SIR 2020–5103: Simulated Effects of Pumping in the Death Valley

Prepared in cooperation with the Bureau of Land Management; National Park Service; Nevada Division of Wildlife; Nye County, Nevada; and U.S. Fish and Wildlife Service Simulated Effects of Pumping in the Death Valley Regional Groundwater Flow System, Nevada and California— Selected Management Scenarios Projected to 2120

a n a PAHUTE MESA– g a Groom t OASIS VALLEY R Range a Tikaboo n g Valley e

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Amargosa Desert Jackass R

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Amargosa Valley Specter Range Mercury Funeral Mountains

Indian Sheep Range Springs Furnace Creek Devils Hole ALKALI FLAT–

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Scientific Investigations Report 2020-5103

U.S. Department of the Interior U.S. Geological Survey Cover. Map of study area showing Alkali Flat–Furnace Creek Ranch, Ash Meadows, Bullfrog Hills, Pahrump to Death Valley South, and Pahute Mesa–Oasis Valley groundwater basins; and Nevada National Security Site boundary and internal operations area, in the Death Valley regional flow system, Nevada and California. Source: U.S. Geological Survey. Simulated Effects of Pumping in the Death Valley Regional Groundwater Flow System, Nevada and California—Selected Management Scenarios Projected to 2120

By Nora C. Nelson and Tracie R. Jackson

Prepared in cooperation with the Bureau of Land Management; National Park Service; Nevada Division of Wildlife; Nye County, Nevada; and U.S. Fish and Wildlife Service

Scientific Investigations Report 2020–5103

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior DAVID BERNHARDT, Secretary U.S. Geological Survey James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2020

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Suggested citation: Nelson, N.C., and Jackson, T.R., 2020, Simulated effects of pumping in the Death Valley Regional Groundwater Flow System, Nevada and California—Selected management scenarios projected to 2120: U.S. Geological Survey Scientific Investigations Report 2020–5103, 30 p., https://doi.org/10.3133/ sir20205103 .

Associated data for this publication: Nelson, N.C., and Jackson, T.R., 2020, MODFLOW-2005 models used to simulate effects of pumping in the Death Valley Regional Groundwater Flow System, Nevada and California—Selected management scenarios projected to 2120: U.S. Geological Survey data release, https://doi.org/10.5066/P9OBUPXU.

ISSN 2328-0328 (online) iii

Acknowledgments

The authors gratefully acknowledge the reviewers of this report for their helpful comments: Kyle W. Davis (U.S. Geological Survey [USGS]), Joseph M. Fenelon (USGS), Philip M. Gardner (USGS), Nina Hemphill (Bureau of Land Management [BLM]), John Klenke (Nuclear Waste Repository Project Office, Nye County, Nevada), Tim Mayer (U.S. Fish and Wildlife Service), Boris Poff (BLM), and Russel Scofield (BLM).

Contents

Acknowledgments ��iii Abstract ��1 Introduction ��1 Purpose and Scope ��5 Description of Study Area ��5 Death Valley Version 3 Predictive Model ��6 Pumping Scenarios ��6 Simulated Effects of Future Groundwater Pumping ��12 Regional Drawdown ��12 Base Case ��12 Scenario A ��18 Scenario B ��18 Scenario C ��23 Water Levels in Devils Hole ��23 Capture of Natural Discharge ��27 Amargosa Wild and Scenic River ��27 Ash Meadows Discharge Area ��28 Furnace Creek Area ��28 Stump Spring ��28 Summary ��28 References Cited ��29

Figures

1. Map showing study area with groundwater basins and hydraulic barriers, Death Valley regional flow system, Nevada and California ��3 2. Map showing study area including discharge areas, Death Valley regional flow system, Nevada and California ��4 3. Graph showing total annual pumping and return flow for the base case scenario and additional annual pumpage in scenarios A, B, and C, Death Valley regional flow system, Nevada and California ��7 4. Map showing location of pumping wells simulated in the base case scenario, Death Valley regional flow system, Nevada and California ��8 5. Map showing location of additional pumping wells in scenario A that were simulated together with the base case pumping wells, Death Valley regional flow system, Nevada and California ��9 6. Map showing location of additional pumping wells in scenario B that were simulated together with the base case pumping wells, Death Valley regional flow system, Nevada and California ��10 7. Map showing location of additional pumping wells in scenario C that were simulated together with the base case pumping wells, Death Valley regional flow system, Nevada and California ��11 8. Map showing water-level drawdown from predevelopment for base case scenario in 2020, Death Valley regional flow system, Nevada and California ��13 vi

9. Map showing water-level drawdown from predevelopment for base case scenario in 2040, Death Valley regional flow system, Nevada and California ��14 10. Map showing water-level drawdown from predevelopment for base case scenario in 2070, Death Valley regional flow system, Nevada and California ��15 11. Map showing water-level drawdown from predevelopment for base case scenario in 2120, Death Valley regional flow system, Nevada and California ��16 12. Map showing difference in water-level drawdown between the base case scenario in 2020 and 2120, Death Valley regional flow system, Nevada and California ��17 13. Graph showing groundwater withdrawals by water use in the Pahrump to Death Valley South groundwater basin from 1913 to 2020 (modified from Halford and Jackson, 2020) ��18 14. Map showing water-level drawdown from predevelopment for scenario A in 2120, Death Valley regional flow system, Nevada and California ��19 15. Map showing difference in water-level drawdown between the base case scenario and scenario A in 2120, Death Valley regional flow system, Nevada and California ��20 16. Map showing water-level drawdown from predevelopment for scenario B in 2120, Death Valley regional flow system, Nevada and California ��21 17. Map showing difference in water-level drawdown between the base case scenario and scenario B in 2120, Death Valley regional flow system, Nevada and California ��22 18. Map showing water-level drawdown from predevelopment for scenario C in 2120, Death Valley regional flow system, Nevada and California ��24 19. Map showing difference in water-level drawdown between the base case scenario and scenario C in 2120, Death Valley regional flow system, Nevada and California ��25 20. Hydrographs showing water levels in Devils Hole, southern Nevada ��26

Tables

1. Summary of pumping scenarios ��7 2. Simulated effects from four scenarios of groundwater pumping on natural discharge at select discharge areas, Death Valley regional flow system, Nevada and California ��27 vii

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain Length foot (ft) 0.3048 meter (m) mile (mi) 1.609 kilometer (km) Area acre 4,047 square meter (m2) acre 0.4047 hectare (ha) acre 0.4047 square hectometer (hm2) acre 0.004047 square kilometer (km2) square mile (mi2) 259.0 hectare (ha) square mile (mi2) 2.590 square kilometer (km2) Flow rate acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m3/yr) acre-foot per year (acre-ft/yr) 0.001233 cubic hectometer per year (hm3/yr) Transmissivity foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d)

Datums

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88). Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83). Altitude, as used in this report, refers to distance above the vertical datum.

Abbreviations

AFFCR Alkali Flat–Furnace Creek Ranch BLM Bureau of Land Management DV3-PRED Death Valley version 3 predictive model NNSS Nevada National Security Site PDVS Pahrump to Death Valley South PMOV Pahute Mesa–Oasis Valley USGS U.S. Geological Survey

Simulated Effects of Pumping in the Death Valley Regional Groundwater Flow System, Nevada and California— Selected Management Scenarios Projected to 2120

By Nora C. Nelson and Tracie R. Jackson

as the megachannel, greatly affecting water levels in the Ash Abstract Meadows discharge area. Scenario C resulted in an additional 10–100 ft of drawdown (compared to the base case) through- Declining water levels and reduced natural discharge at out the southeastern part of the Ash Meadows groundwater springs, seeps, and phreatophyte areas primarily are the result basin by 2120. Simulated drawdowns in Devils Hole in 2120 of decades of groundwater development in the Death Valley were 3.2, 3.4, 3.8, and 25.4 ft for the base case and scenarios regional flow system, in Nevada and California. A calibrated A, B, and C, respectively. The federally mandated minimum groundwater-flow model was used to simulate potential future water level for Devils Hole is 2.7 ft below a reference point. In effects of groundwater pumping on water levels and natural 2020, the simulated water level in Devils Hole was above the groundwater discharge in the study area. Effects of climate minimum water level, at 1.7 ft below the reference. Simulated change on future groundwater pumping were not considered water levels in Devils Hole fell below the federally mandated and were beyond the scope of the study. Four groundwater- water level by 2078, 2073, 2058, and 2025 for the base case pumping scenarios were developed by stakeholders to predict and scenarios A, B, and C, respectively, assuming a hypotheti- and compare (1) the extent of regional water-level declines; cal recharge scenario of constant natural recharge. Simulated (2) drawdown at Devils Hole; and (3) reductions in natural reductions in predevelopment (natural) discharge at select discharge at select discharge areas, including the Amargosa discharge areas ranged from 3 to 38 percent by 2120 for all Wild and Scenic River, the Ash Meadows discharge area, the scenarios. Amargosa Wild and Scenic River was the least Furnace Creek area, and Stump Spring. Scenarios were simu- affected discharge area with simulated capture rates ranging lated from 1913 to 2120, with historical pumping occurring from 3 to 4 percent of predevelopment discharge by 2120. Ash from 1913 to 2010, historical 2010 pumping rates projected Meadows discharge area was greatly affected by groundwater from 2010 to 2020, and scenario pumping beginning in 2020. pumping in scenario C with a simulated capture rate of 38 Pumping scenarios included a base case and scenarios A, B, percent, compared to simulated capture rates of 8, 8, and 9 and C. The base case projected 2010 pumping rates from 2010 percent for the base case, scenario A, and scenario B, respec- to 2120, and scenarios A, B, and C projected base case pump- tively, in 2120. Simulated capture rates in the Furnace Creek ing plus additional pumping at various locations from 2020 to area ranged from 10 to 11 percent for all scenarios in 2120. 2120. By 2020, historical (1913–2020) pumping resulted in Simulated capture rates at Stump Spring ranged from 32 to 36 the propagation of simulated drawdown of 1 foot (ft) or more percent for all scenarios in 2120. westward from Pahrump Valley to areas north of Shoshone in the Pahrump to Death Valley South (PDVS) groundwater basin and the merging of simulated 1-ft drawdown contours between the Alkali Flat–Furnace Creek Ranch (AFFCR) and Introduction Ash Meadows groundwater basins. In the base case scenario, extent and magnitude of simulated drawdown continued to Declining water levels and reduced natural discharge at increase in the Ash Meadows and AFFCR groundwater basins springs, seeps, and phreatophyte areas primarily are the result from 2020 to 2120. In the base case, the magnitude of simu- of decades of groundwater development in the Death Valley lated drawdown continued to increase in western Pahrump regional flow system, in Nevada and California Halford( and Valley from 2020 to 2120, whereas simulated water levels Jackson, 2020). A calibrated groundwater-flow model Halford( rose in eastern Pahrump Valley from 2020 to 2070 and then and Jackson, 2020; Jackson and Halford, 2020) was used to stabilized from 2070 to 2120. Scenarios A and B primar- simulate potential future effects of groundwater pumping on ily affected the PDVS and AFFCR groundwater basins by water levels and natural groundwater discharge in the study increasing the magnitude of drawdown in 2120, compared to area for four pumping scenarios developed by stakeholders. the base case. In scenario C, drawdown propagated through- Effects of climate change on future groundwater pumping out a high-transmissivity part of the carbonate aquifer known were not considered and were beyond the scope of the study. 2 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

