Explanation of Geothermal Area Detailed Maps
For geothermal areas with multiple spring features that would not be adequately represented on the 1:750,000-scale state geothermal map, detailed maps were made of the areas using several databases. Digital (.tif) topographic maps were obtained from the UNR Keck library site and these were used to define areas for the detailed maps, which are not all at the same scale. The scale selected for each map depended on the number of features to be represented in an area. These files were used by cartographers to include relevant topographic and cultural features (e.g., roads) on the detailed maps.
Several data files were used to plot locations of geothermal features in ArcView:
Where sufficient data were available from the individual databases, all springs with a temperature of >10°C above average annual surface temperature and greater than 20°C, and those noted as warm or hot were retained in the database (see Houghton and others, 1975 for a map of mean annual surface temperatures). Wells with temperatures >10°C above average annual surface temperature, and with temperature gradients of >25°C/km were retained in the database. Thus, sites potentially useful for direct use applications (e.g., onion drying, aquaculture, spas, space heating, and gold heap leaching) are included on the map. Questionable records were eliminated from each database. Thermal waters encountered in mines are indicated with the well symbol.
- GEOTHERM (for Nevada) and other unpublished NBMG data, including locations digitized from 7.5' topographic maps -- Digitized wells and springs that were shown on the 7.5' topographic maps as warm or hot are included, as are those identified as thermal based on a record in GEOTHERM. Thermal gradients could not be calculated for many of the well records, but records were retained if the well temperature was >10°C above average annual surface temperature.
- SMU (David Blackwell) -- This dataset includes geothermal temperature and gradient data from exploration drill holes and heat flow holes. These data are maintained by the Geothermal Lab at Southern Methodist University. Wells with a gradient of <50°C/km and located in alluvium, playas, landslides or moraines were eliminated based on considerations of the variations in gradient between alluvium and bedrock expected in an area with the same heat flow (e.g., see Blackwell and Chapman, 1977). Location data for these alluvial units were taken from a digital version of the 1:500,000-scale state geologic map of (Stewart and Carlson, 1978). The subset of the data used in this work is located at GEOTHERM.
- Permitted Wells - This database is a list of all the geothermal wells in the files at the Nevada Bureau of Mines and Geology (NBMG). These files contain all the geothermal well information available at the Nevada Division of Minerals since they took over permitting such wells in 1985. UTM locations were obtained by plotting section information or distance from section line data provided in the permit application. Wells that were plotted using section or quarter section information only are identified as Permitted well (approx. location). Wells for which UTM locations were obtained by plotting them on maps based on noted distances from section lines are identified as Permitted well (measured). Temperatures are not known for all wells in this database. Not all wells have permit numbers assigned.
- Power plant and direct use application locations (unpublished data, L. Garside, R. Hess, and J. Snow) are shown separately on the maps.
The following points were all obtained from the GEOTHERM and digitized databases, and the significance and numbering of the points are described here.
Shape files were made of the data files in ArcView, and different views were produced for each detailed map area. These files were saved to .eps and cartographers produced publication quality maps in Adobe Illustrator.
- Spring (digitized) and Well (digitized) - These are accurate locations that were obtained by digitizing an actual spring or well located on the topographic map. These locations were assigned numbers from 1 to 3000 by Nevada Bureau of Mines and Geology personnel when the locations were digitized from the maps
- Spring (approx. location) and Well (approx. location) - The locations of these points are approximate because they were plotted on topographic maps by Township, Range and Section (and quarter, quarter section where that information was available). The location information for these points originated from GEOTHERM, Garside and Schilling (1979) and various other published sources, and the quality varies, in part because of the need to project Township, Range, and Section lines in areas where they were not shown on maps available at the time the information was recorded. The data records for these points generally include some other information from GEOTHERM or elsewhere such as a temperature, chemistry, or written observations. Because these locations are approximate, it is often not clear which spring in a group of springs should be associated with the data. In cases where there is only one spring or well in a section, the digitized and the "approx. location" points will have the same, accurate coordinates. These sites are labeled with numbers in the 70,000s.
Blackwell, D.D., and Chapman, D.S., 1977, Interpretation of geothermal gradient and heat flow data for Basin and Range geothermal systems: Geothermal Resources Council Transactions, v. 1, p. 19-20.
Garside, L.J., 1994, Nevada low-temperature geothermal resource assessment: Nevada Bureau of Mines and Geology Open-File Report 94-2.
Garside, L.J., and Schilling, J.H., 1979, Thermal waters of Nevada: Nevada Bureau of Mines and Geology Bulletin 91, 163 p.
GEOTHERM database: http://www.nbmg.unr.edu/geothermal/geochemdata/geotherm.htm.
Hess, R.H., 1999, Geothermal energy, in The Nevada mineral industry 1998: Nevada Bureau of Mines and Geology Special Publication MI-1998, p. 42-44.
Houghton, J.G., Sakamoto, C.M., and Gifford, R.O., 1975, Nevada's weather and climate: Nevada Bureau of Mines and Geology Special Publication 2, 84 p.
Permitted wells database. (http://www.nbmg.unr.edu/geothermal/mapfiles/nvgeowel.txt)
SMU (Southern Methodist University) David Blackwell database, web site: http://www.smu.edu/geothermal/georesou/nevada.htm.
Stewart, J.H., and Carlson, J.E., 1978, Geologic map of Nevada: U.S. Geological Survey Map, 1:500,000.
Trexler, D.T., Flynn, T., Koenig, B.A., and Ghusn, G., Jr., 1983, Geothermal Resources of Nevada: Map produced by the National Geophysical Data Center, National Oceanic and Atmospheric Administration for the Geothermal and Hydropower Technologies Division, U.S. Department of Energy, 1 map.
National WATer Data STOrage and REtrieval System (WATSTORE) data for Nevada. U.S. Geological Survey. http://waterdata.usgs.gov/nwis.