ASSESSMENT OF SELECTEDSPRINGS AND WELLS ANDIMPLICATIONS FOR RECHARGE INTHE PAHRUMP VALLEY ANDSPRING MOUNTAINS, NEVADAPaul ...
Sampling MethodologySample collection from springorifice, Wood Canyon springCollection of He sample in copper tubing
Sampling MethodologyMeasurement of field parametersCollection of unfiltered sample
Analyte Suite
Introduction• Conducted assessmentof springs in the SpringMountains and PahrumpValley in March2012, sampling ofsprings and...
Structural Setting• Mountain-block springs NE ofPahrump• 2 valley-floor springs “Hwy 160 FZ”• 2 valley-floor springs close...
Geologic Setting Modified from Workman et al. (2002)Spring Mountains:Proterozoicmetamorphic, clastic, andcarbonaterocks, P...
Sampling Scheme• Water samples from:• 4 valley springs• 6 mountain-block springs• 5 flowing artesian wells• 10 non-flowing...
Results:Mountain Block Springs• The mountain block springsflow from fractured bedrock• The northern five springsemerge fro...
Results:Mountain Block Springs II• Horse Spring Eastemerges from a N-Sfracture in Bonanza King• Rheocrene/fracturespring
Results: Valley Floor Springs• Valley-floor springs areassociated withmapped/inferred structurescutting alluvial formation...
Results:Valley Floor Springs II• Mound Spring iscaldron (hypocrene)spring• Artesian well drillednext to spring may haveres...
Results:Valley Floor Springs III• Stump Spring• Discharge alongPVFZ• Low discharge (0.2gpm)• Rheocrene spring
Results:Valley Floor Springs IV• Ivanpah Spring• Discharge along “Hwy160” FZ• Low discharge (0.3gpm)• Recently beganflowin...
Results: Well Sampling ProgramWells completed in alluvialbasin fill sediments sampledas part of this investigationBypassin...
Results:General Chemistry• Majority of samples• Ca-Mg-HCO3 water type• low TDS (200-400 mg/l)• Consistent with interaction...
Results:General Chemistry II – Nitrate,Arsenic and Fluoride results• Nitrate concentration in wellssampled ranged from 0.1...
Results: 3H• Flow W to SW, consistent withSpring Mtn. recharge• Estimate 5 to 9 TU inprecipitation in Pahrump areaprecipit...
Results: 3H cont.• Most northern mountain blocksprings show < 10-20 year oldrecharge• Central and western Pahrumpwells hav...
Results: PMC• Flow W to SW, consistent withSpring Mtn. recharge• PMC rather than apparent agereported as water has interac...
-110.0-105.0-100.0-95.0-90.0-85.0-14.50 -14.00 -13.50 -13.00 -12.50 -12.00 -11.50 -11.00d2H,o/ood18O, o/ooStump Spr MW Tib...
Results: d2H and d18O• Mostly consistent with high-elevation, fall-spring recharge• Wells and valley-floor springs are typ...
Results: 3He/4He• He samples collected from five springs• Grapevine, Horseshutem, and Crystal Springs were allconsistent w...
Conclusions• Recharge varies from < 10 to 20 years for most mountainfront springs to > 60 years for wells in western Pahru...
Conclusions continued• Discharge from Stump Spring and Mound Spring is fault-controlled• Stump Spring and Stump Spring mon...
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Assessment of Selected Springs and Wells in the Pahrump Valley and Western Spring Mountains, Nye Co., Nevada at Devil’s Hole Conference, Death Valley, Calif.

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GGI recently presented a paper providing results of a survey of Springs and wells in the Pahrump Valley, and springs in the Spring Mountains to evaluate sources and timing of recharge to the Pahrump Valley aquifer. GGI Senior Geologist Paul Drakos presented this study, which was conducted in conjunction with the Nye County Nuclear Waste Repository Office (NWRPO) and the University of New Mexico (UNM). The alluvial aquifer is the main source of water for municipal, domestic, and irrigation wells in the valley. In addition, spring discharge has been utilized for irrigation, mining and domestic uses but also maintains critical habitat. Water samples were analyzed for major anions and cations, hydrogen, oxygen and carbon isotopes, and, for a subset, helium isotopes.

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Assessment of Selected Springs and Wells in the Pahrump Valley and Western Spring Mountains, Nye Co., Nevada at Devil’s Hole Conference, Death Valley, Calif.

