Hydrology of the Valley-Fill and 

Carbonate-Rock Reservoirs 

Pahrump Valley 

Nevada-California

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1832

Prepared in cooperation with the 

Nevada Department of Conservation 

and Natural Resources
Hydrology of the Valley-Fill and 

Carbonate-Rock Reservoirr 

Pahrump Valley 

Nevada-California

By GLENN T. MALMBERG

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1832

Prepared in cooperation with the 

Nevada Department of Conservation 

and Natural Resources

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1967
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

Library of Congress catalog-card No. GS 67-173

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402
CONTENTS

Page

Abstract-__ _____________________________________________________ 1

Introduction._____________________________________________________ 1

Location and extent of the area_________________________________ 1

Purpose and scope of the investigation.___---___-____--_--__.____ 3

Previous investigations.__-____-__-__-__--_-__-_-__--_-_____-.__ 4

Well-numbering system._______________________________________ 5

Acknowledgments. ____________________________________________ 7

Geography^ ______________________________________________________ 7

Topography and drainage..___________--_-_--__-____-__-_-__--__ 7

Culture_:___________________________________________________ 9

Climate______________________________________________________ 10

Geologic units and their water-bearing character.______________________ 12

Consolidated rocks-_____--__----___-__-_--___-_-____-_--______- 15

General features.______-_--__-____-______--______--._______ 15

Water-bearing character,--_--_-_-___-_-_---_-_-_-__-.______ 17

Valley fill._ ______________-________________-_________________ 18

Coarse-grained deposits..___________________________________ 18

Water-bearing character._-____-__-___-___--__-_-______. 19

Fine-grained deposits ______________________________________ 21

Water-bearing character.____-___--_-_----_-_--________- 22

Ground-water hydrology-_______--______-____--_---_-----_-___-_-_- 22

Reservoir systems.____________________________________________ 22

Carbonate-rock reservoir____._.___________________________ 24

Valley-fill reservoir._______________--_-_-__-_______-_--____- 24

Source and movement of ground water____________-__--_-._._____ 25

Recharge.-_-_-______-_____-_________-_____-------------__---_ 26

Discharge._--____-____________--__________---------_-_-----_- 27

Valley-fill reservoir.________________________________________ 27

Springs. ______________________.________-_------___--_- 27

Evapotranspiration. ___________________________________ 28

Subsurface outflow.____________________________________ 29

Pumpage.____________________________________________ 30

Carbonate-rock reservoir. __________________________________ 31

Ground water in storage._____________________________________ 33

Storage capacity__-__-____-----------------------__-------- 33

Depletion of ground water in storage.________________________ 34

Increase of ground water in storage._________________________ 34

Water budget.____-________________--__-___---_------_----_-_- 35

Perennial yield_______________-__-________-_____-_---------_--- 37

Overdraft...__________________________________________________ 39

Chemical quality of water.________________-______--_---_-_--__----- 40

Variations in quality.________________-________-_---------_-_--_ 40

Suitability of the water for irrigation.________-__--__-_----------- 42

Temperature. _____________________-____--__-_---_------------- 43

Summary and conclusions. ___-__________-_------------------------ 44

Selected references____________________--______-___----_-----_------ 46
IV CONTENTS

ILLUSTRATIONS

' [Plates are in pocket]

PLATE 1. Geologic map and sections of Pahrump Valley, shoving the location of 

selected wells and springs.

2. Map of Pahrump Valley, showing water-level contours in the valley-fill 

reservoir in February 1962.

3. Map of part of Pahrump Valley, showing the distribution of phreatophytes, 1959-61.

4. Map of Pahrump Valley, showing net change in water level in the 

valley-fill reservoir between February 1959 and February 1962.

5. Map showing variations in principal chemical constituents of ground 

water in Pahrump Valley.

Page

FIGUKE 1. Index map showing area of report--___--_---____-_________ 2

2. Diagram showing well-numbering system___________________ 6

3. Photograph showing part of the Pahrump fan.______________ 9

4. Graphs showing annual precipitation at three stations_-_____. 11

5. Diagrammatic section, Charleston Peak to the Ncpah Range, 

showing principal topographic, geologic, and hydrologic 

features. _____________________________________________ 23

6. Map showing area and magnitude of ground-water discharge

from springs and wells.________________________________ 32

7. Hydrographs showing water-level fluctuations in selected

wells tapping the valley-fill reservoir_---___-_--_________ 35

8. Graph showing approximate geothermal gradient.___________ 45

TABLES

Page 

TABLE 1. Annual precipitation at Pahrump Ranch, Nev______________ 10

2. Snow-course data for two stations in the Spring Mountains,

1945-62______________________________________________ 12

3. Geologic units of Pahrump Valley_________________________ 13

4. Estimated average annual precipitation and ground-water

recharge in Pahrump Valley.___________________________ 26

5. Estimated annual evapotranspiration in Pahrump Valley. -___ 29

6. Approximate discharge from springs and wells in Pahrump

Valley, 1875-1962_____________________________________ 31

7. Water-budget analysis for Pahrump Valley.________________ 36

8. Chemical analyses of typical irrigation water in Pahrump

Valley_ _____-----_____-----__-__----______-_________ 41

9. Summary of chemical quality of ground water in Pahrump

Valley_ ______-________-----.____----_-____________- 42
HYDROLOGY OF THE VALLEY-FILL AND CARBONATEROCK RESERVOIRS, PAHRUMP VALLEY, NEVADACALIFORNIA

By GLENN T. MALMBERG

ABSTRACT

This is the second appraisal of the water supply of Pahrump Valley, made 15 

years after the first cooperative study. In the first report the average recharge 

was estimated to be 23,000 acre-feet per year, only 1,000 acre-feet r^ore than 

the estimate made in this report. All this recharge was considered to be available 

for development. Because of the difficulty in salvaging the subsurface outflow 

from the deep carbonate-rock reservoil', this report concludes that the perennial 

yield may be only 12,000 acre-feet.

In 1875, Bennetts and Manse Springs reportedly discharged a total of nearly 

10,000 acre-feet of water from the valley-fill reservoir. After the construction of 

several flowing wells in 1910, the spring discharge began to decline. In the mid1940's many irrigation wells were drilled, and large-capacity pumpe were installed. During the 4-year period of this study (1959-62), the net pumping 

draft averaged about 25,000 acre-feet per year, or about twice the estimated 

yield. In 1962 Bennetts Spring was dry, and the discharge from Marse Spring 

was only 1,400 acre-feet.

During the period February 1959-February 1962, pumping caused an estimated storage depletion of 45,000 acre-feet, or 15,000 acre-feet per year. If the 

overdraft is maintained, depletion of stored water will continue anc" pumping 

costs will increase. Water levels in the vicinity of the Pahrump, Manse, and 

Fowler Ranches declined more than 10 feet in response to the pumping during 

this period, and they can be expected to continue to decline at the projected 

rate of more than 3 feet per year.

The chemical quality of the pumped water has been satisfactory for irrigation 

and domestic use. Recycling of water pumped for irrigation, however, could 

result in deterioration of the water quality with time.

INTRODUCTION

LOCATION AND EXTENT OF THE AREA

The Pahrump Valley drainage basin discussed in this r?port includes about 1,050 square miles in Clark and Nye Counties, southern 

Nevada, and Inyo and San Bernardino Counties, southeastern California (fig. 1). Approximately 200 square miles, or about 20 percent
HYDROLOGY, PAHRTJMP VALLEY, NEVADA-CALIFORNIA

120

42

50 50 100 150 MILES

FIGUBE 1. Area in Nevada and southern Califorria described in this report.
INTRODUCTION 6

of the total drainage area, is in California. Pahrump Valley lies approximately between lats 35°45' and 36°30' N. and longs 115°30' and 

116°15' W. It is east of Death Valley and the southern part of the 

Amargosa Desert, and west of Las Vegas Valley. The area extends 

from Johnnie, Nev., southeastward approximately 42 miles to a point 

about 14 miles south of Hidden Hills Ranch; it is about 30 miles 

wide and extends from the crest of the Nopah, the Kingston, and the 

northern part of the Resting Spring Ranges, on the southwest, to the 

crest of the Spring Mountains, on the northeast.

PUBPOSE AND SCOPE OF THE INVESTIGATION

This is the second hydrologic investigation of Pahrump Valley 

made by the U.S. Geological Survey under a cooperative program 

with the Nevada Department of Conservation and Natural Resources. 

Results of the first cooperative investigation are given in a report by 

Maxey and Jameson (1948), in which the geology and hydrology are 

briefly described and an estimate of recharge to and discharge from 

Pahrump Valley are given.

The second investigation was initiated at the request of the Nevada 

State Engineer and was prompted by inhabitants of the valley who are 

concerned with the accelerated rate of water-level decline in wells and 

the decrease in the yields of springs. The probability of overdevelopment of ground water in the valley and the evidence that Pahrump 

Valley is not a hydraulic ally closed basin, as it had previously been 

described, emphasized the need for a reevaluation of the occurrence 

and availability of the ground-water supply of the valley. This reevaluation is consistent with the objectives of the long-rang«, cooperative program (Shamberger, 1962, p. 14) for the orderly study of the 

water resources of Nevada; the long-range program provides for 

additional detailed studies of areas where moderate to substantial 

development has occurred and where records are available as a result 

of a long-continuing inventory.

The purpose of the investigation was to (a) describe the groundwater hydrology of the valley, with special emphasis on the occurrence, 

movement, and chemical character of ground water in the valley-fill 

reservoir and in the underlying carbonate-rock reservoir; (b) estimate 

the perennial yield of the basin; and (c) determine the extent of the 

overdraft. Early in the investigation it was found that subsurface 

outflow from the valley occurs through the carbonate rocks to adjacent 

areas. Owing to a lack of data to define the subsurface outflow and 

points of discharge, only a cursory study was made of this critical 

factor in the water supply of Pahrump Valley.
4 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

The field investigation was made in 1959, and analysis of the resultant data continued through 1962. The field study included a brief 

study of the geology of the area as related to the occurrence of ground 

water, an inventory of ground-water pumpage, the collection and 

analysis of water samples, and a limited number of determinations of 

the hydraulic characteristics of the saturated part of the valley fill. 

Thirteen test wells were drilled in December 1959 to augment the data 

in the undeveloped areas along the southwest margin of the valley and 

to establish a network of wells so that fluctuations of ground-water 

levels could be observed. The fieldwork was done by the author, 

assisted by C. P. Zones and Philip Cohen.

PREVIOUS INVESTIGATIONS

Several reports were published as a result of the previous hydrologic 

and geologic studies of parts of Pahrump Valley; reports used in the 

preparation of this report, are included in the list of selected references.

One of the first investigations of the water resources of the area was 

made by Mendenhall (1909), who made a reconnaissance of the water 

resources of southwestern Nevada and southeastern California. His 

report describes the wells and springs and gives data on their yields 

and on the chemical quality of the water. Data on springs and wells 

in the valley are listed in other publications, but the information commonly is not quantitative.

Waring (1921) studied the water resources of Pahrump Valley 

somewhat more intensively than did Mendenhall. Waring's report 

includes data on the quantity and quality of the ground water from 

springs and wells in Pahrump Valley and discusses the source and 

occurrence of ground water.

During 1922-36 the University of Nevada Agricultural Experiment 

Station at Las Vegas, under the direction of George Ha rdman, studied 

the occurrence and utilization of ground water in Las Vegas and 

Pahrump Valleys (Hardman, 1934, 1949). Valuable data on well 

and spring discharges, water-level measurements, and chemical quality 

of water were obtained during those studies and are contained in 

several reports, some of which were published ancf are listed in 

"Selected References."

In 1944 a reappraisal of the ground-water resources of Pahrump 

Valley was made by G. B. Maxey, U.S. Geological Survey, and C. H. 

Jameson of the Nevada State Engineer's office (Maxey and Jameson, 

1948). Results of that investigation were published in Nevada Water 

Resources Bulletin 5, which contains all data and results of the study 

of Pahrump Valley up to that time. The report summarizes the early 

history and development of ground water, describes ground-water
INTRODUCTION 5

occurrence and quality, and includes estimates of recharge to, and 

discharge from, the ground-water reservoir. Additional data are 

contained in two other reports (Robinson and others, 1947; Maxey 

and Robinson, 1947).

In January and February 1953 several electrical-resistivity depth 

profiles were made by the U.S. Geological Survey near the springs in 

Ash Meadows and in the dry lake in Stewart Valley. The?e profiles 

were made in an effort to obtain information on the source of water 

issuing from springs in Ash Meadows. Results of the studies were 

inconclusive.

WELL-NUMBERING SYSTEM

In this report the numbering of well locations is based on the rectangular system for the division of public lands. The study area 

encompasses the southeast quadrant of the Mount Diablo bas°- line and 

meridian, California, and the northeast quadrant of the San Bernardino base line and meridian, California. In this report the numbers 

assigned to wells in the Nevada part of the area consists of three principal parts: first, a capital S followed by the number of the township 

south of the Mount Diablo base line; second, a slash followed by a 

number designating the range east of the Mount Diablo meridian; and 

third, a hyphen followed by the section number and a series of letters 

used to designate the well location within the section. The letters 

a, b, c, and d designate, respectively, the northeast, northwest, southwest, and southeast quadrants. The first letter designates tY°> quarter 

section; the second letter, the quarter-quarter section; and tb Q, third 

where it was possible to make a determination the quarter-quarterquarter section. Where there is more than one well within a quarterquarter-quarter section, the wells are consecutively numbered according to the order in which they were recorded. For example, the first 

well recorded in the NE^NE^NE^ sec. 25, T. 21 S., R. 53 E., is 

numbered S21/53-25aaal (fig. 2), the second well recorded is numbered S21/53-25aaa2, and so forth. Where the 40-acre ard 10-acre 

tracts are unknown, the numbering system is modified to include only 

the designations for the subdivisions of the sections that are known. 

All wells in Pahrump Valley west of the boundary between Nevada 

and California are numbered in this report according to their location 

in relation to the San Bernardino base line and meridian line by a 

method similar to that just described. The only modification of the 

number is that a capital letter N precedes the township nurrber (such 

as N24/8-26bac), which indicates that the township is north of the 

San Bernardino base line. It thus enables the reader to distinguish 

wells in California from those in Nevada.
6 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

IN

MOUNT DIABLO BASELINE

1W

IS

1N

6

7

18

19

30

31

5

8

17

20

29

32

4

9

16

21

28

33

3

10

15

22

27

34

2

1 1

14

23

26

35

1

12

13

24

11

36

1E SAN BERNARDINO BASELINE

R. 53 E. S 21/53-25

FIGUBE 2. Well-numbering system.
GEOGRAPHY 7 

ACKNOWLEDGMENTS

Acknowledgement is made of the cooperation of residents of the 

valley in supplying data and permitting the use of their wells in the 

course of this investigation. The author is grateful for the wholehearted assistance received from Federal, State, and local governmental agencies. Most of the drillers' logs and other pertirent data 

on well construction used in this investigation were furnished by the 

Nevada State Engineer. Some of the data on chemical analyses of 

water were furnished by the California Department of Water Resources. Water-level records and estimates of annual pump^ge were 

obtained from the Las Vegas Artesian Well Supervisor.

