Christopher M. Hobza Jared D. Abraham James C. Cannia Michaela R. Johnson Steven S. Sibray 20140930 point digital data Reston, Virginia U.S. Geological Survey https://water.usgs.gov/lookup/getspatial?sim3310_SPNRD_ALL_aqbase_control_points_2014 C.M. Hobza, U.S. Geological Survey, Hydrologist 2014 U.S. Geological Survey Scientific Investigations Map 3310 Reston, VA U.S. Geological Survey https://doi.org/10.3133/sim3310 The U.S. Geological Survey and its partners have collaborated to complete airborne geophysical surveys for areas of the North and South Platte River valleys and Lodgepole Creek in western Nebraska. The objective of the surveys was to map the aquifers and bedrock topography of selected areas to help improve the understanding of groundwater-surface-water relationships to be used in water management decisions. Frequency-domain (2008 and 2009) and time-domain (2010) helicopter electromagnetic surveys were completed, using a unique survey flight line design, to collect resistivity data that can be related to lithologic information for refinement of groundwater model inputs. To make the geophysical data useful for multidimensional groundwater models, numerical inversion is necessary to convert the measured data into a depth-dependent subsurface resistivity model. This inversion model, in conjunction with sensitivity analysis, geological ground truth (boreholes), and geological interpretation, is used to characterize hydrogeologic features. The two- and three- dimensional interpretation provides the groundwater modeler with a high-resolution hydrogeologic framework and a quantitative estimate of framework uncertainty. This method of creating hydrogeologic frameworks improved the understanding of the actual flow path orientation by redefining the location of the paleochannels and associated bedrock highs. The improved models represent the hydrogeology at a level of accuracy not achievable using previous data sets. The purpose of this study is to enhance understanding of the groundwater and surface-water relationships in western Nebraska. This data set provides the base of aquifer contours enhanced with airborne electromagnetic (AEM) surveys in the South Platte Natural Resources District. All resistivity data, inversions, and subsequent interpretations of frequency-domain data collected in 2008 and 2009 were reported in the Scientific Investigations Report SIR 2011-5219 (available online at https://pubs.usgs.gov/sir/2011/5219/). Additional surveys were collected in 2010 in the North Platte, South Platte, and Twin Platte Natural Resources Districts. Contractor reports and data were released in the Open-File Report 2013-1268 (available online at http://doi.org/10.3133/ofr20131268). 2008 2010 ground condition Complete None planned -104.2 -102.05 41.44 41.0 ISO 19115 Topic Category geoscientificInformation imageryBaseMapsEarthCover environment inlandWaters USGS Metadata Identifier USGS:5e8d89de-786d-4d58-9b39-d7ecef8a24ff Geographic Names Information System Scottsbluff Nebraska Sidney Ogallala None Acknowledgment of the USGS would be appreciated. U.S. Geological Survey Chris Hobza Hydrologist mailing address

