U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 036–01

April 2001

Introduction

The Amargosa River drainage basin is about 100 miles northwest 

of Las Vegas, Nev., and includes part of the Nevada Test Site (NTS). 

During February 23–24, 1998, a regional storm produced 1.10–2.81 

inches of measured precipitation, which resulted in minor flooding 

throughout the Amargosa River drainage basin. Streamflow from this 

storm was largely derived from four tributaries: Topopah, Fortymile, 

and Beatty Washes, which originate on NTS, and Carson Slough, 

which drains the Ash Meadows area downstream from NTS (Fig. 1). 

Streamflow from these tributaries caused the Amargosa River to flow 

continuously from its headwaters on Pahute Mesa to its terminus in 

Death Valley (Fig. 1).

U.S. Geological Survey (USGS) personnel estimated peak 

streamflows at more than 30 locations and compiled precipitation 

measurements within the Amargosa River drainage basin to 

characterize the February 23–24, 1998, flooding (Tables 1 and 2). 

The data collected are compared with similar data from the March 

10–11, 1995, flooding of the Amargosa River. Cumulative streamflow 

volumes for the 1995 and 1998 storm runoffs cannot be compared 

because most of the streamflow gaging stations operated in 1995 were 

discontinued prior to the 1998 flood.

The USGS, in cooperation with the U.S. Department of Energy, 

monitors streamflow in southern Nevada and eastern California 

through a network of streamflow gaging stations and streamflow 

measurements at miscellaneous sites. Data provided by this network 

are being used to help with the characterization of Yucca Mountain, 

near NTS, as a potential repository for long-term storage of the 

Nation’s high-level nuclear waste. Major questions arising from the 

Yucca Mountain site-characterization studies are whether, under the 

present climatic regime, Fortymile Wash is capable of flowing to the 

Amargosa River, and whether Amargosa River is similarly capable 

of flowing from its source to Death Valley.

The Amargosa River Basin includes 5,500 mi2 (Grasso, 1996, 

table 1) of rugged arid terrain in southwestern Nevada and southeastern California (Fig. 1). Basin relief is approximately 8,000 feet, 

ranging from about 7,700 feet above sea level at Pahute Mesa, Nev., 

to about 300 feet below sea level at Badwater Basin in Death Valley, 

Calif. The river basin is sparsely populated and includes small rural 

communities, mining operations, agricultural areas, Ash Meadows 

National Wildlife Refuge, Death Valley National Park, and government 

research facilities at NTS. 

The Amargosa River is atypical of most North American rivers 

because it seldom flows; runoff is infrequent because much of the 

basin receives less than 6 in/yr of precipitation (Hardman, 1965). 

The river is normally dry except for several short reaches that flow 

seasonally and are fed by springs. The major tributaries to the northern 

reach of the Amargosa River are Thirsty Canyon wash and Beatty 

Wash, which drain the northwestern part of NTS (Fig. 1). Major 

tributaries to the central reach of the Amargosa River are Fortymile 

Wash, Topopah Wash, and Carson Slough (Fig. 1). Fortymile Wash 

drains the southern part of Pahute Mesa, the western part of Jackass 

Flats, and the eastern slopes of Yucca Mountain. Topopah Wash drains 

the eastern part of Jackass Flats. Carson Slough, near Death Valley 

Junction, is a network of shallow incised channels that drain the Ash 

Meadows area. 

Downstream from Alkali Flat, in the southern reach, the Amargosa 

River channel generally is well defined from Eagle Mountain to 

Dumont Sand Dunes, Calif. Upstream from Dumont Sand Dunes, 

small thermal springs near Shoshone and Tecopa, Calif., contribute 

flow to the Amargosa River. Springs also add to river flow in the 

canyon reach between Tecopa and Dumont Sand Dunes. Downstream 

from Dumont Sand Dunes, the Amargosa River flows through 

southern Death Valley to its terminus at the Badwater Basin salt pan.

