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Hydrogeology and Hydrogeochemistry of the Spring Mountains, Clark County, Nevada

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Hydrogeology and Hydrogeochemistry of the Spring Mountains, Clark County, Nevada UNLV Retrospective Theses & Dissertations 1-1-1989 Hydrogeology and hydrogeochemistry of the Spring Mountains, Clark County, Nevada Ronald Lee Hershey University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Hershey, Ronald Lee, "Hydrogeology and hydrogeochemistry of the Spring Mountains, Clark County, Nevada" (1989). UNLV Retrospective Theses & Dissertations. 66. http://dx.doi.org/10.25669/6jjj-tod5 This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. 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Ml 48106-1346 USA 313 761-4700 800 521-0600 Order Number 1839577 Hydrogeology and hydrogeochemistry of the Spring Mountains, Clark County, Nevada Hershey, Ronald Lee, M.S. University of Nevada, Las Vegas, 1989 UMI 300 N. Zeeb Rd. Ann Arbor, MI 48106 HYDROGEOLOGY AND HYDROGEOCHEMISTRY OF THE SPRING MOUNTAINS, CLARK COUNTY, NEVADA by Ronald Lee Hershey A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geoscience Department of Geoscience University of Nevada, Las Vegas December, 1989 The thesis of Ronald Lee Hershey for the degree of Master of Science Geosciences is approved. Chairpere em, Dr. John W. Hess Examining Committee Member, Dr. Richard H. French Examining Committee Member, Dr. Frederick W. Bachuber Graduate Faculty Representative, Dr. Boyd Earl Graduate Dean, Dr. Ronald W. Smith University of Nevada Las Vegas, Nevada December, 1989 ABSTRACT The Spring Mountains are the largest ground-water recharge area in southern Nevada and supply a significant amount of ground water to the Las Vegas, Pahrump, and Indian Springs Valleys. The mountain range, composed predominantly of highly fractured and faulted carbonate rock, is considered part of a regional carbonate aquifer system found in eastern Nevada. Because of the Spring Mountains recharge potential, their proximity to Las Vegas, and their interaction with the regional aquifer system, an understanding of the hydrogeology of the mountain range is vital. Isotopic and chemical analyses from 116 springs and wells in the mountain range and associated valleys indicate that ground water is generally of good quality, warm weather precipitation is recharging the ground-water system at higher elevations, and mixing of several ground-water masses including older regional water is occurring in the northern Las Vegas Valley. The high quality of ground water in the study area is controlled by the predominance of carbonate rock in the central portion of the mountain block. Water quality decreases as lithologies change to quartzite and shale in the north and to clastic and evaporite rocks in the south. Comparisons of average 8 D and 8 180 of ground water, snow, and rain in the study area suggest that a mixture of 40 percent rain and 60 percent snow is needed to derive ground water. A detailed study of 8D and 8 180 of precipitation and ground water at Deer Creek Spring #1 also suggest some summer precipitation is recharging the ground water system. 813C of high elevation springs suggest large amounts of recharge at higher elevations. Modeling of 8 t3C in ground water suggest low Pco2 anc^ enriched 8 13C in soil, and open system conditions at high elevations. Analysis of 14C in ground water and geochemical modeling of ground water using PHREEQE and BALANCE suggest that ground water from the Spring Mountain bedrock aquifer and alluvial-fan aquifers are mixing with water from the regional aquifer in the Las Vegas shear zone. Modeling also suggests mixing of 90 percent Las Vegas shear zone water with 10 percent water from the western portion of the Las Vegas Valley in the Las Vegas well field. TABLE OF CONTENTS ABSTRACT.............................................................................................................. iii LIST OF FIGURES ................................................................................................ vi LIST OF TABLES .................................................................................................. ix LIST OF ABBREVIATIONS ............................................................................... x ACKNOWLEDGEMENTS.................................................................................... xi INTRODUCTION................................................................................................... 1 Introduction ................................................................................................... 1 Objectives ....................................................................................................... 1 Approach ........................................................................................................ 2 Previous work ................................................................................................ 3 ENVIRONMENTAL SETTING ........................................................................... 6 Geography ....................................................................................................... 6 Climate ........................................................................................................... 9 Vegetation ....................................................................................................... 12 Geology ........................................................................................................... 13 Hydrogeology ................................................................................................. 19 HYDROGEOCHEMICAL THEORY .................................................................. 24 Geochemistry ................................................................................................. 24 Oxygen-18/Oxygen-16 and Deuterium/Hydrogen ................................. 27 Carbon-14 ............................................... 29 Carbon-13/Carbon-12 .................................................................................. 32 METHODS AND PROCEDURES ...................................................................... 40 Introduction ................................................................................................... 40 Ground-Water Sampling ............................................................................. 40 Snow Collection ............................................................................................ 41 Time Series Data Collection ....................................................................... 42 Chemical Analyses ....................................................................................... 44 Isotopic Analyses ........................................................................................... 45 RESULTS AND DISCUSSION ............................................................................ 46 Major Ion Geochemistry .............................................................................. 46 Stable Isotopes of Precipitation and Ground W ater ............................. 61 Carbon-14 in Ground Water ...................................................................... 75 Carbon-13/Carbon-12 in Ground Water ................................................. 78 iv Geochemical Modeling ...................................... 93 SUMMARY AND CONCLUSIONS ..................................................................... 108 FURTHER RESEARCH ......................... I l l BIBLIOGRAPHY ...................................................................................................
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