Precipitation and Runoff Simulations of the Carson 

Range and Pine Nut Mountains, and Updated Estimates 

of Ground-Water Inflow and the Ground-Water Budget 

for Basin-Fill Aquifers of Carson Valley, Douglas County, 

Nevada, and Alpine County, California

Prepared in cooperation with Douglas County, Nevada

U.S. Department of the Interior 

U.S. Geological Survey

Scientific Investigations Report 2007–5205
Cover: Looking west from Ambrosetti Pond towards the Carson Range. Photograph 

taken by Laurie Bonner, U.S. Geological Survey, October 27, 2004. 
Precipitation and Runoff Simulations of the 

Carson Range and Pine Nut Mountains, and 

Updated Estimates of Ground-Water Inflow 

and the Ground-Water Budget for Basin-Fill 

Aquifers of Carson Valley, Douglas County, 

Nevada, and Alpine County, California

By Anne E. Jeton and Douglas K. Maurer

Prepared in cooperation with Douglas County, Nevada

Scientific Investigations Report 2007–5205

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

For product and ordering information:

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U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Jeton, A.E., and Maurer, D.K., 2007, Precipitation and runoff simulations of the Carson Range and Pine Nut 

Mountains, and updated estimates of ground-water inflow and the ground-water budget for basin-fill aquifers of 

Carson Valley, Douglas County, Nevada, and Alpine County, California: U.S. Geological Survey Scientific Investigations 

Report 2007–5205, 56 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Purpose and Scope ..............................................................................................................................4

Geographic Setting...............................................................................................................................4

Geologic Setting....................................................................................................................................6

Hydrologic Setting ................................................................................................................................8

Components of the Ground-Water Budget for Basin-Fill Sediments of Carson Valley....8

Description of Watershed Models............................................................................................................11

Precipitation-Runoff Modeling System...........................................................................................13

Model Development ...........................................................................................................................15

Basin Characterization and Delineation of Hydrologic Response Units ..........................15

Runoff and Climate Data...........................................................................................................16

Model Sensitivity........................................................................................................................21

Model Calibration................................................................................................................................22

Error Analysis ......................................................................................................................................22

Carson Range Perennial Watersheds ....................................................................................23

Daggett Creek Watershed...............................................................................................23

Fredericksburg Canyon Watershed...............................................................................27

Pine Nut Mountains Perennial Watersheds..........................................................................27

Pine Nut Creek Watershed..............................................................................................27

Buckeye Creek Watershed .............................................................................................32

Model and Data Limitations ..............................................................................................................32

Results of Watershed Modeling and Comparison with Previous Estimates......................................33

Perennial Watersheds .......................................................................................................................33

Ephemeral Watersheds .....................................................................................................................44

Ground-Water Inflow Simulated from Watershed Models and Variation from Dry to Wet 

Conditions...............................................................................................................................46

Uncertainty in Estimates of Simulated Ground-Water Inflow.....................................................47

Ground-Water Inflow Simulated from Watershed Models Compared with Previous Estimates ...48

Updated Ground-Water Budget for Basin-fill Aquifers of Carson Valley...........................................50

Summary and Conclusions.........................................................................................................................51

Acknowledgments.......................................................................................................................................53

References Cited..........................................................................................................................................53
iv

Figures

Figure 1. Map showing location of the Carson River Basin and the Carson Valley

hydrographic areas, Nevada and California ............................................. 3

Figure 2. Map showing location of the Carson Valley study area and depth to water

table, Nevada and California, June 2005 ................................................ 5

Figure 3. Map showing surficial geologic units and faults in Carson Valley, perennial

and ephemeral watersheds, and the locations of precipitation and runoff

gaging or measurement stations used in watershed model development,

Nevada and California ..................................................................... 7

Figure 4. Graphs showing annual precipitation at Minden, Nevada, and Heavenly

Valley, California, and Palmer Drought Severity Index for western Nevada ......... 9

Figure 5. Conceptual diagram showing components of ground-water recharge to and

discharge from basin-fill aquifers of Carson Valley, Nevada and California ......... 10

Figure 6. Schematic diagram of processes simulated by the Precipitation-Runoff

Modeling System ........................................................................... 14

Figure 7. Maps showing HRU delineation and distribution of slope, aspect, land cover,

and land-surface altitude zones in the Daggett Creek watershed, Carson

Valley, Nevada .............................................................................. 17

Figure 8. Graphs showing simulated and measured daily mean runoff for Daggett

Creek and Fredericksburg Canyon watersheds, Carson Valley, Nevada and

California, water years 1990–2002 ......................................................... 24

Figure 9. Graph showing simulated and measured annual mean runoff and

ground-water inflow for Daggett Creek, water years 1990–2002,

Fredericksburg Canyon, water years 1990–2001, and Pine Nut Creek and

Buckeye Creek watersheds, water years 1981–97, Carson Valley, Nevada and

California .................................................................................... 25

Figure 10. Graphs showing simulated and measured daily mean runoff for Pine Nut

Creek and Buckeye Creek watersheds, Carson Valley, Nevada, water years

1981–97 ....................................................................................... 28

Figure 11. Graphs showing simulated and reconstructed daily mean runoff for 10

ungaged perennial watersheds in Carson Valley, Nevada and California,

water years 1990–2002 ..................................................................... 34

Figure 12. Graphs showing simulated and reconstructed annual mean runoff and

ground-water inflow for 10 ungaged perennial watersheds in Carson Valley,

Nevada and California, water years 1990–2002.......................................... 39
v

Tables

Table 1. Major bedrock type, runoff as a percentage of precipitation, index model, and

precipitation stations used for model development of perennial gaged and

ungaged watersheds, Nevada and California .......................................... 12

Table 2. Precipitation and streamflow-gaging stations, period of record, and altitude,

Carson Valley, Nevada and California ................................................... 21

Table 3. Calibration statistics for PRMS watershed models of gaged watersheds of

the Carson Range and Pine Nut Mountains, Carson Valley, Nevada and

California .................................................................................... 23

Table 4. Summary of model results for 14 perennial watersheds in Carson Valley,

water years 1990–2002, and comparison with estimates from Maurer and

Berger (2007) ................................................................................. 30

Table 5. Summary of model results for selected ephemeral watersheds in Carson

Valley, Nevada and California, water years 1990–2002 ................................. 45

Table 6. Mean annual ground-water inflow to basin-fill deposits of Carson Valley

simulated with watershed models, water years 1990–2002, and compared

with mean annual inflow simulated during dry conditions, water years

1990–92, and wet conditions, water years 1995–97, Nevada and California ......... 46

Table 7. Potential range in estimates of runoff and ground-water inflow to basin-fill

aquifers of Carson Valley from ephemeral watersheds of the Carson Range,

Nevada and California ..................................................................... 48

Table 8. Estimates of mean annual ground-water inflow to basin-fill aquifers of Carson

Valley using water-yield and chloride-balance methods by Maurer and

Berger (2007) and simulated with watershed models of this study, Nevada

and California .............................................................................. 49

Table 9. Updated ground-water budget for basin-fill aquifers of Carson Valley using

previous estimates by Maurer and Berger (2007), and estimates simulated

from watershed models in this study, water years 1990–2005 ........................ 50
vi

Conversion Factors, Datums, and Abbreviations and 

Acronyms

Conversion Factors

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.4047 hectare (ha)

acre 0.4047 square hectometer (hm2) 

acre 0.004047 square kilometer (km2)

square foot (ft2) 929.0 square centimeter (cm2)

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

cubic foot (ft3) 28.32 cubic decimeter (dm3) 

cubic foot (ft3) 0.02832 cubic meter (m3) 

acre-foot (acre-ft) 1,233 cubic meter (m3)

acre-foot (acre-ft) 0.001233 cubic hectometer (hm3) 

Flow rate

acre-foot per day (acre-ft/d) 0.01427 cubic meter per second (m3/s)

acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m3/yr)

acre-foot per year (acre-ft/yr) 0.001233 cubic hectometer per year (hm3/yr)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic foot per second per square mile

 [(ft3/s)/mi2]

 0.01093 cubic meter per second per square 

 kilometer [(m3/s)/km2]

cubic foot per day (ft3/d) 0.02832 cubic meter per day (m3/d)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

 °F=(1.8×°C)+32.

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

 °C=(°F-32)/1.8.
vii

Datums

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Abbreviations and Acronyms

ET Evapotranspiration

GIS Geographic Information System

HRU Hydrologic Response Unit

MMS Modular Modeling System

m.y. Million years

PDSI Palmer Drought Severity Index

PRMS Precipitation-Runoff Modeling System

RMSE Root mean square error

USGS U.S. Geological Survey

Conversion Factors, Datums, and Abbreviations and 

Acronyms—Continued
viii

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Abstract

Recent estimates of ground-water inflow to the basin-fill 

aquifers of Carson Valley, Nevada, and California, from the 

adjacent Carson Range and Pine Nut Mountains ranged from 

22,000 to 40,000 acre-feet per year using water-yield and 

chloride-balance methods. In this study, watershed models 

were developed for watersheds with perennial streams and for 

watersheds with ephemeral streams in the Carson Range and 

Pine Nut Mountains to provide an independent estimate of 

ground-water inflow. This report documents the development 

and calibration of the watershed models, presents model 

results, compares the results with recent estimates of groundwater inflow to the basin-fill aquifers of Carson Valley, and 

presents updated estimates of the ground-water budget for 

basin-fill aquifers of Carson Valley.

The model used for the study was the PrecipitationRunoff Modeling System, a physically based, distributedparameter model designed to simulate precipitation and 

snowmelt runoff as well as snowpack accumulation and 

snowmelt processes. Geographic Information System software 

was used to manage spatial data, characterize model drainages, 

and to develop Hydrologic Response Units. Models were 

developed for

•	 Two watersheds with gaged perennial streams in 

the Carson Range and two watersheds with gaged 

perennial streams in the Pine Nut Mountains using 

measured daily mean runoff,

•	 Ten watersheds with ungaged perennial streams using 

estimated daily mean runoff,

•	 Ten watershed with ungaged ephemeral streams in the 

Carson Range, and

•	 A large area of ephemeral runoff near the Pine Nut 

Mountains.

Models developed for the gaged watersheds were used as 

index models to guide the calibration of models for ungaged 

watersheds.

Model calibration was constrained by daily mean runoff 

for 4 gaged watersheds and for 10 ungaged watersheds in 

the Carson Range estimated in a previous study. The models 

were further constrained by annual precipitation volumes 

estimated in a previous study to provide estimates of groundwater inflow using similar water input. The calibration 

periods were water years 1990–2002 for watersheds in the 

Carson Range, and water years 1981–97 for watersheds in 

the Pine Nut Mountains. Daily mean values for water years 

1990–2002 were then simulated using the calibrated watershed 

models in the Pine Nut Mountains. The daily mean values of 

precipitation, runoff, evapotranspiration, and ground-water 

inflow simulated from the watershed models were summed to 

provide annual mean rates and volumes for each year of the 

simulations, and mean annual rates and volumes computed for 

water years 1990–2002.

Mean annual bias for the period of record for models of 

Daggett Creek and Fredericksburg Canyon watersheds, two 

gaged perennial watersheds in the Carson Range, was within 

4 percent and relative errors were about 6 and 12 percent, 

respectively. Model fit was not as satisfactory for two gaged 

perennial watersheds, Pine Nut and Buckeye Creeks, in the 

Pine Nut Mountains. The Pine Nut Creek watershed model 

had a large negative mean annual bias and a relative error of 

-11 percent, underestimated runoff for all years but the wet 

years in the latter part of the record, but adequately simulated 

the bulk of the spring runoff most of the years. The Buckeye 

Creek watershed model overestimated mean annual runoff 

with a relative error of about -5 percent when water year 1994 

was removed from the analysis because it had a poor record. 

The bias and error of the calibrated models were within 

generally accepted limits for watershed models, indicating 

the simulated rates and volumes of runoff and ground-water 

inflow were reasonable.

Precipitation and Runoff Simulations of the Carson 

Range and Pine Nut Mountains, and Updated Estimates 

of Ground-Water Inflow and the Ground-Water Budgets 

for Basin-Fill Aquifers of Carson Valley, Douglas County, 

Nevada, and Alpine County, California

By Anne E. Jeton and Douglas K. Maurer
The total mean annual ground-water inflow to Carson 

Valley computed using estimates simulated by the watershed 

models was 38,000 acre-feet, including ground-water inflow 

from Eagle Valley, recharge from precipitation on eolian 

sand and gravel deposits, and ground-water recharge from 

precipitation on the western alluvial fans. The estimate was 

in close agreement with that obtained from the chloridebalance method, 40,000 acre-feet, but was considerably 

greater than the estimate obtained from the water-yield 

method, 22,000 acre-feet. The similar estimates obtained 

from the watershed models and chloride-balance method, two 

relatively independent methods, provide more confidence that 

they represent a reasonably accurate volume of ground-water 

inflow to Carson Valley. However, the two estimates are not 

completely independent because they use similar distributions 

of mean annual precipitation.

Annual ground-water recharge of the basin-fill aquifers 

in Carson Valley ranged from 51,000 to 54,000 acre-feet 

computed using estimates of ground-water inflow to Carson 

Valley simulated from the watershed models combined with 

previous estimates of other ground-water budget components. 

Estimates of mean annual ground-water discharge range from 

44,000 to 47,000 acre-feet. The low range estimate for groundwater recharge, 51,000 acre-feet per year, is most similar to 

the high range estimate for ground-water discharge, 47,000 

acre-feet per year. Thus, an average annual volume of about 

50,000 acre-feet is a reasonable estimate for mean annual 

ground-water recharge to and discharge from the basin-fill 

aquifers in Carson Valley.

The results of watershed models indicate that significant 

interannual variability in the volumes of ground-water inflow 

is caused by climate variations. During multi-year drought 

conditions, the watershed simulations indicate that groundwater recharge could be as much as 80 percent less than the 

mean annual volume of 50,000 acre-feet.

Introduction

Rapid population growth (+49 percent from 1990 to 

2000; Economic Research Service, 2003) and changing land 

use in Carson Valley, Douglas County, Nevada, is creating 

an increasing demand for potable water and concern over the 

continued availability of water to sustain future growth. Waterand land-use changes may alter the distribution and magnitude 

of ground-water recharge and discharge and consequently 

may alter flows in the Carson River, affecting water users 

downstream of Carson Valley, who depend on sustained 

river flow (fig. 1). As competition grows for limited water 

resources, water managers increasingly rely on the groundwater system to supply future water demand. Management of 

ground-water resources relies on reasonably accurate recharge 

rates, an important component of the ground-water budget; 

however, the commonly used methods to estimate recharge 

are limited by the scale of application (Cherkauer, 2004). A 

watershed-scale method for estimating ground-water recharge 

and other ground-water budget components uses processbased models that compute distributed water budgets for 

individual watersheds—a scale useful and familiar to water 

managers (Ely, 2006).