February 1998 Storm and Streamflow

Precipitation monitoring sites operated by the National Weather 

Service (NWS), U.S. Fish and Wildlife Service, and National Oceanic 

Atmospheric Administration (NOAA) recorded 29 to 54 percent of 

total February precipitation from a regional storm system within 48 

hours beginning the morning of February 23, 1998 (Table 1). USGS 

personnel at NTS reported streamflow in small washes, such as Split 

and Pagany (which partly drain the eastern slope of Yucca Mountain), 

during the morning of February 23 (Fig. 1). By mid-afternoon, Yucca, 

Topopah, and Fortymile Washes also were reported flowing. Fortymile 

Wash was flowing over roads on NTS near Yucca Mountain (Daniel 

Soeder, U.S. Geological Survey, written commun., 1998). Peak 

streamflow estimates for Fortymile and Topopah Washes (Table 2) and 

downstream field observations indicate those streams flowed from 

NTS and joined the Amargosa River. On the basis of field observations 

and data collected from continuous surface-water monitoring sites, 

streamflow durations generally ranged from 12 to 36 hours and varied 

according to tributary subbasin sizes. Channel erosion by streamflow 

was considered minimal in the large tributaries of Fortymile, Topopah, 

and Beatty Washes, but was more severe in some smaller tributaries 

such as Pagany, Yucca, Split, and Dune Washes. Roads within these 

small drainages were nearly impassable because of erosion.

Carson Slough, State Line Road near Death Valley Junction, California, 

looking north, February 25, 1998. 

Flooding in the Amargosa River Drainage Basin, February 23–24, 1998, Southern 

Nevada and Eastern California, including the Nevada Test Site

Walter E. Nylund, U.S. Geological Survey
0 20 MILES

0 20 KILOMETERS

1

A

EXPLANATION

Streamflow measurement site

 and number (table 2)

Direction of stream flow

Amargosa River drainage basin

 boundary 

Precipitation measurement site

 and identifier (table 1)

Nevada Test Site boundary

Jackass Flats kass Flats

Yucca

Crater

Flat Mtn

Pah

Canyon

Solitario Solitario

Canyon

Delirium Canyon

Dune

Wash

Wash

Wash

Wash

Tonopah

Wash

CraterCrater

Flat

Beatty 

Yucca

Wash Pagany Wash

Drillhole Drillhole Wash

Split Wash

B

6

7,8

11 13

15

16 17

19

18

20

25

D

4

9

10

14

12

Area of Area of

map

NEVADA

Las

Vegas

95

95

374

373

160

372

178

178

127

190

Amargosa Amargosa

Valley

Ash MeadowsAsh Meadows

Beatty

Wash

FortymileFortymile

Wash

Wash

Topopah

Mercury

Mercury

ercury

Valley

alley Oasis Valley

East Cat East Cat

Canyon

Pahrump

Rock Valley Rock Valley

Specter RangeSpecter Range

Dumont

Sand

Dunes

Badwater

 Basin Basin

Alkali

Flat

Eagle

Mtn Black Mountains

Bla k Mountains

Carson SloughCarson Slough

Chicago Valley Chicago Valley

Death Valley

Junction unction

Funeral MountainsFuneral Mountains

Death

Valley

Amargosa Desert Amargosa Desert

Furnace

Creek

Shoshone Shoshone

Silurian ValleySilurian Valley

Sperry

Hills

Tecopa

32

31

24

30

K

J

F

B

A

1 6

2 7,8

14 11 12

13

1516 17

19

18

20

25

29

D

22

H

26

5 21

4

3

9

10

C

27,28

E

G

L

I

23

Stockade Stockade

Wash

Beatty 

AmargosaAmargosa

River

NEVADANEVADA

CALIFORNIACALIFORNIA

River

AmargosaAma gosa

River

AmargosaAma gosa

Ash Mead Ash Meadows

National Wildli National Wildlife

Refuge

Pahute Mesa ahute Mesa

Bare Mtn Bare Mtn

Cane

Springs

Nevada

Test Site est Site

B elle

Vista Road

Fortymile

Thirst y Canyon wash

State

Line Road Line Road

Jackass Flats

Yucca

Crater

Flat Mtn

Pah Canyon

Solitario

Canyon

Delirium Canyon

Dune

Wash

Wash

Wash

Wash

Tonopah

Wash

Crater

Flat

Beatty 

Yucca

Wash Pagany Wash

Drillhole Wash

Split Wash

B

6

7,8

11 13

15

16 17

19

18

20

25

D

4

9

10

14

12

37°00'

