Identification_Information: Citation: Citation_Information: Originator: David C. Twichell Originator: VeeAnn A. Cross Publication_Date: 2003 Title: TIFF format of the Isopach Map of Postimpoundment Sediment in Lake Mead - Geographic Coordinates Geospatial_Data_Presentation_Form: remote-sensing image Online_Linkage: Larger_Work_Citation: Citation_Information: Originator: David C. Twichell Originator: VeeAnn A. Cross Originator: Stephen D. Belew Publication_Date: 2003 Title: Mapping the floor of Lake Mead (Nevada and Arizona): Preliminary discussion and GIS data release Series_Information: Series_Name: Open-File Report Issue_Identification: 03-320 Publication_Information: Publication_Place: Woods Hole Field Center, Woods Hole, MA Publisher: U.S. Geological Survey Description: Abstract: Lake Mead is a large interstate reservoir located in the Mojave Desert of southeastern Nevada and northwestern Arizona. It was impounded in 1935 by the construction of Hoover Dam and is one of a series of multi-purpose reservoirs on the Colorado River. The lake extends 183 km from the mouth of the Grand Canyon to Black Canyon, the site of Hoover Dam, and provides water for residential, commercial, industrial, recreational, and other non-agricultural users in communities across the southwestern United States. Extensive research has been conducted on Lake Mead, but a majority of the studies have involved determining levels of anthropogenic contaminants such as synthetic organic compounds, heavy metals and dissolved ions, furans/dioxins, and nutrient loading in lake water, sediment, and biota (Preissler, et al., 1998; Bevans et al, 1996; Bevans et al., 1998; Covay and Leiker, 1998; LaBounty and Horn, 1997; Paulson, 1981). By contrast, little work has focused on the sediments in the lake and the processes of deposition (Gould, 1951). To address these questions, sidescan-sonar imagery and high-resolution seismic-reflection profiles were collected throughout Lake Mead by the USGS in cooperation with researchers from University of Nevada Las Vegas (UNLV). These data allow a detailed mapping of the surficial geology and the distribution and thickness of sediment that has accumulated in the lake since the completion of Hoover Dam. Results indicate that the accumulation of post-impoundment sediment is primarily restricted to former river and stream beds that are now submerged below the lake while the margins of the lake appear to be devoid of post-impoundment sediment. The sediment cover along the original Colorado River bed is continuous and is typically greater than 10 m thick through much of its length. Sediment thickness in some areas exceeds 35 m while the smaller tributary valleys typically are filled with less than 4 m of sediment. Away from the river beds that are now covered with post-impoundment sediment, pre-impoundment alluvial deposits and rock outcrops are still exposed on the lake floor. Purpose: This GIS (ESRI) grid represents the integration of three datasets collected in 1999-2001 and represents the sediment thickness in Lake Mead as mapped with seismic-reflection equipment. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 19990514 Ending_Date: 20010426 Currentness_Reference: ground condition Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -114.875723 East_Bounding_Coordinate: -114.024827 North_Bounding_Coordinate: 36.485050 South_Bounding_Coordinate: 36.012414 Keywords: Theme: Theme_Keyword_Thesaurus: General Theme_Keyword: ArcView Theme_Keyword: CMGP Theme_Keyword: Coastal and Marine Geology Program Theme_Keyword: isopach Theme_Keyword: OFR03-320 Theme_Keyword: Open-File report Theme_Keyword: sediment Theme_Keyword: sediment thickness Theme_Keyword: TIFF Theme_Keyword: U.S. Geological Survey Theme_Keyword: USGS Theme_Keyword: Woods Hole Field Center Place: Place_Keyword_Thesaurus: General Place_Keyword: Arizona Place_Keyword: Black Canyon Place_Keyword: Boulder Basin Place_Keyword: Colorado River Place_Keyword: Gregg Basin Place_Keyword: Hoover Dam Place_Keyword: Iceberg Canyon Place_Keyword: Lake Mead Place_Keyword: Las Vegas Place_Keyword: Las Vegas Bay Place_Keyword: Las Vegas Wash Place_Keyword: Mojave Desert Place_Keyword: Nevada Place_Keyword: Overton Arm Place_Keyword: United States Place_Keyword: Virgin Basin Place_Keyword: North America Access_Constraints: NONE Use_Constraints: The U.S. Geological Survey must be referenced as the originator of the dataset in any future products or research derived from these data. Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: David C. Twichell Contact_Organization: U.S. Geological Survey Contact_Position: Oceanographer Contact_Address: Address_Type: mailing and physical address Address: 384 Woods Hole Rd. City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Contact_Voice_Telephone: (508) 548-8700 x2266 Contact_Facsimile_Telephone: (508) 457-2310 Contact_Electronic_Mail_Address: dtwichell@usgs.gov Native_Data_Set_Environment: Microsoft Windows 2000 Version 5.0 (Build 2195) Service Pack 4; ESRI ArcCatalog 8.2.0.700 Cross_Reference: Citation_Information: Originator: H.E. Bevans Originator: S.L. Goodbred Originator: J.F. Miesner Originator: S.A. Watkins Originator: T.S. Gross Originator: N.D. Denslow Originator: T. Choeb Publication_Date: 1996 Title: Synthetic organic compounds and carp endrocrinology and histology, Las Vegas Wash and Las Vegas and Callville bays of Lake Mead Nevada Series_Information: Series_Name: Water-Resources Investigations Issue_Identification: 96-4266 Publication_Information: Publisher: U.S. Geological Survey Cross_Reference: Citation_Information: Originator: H.E. Bevans Originator: M.S. Lico Originator: S.J. Lawrence Publication_Date: 1998 Title: Water quality in the Las Vegas Valley area and the Carson and Truckee River basins, Nevada and California, 1992-1996 Series_Information: Series_Name: Circular Issue_Identification: 1170 Publication_Information: Publisher: U.S. Geological Survey Cross_Reference: Citation_Information: Originator: K.J. Couvay Originator: T.J. Leiker Publication_Date: 1998 Title: Synthetic organic compounds in water and bottom sediment from streams, detention basins, and sewage-treatment plant outfalls in Las Vegas Valley, Nevada, 1997 Series_Information: Series_Name: Open-File Report Issue_Identification: 98-633 Publication_Information: Publisher: U.S. Geological Survey Cross_Reference: Citation_Information: Originator: H.R. Gould Publication_Date: 1951 Title: Some quantitative aspects of Lake Mead turbidity currents Series_Information: Series_Name: SEPM Special Publication Issue_Identification: No. 2 Publication_Information: Publisher: Society of Economic Paleontologists and Mineralogists Cross_Reference: Citation_Information: Originator: J.F. LaBounty Originator: M.J. Horn Publication_Date: 1997 Title: The influence of drainage from the Las Vegas Valley on the limnology of Boulder Basin, Lake Mead, Arizona-Nevada Series_Information: Series_Name: Journal of Lake and Reservoir Management Issue_Identification: v. 13 Cross_Reference: Citation_Information: Originator: L.J. Paulson Publication_Date: 1981 Title: Nutrient management with hydroelectric dams on the Colorado River Series_Information: Series_Name: Technical Report Issue_Identification: #8 Publication_Information: Publication_Place: Department of Biological Sciences, University of Nevada, Las Vegas, Nevada Publisher: Lake Mead Limnological Research Center Cross_Reference: Citation_Information: Originator: A.M. Preissler Originator: G.A. Roach Originator: K.A. Thomas Originator: J.W. Wilson Publication_Date: 1998 Title: Water resources data, Nevada, water year 1998 Series_Information: Series_Name: Water Resources Data Nevada Issue_Identification: NV-98-1 Publication_Information: Publisher: U.S. Geological Survey Data_Quality_Information: Logical_Consistency_Report: This isopach map represents the integration of three years of data collection. This time frame of data collection can introduce small discrepancies in the sediment thickness. Completeness_Report: This dataset is complete for the time period it covers. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: The navigation system used was a P-Code GPS system. Navigation was interpolated over as much as a 10 second interval, converted to UTM zone 11 coordinates and rounded to the nearest meter. Quantitative_Horizontal_Positional_Accuracy_Assessment: Horizontal_Positional_Accuracy_Value: 10-20m Horizontal_Positional_Accuracy_Explanation: Nominal accuracy for the system and including rounding errors. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: The nominal resolution of the chirp subbottom system is assumed to be 0.5 meters. Another uncertainty is the speed of sound in sediment, which for this study is assumed to be 1500 m/sec. Due to the generally thin nature of the sediment cover, inaccuracies in the speed of sound are not thought to have a high impact. Quantitative_Vertical_Positional_Accuracy_Assessment: Vertical_Positional_Accuracy_Value: 0.5 meters Vertical_Positional_Accuracy_Explanation: acquisition system resolution Lineage: Process_Step: Process_Description: Seismic-reflecition profiles were interpreted in Landmark seismic interpretation software. The interpreted surfaces included the pre- and post-impoundment surfaces. Process_Step: Process_Description: A supplemental horizon was created within Landmark which is the difference between the pre-and post-impoundment surfaces. Process_Step: Process_Description: This thickness horizon was then exported from Landmark as X,Y,Z values in ASCII format. Process_Step: Process_Description: This ASCII X,Y,Z file was then imported into Earthvision software package. Within Earthvision, these discrete points were gridded using the default spline gridding technique of earthvision. Process_Step: Process_Description: The Earthvision grid was then exported as an X,Y,Z ASCII text file. Process_Step: Process_Description: The Earthvision ASCII text file was then reformatted using an AWK script into an ESRI ASCII grid format. Process_Step: Process_Description: The ESRI ASCII grid format was imported into ArcView and converted to the standard ESRI grid format. Process_Step: Process_Description: This grid was then clipped to the sediment limit shapefile. Process_Step: Process_Description: This UTM grid was then reprojected to the geographic coordinate system using ArcToolbox from ArcGIS version 8.2. Process_Step: Process_Description: This grid was then converted to a TIFF image maintaining the legend colors using the extension image_convert_georef.avx downloaded from the ESRI website. Process_Step: Process_Description: This 24-bit TIFF image was then converted to a paletted 8-bit image and saved with pack bit compression in Corel PhotoPaint version 11. Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Raster Raster_Object_Information: Raster_Object_Type: Pixel Row_Count: 1878 Column_Count: 3381 Vertical_Count: 1 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Geographic: Latitude_Resolution: 0.000252 Longitude_Resolution: 0.000252 Geographic_Coordinate_Units: Decimal degrees Planar: Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: row and column Coordinate_Representation: Abscissa_Resolution: 0.000252 Ordinate_Resolution: 0.000252 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 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: Band_1 Attribute: Attribute_Label: ObjectID 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: Value Attribute: Attribute_Label: Red Attribute: Attribute_Label: Green Attribute: Attribute_Label: Blue Distribution_Information: Distributor: Contact_Information: Contact_Person_Primary: Contact_Person: David C. Twichell Contact_Organization: U.S. Geological Survey Contact_Position: Oceanographer Contact_Address: Address_Type: mailing and physical address Address: 384 Woods Hole Rd. City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Contact_Voice_Telephone: (508) 548-8700 x2266 Contact_Facsimile_Telephone: (508) 457-2310 Contact_Electronic_Mail_Address: dtwichell@usgs.gov Resource_Description: Downloadable Data Distribution_Liability: These data were prepared by an agency of the United States Government. Neither the United States government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Although all data published in this report have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data, software, or related materials. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Transfer_Size: 0.149 Metadata_Reference_Information: Metadata_Date: 20031006 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: VeeAnn A. Cross Contact_Organization: U.S. Geological Survey Contact_Position: Marine Geologist Contact_Address: Address_Type: mailing and physical address Address: 384 Woods Hole Rd. City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Contact_Voice_Telephone: (508) 548-8700 x2251 Contact_Facsimile_Telephone: (508) 457-2310 Contact_Electronic_Mail_Address: vatnipp@usgs.gov 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