GEOGRAPHY

TOPOGBAPHY AND DBAINAGE

Pahrump Valley is a structural depression bordered by high mountains. On the northeast the valley is bounded by the Spring Mountains, which have a maximum altitude of approximately 12,000 feet, 

and on the southwest by the parallel Nopah, Kingston, and Resting 

Spring Ranges, which have a maximum altitude of 6,000 fee* (pi. 1). 

The crest of a series of unnamed fault-block mountains form s a topographic divide that separates Pahrump Valley on the southwest from 

the Amargosa Desert. The southeast boundary of the valley is the 

crest of the unnamed hills that form a topographic divide between 

Pahrump Valley and Mesquite Valley.

Approximately 5 miles east of the Resting Spring Range, an unnamed bedrock spur about 10 miles long forms a low range of mountains that extend southeastward into Pahrump Valley from the northwest edge of the study area. This bedrock spur becomes progressively 

lower in altitude toward the southeast, and near the intersection of 

Nevada Highway 52 and the State border, it plunges bereath the 

alluvium of the valley floor. The small valley between the- bedrock 

spur and the Resting Spring Range on the southwest is 1'nown as 

Stewart Valley. Stewart Valley is hydraulically continuous with 

Pahrump Valley to the southeast and is included in the Pahrump 

Valley drainage basin (pi. 1).

Pahrump Valley is a topographically closed basin from which there 

is no surface-water flowT . Because of the aridity of the region (p. 10), 

no perennial streams exist in the area, except for short distances below 

the springs. Even the water from larger springs and from snowmelt 

in the mountains ordinarily seeps into the gravel of the drainage ways 

within short distances or is lost by evaporation and transpiration. 

Storms, though infrequent, cause the other washes to carr7 surface 

water for only short periods of time.
8 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

Runoff from precipitation within the basin ends in one of two playas, 

or "dry lakes," that lie at the base of the Resting Spring and Nopah 

Ranges on the southwest side of the valley. The ncHhwesternmost 

playa, in Stewart Valley, is the larger of the two, is somewhat irregularly shaped, and has an area of about 6i/£ square miles. At an altitude of about 2,457 feet, it occupies the lowest part of the study area. 

The second playa, about 13 miles southeast of Stewart Valley, is about 

3i/£ miles long and 2 miles wide and is about 60 feet higher in altitude 

than the playa in Stewart Valley. The two playas are separated by a 

low drainage divide that historically has precluded flow of surface 

water northwestward to Stewart Valley.

Runoff from most of the Pahrump drainage basin southeast of the 

Manse Ranch flows into the Pahrump Valley playa, and runoff northwest of the ranch flows to the playa in Stewart Valley. Water ponding in the playas ordinarily evaporates within a few days or weeks.

West of the community of Pahrump the valley floor is broad and 

flat and appears to have been an ancient playa or lake bottom. The 

valley floor slopes gently upward to the toe of the Pahrump fan and 

has an average gradient of about 15 feet per mile. Erosion has dissected it only slightly. Isolated spring mounds and srnd dunes occur 

on this part of the valley floor. Because of the moderately low 

gradient, the stream channels are poorly integrated and shallow. 

Consequently, storm runoff reaching this part of the valley generally 

spreads over a broad area and collects in shallow depressions, from 

which it is eventually discharged by evaporation and i ranspiration.

The topography of the valley floor near Hidden Hills Ranch is one 

of sharp contrasts, characterized in part by badlands. Between the 

northeast edge of the playa and the Manse Ranch, the valley floor 

slopes upward about 30 feet per mile. Locally the gradient is much 

steeper, however, owing to a northwest-trending range of low rounded 

hills and a series of fault scarps l^-G miles northeast of the playa. 

The hills and the scarps are breached in several places by deep southwest-trending arroyos, the largest of which, about 50 feet deep, are near 

Hidden Hills Ranch, Stump Spring, and Browns Spring. Locally 

buttes have formed as the result of erosion.

The southwest side of the Spring Mountains is characterized by 

large alluvial fans that head high in the canyons leading from Mount 

Charleston. The most prominent of these alluvial fans have formed 

at the mouths of Wheeler, Wallace, Carpenter, and Trout Canyons 

and have coalesced to form two major fans called the Pahrump and 

Manse fans, which were named for the large ranches established near 

their toes. The Pahrump and Manse fans extend far into the valley 

and are among the most notable topographic features of the area. The
GEOGRAPHY 9

slopes of the fans become progressively steeper toward the mountains 

and range in gradient from about 200 feet per mile near the ranches 

to about 400 feet per mile near the heads of the fans. Fan-head 

trenching is especially conspicuous in the Pahrump and Manse fans, 

where arroyos have been entrenched 100 feet or more into the fan 

deposits, as shown in figure 3. The large fans have coalesced with 

smaller fans at the mouths of smaller canyons to form an extensive 

alluvial apron along the front of the mountain range.

The topography along the southwest side of Pahrump Valley differs 

markedly from that on the northeast. Southwest of the two playas the 

alluvial fans rise abruptly to the base of the Nopah and Besting Spring 

Kanges, the slope being as much as 500-600 feet per mile.

FIGURE 3. Upper part of the Pahrump fan in Wheeler Wash. The wash 

has been incised to a depth of more than 100 feet below the surface of 

the alluvial fan, and the underlying bedrock is exposed.

CULTUBE

The small settlement of Pahrump the only community in the 

area is in the north-central part of the valley, at the intersection of 

Nevada Highways 52 and 16. Pahrump is the local supply center for 

ranches, and during the summer of 1959 a cotton gin was constructed 

there to process the cotton grown in the valley. A consolidated public 

elementary school is available to the school-age residents in the valley.

Pahrump Valley is one of the most productive farming districts in
10 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

southern Nevada. Agriculture, the principal occupation in the valley, 

is dependent wholly on irrigation from ground water. During 1961 

approximately 6,500 acres was irrigated. Because the climate is arid 

and the daytime temperatures are extremely high, only cotton, alfalfa, 

small grains, and native grasses can generally be grown. Except for 

a dairy herd and a. few range cattle maintained at the Manse Ranch, 

the raising of livestock has been limited by the sparseness of native 

vegetation suitable for browsing.

CLIMATE

The climate of southern Nevada ranges from arid to semiarid. 

Pahrump Valley is arid, characterized by small amounts of precipitation, low humidity, and wide extremes in daily temperatures. Winters 

are short and mild, and the summers, long and very hot.

The precipitation occurs mainly during the winter, and it generally 

increases in abundance with altitude. Winter storms are commonly 

regional in nature, whereas summer storms ordinarily occur as very 

localized thunderstorms in the mountains. At the lower altitudes 

evaporation rates are extremely high, probably exceeding 100 inches 

per year. Strong winds are common throughout the year but are more 

prevalent in the spring than in the other seasons.

Climatological data have been obtained intermittently at Pahrump 

Ranch since 1914. Table 1 shows the approximate precipitation for 

the 14 years during which observations were made and indicates that 

the annual precipitation for those years ranged from 1.88 to 7.26 inches 

and averaged about 4 inches.

In 1945 two precipitation storage gages were installed at Roberts 

Ranch and Bedrock Summit on the west slope of the Spring Mountains. The amount of precipitation recorded at these stations is 

graphically illustrated in figure 4.

TABLE 1. Annual precipitation at Pahrump Ranch 

[NR, no record. From records of the U.S. Weather Bureau]

Year 

1914 ... _______

1915-19 - _ --._

1920 

1921 .. ......

1922___ ___ . .

1923- _ _________

1924 ____ _____

1925-44 ________

1945 ___________

1946___ ________

1947____ _ _______

Inches

______ ___ 14.90

 NR

__________ 7.26

._______._ 2 5.87

.____-__._ 5.58

__________ 2 4.49

_________ 2.20

_________ NR

__________ 4.57

________ NR

_________ 2.80

Year 

1948 - _________

1949 

1950 - -------

1951-58 - ______

1959 

I960-. ___ ___ _ __

1961 

1962_________________

A V GFci £G

Inches 

NR

_______ 5.73

_______ 1.88

_______ NR

_______ 3 3.58

4. 77

3 2. 43

2.46

.__-_- 4.18

' 3 months of the year estimated from monthly averages. 

* 1 month of the year estimated from monthly averages. 

8 Values listed as estimates.
GEOGRAPHY 11

25,

20

15

10

<f> 0 '

UJ

I 

o

z

20,

Red Ro~k Summit 

(alt 6500 ft)

Q_ 10

/Average 10.6

10

No 

record

Average 4.18^

record

Pahrump Ranch 

(alt 2669 ft)

FIGURE 4. Annual precipitation at three stations in Pahrump Valley.

Eecords of two snow courses in the Spring Mountains one in Clark 

Canyon and the other at Trough Springs are listed in tr.ble 2; the 

snow-course data indicate a wide annual variation in the amount of 

water contained in the snow cover.
12 HYDROLOGY, PAHRTJMP VALLEY, NEVADA-CALIFORNIA

TABLE 2. Snow-course data for two stations in the Spring Mountains, 194-5-62

[NR, no record. Snow and water data given in inches. Record from the Nevada Cooperative Snow

Surveys]

Year

1945 -

1946.......

1947 -

1948 -

1949 .. ..

1950 

1951. ...

1952 

1953 

1954 

1955 

1956 

1957 

1958 

1959 

I960 

1961 

1962 

AverClark Canyon Station (Alt 9,000 ft)

February-March

Date

NR

Mar. 2 

Mar. 6 

Feb. 26 

Mar. 4 

Mar. 1 

Feb. 27 

Feb. 24 

Feb. 26 

Feb. 24 

Feb. 27 

Feb. 25 

Feb. 28 

Feb. 23 

Mar. 1 

Feb. 26 

Feb. 25 

Feb. 28

Snow

NR 

16.4 

24.8 

23.4 

48.4 

14.5 

16.8 

36.6 

10.7 

23.3 

26 

13 

11 

24 

21 

37 

10 

41

Water

NR

4..9 

7.6 

7.2 

13.5 

4.9 

2.8 

11.8 

3.1 

8.5 

7.9 

3.8 

4.6 

7.0 

5.4 

11.1 

2.8 

12.6

7.0

March- April

Date

Mar. 28 

Apr. 1 

Mar. 27 

Mar. 29 

Apr. 1 

Mar. 30 

Mar. 29 

Mar. 25 

Mar. 29 

Apr. 1 

Mar. 30 

Mar. 29 

Mar. 26 

Mar. 29 

Mar. 29 

Mar. 27 

Mar. 29 

Mar. 29

Snow

46.3

28.8 

15.4 

27.7 

61.6 

9.4 

6.2 

59.8 

1.1 

34.5 

19 

2 

8 

40 

9 

22 

15 

41

Water

14.3 

8.3 

5.2 

8.1 

18.0 

3.9 

1.5 

18.7 

0.3 

12.8 

6.2 

0.8 

3.7 

11.6 

4.7 

7.9 

3.1 

13.7

7.9

Trough Springs Statiin (Alt 8,500 ft)

February-March

Date

NR

Feb. 27 

Feb. 28 

Feb. 25 

Mar. 4 

Feb. 27 

Feb. 28 

Feb. 25 

Feb. 28 

Feb. 25 

Mar. 1 

Feb. 29 

Feb. 26 

Feb. 23 

Feb. 28 

Feb. 27 

Feb. 25 

Feb. 28

Snow

NR 

14.3 

13.9 

20.0 

46.4 

9.9 

13.3 

38.6 

3.9 

20.1 

23 

9 

7 

18 

16 

33 

7 

34

Water

NR 

4.3

4.9 

6.2 

11.5 

3.1 

2.9 

13.5 

1.2 

7.0 

7.6 

2.9 

2.3 

6.6 

4.6 

10.1 

2.0 

10.6

5.9

March-April

Date

NR

Mar. 29 

Mar. 26 

Mar. 30 

.Apr. 3 

Apr. 2 

Mar. 30 

Mar. 31 

Mar. 28 

.Apr. 2 

Mar. 28 

Mar. 30 

Mar. 28 

Mar. 31 

Mar. 27 

Mar. 26 

Mar. 29 

Mar. 27

Snow

NR

20.6 

3.2 

21.0 

51.8 

1.9 

2.7 

49.5 

0 

29.2 

10 

Trace 

4 

29 

5 

17 

7 

30

Water

NR

6.8 

1.6 

7.2 

14.3 

0.9 

0.5 

17.4 

0 

11.0 

3.9 

Trace 

1.2 

9.9 

2.2 

6.0 

1.9 

10.9

5.6

GEOLOGIC UNITS AND THEIR WATER-BEARING 

CHARACTER

The geology of many of the mountains bordering Pahrump Valley 

is described in detail in several published reports, the most pertinent 

of which are listed in "Selected References." The generalized description of rocks in the mountains, as given in this report, is based 

mainly on a review of those publications. The geology of the sedimentary deposits of the valley fill was studied and mapped by the 

author during the course of this investigation.

For purposes of this report the rocks of the area are divided into 

two very generalized groups. The division is based mainly on the 

water-bearing character and the relative stratigraphic position of 

the rocks with respect to the occurrence and movement of ground 

water: the consolidated rocks that form the mountain ranges and 

underlie the valley fill, and the unconsolidated and partially consolidated sedimentary deposits of the valley fill. Table 3 shows the 

principal rock units and their stratigraphic relationships, lithologic 

character, and water-bearing properties. Plate 1 shows the areal 

distribution of the lithologic units listed in table 3.
GEOLOGIC UNITS AND THEIR WATER-BEARING CHARACTER 13 

TABLE 3. Geologic units of Pahrump Valley

System

>>&

1

ta

3 

&

Series

"S

«

 o

o>

o."w

»

s

Lithologic

unit

Younger

fan 

deposits

Younger

surflcial

deposits

Member

Younger

alluvialfan

deposits

Channel

deposits

Younger

alluvium

Playa

deposits

Lithology and occurrence

Unconsolidated alluvial-fan

deposits and mudflow debris,

consisting of boulders, gravel,

sand, silt, and clay derived

from older alluvial fans and

local exposures of consolidated

rock; occur locally as stringers

and lenses of relatively clean

sand and gravel that partly

mantle the alluvial apron

along the mountain fronts.

A veneer covers the pediment

in the area east of Hidden

Hills Ranch. Heterogeneity

of the material decreases

away from the mountains;

material grades laterally into

finer grained and better

sorted younger alluvium.