  1. 1. ASSESSMENT OF SELECTEDSPRINGS AND WELLS ANDIMPLICATIONS FOR RECHARGE INTHE PAHRUMP VALLEY ANDSPRING MOUNTAINS, NEVADAPaul Drakos1, Roger McRae2, Meghan Hodgins1, JohnKlenke2, William Howard2, Levi Kryder2, Laura Crossey3,and Karl Karkstrom31Glorieta Geoscience, Inc.Santa Fe, NM 87502www.glorietageo.com2Nye County Nuclear Waste Repository Project OfficePahrump, NV 89048www.nyecounty.com3Department of Earth and Planetary Sciences,University of New Mexico, Albuquerque, NM, 87131
  2. 2. Sampling MethodologySample collection from springorifice, Wood Canyon springCollection of He sample in copper tubing
  3. 3. Sampling MethodologyMeasurement of field parametersCollection of unfiltered sample
  4. 4. Analyte Suite
  5. 5. Introduction• Conducted assessmentof springs in the SpringMountains and PahrumpValley in March2012, sampling ofsprings and wells toevaluate rechargesources, timing ofrecharge, and toimprove the hydrologiccharacterization of thearea
  6. 6. Structural Setting• Mountain-block springs NE ofPahrump• 2 valley-floor springs “Hwy 160 FZ”• 2 valley-floor springs close to state-line fault• NW trending Pahrump Valley faultzone (PVFZ) (part of the State LineFault Zone) likely controls StumpSpring/Mound Spring discharge• Wheeler Pass Thrust (WPT) animportant NNE trending fault• Mountain front normal faults (WestSpring Mountains Fault Zone;WSMFZ) bound the east side of thebasin north of the Wheeler Passthrust
  7. 7. Geologic Setting Modified from Workman et al. (2002)Spring Mountains:Proterozoicmetamorphic, clastic, andcarbonaterocks, Paleozoic andMesozoic clastic andcarbonate rocksPahrump Valley: Tertiary
  8. 8. Sampling Scheme• Water samples from:• 4 valley springs• 6 mountain-block springs• 5 flowing artesian wells• 10 non-flowing wells• Analyzed for:• major anions and cations• hydrogen, oxygen and carbon isotopes• helium isotopes (subset)• Spring assessment included:• Geologic and geomorphic mapping• Measurement of spring discharge• Measurement of field water quality parameters• Spring classification based on Springer et al. (2008)
  9. 9. Results:Mountain Block Springs• The mountain block springsflow from fractured bedrock• The northern five springsemerge from highly fracturedor mylonitized quartzite ofthe Johnnie Fm, StirlingQuartzite, Wood Canyon Fm• The springs were classifiedas Rheocrene (emerges instream channel) or hillslopesprings• Q between 1 and 15 gpmHorseshutem Spring emerges from baseof sheer zone along normal fault
  10. 10. Results:Mountain Block Springs II• Horse Spring Eastemerges from a N-Sfracture in Bonanza King• Rheocrene/fracturespring
  11. 11. Results: Valley Floor Springs• Valley-floor springs areassociated withmapped/inferred structurescutting alluvial formations• Ivanpah and Manse springslocated along Hwy 160 fault• Mound and Stump springslocated along State Line faultzone• Valley-floor springs classifiedas: limnocrene (emerges inpools), caldron,hypocrene/buried, andrheocrene• Q between 0.2 (Stump) and1000-1200 gpm (Manse)Manse Spring – Upper Pool
  12. 12. Results:Valley Floor Springs II• Mound Spring iscaldron (hypocrene)spring• Artesian well drillednext to spring may haveresulted in drying up ofspring orifice• Discharge west of PVFZ(possible splay?)• Well flow measured at2.3 gpm
  13. 13. Results:Valley Floor Springs III• Stump Spring• Discharge alongPVFZ• Low discharge (0.2gpm)• Rheocrene spring
  14. 14. Results:Valley Floor Springs IV• Ivanpah Spring• Discharge along “Hwy160” FZ• Low discharge (0.3gpm)• Recently beganflowing after severalyears dry
  15. 15. Results: Well Sampling ProgramWells completed in alluvialbasin fill sediments sampledas part of this investigationBypassing pressure tank to collectsample from non-flowing domesticwell after completion of purging.Assessment of artesian well forinclusion in sampling programUncased well providedkey data point in southernpart of study area