The U.S. Geological Survey (USGS) recently made 

estimates of water-budget components for basin-fill aquifers 

beneath the floor of Carson Valley (Maurer and Berger, 2007). 

A major water-budget component included ground-water 

inflow to the basin-fill aquifers of Carson Valley from the 

Carson Range and Pine Nut Mountains. Ground-water inflow 

was estimated to range from 22,000 acre-ft/yr using a wateryield method to 40,000 acre-ft/yr using a chloride-balance 

method (Maurer and Berger, 2007, p. 38).

Because of the relatively large range in these estimates 

and uncertainties in each method noted by Maurer and Berger 

(2007, p. 55), the U.S. Geological Survey, in cooperation 

with Douglas County, Nevada, and the Carson Water 

Subconservancy District, began a study in 2006 to update 

ground-water-budget estimates for Carson Valley using 

watershed models. Results of the models provide independent 

estimates of ground-water inflow to basin-fill aquifers 

underlying Carson Valley, and ephemeral runoff tributary to 

Carson Valley, both major components of the ground-water 

budget for Carson Valley.

The estimates of ground-water inflow simulated by the 

models provide information to update estimates of mean 

annual ground-water recharge to basin-fill sediments of 

Carson Valley. The estimate of mean annual ground-water 

recharge provides an estimate of the perennial yield of the 

basin-fill aquifers, defined by the Nevada Division of Water 

Planning (1992, p. 73) as:

“The amount of usable water from a ground-water 

aquifer that can be economically withdrawn and 

consumed each year for an indefinite period of time. 

It can not exceed the natural recharge to that aquifer 

and ultimately is limited to the maximum amount of 

discharge that can be utilized for beneficial use.”

Perennial yield typically is used by the Nevada State 

Engineer to determine the maximum limit of ground-water 

pumping allowed in a ground-water basin. However, recent 

publications have noted the inadequacy of using perennial 

yield as a limit to protect water resources (Bredehoeft, 1997; 

Sophocleous, 1997). The authors of these publications point 

out that the ultimate results of ground-water pumping are 

to increase, or induce, ground-water recharge, decrease 

ground-water discharge, or some combination of the two. 

2 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Figure 1. Location of the Carson River Basin and the Carson Valley hydrographic areas, Nevada and California.

nv19-4131_Fig01

NEVADA

CALIFORNIA

NEVADA

CALIFORNIA

Truckee

River

Walker

Walker

River

River

West

Walker River

East

East

West

Fork

Fork

Humboldt

River

Carson

Lake

Stillwater

Point

Reservoir

CARSON

SINK

Lahontan

Reservoir

Pyramid

Lake

Lake

Tahoe

CARSON RIVER

Truckee Canal

Pine Nut Mounta ni s

Los

Angeles

Las Vegas

CARSON

RIVER

BASIN

San

Francisco

Reno

CALIFORNIA

NEVADA

S i e r r a N e v a d a

Carson Valley

study area

120° 119° 118°

40°

39°

EXPLANATION

Boundary of Carson River basin

Boundary of hydrographic areas

Base from U.S. Geological Survey digital data, 1:100,000, 1988.

Universal Transverse Mercator projection, zone 11.

North American Datum of 1983 (NAD 83).

0 10 20 30 40 MILES

100 20 30 40 50 60 KILOMETERS

Carson Valley

study area

Reno

Dayton

Minden

CARSON

CITY

Gardnerville

Markleeville

Woodfords

Fernley

Silver

Springs

Hazen

Fallon Lahontan

Dam

Bradys Hot

Springs

Carson Range

Lahontan

Valley

Churchill

Valley

Dayton

Valley

Eagle

Valley

Introduction 3
Additionally, they state that streams and wetlands may be 

affected by ground-water pumping long before pumping 

reaches the volume of perennial yield. Prudic and Wood 

(1995, p. 10) have shown that in Carson Valley, pumping 

increases recharge through water losses from channels of the 

Carson River and irrigation ditches, and decreases groundwater discharge to the Carson River. These effects are caused 

by the hydraulic connection between the aquifer and surfacewater flow created by the permeable sediments and shallow 

depth to water beneath much of the valley floor.

Bredehoeft (1997) and Sophocleous (1997) both note the 

utility of ground-water flow models to quantify the changes in 

recharge and discharge caused by pumping. Such a model is 

currently being developed for the basin-fill aquifers of Carson 

Valley by the USGS in cooperation with the Carson Water 

Subconservancy District. Results of the watershed modeling 

also provide a means to spatially and temporally distribute 

estimates of ground-water recharge near the boundaries of 

the numerical ground-water flow model. The model will 

provide a useful tool for the State Engineer and water planners 

to evaluate the ultimate effects of different ground-water 

management options on the water resources of Carson Valley.

Purpose and Scope

This report documents the development and calibration 

of precipitation-runoff models for watersheds with perennial 

streams, and for watersheds with ephemeral streams in the 

Carson Range and Pine Nut Mountains and presents estimates 

of ground-water inflow to basin-fill aquifers of Carson Valley 

based on the model results. The model results were compared 

with previous estimates of ground-water inflow to Carson 

Valley, and used to update the ground-water budget for basinfill aquifers of Carson Valley.

The precipitation-runoff models were developed using the 

Precipitation-Runoff Modeling System (PRMS: Leavesley and 

others, 1983) within the Modular Modeling System (MMS: 

Leavesley and others, 1996). Input data used in the models 

were daily precipitation and daily minimum and maximum 

air temperature from four National Weather Service Stations 

and one Natural Resources Conservation Service high-altitude 

station, land-cover and soils data, and slope, aspect, and 

altitude. Model output consisted of runoff, evapotranspiration, 

and ground-water inflow.

The precipitation-runoff models were calibrated against 

measured runoff for water years 1990–2001 and 1990–2002 

for two gaged watersheds with perennial streams in the Carson 

Range, and for water years 1981–97 for two gaged watersheds 

with perennial streams in the Pine Nut Mountains. Runoff 

and ground-water inflow from 10 ungaged watersheds with 

perennial streams in the Carson Range were simulated using 

the model parameters from the calibrated models having 

similar bedrock geology for water years 1990–2002. The 

models of watersheds with ungaged perennial streams were 

calibrated against runoff estimated in an earlier study. The 

precipitation-runoff models were calibrated to match the 

full period of record for each respective watershed rather 

than using separate calibration and verification periods. This 

allowed for a direct comparison to the mean annual water 

budget values estimated from earlier studies.

Additionally, 11 watersheds with ungaged ephemeral 

streams were modeled, 10 in the Carson Range and 1 large 

aggregated area on the east side of Carson Valley, using the 

model parameters from the calibrated models of watersheds 

with gaged perennial streams having similar bedrock geology. 

For brevity, in the remainder of the report, the modeled 

watersheds will be referred to as perennial and ephemeral 

watersheds, although the term actually applies to the streams 

themselves. Simulated ground-water inflow and ephemeral 

runoff were used to update estimates of ground-water 

inflow from the Carson Range and Pine Nut Mountains. The 

updated estimates of ground-water inflow were combined 

with previous estimates of other ground-water recharge 

components, to obtain an updated ground-water budget for 

basin-fill aquifers of Carson Valley.

Geographic Setting

Carson Valley is primarily in Douglas County, Nevada, 

about 4 mi south of Carson City, Nevada’s capital (figs. 1

and 2). The southern end of the valley extends about 3 mi into 

Alpine County, California (fig. 2). The floor of the valley is 

oval-shaped, about 20 mi long and 8 mi wide, and slopes from 

an altitude of about 5,000 ft at the southern end to about 4,600 

ft at the northern end. The Carson Range on the western side 

of the Sierra Nevada rises abruptly from the valley floor with 

mountain peaks ranging in altitude from 9,000 to 11,000 ft, 

whereas, the Pine Nut Mountains on the eastern side rise more 

gradually to peaks ranging in altitude from 8,000 to 9,000 ft.

The major towns in the valley are Minden and 

Gardnerville (fig. 2) with populations of 2,800 and 3,400, 

respectively (U.S. Census Bureau, 2003). Three subdivisions, 

Gardnerville Ranchos south of Gardnerville, and Johnson 

Lane and Indian Hills north of Minden, are growing rapidly, 

with populations of 11,000, 4,800, and 4,400, respectively 

(U.S. Census Bureau, 2003). In addition, development is 

increasing along the eastern and western sides of the valley, 

and on the valley floor on land that historically has been 

agricultural. Douglas County has grown from a population 

of about 28,000 in 1990 to 41,000 in 2000, an increase of 46 

percent (Economic Research Service, 2003).

4 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Figure 2. Location of the Carson Valley study area and depth to water table, Nevada and California, June 2005.

nv19-4131_Fig02

PIN

E

N

U

T

MOUNTA

NI S

PIN

E

N

U

T

MOUNTA

NI S

Base from U.S. Geological Survey digital data, 1:100,000, 1988.

Universal Transverse Mercator projection, zone 11.

North American Datum of 1983 (NAD 83).

CARSON

RIVER

Buckeye Creek

Pine Nut Creek

Clear Creek

Indian Creek

EAST FORK

WEST FORK

CARSON

RIVER

Buckeye Creek

Pine Nut Creek

Clear Creek

Indian Creek

EAST FORK

WEST FORK

Johnson Lane

Airport

Muller Lane

Mottsville Lane

Centerville 

Lane

207

395

395

50

50

208 89

88

88

Fish

Spring

Flat

Indian

Hills

Snowshoe Thompson Ditches

Hot Springs

Mountain

Diamond

Valley

Jack's

Valley

C

ARSO

N

R

A

N

GE

PIN

E

N

U

T

MOUNTA

NI S

CARSON CITY CO

DOUGLAS CO

NEVADA

CALIFORNIA

DOUGLAS COUNTY

ALPINE COUNTY

LYON COUNTY

Gardnerville

Minden

Carson City

Fish

Spring

Flat

Indian

Hills

Snowshoe Thompson Ditches

Hot Springs

Mountain

Diamond

Valley

Jack's

Valley

C

ARSO

N

R

A

N

GE

CARSON CITY CO

DOUGLAS CO

NEVADA

CALIFORNIA

DOUGLAS COUNTY

ALPINE COUNTY

LYON COUNTY

Gardnerville

Minden

Genoa

Carson City

Gardnerville

 Ranchos PINE

N

U

T

M

O

U

N

TAIN

S

5

5

50

200

150

100

50

400

100

20

20

5

20

20

20

200

5

5

200

200

200

50

100

150

100

20

200

50

50

100

50 100

50

50

150

200

200

50

100

20

20

150

200

100

100

200

5

5

50

200

150

100

50

400

100

20

20

5

20

20

20

200

5

5

200

200

200

50

100

150

100

20

200

50

50

100

50 100

50

50

150

200

200

50

100

20

20

150

200

100

100

200

119° 52' 30" 119° 45' 119° 37' 30" 119° 30'

39°

07'

30"

39°

00'

38°

52'

30"

38°

45'

0

0

Ruhenstroth

6 8 10

6

4

4

2

2

12 MILES

8 10 12 14 16 18 KILOMETERS

Line of equal depth to water. Interval, in

 feet, is variable. Datum is land surface.

 Modified from Maurer and Peltz (1994)

EXPLANATION

50

Long-term streamflow gaging station on

 Carson River 

Introduction 5
The Carson Valley study area is a subarea of the 

entire Carson Valley Hydrographic Area and includes the 

portion of the hydrographic area underlain by permeable 

materials capable of transmitting ground water to aquifers 

beneath the floor of Carson Valley (figs. 1 and 2). Along 

the southern boundary, the headwaters of the West and 

East Forks of the Carson River were not included in the 

study area because bedrock underlies the points where the 

West and East Forks of the Carson River cross the study 

area boundary, restricting ground-water inflow. The study 

area boundary covers 253,570 acres, or about 396 mi2.

The valley floor is covered with native pasture 

grasses, croplands of primarily alfalfa, and near the 

northern end of the valley, phreatophytes such as 

greasewood, rabbitbrush, and big sage. On the western side 

of the valley, bitterbrush and sagebrush cover steep alluvial 

fans, and manzanita and ponderosa pine cover the slopes 

of the Carson Range. Alluvial fans and foothills of the 

Pine Nut Mountains on the eastern side of the valley are 

covered with sage and rabbitbrush, and pinyon and juniper 

grow at high altitudes on the Pine Nut Mountains.

Geologic Setting

The distribution of surficial geologic units in Carson 

Valley is shown in figure 3. The geologic units of Stewart 

and Carlson (1978) were grouped into unconsolidated 

alluvial fan, gravel, eolian sand, and basin-fill deposits 

of Quaternary age, volcanic rocks and semiconsolidated 

sediments of Tertiary age, granitic rocks of Cretaceous 

age, and metamorphic rocks of Triassic to Jurassic age.

During the Cretaceous Period, 63 to 138 million 

years (m.y.) ago, the granitic magma of the Sierra Nevada 

pluton intruded into sedimentary and volcanic rocks 

of the Triassic and Jurassic Periods (138 to 240 m.y. 

ago). The resulting granodioritic and metavolcanic and 

metasedimentary rocks form the bulk of the Carson Range 

of the Sierra Nevada and the Pine Nut Mountains (fig. 3), 

and underlie the floor of Carson Valley (Moore, 1969, 

p. 18; Pease, 1980, p. 2). The Tertiary semiconsolidated 

sediments are exposed on the eastern side of the valley 

and likely also underlie Quaternary basin-fill sediments 

beneath the valley floor. Basin and Range faulting took 

place from 10 to 7 m.y. ago, producing the present 

topography of Carson Valley by uplifting the Carson 

Range and Pine Nut Mountains and downdropping the 

floor of Carson Valley (Muntean, 2001, p. 9).

 The mountain blocks bounding Carson Valley are 

west-tilted structural blocks (Stewart, 1980, p. 113), with 

the valley occupying the downdropped western edge 

of the Pine Nut Mountains block (Moore, 1969, p. 18). 

A steep, well-defined normal fault creates a 5,000 ft 

escarpment along the Carson Range on the west, whereas 

nv19-4131_Fig03_Explan

EXPLANATION FOR FIGURE 3

Quaternary

Surficial Geologic Units

Alluvial fans

Tertiary

Granitic rocks

Cretaceous

Metamorphic rocks

Triassic and Jurassic 

Precipitation station and No.

