Identification_Information: Citation: Citation_Information: Originator: Jared D. Abraham Originator: James C. Cannia Originator: Paul A. Bedrosian Originator: Lyndsay B. Ball Originator: Steven S. Sibray Originator: Michaela R. Johnson Publication_Date: 2011 Title: Airborne Electromagnetic Mapping of the Base of Aquifer in Areas of Western Nebraska: Point Locations of Base of Aquifer Elevation for the South Platte Natural Resouces District study area Geospatial_Data_Presentation_Form: vector digital data Series_Information: Series_Name: Scientific Investigations Report Issue_Identification: 2011-5219 Publication_Information: Publication_Place: Reston, Virginia Publisher: U.S. Geological Survey Online_Linkage: http://pubs.usgs.gov/SIR/2011/5219/ Larger_Work_Citation: Citation_Information: Originator: Jared D. Abraham Originator: James C. Cannia Originator: Paul A. Bedrosian Originator: Lyndsay B. Ball Originator: Steven S. Sibray Originator: Michaela R. Johnson Publication_Date: 2011 Title: Airborne Electromagnetic Mapping of the Base of Aquifer in Areas of Western Nebraska Series_Information: Series_Name: Scientific Investigations Report Issue_Identification: 2011-5219 Publication_Information: Publication_Place: Reston, Virginia Publisher: U.S. Geological Survey Online_Linkage: http://pubs.usgs.gov/SIR/2011/5219/ Description: Abstract: The U.S. Geological Survey and its partners have collaborated to use 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 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 to 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. Purpose: The purpose of this study is to enhance understanding of the ground-water and surface-water relationships in Western Nebraska. This data set provides the base of aquifer contours enhanced with airborne electromagnetic (AEM) surveys in the North Platte and South Platte Natural Resources Districts. Supplemental_Information: References ---------------------------------- COHYST, 2005, Testhole digital coverage for COHYST area. Values are currently being modified (01/05): g003iotwce_012405.exe, accessed May 27, 2011, at http://cohyst.dnr.ne.gov/cohyst_preliminarydata.html#geology. COHYST, 2006, Contour Bottom Layers coverage for COHYST: g012hu_contourb7_1106, accessed May 8, 2008, at http://cohyst.dnr.ne.gov/cohyst_preliminarydata.html#geology. Nebraska Department of Natural Resources in work-share agreement with the U.S. Geological Survey, 1998, 7.5 Digital Elevation Models - DEM - 10 meter - Index for the State of Nebraska: Menlo Park, CA, U.S. Geological Survey, raster digital data, accessed January 20, 2010, at http://www.dnr.state.ne.us/databank/dem.html. Worboys, M.F., 1995, GIS-A computer science perspective: Taylor and Francis, London, 376 p. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 2008 Ending_Date: 2010 Currentness_Reference: ground condition Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -104.068240 East_Bounding_Coordinate: -102.033245 North_Bounding_Coordinate: 41.459295 South_Bounding_Coordinate: 40.967779 Keywords: Theme: Theme_Keyword_Thesaurus: ISO 19115 Topic Category Theme_Keyword: geoscientificInformation Theme_Keyword: imageryBaseMapsEarthCover Theme_Keyword: environment Place: Place_Keyword_Thesaurus: Geographic Names Information System Place_Keyword: Scottsbluff Place_Keyword: Nebraska Place_Keyword: Sidney Access_Constraints: None Use_Constraints: Acknowledgment of the USGS would be appreciated. Point_of_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: Jared Abraham Contact_Position: Geophysicist Contact_Address: Address_Type: mailing address Address: PO Box 25046,MS964 Address: Denver Federal Center City: Denver State_or_Province: Colorado Postal_Code: 80225 Contact_Voice_Telephone: 303.236.1318 Contact_Electronic_Mail_Address: jdabraha@usgs.gov Contact_Instructions: Contact via email. Security_Information: Security_Classification_System: None Security_Classification: Unclassified Security_Handling_Description: Security classification is unclassified. Native_Data_Set_Environment: Microsoft Windows Vista Version 6.1 (Build 7600) ; ESRI ArcCatalog 9.3.1.3000 Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: Arc feature attribute values were inspected and found to be consistently coded as described in the Entity and Attribute section. Logical_Consistency_Report: Using ArcGIS tools and routines all arcs were checked for node errors, overshoots, undershoots, dangles, intersections, and duplicate features. Completeness_Report: This data set includes only the study area for the AEM investigation conducted in the South Platte NRD in Nebraska. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Horizontal accuracy was not assessed. Lineage: Source_Information: Source_Citation: Citation_Information: Originator: COHYST Publication_Date: 2006 Title: g012hu_contourb7_1106.shp Geospatial_Data_Presentation_Form: vector digital data Online_Linkage: http://cohyst.dnr.ne.gov/cohyst_preliminarydata.html#geology Source_Scale_Denominator: 250,000 Type_of_Source_Media: online Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2006 Source_Currentness_Reference: publication date Source_Citation_Abbreviation: COHYST, 2006 Source_Contribution: 100-foot base of aquifer contours Source_Information: Source_Citation: Citation_Information: Originator: COHYST Publication_Date: 2005 Title: iotwce_012405 Online_Linkage: http://cohyst.dnr.ne.gov/cohyst_preliminarydata.html#geology Type_of_Source_Media: online Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2005 Source_Currentness_Reference: publication date Source_Citation_Abbreviation: COHYST, 2005 Source_Contribution: Testhole digital coverage providing the base of aquifer elevation. Source_Information: Source_Citation: Citation_Information: Originator: Jared D. Abraham Originator: James C. Cannia Originator: Paul A. Bedrosian Originator: Lyndsay B. Ball Originator: Steven S. Sibray Originator: Michaela R. Johnson Publication_Date: 2011 Title: Airborne Electromagnetic Mapping of the Base of Aquifer in Areas of Western Nebraska: Point locations of base of aquifer elevation Series_Information: Series_Name: Scientific Investigations Report Issue_Identification: 2011-5219 Publication_Information: Publication_Place: Reston, Virginia Publisher: U.S. Geological Survey Online_Linkage: http://pubs.usgs.gov/SIR/2011/5219/ Larger_Work_Citation: Citation_Information: Originator: Jared D. Abraham Originator: James C. Cannia Originator: Paul A. Bedrosian Originator: Lyndsay B. Ball Originator: Steven S. Sibray Originator: Michaela R. Johnson Publication_Date: 2011 Title: Airborne Electromagnetic Mapping of the Base of Aquifer in Areas of Western Nebraska Series_Information: Series_Name: Scientific Investigations Report Issue_Identification: 2011-5219 Publication_Information: Publication_Place: Reston, Virginia Publisher: U.S. Geological Survey Online_Linkage: http://pubs.usgs.gov/SIR/2011/5219/ Type_of_Source_Media: online Source_Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 2008 Ending_Date: 2010 Source_Currentness_Reference: ground condition Source_Citation_Abbreviation: Abraham and others, 2011 Source_Contribution: Point locations of base of aquifer elevation identified from COHYST test hole shapefile (COHYST, 2005), airborne electromagnetic survey (AEM), and time-domain electromagnetic (TDEM) survey. Source_Information: Source_Citation: Citation_Information: Originator: Nebraska Department of Natural Resources in work-share agreement with the U.S. Geological Survey Publication_Date: 1998 Title: 7.5 Digital Elevation Models - DEM - 10 meter Online_Linkage: http://www.dnr.state.ne.us/databank/dem.html. Source_Scale_Denominator: 24,000 Type_of_Source_Media: online Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 1998 Source_Currentness_Reference: publication date Source_Citation_Abbreviation: NDNR, 1998 Source_Contribution: Land surface elevation for redefining base of aquifer contours where the base outcrops at land surface. Process_Step: Process_Description: 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). Process_Date: 20100903 Process_Step: Process_Description: 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) used in the original interpolation of the base of aquifers were used as elevation control again in the contour refinement. Additional point locations for base of aquifer elevation were provided from the time-domain electromagnetic (TDEM) surveys conducted at a network of locations coinciding with AEM flight paths. The TDEM surveys were used to identify the base of aquifer elevation where the thickness of overburden was greater. Process_Date: 20101004 Process_Step: Process_Description: The COHYST base of aquifer contours originally had a 100-foot contour interval. Preliminary 50-foot contours were generated using the ArcGIS application, Topogridtool, to interpolate the contour surface and recontour at 50-foot interval (Worboys, 1995). Process_Date: 20101005 Process_Step: Process_Description: The new preliminary set of 50-foot base of aquifer contours were redefined using the point locations of base of aquifer elevation. The redefined contours were compared with land surface elevation as a consistency check. Where the base of aquifer intersects land surface the contours were reshaped to follow 90-meter DEM contours (10-meter NDNR DEM resample (bilinear) to 30-m and then resampled again (bilinear) to 90-m. The 90-meter cell size was used because this is scale of the base of aquifer contours. Process_Date: 20101106 Process_Step: Process_Description: To facilitate comparison between the original COHYST contours and the redefined AEM-TDEM contours the contours were interpolated to raster surfaces again using the ArcGIS application, Topogridtool. An estimate of aquifer thickness was created from the subtraction of the 90-meter