The study area includes four groundwater basins within that a minimum pool elevation is maintained in Devils Hole the Death Valley regional flow system Harrill( and others, (Williams and others, 1996). The mandated minimum pool 1988) in southwestern Nevada and southeastern California elevation is 2.7 ft below a reference point in Devils Hole and (fig. 1). The four groundwater basins include Pahute Mesa– was established without differentiating between water-level Oasis Valley (PMOV), Alkali Flat–Furnace Creek Ranch changes that are due solely to pumping or to a combination of (AFFCR), Ash Meadows, and Pahrump to Death Valley South pumping and climate (Williams and others, 1996). Therefore, (PDVS; fig. 1). Declining water levels and reduced natural dis- water-level changes in Devils Hole from natural stresses charge at some springs, seeps, and evapotranspiration areas are should be considered in addition to changes from pumping. the result of decades of groundwater development in this dry Groundwater pumping has caused declines in natural region (Halford and Jackson, 2020). This report was prompted groundwater discharge within the study area (Halford and by concern from local and Federal managers of the potential Jackson, 2020). Natural groundwater discharge occurs either future effects of groundwater pumping on water levels and by diffuse upward flow into shallow alluvium, where water natural groundwater discharge, with special regard to several is either evaporated or transpired by phreatophytes; or from federally protected groundwater-dependent ecosystems in the springs and seeps, some of which support perennial reaches of study area. the Amargosa River. The groundwater-discharge areas investi- Pahrump Valley and central Amargosa Desert histori- gated for this report are the Amargosa Wild and Scenic River, cally are the two primary pumping centers in the study area. the Ash Meadows discharge area, the Furnace Creek area, and Pahrump Valley and central Amargosa Desert have had Stump Spring (fig. 2). Natural discharge in the Amargosa Wild measured drawdowns of as much as 80 and 50 ft, respectively and Scenic River includes all discharge from springs and phre- (Halford and Jackson, 2020). Halford and Jackson (2020) also atophytes along a 33-mi perennial reach between Shoshone reported that groundwater pumping from central Amargosa and Dumont Dunes in California (fig. 2). The Ash Meadows Desert and Pahrump Valley affected areas of 300 and 600 discharge area includes Amargosa Flat, more than 30 springs mi2, respectively, based on the delineation of areas where and seeps at Ash Meadows, and evapotranspiration areas measured water levels declined at a rate greater than 0.1 ft per extending downgradient from springs (fig. 2). Furnace Creek decade. Continued groundwater pumping at current (estimated area groundwater discharge includes discharge from Texas, from 2010) rates in Pahrump Valley, the central Amargosa Nevares, and Travertine Springs; evapotranspiration from Desert, and other nearby pumping centers likely will increase phreatophytes on the alluvial fan; and water diverted from the magnitude and extent of regional drawdown. Effects of Furnace Creek Wash that would have discharged as evapo- groundwater pumping can include water-level declines; land transpiration on the alluvial fan before groundwater develop- subsidence; and capture from springs, streams, and phreato- ment (fig. 2; see Halford and Jackson [2020] for details). The phytic vegetation, which can adversely affect species that use four groundwater-discharge areas investigated in this report these groundwater-dependent ecosystems. These effects are of are federally protected: concern to a variety of land-, water-, and wildlife-management 1. The Ash Meadows discharge area, which contains agencies. Devils Hole, is within a detached unit of Death Valley A high-profile concern within the study area is the effect National Park; of pumping on the water level in Devils Hole in the Ash Meadows discharge area (fig. 2). Devils Hole is the exclusive 2. The Amargosa River between Shoshone and Dumont habitat of an endangered species, Cyprinodon diabolis (Devils Dunes in California is a designated National Wild and Hole pupfish). During the 1970s, groundwater development Scenic River (Interagency Wild and Scenic Rivers in the Ash Meadows discharge area by Cappaert Enterprises, Coordinating Council, 2018); formerly Spring Meadows, Inc., caused a 2.3-ft water-level decline in Devils Hole, which temporarily reduced the spawn- 3. The Furnace Creek area is within Death Valley National ing habitat of the Devils Hole pupfish Dudley( and Larson, Park; and 1976). The correlation of nearby pumping to water-level 4. Stump Spring is a designated Area of Critical declines in Devils Hole was sufficient evidence for the U.S. Environmental Concern (Bureau of Land Supreme Court, in the 1976 court case Cappaert v. United Management, 1998). States (426 U.S. 128), to limit pumping of groundwater so Introduction 3

11 11630 116 11530 115 318 EVD LIFRI Study area NYE CO.

P i c a 375

h h

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BULLFROG Timber Mountain ucca HILLS Flat

3 Pintwater Range D 93 e

ucca e

r Oasis Valley Mountain t

R eatty a n

g LINCOLN CO.

e e g

Three CLARK CO. n

a a Lakes Amargosa Desert Jackass R

d Valley e Flats e A l t i t m o a m p r y S o t s r a o Indian R margosa Springs iv e Valley r Specter Range ercury Valley 190 Funeral Mountains

Indian Sheep Range Springs 36 373 30 Furnace 95 reek Devils Hole (Subunit of Death Valley ALALI FLAT– National Park) EPLANATIN FURNACE DEATH Spring Mountains VALLEY CREE Hydraulic barrierArea Greenwater Range of low-permeability 15 NATIONAL RANCH Las Vegas rock at the water table PARK Valley Pahrump (Halford and Jackson, Las

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e (ackson and Halford, 127 r 2020) Dumont Dunes bservation site Base from U.S. Geological Survey digital data, 1:100,000. Hillshade from U.S. Geological Survey 1-arc second 0 10 20 MILES National Elevation Data. Universal Transverse Mercator Projection, one 11, North American Datum of 1983. 0 10 20 KILOMETERS

Figure 1. Study area with groundwater basins and hydraulic barriers, Death Valley regional flow system, Nevada and California. 4 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

11 11630 116 11530 115 318 Furnace Creek area Ash Meadows discharge area Amargosa Wild and Scenic River (AWSR) Nevares NYE CO.

Springs a

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30 n PAHUTE MESA– g e Groom Beginning of OASIS VALLE e g Range n Amargosa AWSR a Shoshone R d Flat e lt e B Rainier Mesa Furnace Texas Springs Devils HoleEmigrant 95 reek Valley

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e 127 r bservation site Dumont Spring or spring comple Dunes Base from U.S. Geological Survey digital data, 1:100,000. Hillshade from U.S. Geological Survey 1-arc second 0 10 20 MILES National Elevation Data. Universal Transverse Mercator Projection, one 11, North American Datum of 1983. 0 10 20 KILOMETERS

Figure 2. Study area including discharge areas, Death Valley regional flow system, Nevada and California. Introduction 5

