hoogenboom, B.E., and Burton, B.L., 2021, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, November 2019 - March 2020: U.S. Geological Survey data release, https://doi.org/10.5066/P9E44CTQ.

As part of the U.S. Geological Survey (USGS) Water Availability and Use Science Program study of the Mississippi Alluvial Plain (MAP), a shapefile representing seven generalized regions of the MAP extent as defined by Painter and Westerman (2018) was compiled. The generalized regions provide a framework for analysis, visualization, and regional comparisons of local data within the MAP. Regions north of the Red River were based on those described by Ackerman (1996). The Grand Prairie region includes the area north and east of the Arkansas River and south and west of the White River within the MAP. The Cache region includes the area north and east of the White River and the area generally west of Crowley’s Ridge, which lies outside of the MAP extent (Painter and Westerman, 2018), bisects the northern part of the MAP, and has elevations 100 to 250 feet (ft) higher than the MAP (Ackerman, 1996). The Delta region, which is roughly equivalent to the Yazoo River drainage, lies predominately in Mississippi and covers much of the area east of the Mississippi River within the MAP. The Boeuf region covers the area north of the Red River and the Little Old River - Mississippi River confluence, the area south of the Arkansas River, and the area west of the Delta region within the MAP. The St. Francis region lies generally east of Crowley’s Ridge and north of the Delta region in parts of Tennessee, Kentucky, Illinois, Missouri, and Arkansas. The regions south of the Red River and the Little Old River – Mississippi River confluence were based primarily on depositional environment (Saucier, 1994). The Atchafalaya region contains the Atchafalaya River. The Deltaic and Chenier Plains region lies south of the Atchafalaya region and covers the southernmost part of the MAP. In order to keep the regions contiguous, some relatively small parts of the Deltaic and Chenier Plains as defined by Saucier (1994) were included within the boundary of the Atchafalaya region defined for this study, and vice-versa. References Ackerman, D.J., 1996, Hydrology of the Mississippi River Valley alluvial aquifer, South-Central United States: U.S. Geological Survey Professional Paper 1416-D, 56 p., 8 pls. in pocket. 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. Saucier, R.T., 1994, Geomorphology and Quaternary geologic history of the Lower Mississippi Valley: U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS, Vols. I and II, 398 p., 28 pls.

Electrical resistivity results from four regional airborne electromagnetic (AEM) surveys (Burton et al. 2024, Hoogenboom et al. 2023, Minsley et al. 2021, Burton et al. 2021) over the Mississippi Alluvial Plain (MAP) were combined by the U.S. Geological Survey (USGS) to produce three-dimensional (3D) gridded models and derivative hydrogeologic products. To calculate estimates of streambed properties across the MAP region, e.g. the relative connection potential between streams and the adjacent Mississippi River Valley Alluvial aquifer (MRVA), new 3D grids of electrical resistivity were generated for 2 meter (m) depth layers and only shallow depths (0-30 m). One grid was made with the horizontal dimension aligning with the 1 kilometer (km) x 1 km National Hydrogeologic Grid (NHG; Clark et al. 2018), and a second version was generated at a finer resolution of 100 m x 100 m, subdividing the NHG grid. Stream locations taken from the National Hydrograph Dataset Plus (NHDPlus) high resolution dataset were buffered with a 1.0 km radius and then intersected with both shallow 3D depth grids to isolate resistivity values immediately beneath or adjacent to streams. Twelve “facies classes” were defined to categorize materials expected to have similar hydrologic and geologic properties based on their electrical resistivity (i.e. low classes correspond to clays and silts with low permeability, and higher classes reflect larger grain sizes (sands, gravels) with expected higher permeability). The potential hydraulic connection through streambed sediments was estimated by calculating the vertically integrated electrical conductance (VIC) across each 2 m layer between 0 and 10 m depth. The shallow 3D resistivity and facies grids were exported in NetCDF format with an accompanying XML NetCDF Markdown Language metadata file. The streambed connectivity estimates were exported as raster images in Georeferenced Tagged Image File Format (GeoTIFF). Burton, B.L., Adams, R.F. Adams, Minsley, B.J., Pace, M.D.M., Kress, W.H., Rigby, J.R., and Bussell, A.M., 2024, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, March 2018 and May - August 2021: U.S. Geological Survey data release, https://doi.org/10.5066/P9KPK3UJ. Hoogenboom, B.E., Minsley, B.J., James, S.R., and Pace, M.D., 2023, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, Mississippi Embayment, and Gulf Coastal Plain, September 2021 - January 2022: U.S. Geological Survey data release, https://doi.org/10.5066/P93DO0EO. Burton, B.L., Minsley, B.J., Bloss, B.R., and Kress, W.H., 2021, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, November 2018 - February 2019: U.S. Geological Survey data release, https://doi.org/10.5066/P9XBBBUU. Clark, B.R., Barlow, P.M., Peterson, S.M., Hughes, J.D., Reeves, H.W., and Viger, R.J., 2018, National-scale grid to support regional groundwater availability studies and a national hydrogeologic database: U.S. Geological Survey data release, https://doi.org/10.5066/F7P84B24. Minsley, B.J., James, S.R., Bedrosian, P.A., Pace, M.D., Hoogenboom, B.E., and Burton, B.L., 2021, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, November 2019 - March 2020: U.S. Geological Survey data release, https://doi.org/10.5066/P9E44CTQ.

