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Professional Paper 1771

Prepared in cooperation with the U.S. Department of Energy, National Nuclear Security Administration, Nevada Site Office, Office of Environmental Management under Interagency Agreement, DE-A152-07NA28100U.

Groundwater Flow Systems at the Nevada Test Site, Nevada: A Synthesis of Potentiometric Contours, Hydrostratigraphy, and Geologic Structures

By Joseph M. Fenelon, Donald S. Sweetkind, and Randell J. Laczniak

Thumbnail of and link to report PDF (10.4 MB)Abstract

Contaminants introduced into the subsurface of the Nevada Test Site by underground nuclear testing are of concern to the U.S. Department of Energy and regulators responsible for protecting human health and safety. The potential for contaminant movement away from the underground test areas and into the accessible environment is greatest by groundwater transport. The primary hydrologic control on this transport is evaluated and examined through a series of contour maps developed to represent the hydraulic-head distribution within each of the major aquifers underlying the area. Aquifers were identified and their extents delineated by merging and analyzing multiple hydrostratigraphic framework models developed by other investigators from existing geologic information. A map of the hydraulic-head distribution in each major aquifer was developed from a detailed evaluation and assessment of available water-level measurements. Multiple spreadsheets that accompany this report provide pertinent water-level and geologic data by well or drill hole.

Aquifers are mapped and discussed in general terms as being one of two types: alluvial–volcanic, or carbonate. Both aquifer types are subdivided and mapped as independent regional and local aquifers, based on the continuity of their component rock. Groundwater-flow directions, approximated from potentiometric contours that were developed from the hydraulic-head distribution, are indicated on the maps and discussed for each of the regional aquifers and for selected local aquifers. Hydraulic heads vary across the study area and are interpreted to range in altitude from greater than 5,000 feet in a regional alluvial–volcanic aquifer beneath a recharge area in the northern part of the study area to less than 2,300 feet in regional alluvial–volcanic and carbonate aquifers in the southwestern part of the study area. Flow directions throughout the study area are dominantly south-southwest with some local deviations. Vertical hydraulic gradients between aquifer types are downward throughout most of the study area; however, flow from the alluvial–volcanic aquifer into the underlying carbonate aquifer, where both aquifers are present, is believed to be minor because of an intervening confining unit. Limited exchange of water between aquifer types occurs by diffuse flow through the confining unit, by focused flow along fault planes, or by direct flow where the confining unit is locally absent.

Interflow between regional aquifers is evaluated and mapped to define major flow paths. These flow paths delineate tributary flow systems, which converge to form intermediate and regional flow systems. The implications of these flow systems in controlling transport of radionuclides away from the underground test areas at the Nevada Test Site are briefly discussed. Additionally, uncertainties in the delineation of aquifers, the development of potentiometric contours, and the identification of flow systems are identified and evaluated.

Eleven tributary flow systems and three larger flow systems are mapped in the Nevada Test Site area. Flow systems within the alluvial–volcanic aquifer dominate the western half of the study area, whereas flow systems within the carbonate aquifer are most prevalent in the southeastern half of the study area. Most of the flow in the regional alluvial–volcanic aquifer that moves through the underground testing area on Pahute Mesa is discharged to the land surface at springs and seeps in Oasis Valley. Flow in the regional carbonate aquifer is internally compartmentalized by major geologic structures, primarily thrust faults, which constrain flow into separate corridors. Contaminants that reach the regional carbonate aquifer from testing areas in Yucca and Frenchman Flats flow toward downgradient discharge areas through the Alkali Flat–Furnace Creek Ranch or Ash Meadows flow systems and their tributaries.

First posted January 25, 2010

  • Appendix 1 XLS (10.5 MB)
    Water levels measured in the Nevada Test Site area, 1941–2008.
  • Appendix 2 XLS (325 KB)
    Mean water levels, hydraulic heads, well characteristics, and selected water temperatures for wells used to develop potentiometric contours in the Nevada Test Site area.
  • Appendix 3 XLS (2 MB)
    Hydrostratigraphic units and subsurface hydrologic unit types for wells in the Nevada Test Site area, as projected from hydrostratigraphic framework models.
  • Plate 1 PDF (1.5 MB)
    Map showing location of boreholes with water-level measurments that were used to develop potentiometric contours in the Nevada Test Site area, Nevada.
  • Plate 2
    (Sheet 1 | PDF 375KB)
    (Sheet 2 | PDF 338KB)
    Hydrogeologic sections showing distribution of subsurface hydrologic unit types and designations of local and regional aquifer and confining units in the Nevada Test Site area, Nevada.
  • Plate 3 PDF (2.1 MB)
    Map showing predevelopment hydraulic heads and potentionmetric contours for the alluvial-volcanic aquifer in the Nevada Test Site area, Nevada.
  • Plate 4 PDF (2.15 MB)
    Map showing predevelopment hydraulic heads and potentiometric contours for the carbonate aquifer in the Nevada Test Site area, Nevada.
  • Plate 5 PDF (1.66 MB)
    Map showing groundwater flow systems of the regional alluvial-volcanic aquifer in the Nevada Test Site area, Nevada.
  • Plate 6 PDF (1.55 MB)
    Map showing groundwater flow systems of the regional carbonate aquifer in the Nevada Test Site area, Nevada.

For additional information contact:
Director, Nevada Water Science Center
U.S. Geological Survey
2730 N. Deer Run Road
Carson City, Nevada 89701

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Suggested citation:

Fenelon, J.M., Sweetkind, D.S., and Laczniak, R.J., 2010, Groundwater flow systems at the Nevada Test Site, Nevada: A synthesis of potentiometric contours, hydrostratigraphy, and geologic structures: U.S. Geological Survey Professional Paper 1771, 54 p., 6 pls.




Study Methods

Potentiometric Contours and Conceptualization of Flow

Limitations and Considerations


References Cited

Appendix 1. Water Levels Measured in the Nevada Test Site Area, Nevada, 1941–2008

Appendix 2. Mean Water Levels, Hydraulic Heads, Well Characteristics, and Selected Water Temperatures for Wells Used to Develop Potentiometric Contours in the Nevada Test Site Area

Appendix 3. Hydrostratigraphic Units and Subsurface Hydrologic Unit Types for Wells in the Nevada Test Site Area, as Projected from Hydrostratigraphic Framework Models

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