Purpose and Scope 2017). Primary recharge locations for the study area include Pahute Mesa; the Spring Mountains; Timber Mountain; and The purpose of this report is to simulate four the Belted, Groom, Pahranagat, and Sheep Ranges. Natural groundwater-pumping scenarios to forecast (1) the extent of discharge occurs primarily along the Amargosa Wild and regional drawdowns; (2) drawdown in Devils Hole; and (3) Scenic River and in Ash Meadows discharge area, Furnace pumping-induced reductions in natural discharge from the Ash Creek area, Oasis Valley, and Pahrump Valley. Recharge gen- Meadows discharge area, the Furnace Creek area, Amargosa erally occurs in the northern and eastern parts of the study area Wild and Scenic River, and Stump Spring. A “base case” and discharge occurs in the southern and western parts of the pumping scenario simulates historical development from 1913 study area (fig. 1; Halford and Jackson, 2020). to 2010 and assumes that pumping continues at current (2010) The PDVS groundwater basin is hydraulically isolated, rates, with 2010 pumping rates projected through 2120. Three whereas the AFFCR and Ash Meadows groundwater basins additional groundwater-pumping scenarios (scenarios A, B, are hydraulically connected (Halford and Jackson, 2020). and C) were provided by the Bureau of Land Management; Low-permeability siliciclastic rocks in the northern part National Park Service; Nevada Division of Wildlife; Nye of the Spring Mountains and Resting Spring Range form County, Nevada; and U.S. Fish and Wildlife Service. Pumping a hydraulic barrier between Pahrump Valley and the Ash rates (magnitudes) and locations in scenarios A, B, and C were Meadows discharge area (fig. 1). Low-permeability rocks selected by cooperators to determine potential future effects in the Resting Spring Range, Greenwater Range, and Black of additional pumping through 2120 on federally protected, Mountains impede the propagation of drawdown from the groundwater-dependent ecosystems. The pumping rates and PDVS groundwater basin toward the central Amargosa Desert. locations provided are hypothetical and do not necessarily Instead, drawdowns from pumping in Pahrump Valley extend represent the water usage plans or forecasts of any of the listed westward and southwestward toward discharge areas along the agencies or of the U.S. Geological Survey. Amargosa Wild and Scenic River. Groundwater-pumping scenarios were simulated using The Ash Meadows and AFFCR groundwater basins are a previously developed numerical groundwater-flow model, hydraulically connected by a 2–5 mi wide corridor near well referred to as the Death Valley version 3 predictive model AD-4, referred to as the well AD-4 corridor (fig. 1; Halford (DV3-PRED; Halford and Jackson, 2020). The four scenarios and Jackson, 2020). The well AD-4 corridor is an area of simulate historical pumping from 1913 to 2010 in the PMOV, groundwater upwelling, as indicated by a potentiometric AFFCR, Ash Meadows, and PDVS groundwater basins. The high in water-level contours around well AD-4 that decreases base case scenario projects 2010 pumping rates through 2120; radially into the central Amargosa Desert (Walker and Eakin, the other three scenarios (A, B, and C) simulate the base case 1963, plate 3; Claassen, 1985). The hydraulic connection pumping plus additional pumping through 2120 from two or through the well AD-4 corridor allows groundwater from more of the following areas: the Amargosa Desert, Pahrump the Ash Meadows groundwater basin to move upward from Valley, Indian Springs area, and north of Ash Meadows dis- carbonate rocks into basin fill in the central Amargosa Desert. charge area. Drawdowns from pumping basin fill in the central Amargosa Desert have propagated through the well AD-4 corridor into carbonate rocks within the Ash Meadows groundwater basin Description of Study Area by 2018 (Halford and Jackson, 2020). In the Ash Meadows groundwater basin, drawdowns The 6,720,000-acre study area consists of four groundwa- propagate quickly and recover slowly in a hydrologic feature ter basins: PMOV, AFFCR, Ash Meadows, and PDVS (fig. 1). known as the megachannel (Halford and Jackson, 2020). The Altitudes in the study area range from 11,916 ft in the Spring megachannel is an areally extensive, highly transmissive fea- Mountains to −282 ft in Death Valley (Halford and Jackson, ture in carbonate rocks (fig. 1), where transmissivity exceeds 2020). Recharge occurs primarily in high-altitude areas (above 20,000 ft2/d. As delineated by Halford and Jackson (2020), 6,000 ft) because high-altitude areas receive higher rates of the megachannel extends from the Ash Meadows discharge precipitation than lower-altitude areas. Recharge principally area to the northern extent of Yucca Flat. The megachannel occurs after winters with greater-than-average precipitation, was delineated from interpretations of hydrochemical data at when spring snowmelt replenishes the soil reservoir beyond Ash Meadows springs and aquifer-test results in Yucca Flat its storage capacity, allowing downward percolation below the (Winograd and Pearson, 1976; Jackson, 2017; Jackson and root zone and into the groundwater system (Smith and others, Halford, 2020). 6 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

Death Valley Version 3 Predictive Model (2010) rates through 2120. The other three scenarios (A, B, and C) simulate the same historical pumping rates through The DV3-PRED model (Halford and Jackson, 2120 as the base case plus increased groundwater pumping 2020; Jackson and Halford, 2020) is a three-dimensional, from 2020 to 2120 within the AFFCR, Ash Meadows, and finite-difference, numerical groundwater-flow model (or) PDVS groundwater basins. The four pumping scenarios (MODFLOW–2005; Harbaugh, 2005). The DV3-PRED are summarized in table 1 and figure 3. Locations and rates of model simulates the effect of historical and future potential base case pumping wells are shown in figure 4. Locations and groundwater development in the Ash Meadows, AFFCR, rates of additional pumping wells used in scenarios A–C are PMOV, and PDVS groundwater basins (fig. 1). The model shown in figures 5–7 and are provided in the model archive domain is the areal extent of the four combined groundwater (Nelson and Jackson, 2020). basins. Historical groundwater development (1913–2010) The base case scenario simulates the effect of contin- was simulated with the MODFLOW Well package using ued pumping at current (2010) rates through 2120. A total of groundwater-withdrawal data compiled by Elliott and Moreo 970 wells were used to simulate annual pumping volumes of (2018). Historical annual groundwater withdrawals were simu- 37,873 acre-ft from 2010 to 2120 (table 1). The maximum lated from 1913 to 2010, and current (2010) pumping rates pumping rate from an individual well during the simula- were projected from 2010 to 2020. Capture-limited boundary tion period from 2010 to 2120 is 1,127 acre-ft/yr, which was conditions (Halford and Plume, 2011) were used to simulate pumped from a well open to basin fill in the central Amargosa discharges from springs and evapotranspiration areas. Capture Desert (fig. 4). The main pumping areas are in Pahrump is the decrease in discharge from springs and evapotranspi- Valley and the central Amargosa Desert. Notable pumping ration areas that is the result of pumping. Capture-limited also occurs near Indian Springs, Emigrant Valley, Furnace boundary conditions ensured that the total amount of discharge Creek, and Beatty and on the Nevada National Security Site captured from springs and evapotranspiration areas cannot (NNSS; fig. 4). exceed predevelopment discharges. Scenario A adds 222 wells to base case pumping, increas- Hydraulic properties in the DV3-PRED model were ing total (gross) pumping by 13 percent from 37,873 acre-ft/ distributed using a simplified hydrogeologic framework of car- yr (in the base case) to 42,609 acre-ft/yr (table 1). Domestic bonate rocks, volcanic rocks, basin fill, volcanic-sedimentary and municipal wells were added in Pahrump Valley, including rocks, and low-permeability granitic and siliciclastic rocks. three municipal wells pumping 667 acre-ft/yr and 216 domes- For each of these geologic units, heterogeneous hydraulic- tic wells pumping 3.4 acre-ft/yr (fig. 5). The Nevada State conductivity, specific-yield, and specific-storage distributions Engineer limits net consumptive use from domestic wells to were estimated from calibration of the model to predevelop- 0.5 acre-ft/yr (Geter, 2015, p. 2); however, domestic pump- ment (steady-state) and groundwater-development (transient) ing rates greater than 0.5 acre-ft/yr likely were provided by conditions. Measured water-level altitudes in wells, spring cooperators to simulate multiple domestic wells in the same pools, and evapotranspiration areas; transmissivity estimates model cell. Three pumping wells were added in the Amargosa from aquifer tests and specific capacity; drawdowns in wells Desert with pumping rates ranging from 500 to 1,000 acre-ft/ from pumping; and spring capture were compared to simulated yr (fig. 5). equivalents during model calibration (Halford and Jackson, Scenario B adds 226 wells to base case pumping, increas- 2020; Jackson and Halford, 2020). See Halford and Jackson ing total pumping by 6 percent from 37,873 to 39,963 acre-ft/ (2020) for detailed descriptions of model development and yr, compared to the base case (table 1). Scenario B includes calibration. the same locations of domestic and municipal wells in Pahrump Valley as scenario A (figs. 5–6), except that pumping rates are decreased by a factor of two for domestic (1.7 Pumping Scenarios acre-ft/yr) and municipal (333 acre-ft/yr) wells. Compared to scenario A, scenario B increases the number of wells in the Four groundwater-pumping scenarios were developed to Amargosa Desert from 3 to 5 but decreases the total pumping examine potential effects of future pumping on water levels in the Amargosa Desert from 2,000 to about 710 acre-ft/yr, and groundwater discharges in the study area. Each scenario with individual pumping rates in the Amargosa Desert ranging simulates historical pumping at annual rates from 1913 to from 7.5 to 500 acre-ft/yr (fig. 6). Unlike scenario A, scenario 2010 (Elliott and Moreo, 2018), and 2010 pumping rates are B has two new wells open to carbonate rock about 14 and 20 projected through 2020; therefore, pumping rates from 1913 mi northeast of Devils Hole, respectively. The carbonate well to 2020 are the same for all four scenarios. Future pumping closer to Devils Hole occurs within the megachannel, whereas scenarios begin in 2020 and are projected for 100 years to the farther well is about 2 mi east of the megachannel. These 2120. The base case scenario simulates future groundwater two carbonate wells have pumping rates of 5 acre-ft/yr (fig. 6). withdrawals by assuming that all pumping continues at current Introduction 7

Table 1. Summary of pumping scenarios.

[—, not applicable]

Total number of pumping wells Total pumpage from 2020 to 2120 Increase from base case pump- Pumping scenario from 2020 to 2120 (acre-feet per year) ing (percent) Base case 970 37,873 — A 1,192 42,609 13 B 1,196 39,963 6 C 1,203 73,587 94

80,000 EPLANATIN Base case 60,000 Scenario B Scenario A Scenario C Return flow

40,000

20,000

0 Groundwater withdrawals, in acre-feet per year −20,000 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100 2110 2120 Year

Figure 3. Total annual pumping and return flow for the base case scenario and additional annual pumpage in scenarios A, B, and C, Death Valley regional flow system, Nevada and California. 8 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

11 11630 116 11530 115 318 NYE CO.

P i c a 375

h h

r 3 R a a n 30 n a PAHUTE MESA– g g e a Groom t R OASIS VALLE e g Range a n n a g R e d e lt e Rainier Pahute Mesa B Mesa Emigrant ASH MEADOWS 95 Valley

BULLFROG ucca HILLS Flat

3 Pintwater Range D 93 e

ucca e

r Mountain t

eatty R a n

g LINCOLN CO.

Amargosa Desert e e g

Three CLARK CO. n

a a Lakes Jackass R

d Valley e Flats e l t i t A o m m p y a t S r r o o Indian s a margosa Springs R i Valley ercury v Specter Range Valley Funeral Mountains e 190 r

Sheep Range Indian Springs 36 Furnace 373 30 reek Devils Hole ALALI FLAT– EPLANATIN FURNACE Spring Mountains 95Etent of the mega- CREE channel (Halford and Greenwater Range 15 RANCH ackson,Las Vegas 2020) Etent ofValley the AD-4

Pahrump corridor (HalfordLas and R

e ackson, 2020)Vegas s

D t i

e n Groundwater basin

a g t

h S Nopah Range boundary (Halford and

p Black Mountains 582 r ackson, 2020) i n Chicago Valley

Pahrump g

Nevada National

R Valley

a Security Site n V g 36 a boundary and internal l e le A Shoshone m y PAHRUMP TO operations area a

r g s o A a DEATH VALLE Base case simulated s m a y a pumping well, in r W e l SOUTH l o i s l a acre-feet per year a d n V R a a i n a v R i ecopa d e n 0 to 5 r C r S i a INYO CO. n o NEVADA c f CALIFORNIA

e li n 5 to 50

a i SAN BERNADINO CO. c

i 50 to 500 v

e 127 r 500 to 5,000 Dumont Dunes bservation site Base from U.S. Geological Survey digital data, 1:100,000. Hillshade from U.S. Geological Survey 1-arc second 0 10 20 MILES National Elevation Data. Universal Transverse Mercator Projection, one 11, North American Datum of 1983. 0 10 20 KILOMETERS

Figure 4. Location of pumping wells simulated in the base case scenario, Death Valley regional flow system, Nevada and California. Introduction 9

11 11630 116 11530 115 318 NYE CO.