Unconsolidated fairly well

sorted gravel, sand and silt

in the principal arroyos

draining the major watershed

areas. Particle size decreases

and sorting and rounding

generally increase away from

mountain fronts.

Unconsolidated moderately

well sorted sand, silt, and

clay and minor amounts of

gravel derived mostly from

medial and older lacustrine

deposits and from alluvial

fans. Extensively exposed

on the valley floor.

Unconsolidated clay, silt, and

fine sand. The surface of the

playa in Stewart Valley is

loosely compacted and

flocculated clay, whereas the

surface of the playa in the

west-central part of the valley

is hard and compact.

Water-bearing properties

Lies mainly above the zone of

saturation; however, where it

dips beneath tl e valley floor

into the zone of saturation ,

stringers and lenses of

relatively clean well-sorted

gravel readily yield water to

wells.

Highly permeable material

occurring mainly above the

zone of saturation in the

recharge area. Outcrops

provide ready access for

ground-water recharge from

snow melt and storm runoff.

Where buried vathin the

alluvial fans, deposits transmit water from areas of

recharge to the valley fill.

Deposits yield large quantities

of water when tapped by

wells in the zone of saturation.

Moderate to low permeability

generally limits productivity

of wells to small yields.

Where saturated, the permeability of these deposits is very

low; consequently, they will

not readily yield water to

wells. The che~nical quality

of the ground water beneath

the playa in Stewart Valley is

generally unfit for most uses.

240-366 O 67-
14 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA 

TABLE 3. Geologic units of Pahrump Valley Continued

System

§

U

I,

i

s03

a

cy

>,

So

10?

 0

^

.2

S3 H

Series

§

9

S

§

A

 o 

a

a

<u a

§

JS

PH

Oi

g

1

A<

"3

o

 Oi

I

-2

^

Lithologic

unit

Younger

surficial

depositsCon.

Medial

fanglomerate

Medial

lacustrine

deposits

Older

lacustrine

deposits

Older

fanglomerate

Member

Dune

sand

Sinter

Lithology and occurrence

Unconsolidated sand, silt, and

clay derived mainly from

younger alluvium and older

and medial lacustrine

deposits. Dunes are

commonly stabilized by

vegetation.

Calcareous siliceous spring

mounds derived form the

conspicuous mounds along

the fault in the central part

of the valley.

Unconsolidated to cemented

alluvial fan deposits and

mudfiow debris composed of

boulders, sand, silt, and clay;

contains stringers and lenses

of relatively clean well sorted

sand and gravel. Crops out

adjacent to consolidated rock

along the Spring Mountains

and dips toward the center of

the valley beneath the

younger alluvial-fan deposits.

Calcareous clay and silt.

Occur as shore-line deposits

along the base of the

Pahrump and Manse fans.

Predominantly clay and silt;

minor amounts of fine sand

and mudflow debris; a few

beds of caliche; faulted and

gently warped. Principal

exposures occur on the upthrown fault block along the

longitudinal axis of the valley.

Poorly consolidated to unconsolidated alluvial-fan and

mudflow debris consisting

of poorly-sorted boulders,

gravel, sand, silt, and clay.

The debris, derived mainly

from Kingston Mountain, is

of igneous, metamorphic and

sedimentary origin. Outcrops are present only in the

southern half of the valley.

The unit is faulted and highly

dissected.

Water-bearing properties

Lies above the zone of saturation. Downward percolation

and subsequent ground- water

recharge from precipitation

are limited because of the low

permeability of the material.

Limited areal extent and low

degree of permeability render

the deport unimportant as an

aquifer.

The generally poor sorting and

partial cementation limit the

water bearing zones to buried

gravel trains in the higher

areas of the alluvial fans.

Zones are also limited to

lenses of fairly well-sorted and

rounded sand and gravel in

the lowe- areas of the fans.

Where the deposits lie in the

zone of saturation, highly

permeable lenses of gravel and

sand reaiily yield water to

wells ani are the most productive aquifers in the valley.

Unconsolidated to partly consolidated clay and silt and

minor ar»ounts of sand that

occur mainly above the zone

of saturation.

Mostly Unconsolidated to

indurated fine-grained

material that has low permeability. Where saturated,

thin beds of fine-grained sand

may yie'd moderate amounts

of water to wells.

Lies largely above the zone of

saturation and is not known

to be pe^trated by wells.

Heterogeneity of the material

suggests that its permeability

is low.
GEOLOGIC UNITS AND THEIR WATER-BEARING CHARACTER 15

TABLE 3. Geologic units of I'ahrump Valley Continued

System

.§

k*

s

.2'-£

H

0

i

Precambri

Series

aq;

o

s

I

8

o

§

Lithologie 

unit

Tuff

Sedimentary,

metamorphic,

and

igneous 

rocks

Member Lithology and occurrence

White and light-yellow to lightgreen beds of thinly laminated tuff; extensively faulted 

and folded. Exposed at the

base of the upthrown fault 

block along the NevadaCalifornia border.

Basement complex; forms the

confines of the alluvial basin;

composed of: Precambrian

gneiss, granite, and sedimentary rock; Paleozoic limestone, dolomite, and quartzite; Mesozoic clastic and

granitic rocks; and Tertiary

tuff, some volcanic flows,

and fresh-water limestone.

Water-bearirg properties

Consolidated an-"1 partly to

highly indurated; has very

low permeabil'^y. Where 

saturated, it would yield

virtually no water to wells.

Highly indurated rock having

limited primary porosity.

The intensive faulting and

crushing and subsequent

solution of the carbonate rocks

have resulted in the formation

of local and repional zones of

high permeability. Inferences

drawn from the existing data

suggest that highly fractured

and altered carbonate rocks 

transmit approximately half 

of the estimated average 

annual recharge to adjacent

areas. Rocks not tapped by

wells.

CONSOLIDATED BOCKS 

GENERAL, FEATURES

The consolidated rocks that crop out in Pahrump Valley are several 

thousand feet thick and are made up predominantly of dense highly 

indurated crystalline, metamorphic, and sedimentary rocks. The sedimentary rocks include a thick sequence of beds composed mainly of 

calcareous and clastic material; they are widespread throughout 

eastern and southern Nevada and adjacent areas of Utah and California. In this region the consolidated rocks have been intensely 

folded, faulted, and deeply dissected by erosion. Consequently, they 

form a rugged surface of high relief. Sedimentary rocks of Paleozoic 

age and, to a lesser extent, sedimentary and igneous rocks of Mesozoic 

and Tertiary age occur beneath the intermontane basins and form most 

of the mountain ranges that border the basins. Beneath the floor of 

most of the alluvium-filled valleys the consolidated rocks occur at 

depths of as much as several thousand feet.

The lithologic units forming the consolidated-rock group differ 

widely in lithology. In the study area they consist principally of 

limestone, dolomite, sandstone, shale, and quartzite and lesser amounts 

of intrusive igneous rocks, tuff, breccia, and volcanic flows. In aggregate, the units range in thickness from about 13,000 feet (Hewett, 1931,
10 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

p. 9), in the southern part of the Spring Mountains, to about 33,000 

feet (Nolan, 1929, p. 465), at the north end of the range.

The Spring Mountains, south of Charleston Peak, are composed of 

about 8,500 feet of dominantly fossiliferous limestone and dolomite of 

Paleozoic age (Hewett, 1931, p. 9,10) overlain by approximately 4,500 

feet of largely sandstone, shale, and conglomerate of Mesozoic age. 

North of Charleston Peak the Paleozoic section thickens, and near 

Mount Sterling the exposed rocks consist of about 12,000 feet of quartzite and shale of Cambrian age (Nolan, 1929, p. 461-465) overlain by 

about 21,000 feet of dominantly carbonate rocks of marine origin.

In the Kingston Range, bordering Pahrump Valley on the southwest, about 5,400 feet of metamorphic and sedimentary rocks of Precambrian age is exposed. The Precambrian rocks a.ra- overlain by 

about 2,000 feet of carbonate rocks of Paleozoic age which have been 

intruded by monzonite porphyry and related intrusive rocks of Late 

Cretaceous to late Tertiary age. The carbonate rocks, in turn, are 

overlain by an unmeasured thickness of unconsolidated deposits consisting of sand, gravel, bentonite, and ash of Cenozoic age (Hewett, 

1948, p. 196-200). In the Nopah and Resting Spring Ranges, about 

7,000 feet of Precambrian metamorphic, igneous, and sedimentary 

rocks is overlain by about 22,900 feet of Paleozoic rocks (Hazzard, 

1937, p. 289). The base of the Paleozoic section is composed of about 

14,800 feet of dominantly clastic rock of Cambrian age, Most of the 

overlying strata in the Paleozoic section are carbonate rocks. Lava 

flows of probable Tertiary age lie unconf ormably on rocks of Paleozoic 

age in the Resting Spring Range but are absent from the Nopah Range. 

Isolated exposures of highly indurated fresh-water limestone, tuff, 

and flows of Tertiary (?) age on the north and northeast flanks of the 

Kingston Range are included with the basement complex on plate 1.

In the Spring Mountains, normal faults having relative displacements of several thousand feet and a series of north-trending thrust 

faults have caused intense local fracturing of the rocks ?nd the superposition of rocks of older geologic age on younger ones. The regional 

structural deformation that created the mountains also formed the 

large structural depression in the consolidated rocks that underlie 

Pahrump Valley. More than a thousand feet of erosional debris from 

the adjacent highland areas has accumulated in this depression and 

now covers most of the underlying bedrock. Consequently, the geologic and topographic features that resulted from the structural 

activity are buried and are not known. Because of the structural 

origin of the basin, however, the relief on the buried bedrock surface 

probably varies markedly within short distances.
GEOLOGIC UNITS AND THEIR WATER-BEARING CHARACTER 17 

WATER-BEARING CHARACTER

The consolidated rocks differ widely in hydraulic properties; most 

are dense and well indurated and possess little primary permeability. 

Some of the rocks, however, are capable of absorbing, storing, and 

transmitting water owing to intensive fracturing and chemical weathering. The crystalline and clastic units contain some water in fractures and joints, although the fractures are generally tight and, 

therefore, do not readily transmit water.

The carbonate-rock units, on the other hand, principally those of 

Paleozoic age, contain fractures and solution channels and are locally 

moderately to highly permeable. They constitute a major reservoir 

system that underlies most of southern Nevada, and ground water is 

thereby transmitted beneath topographic divides from one valley to 

another. In this report the complex carbonate rocks, as related to 

the hydrology of the valley, are referred to simply as the carbonaterock reservoir. This reservoir was not recognized in the study made 

20 years ago by Maxey and Jameson (1948, p. 116), who stated that 

the consolidated rocks were impermeable.

Test drilling at several locations at the Nevada Test Site, about 25 

miles north of Pahrump Valley, has shown that locally the carbonaterock aquifer is capable of transmitting large quantities of ground 

water. Coefficients of transmissibility, computed from pumping-test 

data for wells tapping this aquifer, range from 400 to 900,000 gpd per 

ft (gallons per day per foot) (Winograd, 1963, p. 29). The coefficient of transmissibility is defined as the rate of flow of water, at 

the prevailing water temperature, in gallons per day, through a 1-foot - 

wide vertical strip of the aquifer that extends the full saturated 

height of the aquifer, under a hydraulic gradient of 100 percent 

(Theis 1935). The test drilling also showed that the Precambrian 

crystalline and sedimentary rocks and Paleozoic clastic formations 

have low permeability. These rocks contain little water and generally 

function as barriers that impede ground-water movement.

Hundreds of feet of core from numerous widely spaced wells at the 

Nevada Test Site indicate that the permeability of the carbonate-rock 

aquifer at depth is probably due principally to fractures rather than 

to solution channels. The presence of numerous caves and large 

springs in carbonate rocks that crop out throughout the southern and 

eastern parts of the State, and the occurrence of open fractures in the 

carbonate rocks at depths of several thousand feet suggest, however, 

that solution by percolating ground water is also a significant factor 

in the transmission of ground water. Devils Hole, near Ash Meadows, 

is an example of a solution opening in Paleozoic carbonate rocks.
18 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

VALLEY TILL

Thick semiconsolidated to unconsolidated continental deposits of 

fluvial and lacustrine origin have accumulated in Pah rump Valley 

and form the principal ground-water reservoir. The continental 

deposits are of Tertiary and Quaternary age and are composed mainly 

of detrital material; they underlie an area of about 650 square miles 

in the central part of the valley. Thickness of the valley fill is unknown; although several wells have been drilled to depths of about 

1,000 feet, none have penetrated bedrock.

The valley fill consists principally of alluvial material derived from 

older consolidated rocks in the surrounding mountains and is interbedded with some tuff and chemical precipitates. The oldest recognized sedimentary deposits of the valley fill are composed of an 

unknown thickness of partially consolidated and higlly indurated 

tuff of Tertiary age. Overlying the tuff is a succession of unconsolidated material consisting of alluvial-fan and lacustrine deposits 

ranging in age from late(?) Tertiary to Quaternary. Six major 

units are recognized in this succession of deposits; they are: Older 

fanglomerate, older lacustrine deposits, medial lacustrine deposits, 

medial fanglomerate, younger surficial deposits, and younger fan 

deposits.

The older deposits have been uplifted by faulting and gentle folding 

and subsequently have been exposed by erosion. Northeast of the 

fault that approximately parallels the California-Nevada border 

(pi. 1), erosion of the upthrown fault block has exposed approximately 

1,000 feet of the upper part of the valley fill.

The valley-fill deposits are grouped into two very generalized types. 

On the basis of their lithologic and and hydrologic character as determined from exposures and lithologic logs, the types are (1) the coarsegrained alluvial-fan deposits of low to high permeability along the 

margin of the valley, and (2) the uniformly fine-grained lacustrine and 

play a deposits of low permeability in the central part of the valley.

COARSE-GRAINED DEPOSITS

The coarse-grained deposits of the valley fill crop out in an area of 

about 300 square miles along the perimeter of the valley ?,nd in isolated 

exposures on the crests of a range of low hills along the Nevada-California border. The coarse-grained deposits, composed principally of 

sand, gravel, and boulders, were derived from adjacent mountains. 

The material was deposited mainly in alluvial fans an^l aprons that 

form thick wedges of gravel along the edge of the valley. These 

deposits are the older and the medial fanglomerate of Pliocene and 

early Pleistocene age and the younger fan deposits of Pleistocene and
GEOLOGIC UNITS AND THEIR WATER-BEARING CHARACTER 19

Recent age. Those alluvial-fan deposits that had been raised above 

the adjacent alluvial surfaces by faulting or up warp ing and then dissected by erosion were mapped as older and medial fanglomerate. 

Alluvial-fan deposits that are unaltered by deformation and erosion 

and are sites of active deposition were mapped as younger fan deposits. 

Coarse-grained channel deposits in the major arroyos were also included in the younger fan deposits.