Precipitation storage gage

Gaging station

Fault—Dashed where approximately located

1e 

Basin-fill deposits

Gravel deposits

Eolian sand 

Semiconsolidated sediments 

Boundary of perennial watershed and No.— 

 “u” indicates ungaged watershed,

 “g” indicates gaged watershed

Boundary of ephemeral watershed and No.

Boundary of Carson Valley study area 

Runoff measurement site

Volcanic rocks

6p

12g6u

a diffuse fault zone is found on the eastern side of the valley, 

dividing the Pine Nut Mountains block into several smaller 

blocks (fig. 3). Evidence of continued westward tilting is 

demonstrated by recent faulting along the base of the Carson 

Range (Pease, 1980, p. 15) and by displacement of the Carson 

River to the extreme western side of the valley (Moore, 1969, 

p. 18). A gravity survey by Maurer (1984) indicates that the 

depth to consolidated bedrock beneath the western half of 

Carson Valley is as great as 5,000 ft.

6 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Figure 3. Surficial geologic units and faults in Carson Valley, perennial and ephemeral watersheds, and the 

locations of precipitation and runoff gaging or measurement stations used in watershed model development, 

Nevada and California.

nv19-4131_Fig03

US

50

US

395

US

50

US

395

SR

88

SR

207

US

395 SR

88

SR

89 SR

208

3p

4p

1p

2p

5p

6p

Lower Pine Nut

storage gage

Upper Pine

Nut

storage

gage

West

Fork

East Fork

Carson River

Carson City County

Douglas County

Douglas County

Washoe County

NEVADA

CALIFORNIA

Douglas County

Alpine County

Lyon County

Carson City County

CARSON

RANGE

PINE NU

T

MOUNTA

NI S

5e

6e

1e

10e

8e

3e

9e

2e

4e

7e

11e

14g

13g

5g

11u

3u

1u

12g

7u

8u

10u

4u

2u

6u

9u

Area of figure 7

119° 52' 32" 119° 45' 119° 37' 30" 119° 30'

39° 07' 30"

39° 00'

38° 52' 30"

38° 45'

Carson City

Genoa

Gardnerville

Minden

0

0

2 4 6 8

2 4 6 8 MILES

10 12 KILOMETERS

Base from U.S. Geological Survey digital data, 1:100,000, 1988 Universal Transverse Mercator projection, zone 11. 

Shaded-relief from 30-meter Digital Elevation Model: Sun illumination from northwest at 30 degrees above horizon. 

Base geology from Stewart and Carlson (1978) at 1:250,000 scale. Modified from geologic mapping by Stewart (1999) 

at 1:100,000 scale; by Armin and John (1983), Stewart and Noble (1979) at 1:62,500 scale; and by dePolo and others 

(2000), Garside and Rigby (1998), and Muntean (2001) at 1:24,000 scale. Faults from U.S. Geological Survey (2003).

Introduction 7
Hydrologic Setting

Carson Valley lies in the rainshadow of the Carson 

Range, with annual precipitation at the town of Minden on the 

valley floor averaging 8.4 in/yr (period of record 1971–2000; 

National Oceanic and Atmospheric Administration, 2002, p. 

12). In contrast, the top of the Carson Range receives about 

40 in/yr and the top of the Pine Nut Mountains receives 

from 15 to 18 in/yr (Maurer and Halford, 2004, p. 35). From 

1984 to 1992 and from 1999 to 2004, conditions were dry 

with annual precipitation less than average (fig. 4A). The 

Palmer Drought Severity Index (PDSI; National Oceanic 

and Atmospheric Administration, 2006) is based on longterm weather conditions and provides a cursory indication of 

regional meteorological wet or dry periods (fig. 4C). The PDSI 

indicates that the longest recorded period of severe to extreme 

drought conditions was from 1999 to 2004.

The hydrology of Carson Valley is dominated by flow 

of the Carson River. The East and West Forks of the Carson 

River enter from the southern parts of the valley and flow 

northward to join near Genoa (fig. 2). The combined flow 

continues north to leave the valley southeast of Carson City. 

Flow of the Carson River is diverted across the valley floor 

through a network of canals and ditches for flood irrigation 

of crops and native pasture grasses. Twelve perennial streams 

drain the Carson Range, their flow reaches the valley floor 

even during extended periods of drought (fig. 3; Maurer and 

Berger, 2007, p. 36). Only two perennial streams, Buckeye 

and Pine Nut Creeks, drain the Pine Nut Mountains and their 

flow only rarely reaches the valley floor, becoming ephemeral 

a short distance downstream of their gaging stations (fig. 3) 

Ten ephemeral watersheds also drain the Carson Range, and a 

large area of ephemeral runoff is present on the eastern side of 

the valley. However, runoff from these ephemeral watersheds 

has not been measured.

Infiltration of surface water through streambeds and 

ditches and beneath flood-irrigated fields maintains a shallow 

water table less than 5 ft below land surface beneath much 

of the valley floor (fig. 2). Depth to the water table beneath 

alluvial fans on the western side of the valley quickly increases 

to greater than 200 ft within 1 mi of the valley floor, whereas 

depth to the water table on the eastern side of the valley 

reaches 200 ft about 3 mi from the valley floor (fig. 2).

Ground water flows downgradient from the Carson 

Range on the west and the Pine Nut Mountains on the east 

towards the Carson River on the valley floor. Beneath alluvial 

fans on the western side of the valley, ground water flows 

eastward and the gradient is about 100 ft/mi, whereas on the 

eastern side of the valley, ground water flows westward and 

the gradient ranges from 20 to 100 ft/mi (Maurer, 1986, p. 18). 

Beneath the valley floor, ground water flows toward the north 

and gradients range from about 100 ft/mi in the southwestern 

part of the valley to about 5 ft/mi in the northern part of the 

valley (Berger and Medina, 1999). Maurer (1986, p. 18), 

Maurer (2002, p. 10), and Maurer and Berger (2007, p. 57) 

present water-level data that indicate ground water flows from 

semiconsolidated sediments on the eastern side of the valley 

towards the valley floor.

Unconsolidated sediments that form the alluvial fans 

surrounding the valley, and that underlie the flood plain of 

the Carson River are the principal aquifers in Carson Valley 

(Maurer, 1986, p. 17). In the semiconsolidated Tertiary 

sediments, lenses of sand and gravel are the primary waterbearing units, and probably transmit most ground-water flow 

through the units. The consolidated granitic and metamorphic 

rocks forming the bulk of the Carson Range and Pine Nut 

Mountains are much less permeable to ground-water flow than 

other geologic units in Carson Valley. However, numerous 

wells have been drilled in the consolidated rocks that provide 

sufficient water for domestic use from fractured or weathered 

zones.

Components of the Ground-Water Budget for 

Basin-Fill Sediments of Carson Valley

The components of the ground-water budget for basin-fill 

sediments of Carson Valley were delineated by Maurer and 

Berger (2007, p. 20). The major component of ground-water 

recharge to basin-fill sediments is ground-water inflow from 

the Carson Range and Pine Nut Mountains (fig. 5). Groundwater inflow was estimated by Maurer and Berger (2007) from 

the perspective of the basin-fill aquifers beneath the floor of 

Carson Valley. For this reason, the term ground-water inflow 

was used to describe ground-water flow from watersheds in 

the Carson Range and Pine Nut Mountains. Ground-water 

inflow from the Carson Range includes inflow from perennial 

and ephemeral watersheds, and inflow from infiltration of 

8 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Figure 4. Annual precipitation at Minden, Nevada, and Heavenly Valley, California, and Palmer 

Drought Severity Index for western Nevada.

nv19-4131_Fig04

0

2

4

6

8

10

12

14

16

18

20

A. Minden, Nevada

 Period of record: 1930–2005 

Average annual precipitation, 8.4 in. (1971–2000)

0

5

10

15

20

25

30

35

40

45

50

55

60

65

B. Heavenly Valley, California

 Period of record: 1979–2005

Average annual precipitation, 34.5 in. (1979–2005)

1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 

PALMER DROUGHT SEVERITY INDEX

-8

-6

-4

-2

0

2

4

6

8

10

Area of severe to extreme wetness

Area of severe to extreme drought

C. Palmer Drought Severity Index for western Nevada

ANNUAL PRECIPITATION, IN INCHES

Introduction 9
precipitation and ephemeral runoff on the western alluvial 

fans. Maurer and Berger (2007, p. 36) concluded that 

infiltration of perennial runoff on the western alluvial fans was 

negligible. Ground-water inflow from the Pine Nut Mountains 

includes ground-water inflow from perennial and ephemeral 

watersheds, and ground-water inflow from infiltration of 

ephemeral runoff. The term ground-water inflow is used 

throughout this report to remain consistent with previous 

descriptions of ground-water movement into the basin-fill 

aquifers of Carson Valley.

Such ground-water inflow is not strictly considered 

ground-water recharge because the flow does not cross the 

water table (Freeze and Cherry, 1979, p. 211). However, for 

the purposes of this study, which is focused on the basin-fill 

aquifers of Carson Valley, ground-water inflow entering basinfill aquifers from the mountain blocks was considered groundwater recharge.

Maurer and others (2006, p. 28) used soil-chloride data 

to show that recharge from precipitation does not take place 

at most locations on alluvial fans and semiconsolidated 

Figure 5. Components of ground-water recharge to and discharge from basin-fill aquifers of Carson Valley, Nevada and California.

nv19-4131_Fig05

Carson Range

Includes: Includes:

Net ground-water

pumping

Ground-water

evapotranspiration

from phreatophytes

Ground-water

inflow from

Eagle Valley

Ground-water recharge

from precipitation on eolian

sand and gravel deposits

Ground-water

recharge from

streamflow loss

Ground-water

discharge to

streamflow

Secondary

recharge of

pumped

ground water

Ground-water inflow

from Pine Nut Mountains

–Ground-water inflow from

 perennial and ephemeral

 watersheds

–Infiltration of ephemeral runoff and

 infiltration of perennial runoff

 from Pine Nut and Buckeye Creeks

Ground-water

inflow from

Carson Range

–Ground-water inflow from

 perennial and ephemeral

 watersheds

–Infiltration of precipitation

 and ephemeral runoff

 on western alluvial fans

Pine Nut

Mountains

Basin-fill aquifers

of Carson Valley

sediments on the eastern side of Carson Valley. The soilchloride data showed that ground-water recharge from 

precipitation does take place on eolian sand and gravel 

deposits in the northern part of Carson Valley (fig. 3), although 

at relatively low rates.

Ground-water inflow to the basin-fill deposits of Carson 

Valley from the Carson Range and Pine Nut Mountains was 

estimated by Maurer and Berger (2007) using a water-yield 

method and a chloride-balance method. The water-yield 

method uses an equation developed for nearby Eagle Valley 

(Maurer and Berger, 1997, p. 34) that computes estimates of 

water yield, defined by Maurer and Berger (1997) as the sum 

of runoff and ground-water inflow, from annual precipitation. 

The equation was applied to precipitation estimates for each 

watershed made by Maurer and Berger (2007, p. 29) using 

the linear relations of Maurer and Halford (2004) to estimate 

water yield from the perennial watersheds. The estimates of 

runoff from the perennial watersheds by Maurer and others 

(2004, p. 14) were subtracted from the computed water yield 

to obtain estimates of ground-water inflow.

10 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
The estimates of ground-water inflow from the wateryield method were combined with estimates of inflow from 

infiltration of precipitation and ephemeral runoff on the 

western alluvial fans to obtain the total ground-water inflow to 

basin-fill aquifers in Carson Valley (Maurer and Berger, 2007, 

p. 38). Maurer and Berger (2007) assumed that ephemeral 

runoff is largely lost to infiltration and that infiltration of 

ephemeral runoff becomes ground-water inflow to the basinfill aquifers of Carson Valley. The total ground-water inflow 

to the basin-fill deposits of Carson Valley estimated using the 

water-yield method was 22,000 acre-ft/yr (Maurer and Berger, 

2007, p. 40).

The chloride-balance method uses a chloride massbalance equation (Wilson and Guan, 2004, p. 122; Maurer 

and Berger, 2007, p. 34). The method assumes that chloride 

deposited from precipitation is concentrated in the subsurface 

as water is lost to evapotranspiration (ET) in the mountains 

and on alluvial fans. The masses of chloride deposited by 

precipitation and removed in runoff are determined from the 

chloride concentrations of precipitation and runoff multiplied 

by their mean annual volumes. The mass of chloride from 

precipitation minus the mass of chloride in runoff is divided 

by the chloride concentration of ground water in basinfill aquifers to estimate ground-water inflow. The estimate 

includes ground-water inflow from perennial and ephemeral 

watersheds and from infiltration of runoff and precipitation on 

the alluvial fans when the chloride concentration of ground 

water near the toe of the alluvial fans is used (Wilson and 

Guan, 2004, p. 123). Ground-water inflow to Carson Valley 

estimated using the chloride-balance method was 40,000 acreft/yr (Maurer and Berger, 2007, p. 40).

Other components of ground-water recharge estimated 

by Maurer and Berger (2007) include ground-water inflow to 

the northern end of Carson Valley from Eagle Valley, groundwater recharge from precipitation on eolian sand and gravel 

deposits, ground-water recharge from streamflow of the 

Carson River and irrigation ditches, and secondary recharge of 

pumped ground water (fig. 5). Using streambed temperature 

data, and data on ground-water levels compared to stream 

stage, Maurer and Berger (2007, p. 51) showed that the Carson 

River and irrigation ditches generally lose flow to groundwater recharge on the southern and southeastern parts of 

Carson Valley, and gain flow from ground-water discharge on 

the western and northern parts of Carson Valley. Components 

of ground-water discharge estimated by Maurer and Berger 

(2007) include ground-water discharge by evapotranspiration 

(ET) of phreatophytes, ground-water discharge to streamflow, 

and net ground-water pumping.

Water-budget estimates by Maurer and Berger (2007) 

were representative of water years 1990–2005. The estimates 

of ground-water recharge from discharge to the Carson River, 

net ground-water pumping, and secondary recharge of pumped 

ground water were made from analyses of streamflow gains 

and losses, and data on annual pumping averaged over the 

period 1990–2005. The estimates of ET were based on a 

land-use map developed from imagery collected in 2004 and 

updated by field checks for 2005. Estimates of ground-water 

inflow used mean annual runoff for 1990–2002, and mean 

annual precipitation for 1971–2000.