P i c a 375

h h

r 3 R a a n 30 n a PAHUTE MESA– g g e a Groom t R OASIS VALLE e g Range a n n a g R e d e lt e Rainier Pahute Mesa B Mesa Emigrant ASH MEADOWS 95 Valley

BULLFROG ucca HILLS Flat

3 Pintwater Range D 93 e

ucca e

r Mountain t

eatty R a n

g LINCOLN CO.

Amargosa Desert e e g

Three CLARK CO. n

a a Lakes Jackass R

d Valley e Flats e l t i t A o m m p y a t S r r o o Indian EPLANATIN s a margosa Springs R Etent of the mega- i Valley ercury v Specter Range Valley Funeral Mountains e channel (Halford and 190 r ackson, 2020) EtentSheep of Range the AD-4 Indian corridor (Halford and Springs 36 Furnace 373 ackson, 2020) 30 reek Groundwater basin Devils Hole boundary (Halford and ackson, 2020) ALALI FLAT– Nevada National FURNACE Security Site Spring Mountains 95 CREE boundary and internal Greenwater Range operations area 15 RANCH Las Vegas Base caseValley simulated

Pahrump pumping well,Las in R

e acre-feet perVegas year s

D t

e n

a g 0 to 5

t h S Nopah Range

p Black Mountains 5 to 50 582 r

i n Chicago Valley

Pahrump g 50 to 500

R Valley

n 500 to 5,000 V g 36 a l e le A Scenario A pumping well Shoshone m y PAHRUMP TO a

r simulated in additon to g s o A a DEATH VALLE s base case pumping m a y a r W e l SOUTH wells, in acre-feet per l o i sa l a d n year V R a a i n a v R i ecopa d e n 0 to 5 r C r S i a INYO CO. n o NEVADA c f CALIFORNIA

e li n 5 to 50

a i SAN BERNADINO CO. c

i 50 to 500 v

Figure 5. Location of additional pumping wells in scenario A that were simulated together with the base case pumping wells, Death Valley regional flow system, Nevada and California. 10 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

11 11630 116 11530 115 318 NYE CO.

P i c a 375

h h

r 3 R a a n 30 n a PAHUTE MESA– g g e a Groom t R OASIS VALLE e g Range a n n a g R e d e lt e Rainier Pahute Mesa B Mesa Emigrant ASH MEADOWS 95 Valley

BULLFROG ucca HILLS Flat

3 Pintwater Range D 93 e

ucca e

r Mountain t

eatty R a n

g LINCOLN CO.

Amargosa Desert e e g

Three CLARK CO. n

a a Lakes ! Jackass R

d Valley e Flats e l t i t A o m m p y a t S r r o o Indian EPLANATIN s a margosa Springs R Etent of the mega- i ! Valley ercury v Specter Range Valley Funeral Mountains e channel (Halford and 190 r ! ackson, 2020) ! ! EtentSheep of Range the AD-4 ! Indian corridor (Halford and 36 Springs ackson, 2020) Furnace 373 ! 30 reek Groundwater basin Devils Hole boundary (Halford and ackson, 2020) ALALI FLAT– Nevada National FURNACE Security Site Spring Mountains 95 CREE !!!!!!! boundary and internal Greenwater Range !!!!!!!!!! !!!!!!!!!!!!!! operations area 15 RANCH !!!!!!!!!!!!!!!! Las Vegas !!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!! Base caseValley simulated !!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!! pumping well, in !!!!!!!!!!!!!!!!!!!!! Pahrump Las R !!!!!!!!!!!!!!!!!!!!! ! !

e acre-feet perVegas year s !!!!!!!!!!!!!!!!!!! ! ! ! !

t !! ! ! ! !

e n !! ! ! ! !!!

a g !! ! ! ! ! ! ! 0 to 5

t S ! ! ! ! h Nopah Range ! ! ! !

p Black Mountains 5 to 50 582 r

i n Chicago Valley

Pahrump g 50 to 500

R Valley

n 500 to 5,000 V g 36 a l e le A Scenario B pumping well Shoshone m y PAHRUMP TO a

r simulated in addition to g s o A a DEATH VALLE s base case pumping m a y a r W e l SOUTH wells, in acre-feet per l o i sa l a d n year V R a a i n a v R i ecopa d e n 0 to 5 r C r S i a INYO CO. n o NEVADA c f CALIFORNIA

e li n 5 to 50

a i SAN BERNADINO CO. c

i 50 to 500 v

Figure 6. Location of additional pumping wells in scenario B that were simulated together with the base case pumping wells, Death Valley regional flow system, Nevada and California. Simulated Effects of Future Groundwater Pumping 11

11 11630 116 11530 115 EPLANATIN318 Etent of the megachannel (Halford and ackson, 2020) NYE CO. Etent of the AD-4 a w corridor (Halford and i c 375 h ackson, 2020)

3 R a Groundwater basin 30 n PAHUTE MESA– g e boundary (Halford and Groom OASIS VALLE e ackson, 2020) g Range n a Nevada National R d Security Site e lt boundary and internal e Rainier Pahute Mesa B Mesa operations area Emigrant 95 Valley ASH MEADOWS

BULLFROG ucca HILLS Flat

3 Pintwater Range D 93 e

ucca e

r Mountain t

eatty R a n

g LINCOLN CO.

Amargosa Desert e e g

Three CLARK CO. n

a a Lakes Jackass R

d Valley e Flats e l t i t A o m m p y a t S r r o o Indian s a margosa Springs R i Valley ercury v Specter Range Valley Funeral Mountains e 190 r

Sheep Range

36 373 Indian Furnace Springs 30 reek Devils Hole ALALI FLAT– FURNACE 95 Spring Mountains CREE RANCH Greenwater Range Base case simulated 15 pumpingLas Vegas well, in Valley acre-feet per year

Pahrump Las R

e 0 to 5 Vegas s

D t i

e n 5 to 50

a g

t h S Nopah Range

p 50 to 500 Black Mountains 582 r

i n Chicago Valley

Pahrump g 500 to 5,000 or more

R Valley

n Scenario C pumping well V g 36 a l e simulated in addition to le A Shoshone m y PAHRUMP TO base case pumping a

r g s wells, in acre-feet per o A a DEATH VALLE s m a y year a r W e l SOUTH l o i s l a 0 to 5 a d n V R a a i n a v R i ecopa d 5 to 50 e n r C r S i a INYO CO. n o NEVADA c f CALIFORNIA

e li 50 to 500

n a i SAN BERNADINO CO. c

R 500 to 5,000 i

e 127 r 5,000 or more Dumont Dunes bservation site Base from U.S. Geological Survey digital data, 1:100,000. Hillshade from U.S. Geological Survey 1-arc second 0 10 20 MILES National Elevation Data. Universal Transverse Mercator Projection, one 11, North American Datum of 1983. 0 10 20 KILOMETERS

Figure 7. Location of additional pumping wells in scenario C that were simulated together with the base case pumping wells, Death Valley regional flow system, Nevada and California. 12 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

Scenario C adds 233 wells to base case pumping, increas- all historical and future pumping that occurred from 1913 to ing total pumping to 73,587 acre-ft/yr, which is an increase 2120. Drawdown maps from predevelopment conditions have of 94 percent compared to the base case scenario (table 1). 1-ft drawdown thresholds; therefore, simulated drawdowns of Scenario C has the same locations and pumping rates for less than 1 ft are not shown. domestic and municipal wells in Pahrump Valley as scenario Drawdown difference maps are used to visually assess A. Scenario C includes only three new wells in the central small changes in drawdown between the pumping scenarios Amargosa Desert, each pumping at rates of 500 acre-ft/ and the base case. Drawdown difference maps have thresholds yr. Scenario C has the same locations as scenario B for two of 0.1 ft. For the base case scenario, the drawdown difference carbonate wells about 14 and 20 mi northeast of Devils Hole, map was computed by subtracting drawdown in 2120 from respectively; however, pumping rates are increased to 500 drawdown in 2020. Scenarios A, B, and C are compared to acre-ft/yr. Unlike the other scenarios, scenario C adds nine the base case by subtracting simulated drawdowns in each new wells in the carbonate aquifer in the Indian Springs area. scenario from drawdown in the base case. For example, the These nine wells account for most of the increased pumping in drawdown difference map for scenario A in 2120 is computed scenario C. At Indian Springs, seven high-capacity wells each by subtracting scenario A drawdowns in 2120 from base case pump 2,286 acre-ft/year; two wells pump at 7,239 acre-ft/yr, drawdowns in 2120. one just east of Indian Springs and the other to the northeast in Three Lakes Valley (fig. 7). Base Case In the PDVS groundwater basin, the maximum extent Simulated Effects of Future of simulated drawdown (1 ft or greater) remained relatively unchanged in 2120 compared to 2020 because effects from Groundwater Pumping historical pumping had propagated to all groundwater- discharge areas in the PDVS basin by 2020 (figs. 8–12). The following sections discuss DV3-PRED model Simulated effects of pumping in Pahrump Valley propa- results for each pumping scenario: simulated regional draw- gated downgradient into Chicago Valley and through the down, simulated water levels in Devils Hole, and simulated Resting Spring Range to discharge areas north of Shoshone, capture of natural discharge. Magnitude and extent of simu- California, by 2020 (fig. 8). Pumping in Pahrump Valley lated regional drawdown are presented for the base case as peaked in 1968 because of irrigation and decreased from the water-level drawdown from predevelopment in 2020, 2040, 1970s to 2010 (fig. 13) because of a transition from irrigation 2070, and 2120, and drawdown difference from 2020 in 2120. to use in domestic, industrial, municipal, and public supply. Magnitude and extent of simulated regional drawdown are The changes in pumping resulted in declining water levels presented for scenarios A, B, and C as water-level drawdown in western Pahrump Valley and rising water levels in eastern from predevelopment in 2120 and drawdown difference from Pahrump Valley from 1980 to 2019 (Halford and Jackson, the base case in 2120 for each respective scenario in 2120. 2020). Continued simulated pumping at 2010 rates for the Water levels in Devils Hole are presented using two hydro- base case scenario results in continued water-level declines graphs: (1) simulated drawdown only, and (2) combined in western and southern Pahrump Valley, whereas water water-level changes from natural stresses and pumping in each levels rise from 2010 to 2070 and then stabilize from 2070 to pumping scenario. Simulated capture of natural discharge is 2120 in eastern Pahrump Valley (figs. 9–11). From 2040 to presented for the following discharge areas: Amargosa Wild 2120, pumping in western Pahrump causes large drawdowns and Scenic River, Ash Meadows discharge area, Furnace between 50 and 100 ft through northern Pahrump Valley (figs. Creek area, and Stump Spring. 9–11) as pumping propagates toward low-permeability rock in the Spring Mountains (fig. 1). Regional Drawdown In the AFFCR and Ash Meadows groundwater basins, simulated drawdowns of less than 5 ft have merged between The magnitude and extent of simulated drawdown is pumping centers in the central Amargosa Desert, the NNSS, presented in the following sections. All drawdowns were Indian Springs, and the Ash Meadows discharge area by 2020 calculated using simulated hydraulic heads from model layer (fig. 8). By 2120, drawdown from the pumping center south 2 (layer 1 is 1 ft thick and was created for the purpose of of Beatty coalesces with the other merged pumping centers in estimating specific yield and simulating groundwater/surface- the Amargosa Desert, NNSS, and the Ash Meadows groundwater interaction [Halford and Jackson, 2020]). Simulated water basin (fig. 11). Areas of drawdown from pumping in drawdown maps are presented in two formats: drawdown the PMOV groundwater basin and Emigrant Valley remain from predevelopment conditions and drawdown differences. isolated from one another and from other areas of drawdown For example, a map of drawdown in 2120 from predevelop- through 2120. ment conditions is the simulated drawdown in year 2120 from Simulated Effects of Future Groundwater Pumping 13