The most extensive outcrop area of coarse-grained deposits is in the 

alluvial apron along the east side of Pahrump Valley, adjacent to the 

Spring Mountains. Exposures are widest at the reentrant valleys 

that drain onto the Pahrump and Manse fans. The outcrop is approximately 12 miles wide on the Pahrump fan, but elsewhere along the 

northeast side of the valley it averages about 7 miles wide. Less 

extensive areas of alluvial-fan deposits are exposed along the southwest 

side of Pahrump Valley, where the average width of the outcrop is 

less than 3 miles.

Most material in the alluvial fans and aprons is poorly bedded, and 

locally it is moderately to highly indurated by calcareous cement. The 

beds dip away from the mountain fronts toward the central part of 

the valley.

The coarsest, most angular, and least sorted material occurs near 

the heads of the alluvial slopes at the mountain front. Farther away 

from the mountains the dip of the beds decreases, and the material 

becomes smaller, slightly more rounded, and better sorted. Along 

the lower margins of the fans, these deposits interfinger with and grade 

laterally into contemporaneous lacustrine or playa deposits. Well 

logs of some of the deeper wells drilled near the toes of the fans along 

the northeast side of the valley show that beds of sand, gravel, and 

boulders interfinger with playa or lacustrine strata. Although marked 

differences in lithology between typical fan deposits and typical lacustrine or playa deposits are common, the lateral change in lithology is 

generally gradational through a zone of several miles.

Faulting, up warping, and subsequent erosion of the alluvial-fan deposits have resulted in the formation of drainage channels, or arroyos, 

that have been deeply entrenched in the heads of the alluvial fans. 

Characteristically, the bed material in these channels is coarsest near 

the mouths of the canyons and becomes progressively fin°-r grained 

downslope. In the larger stream channels, stringers of relatively clean 

gravel and sand have been transported to points many miles from the 

mountains.

WATER-BEARING CHARACTER

The coarse-grained valley-fill deposits form the most productive 

water-bearing material in the area. For purposes of this report, the 

older and the medial fanglomerates and the younger fan deposits
20 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

along the mountain fronts, as shown on plate 1, are regarded as a 

single hydrogeologic unit. The high degree of cementation of the 

alluvial deposits in the walls of the arroyos near the heads of the alluvial fans indicates that the bulk of the coarse-grained material in the 

upper part of the alluvial apron has low permeability and porosity. 

Stringers of relatively clean uncemented gravel in the existing1 channels and in those buried within the alluvial-fan deposits, however, are 

highly permeable and readily transmit water. Most runoff from the 

watershed that reaches the alluvial fans percolates into the gravel deposits. Following cloudbursts, only rarely does runoff from the mountains reach the valley floor.

Because of the wide variation in lithology of the alluvial-fan deposits, the hydraulic characteristics vary greatly within short distances ; and predictions of the water-bearing properties in undeveloped 

areas are, therefore, somewhat speculative. Wells drilled along the 

toes of the fans, however, usually penetrate highly permeable lenses or 

stringers of sand and gravel that are capable of yielding large quantities of water. The specific capacities of 20 wells drilled along the 

toes of Pahrump and Manse fans range from about 5 to 185 gpm 

(gallons per minute) per foot of drawdown. The specific capacity 

of a well is defined as the rate of yield per unit of drawdown and 

is generally expressed as gallons per minute per foot of drawdown 

(Wenzel,1942,p.l51).

Water-bearing lenses of sand and gravel in the alluvial-fan deposits 

are generally irregular in thickness and in areal extent and commonly 

cannot be traced as individual beds from well to well. These alluvialfan deposits are overlain locally by layers of caliche or other comparatively impermeable material, or they interfinger with lacustrine 

or playa deposits; therefore they may contain ground water under 

confined or artesian pressure. In early stages of agricultural development of the valley, many high-capacity flowing wells were developed 

in these deposits.

Southwest of the alluvial apron the thickness and the number of 

highly permeable layers of sand and gravel decrease, and the amount 

of silt and clay increases. Consequently, the yields of wells commonly 

decrease farther away from the fans.

No attempt has been made to develop wells in the coarse-grained 

deposits along the base of the Nopah and Resting Spring Ranges on 

the southwest side of Pahrump Valley. The water-bearing character 

of the deposits in this area, therefore, generally is not known. Because 

the alluvial fans are small and the transport distance of the alluvialfan material is short, however, the materials probably are more angular, less well sorted, and less permeable than correlative material on 

the northeast side of the valley.
GEOLOGIC UNITS AND THEIR WATER-BEARING CHARACTER 21 

FINE-GRAINED DEPOSITS

The deposits that crop out in an area of about 350 square miles 

in the central part of Pahrump Valley are composed principally of 

silt, clay, and fine-grained sand and some tuff and precipitates. These 

fine-grained deposits include four principal lithologic units (table 3; 

pi. 1) : (1) tuff of Miocene or Pliocene age, (2) older and (3) medial 

lacustrine deposits of Pliocene and early Pleistocene age, and (4) 

younger surficial deposits of Pleistocene and Recent age, which include 

younger alluvium, playa deposits, dune sand, and sinter.

The beds of tuff and overlying older lacustrine deposits a,re exposed 

in the central part of the valley, where they have been uplifted and 

faulted and subsequently exposed by erosion. The fault is approximately parallel to the boundary between Nevada and California and 

extends from the south edge of the study area about 23 miles along 

the trough of the valley. The deposits northeast of the fault are 

now stratigraphically higher than those on the southwest side, and 

the beds adjacent to the fault on the northeast are tilted at angles of 

as much as 15°. Along the east margin of the fine-grained deposits, 

the medial and older lacustrine deposits are slightly tilted and bowed 

upward. Erosion has planed off the surface of the upthrown fault 

block, exposing approximately 1,000 feet of the uppermost beds of the 

fine-grained deposits.

Exposed in the banks of arroyos near Hidden Hills Ranch (pi. 1) is 

about 200 feet of thin-bedded to massive tuff that is overlain by about 

800 feet of thin to massive beds predominantly of silt and clay. The 

silt and clay are interbedded locally with layers of caliche, laminations 

of fine-grained sand, and thin beds of f anglomerate. Most of the material is erosional debris transported from the alluvial fans and 

weathered material eroded from older Tertiary deposits. Some of the 

strata containing mud cracks, ripple marks, and crossbedding are interbedded with uniform layers of clay and silt, which suggests that they 

probably were deposited in a basin that was occupied alternately by 

playas and by lakes. The thickness of the lacustrine deposits generally is unknown and may vary considerably from one area to another, 

owing to the irregularity of the surfaces of the tuff and bedrock on 

which the deposits lie unconformably.

Logs of wells drilled in the fine-grained deposits in the northern part 

of the valley west of Pahrump (pi. 1) indicate a gross overall lithology 

similar to that exposed near Hidden Hills Ranch. Data are insufficient at this time, however, to indicate whether individual beds 

extend as continuous stratigraphic units beneath the entire valley floor.

240-366 O 67 8
22 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA 

WATER-BEARING CHARACTER

The predominance of clay throughout the fine-grained deposits 

generally causes them to be poor aquifers. In the upp^r 800 feet of 

the exposed material in the walls of the dry wash passing through 

Hidden Hills Ranch, the only beds that would be capable of transmitting small amounts of ground water are thin beds of fine sand. 

The tuff in the lower 200 feet of exposed material has low porosity 

and low permeability and generally tends to retard the movement of 

ground water.

Several attempts have been made to develop ground water from the 

fine-grained deposits near Hidden Hills Ranch, in the adjacent area 

to the southwest, and in the area west of Pahrump. Several wells 

have been drilled in these areas to depths of 800 feet or more, and well 

N22/10-26 (not shown on pi. 1), 21/£ miles southwest of Sfump Spring, 

was reportedly drilled to a depth of 1,351 feet. This well, though 

never completed, is the deepest known in the valley, and the driller 

reported that it was dry. 'The driller's log shows thr,t, except for 

minor amounts of sand, silt, and cemented gravel, the entire drilled 

thickness was clay.

Of the wells in the vicinity of Hidden Hills Ranch for which 

pumping data are available, none have a specific capacity greater than 

1 gpm per foot of drawdown. In the area between tl ^ toes of the 

Manse and Pahrump fans and the California-Nevada boundary, 

approximately 50 wells of various depths have been developed in finegrained deposits. The highest specific capacity in any cf the 10 wells 

tested in this group was only about 5 gpm per foot of drawdown.

GROUND-WATER HYDROLOGY

RESERVOIR SYSTEMS

Ground water in Pahrump Valley occurs in two principal reservoirs : the valley fill and the carbonate rocks. The valley-fill reservoir 

is coextensive with the area shown as fine-grained and coarse-grained 

deposits on plate 1. The carbonate-rock reservoir underlies the valley 

fill and extends laterally into the adjacent hills and mountains. 

Because no wells penetrate both systems, the hydraulic continuity and 

magnitude of interflow between them these systems is poorly 

understood.

Figure 5 is a diagrammatic cross section of Pahrump Valley 

showing, the probable general relation between the valley-fill and 

carbonate-rock reservoirs. If the tuff in the lower part, of the valley 

fill is widespread, as is suggested by the diagrammatic section, the 

hydraulic continuity between the two systems beneath tl^ valley floor
o

1 &

I.

n

ft

2^

P* 2 

I &

(§ o" 

ft' c* 

(p 5 

55 g, 

ft Sd 

13 2 

?! 

I o
24 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

would 'be poor; nonetheless, the lateral continuity may be reasonably 

good. Thus, beneath the valley floor the two ground-water reservoirs 

are considered to function mainly as independent flow systems, 

although interflow almost certainly occurs laterally along the contact 

between them.

CARBONATE-ROCK RESERVOIR

The carbonate-rock reservoir crops out in the Spring Mountains, 

underlies the valley fill of Pahrump Valley, and extends southwestward through the Nopah and Resting Spring Ranges into California 

and Chicago Valleys (pi. 1; fig. 5). Except for a small wedge of 

carbonate rocks north of Stewart Valley, the reservoir is terminated by 

structural deformation along the northwest side of Pahrump Valley, 

where quartzite and other poorly permeable rocks crop out. The reservoir probably extends southeastward to Mesquite Valle7-

The carbonate-rock reservoir, which may have a maximum thickness 

of at least 20,000 feet locally, is inferred by the author to be hydraulically continuous beneath the area just described. Cortinuity in the 

carbonate-rocks reservoir probably is achieved principally through 

extensive fractures and to a small degree by localized solution channels. 

Ground water in the reservoir is mainly unconfined in the mountainous 

areas where the carbonate rocks crop out and receive recharge; at 

depth it is confined beneath the tuff in Pahrump Valley. No wells tap 

the carbonate-rock reservoir; hence, the head distribution is not known.

VALJLEY-FILL, RESERVOIR

On the northeast, northwest, and southwest, the valley-fill reservoir 

is terminated by consolidated rocks, but on the southeast it is generally 

continuous with the valley-fill reservoir in Mesquite Valley (pis. 1, 2). 

The southeast edge of the reservoir is arbitrarily regarded to be at the 

surface divide between Pahrump and Mesquite Valleys. The total 

area in Pahrump Valley is about 650 square miles. The bottom of 

the reservoir is the contact between the older lacustrine deposits and 

the older fanglomerate and the underlying tuff. In most places the 

saturated thickness of the reservoir probably exceeds 1,000 feet.

The principal aquifers in the valley-fill reservoir are the coarsegrained deposits which underlie Pahrump and Manse fans and which 

southwestward interfinger with the fine-grained deposits (pi. 1). 

Similarly, aquifers probably occur along the southwest side of the 

valley, where only a few wells have been drilled.

Confined ground water occurs along the toes of Pahrump and Manse 

fans in a narrow band about 2 miles wide and 13 miles long. Prior to 

extensive ground-water development, two large springs Bennetts 

(Pahrump) and Manse Springs discharged nearly 10,000 acre-feet
GROUND-WATER HYDROLOGY 25

per year of water in this area. By 1962 Bennetts Spring WF s dry and 

Manse Spring discharged only a third of its original flow (table 6). 

The area of artesian flow had decreased to only several square miles 

(pi. 2).

SOUBCE AND MOVEMENT OF GKROUND WATEB

Plate 2 shows that in 1962 the movement of ground water in the 

valley-fill reservoir was south westward across the valley; this indicates 

that the principal recharge area is in the Spring Mountains. Similarly, the direction of flow in the carbonate-rock reservoir is presumed 

to be south westward (fig. 5). Although the configuration of the 

water-level contours in the valley fill has been substantially modified 

by pumping along the toes of Pahrump and Manse fans, the overall 

slope of the flow net in the rest of the valley has not been greatly 

altered by pumping.

The contours also show that near the southwest side of the valley 

the ground water moves into the Nopah and Resting Spring Ranges, 

thus demonstrating a hydraulic continuity between the valley-fill and 

carbonate-rock reservoirs in this part of the valley. In 1962 the depth 

to water in wells along the southwest side of the valley ranged from 21 

feet, in Stewart Valley, to more than 200 feet, at the base of the 

Kingston Range. Except in Stewart Valley, there was little possibility 

of water being lost through evapotranspiration. Most ground water 

reaching this part of the valley is transmitted from Pahrump Valley 

southwestward through the mountains to California and Chicago 

Valleys.

Along the southeast side of the valley, ground-water flow is generally 

parallel to the arbitrary boundary between Pahrump and Mesquite 

Valleys (pis. 1, 2). Any extensive ground-water development near 

the boundary would change the flow net and, hence, necessitate a corresponding change in position of the present arbitrary boundary between the two valleys.

At the northwest edge of the valley-fill reservior, the water-level 

contours are generally normal to the consolidated rocks and, therefore, do not indicate any water movement into them. The sm all wedge 

of carbonate rocks north of Stewart Valley provides a potential avenue 

of flow northwestward to the springs in Ash Meadows Last Chance, 

Bole, Big, and Jack Rabbit Springs, which issue at depth from carbonate rocks. Although the head differential is favorable for the potential northwestward flow of ground water in the carbonate-rock 

reservoir, the water-level contours in the valley fill do not indicate this 

possibility, nor does the quality of water in the two areas support this 

thesis. Nevertheless, until the head distribution in the carbonate rocks 

in Pahrump and Stewart Valleys and in the intervening area to the
26 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

northwest is known, the possibility of northwestward flow to the 

springs must remain unresolved.

RECHARGE

Maxey and Jameson (1948, p. 117) estimated that the long-term 

average recharge to Pahrump Valley is about 23,000 acre-feet per year. 

This estimate was based on the assumption that 25 percent of the precipitation at altitudes above 8,500 feet, 20 percent of the precipitation 

at altitudes between 6,500 and 8,500 feet, and little precipitation below 

the 6,500-foot level reach the ground-water reservoirs; virtually all 

recharge occurs in the Spring Mountains. Maxey and Jameson's estimate of recharge is in close accord with that described next, which 

was determined by use of a similar technique.