  16. 16. Results:General Chemistry• Majority of samples• Ca-Mg-HCO3 water type• low TDS (200-400 mg/l)• Consistent with interaction ofdolomite +/- limestone• Relatively short residencetime/interaction withcarbonate & silicate clasts• Exceptions - Higher TDSand/or SO4• Stump & Grapevine Springs• Harley & Fairgrounds Wells
  17. 17. Results:General Chemistry II – Nitrate,Arsenic and Fluoride results• Nitrate concentration in wellssampled ranged from 0.14 to0.57, with one sample 1.1 mg/l• With the exception of Horseshutem(1.2 mg/l) and Stump (2.97mg/l), springs exhibited < 1 mg/lnitrate• All wells and springs had As < 0.010mg/l. Maximum values 0.0041(Stump Spring) and 0.0047 (HarleyWell)• Fluoride < 1 mg/l at all locations• High nitrate and As generallycorrespond to higher sulfateStump SpringHarley Well
  18. 18. Results: 3H• Flow W to SW, consistent withSpring Mtn. recharge• Estimate 5 to 9 TU inprecipitation in Pahrump areaprecipitation• TU of >2 indicates <10-20 yearold recharge• TU or <1.5 indicates mixture ofmodern recharge with pre-1952recharge• TU of <0.8/non-detectabletritium indicates predominantlyor entirely pre-1952 recharge
  19. 19. Results: 3H cont.• Most northern mountain blocksprings show < 10-20 year oldrecharge• Central and western Pahrumpwells have 3H valuesindicating predominantly orentirely pre-1952 recharge• Mound and Stump Springshave relatively high 3H valuesof 0.9-1.2 TU (mixture ofmodern and pre-1952recharge)0.7-1.1
  20. 20. Results: PMC• Flow W to SW, consistent withSpring Mtn. recharge• PMC rather than apparent agereported as water has interactedwith old carbonate rocks• PMC data consistent with 3H data• PMC >80% suggest <20 years oldrecharge• PMC <20% suggest >60 years oldrecharge• Stump spring anomalously highPMC, in contrast to low PMC inStump Spring MW
  21. 21. -110.0-105.0-100.0-95.0-90.0-85.0-14.50 -14.00 -13.50 -13.00 -12.50 -12.00 -11.50 -11.00d2H,o/ood18O, o/ooStump Spr MW Tiberti Well USGS Dondi BiermeyerJeep Trail Fairgrounds Well West Mesquite DupeAW 34 Harley Well Trout Spring (average)*Santa Cruz Spring Crystal Spring Horseshutem SpringWood Canyon Spring Stump Spring Grapevine SpringHorse Spring East Ivanpah Spring Mound SpringManse Spring Hafen Artesian Well Munsen WellBowman Pond Artesian Well Pechstein Artesian Well VelozSpring Mts. Snow Melt* Spring Mts. Oct.-June Rain* GMWL (Craig, 1961)*Source: Winograd et al. (1998)Stump springStump spring MWResults: d2H and d18OMountain block springsMajority of valley floorsprings and wells
  22. 22. Results: d2H and d18O• Mostly consistent with high-elevation, fall-spring recharge• Wells and valley-floor springs are typically moredepleted, indicating higher elevation recharge thanmountain-block springs• Stump & Santa Cruz Springs have evaporative signatures• Stump spring MW much more depleted that Stump spring
  23. 23. Results: 3He/4He• He samples collected from five springs• Grapevine, Horseshutem, and Crystal Springs were allconsistent with an atmospheric He source and relativelyyoung recharge• Ivanpah Spring has 3He/4He ratio consistent with mantlehelium contribution to the sample, indicating that Ivanpahis a fault-controlled spring (“Hwy 160” fault)
  24. 24. Conclusions• Recharge varies from < 10 to 20 years for most mountainfront springs to > 60 years for wells in western Pahrump• High elevation, fall through spring recharge ispredominant recharge source.• Faults typically act as low-permeability barriers togroundwater flow in the Pahrump Valley.• Stump Spring shows anomalous general and isotopegeochemistry results
  25. 25. Conclusions continued• Discharge from Stump Spring and Mound Spring is fault-controlled• Stump Spring and Stump Spring monitoring well havedistinctly different geochemical signatures• Ivanpah Spring has 3He/4He ratio consistent with mantleHelium contribution, indicating that Ivanpah is also fault-controlled• Water quality in the Pahrump Valley in wells and springssampled in this study is excellent
  26. 26. QUESTIONS?

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