11 11630 116 11530 115 EPLANATIN318 Area of groundwater discharge by evapotranspiration NYE CO.

a Simulated water-level w

i c 375drawdown in 2020 from h

3 R predevelopment, in feet

30 n PAHUTE MESA– g 1 to 5 e Groom OASIS VALLE e 5 to 10 g Range n a 10 to 50 R d e lt 50 to 100 e Rainier Pahute Mesa B 100 or more Mesa Emigrant 95 Valley ASH MEADOWS

BULLFROG ucca HILLS Flat

3 Pintwater Range D 93 e

ucca e

r Mountain t

R eatty a n

g LINCOLN CO.

e e g

Three CLARK CO. n

a a Lakes Amargosa Desert Jackass R

d Valley e Flats e A l t i t m o a m p r y S o t s r a o Indian R margosa Springs iv e Valley r Specter Range ercury Valley 190 Funeral Mountains

Sheep Range Indian Springs 36 Furnace 30 reek

Devils Hole 95 ALALI FLAT– 373 Spring Mountains Greenwater Range 15 FURNACE Las Vegas CREE Valley Pahrump

RANCH Las R

e Vegas s

D t

e n Pahrump

a g

t 582 h S Nopah Range Valley

p Black Mountains

i n Chicago Valley

PAHRUMP TO g Etent of the mega-

channel (Halford and a DEATH VALLE

n V g ackson, 2020) a 36 e SOUTH l A Stump le Shoshone m Etent of the AD-4 y Spring a r corridor (Halford and g s o A a s ackson, 2020) m a y a r W e l l Groundwater basin o i s l a a d n V R a a boundary (Halford and i n a v R i ecopa d e n r C r ackson, 2020) S i a INYO CO. n o NEVADA c f CALIFORNIA

e li Nevada National

n a i SAN BERNADINO CO. c

Security Site R

e boundary and internal 127 r operations area Dumont Dunes bservation site Base from U.S. Geological Survey digital data, 1:100,000. Hillshade from U.S. Geological Survey 1-arc second 0 10 20 MILES National Elevation Data. Universal Transverse Mercator Projection, one 11, North American Datum of 1983. 0 10 20 KILOMETERS

Figure 8. Water-level drawdown from predevelopment for base case scenario in 2020, Death Valley regional flow system, Nevada and California. 14 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

11 11630 116 11530 115 EPLANATIN318 Area of groundwater discharge by evapotranspiration NYE CO.

a Simulated water-level w

i c 375drawdown in 2040 from h

3 R predevelopment, in feet

30 n PAHUTE MESA– g 1 to 5 e Groom OASIS VALLE e 5 to 10 g Range n a 10 to 50 R d e lt 50 to 100 e Rainier Pahute Mesa B 100 or more Mesa Emigrant 95 Valley ASH MEADOWS

BULLFROG ucca HILLS Flat

3 Pintwater Range D 93 e

ucca e

r Mountain t

R eatty a n

g LINCOLN CO.

e e g

Three CLARK CO. n

a a Lakes Amargosa Desert Jackass R

d Valley e Flats e A l t i t m o a m p r y S o t s r a o Indian R margosa Springs iv e Valley r Specter Range ercury Valley 190 Funeral Mountains

Sheep Range Indian Springs 36 Furnace 30 reek

Devils Hole 95 ALALI FLAT– 373 Spring Mountains Greenwater Range 15 FURNACE Las Vegas CREE Valley Pahrump

RANCH Las R

e Vegas s Pahrump

D t

e n Valley

a g

t 582 h S Nopah Range

p Black Mountains

i n Chicago Valley

PAHRUMP TO g Etent of the mega-

channel (Halford and a DEATH VALLE

e li Nevada National

n a i SAN BERNADINO CO. c

Security Site R

Figure 9. Water-level drawdown from predevelopment for base case scenario in 2040, Death Valley regional flow system, Nevada and California. Simulated Effects of Future Groundwater Pumping 15

11 11630 116 11530 115 EPLANATIN318 Area of groundwater discharge by evapotranspiration NYE CO.

a Simulated water-level w

i c 375drawdown in 2070 from h

3 R predevelopment, in feet

30 n PAHUTE MESA– g 1 to 5 e Groom OASIS VALLE e 5 to 10 g Range n a 10 to 50 R d e lt 50 to 100 e Rainier Pahute Mesa B 100 or more Mesa Emigrant 95 Valley ASH MEADOWS

BULLFROG ucca HILLS Flat

3 Pintwater Range D 93 e

ucca e

r Mountain t

R eatty a n

g LINCOLN CO.

e e g

Three CLARK CO. n

a a Lakes Amargosa Desert Jackass R

d Valley e Flats e A l t i t m o a m p r y S o t s r a o Indian R margosa Springs iv e Valley r Specter Range ercury Valley 190 Funeral Mountains

Sheep Range Indian Springs 36 Furnace 30 reek

Devils Hole 95 ALALI FLAT– 373 Spring Mountains Greenwater Range 15 FURNACE Las Vegas CREE Valley Pahrump

RANCH Las R

e Vegas s Pahrump

D t

e n Valley

a g

t 582 h S Nopah Range

p Black Mountains

i n Chicago Valley

PAHRUMP TO g Etent of the mega-

channel (Halford and a DEATH VALLE

e li Nevada National

n a i SAN BERNADINO CO. c

Security Site R

Figure 10. Water-level drawdown from predevelopment for base case scenario in 2070, Death Valley regional flow system, Nevada and California. 16 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

11 11630 116 11530 115 EPLANATIN318 Area of groundwater discharge by evapotranspiration NYE CO.

a Simulated water-level w

i c 375drawdown in 2120 from h

3 R predevelopment, in feet

30 n PAHUTE MESA– g 1 to 5 e Groom OASIS VALLE e 5 to 10 g Range n a 10 to 50 R d e lt 50 to 100 e Rainier Pahute Mesa B 100 or more Mesa Emigrant 95 Valley ASH MEADOWS

BULLFROG ucca HILLS Flat

3 Pintwater Range D 93 e

ucca e

r Mountain t

R eatty a n

g LINCOLN CO.

e e g

Three CLARK CO. n

a a Lakes Amargosa Desert Jackass R

d Valley e Flats e A l t i t m o a m p r y S o t s r a o Indian R margosa Springs iv e Valley r Specter Range ercury Valley 190 Funeral Mountains

Sheep Range Indian Springs 36 Furnace 30 reek

Devils Hole 95 ALALI FLAT– 373 Spring Mountains Greenwater Range 15 FURNACE Las Vegas CREE Valley Pahrump

RANCH Las R

e Vegas s Pahrump

D t

e n Valley

a g

t 582 h S Nopah Range

p Black Mountains

i n Chicago Valley

PAHRUMP TO g Etent of the mega-

channel (Halford and a DEATH VALLE

e li Nevada National

n a i SAN BERNADINO CO. c

Security Site R

Figure 11. Water-level drawdown from predevelopment for base case scenario in 2120, Death Valley regional flow system, Nevada and California. Simulated Effects of Future Groundwater Pumping 17

11 11630 116 11530 115 EPLANATIN318 Area of groundwater discharge by evapotranspiration NYE CO.

w Difference in simulated

i c 375water-level drawdown h

3 R for the base case

a 30 n scenario between 2120 PAHUTE MESA– g e Groom and 2020, in feet OASIS VALLE e g Range 0.1 to 1 n a R 1 to 10 d e lt 10 to 100 e Rainier Pahute Mesa B Mesa 100 or more Emigrant 95 Valley ASH MEADOWS

BULLFROG ucca HILLS Flat

3 Pintwater Range D 93 e

ucca e

r Mountain t

R eatty a n

g LINCOLN CO.

e e g

Three CLARK CO. n

a a Lakes Amargosa Desert Jackass R

d Valley e Flats e A l t i t m o a m p r y S o t s r a o Indian R margosa Springs iv e Valley r Specter Range ercury Valley 190 Funeral Mountains

Sheep Range Indian Springs 36 Furnace 30 reek

Devils Hole 95 ALALI FLAT– 373 Spring Mountains Greenwater Range 15 FURNACE Las Vegas CREE Valley Pahrump

RANCH Las R

e Vegas s Pahrump

D t

e n Valley

a g

t 582 h S Nopah Range

p Black Mountains

i n Chicago Valley

PAHRUMP TO g Etent of the mega-

channel (Halford and a DEATH VALLE

n V g a ackson, 2020) 36 e SOUTH l A Stump le Shoshone m Etent of the AD-4 y Spring a r corridor (Halford and g s o A a s ackson, 2020) m a y a r W e l l o i Groundwater basin s l a a d n V R a a boundary (Halford and i n a v R i ecopa d e n r C r ackson, 2020) S i a INYO CO. n o NEVADA c f CALIFORNIA

e li n Nevada National

a i SAN BERNADINO CO. c

R Security Site

Figure 12. Difference in water-level drawdown between the base case scenario in 2020 and 2120, Death Valley regional flow system, Nevada and California. 18 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

50 EPLANATIN Water use in the Pahrump to Death Valley South 40 groundwater basin Irrigation Industrial, municipal, and public supply Domestic 30 Return flow

20 acre-feet per year

10 Projected Groundwater withdrawals, in thousands of

0 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 ear

Figure 13. Groundwater withdrawals by water use in the Pahrump to Death Valley South groundwater basin from 1913 to 2020 (modified from Halford and Jackson, 2020).