117°00' 116°00'

36°30'

36°00'

Area of

map

NEVADA

Las

Vegas

Base from U. S. Geological Survey digital data, 1:100,000, 1978-85:

Universal Transverse Mercator Projection, Zone 11. Shaded-relief

base from 1:24,000-scale Digital Elevation Model; sun illumination

from northwest at 30 degrees above horizon

95

95

374

373

160

372

178

178

127

127

190

Amargosa

Valley

Ash Meadows

Beatty

Wash

Fortymile

Wash

Wash

Topopah

Mercury

Mercury

Valley Oasis Valley

East Cat

Canyon

Pahrump

Rock Valley

Specter Range

Dumont

Sand

Dunes

Badwater

 Basin

Alkali

Flat

Eagle

Mtn Black Mountains

Carson Slough

Chicago Valley

Death Valley

Junction

Funeral Mountains

Death

Valley

Amargosa Desert

Furnace

Creek

Shoshone

Silurian Valley

Sperry

Hills

Tecopa

32

31

24

30

K

J

F

B

A

1 6

2 7,8

14 11 12

13

1516 17

19

18

20

25

29

D

22

H

26

5 21

4

3

9

10

C

27,28

E

G

L

I

23

Stockade Wash

Beatty 

Amargosa

River

NEVADA

CALIFORNIA

River

Amargosa

River

Amargosa

Ash Meadows

National Wildlife

Refuge

Pahute Mesa

Bare Mtn

Cane

Springs

Nevada

Test Site

B elle Vista Road

Fortymile

State

Line Road

Thirst y Canyon wash

Figure 1. Geographic setting and flow paths of the Amargosa River drainage basin during the February 23–24, 1998, flood.

Field observations off NTS indicated that Amargosa River flow 

lasted for several days near Eagle Mountain and southward near 

Dumont Sand Dunes (Fig. 1). Although not quantifiable because of 

multiple, poorly confined channels, field observations indicated that 

runoff from the Ash Meadows area contributed substantial streamflow 

(through Carson Slough) to the central reach of the Amargosa River. 

Prolonged runoff from Ash Meadows probably was amplified because 

precipitation prior to late February recharged the soil mantle. 

Thereby, infiltration losses from the late-February storm were 

reduced. Flows over roads were observed where U.S. Highway 95 

crosses Fortymile Wash, in the Amargosa Farms, State Line Road 

area, and at several river crossings on California State Highway 127. 

The combined result of widespread and prolonged storm runoff 

throughout the Amargosa River Basin was persistent streamflow that 

contributed to the formation of a small lake on the normally dry and 

barren Badwater Basin salt pan at the river terminus in Death Valley.
1 Ernie Cobb, National Weather Service, written commun., 1998.

2 Raymond D. Dennis, National Oceanic Atmospheric Administration, written commun., 1998.

3 David St. George, U.S. Fish and Wildlife Service, oral commun., 1998.

4 Dorothy Miller, Desert Research Institute, oral commun., 1998.

Site 

identifier

(fig. 1)