In this report, water-budget components simulated by the 

watershed models are mean annual values representative of 

water years 1990–2002, the period for which measured and 

estimated daily mean runoff data were available for model 

calibration. The estimates were combined with other waterbudget components estimated by Maurer and Berger (2007) 

for water years 1990–2005, under the assumption that the 

two periods have similar hydrologic conditions. Mean annual 

precipitation at Heavenly Valley, near the crest of the Carson 

Range averaged 33.29 in. for water years 1990–2002 and 

33.26 in. for water years 1990–2005. Similarly, mean annual 

precipitation at Minden, Nev., on the floor of Carson Valley 

averaged 8.72 in. for water years 1990–2002 and 8.67 in. for 

water years 1990–2005; indicating only a small difference in 

mean annual precipitation during the two periods.

Description of Watershed Models

Models were developed for gaged and ungaged perennialstream watersheds and ungaged ephemeral-stream watersheds 

in the study area. Watershed models for four gaged perennial 

watersheds were calibrated for this study; Daggett Creek 

(watershed 5g), Fredericksburg Canyon (watershed 12g), Pine 

Nut Creek (watershed 13g), and Buckeye Creek (watershed 

14g; fig. 3, table 1). Models were then developed for the 10 

ungaged perennial watersheds in the Carson Range (fig. 3 and 

table 1) having estimates of daily mean runoff from a previous 

study (watersheds 1u–4u and 6u–11u; Maurer and Berger, 

2007).

Description of Watershed Models 11
Models for the ungaged perennial watersheds were 

developed using the calibrated models for either the Daggett 

Creek or Fredericksburg Canyon watersheds as an index 

model, meaning that PRMS parameters of the index model 

were used in building the preliminary model for the ungaged 

watersheds. Selection of which gaged watershed model to 

use as an index model was based on the similarity between 

gaged and ungaged watersheds of (1) major bedrock type, and 

(2) runoff as a percentage of precipitation as determined by 

Maurer and Berger (2007, p.29). The Daggett Creek watershed 

is underlain by granitic bedrock and about 21 percent 

of precipitation becomes runoff (table 1), whereas the 

Fredericksburg Canyon watershed is underlain by a mixture 

of granitic and metamorphic bedrock and a relatively large 

amount, about 45 percent, of precipitation becomes runoff.

Table 1. Major bedrock type, runoff as a percentage of precipitation, index model, and precipitation stations used for model 

development of perennial gaged and ungaged watersheds, Nevada and California. 

[Watershed No.: “u” is ungaged, “g” is gaged. Locations are shown in figure 3. Runoff efficiency: Runoff as a percentage of precipitation from Maurer and 

Berger (2007, p. 29). Index model: Watershed model for gaged watershed used as index for models of ungaged watersheds. Abbreviations: –, indicates no index 

model used]

Watershed 

No. Watershed name Major bedrock type

Runoff 

efficiency 

(percent)

Index model

Altitude of precipitation station

Low High

1u Water Canyon Metamorphic and 

granitic

45 Fredericksburg 

Canyon

Sheridan Acres Daggett Pass

2u James Canyon Metamorphic 38 Fredericksburg 

Canyon

Sheridan Acres Daggett Pass

3u Sierra Canyon Metamorphic and 

granitic

31 Daggett Creek Sheridan Acres Daggett Pass

4u Genoa Canyon Granitic 30 Daggett Creek Sheridan Acres Daggett Pass

5g Daggett Creek Granitic 21 – Sheridan Acres Daggett Pass

6u Mott Canyon Granitic 52 Fredericksburg 

Canyon

Sheridan Acres Heavenly Valley

7u Monument 

Creek

Granitic 74 Fredericksburg 

Canyon

Sheridan Acres Heavenly Valley

8u Stutler Canyon Granitic 11 Daggett Creek Sheridan Acres Heavenly Valley

9u Sheridan 

Creek

Granitic 93 Fredericksburg 

Canyon

Sheridan Acres Heavenly Valley

10u Jobs Canyon Granitic 31 Daggett Creek Sheridan Acres Heavenly Valley

11u Luther Creek Granitic 30 Daggett Creek Sheridan Acres Heavenly Valley

12g Fredericksburg 

Canyon 

Metamorphic and 

granitic

45 – Sheridan Acres Heavenly Valley

13g Pine Nut 

Creek

Metamorphic 8 – Minden (1980–91)

Fish Springs 

(1992–2002)

Minden (1980–91)

Fish Springs 

(1992–2002)

14g Buckeye 

Creek

Granitic 2 – Minden (1980–91)

Fish Springs 

(1992–2002)

Minden (1980–91)

Fish Springs 

(1992–2002)

12 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Finally, models were developed for ephemeral watersheds 

to estimate the quantity of ephemeral runoff tributary to 

Carson Valley and the potential for ground-water inflow from 

ephemeral watersheds. Models were developed for 10 of the 

larger ephemeral watersheds of the Carson Range (watersheds 

1e–10e, fig. 3) and a large area near the Pine Nut Mountains 

where runoff is ephemeral (watershed 11e) Similar to the 

models developed for the ungaged perennial watersheds, 

either the Daggett Creek or Fredericksburg Canyon watershed 

models were used as index models for the ephemeral 

watershed models of the Carson Range. Because the volume 

of ephemeral runoff is uncertain, selection of the index model 

was based only on the bedrock type underlying the ephemeral 

watershed. The Buckeye Creek model (table 1) was used as an 

index model for the area of ephemeral runoff on the eastern 

side of the valley. The Buckeye Creek model was used rather 

than the Pine Nut Creek model because the overall geology 

underlying the Buckeye Creek watershed is more similar to 

that of the area of ephemeral runoff. It consists of a mixture 

of consolidated rocks, semiconsolidated sediments, and 

alluvial fans (fig. 3). Index model parameters were used for 

the ephemeral watershed models without adjustment, except 

for an adjustment of the precipitation correction factor as 

discussed in the section, “Runoff and Climate Data.”

Precipitation-Runoff Modeling System

Conceptually, perennial and ephemeral drainages such 

as those on the eastern and western sides of Carson Valley 

can be described in terms of a few key hydrologic processes 

that, working in combination, result in measured runoff 

variations (Beven, 2001). The model used in this study is the 

Precipitation-Runoff Modeling System (PRMS; Leavesley 

and others, 1983). PRMS is a process-based, distributedparameter modeling system designed to analyze the effects of 

precipitation, climate, and land use on runoff and watershed 

hydrology (Leavesley and others, 1983).

The term “process-based” refers to the use of 

mathematical equations to simulate the physical processes of 

the various water-budget components. The term “distributedparameter” refers to the representation of the watershed 

with spatially varying hydrologic characteristics, which 

is represented numerically as a collection of hydrologic 

response units (HRUs) that each have a unique set of physicalparameter values. The term “parameters” used throughout this 

report refers to quantities that define certain relatively constant 

characteristics of the watershed system. When evaluating the 

mathematical representation of the watershed, the independent 

variables are varied, while the parameters are held constant. 

The system may then be reevaluated or reprocessed with 

different parameter values, to simulate a system with different 

behavior.

The PRMS computer program is part of a larger 

modeling system, the Modular Modeling System (MMS) 

(http://wwwbrr.cr.usgs.gov/projects/SW_precip_runoff/

software/software.shtml). MMS combines a library of modules 

that simulate separate components of the hydrologic system 

including water, energy and biochemical processes.

In distributed-parameter precipitation-runoff models, 

the hydrologic processes are parameterized to account for 

the spatial and temporal variability of basin characteristics. 

Although partitioning methods differ, the intent of distributedparameter models is to better conceptualize hydrologic 

processes, to represent these processes at time and space scales 

similar to those in nature, and to reduce model input error, 

thereby improving overall model performance.

The spatial variability of land characteristics that affect 

runoff within watersheds is accounted for in the model 

by dividing the modeled area into Hydrologic Response 

Units (HRUs). A critical assumption is that the hydrologic 

response to uniformly distributed precipitation and simulated 

snowmelt is homogeneous within each HRU. HRUs are thus 

characterized by those physiographic properties that determine 

hydrologic response: altitude, slope, aspect, vegetation, soil, 

geology, and climate. HRUs may consist of noncontiguous 

or contiguous areas of similar properties. Water and energy 

balances reflecting physical and hydrologic characteristics 

and the climate conditions for that day are computed daily 

for each HRU. The HRU is indexed to one or more nearby 

climate stations and precipitation is adjusted within the PRMS 

model with monthly correction factors. Monthly temperature 

lapse rates and precipitation-correction factors are used to 

extrapolate measured daily air temperature and precipitation 

from nearby climate stations to individual HRUs, thereby 

accounting for spatial and altitude differences. The form of 

precipitation (rain, snow, or mixed) is dependent on relations 

between a specified snow-rain threshold temperature and 

minimum and maximum temperatures for each HRU.

Responses to climate events can be simulated in terms of 

water and energy balances, streamflow regimes, flood peaks 

and volumes, soil-water relations, and ground-water recharge 

(represented by the term ground-water sink in fig. 6). Groundwater recharge from the watersheds moves in the subsurface 

to become ground-water inflow to the basin-fill aquifers in 

Carson Valley.

The watershed system is conceptualized as a series of 

interconnected reservoirs, whose collective output produces 

the total hydrologic response (fig. 6). The water-budget 

components (rectangular boxes) denote the storage and 

collection of water and energy. Daily precipitation, daily 

maximum and minimum air temperature, and a surrogate 

for daily solar radiation are inputs that drive the model. 

The surrogate for solar radiation is estimated from daily 

temperature using a modified degree-day method and adjusted 

for slope and aspect. This method is appropriate for use in the 

study area because predominantly clear skies prevail on days 

without precipitation (Frank and Lee, 1966; Swift, 1976). 

Description of Watershed Models 13
Snowmelt is a significant component of the water budget for 

mountainous watersheds. Snowpack components of PRMS 

simulate the initiation, accumulation, and depletion of snow 

on each HRU. The snowpack is simulated both in terms of 

its water storage and as a dynamic-heat reservoir (Anderson, 

1973; Obled and Rosse, 1977; Leavesley and others, 1983). 

A snowpack water balance is computed daily within each 

HRU, and a snowpack energy balance is computed each day 

and night. For moderate-altitude, snow-dominated watersheds 

such as in the Carson Range and the Pine Nut Mountains, 

the importance of seasonal differences in temperature and 

precipitation is reflected in snowpack accumulation and melt 

rates, and ultimately the timing of runoff.

Potential evapotranspiration (PET) was computed using 

a modified version of the Jensen Haise method (Jensen and 

Haise, 1963; Jensen and others, 1969) to account for forest 

canopies and changes in altitude and humidity. Annually 

simulated PET estimates were compared to regional PET 

values for verification (Farnsworth and others, 1982). PET is 

first satisfied in the model by vegetation canopy-interception 

storage, followed by sublimation (snowpack evaporation) 

and impervious-surface evaporation. When snow is present 

and there is no transpiration, sublimation is computed as a 

percentage of the total PET (PRMS assumes no sublimation 

when plants are transpiring). The remaining PET demand is 

satisfied by evaporation from the soil surface and soil-zone 

storage after transpiration begins. The transpiration period 

depends on the plant type and altitude zone contained within 

each HRU. For each year of simulation, a cumulative degreeday index is computed (using daily mean temperature) to 

determine the start of transpiration, allowing for earlier or later 

initiation of the transpiration period during warmer or cooler 

springs, respectively.

nv19-4131_Fig06

Ground-water

reservoir

Subsurface

reservoir

Lower zone

Recharge zone

Impervious-zone reservoir

Snowpack

Interception

Precipitation Solar

radiation

Air

temperature

Evaporation

Sublimation

Evaporation

Transpiration

Transpiration

Sublimation

Evapotranspiration

Throughfall

Snowmelt

Subsurface

recharge

Soil-zone excess

Ground-water sink

(Ground-water inflow)

Interflow

Baseflow In-stream runoff

Overland runoff

Overland runoff

Evaporation

Ground-water

recharge

Ground-water

recharge

Soil-zone

reservoir

PRECIPITATION-RUNOFF MODELING SYSTEM

Figure 6. Schematic diagram of processes simulated by the Precipitation-Runoff Modeling System 

(modified from Leavesley and others, 1983).

14 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
PRMS simulates the soil zone as a simplified two-layer 

system: a shallow, upper zone (called the recharge zone 

in figure 6) where water losses are from soil evaporation 

and transpiration, and a deeper, lower zone where the soilmoisture depletion is by transpiration, ground-water and 

subsurface recharge. In this study, the subsurface is defined 

as the unsaturated zone below the root zone and above 

the water table. The total soil profile depth for each HRU 

is defined as the average rooting depth of the dominant 

vegetation. Actual evapotranspiration (AET) losses from the 

soil zone are simulated as proportional to the remaining PET 

demand and the ratio of currently available soil moisture to 

the maximum water-holding capacity of the soil profile. In 

PRMS, infiltration into the soil-zone reservoir depends on the 

daily snowmelt or net rainfall rates (total precipitation minus 

canopy interception), soil field capacities, specified maximum 

infiltration rates (for snowmelt), and antecedent soil-moisture 

conditions (water in the soil zone prior to infiltration). 

Infiltration thresholds are defined depending on whether the 

water is derived from rain or snowmelt.

The subsurface reservoir represents the pathways that 

the soil-water excess takes in percolating through the shallow 

unsaturated zones to stream channels, arriving at the streams 

above the water table. Soil water in excess of field capacity 

is first used to satisfy recharge to the ground-water reservoir 

and is assumed to have a maximum daily limit. Once this 

limit is reached, further percolation of soil water is routed to 

the subsurface reservoir. Water can then be further allocated 

to the ground-water reservoir or routed directly to the stream 

channel from the subsurface reservoir (fig. 6). The latter is 

referred to as interflow and is computed as a non-linear rate 

using the storage volume of the subsurface reservoir and 

user-defined routing coefficients. Flow from the ground-water 

reservoir is the source of baseflow in the stream. Movement of 

ground water outside the modeled watershed is simulated by 

decreasing the ground-water storage. This portion of the water 

budget is referred to as a ground-water sink. In this study, the 

ground-water-sink flux represents ground-water inflow to the 

basin-fill aquifers of Carson Valley.

Runoff, as simulated by PRMS, is a summation of three 

components: (1) overland runoff from saturated soils or runoff 

from impervious surfaces, (2) interflow from the unsaturated 

zone below the root zone as described above, and (3) baseflow. 

A basic assumption in PRMS is that the runoff travel time, 

from the headwaters to the outlet of a defined model area (a 

tributary watershed, for example) is less than or equal to the 

daily time step, and thus daily runoff need not be explicitly 

routed along stream channels.