Simulated drawdown from the central Amargosa Desert The addition of three wells in the Amargosa Desert extends into the Furnace Creek area, Jackass Flats, and the increases simulated drawdowns above base case conditions megachannel by 2020 (fig. 8). The maximum drawdown in the throughout the Amargosa Desert and the Ash Meadows central Amargosa Desert increases from about 65 ft in 2020 groundwater basin (fig. 15). A new well pumping at 1,000 to about 120 ft in 2120. Continued pumping from the cen- acre-ft/yr south of Beatty induces about 75 ft of additional tral Amargosa Desert causes drawdown to propagate farther drawdown (fig. 15). Two wells in the central Amargosa Desert, westward and northward into the Furnace Creek area and which each pump at rates of 500 acre-ft/yr, induce about 9 and Jackass Flats between 2020 and 2120 (figs. 8–11). Drawdowns less than 1 ft of additional drawdown in the Amargosa Desert from pumping in the central Amargosa Desert, NNSS, and and megachannel, respectively (fig. 15). Indian Springs propagate into the megachannel, and due to the hydraulic connection through this transmissive zone (Halford and Jackson, 2020), result in drawdown in the Ash Meadows Scenario B discharge area. Drawdown in the megachannel increases from Pumping rates of the 219 new wells in Pahrump Valley roughly 2 to 4 ft from 2020 to 2120. The extent of drawdown were reduced by 50 percent in scenario B as compared to sce- in the Ash Meadows groundwater basin from pumping in the nario A. Total drawdown from predevelopment exceeded 100 central Amargosa Desert, NNSS, and Indian Springs increases ft in 2120 in western Pahrump (fig. 16). Although the extent to the north and east from 2020 to 2120, and drawdown of simulated additional drawdowns in the PDVS groundwater extends 20 mi along the Sheep Range by 2120. basin for scenarios A and B appears somewhat similar, reduc- ing the pumping rates in scenario B resulted in a smaller areal Scenario A extent of additional drawdowns exceeding 1 ft in the PDVS groundwater basin (fig. 17). In the PDVS groundwater basin, the addition of 216 The areal extent of drawdown difference from the base domestic wells and 3 municipal wells in Pahrump Valley case in the Amargosa Desert is smaller in scenario B (fig. 17), causes additional drawdown above simulated base case compared to scenario A (fig. 15). Scenario B simulates five conditions but does not noticeably increase the maximum new Amargosa Desert wells that pump a total of 710 acre-ft/yr drawdown extent in the PDVS groundwater basin (figs. 14 and less than the three new Amargosa Desert wells that pump and 15). Additional drawdown is the difference in drawdown a total of 2,000 acre-ft/yr in scenario A. For the Ash Meadows between a model scenario (A, B, or C) in 2120 and the base groundwater basin, two hypothetical wells that are in or near case in 2120. Scenario A results in an additional drawdown of the megachannel and a new hypothetical well near the well 1–10 ft throughout most of Pahrump Valley by 2120 (fig. 15). AD-4 corridor contribute to the maximum extent of simulated Moreover, simulated drawdown near municipal wells in additional drawdown. Compared to scenario A, the maximum Pahrump Valley increases by about 35 ft by 2120 (fig. 15). extent of simulated drawdown in scenario B propagated farther northward and eastward toward the Sheep Range. Simulated Effects of Future Groundwater Pumping 19

11 11630 116 11530 115 EPLANATIN318 Area of groundwater discharge by evapotranspiration NYE CO.

a Simulated water-level w

i c 375drawdown in 2120 from h

3 R predevelopment for

a 30 n scenario A, in feet PAHUTE MESA– g e Groom 1 to 5 OASIS VALLE e g Range n 5 to 10 a R d 10 to 50 e lt e Rainier 50 to 100 Pahute Mesa B Mesa 100 or more Emigrant 95 Valley ASH MEADOWS

BULLFROG ucca HILLS Flat

3 Pintwater Range D 93 e

ucca e

r Mountain t

R eatty a n

g LINCOLN CO.

e e g

Three CLARK CO. n

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d Valley e Flats e A l t i t m o a m p r y S o t s r a o Indian R margosa Springs iv e Valley r Specter Range ercury Valley 190 Funeral Mountains

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Figure 14. Water-level drawdown from predevelopment for scenario A in 2120, Death Valley regional flow system, Nevada and California. 20 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

11 11630 116 11530 115 EPLANATIN318 Area of groundwater discharge by evapotranspiration NYE CO.

a Difference in simulated w

i c 375water-level drawdown h

3 R between scenario A

a 30 n and the base case in PAHUTE MESA– g e Groom 2120, in feet OASIS VALLE e g Range 0.1 to 1 n a R 1 to 10 d e lt 10 to 100 e Rainier Pahute Mesa B Mesa Emigrant 95 Valley ASH MEADOWS

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Sheep Range Indian Springs 36 Furnace 30 reek

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Figure 15. Difference in water-level drawdown between the base case scenario and scenario A in 2120, Death Valley regional flow system, Nevada and California. Simulated Effects of Future Groundwater Pumping 21

11 11630 116 11530 115 EPLANATIN318 Area of groundwater discharge by evapotranspiration NYE CO.

a Simulated water-level w

i c 375drawdown in 2120 from h

3 R predevelopment for

a 30 n scenario B, in feet PAHUTE MESA– g e Groom 1 to 5 OASIS VALLE e g Range n 5 to 10 a R d 10 to 50 e lt e Rainier 50 to 100 Pahute Mesa B Mesa 100 or more Emigrant 95 Valley ASH MEADOWS

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Sheep Range Indian Springs 36 Furnace 30 reek

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Figure 16. Water-level drawdown from predevelopment for scenario B in 2120, Death Valley regional flow system, Nevada and California. 22 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

11 11630 116 11530 115 EPLANATIN318 Area of groundwater discharge by evapotranspiration NYE CO.

a Difference in simulated w

i c 375water-level drawdown h

3 R between scenario B

a 30 n and the base case in PAHUTE MESA– g e Groom 2120, in feet OASIS VALLE e g Range 0.1 to 1 n a R 1 to 10 d e lt 10 to 100 e Rainier Pahute Mesa B Mesa Emigrant 95 Valley ASH MEADOWS

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d Valley e Flats e A l t i t m o a m p r y S o t s r a o Indian R margosa Springs iv e Valley r Specter Range ercury Valley 190 Funeral Mountains

Sheep Range Indian Springs 36 Furnace 30 reek

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Figure 17. Difference in water-level drawdown between the base case scenario and scenario B in 2120, Death Valley regional flow system, Nevada and California Simulated Effects of Future Groundwater Pumping 23