Station name 

Precipitation (inches)

in March 1995 Percent of 

total for 

March 10–11, 

1995

Precipitation (inches)

in February 1998

Percent of

total for

February 

23–24, 

1998 March 10–11 Marchtotal

February 

23–24

February

total

A

B

C

D

E

F

G

H

I

J

K

L

Beatty, Nev.1,4

Fortymile Canyon, NTS2

Cane Springs, NTS2

Jackass Flats, NTS2

Rock Valley, NTS2

Mercury, NTS2

Desert Rock, NTS2

Amargosa Farms, Nev.1,4

Ash Meadows, Nev.3

Pahrump, Nev.1

Shoshone, Calif.1,4

Death Valley, Calif.1,4

2.36

3.98

1.38

1.79

1.53

.68

.81

.52

--

--

0

.24

3.50

5.40

2.63

2.48

2.61

1.60

2.39

.94

--

--

.45

.31

67

74

52

72

59

42

34

55

--

--

0

77

1.68

2.10

e2.20

e2.10

2.81

2.17

2.52

1.76

1.40

1.42

1.10

1.10

4.47

5.15

e6.04

e6.26

5.97

4.10

4.64

3.69

3.16

3.32

3.84

2.31

38

41

36

34

47

53

54

48

44

43

29

48

Comparison of 1995 and 1998 Floods

The floods of March 1995 and February 1998 have similarities 

and differences. Similarities include larger-than-normal snowpacks 

during both years on Pahute Mesa and surrounding mountains (Beck 

and Glancy, 1995; Raymond Dennis, National Oceanic and 

Atmospheric Administration, oral commun., 1998). Both floods were 

the result of regional storms that contributed a substantial quantity of 

precipitation to the river basin over a relatively short time. Also, both 

floods may have occurred during periods of the atmospheric and 

oceanic phenomenon known as “El Nino” (Desert Research Institute, 

1998; National Oceanic and Atmospheric Administration, 1998). 

During both floods, surface water from NTS flowed to the Amargosa 

River mainly by way of Fortymile Wash, and road overflows were 

observed at similar locations. Neither lower Crater Flat nor Solitario 

Canyon (Fig. 1) contributed streamflow to the Amargosa River during 

the floods of March 1995 and February 1998.

Differences between the two floods, however, also were apparent. 

For example, the flood of March 1995 was the result of precipitation, 

of relatively short duration, that occurred mainly in the higher 

altitudes near Yucca Mountain. Snowpack melting, which resulted 

from precipitation at these higher altitudes, probably contributed 

significantly to the peak streamflows in Beatty and Fortymile Washes 

and their associated tributaries (David A. Beck, U.S. Geological 

Survey, oral commun., 1998). In Fortymile Wash, a peak streamflow 

of about 3,000 ft3/s (Table 2) severely scoured and eroded the channel 

and caused extensive road damage on NTS and to U.S. Highway 95 

(Beck and Glancy, 1995). 

In contrast, the February 1998 flooding was attributed to 

persistent, widespread precipitation, over several days, which 

eventually caused streamflow in most major tributaries to Fortymile 

Wash and the Amargosa River. Although snowpack accumulation was 

observed at higher altitudes within the region during February 1998, 

snowpack melting was not a major factor during the 1998 flood 

(David A. Beck, U.S. Geological Survey, oral commun., 1998). Peak 

streamflows generally were lower in the northern (higher altitude) 

reach of the Amargosa River drainage basin, but higher in the central 

and southern (lower altitude) reaches of the drainage basin.

Major streamflow from NTS during the March 1995 flood was 

observed only in Beatty and Fortymile Washes. During the February 

1998 flood, Topopah Wash also flowed off NTS (Table 2). Based on 

peak-flow estimates and observations of channel scour and fill, 

streamflows were greater in Beatty and Fortymile Washes during 

March 1995 than February 1998; however, streamflows were greater 

in several small washes including Dune, Yucca, Cane Springs, and 

Split (Table 2) during February 1998 than March 1995. Durations of 

streamflows also differed between the two floods; the February 1998 

streamflows in washes on NTS lasted 12 to 36 hours, whereas the 

March 1995 streamflows lasted only 10 to 12 hours. 

Runoff from the Ash Meadows area played an important role in 

sustaining streamflow in the central and southern reaches of the 

Amargosa River in February 1998. Near-peak streamflow discharge 

was observed at Carson Slough draining into Alkali Flat 

approximately 24 hours after flow completely ceased in Fortymile 

Wash and in the Amargosa River upstream from Nevada State 

Highway 373 (David A. Beck, U.S. Geological Survey, oral commun., 

1998). Overall, the February 1998 flood sustained streamflow over a 

longer duration throughout the entire Amargosa River drainage basin 

than did the March 1995 flood.