A method described by Eakin and others (1951, p. 26, 27) is used to 

reappraise the estimated recharge to Pahrump Valley. This method 

is also based on the assumption that a fixed percentage of a given average annual rate of precipitation ultimately recharges the ground-water 

reservoirs. More altitude zones are used, however, to correspond more 

closely to the amounts of precipitation, which ranges from about 4 

inches on the valley floor (alt, about 2,600 ft), to about 28 inches in the 

higher parts of the Spring Mountains (alt, 11,000 ft).

The altitude zones and the estimated average annual precipitation 

and recharge in these zones are given in table 4, which shows that ordinarily no recharge occurs in the zones where precipitation is less than 

8 inches per year. The estimated average annual precipitation in the 

entire area is about 420,000 acre-feet, and the estimated average annual 

recharge from this precipitation is 22,000 acre-feet, o^ only about 5 

percent of the total precipitation. This estimate of recharge is 1,000 

acre-feet less than that made by Maxey and Jameson (1948).

TABLE 4. Estimated average annual precipitation and ground-water recharge in

Pahrump Valley

Precipitation zone (ft)

Above 8,000 _ ______

7,000-8, 000_ _________

6,000-7, 000_ _________

5, 000-6, 000 _._ _ ____

Below 5,000__________

Total (rounded).

Area 

(acres)

29,500 

30,200 

48 , 600 

51,100 

454 , 000

613,000

Estimated annual precipitation

Range 

(in.)

>20 

15-20 

12-15 

8-12 

<8

Average 

(ft)

1. 75 

1. 46

1. 12 

. 83 

. 50

Average 

(acre-ft)

51,600 

44,100 

54,400 

42 , 400 

227 , 000

420 , 000

Estimated recharge

/ ssumed 

percentage 

of precipitation

20 

15

7 

3 

0

Acre-feet 

per year

10,300 

6,600 

3,800 

1,300

1 22,100

1 Except for several hundred acre-feet of recharge in the Nopah and Resting Spring Ranges, virtually all 

the estimated recharge occurs in the Spring Mountains.
GROUND-WATER HYDROLOGY 27

The recharge, as estimated by this method, may occur in three ways: 

by direct infiltration of rainfall in areas that are generally higher than 

5,000 feet, by seepage loss from streams in the mountains and in the 

valley, and by lateral movement from the carbonate-rock reservoir, as 

well as from fractures in the other consolidated rocks to the valley-fill 

reservoir. Because there are many unknown factors in the spatial 

distribution both of recharge to and of interflow between ground-water 

reservoirs, no direct estimates of recharge to each of the two reservoirs 

could be made. In the section "Discharge," however, the probable 

division of the total average annual recharge is computed indirectly 

to be about 12,000 acre-feet to the valley-fill reservoir and about 10,000 

acre-feet to the carbonate-rock reservoir.

DISCHARGE

Ground-water discharge from Pahrump Valley occurs by pumping 

from wells, by evapotranspiration, through springs, and by subsurface 

outflow principally to areas southwest of the valley. Prior to the construction and use of large-capacity wells in about 1912, virtually all 

the discharge was by natural processes. By 1962, pumpage constituted 

about 60 percent of the total discharge from the valley.

In this section of the report, estimates of discharge are made for 

natural conditions and for the 4-year period 1959-62; some discharge 

records that date back discontinuously to 1875 are also presented (table 

6). For the valley-fill reservoir, direct estimates are made for the several elements of discharge; but for the carbonate-rock reservoir, only 

an indirect estimate of discharge by subsurface outflow can be made 

from the present data.

VALLEY-FILL, RESERVOIR

SPRINGS

Before large-scale withdrawals from wells began, ground water 

under artesian pressure issued from two large springs in the valley fill 

near the toes of Pahrump and Manse fans. Bennetts Spring 

(Pahrump Spring), originally the larger of the two, is approximately 

a quarter of a mile south of the community of Pahrump (pi. 1). 

Manse Spring is about 6 miles southeast, near the headquarters of the 

Manse Ranch.

During the initial phases of ground-water development in the valley, 

diversions from the large springs provided virtually all water for 

irrigation. Subsequently, ground-water development from wells tapping the valley-fill reservoir has caused a reduction of artesian pressure and a continual decline of the spring discharge. The artesian 

head in the vicinity of the two large springs was sufficiently lowered
28 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

by 1959 to cause Bennetts Spring to become dry and the, flow from the 

Manse Spring to decrease to about a third of the original flow. The 

total discharge from these two springs has dwindled from nearly 

10,000 acre-feet per year under natural conditions to at out 1,400 .acrefeet per year in 1962 (table 6).

Several small springs issue from the scarps that trar sect the valley 

fill in the southern part of Pahrump Valley. These include Stump 

Spring, southeast of Hidden Hills Ranch, Brown's Spring, and several 

other unnamed springs and seeps northwest of the ranch headquarters 

(pi. 1). The combined discharge of these small springs probably does 

not exceed 50 acre-feet per year (table 6, col. 4). Their flow in 1962 

had not been affected by ground-water development.

The term "net spring discharge" is used to describe that part of the 

total spring discharge that is permanently removed from the valley-fill reservoir by evapotranspiration downstream from the spring 

orifices. The total spring discharge less the net spring discharge 

is the amount that returns to ground water in the vrlley-fill reservoir. As described in the following section of this report, under 

natural conditions approximately 7,000 acre-feet of trs total spring 

discharge of nearly 10,000 acre-feet per year (table 6) was consumed 

by evapotranspiration. Thus, in approximate terms, the net spring 

discharge prior to pumping averaged about 7,000 acre-feet per year, 

and the 'amount that returned to ground water averaged about 3,000 

acre-feet per year.

During the period 1959-62, the total spring discharge averaged 

only about 1,600 acre-feet per year and was almost wholly from 

Manse Spring. Approximately one-third of the anual flow of 

Manse Spring occurred in the nongrowing season from about November 10 to March 15. During this 4-month period, most spring 

discharge percolated into the ground and returned to the groundwater reservoir. Accordingly, the net spring discharge in the period 1959-62 probably averaged about 1,000 acre-feet per year.

EVAPOTRANSPIRATION

Evaporation from bare soil and transpiration by phreatophytes 

occur along stream channels downstream from the springs, along 

drainage ditches that convey tail-waste from irrigated areas, around 

the playa in Stewart Valley, and locally in the lowlands west of the 

community of Pahrump. The areal extent of phreatophytes in 1961 

is shown on plate 3. Areal photographs made in 1952 show that the 

distribution of phreatophytes was about the same in 1P52 as in 1961. 

Phreatophyte areas formerly supported by spring flow under natural 

conditions were receiving irrigation tail waste in 1961 from irrigated
GROUND-WATER HYDROLOGY 29

areas through the same channels that originally carried the spring 

flow. Consequently the phreatophyte areas and the amount of water 

probably used by them have not been appreciably altered from the 

natural state.

The principal phreatophytes include mesquite, saltgrass, saltbrush, 

saltcedar, and cottonwood. The areas, estimated rates of use, and estimated evapotranspiration from areas of phreatophytes rre shown 

in table 5. The estimated use also includes the evaporation from 

bare soil in and near the areas of phreatophytes. Table 5 shows that 

the estimate^, annual evapotranspiration from spring discharge and 

irrigation tail-waste was about 7,000 acre-feet and that f^om areas 

of shallow ground water, about 3,300 acre-feet.

TABLE 5. Estimated annual evapotranspiration in Pahrump Valley

Phreatophytes

From spring discharge and irrigation tail-waste : 

Mesquite __

Saltgrass and saltbrush

Saltcedar,

Cottonwood

Subtotal (rounded)

From ground water in the valley-fill reservoir: 

Mesquite

Total (rounded).

Phreatophyte 

area 

(acres)

1,600

450

35

10

2, 100

1,000

3, 100

Rate of 

use '

(ft)

3.3

3. 0

6. 0

5. 5

3.3

Evapotranspiration 2 

(acre-ft)

5, 300

1, 400

200

50

7,000

3,300

10, 000

1 Modified to reflect climatic and hydrologic conditions in Pahrump Valley: mesquite (P.obinson, 1958, 

p. 38), saltgrass (Young and Blaney, 1942, p. 129), saltcedar (Gatewood and others, 195"), p. 150-152), 

and cottonwood (Blaney and Harris, 1952).

2 Includes evaporation from bare soil in and near phreatophyte areas.

SUBSURFACE OUTFLOW

The water-level contours (pi. 2) show that ground water in the 

valley-fill reservoir moves southwestward into the carbonate-rock reservoir in the Nopah and Resting Spring Ranges. The outflow from 

the valley-fill reservoir can be estimated by use of a form of Darcy's 

law:

0 = 0.00112 TIL,

in which Q is the discharge, in acre-feet per year; T is the coefficient 

of transmissibility, in gallons per day per foot; / is the hydraulic 

gradient, in feet per mile; and L is the width, in miles, of the cross 

section through which outflow occurs (Ferris and others, 19°2, p. 73). 

The factor 0.00112 is used to convert gallons per day to acre-feet per 

year.
30 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

The logs of wells in the southwestern part of the valley show that 

the valley fill is dominantly clay and silt; hence, the coefficient of transmissibility probably is low and may be only about 1,000-5,000 gallons 

per day per foot. The hydraulic gradient averages about 20 feet per 

mile along the 35-mile length of the valley trough. Thus, by substituting these values in the above equation, this preliir inary estimate 

of outflow is computed to be about 2,000 acre-feet per year. Because 

little historic change in hydraulic gradient has occurred in this part of 

the valley, the subsurface outflow remained nearly constant through 

1962. The pumping in an area 5-10 miles northeast of th0, valley trough 

and in the southern part of the valley may eventually reduce the 

hydraulic gradient and thereby proportionately reduce the outflow.

PUMPAGE

Practically all discharge of ground water by pumping and by flow 

from artesian wells occurs along the toes of Manse and Pahrump fans 

on the northeast side of the valley floor. After the first successful 

flowing artesian wells were drilled in 1910, the number of new wells 

drilled and the annual discharge increased slowly until the mid-1940's. 

At that time many wells were drilled and large-capacity pumps were 

installed. From the mid-1940's through 1962 the annual discharge 

from wells increased from an estimated 10,000 acre-feet to about 

28,000 acre-feet. During the period 1959-62 the discharge averaged 

about 26,000 acre-feet per year. Discharge from wells in 1962 was 

about three times that from springs in 1875.

Table 6 lists the discharge from wells and springs fc^ all years for 

which records or estimates are available. Figure 6 shows the areal 

distribution and approximate magnitude of well and spring discharge 

in 1961. Figure 6 shows that the largest areas of well r,nd spring discharge are centered around the Fowler and Manse Ranches, where the 

discharge was about 5,700 and 6,200 acre-feet, respectively.

As described in "Storage capacity1 ' of this report, approximately 

1,000 acre-feet of irrigation water infiltrated the valley-fill reservoir 

each year during the period 1959-62. The net pumping draft, or 

the amount of ground water permanently removed from the reservoir 

by pumping, therefore, was about 25,000 acre-feet per year for that 

period. Moreover, an estimated 7,000 acre-feet per year of the pumped 

water ran off as tail-waste and, as previously mentioned, was consumed by evapotranspiration. These estimates suggest that approximately 18,000 acre-feet, or 70 percent, of the annual pumpage during 

this period was consumptively used for the irrigation of about 6,500 

acres of crops that is, about 2.8 acre-feet per irrigated acre.
GROUND-WATER HYDROLOGY 31

TABLE 6. Approximate discharge, in acre-feet, from springs and wells in Pahrump

Valley, 1875-1962

[Discharge measurements from records of the Nevada State Engineer, except as indicated]

Year

1875.........

1877.........

1910 

1913 -.-

1916.---....

1927..... .

1937... -..-__

1939 ......

1940 --...

1943 __

1946 -

1947. -. ...

1948.........

1949 

1951 .-

1952 

1953... .-_-_.

1954 --...

1955 -

1956 ___

1957 -...

1958 .-

1959 ..

1960 -

1961. ...

1962 -

Manse

2\300

3 4, 300

52,300

61,900

2,200

2,200

2.2CO

1,500

2,000

1,900

1,800

1,900

1,800

1,700

1,800

1,700

1,800

1,700

1,500

1,400

Springs 1

Bennetts

2 5, 400

s 3, 400

61,600

4,100

3,2CO

2,600

4, ICO

2,000

2,000

1,400

0

0

0

Other

'60

Wells

0

4 500

M,300

M,600

3,300

3,500

16,300

15, 500

19, 100

16,100

25, 100

27,200

23,300

21, 300

22,900

25,300

28,500

27,600

Total

29,700

510,000

9,600

8,900

7,000

18,500

17,000

21, 000

18,000

27,000

29,000

27,000

26,000

27,000

Kemari s

estimate of well discharge. 

Do.

Do.

Do.

Do.

39 wells in use

Do.

Do.

1 Flow from springs estimated on the basis of one or more measurements a year.

2 Maxey and Jameson (1948, p. 10).

3 Maxey and Jameson (1948, p. 78).

4 Clark County Keview, Feb. 22,1913.

5 Waring, G. A. (1921, p. 61-66).

6 George Hardman (written commun., 1935).

7 Estimated by author. The discharge has probably remained constant during historic period.

Pumpage for domestic and other uses probably was cnly a few 

hundred acre-feet per year for the period 1959-62. This amount of 

pumpage is so small that it is within the limits of error of the estimated 

pumpage for irrigation. Therefore, the discharge from wells (table 6) 

is considered to be the total pumpage in Pahrump Valley.

CARBONATE-ROCK RESERVOIR

Virtually all discharge of ground water from the carbonate-rock 

reservoir in Pahrump Valley is by subsurface outflow beneath topographic divides to Chicago and California Valleys and possibly to 

Ash Meadows (pi. 2). A minor amount of discharge may occur in 

the vicinity of Sixmile Spring, where several seeps are present adjacent 

to carbonate-rock outcrops (pi. 1). Sixmile Spring apparently has 

never flowed; Waring (1921) described it as wrater standing about 

6 feet below the surface in a low sandy mound. In 1962 the water 

was at about the same level, and standing about 10 feet above the 

regional water level in the valley fill; the higher head may be due to 

the flowr system in the carbonate-rock reservoir.
32 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

116°05' 

36°20'

Diameter of circle 

irdicates ground 

water discharge

Includes about 

J.~-- 1500 acre-fe 

of spring dis 

from Manse

FIGURE 6. Approximate area and magnitude of ground-water discharge from 

springs and wells in Pahrump Valley in 1961.