5231 South 19th St

Lincoln Nebraska 68512 402.328.4100 cmhobza@usgs.gov Contact via email. https://water.usgs.gov/GIS/browse/SIM3310_SPNRD_ALL_aqbase_control_points_2014.jpg Illustration of data set jpg This dataset was prepared in cooperation with the South Platte Natural Resources District (NRD) and the University of Nebraska Conservation and Survey Division. The dataset was prepared using information from the Cooperative Hydrology Study, University of Nebraska-Lincoln, Conservation and Survey Division, Nebraska Department of Natural Resources, and the U.S. Geological Survey. None Unclassified Security classification is unclassified. Microsoft Windows Vista Version 6.1 (Build 7600) ; ESRI ArcCatalog 9.3.1.3000 Point feature attribute values were inspected and found to be consistently coded as described in the Entity and Attribute section. All base-of-aquifer elevations are within the contour interval defined by the upper and lower altitude of the bounding contours. This data set includes only the study area for the airborne electromagnetic (AEM) investigation conducted in the South Platte NRD in Nebraska. Horizontal accuracy was not assessed. COHYST 1999 vector digital data http://cohyst.dnr.ne.gov/cohyst_preliminarydata.html#basecoverage 100,000 online 1999 publication date COHYST, 1999 Natural Resources District boundaries COHYST 2006 vector digital data 250,000 online 2006 publication date COHYST, 2006 100-foot base of aquifer contours COHYST 2005 http://cohyst.dnr.ne.gov/cohyst_preliminarydata.html#geology online 2005 publication date COHYST, 2005 Testhole digital coverage providing the base of aquifer elevation. Jared D. Abraham James C. Cannia Paul A. Bedrosian Lyndsay B. Ball Steven S. Sibray Michaela R. Johnson 2012 Scientific Investigations Report 2011-5219 Reston, Virginia U.S. Geological Survey https://pubs.usgs.gov/sir/2011/5219/ Jared D. Abraham James C. Cannia Paul A. Bedrosian Lyndsay B. Ball Steven S. Sibray Michaela R. Johnson 2012 Scientific Investigations Report 2011-5219 Reston, Virginia U.S. Geological Survey https://pubs.usgs.gov/sir/2011/5219/ online 2008 2010 ground condition Abraham and others, 2011 Point locations of base of aquifer elevation identified from COHYST test hole shapefile (COHYST, 2005), AEM survey, and time-domain electromagnetic (TDEM) survey. U.S. Geological Survey Crustal Geophysical and Geochemical Science Center 2014 Open-File Report 2013-1268 Reston, Virginia U.S. Geological Survey https://pubs.usgs.gov/of/2013/1268/ Jared D. Abraham James C. Cannia Paul A. Bedrosian Lyndsay B. Ball Steven S. Sibray Michaela R. Johnson 2014 Open-File Report 2013-1268 Reston, Virginia U.S. Geological Survey https://pubs.usgs.gov/of/2013/1268/ online 2010 2010 ground condition U.S. Geological Survey Crustal Geophysical and Geochemical Science Center, 2014 Describes AEM data acquisition and processing for a electromagnetic time-domain survey. Nebraska Department of Natural Resources in work-share agreement with the U.S. Geological Survey 1998 http://dnr.ne.gov/digital-elevation-models 24,000 online 1998 publication date NDNR, 1998 Land surface elevation for redefining base of aquifer contours where the base outcrops at land surface. U.S. Geological Survey (USGS), EROS Data Center 1999 http://ned.usgs.gov/ned.html 24,000 online 1999 publication date USGS, 1999 Land surface elevation for examining base of aquifer contours where the base of aquifer is near the land surface. AEM surveys were conducted in 2008, 2009, and 2010. The geophysical data collected were resistivity measurements that can be related to lithologic information. The measured resistivity data were ran through a process of numerical inversion to convert data to a depth-dependent subsurface resistivity model. The inversion model, in conjunction with sensitivity analysis, geological ground truth (boreholes), and geological interpretation was used to characterize hydrogeologic features and identify the base of aquifer. Point locations of the base of aquifer elevation were exported to a shapefile for use in redefining the existing base of aquifer contours (COHYST, 2006; Abraham and others, 2012). 20120403 Point locations of base of aquifer elevations were picked from AEM data and borehole geophysical logs confirming the base unit. These locations were exported to shapefile format to provide more detailed elevation control in redefining the base of aquifer contours. Point locations from existing wells and test holes (COHYST, 2005; Abraham and others, 2012) used in the original interpolation of the base of aquifers were used as elevation control again in the contour refinement. 20120403 Vector String 169 Universal Transverse Mercator 13 0.999600 -105.000000 0.000000 500000.000000 0.000000 coordinate pair 0.001 0.001 meters North American Datum of 1983 Geodetic Reference System 80 6378137.000000 298.257222 National Geodetic Vertical Datum of 1929 25 feet Explicit elevation coordinate included with horizontal coordinates SIM3310_SPNRD_ALL_aqbase_control_points_2014 Point locations of base of aquifer elevation U.S. Geological Survey FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Points defining the features. THNUM Unique test hole identifier from University of Nebraska-Lincoln, Conservation and Survey Division subsequently modified by COHYST. The special characters were removed from original identifiers and a numerical suffix was added. COHYST, 2005 Unique identifier for UNL CSD test holes. REGNUM Well registration number from Nebraska Department of Natural Resources. COHYST, 2005 Unique identifier for NDNR registered wells. SOURCE Source of point location for base of aquifer elevation U.S. Geological Survey TDEM Time-domain electromagnetic survey U.S. Geological Survey AEM Airborne electromagnetic survey U.S. Geological Survey COHYST Cooperative Hydrologic Study Team test holes and wells U.S. Geological Survey USGS U.S. Geological Survey test holes U.S. Geological Survey BASE_FT29 Elevation of base of aquifer, in feet, referenced to National Geodetic Vertical Datum of 1929 U.S. Geological Survey 3101 5359.4 U.S. Geological Survey Michael Ierardi IT Specialist mailing and physical

445 National Center

Reston Virginia 20192 USA 1-888-275-8747 (1-888-ASK-USGS) mierardi@usgs.gov Data provided for download Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials. Shapefile 0.217 https://water.usgs.gov/GIS/dsdl/SIM3310_SPNRD_ALL_aqbase_control_points_2014.zip None 20201117 U.S. Geological Survey Michael Ierardi IT Specialist mailing and physical address

445 National Center

Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) mierardi@usgs.gov FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 local time