Summary

The 1995 streamflow was dominated by high-magnitude runoff of 

relatively short duration in Beatty and Fortymile Washes, probably 

enhanced by localized precipitation on snowpack in the upper 

altitudes of NTS. In 1998, sustained regional precipitation caused 

lower magnitude streamflows of longer duration in Fortymile Wash, 

Amargosa River, and their major tributaries. In both floods, much or 

all of Fortymile Wash and the Amargosa River flowed simultaneously. 

In March 1995, water in Fortymile and Beatty Washes flowed off 

NTS; in February 1998, water in Topopah Wash also flowed off NTS. 

In 1995 and 1998, the Amargosa River flowed from its headwaters to 

its terminus in Death Valley. Both the 1995 and 1998 floods indicate, 

therefore, that the Amargosa River, with contributing streamflow from 

one or more among Beatty, Fortymile, and Topopah Washes, has the 

potential to transport dissolved and particulate material well beyond 

the boundary of NTS and the Yucca Mountain area during periods of 

moderate to severe streamflow.

Table 1. Precipitation for March 1995 and February 1998 floods, Amargosa River Basin, Nevada–California

[Abbreviations and symbol: e, estimated; Nev., Nevada; NTS, Nevada Test Site; --, not available]

Note: Trace amounts of precipitation and snowfall are not figured into totals. 
Selected References

Beck, D.A., and Glancy, P.A., 1995, Overview of runoff of March 11, 1995, in 

Fortymile Wash and Amargosa River, southern Nevada: U.S. Geological 

Survey Fact Sheet FS-210-95, 4 p.

Desert Research Institute, 1998, Western Regional Climate Center theme page: 

accessed August 3, 1998, on the World Wide Web at URL 

<http://www.wrcc.dri.edu/cgi-bin/elnino1.pl>.

Grasso, D.N., 1996, Hydrology of modern and late Holocene lakes, Death 

Valley, California: U.S. Geological Survey Water-Resources Investigations 

Report 95-4237, 54 p.

Hardman, George, 1965, Nevada precipitation map: University of Nevada 

Agricultural Experimentation Bulletin 183, 57 p.

Laczniak, R.J., Cole, J.C., Sawyer, D.A., and Trudeau, D.A., 1996, Summary of 

hydrogeologic controls on ground-water flow at the Nevada Test Site, Nye 

County, Nevada: U.S. Geological Survey Water-Resources Investigations 

Report 96-4109, 59 p.

National Oceanic Atmospheric Administration, 1998, El Nino theme page: 

accessed August 3, 1998, on the World Wide Web at URL 

<http://www.pmel.noaa.gov/toga-taol/el-nino-story.html>.

National Weather Service, 1998, Las Vegas home page: accessed August 3, 

1998, on the World Wide Web at URL <http://nimbo.wrh.noaa.gov/Lasvegas>

[last updated June 9, 1998].

U.S. Geological Survey, 1993–97, Water resources data, Nevada, water years 

1992–96: U.S. Geological Survey Water-Data Reports, NV-92-1 to NV-96-1 

(published annually).

—Daron J. Tanko and Patrick A. Glancy

For further information contact:

 Public Information Assistant U.S. Geological Survey

 GS-W-NVpublic-info@usgs.gov 333 W. Nye Lane

 URL: http://nevada.usgs.gov Carson City, NV 89706

 telephone: (775) 887–7649

1

 Road repair and grading destroyed all high-water marks prior to peak-streamflow estimates, but it is believed by reconnaissance teams that runoff may have been 

substantial to cause such extensive road damage. 2

 Includes peak streamflow estimates in bypass channel of 300 ft3/s (March 1995) and 7.0 ft3/s (February 1998). 3

 Total of peak streamflow estimates in three principal channels.

Site

no. 