In PRMS, the ground-water reservoir can be thought of as 

a bucket from which water in storage is released at a rate that 

satisfies the baseflow component of the measured hydrograph 

(the seasonal runoff recessions). Baseflow is designed to 

respond more slowly to hydrologic fluctuations than interflow. 

The interflow component typically is represented in the stream 

hydrograph as the more immediate response to snowmelt, 

though less rapid than the overland flow component, which 

occurs when net precipitation or snowmelt exceed infiltration 

thresholds.

Model Development

The development of the PRMS model required 

delineating subbasins or watersheds for gaged and ungaged 

perennial and ephemeral watersheds, compiling daily 

time series of runoff and climate data, delineating HRUs, 

and computing initial index-model parameters for gaged 

watersheds. PRMS parameters of the index models were used 

in building the preliminary models for the ungaged perennial 

and ephemeral watersheds. While the HRU-dependent 

parameters were determined and computed for watershedspecific areas, the non-HRU dependent parameters were 

initially derived using the index model then transferred to the 

models of the ungaged and ephemeral watersheds. Parameters 

of particular relevance are those used in the routing of water 

through the soil zones and the shallow subsurface reservoir, 

the ground-water flow coefficients, and most importantly, 

those used for simulating ground-water inflow to the basin-fill 

aquifers of Carson Valley.

 Index model parameters for the ungaged perennial 

watershed models were adjusted to closely match 

reconstructed runoff, whereas index model parameters were 

used without adjustment for the ephemeral watershed models, 

except for adjusting the precipitation correction factor, as 

discussed in the section, “Runoff and Climate Data.” The 

modeling and calibration periods were restricted by the lengths 

of the climate and runoff records.

Basin Characterization and Delineation of 

Hydrologic Response Units

Geographic Information System (GIS) software, the 

Weasel Toolbox (Viger and Leavesley, 2006: http://wwwbrr.

cr.usgs.gov/weasel/, accessed on November 1, 2005) was used 

to manage spatial data and to characterize model drainages 

and HRUs in terms of slope, aspect, altitude, vegetationcover densities and types, and soil types and depths. Analyses 

of these characteristics provided estimates of spatially 

varying HRU-specific model parameters. Initial global 

model parameters, whose values apply over the entire basin, 

were quantified from PRMS parameter values for similar 

watershed studies in the region (Jeton and others, 1996; 

Jeton, 1999a and 1999b). The gaged and ungaged perennial 

watersheds are hydrographically defined basins, defined as 

land areas that drain to a downstream point, whereas the 

ephemeral watersheds are aggregated areas whose boundaries 

were arbitrarily defined outside of the Weasel Toolbox, and 

imported for use in HRU delineation.

Description of Watershed Models 15
A 10-meter digital elevation model (DEM) was used 

as the basis for computing the watershed boundary (U.S. 

Geological Survey, 1999). Other digital data include 

slope and aspect (derived from the 10-meter DEM), soils 

[1:250,000 State Soil Geographic (STATSGO) database; 

(U.S. Department of Agriculture, 1991)], and land cover for 

computing vegetation type and canopy density.

Preliminary HRUs were delineated as subbasin areas 

with more emphasis on hydrography than on other physical 

characteristics. These HRUs were further subdivided by 

altitude resulting in the final physiographic delineation of the 

HRUs. The final digital HRU data layer was intersected with 

measurements of altitude, slope, aspect, vegetation, and soils 

and averaged values were assigned to each HRU.

Figure 7 shows an example of HRU delineation and the 

distribution of slope, aspect, land cover, and land-surface 

altitude zones in the Daggett Creek watershed. The GISderived parameters are “static,” meaning they are simulated 

as constant through time and are not adjusted during model 

calibration. Typically, watershed models are run using several 

years of daily climate data as model input and land cover and 

density are assumed to be constant over time. In the present 

study, however, vegetation-cover type and canopy density for 

the western and eastern sides of Carson Valley have undergone 

some changes attributed to recent wildfires. The vegetation 

data reflect conditions from 1998 to 2000, as mapped in the 

digital land-cover data sets, with some modifications made to 

the land cover for the eastern side of Carson Valley.

For the present study, the altitude (DEM) dataset was reclassified into 1,000-foot altitude bands and used to restrict the 

altitude range within a single HRU to about 1,000 ft (fig. 7D). 

Point precipitation and temperature measurements from 

climate stations at lower or higher altitudes than the HRUs 

were distributed to the HRU using orographic corrections 

based on the mean HRU altitude. Restricting the range in 

altitude within a single HRU decreases the magnitude of the 

orographic corrections.

Digital land-cover data for the Carson Range was 

obtained from the U.S. Forest Service (Kathy Braton, U.S. 

Forest Service, Carson City, Nevada, written commun., 2006). 

These data are a modified version of the 1:24,000 Toiyabe 

National Forest vegetation layer (http://www.fs.fed.us/r5/rsl/

clearinghouse/sec-gbasin.shtml), which was mapped using 

imagery from 2000 (Ralph Warbington, U.S. Forest Service, 

Remote Sensing Laboratory, oral commun., 2006). For the 

Pine Nut Mountains, land cover was derived from the 30-

meter resolution Southwest Regional Gap Analysis Program 

(GAP) data (Kepler and others, 2005) for vegetation type and 

density as mapped between 1998 and 2000. Canopy densities 

from the Southwest Regional GAP data appeared to be too 

high based on visual inspection, and arbitrary adjustments 

were made to lower the density for shrub and pinion-juniper 

woodlands. HRU vegetation densities primarily affect 

simulated snowmelt and runoff timing rather than overall 

runoff volume. Accurate simulation of runoff timing was 

less of a concern in the present study, however, because the 

water-budget components were aggregated to annual and mean 

annual values for comparison with estimates of Maurer and 

Berger (2007).

Runoff and Climate Data

Daily mean runoff is available for model calibration 

for 4 gaged perennial watersheds (watersheds 5g and 

12g–14g; fig. 3 and table 2) and 10 ungaged perennial 

watersheds (watersheds 1u–4u and 6u–11u; fig. 3) in 

the Carson Range. Daily mean runoff for the ungaged 

watersheds was estimated by Maurer and others (2004, p. 8) 

using multivariate regressions of more than 400 individual 

discharge measurements against selected continuously gaged 

streams in and near Carson Valley. In the remainder of this 

report, the term “reconstructed” runoff is used for the runoff 

statistically generated to distinguish the estimates from other 

estimated runoff values. The term “measured” runoff is used 

for measured or continuously gaged runoff, and “simulated” 

runoff is defined as runoff simulated by the watershed models. 

The reconstructed daily mean runoff was estimated by Maurer 

and others (2004, p. 17) to have an uncertainty of about 

30 percent, and measured daily mean runoff of the gaged 

watersheds was estimated to have an uncertainty of about 15 

percent.

Climate input-data requirements for PRMS are daily 

total precipitation and daily maximum and minimum air 

temperature. Daily precipitation from six stations in and near 

Carson Valley (stations 1p–6p; table 2, fig. 3) was used to 

determine daily precipitation for each HRU in each watershed 

model. The stations used for each watershed model initially 

were selected by their proximity to the watershed and the 

altitude distribution within the watershed. For the Carson 

Range, high-altitude climate data were limited to climate 

stations at Daggett Pass (station 2p at 7,330 ft) and Heavenly 

Valley (station 3p at 8,582 ft). PRMS simulations using the 

Minden climate station (station 5p at 4,709 ft), located on the 

valley floor east of the Carson Range, tended to underestimate 

precipitation, underscoring the rainshadow effect of the Carson 

Range. Simulations using Sheridan Acres climate station 

(station 4p at 4,774 ft), located near the base of the Carson 

Range, appeared more suitable for estimating precipitation for 

HRUs with altitudes lower than 7,000 ft.

For the eastern side of Carson Valley, daily precipitation 

data were limited to Fish Springs, at an altitude of 5,120 ft 

(station 6p, table 2, fig. 3). Mean annual precipitation for 

Fish Springs averaged 7.7 in. during 1991–2002. Two storage 

gaging stations, Lower and Upper Pine Nut Mountains 

at altitudes of 6,440 ft and 7,201 ft in the Pine Nut Creek 

watershed, recorded annual precipitation of 13.6 and 15.2 in., 

respectively, for 1984–2002 (Maurer and Halford, 2004, 

p. 26). Annual averages for the storage gaging stations were 

used to compare simulated precipitation estimates for the 

1981–97 modeling period.

16 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Figure 7. HRU delineation and distribution of slope, aspect, land cover, and land-surface altitude zones in the Daggett Creek 

watershed, Carson Valley, Nevada.

nv19-4131_Fig07a

7

9

6

26

14

8

2

22

21

15

3

5

18

4

29

25

23

1

28

17

13

10

11

24

16

20

27

12

30

19

22

500 1,000 1,500 2,000 2,500 METERS

0

0

1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 FEET

Carson Valley

study area

Daggett Creek

watershed

EXPLANATION

Daggett Creek hydrologic 

 response unit (HRU) and No. 

5–15

15–35

35–45

45–65

65–95

Slope of surface, in percent

Boundary of watershed

A. Slope

Description of Watershed Models 17
Figure 7.—Continued.

nv19-4131_Fig07b

7

9

6

26

14

8

2

22

21

15

3 5

18

4

29

25

23

1

28

17

13

10

11

24

16

20

27

12

30

19

EXPLANATION

Drainage aspect, in degrees

Boundary of watershed

0 (N)

0–45 (NE)

45–90 (E)

90–135 (SE)

135–180 (S)

180–225 (SW)

225–270 (W)

270–360 (NW)

22 Daggett Creek hydrologic 

 response unit (HRU) and No. 

500 1,000 1,500 2,000 2,500 METERS

0

0

1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 FEET

Carson Valley

study area

Daggett Creek

watershed

B. Aspect

18 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
nv19-4131_Fig07c

7

9

6

26

14

8

2

22

21

15

3

5

18

4

29

25

23

1

28

17

13

10

11

24

16

20

27

12

30

19

EXPLANATION

Barren

Conifer

Hardwood

Herbaceous

Shrub

Urban or roads

Open water

U.S. Forest Service Toiyabe 

 National Forest land cover

Boundary of watershed

22 Daggett Creek hydrologic 

 response unit (HRU) and No. 

C. Land cover 500 1,000 1,500 2,000 2,500 METERS

0

0

1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 FEET

Carson Valley

study area

Daggett Creek

watershed

Figure 7.—Continued.

Description of Watershed Models 19
nv19-4131CarsonCity_Fig07d_elevation

500 1,000 1,500 2,000 2,500 METERS

0

0

1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 FEET

EXPLANATION

5–6,000 

6–7,000

7–8,000

8–9,000

9–10,000

Altitude, in feet

Boundary of watershed

22 Daggett Creek hydrologic 

 response unit (HRU) and No. 

Carson Valley

study area

Daggett Creek

watershed

7

9

6

26

14

8

2

22

21

15

3

5

18

4

29

25

23

1

28

17

13

10

11

24

16

20

27

12

30

19

D. Land-surface altitude zones

Figure 7.—Continued.

20 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Table 2. Precipitation and streamflow-gaging stations, period of 

record, and altitude, Carson Valley, Nevada and California. 

[Watershed No.: “g” is gaged station; “p” is precipitation station. Station 

locations are shown in figure 3. Altitude: Datum is North American Vertical 

Datum of 1988. Abbreviations: USGS, U.S. Geological Survey]

Watershed 

No. 

Station name 

(site identifier)

Period of record

(water years)

Altitude

(feet)

Precipitation stations1

1p Carson City 1893–2006 4,750

2p Daggett Pass 1971–2006 7,330

3p Heavenly Valley 1970–2006 8,582

4p Sheridan Acres 1992–2006 4,774

5p Minden 1928–2006 4,709

6p Fish Springs 1991–2002 5,120

USGS streamflow-gaging stations2

5g Daggett Creek 

near Genoa, NV 

(10310400)

1965–83 

1988–2006

5,100

12g Fredericksburg 

Canyon Creek near 

Fredericksburg, 

CA (10310300)

1989–2001 5,520

13g Pine Nut Creek near 

Gardnerville, NV 

(10309050)

1981–97 6,340

14g Buckeye Creek 

near Minden, NV 

(19309070)

1981–97 5,640

1 For location details, see Maurer and Halford (2004, p. 26).

2 For location details, see Maurer and others (2004, p. 7).

for the watersheds using the linear relations of Maurer and 

Halford (2004) for 1971–2000. This was done to assure that 

the precipitation input to watershed models was consistent 

with that used previously for estimating ground-water inflow 

to Carson Valley. Maurer and others (2004, p. 15) reported that 

mean annual precipitation for 1990–2002 was similar to that 

for 1971–2000 at Minden, 8.45 and 8.38 in/yr, respectively, 

and at Heavenly Valley, near the crest of the Carson Range, 

33.3 and 32.9 in/yr, respectively.

Precipitation was estimated by Maurer and Halford 

(2004) using two linear relations between precipitation and 

altitude, one for the western side and one for the eastern 

side of Carson Valley, based on data from 14 stations in and 

near Carson Valley. An areal distribution of precipitation 

was estimated by applying these relations to a DEM of the 

study area (Maurer and Halford, 2004, p. 28). In this study, 

the resulting gridded data set was combined with HRU areas 

for each modeled watershed and the precipitation estimates 

of Maurer and Halford (2004) were used to adjust the HRU 

precipitation correction.

Model Sensitivity

Sensitivity analyses during model calibration typically 

help to determine the extent to which parameter-value 

uncertainties result in acceptable runoff predictions. Although 

this modeling study was focused on estimating ground-water 

inflow, the hydrologic data to which the watershed model is 

calibrated is runoff, with ground-water inflow simulated as 

water in the ground-water reservoir in excess of what reaches 

the stream channel as baseflow.

The model sensitivities to PRMS parameter values for 

the present study can be understood from previous watershed 

modeling studies in the East Fork Carson River basin (Jeton 

and others, 1996), the Lake Tahoe basin (Jeton, 1999a), and 

the catchment area of the Truckee River (Jeton, 1999b). The 

hydroclimatic setting of these earlier studies is similar to that 

of the watersheds in the present study area with appropriate 

adjustments made for precipitation distribution. Previous 

studies of similar watersheds list the parameters modified 

during calibration (for example, Jeton, 1999b, p. 17).