A crude estimate of the average annual subsurface outflow is indirectly computed as the difference between the total recharge (22,000 

acre-ft, table 4) and the natural discharge from the valley-fill 

reservoir by evapotranspiration (about 10,000 acre-ft, table 5), or 

about 12,000 acre-feet. Of this annual outflow from the carbonaterock reservoir, approximately 2,000 acre-feet is supplied from the 

valley-fill reservoir along the southwest side of the valley (p. 30) ; 

the rest, 10,000 acre-feet, is supplied by flow at depth from the recharge
GROUND-WATER HYDROLOGY 33

area in the Spring Mountains (fig. 5). These crude estimates suggest 

in turn that the division of total recharge between the two reservoirs 

is 12,000 acre-feet to the valley-fill reservoir and 10,000 acre-feet to 

the carbonate-rock reservoir.

The ultimate disposition of all the estimated 12,000 acre-feet of 

subsurface outflow to adjacent valleys was not resolved during this 

study. The geologic controls suggest that most of the outflow moves 

southwestward through a thick section of carbonate rocks beneath the 

Nopah and Resting Spring Eanges; part may move northwestward 

through a thin section of carbonate rocks or along major fa.ult zones 

to the springs at Ash Meadows. Most springflow at Ash Meadows, 

however, probably is derived from sources to the north (I. J. Winograd, U.S. Geol. Survey, oral commun., 1965).

In Chicago Valley, the phreatophytes (pi. 3), covering an area of 

about 600 acres, probably discharge about 2,000 acre-feet p°r year 

far more than the local recharge. Tecopah Springs, at the routhwest 

end of California Valley (pi. 3), and other springs may have a combined total discharge of 1,000-2,000 acre-feet per year. But even if all 

this discharge of 3,000-4,000 acre-feet per year were supplied from 

Pahrump Valley and none were supplied from local sources which 

is not true it would account for only about a fourth of the estimated 

subsurface outflow from Pahrump Valley.

GROUND WATER IN STORAGE 

STORAGE CAPACITY

The valley-fill reservoir in Pahrump Valley contains a large amount 

of ground w^ater that is moving slowly from areas of recharge to points 

of discharge. The amount stored, or in transient storage, in the reservoir is many times the average annual recharge and represents water 

accumulated during several hundred years. The amount of water 

contained in a selected volume of the valley-fill reservoir is computed 

by multiplying the volume of saturated material by the specific yield 

of the material. As defined by Meinzer (1923, p. 28), specif c yield is 

the ratio of (1) the volume of water which the material, after being 

saturated, will yield by gravity to (2) the volume of the material. 

This ratio is stated as a percentage.

An estimated specific yield of 15 percent is assigned for determinations in this report because no tests were made to ascertain the specific 

yield of the valley-fill deposits in Pahrump Valley. Studies made in 

other areas show that the specific yield of valley fill commonly ranges 

from 7 to 20 percent. (For example, see Davis and others, 1959, p. 

206-211, 242-253; and Thomasson and others, 1960, p. 283-286, 292.)

To show that a large amount of ground water probably is stored
34 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

in the valley-fill reservoir in Pahrump Valley, an estimate is made for 

the upper 100 feet of saturated material. The reservoir area is about 

650 square miles, or about 400,000 acres; the selected saturated zone is 

100 feet thick; and the assigned specific yield is 15 percent. The estimated ground water in storage is the product of theee three values, 

or about 6 million acre-feet that is, the water in storage in each foot 

of saturated material is about 60,000 acre-feet, which is equivalent to 

about 5 years of recharge to the valley-fill reservoir.

DEPLETION OF GROUND WATER IN STORAGE

Changes in the amount of ground water in storage are indicated by 

water-level fluctuations and occur chiefly in response to changes in the 

rates of recharge and discharge. Pumping from wells commonly 

places a large stress on a ground-water system and, if prolonged or 

intense, generally results in a marked decline in water levels and a 

corresponding decrease in stored water.

Development of ground water in the valley-fill reservoir was started 

in the vicinity of Manse and Bennetts Springs. Since about 1948 the 

water level in well S21/54 lOaac, near Manse Spring, and in well 

S20/53-24caa, near Bennetts Springs, has been declining because of 

pumping (fig. 7). In these two areas, pumping had caused water 

levels to lower more than 25 feet by 1962. Hydrographs of wells 

N24/8-26bac and Sl9/53-32aaa, which are farther from heavypumping areas, show only minor changes in water level during the 

period of ground-water development (fig. 7).

Plate 4 shows the net change in water levels for the 3-year period 

February 1959-February 1962. Areas in which water levels have declined 5 feet or more are around major centers of pumping and total 

about 13,000 acres; areas having less than 5 feet of water-level decline 

are ill-defined but probably total at least four times as much acreage. 

The total volume of deposits dewatered during the 3-year period was 

about 300,000 acre-feet. Determined with the assigned specific yield 

of 15 percent, this total volume indicates a probable storage depletion 

of roughly 45,000 acre-feet, or about 15,000 acre-feet per year.

INCREASE OF GROUND WATER IN STORAGE

Infiltration of irrigation water along diversion ditches and in irrigated areas during the period 1959-62 caused water levels to rise 1-2 

feet each year in three areas southwest of the principal irrigated areas 

(pi. 4). The estimated total return flow in these areas as represented 

by the net increase in storage, is the product of (1) th?, area of about 

7,000 acres, (2) the average water-level rise of about 0.8 foot, and (3) 

the assigned specific yield of 15 percent, or a net increase of approximately 1,000 acre-feet. Areas of water-level rise generally dissipate
GROUND-WATER HYDROLOGY 35

I I I Well S 21/54-10 aac

X/VyV\A

o 

S 30

u_? 40

of 

< 50

0

~N

V

^v-^

V

\,fl^y

^VV

We

\l

IS20/E

,Well

3-24CJ

aved

a

1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1359 1960 1961 

HYDROGRAPHS OF TWO WELLS SHOWING WATER-LEVEL FLUCTUATIONS IN CONFINED AQUIFERS

1953 1954 1955 1956 1957 1958 1959 1960 1961

Well S 19/53-32aaa

1953 1954 1955 1956 1957 1958 1959 1960 1961 

HYDROGRAPHS OF TWO WELLS SHOWING WATER LEVEL FLUCTUATIONS IN UNCONFINED AQUIFERS

FIGURE 7. Water-level fluctuations in selected wells tapping the valley-fill 

reservoir in Pahrump Valley.

after each successive year's irrigation season; hence, the computed 

return-flow value of about 1,000 acre-feet mainly indicates the annual 

increment of return flow, or recycled water.

WATER BUDGET

The water budget for Pahrump Valley brings together and compares the estimated elements of recharge and discharge and the changes 

in amount of ground water in storage for natural conditions and for 

the 4-year period 1959-62. This analysis includes the carbonate-rock 

and valley-fill reservoirs and shows the magnitude of the errors involved in the estimates made in the preceding sections of this report. 

These estimates are summarized in table 7 and show the marked change 

that has occurred in the ground-water regimen of the valley-fill reservoir from conditions prior to ground-water development to conditions 

of moderately large withdrawals in the period 1959-62.
TABLE 7. Water-budget analysis, in acre-feet per y

[Boldface numbers indicate steps in ana

Budget item

Recharge (1)

Discharge: 

Springs:

Evapotranspiration:

Pumpage:

Total (2) 

Difference (3) = (1-2) . 

Natural cond

Carbonaterock reservoir

1 10, 000 

Minor

Minor

Minor 

10, 000

0

10, 000 

0 

0 

0

Valley-fi

reservo

2 12, 

(10, 

(-3,0

3 7, 

3

2

12

1 Computed by difference: total recharge less recharge to valley-fill reservoir. 

- Assumed equal to total discharge under natural conditions from the valley-fill 

reservoir. 

3 Total amount was consumed by evapotranspiratioii (p. 29).

4 Of the 26,00

acre-feet was co

5 Average for 
GROUND-WATER HYDROLOGY 37

Pumping from the valley-fill reservoir probably has not yet intercepted any of the subsurface outflow from the valley. Table 7 shows 

that the annual outflow of 10,000 acre-feet from the carbonate-rock 

reservoir and the outflow of 2,000 acre-feet from the valley-fill reservoirs to the carbonate-rock reservoir have therefore remained constant. 

For two reasons, moreover, the water budget for the carbonate-rock 

reservoir balances: (1) it is assumed that no change in storage has 

occurred; and (2) the estimates of recharge and discharge, which were 

determined by difference, were assumed to be equal. Similarly, the 

water budget for natural conditions in the valley-fill reservoir balances.

During the period 1959-62 the estimated total annual discharge from 

the valley-fill reservoir increased from about 12,000 acre-feet under 

natural conditions to approximately 31,000 acre-feet nearly a threefold increase (table 7). As a result the estimated annual natural discharge has been reduced from 12,000 acre-feet to 6,000 acre-feet, and 

the ground water in storage has been depleted at an estimated average 

rate of 15,000 acre-feet per year.

The water-budget analysis for the period 1959-62 also shows a discrepancy of 4,000 acre-feet per year in the difference between the estimated recharge and discharge and the estimated storage depletion. 

This imbalance shows a magnitude of error of about 25 percent in the 

several estimates of recharge, discharge, and storage change. Except 

for the estimates of pumpage and storage depletion, the estimates of 

other budget items are too small to affect the imbalance. On°i probable 

source of error is the estimated return to storage of irrigation water, 

which seems IOWT only 4 percent of the pumpage. In other areas the 

return commonly ranges from 25 to 40 percent of the total pumpage 

(Thomasson and others, 1960). The estimated storage depletion of 

15,000 acre-feet per year may also be considerably in error, owing principally to the poor control of area and thickness in determining the 

volume of deposits dewatered in the areas of pumping.

PERENNIAL YIELD

The perennial yield of a ground-water reservoir may be defined as 

the maximum amount of water of usable chemical quality that can be 

withdrawn and consumed economically each year for an indefinite 

period of time. If the perennial yield is continually exceeded, water 

levels will decline until the ground-water reservoir is depleted of water 

of usable quality or until the pumping lifts become uneconomical to 

maintain. Perennial yield cannot exceed the natural recharge to an 

area indefinitely; it is ultimately limited to the maximum amount of 

natural discharge that can be salvaged for beneficial use.
38 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

Before pumping began, the natural discharge from Prlirump Valley 

comprised about 10,000 acre-feet per year from the carbonate-rock 

reservoir and about 12,000 acre-feet per year from the valley-fill 

reservoir (table 7). During the period 1959-62, when pumpage averaged about 26,000 acre-feet per year, natural discharge from the valleyfill reservoir was about 6,000 acre-feet per year less thar before pumping began, but probably little or no decrease had occurred in the 

discharge from the carbonate-rock reservoir. To estimate the maximum amount of natural discharge that can be salvaged, the future 

cause-and-effect relation between pumping and natural discharge must 

be evaluated. The following estimates and assumptions are made to 

ascertain this relation:

1. The 1962 areal pattern of pumping on the Nevada side of Pahrump 

Valley will probably not change appreciably in the near future, 

but pumpage may increase. As a result, Manse Spring probably 

will stop flowing, and evapotranspiration from areas of shallow 

ground water west of Pahrump will markedly decrease (pi. 3). 

The total additional salvage of natural discharge may ultimately 

be as much as 4,000 acre-feet per year.

2. Pumping on the California side and near the south end of Pahrump 

Valley may markedly increase. From February 1959 to February 1962 (pi. 3), pumping lowered water levels in this area 

about 4 feet. Large withdrawals will reduce the ground-water 

outflow from the valley-fill reservoir to the carbonate-rock-reservoir possibly as much as 50 percent, or about 1,000 acre-feet per 

year. No other development on the California side seems feasible 

or imminent as of 1962.

3. At the 1962 rate or at a higher rate, prolonged pumping from the 

valley-fill reservoir will probably somewhat reduce subsurface 

outflow from the carbonate-rock reservoir to adjacent valleys. 

Until both the cause-and-effect relation of the future pumping 

regimen and the subsurface outflow from the carbonate-rock reservoir can be more thoroughly evaluated, the salvable outflow from 

the carbonate-rock reservoir is assumed to be only 1,000 acre-feet 

per year.

4. The carbonate-rock reservoir probably occurs at a depth of more 

than a thousand feet beneath most of Pahrump Valley. Future 

drilling of deep wells in an attempt to tap water in fracture zones 

in the carbonate rocks seems only a remote possibility. Accordingly, the possibility of salvaging outflow from this reservoir by 

pumping also seems remote at this time.

Based on these estimates and assumptions, the maximum amount of 

natural discharge that can be salvaged probably is not more than 12,000
GROUND-WATER HYDROLOGY 39

acre-feet per year, which is 6,000 acre-feet per year more than the 

yearly amount salvaged during the period 1959-62.

In summary, the maximum salvable discharge comprises tH following (annual estimates) :

1. All net spring discharge, which was originally 7,000 acre-feet;

2. Possibly as much as 3,000 acre-feet of evapotranspiration in areas 

of shallow ground water;

3. About 1,000 acre-feet of subsurface outflow from the valley-fill 

reservoir;

4. Possibly 1,000 acre-feet ,of outflow from the carbonate-rock reservoir to adjacent valleys (table 7).

Thus, the estimated perennial yield of Pahrump Valley also probably 

does not exceed 12,000 acre-feet. This means that about 10,000 acrefeet per year of subsurface outflow probably is not salvable and that, 

ultimately, any net pumping draft in excess of 12,000 acre-feet per 

year will be supplied from ground water in storage.

OVERDRAFT

Overdraft may be defined as the amount by which the net pumping 

draft exceeds the perennial yield. During the period 1959-62 the 

estimated net pumping draft averaged 25,000 acre-feet per year (table 

7), or approximately twice the estimated perennial yield of 12,000 acrefeet. Annual overdraft in Pahrump Valley during this period thus 

averaged about 13,000 acre-feet. Even if the net pumping draft was 

somewhat smaller than that estimated (p. 37), it still would have 

exceeded the estimated yield.

Table 6 shows that pumpage increased during the last several years 

of record. As long as annual pumpage continues to increase, overdraft also will continue to increase. Over the long tern: this deficiency will be supplied almost wholly from ground water in storage 

in the valley-fill reservoir. This depletion in turn will be manifested, 

principally in the areas of large withdrawals, by the continued downward trend of water levels, as shown in figure 7, and by increased 

pumping lifts.

Continued overdraft and the accompanying increase in pumping 

lifts will clearly result in an increase in pumping costs. The electrical 

energy required to lift water from a well to the point of discharge 

commonly is 2 kilowatt-hours per acre-foot per foot of lift. For 

example, using this energy factor, 200 kilowatt-hours would be required to lift 1 acre-foot of water from a pumping level 100 feet below 

the discharge point. If the pumping lift should double in the future, 

the kilowatt-hours per acre-foot would also double, provided that the 

well and pumping plant efficiencies were to remain nearly the same.
40 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA 

CHEMICAL QUALITY OF WATER

Chemical analyses made by several agencies are available for water 

from 43 wells and 5 springs in Pahrump Valley and vicinity. Of these 

analyses, 18 are "complete" analyses and 30 are "partial" analyses 

(specific conductance, chloride, hardness, and pH). Water-temperature data are also available for most of the sampling points. Representative chemical analyses are shown in table 8, and the range in 

chemical quality of all "complete" analyses is shown in table 9. Plate 

5 shows the chemical quality of water and its variation from one part 

of the valley to another.

