Nevada Water Science Center

Drilling in the Carbonate Aquifer, Clark County

Additional water supplies in east-central Nevada are currently being explored as potential locations for groundwater supply from the deep regional consolidated rock aquifers.

Understanding the potential to impact the regional groundwater potential is limited due to lack of deep wells that help define the geohydrologic systems in Southern Nevada.  Furthermore, federal resource managers require reliable information about the hydrogeologic framework, sources of water to springs, and chemical composition of spring waters to make informed decisions about maintaining and protecting water-dependent ecosystems in Clark County.

In order to further evaluate the hydrogeologic conditions in the regional groundwater aquifer in Clark County, and to provide needed information, deep wells that provide information relative to the regional groundwater flow system need to be installed in areas of critical concern.

Research Plan

This project includes the following activities:

  • Site Reconnaissance and Borehole Location: Conduct an active seismic geophysical survey to identify exact borehole installation location by predicting depth to competent rock. Drill sites will be located in areas where depth to bedrock is minimized.
  • Permits and Regulatory Information: provide technical expertise to assist in completion of any
    necessary paper-work, including state applications and National Environmental policy Act
    (NEPA) analysis and compliance, in order to procure the proper permits and licenses to drill
    monitoring wells in the regional carbonate aquifer.
  • Drilling: Drill boreholes in selected sites. Borehole drilling will be completed using
    mud rotary, air rotary or percussion methods.
  • Data: Data collected during this activity includes:
    • Lithology: Lithologic cuttings will be collected, evaluated and logged as drilling occurs.
    • Borehole Geophysics: Geophysical logs will be collected from each borehole upon
      completion of drilling.
  • Borehole Construction: Monitoring wells will be constructed in each borehole. perforated
    casing will be placed in the interpreted highest transmissive zone in the fractured carbonate
    rock.
  • Chemistry:Samples of groundwater will be collected upon completion of well
    construction and development and analyzed for various water-quality constituents. Samples will be collected and analyzed for inorganic compounds, isotopes, metals and radionuclides.
  • Water-level data: Water-levels will be collected periodically throughout the drilling
    activity and made available on NWISweb.
  • Post Drilling Data Analysis:
    • Cuttings will be analyzed and detailed lithology will be compiled and associated with surrounding and known surface geology.
    • Borehole geophysics will be compiled and used to assist hydrogeologic interpretation (i.e. fracture analysis, depositional contacts, permeable units, and types of sedimentary
      deposits).
  • Data Management: Data from each borehole will be entered into NWIS.
    • Well Completion Report: A lithologic log and general well description will be compiled
      and submitted to the Nevada State Engineers Office following the completion of each well.
    • Site Identification Numbers: Well designations will be assigned upon completion of each
      well. These IDs will be permanently linked to all data collected by the USGS in the NWIS
      database.
    • Well Technical Record: A comprehensive file of all data will be maintained at the USGS
      Nevada Water Science Center offices in Carson City, and Henderson, NV.
    • Publication: A report outlining the drilling activity and the results from data
      collection will be compiled and published at the project’s completion.

Background

Several valleys in east-central Nevada are currently being explored to ascertain their potential for
groundwater supply. Existing permits requesting 134,000 acre-feet/year of water from Spring, Snake, Cave, Dry Lake, and Delamar Valleys are being evaluated by the Nevada State Engineers office. In response, the Nevada State Engineer has ordered additional study of the regional carbonate-rock aquifer systems to assess potential impacts of groundwater withdrawals.

The regional consolidated carbonate-rock aquifers in Southern Nevada are believed to yield up to 160,000 acre-feet/year (Dettinger and others, 1995), and effects from pumping on the regional water-level surface are not clearly understood. Few deep wells with water-levels representative of the regional water-level surface exist; therefore, a quantitative analysis of the regional groundwater potential is limited. Additionally, the lack of wells completed in regional carbonate-rock aquifer systems limit the general understanding of effects on pumping within localized hydrogeologic settings. For example, additional data on water level changes across individual fault lines, groundwater withdrawal effects on springs, and the general chemical condition of groundwater would increase understanding of local conditions in the regional carbonate aquifer. Further evaluations of the direction of groundwater flow, in regional systems, provides valuable data that will enhance our understanding of water-balances in aquifer systems that are potentially impacted by pumping; sustain biologically-sensitive aquatic, riparian, and phreatophytic ecosystems; and/or discharge at springs, river drainages, and playa areas.

To address these issues, funds have been allocated through Round 5 of the Southern Nevada public Lands Act to install deep wells throughout Clark County and provide analysis that will assist the understanding of the condition and flow direction of the regional carbonate-rock aquifer systems. These additional deep wells will provide valuable hydrogeologic data including hydrogeologic framework and chemical composition of groundwater in deep aquifers. This information will assist Federal resource managers in making informed decisions about maintaining and protecting groundwater resources within Clark County.

Drilling in Clark County

Quick Facts

 

Location: Clark County, southern Nevada

Start Date: 2008

End Date: 2013

Cooperators: Bureau of Land Management

Contact Information

 

Jon Wilson

USGS Nevada Water Science Center

160 N. Stephanie St.

Henderson, NV 89074

phone: (702) 564-4540

Email: jwilson@usgs.gov

 

Abbreviations

 

NWIS: National Water Information System

 

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page Last Modified: May 1, 2012