Scenario C in Devils Hole by 2120 will be about 3.2 ft. Scenario A includes three new wells in basin fill in the Amargosa Desert, Scenario C simulates three new central Amargosa Desert which result in 3.4 ft of simulated drawdown (an additional wells that each pump 500 acre-ft/yr. Total drawdown from 0.2 ft compared to the base case) in Devils Hole by 2120 predevelopment exceeds 100 ft in 2120 in parts of Pahrump (fig. 20A). In scenario B, simulated drawdown in 2120 was Valley, the Amargosa Desert, central NNSS, and a large area in 3.8 ft (0.6 ft more than for the base case; fig. 20A). Pumping the Ash Meadows groundwater basin, extending through Three wells in or near the megachannel and in the well AD-4 cor- Lakes Valley (fig. 18). The magnitude and extent of additional ridor likely are responsible for much of the additional draw- drawdown in the central Amargosa Desert is similar between down in scenario B compared to the base case and scenario A. scenarios A (fig. 15) and C (fig. 19) because similar volumes Pumping of about 30,500 acre-ft/yr from nine new wells in the of groundwater are withdrawn from wells. Indian Springs area in scenario C substantially affected water Simulated additional drawdowns in the megachannel are levels in Devils Hole, resulting in a maximum simulated draw- substantially larger in scenario C (fig. 19) compared to sce- down of 25.4 ft at Devils Hole by 2120 (maximum drawdown narios A and B (figs. 15 and 17). In scenario C, two additional not shown in fig. 20A). Simulated groundwater pumping in the wells in or near the megachannel and nine new pumping wells Indian Springs area causes water-level drawdown to propagate in the Indian Springs area induce additional drawdowns that through the carbonate aquifer into the megachannel and down- propagate throughout the megachannel. The additional pump- gradient to Devils Hole. ing induces about 35 ft of additional drawdown in the mega- The DV3-PRED model simulates drawdown due to channel compared to the base case. pumping and does not have the capacity to simulate natural Total drawdown and drawdown difference from the base stresses (fig 20A); however, natural stresses such as recharge case in 2120 for scenario C show merged drawdowns of less and earthquakes have a substantial effect on water levels in than 5 ft between the PDVS and Ash Meadows groundwater Devils Hole (to as much as 0.8 ft from 1940 to 2018, fig. 20B). basins (figs. 18 and 19). A merged drawdown of less than 5 ft To accurately simulate the effect of natural stresses on water induced 30 acre/yr of simulated groundwater flow from PDVS levels in Devils Hole, the DV3-PRED model was modified to to Ash Meadows, which is 0.2 percent of the predevelopment include both natural and pumping-induced stresses. Previously discharge in the Ash Meadows discharge area (18,500 acre-ft/ simulated water-level fluctuations at Devils Hole due to natu- yr; Halford and Jackson, 2020). This result is speculative and ral stresses (Halford and others, 2012; Jackson and Halford, uncertain because of a lack of water-level data in wells to 2020) were combined with pumping-induced simulated constrain flow between Pahrump Valley and the Ash Meadows drawdowns using DV3-PRED to evaluate the effect of both discharge area. stresses on water levels in Devils Hole. Simulated water-level fluctuations caused by natural stresses and pumping compare Water Levels in Devils Hole reasonably well to observed water levels from 1940 to 2018 (fig. 20B) and provide an accurately simulated water-level For each model scenario, two Devils Hole hydrographs depth in 2018 to initiate model forecast scenarios from 2019 were constructed to show (1) the component of drawdown to 2120. However, forecasting future change in recharge (water-level decline) resulting from historical and future effects on water levels from 2019 to 2120 is highly uncer- pumping simulated using the DV3-PRED model (fig. 20A), tain and beyond the scope of this study. From 2019 to 2120, and (2) the combined water-level changes from fluctuations in a constant value was used to simulate year-to-year model natural stresses and pumping (fig. 20B). The combined effect recharge by assuming recharge to be equal to natural ground- of natural stresses and pumping on water levels in Devils water discharge (fig. 20B). A constant recharge approach, in Hole is needed to accurately forecast the timing of simulated essence, negates the effect of natural stresses and simulates water-level declines below the U.S. Supreme Court-mandated only pumping-induced water-level change from 2019 to 2120. minimal water level. Although not necessarily a realistic forecast of future climate The DV3-PRED model simulates drawdown in Devils effects on water levels in Devils Hole, the approach does Hole only due to pumping, from 1940 to 2120, and does not provide useful information on the general rate and timing of simulate natural stresses such as recharge (fig. 20A). Pumping- pumping-induced water-level change. The resulting simulated induced simulated drawdown in Devils Hole ranged from 3.2 water levels for all model scenarios were compared to the to 25.4 ft by 2120 (fig. 20A; simulated drawdown of 25.4 ft in U.S. Supreme Court-mandated minimum water level of 2.7 ft 2120 for scenario C not shown in fig. 20A). If pumping contin- below an established reference point in Devils Hole. ues at 2010 rates (the base case), then the simulated drawdown 24 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

11 11630 116 11530 115 EPLANATIN318 Area of groundwater discharge by evapotranspiration NYE CO.

a Simulated water-level w

i c 375drawdown in 2120 from h

3 R predevelopment for

a 30 n scenario C, in feet PAHUTE MESA– g e Groom 1 to 5 OASIS VALLE e g Range n 5 to 10 a R d 10 to 50 e lt e Rainier 50 to 100 Pahute Mesa B Mesa 100 or more Emigrant 95 Valley ASH MEADOWS

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d Valley e Flats e A l t i t m o a m p r y S o t s r a o Indian R margosa Springs iv e Valley r Specter Range ercury Valley 190 Funeral Mountains

Sheep Range Indian Springs 36 Furnace 30 reek

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Figure 18. Water-level drawdown from predevelopment for scenario C in 2120, Death Valley regional flow system, Nevada and California. Simulated Effects of Future Groundwater Pumping 25

11 11630 116 11530 115 EPLANATIN318 Area of groundwater discharge by evapotranspiration NYE CO.

a Difference in simulated w

i c 375water-level drawdown h

3 R between scenario C

a 30 n and the base case in PAHUTE MESA– g e Groom 2120, in feet OASIS VALLE e g Range 0.1 to 1 n a R 1 to 10 d e lt 10 to 100 e Rainier Pahute Mesa B Mesa 100 or more Emigrant 95 Valley ASH MEADOWS

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Figure 19. Difference in water-level drawdown between the base case scenario and scenario C in 2120, Death Valley regional flow system, Nevada and California 26 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

A 0 EPLANATIN Base case Scenario A Scenario B 1 Scenario C Change in Devils Hole water level from natural causes—dashed where unknown Measured 2

Simulated drawdown

Simulated drawdown, in feet 3 of 25.4 ft in 2120 for scenario C not shown

4 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100 2110 2120 B 0 ? Future natural ﬂuctuations from recharge are unknown but have a large effect on water levels −1

−2

U.S. Supreme Court-mandated −3 minimum water level Water-level depth below reference point, in feet Water-level

−4 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100 2110 2120 Year

Figure 20. Water levels in Devils Hole, southern Nevada. A, Simulated drawdowns for four pumping scenarios from the predictive Death Valley version 3 model (DV3-PRED). B, Measured (1940–2017) water-level depth below reference point, estimated (1940–2018) and projected (2019–2120) changes in Devils Hole water level from natural stresses, and summation of simulated drawdowns and natural water-level changes for four pumping scenarios. Simulated Effects of Future Groundwater Pumping 27

For all model scenarios simulated using a constant Capture of Natural Discharge recharge value, water levels in Devils Hole declined below the mandated minimum water level by 2120 (fig. 20B). The base Simulated discharges for the Amargosa Wild and Scenic case and scenarios A, B, and C water levels decline below River, the Ash Meadows discharge area, the Furnace Creek 2.7 ft by 2078, 2073, 2058, and 2025, respectively. However, area, and Stump Spring were computed using ZONEBUD- natural water-level fluctuations in the future (after 2019) may GET, a computer program for calculating subregional water influence the timing of when water levels decline below the budgets for MODFLOW groundwater-flow models (Harbaugh, mandated minimum water level. For example, an extended dry 1990). Simulated discharges and percentages of captured dis- period (less than average recharge) will accelerate the tim- charge for each of the four scenarios are presented in table 2. ing when water levels will drop below the mandated minimum water level, whereas an extended wet period (greater than average recharge) will prolong the timing. For scenario Amargosa Wild and Scenic River C, the relatively large simulated groundwater withdrawals The Amargosa Wild and Scenic River is the least affected have caused a steep decline of water levels in Devils Hole discharge area, by percentage of capture, examined for this (fig. 20A), compared to other model simulations. Under the report. The Amargosa Wild and Scenic River has a simulated higher pumping stress of scenario C, natural fluctuations predevelopment discharge of 6,700 acre-ft/yr (table 2; Halford would likely have a minimal effect on the timing of when and Jackson, 2020). The base case reduces simulated discharge water levels decline below the mandated minimum water level by 3 percent, and scenarios A, B, and C reduce simulated of 2.7 ft. For the base case, scenario A, and scenario B, the discharge by 4 percent by 2120. timing of when water levels will decline below the mandated minimum water level is much more dependent on future natural water-level fluctuations.

Table 2. Simulated effects from four scenarios of groundwater pumping on natural discharge at select discharge areas, Death Valley regional flow system, Nevada and California.

[Predevelopment discharge: Values are simulated values from Halford and Jackson (2020)]

Pre-develop- Simulated discharge Capture ment discharge Pumping (acre-feet per year) (percent) Discharge area (acre-feet scenario per year) 2020 2040 2070 2120 2020 2040 2070 2120 Amargosa Wild 6,700 Base case 6,500 6,500 6,500 6,500 3 3 3 3 and Scenic A 6,500 6,500 6,500 6,400 3 3 3 4 River B 6,500 6,500 6,500 6,400 3 3 3 4 C 6,500 6,500 6,500 6,400 3 3 3 4 Ash Meadows 18,500 Base case 17,900 17,800 17,500 17,100 3 4 5 8 discharge area A 17,900 17,800 17,500 17,000 3 4 5 8 B 17,900 17,600 17,400 16,900 3 5 6 9 C 17,900 16,200 14,000 11,500 3 12 24 38 Furnace Creek 6,300 Base case 5,800 5,800 5,700 5,700 8 8 10 10 area A 5,800 5,800 5,700 5,600 8 8 10 11 B 5,800 5,800 5,700 5,600 8 8 10 11 C 5,800 5,800 5,700 5,600 8 8 10 11 Stump Spring 250 Base case 180 180 180 170 28 28 28 32 A 180 180 170 160 28 28 32 36 B 180 180 170 160 28 28 32 36 C 180 180 170 160 28 28 32 36 28 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