The scope of this section is limited to brief presentations of the 

variations in water quality and of the suitability of the water for 

irrigation use. A brief analysis is made of the geothermal gradient in 

the valley-fill reservoir.

VARIATIONS IN QUALITY

Along the northeast side of Pahrump Valley most ground water in 

the valley-fill reservoir is of calcium-magnesium bicarbonate type 

(pi. 5), indicating the abundance of carbonate rocks in the Spring 

Mountains, where most recharge occurs. The dissolvec1 -solids content 

of the ground water increases as the water moves southwestward 

across the valley. Most of the water analyzed, however, was from 

shallow wells, and its quality may not be indicative of the quality of 

water in the deeper aquifers. Most analyses of water sampled in the 

vicinity of the Nevada-California boundary showed an increase in 

magnesium concentration in relation to calcium; consequently, magnesium is the predominant cation in solution. Northeast of the boundary the total dissolved-solids content is generally less than 300 ppm 

(parts per million).

Analyses of ground water sampled along the southwest side of the 

valley showed a wide variation in quality. In Stewart Valley the 

water generally has a high sodium content, and locally high contents 

of magnesium, sulfate, and chloride. The total dissolved-solids content ranges from about 520 ppm (well N24/8-6dcd) to about 40,000 

ppm (well N25/7-25ccc, not shown on pi. 5). At the north edge of 

the playa in Pahrump Valley, the water (well N22/9-5o.bc) is high in 

magnesium, sodium, sulfate, and total dissolved-solids content. Elsewhere on the California side of Pahrump Valley, the water is generally 

of magnesium bicarbonate type, having a total dissolvec1 -solids content 

of less than 500 ppm.
TABLE 8. Chemical analyses of typical irrigation wa

[Constituents in parts per million, except as indicated. COs not present. Analys

Selected wells

S]9/52-36bdd___-- ...._....

S19/53-9bbc_. .-.. ---------

Sl9/53-21aaa_. ------------

S20/53-20bba_ _-.___-_-_ 

S21/54-16ada------------

S22/54-24dcc i- -__-_ _-..

Depth of well

(ft)

389

746

595

662

902

795

1.050

680

Date ofcollection

4-29-59

4-24-59

4-29-59

4-29-59

5-22-59

2-10-55

5-28-53

5-10-57

Temperature

(°F)

69.5

73

72.5

79.5

74

0 

5£ 

a

CO

26

21

20

17

23

16

20

20

Calcium (Ca)

30

46

47

50

62

53

36

69

Magnesium 

(Mp)

22

26

28

22

60

22

24

26

Sodium (Na)

13

28

7.5

6.9

11

7.1

9.2

6.9

Potassium (K)

2.2

4.0

1.6

2.7

.8

1.5

.4

Bicarbonate 

(HC0 3)

199

280

269

242

257

224

186

281

6

52-

3

 2

CO

2

3

2

2

17

4

4

5

Analysis by California Department of Water Resources.
42 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

TABLE 9. Summary of chemical quality of ground water in Pahrump Valley 

[Constituents in parts per million except as indicated]

Silica (SiO2 )____________ _______

Iron (Fe) : 

Total__-__ ________________

Dissolved

Calcium (Ca)

Magnesium (Mg)

Sodium (Na)

Bicarbonate (HCOs)

Carbonate (CC>4)

Sulfate (SO4 )------------_----

Chloride (Cl)___. ______________

Fluoride (F)____ ______

Nitrate (NO3 ) --_________..____

Boron (B)_ ___________________

Dissolved solids (calculated) 

Hardness as CaCCV. 

TotaL_____. ______________

Noncarbonate

Specific conductance (micromhos at 25°C)___

pH__.________________________

Percent sodium _

Maximum

90

3. 0

1. 4

264

594

13, 000

1,980

1, 450

57

8, 830

15, 700

' 1. 4

42

54

40, 600 

3, 100

2,780

50, 300

9. 3

83

Minimum

3. 6

. 00

. 00

5.6

8.3

5. 8

.3

125

0

14

2. 0

. 1

0

.00

220 

54

0

348

7. 4

5

Mediin

20

0. 10

. 01

43

29

23

3 1

238

0

55

16

.3

1. 5

.07

301 

223

17

515

7. 9

18

Number of 

determinations

26

17

6

40

40

40

40

40

40

40

40

28

27

37

30 

38

29

30

36

31

Water in Sixmile Spring is of calcium bicarbonate typ°, and is, therefore, different from the types of water in nearby wells which tap the 

valley-fill reservoir (pi. 5). The spring-water type suggests that it is 

derived from the carbonate-rock reservoir.

SUITABILITY OF THE WATER FOB IRRIGATION

Most water users in Pahrump Valley are interested in the suitability 

of the water for irrigation, because the economy of the valley is dependent almost wholly on irrigation agriculture. Table 9 briefly summarizes the range of principal chemical constituents in the ground 

water, listing the maximum, minimum, and the median values for each 

constituent and the number of samples on which these values are based. 

Several characteristic properties of the water are also listed; these 

include dissolved solids, hardness, specific conductance, pH, and percent sodium (the ratio of sodium ions to the total number of cations in 

solution). Table 8 shows the chemical character of the ground water 

in eight selected wells in and adjacent to the principal rreas of pumpage. Of the factors shown in this table, the most critical with respect 

to the suitability of water for irrigation are the dissolved-solids content and the concentration of toxic elements, such as boron. Other 

factors, such as soil type and composition, climate, and methods of 

water application also affect the suitability of water for irrigation.
CHEMICAL QUALITY OF WATER 43

Extensive irrigation in the poorly drained central part of Pahrump 

Valley may cause an eventual rise in the water table that will result in 

water logging and drainage problems. To maintain irrigation on a 

permanent basis in these areas, construction of drainage ditches may 

be required to control the depth of the water table and to prevent an 

excessive increase in dissolved-mineral constituents in the soil and in 

the underlying ground water.

Eecirculation^, or reuse, of water also tends to increase the dissolvedsolids content. As water levels along the base of the Manse and Pahrump fans continue to decline, recirculation of irrigation water 

probably will increase because of the accompanying decrease in 

ground-water movement away from the pumped area. The recirculation of water through several cycles of irrigation in the same area 

will tend to increase the concentration of dissolved solids.

The ground water in most of Pahrump Valley is of moderate salinity 

and is low in sodium content. Water that is low in sodium content can 

be used successfully for irrigation of nearly all soils. After a small 

amount of leaching, the soil in the principal irrigated areas and at 

the south end of the valley is satisfactory for irrigation.

TEMPERATURE

The temperature of ground water is closely related to the temperature of the aquifer in which the water occurs. Therefore, insofar 

as the temperature of the water is in equilibrium with that of the 

aquifer, an increase in water temperature with depth probably is 

indicative of the geothermal gradient in the area. Residual heat 

from metamorphism, from crushing and shearing during faulting, 

or from underlying bodies of hot igneous rock may cause local anomalous temperatures both areally and at depth. Difference in thermal 

conductivity of different rock types may also result in different 

geothermal gradients in the same area.

The regional geothermal gradient is controlled by the transfer of 

heat from great depths within the earth toward the land surface. 

Hence, if the regional geothermal gradient is not altered by localized 

thermal activity, the temperature of the ground and of the water it 

contains will increase with depth. If the rate of temperature change 

with depth is known, the temperature of water being discharged from 

a well or spring may indicate the depth from which the water is coming. Although variations in the heat-flow pattern within the zone of 

saturation may result from many causes, the heat from the interior 

of the earth probably is fairly constant throughout the study area.

Near-surface temperatures approximate the mean annual air temperature, but they may vary slightly in response to expornre or to 

environmental changes caused by the activity of man.
44 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

The mean annual air temperature in Pahrump Valley is approximately 65 °F, and the temperature of ground water from wells and 

springs in the valley area should equal or exceed that amount. In figure 8, 65 measurements of ground-water temperature are plotted 

against the depth of the well from which the water was discharged. 

Temperatures were measured at the point of discharge and possibly are 

somewhat lower than the water temperature in the principal aquifer 

supplying water to the well. The average temperature gradient for 

the area, as shown by the approximate curve of best fit in figure 8, is 

about 1°F for each 85 feet in depth.

Figure 8 is useful in estimating the approximate depth of the 

source of water. For example, the water temperature of Bennetts 

and Manse Springs averages about 75° and 76°F, respectively. This 

temperature is about 10°-11° warmer than the temperature of the 

shallowest water in the zone of saturation, which is at mean annual 

air temperature. This suggests that if the water from Bennetts 

Spring originated from a single water-bearing zone, the depth of 

the zone would be about 850 feet. Also, water discharged at the Manse 

Spring probably would originate from a depth of about 900 feet. 

If the spring discharge is a mixture of water derived from different 

depths, however, its temperature would be a composite of the temperatures of all the contributing aquifers, and the computed depths of 

850-900 feet, therefore, would represent average depths.

SUMMARY AND CONCLUSIONS

This second appraisal of the ground-water resources of Pahrump 

Valley has revealed the existence of two reservoir systems one in 

the valley fill, which has been extensively developed for irrigation, 

and the other in the underlying carbonate rocks, which is undeveloped. 

Of the estimated total average annual recharge of 22,000 acre-feet, 

approximately 12,000 acre-feet is believed to leave the valley by subsurface outflow through the carbonate rocks to adjacent areas. 

Pumping from the valley-fill reservoir in the future may salvage 

only 2,000 acre-feet per year of this outflow. This possibility suggests in turn that the salvable discharge may be only 12,000 acre-feet 

per year, or that the perennial yield of the valley may be limited to 

this amount of water over a long period of time.

The net pumping draft in the 4-year period 1959-62 averaged about 

25,000 acre-feet per year, which is about twice the estimated perennial 

yield, or an overdraft of about 13,000 acre-feet per year. Over the long 

term the overdraft will be supplied from ground water stored in the 

valley-fill reservoir. This will result in declining water levels, 

increased pumping lifts, and, hence, increased pumping costs.
SUMMARY AND CONCLUSIONS 45

100 -

300 -

400

600

Q 700 -

800 -

900 -

1000 -

1100

60 65 70 75 80 85 90 

TEMPERATURE OF THE GROUND WATER, IN DEGREES FAHRENHEIT

FIGURE 8. Approximate geothermal gradient in 1'ahrump Valley.
46 HYDROLOGY, PAHRUMP VALLEY, NEVADA-CALIFORNIA

Still unresolved is the ultimate disposition of the subsurface outflow from Pahrump Valley. This second investigation suggests that 

most of the outflow is southwestward through the No^ah and Resting Springs Ranges to discharge points in California, and that part 

may move northwestward to discharge at the springs in Ash Meadows. A direct determination of the magnitude and direction of the 

outflow, however, would require costly exploratory drilling. Even 

if the magnitude of the outflow could be determined, the amount 

that could be salvaged by pumping in Pahrump Vrlley probably 

would be small.

SELECTED REFERENCES

Blaney, H. F., and Harris, Karl, 1952, Report on water supply of the lower 

Colorado River Basin (provisional) : U.S. Bur. Reclamation Proj. Plan. 

Rept, 24 p.

Bowyer, Ben, Pampeyan, E. H., and Longwell, C. R., 1958, Geologic map of Clark 

County, Nevada : U.S. Geol. Survey Mineral Inv. Field Studies Map MF-138.

Davis, G. H.,,Green, J. H., Olmsted, F. H., and Brown, D. W., 1959, Groundwater conditions and storage capacity in the San Joaquin Valley, California : 

U.S. Geol. Survey Water-Supply Paper 1469, 287 p.

Eakin, T. E., and others, 1951, Estimated annual increment to ground water, in 

Contributions to the hydrology of eastern Nevada: Nevada State Engineer, 

Water Resources Bull. 12, p. 26-27.

Ferris, J. G., Knowles, D. B., Brown, R. H., and Stallman, R. w., 1962, Theory 

of aquifer tests: U.S. Geol. Survey Water-Supply Paper 1536-E, 174 p.

Gatewood, J. S., Robinson, T. W., Colby, B. R., Hem, J. D., and Halpenny, L. C., 

1950, Use of water by bottom-land vegetation in lower Safford Valley, Arizona : U.S. Geol. Survey Water-Supply Paper 1103, 210 p.

Hardman, George, and Mason, H. S., 1949, Irrigated lands of Tevada: Nevada 

Univ. Agr. Expt. Sta. Bull. 183, 57 p.

Hardman, George, and Miller, Meredith, 1934, The quality of the waters of southeastern Nevada, drainage basins and water resources: Nevada Univ. Agr. 

Expt. Sta. Bull. 136, p. 22-28.

Hazzard, J. C., 1937, Paleozoic section in the Nopah and Resting Springs Mountains, Inyo County, California: California Jour. Mines and Geology, v. 33, 

no. 4, p. 289-339.

Hewett, D. F., 1931, Geology and ore deposits of the Goodsprings quadrangle, 

Nevada : U.S. Geol. Survey Prof. Paper 162,172 p.

 1948, Iron deposits of the Kingston Range, San Bernardino County, California : California Div. Mines Bull. 129, p. 195-206.

 1956, Geology and mineral resources of Ivanpah quadrangle, California

and Nevada : U.S. Geol. Survey Prof. Paper 275,172 p.

Jennings, C. W., 1958, Geologic map of California, Death Valley sheet: California Dept. Nat. Resources, O. P. Jenkins, ed.

 1961, Geologic map of California, Kingman sheet: California Dept. Nat. 

Resources, O. P. Jenkins, ed.

Jennings, C. W.. Burnett, J. L.. and Troxel, B. W., 1962. Geologic map of California, Trona sheet: California Dept. Nat. Resources, O. r. Jenkins, eel.

Loeltz, O. J., 1960, Source of water issuing from springs in Ash Meadow Valley, 

Nye County, Nevada (abs.) : Geol. Soc. America Bull., v. 71, no. 12, p. 2.
SELECTED REFERENCES 47

Maxey, G. B., and Jameson, C. H., 1948, Geology and water resources of Las Vegas, 

Pahrump, and Indian Spring Valleys, Clark and Nye Counties, Nevada: 

Nevada Water Resources Bull. 5,121 p.; app. 1,128 p.; app. 2, 43 p.

Maxey, G. B., and Robinson, T. W., 1947, Ground water in Las Vegas, Pahrump, 

and Indian Spring Valleys, Nevada: Nevada Water Resources Bull. 6, 23 p.