Electrical resistivity results from four regional airborne electromagnetic (AEM) surveys (Burton et al. 2024, Hoogenboom et al. 2023, Minsley et al. 2021, Burton et al. 2021) over the Mississippi Alluvial Plain (MAP) were combined by the U.S. Geological Survey (USGS) to produce three-dimensional (3D) gridded models and derivative hydrogeologic products. To calculate estimates of streambed properties across the MAP region, e.g. the relative connection potential between streams and the adjacent Mississippi River Valley Alluvial aquifer (MRVA), new 3D grids of electrical resistivity were generated for 2 meter (m) depth layers and only shallow depths (0-30 m). One grid was made with the horizontal dimension aligning with the 1 kilometer (km) x 1 km National Hydrogeologic Grid (NHG; Clark et al. 2018), and a second version was generated at a finer resolution of 100 m x 100 m, subdividing the NHG grid. Stream locations taken from the National Hydrograph Dataset Plus (NHDPlus) high resolution dataset were buffered with a 1.0 km radius and then intersected with both shallow 3D depth grids to isolate resistivity values immediately beneath or adjacent to streams. Twelve “facies classes” were defined to categorize materials expected to have similar hydrologic and geologic properties based on their electrical resistivity (i.e. low classes correspond to clays and silts with low permeability, and higher classes reflect larger grain sizes (sands, gravels) with expected higher permeability). The potential hydraulic connection through streambed sediments was estimated by calculating the vertically integrated electrical conductance (VIC) across each 2 m layer between 0 and 10 m depth. The shallow 3D resistivity and facies grids were exported in NetCDF format with an accompanying XML NetCDF Markdown Language metadata file. The streambed connectivity estimates were exported as raster images in Georeferenced Tagged Image File Format (GeoTIFF). Burton, B.L., Adams, R.F. Adams, Minsley, B.J., Pace, M.D.M., Kress, W.H., Rigby, J.R., and Bussell, A.M., 2024, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, March 2018 and May - August 2021: U.S. Geological Survey data release, https://doi.org/10.5066/P9KPK3UJ. Hoogenboom, B.E., Minsley, B.J., James, S.R., and Pace, M.D., 2023, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, Mississippi Embayment, and Gulf Coastal Plain, September 2021 - January 2022: U.S. Geological Survey data release, https://doi.org/10.5066/P93DO0EO. Burton, B.L., Minsley, B.J., Bloss, B.R., and Kress, W.H., 2021, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, November 2018 - February 2019: U.S. Geological Survey data release, https://doi.org/10.5066/P9XBBBUU. Clark, B.R., Barlow, P.M., Peterson, S.M., Hughes, J.D., Reeves, H.W., and Viger, R.J., 2018, National-scale grid to support regional groundwater availability studies and a national hydrogeologic database: U.S. Geological Survey data release, https://doi.org/10.5066/F7P84B24. Minsley, B.J., James, S.R., Bedrosian, P.A., Pace, M.D., Hoogenboom, B.E., and Burton, B.L., 2021, Airborne electromagnetic, magnetic, and radiometric survey of the Mississippi Alluvial Plain, November 2019 - March 2020: U.S. Geological Survey data release, https://doi.org/10.5066/P9E44CTQ.

This dataset includes the surficial extent of the Red River alluvial aquifer, cross-section wells within the Red River alluvial surficial extent, Red River alluvial aquifer base contours and wells, isopach showing combined thickness of the Red River alluvial aquifer sand and gravel units, wells used to construct the isopach of the Red River alluvial aquifer, and well points that were used to construct 25-foot contours showing the altitude of the base of the Red River alluvial aquifer. Datasets are shown in figures of the larger body of work "Hydrogeologic framework of the Red River alluvial aquifer and Carrizo-Wilcox aquifer, in northwestern Louisiana" (Hays and others, 2021).

This dataset includes the surficial extent of the Red River alluvial aquifer, cross-section wells within the Red River alluvial surficial extent, Red River alluvial aquifer base contours and wells, isopach showing combined thickness of the Red River alluvial aquifer sand and gravel units, wells used to construct the isopach of the Red River alluvial aquifer, and well points that were used to construct 25-foot contours showing the altitude of the base of the Red River alluvial aquifer. Datasets are shown in figures of the larger body of work "Hydrogeologic framework of the Red River alluvial aquifer and Carrizo-Wilcox aquifer, in northwestern Louisiana" (Hays and others, 2021).