Sensitivity analyses show that runoff simulations are 

most sensitive to the (1) snow threshold temperature that 

determines precipitation form, (2) precipitation-correction 

factor for snow and rain (similar to a precipitation lapse rate 

where the measured precipitation is adjusted for differences 

in altitude between the climate station and the HRU), 

(3) monthly temperature lapse rates (typically between 3.5 

and 4.5°F for every 1,000 ft), (4) monthly evapotranspiration 

coefficients for the Jensen-Haise potential-evapotranspiration 

computation (Jensen and Haise, 1963), and (5) coefficient for 

transmission of solar radiation through winter plant canopies 

to snow surface, which affects snowmelt timing.

Initial PRMS model simulations in this study used 

an HRU precipitation correction factor that increased 

precipitation 15–20 percent for each 1,000 ft of altitude 

gain above the valley floor. This initial correction factor was 

derived from local lapse rates calculated using low- and highaltitude precipitation stations and differences in mean HRU 

altitude. Maximum and minimum daily temperatures were 

adjusted in the PRMS model with an altitude correction factor 

of 3.5°F of cooling for every 1,000 ft of altitude gain, which 

corresponds to regional temperature lapse rates used in similar 

watershed modeling studies.

Additional adjustments of simulated precipitation were 

made during model calibration, so that simulated mean 

annual precipitation was similar to previous mean annual 

precipitation estimated by Maurer and Berger (2007, p. 29) 

Description of Watershed Models 21
The watershed models also were sensitive to soil moisture 

storage, and the flow-routing coefficients for interflow and 

ground-water reservoirs used to simulate ground-water inflow. 

Parameters that determine flows to and from the groundwater reservoirs were adjusted to fit the observed shapes of 

the seasonal recession of runoff. Interflow influences the 

quicker response seen as spikes in the hydrograph in response 

to snowmelt or rain events and exhibits a short lag in timing. 

Overland runoff from the rock outcrop or otherwise barren, 

more impervious areas, reflects a near instantaneous runoff 

response.

Model Calibration

Calibration of PRMS models is an iterative process 

where, after each adjustment of model parameters, simulated 

runoff is visually and statistically compared with measured or 

reconstructed runoff, with special attention paid to matching 

flow volumes for seasonal and annual time periods, and runoff 

timing for large events. Ground-water inflow is a component 

that is not measured but modeled as a residual component 

of the water budget. If the dominant gains to the system 

(precipitation) and losses (evapotranspiration) are adequately 

modeled, and the simulated hydrograph matches the 

measured hydrograph overall, water in excess of that which 

reaches the stream channel can be considered as an adequate 

representation of ground-water inflow. The simulations are 

run on a daily time step; however, ground-water inflow is 

evaluated on a mean annual basis to allow for comparison 

to previously derived estimates. Seasonal and annual waterbudget components derived from the models were of most 

interest and the detailed timing of runoff and ground-water 

inflow was not crucial.

Effort was made during calibration to provide the best 

fit to measured or reconstructed runoff during wet years 

from 1993 to 1998 for watersheds in the Carson Range, and 

1982–83 and 1986 for Pine Nut and Buckeye Creeks (fig. 4). 

This was done because initial watershed modeling showed that 

ground-water inflow was greatest or occurred primarily during 

wet years.

For comparison with previous water-budget estimates, 

and because reconstructed runoff was available for ungaged 

watersheds for the same time period, a calibration period of 

water years 1990–2002 was selected for watershed models of 

the Carson Range. For Pine Nut Creek and Buckeye Creek 

watershed models, a calibration period of water years 1981–97 

was selected, because it coincides with the period of record of 

measured runoff for the streams (table 2). Simulations of the 

Pine Nut Creek and Buckeye Creek watersheds were extended 

to include water years 1998–2002 using the models developed 

for the 1981–97 calibration period. To provide simulation 

results for the same period as the Carson Range models, Pine 

Nut and Buckeye Creek models were run for the 1990–2002 

period.

Error Analysis

No single calibration of a PRMS model will simulate all 

runoff regimes with equal accuracy. The goal in modeling is 

threefold: (1) little to no bias, (2) small simulation error, and 

(3) realistic parameter values reflecting the conditions being 

modeled. The goals for calibration are to maintain a good 

visual fit between the simulated and measured hydrographs, 

to keep mean annual biases to within 5 percent, and to keep 

relative error to within 10 percent. In watershed modeling, 

common measures of simulation error include the sum of 

errors and bias. Bias is computed to determine the presence of 

systematic error or an indication of central tendency (that is, 

whether the simulations show a tendency towards under- or 

overestimating with respect to the measured runoff). Absolute 

errors (defined as the difference between simulated and 

measured runoff) tend to be dominated by a few large events 

(Haan and others, 1982), unless normalized by the measured 

values to form “relative error,” as used in this report. The 

un-normalized root mean square error (RMSE) provides a 

common measure of the magnitude of simulation errors that 

complements the relative measures provided by the bias and 

relative errors.

Normalizing runoff error by dividing it by the measured 

value presents a problem when the extremely low flows result 

in very large relative errors even though the absolute error 

may be small (Haan and others, 1982). Though much of the 

measured runoff of Carson Range watersheds represents 

low flows, no runoff data for these watersheds were omitted 

in the error analysis primarily to allow for comparisons 

between reconstructed and measured runoff. For the east 

side watersheds, the Buckeye Creek gaging record indicates 

numerous days with zero flows, possibly due to poor site 

location of the gaging station downstream of a losing reach, 

and the Pine Nut Creek simulations resulted in months with 

zero flow. For this reason, only months with non-zero flows 

were included in the error analysis.

Model calibration biases, relative errors, and RMSEs 

for the four watershed models of gaged watersheds are 

given in table 3. Error statistics were not calculated for 

models calibrated using reconstructed runoff because of the 

considerable uncertainty associated with the reconstructed 

daily mean runoff. The error statistics are presented as 

seasonal, mean monthly, and mean annual summaries for 

the simulation period, with the exception of Buckeye Creek 

watershed model. For Buckeye Creek, error statistics are 

presented only for February–April due to the prevalence of 

zero runoff in the measured record during other times of the 

year. For the remaining watershed models, monthly error 

statistics were computed for four seasons; October–December, 

January–March, April–June, and July–September. Each of 

these seasons represents a particular hydroclimatic regime 

with October–December characterized by early winter rain, 

snow, and mixed rain and snow events, and July–September 

22 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
characterized by low-flow conditions and occasional summer 

convective storms. January–March are characterized by winter 

snow and occasional rain-on-snow events, and the spring 

runoff season; April–June tends to produce the most water 

available for ground-water inflow to basin-fill deposits of 

Carson Valley. Lastly, the term “runoff efficiency” is used to 

compare the percentage of precipitation that becomes runoff, 

which indirectly is a measure of losses to evapotranspiration 

and infiltration. Runoff efficiencies were simulated for 

the 1990–2002 period of record and compared to previous 

estimates.

Carson Range Perennial Watersheds

Daily mean runoff simulated by the models and measured 

for the Daggett Creek and Fredericksburg Canyon watersheds 

provides the best fit for wet years (fig. 8). The hydrographs 

show a distinct increase in baseflow in 1995 and 1996 with 

another, smaller increase in 1997. The increase in 1997 is the 

result of a very heavy snow accumulation and melt period in 

early 1997. Wet conditions continue into 1998 before returning 

to dry conditions for the remaining years of the modeling 

period.

Daggett Creek Watershed

With the exception of April–June, calibration statistics 

for the Daggett Creek model are satisfactory for seasonal, 

monthly, and annual time scales (table 3). Simulated mean 

monthly and mean annual runoff show a tendency to slightly 

underestimate runoff with low associated errors, and a 

mean annual RMSE of 1.1 in. Based on visual inspection, a 

satisfactory overall fit was obtained between simulated and 

measured daily mean runoff for Daggett Creek for the 1993–

98 period of high runoff (fig. 8).

The pattern of simulating, on average, an earlier than 

recorded spring runoff (fig. 8), particularly evident for water 

years 1995–2000 results in an overestimation of runoff for 

January–March and a subsequent underestimation of runoff for 

April–June (table 3). This may be due to cooler temperatures 

than were modeled resulting in a later measured spring runoff. 

Comparisons of measured and simulated annual mean runoff 

and ground-water inflow are illustrated in figure 9. Overall, 

the Daggett Creek model under-estimates annual runoff for 

dry (or below normal) years and overestimates runoff for wet 

years. The mean annual runoff efficiency using the simulated 

runoff was 20 percent, comparable to the efficiency calculated 

with the measured flow (table 1).

Table 3. Calibration statistics for PRMS watershed models of gaged watersheds of the Carson Range and Pine Nut Mountains, Carson 

Valley, Nevada and California.

[Bias = ∑(simulated–measured)/∑(measured)*100. Relative error = ∑((simulated–measured)/measured)*100/number of measurements. RMSE is root mean 

square error–SQRT(∑(simulated–measured)2/number of measurements. –, not calculated because of zero flow for many days]

Season Bias

(percent)

Relative error

(percent)

RMSE 

(inches) Season Bias(percent)

Relative error

(percent)

RMSE 

(inches)

Daggett Creek

(water years 1990–2002)

Fredericksburg Canyon

(water years 1990–2001)

October–December -5.4 -8.7 0.1 October–December 6.7 4.8 0.2

January–March 7.6 2.9 0.2 January–March 2.4 7.8 0.3

April–June -14.0 -7.8 0.2 April–June 18.6 27.0 0.4

July–September -1.5 1.4 0.1 July–September -2.3 13.1 0.3

Period of record 

mean monthly

-3.7 -2.7 0.2 Period of record 

mean monthly

3.7 14.6 0.4

Period of record 

mean annual

-3.7 5.6 1.1 Period of record 

mean annual

3.7 12.0 6.0

Pine Nut Creek

(water years 1981–97)1

 Buckeye Creek

(water years 1981–97)

October–December -72.0 -70.0 0.1 February–April -12.3 5.0 0.1

January–March 16.9 3.8 0.2 – – – –

April–June 6.0 21.8 0.1 – – – –

July–September 40.0 8.5 0.0 – – – –

Period of record 

mean monthly

-5.4 -9.7 0.2 – – – –

Period of record 

mean annual

-15.0 -11.0 1.0 Period of record 

mean annual2

7.7 -5.4 0.0

1 Calculated for months with non-zero simulation results.

2 Calculated with water year 1994 removed.

Description of Watershed Models 23
nv19-4131_Fig08

Daggett Creek—watershed 5g 

0.1

1

10

100

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Measured

Simulated

Fredericksburg Creek—watershed 12g

DAILY MEAN RUNOFF, IN CUBIC FEET PER SECOND

0.1

1

10

100

Figure 8. Simulated and measured daily mean runoff for Daggett Creek and Fredericksburg Canyon watersheds, Carson 

Valley, Nevada and California, water years 1990–2002.

24 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
nv19-4131_Fig09a

Daggett Creek—watershed 5g 

5

0

10

15

5

0

10

15

20

25

30

Fredericksburg Creek—watershed 12g

ANNUAL MEAN RUNOFF, AND INFLOW, IN INCHES

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Measured runoff

Ground-water inflow

Simulated runoff

Figure 9. Simulated and measured annual mean runoff and ground-water inflow for Daggett Creek, water years 1990–2002, 

Fredericksburg Canyon, water years 1990–2001, and Pine Nut Creek and Buckeye Creek watersheds, water years 1981–97, 

Carson Valley, Nevada and California.

Description of Watershed Models 25
nv19-4131_Fig09b

Pine Nut Creek—watershed 13g 9

8

7

6

5

4

3

2

1

0

10

Measured runoff

Ground-water inflow

Simulated runoff

Buckeye Creek—watershed 14g

ANNUAL MEAN RUNOFF AND INFLOW, IN INCHES

9

8

7

6

5

4

3

2

1

0

10

1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997

Figure 9.—Continued.

26 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Fredericksburg Canyon Watershed

Mean monthly and mean annual statistics for the 

Fredericks Canyon model (table 3) indicate a slight bias to 

overestimate runoff. Mean monthly and mean annual relative 

errors were about 15 and 12 percent, respectively, and mean 

annual RMSE was 6 in. For April–June, the bias and relative 

error are large and indicate a tendency to overestimate runoff 

during this period. Statistics for the other seasonal aggregates 

(table 3) indicate an adequate fit between simulated and 

measured values.

The simulated and measured runoff indicate that spring 

runoff in general and the baseflow recession for 1993 and 

1995–97 match well (fig. 8), but annual runoff for 1998–99 

is overestimated. For the drier years (water years 1990–92 

and 1994), baseflow and annual runoff are overestimated. 

Beginning in 1993, precipitation appears to have recharged 

subsurface storage sufficiently to increase baseflow for 

subsequent years, only returning to baseflow conditions 

similar to 1990 by water year 2001 (fig. 8). For 1997, the 

measured snowmelt recession curve shows an erratic response 

(fig. 8), possibly attributed to poor data. Runoff for most days 

of the year is less than 2 ft3/s for dry years and increases to 

more than 10 ft3/s only during spring runoff for wet years 

(fig. 8).

The recorded January 1997 flood peak for Fredericksburg 

Canyon of 5,000 ft3/s (Bonner and others, 1998, p. 152) 

is considered to be highly unlikely when compared to the 

same flood peaks in other Carson Range watersheds (Mike 

Nolan, U.S. Geological Survey, oral commun., 2006). For 

this study, the January 1997 peak was therefore arbitrarily 

adjusted to 100 ft3/s (rather than omitted), to not unduly skew 

the statistical analyses. Measured runoff for January–May 

1997 has numerous days when the runoff had been estimated 

(Bonner and others, 1998, p. 152) and overall the record 

for this water year is rated as poor. The runoff efficiency 

calculated for the 1990–2001 period is 45 percent, comparable 

to that calculated using measured runoff (table 1).

Pine Nut Mountains Perennial Watersheds

The period of record of the runoff used for calibration 

of the Pine Nut Creek and Buckeye Creek watersheds differs 

from the Carson Range watersheds, and represents an earlier 

period from water years 1981–97. Both the Buckeye Creek 

and Pine Nut Creek watershed models used a combination of 

precipitation data from the Minden station for 1981–91, and 

the Fish Springs station for 1992–2002 as input data.