Meinzer, O. E., 1923, Outline of ground-water hydrology, with definitions: U.S. 

Geol. Survey Water-Supply Paper 494, 71 p.

Mendenhall, W. C., 1909, Some desert watering places in southeastern California 

and southwestern Nevada : U.S. Geol. Survey Water-Supply Paper 224, 98 p.

Miller, M. R., Hardman, George, and Mason, H. G., 1953, Irrigation waters of 

Nevada : Nevada Univ. Agr. Expt. Sta. Bull. 187, 63 p.

Nolan, T. B., 1929, Notes on the stratigraphy and structure of the northwest 

portion of Spring Mountain, Nevada : Am. Jour. Sci., 5th ser., v. 17, p. 461-472.

Robinson, T. W., 1958, Phreatophytes: U.S. Geol. Survey Water-Supply Paper 

1423, 84 p.

Robinson, T. W., and others, 1947, Water levels and artesian pressure in wells 

in Las Vegas Valley and in other valleys in Nevada, 1913-45: Nevada Water 

Resources Bull. 3, 77 p.

Scofield, C. S., 1936, The salinity of irrigation waters: Smithsonian Inst. Ann. 

Rept. 1935, p. 275-287.

Shamberger, Hugh A., 1962, A proposed ten-year cooperative water resources program between the State of Nevada and the U.S. Geological Survey: Nevada 

Dept. Conserv. Nat. Resources, Water Resources Inf. Ser. Rept. 4, 18 p.

Theis, C. V., 1935, Relation between the lowering of the piezometric surface and 

the rate and duration of discharge of a well using ground-water storage: Am. 

Geophys. Union Trans., pt. 2, p. 519-524.

Thomasson, H. G., Jr., Olmsted, F. H., and LeRoux, E. F., 1960, Geology, water 

resources, and usable ground-water storage capacity of part of Solano County, 

California : U.S. Geol. Survey, Water-Supply Paper 1464, 693 p.

U.S. Salinity Laboratory Staff, 1954, Diagnosis and improvement of saline and 

alkali soils : U.S. Dept. Agriculture, Agriculture Handb. 60.

Walker, G. E., and Eakin, T. E., 1963, Geology and ground water of Amargosa 

Desert, Nevada-California : Nevada Dept. Conserv. Nat. Resources, GroundWater Resources Reconn. Ser. Rept. 14, 45 p.

Waring, G. A., 1921, Ground water in Pahrump, Mesquite, and Ivanpah Valleys, 

Nevada and California: U.S. Geol. Survey Water-Supply Paper 450-C, p. 

C51-C86.

Wenzel, L. K., 1942, Methods for determining permeability of water-bearing materials, with special reference to discharging-well methods : U.S. Geol. Survey 

Water-Supply Paper 887,192 p.

Winograd, I. J., 1962, Interbasin movement of ground water at the Nevada Test 

Site, Nevada : U.S. Geol. Survey Prof. Paper 450-C, p. C108-C111.

 1963, A summary of the ground-water hydrology of the areas between the 

Las Vegas Valley and the Amargosa Desert with special reference to the 

effects of possible new withdrawals of ground water: U.S. Geol. Survey 

TE1-840, 79 p.

Young, A. A., and Blaney, H. F., 1942, Use of water by native vegetation: California Dept. Public Works, Div. Water Resources Bull. 50.160 p.

U.S. GOVFRNMENT PRINTING OFFICE: 1967 O 240-366
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY

10' 5

PREPARED IN COOPERATION WITH THE

NEVADA DEPARTMENT OF CONSERVATION 

AND NATURAL RESOURCES

R 55 E. 45' R 56 E. 4O'

115°30'

36° 30'

T 17 S.

x

19 S

20 S.

T 21 S.

T 22 S.

36 "00'

T. 23 S.

T. 24 S.

T. 25 S

R 7 E 10'

Base from U.S. Geological Survey quadrangles

5 R 9 E. 116°00' 55' R. 10 E. 50' R 11 E

45' R. 12 E. 4O' R , I E 55' R. 57 E. 

INTERIOR GEOLOGICAL SURVEY, WASHINGTON. D C 1967 W6613I

R. 58 E.

35°45'

115°30' 

Geology of valley fill by G. T. Malmberg, 1963

1

WATER SUPPLY PAPER 1832 

PLATE 1

EXPLANATION

DEPOSITS OF THE VALLEY FILL 

FINE-GRAINED DEPOSITS COARSE-GRAINED DEPOSITS

Qyf

Younger surf icial deposits

Qya. younger alluvium: gravel, sand, silt, and 

clay derived principally from older lacustrine and alluvial-fan deposits; forms a 

veneer on older sedimentary deposits and 

lies largely above the zone of saturation

Qp, playa deposits: silt and clay; yield virtually no water to wells; depth to ground 

water beneath both playa surfaces more 

than 10 feet

Qd, dune sand: sand, silt, and clay; commonly 

stabilized by vegetation; lies above the zone 

of saturation

Qs, sinter: calcareous and siliceous; forms 

conspicuous mounds adjacent to fault in 

central part of valley

Younger fan deposits

Qyf, younger alluvial-fan deposits: gravel, 

sand, silt, and clay derived from older 

alluvial fans and consolidated rock in 

adjacent mountains; form alluvial fans and 

aprons along base of mountains; heterogeneity decreases with altitude; lie largely 

above zone of saturation but where saturated, 

stringers of highly permeable sand and 

gravel yield water readily to wells

Qc, channel deposits: gravel, sand, and silt in 

major stream channels; confined to arroyos 

on alluvial fans; highly permeable; where 

saturated they yield water readily to wells. 

Outcrop areas form principal areas of 

ground-water recharge

UNCONFORMITY

Medial lacustrine deposits

Silt and clay, highly calcareous; form a prominent bench along east side of valley. Bench

lies above the zone of saturation; lies conformably on older lacustrine deposits

Medial fanglomerate

Gravel, sand, silt, and clay, in part cemented; 

faulted and dissected; contains stringers 

and lenses of highly permeable sand and 

gravel. Where saturated may yield large 

quantities of water to wells. Grades laterally 

into.medial and older lacustrine deposits

Older lacustrine deposits 

Clay, silt, sand, and minor amounts of gravel; 

in part cemented by caliche; faulted and 

dissected. Saturated beneath the water 

table but generally does not yield large 

quantities of water to wells

Older fanglomerate

Boulders, gravel, sand, silt, and clay. Composed of igneous, metamorphic, and sedimentary rocks; faulted and dissected. Not 

known to occur at depth, but if saturated it 

probably would yield only limited amounts 

of water to wells. Interfingers with lower 

part of older lacustrine deposits

UNCONFORMITY

Tuff

Includes thin to massive beds of tuff; highly 

faulted and folded; where saturated would 

yield limited amounts of water to wells

UNCONFORMITY

CONSOLIDATED ROCKS

Sedimentary, metamorphic and igneous rocks

Highly indurated; intensely faulted and folded. Carbonate rocks 

absorb and transmit a large part of annual recharge from precipitation, and probably form a hydrologic system that in^part 

is separated from the ground-water system in the alluvial fill

Contact

Dashed where approximately located 

U__________

° Fault

Dashed where approximately located; dotted where concealed. 

D, downthrown side; U, upthrown side

Basin boundary

Qbaa 

Well and identification number

_ acdl

Flowing well and identification number

~« bdc 

Spring and identification number

Strike and dip of beds

cc

z

H

o

cc 

<

z 

tr 

LJ

o

Q

Z

K. 

U

I111

rOQ < 

Sr-

<o: 

u uj

UJrAPPROXIMATE MEAN 

DECLINATION. 1967

SCALE 1:125000 

4

8

10 MILES

10 KILOMETERS

CONTOUR INTERVALS 40, 80 AND 200 FEET

SUPPLEMENTAL CONTOUR INTERVALS 20 AND 40 FEET

DATUM IS MEAN SEA LEVEL

5000' -

4000' -

3000'-

r 12,000'

-11,000'

- 10,000'

r- 9000'

- 8000'

- 7000'

- 6000'

- 5000' 5000' -i

- 4000' 4000' -

- 3000' 3000' -

2000

VERTICAL EXAGGERATION X 4

2000' 2000'

Qp Qya

QTol

B'

r 5000'

Tp-Gr

Qyf

- 4000'

- 3000'

VERTICAL EXAGGERATION X 4

2000'

GEOLOGIC MAP AND SECTIONS OF PAHRUMP VALLEY, NEVADA- CALIFORNIA, SHOWING

THE LOCATION OF SELECTED WELLS AND SPRINGS
UNITED STATES DEPARTMENT OF THE INTERIOR 

116°15' GEOLOGICAL SURVEY

PREPARED IN COOPERATION WITH THE

NEVADA DEPARTMENT OF CONSERVATION 

AND NATURAL RESOURCES

R 57 E

115°30'

3j6°30'

T 18 S.

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T. 23 S.

T 24 S

35'45'

Base from U.S. Geological Survey quadrangles

» I-. E 35' R-!>7 E. R. 5(, E 

INTERIOR GEOLOGICAL. SURVEY, WASHINGTON. D. C. 1967 W66131

35°45'

-16*., MAP OF PAHRUMP VALLEY, NEVADA-CALIFORNIA, SHOWING WATER-LEVEL CONTOURS IN

THE VALLEY-FILL RESERVOIR IN FEBRUARY 1962

APPROXIMATE MEAN 

DECLINATION. 1967

SCALE 1:125000 

4 10 MILES

8 10 KILOMETERS

CONTOUR INTERVALS 40, 80, AND 200 FEET

SUPPLEMENTAL CONTOUR INTERVALS 20 AND 40 FEET

DATUM IS MEAN SEA LEVEL

WATER SUPPLY PAPER 1832 

PLATE 2

EXPLANATION

Area of artesian flow in February 1962

Approximate contact between valley fill 

and consolidated rocks

-2800 

Water-level contour, February 1962 

Dashed where approximate; contour interval 

20 feet; dotted lines are 10-foot contours. 

Datum, is mean sea level

Direction of ground-water flow

Basin boundary

Well in which water-level measurement was 

made; solid circle indicates flowing well

Gbca

Well in which water level declined below 

land surface during 1959-62

©~

Spring that flowed in 1959 but was dry 

in 1962

Spring
36°17'30

UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY

116°15' R 51 E

PREPARED IN COOPERATION WITH THE

NEVADA DEPARTMENT OF CONSERVATION 

AND NATURAL RESOURCES

WATER SUPPLY PAPER 1832 

PLATE 3

1 .- fy^^^^l

«r~-^, I ^

n .£"' / : X

./ yi

T 22 N

36° 00116° 15' nib R. , Base from U.S. Geological Survey quadrangles

APPROXIMATE MEAN 

DECLINATION, 1967

MAP OF PART OF PAHRUMP VALLEY, NEVADA-CALIFORNIA, SHOWING

THE DISTRIBUTION OF PHREATOPHYTES, 1959-61

SCALE 1:62500

V4

.5 0

5 MILES

CONTOUR INTERVALS 200 AND 400 FEET 

DATUM IS MEAN SEA LEVEL

5 KILOMETERS

35" 55'

116°55' R. 10 E.

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50' RUE INTER10R GEOLOGICAL SURVEY. WASHINGTON. D C 1967 W66131 115°45'
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY

36°30' 55' R. 54 E.

PREPARED IN COOPERATION WITH THE

NEVADA DEPARTMENT OF CONSERVATION 

AND NATURAL RESOURCES

50' R- 55 E 45'

WATER SUPPLY PAPER 1832 

PLATE 4

40'

35' R 57 E

VI

25 \

N

/I

\

\.

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&

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\ \

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115°30'

36° 30'

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V

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baa

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T. 17 S.

V: -*"_B' -V- : 

/;

EXPLANATION

n.

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,ddd

n*

M,

dba : O O

aba

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Consolidated rocks

Approximate contact between valley fill 

and consolidated rocks

15'

(-)5 ..-.

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^X^

/ cH^o^jlr

baa

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>. baa .

.' ' ---- V' 

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Line of equal change of water level,

February 1959 - February 1962 

Dashed where approximate; interval 5 feet; 

dotted line represents 1-foot interval

Boundary basin

Nonflowing well used as a control point

Flowing well used as a control point

0bda2

Well in which water level declines below 

land surface during 1959-62

^m-y-

^ x: x: x : x-,.

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Base from U.S. Geological Survey quadrangles

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R 8 E R. 9 E. H6°00' R. 10 E. 50' 45' R 12 E 40' n - F. ?- P. 57 E. R- 58 E. .._.,,.. 

INTERIOR GEOLOGICAU SURVEV. WASHINGTON. D C 1967 W6613I 113 3O

MAP OF PAHRUMP VALLEY, NEVADA-CALIFORNIA, SHOWING NET CHANGE IN WATER LEVEL 

IN THE VALLEY-FILL RESERVOIR BETWEEN FEBRUARY 1959 AND FEBRUARY 1962

DECLINATION, 1967

SCALE 1:125000 

4 10 MILES

i i i=r

8 10 KILOMETERS

CONTOUR INTERVALS 40, 80 AND 200 FEET

SUPPLEMENTAL CONTOUR INTERVALS 20 AND 40 FEET

DATUM IS MEAN SEA LEVEL
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY

PREPARED IN COOPERATION WITH THE

NEVADA DEPARTMENT OF CONSERVATION 

AND NATURAL RESOURCES

40'

35' R 57 E.

115°30'

36°30'

T 18 S.

; T 19 S

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WATER SUPPLY PAPER 1832 

PLATE 5

T. 17 S.

T. 20 S.

T. 21 S.

4 T. 22 S.

36° 00'

T. 23 S.

35°45

Base from U.S. Geological Survey quadrangles

r 13 E ?5' R 57 E. 

INTERIOR GEOLOGICAL SURVEY. WASHINGTON. D C. 1967 W6613

T 25 6

35°45'

MAP SHOWING VARIATIONS IN PRINCIPAL CHEMICAL CONSTITUENTS OF GROUND WATER

IN PAHRUMP VALLEY, NEVADA-CALIFORNIA

APPROXIMATE MEAN 

DECLINATION. 1967

-I T=

SCALE 1:125000 

4 10 MILES

10 KILOMETERS

3

CONTOUR INTERVALS 40, 80, AND 200 FEET

SUPPLEMENTAL CONTOUR INTERVALS 20 AND 40 FEET

DATUM IS MEAN SEA LEVEL

EXPLANATION

K+NaCI

10 5 0 5 10

11 11 i i 11 i i i 11 i 11 11 i i

Equivalents per million

Consolidated rocks

Approximate contact between 

valley fill and consolidated rocks

Boundary basin

dbd

o

Well

bed

Flowing well

dab

 ^

Spring