AEM-TDEM surface from the 90-meter DEM. Process_Date: 20111115 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Vector Point_and_Vector_Object_Information: SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: String Point_and_Vector_Object_Count: 169 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Grid_Coordinate_System: Grid_Coordinate_System_Name: Universal Transverse Mercator Universal_Transverse_Mercator: UTM_Zone_Number: 13 Transverse_Mercator: Scale_Factor_at_Central_Meridian: 0.999600 Longitude_of_Central_Meridian: -105.000000 Latitude_of_Projection_Origin: 0.000000 False_Easting: 500000.000000 False_Northing: 0.000000 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: 0.001 Ordinate_Resolution: 0.001 Planar_Distance_Units: meters Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1983 Ellipsoid_Name: Geodetic Reference System 80 Semi-major_Axis: 6378137.000000 Denominator_of_Flattening_Ratio: 298.257222 Vertical_Coordinate_System_Definition: Altitude_System_Definition: Altitude_Datum_Name: National Geodetic Vertical Datum of 1929 Altitude_Resolution: 25 Altitude_Distance_Units: feet Altitude_Encoding_Method: Explicit elevation coordinate included with horizontal coordinates Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: SPNRD_ALL_aqbase_control_points Entity_Type_Definition: Point locations of base of aquifer elevation Entity_Type_Definition_Source: U.S. Geological Survey Attribute: Attribute_Label: FID Attribute_Definition: Internal feature number. Attribute_Definition_Source: ESRI Attribute_Domain_Values: Unrepresentable_Domain: Sequential unique whole numbers that are automatically generated. Attribute: Attribute_Label: Shape Attribute_Definition: Feature geometry. Attribute_Definition_Source: ESRI Attribute_Domain_Values: Unrepresentable_Domain: Coordinates defining the features. Attribute: Attribute_Label: THNUM Attribute_Definition: Unique test hole identifier from University of Nebraska-Lincoln, Conservation and Survey Division Attribute_Definition_Source: COHYST, 2005 Attribute_Domain_Values: Unrepresentable_Domain: Unique identifier for UNL CSD test holes. Attribute: Attribute_Label: REGNUM Attribute_Definition: Well registration number from Nebraska Department of Natural Resources. Attribute_Definition_Source: COHYST, 2005 Attribute_Domain_Values: Unrepresentable_Domain: Unique identifier for NDNR registered wells. Attribute: Attribute_Label: SOURCE Attribute_Definition: Source of point location for base of aquifer elevation Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Enumerated_Domain: Enumerated_Domain_Value: TDEM Enumerated_Domain_Value_Definition: Time-domain electromagnetic survey Enumerated_Domain_Value_Definition_Source: U.S. Geological Survey Enumerated_Domain: Enumerated_Domain_Value: AEM Enumerated_Domain_Value_Definition: Airborne electromagnetic survey Enumerated_Domain_Value_Definition_Source: U.S. Geological Survey Enumerated_Domain: Enumerated_Domain_Value: COHYST Enumerated_Domain_Value_Definition: Cooperative Hydrologic Study Team test holes and wells Enumerated_Domain_Value_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Enumerated_Domain: Enumerated_Domain_Value: AEM Enumerated_Domain_Value_Definition: Airborne electromagnetic survey Enumerated_Domain_Value_Definition_Source: U.S. Geological Survey Attribute: Attribute_Label: BASE_FT29 Attribute_Definition: Elevation of base of aquifer, in feet, referenced to National Geodetic Vertical Datum of 1929 Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 3101 Range_Domain_Maximum: 5359.4 Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: Jared D. Abraham Contact_Position: Geophysicist Contact_Address: Address_Type: mailing address Address: PO Box 25046,MS964 Address: Denver Federal Center City: Denver State_or_Province: Colorado Postal_Code: 80225 Contact_Voice_Telephone: 303.236.1318 Contact_Electronic_Mail_Address: jdabraha@usgs.gov Contact_Instructions: Contact via email. Resource_Description: Downloadable Data Distribution_Liability: 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. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: Shapefile Transfer_Size: 0.217 Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: http://pubs.usgs.gov/SIR/2011/5219/ Fees: None Metadata_Reference_Information: Metadata_Date: 20110527 Metadata_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: Bruce D. Smith Contact_Position: Geophysicist Contact_Address: Address_Type: mailing address Address: PO Box 25046,MS964 Address: Denver Federal Center City: Denver State_or_Province: Colorado Postal_Code: 80225 Contact_Voice_Telephone: 303.236.1399 Contact_Electronic_Mail_Address: bsmith@usgs.gov Contact_Instructions: Contact via email. Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Time_Convention: local time Metadata_Extensions: Online_Linkage: http://www.esri.com/metadata/esriprof80.html Profile_Name: ESRI Metadata Profile