(fig. 1)

Gaging station Drainage

area

(mi2 )

Peak discharge (ft3/s) Years of

streamflow

Number Name record

March

1995

February

1998

Nevada Test Site

6

7

8

9

10

102512495

102512496

102512497

102512499

10251250

Pah Canyon Wash above Fortymile Wash Confluence

Unnamed Tributary to Fortymile Wash North of Delirium Canyon 

Delirium Canyon Wash above Fortymile Wash Confluence

Unnamed Tributary to Fortymile Wash South of Delirium Canyon

Fortymile Wash at Narrows

6.28

1.14

2.37

.81

258 

nd

nd

nd

nd

3,000

90

180

120

70

200

1998

1998

1998

1998

1983–97, 1998

11

12

13

14

15

10251252

102512531

102512533

102512535

1025125356

Yucca Wash near Mouth

Pagany Wash near the Prow

Pagany Wash #1 near Well UZ-4

Drillhole Wash above UZ-1

Wren Wash at Yucca Mountain

17.0

.47

.82

.68

.23

0

60

60

30

30

220

20

17

< 4.0

< 5.0

1982–95, 1998

1994–95, 1998

1993–95, 1998

1994–95, 1998

1994–95, 1998

16

17

18

19

20

102512537

1025125372

10251254

10251255

10251256

Split Wash below Quac Canyon Wash

Split Wash at Antler Ridge

Drillhole Wash at Mouth

Fortymile Wash near Well J-13

Dune Wash near Busted Butte

.33

2.35

16.3

304

6.77

11

nd

< 0.1

3,000

< 3.0

13

< 2.0

25

200

1nd

1993–95, 1998

1993–95, 1998

1983–95, 1998

1983–97, 1998

1982–95, 1998

25

27

28

10251260

10251265

102512654

Topopah Wash at Little Skull Mountain

Cane Springs Wash near Cane Springs

Cane Springs Tributary below Skull Mountain

104

8.36

2.29

< 1.5

< 5.0

15

30

110

< 5.0

1984–95, 1998

1984–95, 1998

1992–95, 1998

Sites off the Nevada Test Site

1

2

3

4

5

10251215

10251217

10251225

10251233

10251235

Beatty Wash near Beatty, Nev.

Amargosa River at Beatty, Nev.

Amargosa River at Big Dune near Amargosa Valley, Nev.

Solitario Canyon at Mouth near Yucca Mountain, Nev.

Crater Flat Wash above Highway 95 near Amargosa Valley, Nev.

94.6

458

842

4.14

157

900

1,000

nd

0

0

30

90

20

0

0

1989–95, 1998

1993–95, 1996– 98

1998

1995, 1998

1995, 1998

21

22

23

24

26

10251258

102512585

10251259

102512597

10251261

Fortymile Wash near Amargosa Valley, Nev.

Fortymile Wash at Amargosa Farms, Nev.

Amargosa River at Highway 127 near Calif.–Nev. State Line

Amargosa River at Death Valley Junction, Calif.

Topopah Wash at Highway 95 near Amargosa Valley, Nev.

316

 325

1,542

 1,567

150

2

1,200 

nd

27

< 5.0

nd

2340

3

90

30

60

20

1983–98

1998

1993–95, 1998

1995, 1998

1998

29

30

31

32

10251270

10251280

10251300

10251375

Amargosa River Tributary near Mercury, Nev.

Amargosa River near Eagle Mountain below Death Valley Junction, Calif.

Amargosa River at Tecopa, Calif.

Amargosa River at Dumont Sand Dunes near Death Valley, Calif.

110

2,632 

3,090 

 3,284

0

100

170

nd

25

190

250

200

1963–81,

1984–95, 1998

1990–95, 1998

1961–83, 

1991–95, 1998

1998

April 2001 USGS Fact Sheet 036–01

Table 2. Peak-flow estimates for selected sites in tributaries and reaches of the Amargosa River Basin, Nevada–California

[Site number is assigned in downstream order from uppermost location. Abbreviations and symbols: Nev., Nevada; Calif., California; nd, not determined; ft3/s, cubic 

feet per second; mi2, square miles; <, less than]