Ash Meadows Discharge Area scenario simulated no additional groundwater development within the study area and simulated projected 2010 pumping Simulated predevelopment discharge from Ash Meadows rates through 2120. The other three scenarios (A, B, and C) discharge area is 18,500 acre-ft/yr (table 2; Halford and simulated base case pumping rates plus additional groundwa- Jackson, 2020). In the base case, simulated discharge is ter pumping from 2020 to 2120 within the Alkali Flat–Furnace reduced by 8 percent to 17,100 acre-ft/yr by 2120. Scenarios Creek Ranch (AFFCR), Ash Meadows, and (or) Pahrump to A and B induce the capture of 8 and 9 percent of predevelop- Death Valley South (PDVS) groundwater basins. ment discharge, respectively. In scenario C, simulated dis- By 2020, historical (1913–2020) pumping resulted in charge is reduced by 38 percent to 11,500 acre-ft/yr by 2120. the propagation of simulated drawdown of 1 foot (ft) or more Scenario C has a large effect on simulated discharge at Ash westward from Pahrump Valley to areas north of Shoshone Meadows discharge area. This is because, in scenario C, in the PDVS groundwater basin and the merging of simu- 1–10 ft of drawdown were induced in the megachannel from lated 1-ft drawdown contours between the AFFCR and Ash the high withdrawal rates near Indian Springs (fig. 18), Meadows groundwater basins. In the base case scenario, the whereas additional pumping in scenarios A and B induced less extent and magnitude of simulated drawdown continued to than 1 ft of drawdown (figs. 14 and 16). increase in the Ash Meadows and AFFCR groundwater basins from 2020 to 2120. In the base case, the magnitude of simu- Furnace Creek Area lated drawdown continued to increase in western Pahrump Valley from 2020 to 2120, whereas simulated water levels The Furnace Creek area has a simulated predevelopment rose in eastern Pahrump Valley from 2020 to 2070 and then discharge of 6,300 acre-ft/yr (table 2; Halford and Jackson, stabilized from 2070 to 2120. Scenarios A and B primar- 2020). The base case predicts a 10-percent reduction in prede- ily affected the PDVS and AFFCR groundwater basins by velopment discharge at Furnace Creek area by 2120. Scenarios increasing the magnitude of drawdown in 2120, compared to A, B, and C all predict an 11-percent reduction in predevelop- the base case. In scenario C, drawdown propagated through- ment discharge by 2120. out a high-transmissivity part of the carbonate aquifer known as the megachannel, greatly affecting water levels in the Ash Meadows discharge area. Scenario C resulted in an additional Stump Spring 10–100 ft of drawdown (compared to the base case) throughout the southeastern part of the Ash Meadows groundwater Simulated predevelopment discharge at Stump Spring basin by 2120. is 250 acre-ft/yr (table 2; Halford and Jackson, 2020). In the Simulated drawdown at Devils Hole in 2120 was 3.2, 3.4, base case, simulated discharge is reduced by 32 percent to 170 3.8, and 25.4 ft for the base case and scenarios A, B, and C, acre-ft/yr by 2120. Scenarios A, B, and C all reduce simulated respectively. Simulated water levels in Devils Hole fell below discharge by 36 percent to 160 acre-ft/yr. the federally mandated water level by 2078, 2073, 2058, and 2025 for the base case and scenarios A, B, and C, respectively, assuming a hypothetical case of constant natural recharge for Summary the period 2020—2120. In scenario A, pumping of about 2,000 acre-feet per year (acre-ft/yr) from three new Amargosa Desert Declining water levels and reduced natural discharge at wells results in an additional 0.2 ft of water-level decline in springs, seeps, and phreatophyte areas primarily are the result Devils Hole compared to the base case by 2120. In scenario B, of decades of groundwater development in the Death Valley pumping of about 710 acre-ft/yr is more than the base case in regional flow system, in Nevada and California. The calibrated the Amargosa Desert but less than the pumping from this area Death Valley version 3 predictive groundwater-flow model in scenario A. For the pumping level simulated in scenario was used to simulate four future groundwater-pumping scenar- B, simulated drawdown in Devils Hole is 0.2 ft greater than ios in the Death Valley regional flow system. The model was simulated drawdown in scenario A by 2120 because of the used to predict (1) the extent of regional water-level declines; proximity of the pumping to the megachannel. Scenario C (2) drawdown at Devils Hole; and (3) reductions in natural shows that high withdrawal rates (combined pumping of more discharge in the Amargosa Wild and Scenic River, the Ash than 30,000 acre-ft/yr) from the carbonate aquifer near Indian Meadows discharge area, the Furnace Creek area, and Stump Springs result in rapid declines in Devils Hole water levels and Spring. Each scenario simulates historical pumping at annual capture of a large fraction of groundwater in the Ash Meadows rates from 1913 to 2010, and historical 2010 pumping is discharge area. projected from 2010 to 2120. Future pumping scenarios begin in 2020 and are projected for 100 years to 2120. The base case References Cited 29

Reductions in natural discharge at select discharge areas Halford, K.J., and Jackson, T.R., 2020, Groundwater char- ranged from 3 to 38 percent by 2120. The four pumping sce- acterization and effects of pumping in the Death Valley narios had a limited effect on discharge at the Amargosa Wild regional groundwater flow system, Nevada and California, and Scenic River, where capture rates ranged from 3 to 4 per- with special reference to Devils Hole: U.S. Geological cent for all scenarios. Capture rates in 2120 at Ash Meadows Survey Professional Paper 1863, 178 p., accessed March 5, discharge area ranged from 8 to 9 percent for the base case, 2020, at https://doi.org/10.3133/pp1863. scenario A, and scenario B, and the simulated capture rate was 38 percent for scenario C. The four pumping scenarios Halford, K.J., and Plume, R.W., 2011, Potential effects of had moderate effects on discharge at the Furnace Creek area, groundwater pumping on water levels, phreatophytes, and where capture rates ranged from 10 to 11 percent for all spring discharges in Spring and Snake Valleys, White Pine scenarios in 2120. The capture rate at Stump Spring was 32 County, Nevada, and adjacent areas in Nevada and Utah: percent for the base case scenario and 36 percent for scenarios U.S. Geological Survey Scientific Investigations Report A, B, and C in 2120. 2011–5032, 52 p., https://doi.org/10.3133/sir20115032. Harbaugh, A.W., 1990, A computer program for calculating subregional water budgets using results from the U.S. References Cited Geological Survey Modular Three-Dimensional Finite- Difference Ground-Water Flow Model: U.S. Geological Survey Open-File Report 90–392, 46 p. [Also available at Bureau of Land Management, 1998, Record of decision for https://doi.org/10.3133/ofr90392.] the approved Las Vegas Resource Management Plan and final Environmental Impact Statement: Las Vegas, Nevada, Harbaugh, A.W., 2005, MODFLOW-2005—The U.S. Bureau of Land Management, 52 p., accessed November 19, Geological Survey modular ground-water model—The 2019, at https://eplanning.blm.gov/epl- front-office/projects/ ground-water flow process: U.S. Geological Survey lup/78155/128947/156899/1998_LV_RMP_ROD.pdf. Techniques and Methods, book 6, chap. A16 [variously paged], accessed November 19, 2019, at https://doi.org/ Claassen, H.C., 1985, Sources and mechanisms of recharge 10.3133/tm6A16. for ground water in the west-central Amargosa Desert, Nevada; a geochemical interpretation: U.S. Geological Harrill, J.R., Gates, J.S., and Thomas, J.M., 1988, Major Survey Professional Paper 712-F, 31 p., https://doi.org/ ground-water flow systems in the Great Basin region 10.3133/pp712F. of Nevada, Utah, and adjacent states: U.S. Geological Survey Hydrologic Atlas 694–C, 2 plates. [Also Dudley, W.W., Jr., and Larson, J.D., 1976, Effect of irrigation available at https://doi.org/10.3133/ha694C.] pumping on desert pupfish habitats in Ash Meadows, Nye County, Nevada: U.S. Geological Survey Professional Paper Interagency Wild and Scenic Rivers Coordinating Council, 927, 52 p. [Also available at https://doi.org/10.3133/pp927.] 2018, National Wild and Scenic Rivers System— Amargosa River, California: National Wild and Scenic Elliott, P.E., and Moreo, M.T., 2018, Update to the ground- Rivers System web page, accessed January 2, 2018, at water withdrawals database for the Death Valley regional https://www.rivers.gov/rivers/amargosa.php. groundwater flow system, Nevada and California, 1913–2010: U.S. Geological Survey data release, accessed Jackson, T.R., 2017, AQUIFER TEST PACKAGE— November 19, 2019, at https://doi.org/10.5066/F75H7FH3. Drawdown estimation and analysis of the ER-4-1 m1 multiple-well aquifer test of the lower carbonate aquifer, Geter, T., 2015, Amargosa Desert (hydrographic basin Yucca Flat, Nevada National Security Site: U.S. Geological 14–230) groundwater pumpage inventory water year 2015: Survey, aquifer test package, accessed June 1, 2017, at Department of Nevada Department of Conservation and https://nevada.usgs.gov/aquifertests/studies/tests.html?test_ Natural Resources, 126 p. pg=ER-4-1m1. Halford, K., Garcia, C.A., Fenelon, J., and Mirus, B., 2012, Jackson, T.R., and Halford, K.J., 2020, MODFLOW-2005 Advanced methods for modeling water-levels and estimat- model and supplementary data used to characterize ground- ing drawdowns with SeriesSEE, an Excel add-In (ver. water flow and effects of pumping in the Death Valley 1.1, July 2016): U.S. Geological Survey Techniques and regional groundwater flow system, Nevada and California, Methods, book 4, chap. F4, 28 p., accessed November 19, with special reference to Devils Hole: U.S. Geological 2019, at https://dx.doi.org/10.3133/tm4F4. Survey data release, https://doi.org/10.5066/P9HIYVG2. 30 Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California

Nelson, N.C., and Jackson, T.R., 2020, MODFLOW-2005 Williams, O.R., Albright, J.S., Christensen, P.K., Hansen, models used to simulate effects of pumping in the Death W.R., Hughes, J.C., Johns, A.E., McGlothlin, D.J., Pettee, Valley Regional Groundwater Flow System, Nevada and C.W., and Ponce, S.L., 1996, Water rights and Devil’s Hole California—Selected management scenarios projected to pupfish at Death Valley National Monument,in Halvorson, 2120: U.S. Geological Survey data release, https://doi.org/ W.L., and Davis, G.E., eds., Science and ecosystem 10.5066/P9OBUPXU. management in the National Parks: Tucson, University of Arizona Press, p. 161–183. Smith, D.W., Moreo, M.T., Garcia, C.A., Halford, K.J., and Fenelon, J.M., 2017, A process to estimate net infiltra- Winograd, I.J., and Pearson, F.J., Jr., 1976, Major carbon-14 tion using a site-scale water-budget approach, Rainier anomaly in a regional carbonate aquifer—Possible evi- Mesa, Nevada National Security Site, Nevada, 2002–05: dence for megascale channeling, south-central Great Basin: U.S. Geological Survey Scientific Investigations Report Water Resources Research, v. 12, no. 6, p. 1125–1143, 2017–5078, 22 p., https://doi.org/10.3133/sir20175078. https://doi.org/10.1029/WR012i006p01125. Walker, G.E., and Eakin, T.E., 1963, Geology and ground water of Amargosa Desert, Nevada-California: Nevada Department of Conservation and Natural Resources, Water Resources—Reconnaissance Series Report 14, 45 p., http://images.water.nv.gov/images/publications/ recon%20 reports/rpt14- Amargosa_valley.pdf. Publishing support provided by the U.S. Geological Survey Science Publishing Network, Tacoma Publishing Service Center

For more information concerning the research in this report, contact the Director, Nevada Water Science Center U.S. Geological Survey 2730 N. Deer Run Road Carson City, Nevada 89701 https://www.usgs.gov/centers/nv-water Nelson and Jackson—Simulated Effects of Pumping, Death Valley Regional Groundwater Flow System, Nevada and California—SIR 2020-5103 ISSN 2328-0328 (online) https://doi.org/10.3133/sir20205103