There is considerably more uncertainty associated 

with the watershed models on the eastern side than with 

those on the western side for the following reasons: (1) 

the Pine Nut Mountains are subjected to more convective 

storm activity and without local precipitation data (Minden 

and Fish Springs stations may be too far from the modeled 

drainages to accurately estimate their precipitation), and 

lacking high-altitude data, the models may not adequately 

simulate the spatial and temporal distribution of precipitation; 

(2) the model-input precipitation time series is based on a 

combination of two stations (Minden and Fish Spring climate 

stations) that have different periods of record and slightly 

different altitudes but the model applies the same precipitation 

adjustments to each station record; (3) the Buckeye Creek 

watershed may be too large to fit the assumption that runoff 

and subsurface flow reach the stream channel within a daily 

time step; and (4) there is uncertainty about the soil-water 

holding capacity, which affects simulated evapotranspiration, 

runoff, and ground-water inflow to basin-fill aquifers of 

Carson Valley.

Pine Nut Creek Watershed

Mean monthly and mean annual bias and relative error 

are large in the Pine Nut Creek watershed model, and indicate 

systematic underestimations for mean annual and mean 

monthly runoff, though less so for the latter. As illustrated in 

figure 10, the model underestimates annual runoff for all years 

with the exception of 1982 and 1993 and wet years from 1995 

to 1997.

Precipitation volumes for the Pine Nut Creek model were 

not adjusted to exactly match the 1971–2000 mean annual 

precipitation volumes determined by Maurer and Berger 

(2007, p. 29; table 4), which estimated a mean annual rate of 

16 in., resulting in excessive simulated runoff. Precipitation 

amounts were decreased to better match the mean annual 

precipitation of about 14 in. at the Lower Pine Nut storage 

gage (Maurer and Halford, 2004, p. 26). Simulating runoff 

using the adjusted precipitation amounts improved runoff 

comparisons for the currently underestimated dry years, yet 

for the wet years particularly 1993, and 1995–97, the modeloverestimated runoff resulted in a relative error ranging 

from 19 percent in 1997 to more than 100 percent in 1993 

(fig. 10). Overall, the model underestimates runoff for the 

dry years when runoff typically was less than 2 ft3/s. The 

runoff efficiency for the model estimates is about 2 percent as 

compared to the 8 percent computed by Maurer and Berger 

(2007, p. 29).

Description of Watershed Models 27
Simulated

Measured

90

80

70

60

50

40

30

20

10

0

100

A. Pine Nut Creek—w atershed 13g

1980 1983 1985 1987 1984 1986 1988 1989 1990 1992 1994 1996 1991 1993 1995 1997

15

5

20

10

0 19821981

DAILY MEAN RUNOFF, IN CUBIC FEET PER SECOND

5X vertical exaggeration

nv19-4131_Fig10a

Figure 10. Simulated and measured daily mean runoff for Pine Nut Creek and Buckeye Creek watersheds, Carson Valley, 

Nevada, water years 1981–97.

28 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
nv19-4131_Fig10b

Simulated

Measured

90

80

70

60

50

40

30

20

10

0

100

DAILY MEAN RUNOFF, IN CUBIC FEET PER SECOND

1980 1983 1985 1987 1984 1986 1988 1989 1990 1992 1994 1996 1991 1993 1995 1997

15

5

20

10

0 19821981

5X vertical exaggeration

B. Buckeye Creek—watershed 14g

ft

Figure 10.—Continued.

Description of Watershed Models 29
Table 4. Summary of model results for 14 perennial watersheds in Carson Valley, water years 1990–2002, and comparison with estimates from Maurer and Berger (2007). 

[Values in inches are volumes in acre-feet, divided by watershed area, in acres, multiplied by 12. Watershed No. ending in “u” is ungaged; watershed No. ending in “g’ is gaged watershed. Locations of watersheds are shown in figure 3. Measured or reconstructed mean annual runoff: From Maurer and others (2004, p. 14); measured for gaged watersheds; reconstructed for ungaged watersheds. Relative difference in runoff: Computed from values in acre-feet as (simulated−estimated/estimated)*100. Estimated mean annual precipitation: From Maurer and Berger (2007, p. 29). Estimated mean annual ET: Multiply reported ET rate, in feet, by watershed area to obtain ET volume in acre-feet. Estimated mean annual ground-water inflow: From Maurer and Berger (2007, p. 32). Ground-water inflow: Defined as ground-water inflow to basin-fill aquifers of Carson Valley. Abbreviations: acre-ft, acre-feet; ET, evapotranspiration]

Watershed 

No.

Watershed 

name

Drainage 

area, 

(acres, 

rounded)

Mean annual precipitation

Relative 

difference in 

precipitation 

estimates

(percent)

Mean annual runoff

Relative 

difference 

in runoff

(percent)

Mean annual ET Mean annual ground-water inflow

Estimated

by Maurer and 

Berger, 2007 

1971–2000

Simulated by 

watershed 

models

1990–2002

Measured or 

reconstructed by 

Maurer and 

others, 2004 

1990–2002

Simulated by 

watershed 

models,

1990–2002

Estimated by 

Maurer and 

Berger, 2007

Simulated by 

watershed 

models, 

1990–2002

Estimated by 

Maurer and 

Berger, 2007

Simulated by 

watershed 

models, 

1990–2002

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

1u Water Canyon 1,700 4,200 4,200 0 1,900 2,100 11 2,400 1,900 0 100

(30) (30) (13) (15) (17) (14) (9) (0.9)

2u James Canyon 1,300 3,400 3,300 -3 1,300 1,300 0 2,100 1,700 60 200

(31) (30) (12) (12) (19) (16) (0.6) (2.2)

3u Sierra Canyon 2,000 4,900 4,900 0 1,500 1,400 -7 3,200 2,800 200 600

(29) (29) (9.0) (8.4) (19) (17) (1.2) (3.5)

4u Genoa Canyon 1,400 3,200 3,000 -6 960 1,000 4 2,100 1,700 80 400

(27) (26) (8.2) (8.6) (18) (15) (3.5) (3.1)

5g Daggett Creek 2,400 5,600 5,700 2 1,200 1,100 -8 3,600 3,000 700 1,600

(28) (29) (6.0) (5.5) (18) (15) (3.5) (7.9)

6u Mott Canyon 1,300 3,300 3,400 3 1,700 1,600 -6 1,600 1,600 0 0

(30) (31) (15) (15) (14) (14) (0) (0)

7u Monument Creek 1,500 3,500 3,600 3 2,600 1,800 -31 900 1,800 0 0

(28) (29) (21) (14) (7) (14) (0) (0)

8u Stutler Canyon 1,600 4,000 4,000 0 450 450 0 23,500

(19)

1,900 2100

(0.5)

11,600/1,000

(30) (30) (3.4) (3.4) (14) (12.3)

9u Sheridan Creek 640 1,400 1,400 0 1,300 700 -46 660 0

(26) (26) (24) (13) (12) (0)

10u Jobs Canyon 2,000 5,500 5,500 0 1,700 2,000 18 3,200 2,800 700 800

(33) (33) (10) (12) (19) (17) (1.3) (4.7)

11u Luther Creek 2,800 7,200 7,200 0 2,200 2,100 -5 4,500 4,100 500 1,200

(31) (31) (9.4) (9) (19) (18) (2.1) (5.3)

12g Fredericksburg Canyon 2,400 6,400 6,700 5 2,900 3,000 3 3,800 3,300 0 300

(32) (34) (14) (15) (19) (17) (0) (1.6)

Subtotal, Carson Range3 21,000 52,600 52,900 0 19,700 18,600 -6 30,200 27,300 2,300 46,200

(30) (30) (11) (11) (19) (16) (1.3) (3.5)

30 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Watershed 

No.

Watershed 

name

Drainage 

area, 

(acres, 

rounded)

Mean annual precipitation

Relative 

difference in 

precipitation 

estimates

(percent)

Mean annual runoff

Relative 

difference 

in runoff

(percent)

Mean annual ET Mean annual ground-water inflow

Estimated

by Maurer and 

Berger, 2007 

1971–2000

Simulated by 

watershed 

models

1990–2002

Measured or 

reconstructed by 

Maurer and 

others, 2004 

1990–2002

Simulated by 

watershed 

models,

1990–2002

Estimated by 

Maurer and 

Berger, 2007

Simulated by 

watershed 

models, 

1990–2002

Estimated by 

Maurer and 

Berger, 2007

Simulated by 

watershed 

models, 

1990–2002

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

13g Pine Nut Creek 6,400 8,500 7,200 -15 670 690 3 7,000 5,200 700 1,200

(16) (14) (1.3) (1.3) (13) (10) (1.3) (2.3)

14g Buckeye Creek 28,900 34,000 33,000 -3 690 700 1 29,000 25,000 3,600 7,000

(14) (14) (0.2) (0.3) (12) (10) (1.5) (2.9)

 Subtotal, Pine Nut Mountains3 35,300 42,500 40,200 -5 1,360 1,390 2 36,700 30,100 4,300 8,200

(14) (14) (0.5) (0.5) (12) (10) (1.5) (2.8)

Total (rounded) 56,300 95,100 93,100 3-2 21,000 20,000 3-5 66,900 57,400 6,600 14,400

(20) (20) (4.5) (4.3) (14) (12) (1.4) (3.2)

1 About 600 acre-ft from Stutler Canyon is assumed to supply streamflow to Sheridan Creek, and is not available as ground-water inflow to basin-fill aquifers of Carson Valley. Remaining 1,000 acre-ft 

assumed to supply ground-water inflow to basin-fill aquifers of Carson Valley.

2 Estimates from Maurer and Berger (2007) are for the combined watersheds of Stutler Canyon and Sheridan Creeks.3 Values of relative difference for subtotal and total are actually average values, rather than subtotals.4 Includes 1,000 acre-ft from Stutler Canyon.

Table 4. Summary of model results for 14 perennial watersheds in Carson Valley, water years 1990–2002, and comparison with estimates from Maurer and Berger (2007)—Continued. [Values in inches are volumes in acre-feet, divided by watershed area, in acres, multiplied by 12. Watershed No. ending in “u” is ungaged; watershed No. ending in “g’ is gaged watershed. Locations of watersheds are shown in figure 3. Measured or reconstructed mean annual runoff: From Maurer and others (2004, p. 14); measured for gaged watersheds; reconstructed for ungaged watersheds. Relative difference in runoff: Computed from values in acre-feet as (simulated−estimated/estimated)*100. Estimated mean annual precipitation: From Maurer and Berger (2007, p. 29). Estimated mean annual ET: Multiply reported ET rate, in feet, by watershed area to obtain ET volume in acre-feet. Estimated mean annual ground-water inflow: From Maurer and Berger (2007, p. 32). Ground-water inflow: Defined as ground-water inflow to basin-fill aquifers of Carson Valley. Abbreviations: acre-ft, acre-feet; ET, evapotranspiration]

Description of Watershed Models 31
As with all other watershed models presented in this 

study, the PRMS method for computing ground-water inflow 

affects the baseflow period for the dry years in a more 

pronounced manner when adjusting ground-water inflow 

to minimize overestimation of runoff during the wet years. 

This resulted in days with zero simulated runoff for the Pine 

Nut Creek model. Due to the use of a normalized error, only 

months with non-zero simulated runoff were included in the 

seasonal error analyses. The only seasonal aggregate with a 

reasonable bias is April–June. The tendency however, is to 

overestimate spring runoff during the wet years from water 

years 1995–97, resulting in an overall relative error of about 

22 percent for April–June.

Buckeye Creek Watershed

Although the Buckeye Creek watershed is considered to 

be a perennial watershed, records indicate periods of very low 

to zero runoff for much of the year, thus characterizing this 

watershed as more of an ephemeral- than perennial-stream 

watershed. The Buckeye Creek gaging station is downstream 

of a losing reach and has many days with zero flows except 

during the early spring snowmelt. For that reason, error 

statistics were computed for mean annual runoff, and the 

February–April aggregate, the latter for years with measured 

flow (table 3).

Overall, the simulated hydrograph indicates that the 

model simulates a much quicker response to precipitation 

than what is measured at the gage and it tends to overestimate 

mean annual runoff by as much as 12 percent relative to the 

measured runoff (fig. 10: table 3) However, for the February–

April period, the only season with consistently measured 

runoff greater than zero, seasonal simulations underestimate 

runoff. For water years 1981–97, mean annual relative error 

is 102 percent. However, removing water year 1994 from 

the analysis, when the annual difference in simulated and 

measured runoff exceeds 1,000 percent (0.046 in. simulated 

versus 0.003 in. measured), reduces the relative error to about 

-5 percent (table 3).

The ground-water inflow component of the water 

budget is greater than zero for those years with above normal 

precipitation (fig. 9). For wet years (1982–83, 1986, 1993, 

1995–97), ground-water inflow ranges from 20 percent of the 

precipitation in 1982 to more than 40 percent in 1997. The 

runoff efficiency for Buckeye Creek watershed is estimated 

to be 2 percent (table 1) indicating most of the precipitation is 

lost to evapotranspiration and infiltration.

Whether computed ground-water inflow from the 

Buckeye Creek watershed is reasonable depends primarily 

on the accuracy of the precipitation inputs. Simulated 

daily hydrographs for individual years with above normal 

precipitation (fig. 10) reasonably fit measured hydrographs for 

most of the winter to early spring runoff peaks, although there 

is a tendency for the model to underestimate March–April 

runoff. Conversely, during dry or below average precipitation 

years, not only is the runoff well below 1 ft3/s for every day 

during the year, but there are a larger number of measured 

summer runoff peaks that the model did not simulate.

Model and Data Limitations

The precipitation-runoff model is a mathematical 

representation of the physical processes that occur in the 

watershed. The quality of the model results depends on the 

accuracy of the representation of the physical processes 

(model error), the quality and accuracy of the precipitation and 

air-temperature input time series and runoff calibration time 

series (data error), and the accuracy of the calibrated model 

parameters (parameter error: van Heeswijk, 2006).

Those error sources most affecting the watershed 

models for Carson Valley include: the assumption that 

the ungaged perennial and ephemeral watersheds are 

hydrologically similar to the index watersheds, the scale of 

available soil data, the adequacy of available climate data and 

accuracy of precipitation estimates using the precipitation 

distribution of Maurer and Halford (2004), the accuracy of 

the reconstructed daily mean runoff used for calibration of 

the ungaged perennial watersheds, and the sensitivity of the 

model in simulating baseflow during years of below normal 

precipitation. Watersheds are dynamic systems. Land-cover 

type, density, and the percentage of impervious or barren 

areas are static parameters in PRMS, and therefore reflect land 

cover conditions for 1998–2000, when the digital maps were 

compiled.

The hydrologic similarity of ungaged watersheds to index 

watersheds cannot be further addressed without additional, 

definitive measurements of runoff from the ungaged 

watersheds. The effect of index model selection for ephemeral 

watersheds of the Carson Range is evaluated in the section, 

“Uncertainty in Estimates of Simulated Ground-Water Inflow.”

The scale of available soil data limits the extent to which 

the watershed models can represent the actual hydrologic 

system. The STATSGO soils data are mapped at a scale 

of 1:250,000, resulting in a 1,000-m grid resolution and a 

minimum mapping unit of 1,544 acres, an area larger than 

many of the modeled watersheds. Most of the Carson Range 

watersheds are characterized as having either one or two soil 

types, reflecting the dominance of granitic or metamorphic 

bedrock. Watersheds on the eastern side of Carson Valley have 

from four to five different soil types reflecting a more varied 

geologic landscape that includes crystalline volcanic rocks, 

Tertiary sediments, and alluvial-fan deposits.

The soil-water holding capacity was adjusted upward for 

most of the HRUs, reflecting an increase from 30 to more than 

100 percent of the initial value computed from the STATSGO 

data to better match the reconstructed or measured runoff. The 

soil parameters influence the distribution of water between 

32 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
the surface and subsurface reservoirs and ultimately affect the 

distribution of interflow or shallow subsurface flow, baseflow, 

and ground-water inflow. In addition, the amount of actual 

evapotranspiration (AET) is influenced by the generalized 

PRMS soil designation of sand, loam or clay (derived from 

STATSGO), and the ratio of available water to the maximum 

soil-water storage at a given simulation time step.

The dominance of one flow coefficient over the other 

influences the shape of the simulated hydrograph. The 

simulated ground-water inflow is set at a constant rate in the 

model for the selected modeling period. The constant rate 

affects low-runoff years more visibly than the above-average 

precipitation years. In low runoff years, less water is routed to 

the subsurface reservoirs and thus, less water is available for 

baseflow. This results in a tendency to underestimate baseflow 

for the drier years, when adjusting the model to better fit wet 

years. Though there can be remaining soil-moisture storage at 

the end of a simulated water year, this may be underestimated 

compared to the actual year-to-year subsurface storage. 

Propogated over several consecutively low precipitation 

years, the tendency to underestimate baseflow can potentially 

increase the modeling error for the period of record.

The rainshadow effect of the Carson Range influences 

precipitation in Carson Valley as much as altitude. The 

Sheridan Acres, Daggett Pass, and Heavenly Valley climate 

stations (stations 4p, 2p, and 3p in fig. 3, respectively) 

adequately represent the range in precipitation distribution 

for the Carson Range while the Minden station (station 5p) 

appears to be influenced by the Carson Range rainshadow 

effect. The Fish Spring station (station 6p) in the Pine Nut 

Creek drainage recorded data from 1991 to 2002. The Minden 

data were used to complete the earlier part of the record 

and used to model both Buckeye Creek and Pine Nut Creek 

watersheds. The Pine Nut Mountains are more influenced 

by localized, convective storm activity, which may not be 

adequately represented by the Minden or Fish Springs climate 

stations. There may be some error introduced at the scale of 

daily runoff simulations in the use of one low-altitude climate 

station in simulating air temperatures for the higher altitude 

HRUs, and the use of regional monthly temperature lapse rates 

to adjust for differences in HRU altitude.

Precipitation inputs were corrected to closely match 

the long-term precipitation estimates for each watershed 

determined by Maurer and Berger (2007, p. 29) using the 

linear relations developed by Maurer and Halford (2004) for 

1971–2000. Although the simulated mean annual volume of 

precipitation may correlate well with the previous estimates 

of Maurer and Berger (2007; table 4), there is uncertainty as 

to the interannual variability introduced by the model in using 

the same monthly HRU precipitation correction factor from 

year to year. Maurer and Halford (2004) report an uncertainty 

estimate of 15 percent of the total precipitation estimated 

for Carson Valley, however, the uncertainty associated with 

precipitation estimates for high-altitude areas is unknown.

Lastly, the reconstructed runoff time series to which 

the simulated runoff for ungaged perennial watersheds in 

the Carson Range was compared during model calibration, 

have an estimated uncertainty of about 30 percent. Sparse 

measurements accompany this data set and thus comparison of 

reconstructed and simulated daily mean runoff is most reliably 

done on an annual basis. The PRMS models generally exhibit 

a quicker runoff response to precipitation than most of the 

reconstructed time series, which use a composite of Carson 

River flows and gaged records from nearby watersheds. The 

overall effect is to minimize the daily variations typically 

present in the measured runoff. This is particularly evident for 

those watersheds with barren or rock exposure where runoff 

tends to be more immediate, reflecting the low infiltration 

during periods of rapid snowmelt or heavy rain.

Results of Watershed Modeling and 

Comparison with Previous Estimates

The watershed models provide estimates of annual mean 

unit-area rates of precipitation, runoff, evapotranspiration 

(ET), and ground-water inflow, in inches per acre for water 

years 1990–2002. In this report, the annual mean rates are 

reported as water-equivalent heights, in inches. Mean annual 

volumes, in acre-feet, were computed for water years 1990–

2002 by averaging the annual mean rates and multiplying by 

the drainage area of the watersheds, for comparison with the 

volumes estimated by Maurer and Berger (2007).

Perennial Watersheds

Simulated daily mean and annual mean runoff matches 

measured and reconstructed runoff reasonably well for most 

perennial watersheds, with the exceptions of Monument 

Creek, Sheridan Creek, and Jobs Canyon (table 4; figs. 11

and 12). The difference between simulated and measured or 

reconstructed mean annual runoff was 11 percent or less, also 

with the exceptions of Monument Creek, Sheridan Creek, and 

Jobs Canyon (table 4). The simulated mean annual runoff was 

31 percent less than the reconstructed runoff for Monument 

Creek watershed (table 4). High amounts of runoff as a 

percentage of precipitation for Mott Canyon and Monument 

Creek watersheds were noted by Maurer and Berger (2007, 

p. 32; table 1) along with the observation that they are 

not incised as greatly into the mountain blocks as other 

watersheds. Both observations indicate that these watersheds 

may be underlain by less permeable and less fractured 

bedrock, which is consistent with no ground-water inflow 

simulated from the two watersheds (table 4, fig. 12).

Results of Watershed Modeling and Comparison with Previous Estimates 33
nv19-4131_Fig11a

Simulated

Reconstructed

0.1

1

10

100

DAILY MEAN RUNOFF, IN CUBIC FEET PER SECOND

0.1

1

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 0.01

10

100

James Canyon—w atershed 2u

Water Canyon—w atershed 1u

Figure 11. Simulated and reconstructed daily mean runoff for 10 ungaged perennial watersheds in Carson Valley, Nevada 

and California, water years 1990–2002.

34 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
nv19-4131_Fig11b

Reconstructed

Simulated

0.1

1

10

100

1,000

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

DAILY MEAN RUNOFF, IN CUBIC FEET PER SECOND

0.1

1

0.01

10

100

Sierra Canyon—w atershed 3u

Genoa Canyon—w atershed 4u

Figure 11.—Continued.

Results of Watershed Modeling and Comparison with Previous Estimates 35
nv19-4131_Fig11c

Simulated

Reconstructed

0.1

1

10

100

0.1

1

10

100

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

DAILY MEAN RUNOFF , IN CUBIC FEET PER SECOND

Mott Canyon—watershed 6u

Monument Creek—watershed 7u

Figure 11.—Continued.

36 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
nv19-4131_Fig11d

Simulated

Reconstructed

0.1

1

10

0.1

1

10

100

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

DAILY MEAN RUNOFF, IN CUBIC FEET PER SECOND

Stutler Canyon—watershed 8u

Sheridan Creek—watershed 9u

Figure 11.—Continued.

Results of Watershed Modeling and Comparison with Previous Estimates 37
nv19-4131_Fig11e

Jobs Canyon—watershed 10u

Luther Canyon—watershed 11u

Simulated

Reconstructed

0.1

1

0.1

1

10

100

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

DAILY MEAN RUNOFF, IN CUBIC FEET PER SECOND

Figure 11.—Continued.

38 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
nv19-4131_Fig12a

5

0

10

15

20

25

35

30

James Canyon - watershed 2u

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Water Canyon—watershed 1u

5

0

10

15

20

25

30

ANNUAL MEAN RUNOFF AND INFLOW, IN INCHES

Reconstructed runoff

Ground-water inflow

Simulated runoff

Figure 12. Simulated and reconstructed annual mean runoff and ground-water inflow for 10 ungaged perennial watersheds in 

Carson Valley, Nevada and California, water years 1990–2002.

Results of Watershed Modeling and Comparison with Previous Estimates 39
nv19-4131_Fig12b

5

0

10

15

20

25

5

0

10

15

20

ANNUAL MEAN RUNOFF AND INFLOW, IN INCHES

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Genoa Canyon—watershed 4u

Sierra Canyon—watershed 3u

Reconstructed runoff

Ground-water inflow

Simulated runoff

Figure 12.—Continued.

40 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
nv19-4131_Fig12c

0

10

20

30

5

15

25

0

10

20

5

15

25

35

ANNUAL MEAN RUNOFF, IN INCHES

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Mott Canyon —watershed 6u

Monument Creek—watershed 7u

Reconstructed runoff

Simulated runoff

Figure 12.—Continued.

Results of Watershed Modeling and Comparison with Previous Estimates 41
nv19-4131_Fig12d

0

10

20

50

40

30

5

15

25

0

10

20

5

15

25

55

45

35

60

ANNUAL MEAN RUNOFF AND INFLOW, IN INCHES

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Sheridan Creek - watershed 9u

Stutler Canyon - watershed 8u

Reconstructed runoff

Ground-water inflow

Simulated runoff

Figure 12.—Continued.

42 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
nv19-4131_Fig12e

Luther Canyon —watershed 11u

5

0

10

15

20

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Jobs Canyon—watershed 10u

0

10

20

5

15

25

ANNUAL MEAN RUNOFF AND INFLOW, IN INCHES

Reconstructed runoff

Ground-water inflow

Simulated runoff

Figure 12.—Continued.

Mean annual runoff was underestimated for Sheridan 

Creek watershed by 46 percent, no ground-water inflow 

from the watershed was simulated, and the rates of groundwater inflow simulated for Stutler Canyon watershed were 

considerably greater than any other watershed (table 4; 

fig. 12). These results are consistent with the observations of 

Maurer and Berger (2007, p. 30), who noted large differences 

in runoff as a percentage of precipitation from the two 

watersheds (table 1), and suggested that subsurface flow may 

be taking place from the Stutler Canyon watershed to the 

Sheridan Creek watershed.

The source of runoff in the Sheridan Creek watershed is a 

series of springs that issue from the base of a ridge separating 

the two watersheds, and the Stutler Canyon watershed lies at 

a higher altitude, to the west of the Sheridan Creek watershed 

(watersheds 8u and 9u, respectively, in fig. 3). For these 

reasons, estimates of ground-water inflow to Carson Valley 

were made from the combined areas of the Stutler Canyon 

and Sheridan Creek watersheds by Maurer and Berger (2007). 

Results of the watershed modeling suggest that the deficiency 

of simulated runoff from Sheridan Creek watershed, 600 

acre-ft/yr, may be supplied from the 1,600 acre-ft/yr of 

subsurface flow simulated from Stutler Canyon watershed 

(table 4). The remaining 1,000 acre-ft/yr from Stutler Canyon 

watershed likely becomes ground-water inflow to basin-fill 

aquifers of Carson Valley.

Simulated daily mean runoff from Jobs Canyon 

watershed generally was overestimated from 1990 to 1995, but 

matches reconstructed runoff more closely from 1996 to 2002 

(fig. 10). Annual mean runoff appears to match reconstructed 

runoff more closely than daily mean runoff from 1990 to 1995 

(fig. 12), likely because of compensating differences from 

periods of under- and overestimation during the year. Mean 

annual runoff was overestimated by 18 percent for water years 

1990–2002 (table 4). The difference between the simulated 

and estimated runoff volumes may not be meaningful because, 

as stated previously, the reconstructed daily mean flows 

have an uncertainty of as much as 30 percent. However, the 

reconstructed runoff represents the best available estimate of 

daily flows from the ungaged watersheds.

Results of Watershed Modeling and Comparison with Previous Estimates 43
For all perennial watersheds, simulated precipitation was 

within 15 percent of that estimated by Maurer and Berger 

(2007), largely because effort was made during calibration 

to match the previous estimate of precipitation, as previously 

discussed. Simulated ET from the models generally was 

less than ET estimated by Maurer and Berger (2007) largely 

because of the greater volumes of simulated ground-water 

inflow, and also in part, because of differences between 

simulated and reconstructed runoff. The ET estimates made 

by Maurer and Berger (2007) were calculated as the difference 

between precipitation and the combined volumes of runoff and 

estimates of ground-water inflow. Their ET estimates therefore 

include the combined errors associated with ground-water 

inflow estimates and the reconstructed runoff estimates. ET 

estimates in the PRMS model are a summation of sublimation, 

soil water loss, canopy interception loss, and evaporation from 

impervious surfaces.

Simulated annual rates of ground-water inflow from 

the watersheds to the basin-fill deposits of Carson Valley 

generally are less than 5 in. for most watersheds, but are as 

great as 22 in. for Stutler Canyon, about 12 in. for Daggett 

Creek, and about 10 in. for Pine Nut and Buckeye Creeks 

(figs. 9 and 12). The high annual rates for Stutler Canyon 

watershed are explained by the likelihood of subsurface 

flow to Sheridan Creek (not simulated), which would reduce 

ground-water inflow contributions from Stutler Canyon 

watershed to the basin-fill deposits of Carson Valley. The high 

rates for Daggett Creek watershed are consistent with its low 

amount of runoff as a percentage of precipitation, 21 percent 

(table 1). The relatively low amount of runoff indicates that 

bedrock underlying the Daggett Creek watershed likely is 

more fractured and permeable than other watersheds, allowing 

greater rates of infiltration and ground-water inflow. The 

Daggett Creek watershed lies at the topographically lowest 

point along the crest of the Carson Range; further indication 

that bedrock underlying the watershed is more fractured, 

erodible, and permeable than other watersheds of the Carson 

Range. Bedrock underlying the Pine Nut and Buckeye Creek 

watersheds (watersheds 13g and 14g, respectively, in fig. 3) 

also may be more fractured than those of the Carson Range, 

as indicated by the number of mapped faults. Moore (1969, 

p. 18) describes the Pine Nut Mountains as being composed of 

several orographic blocks which have been tilted individually, 

in contrast to the Carson Range, which generally was uplifted 

along a single fault zone with a large displacement (fig. 3).

The simulated mean annual volume of ground-water 

inflow to the basin-fill aquifers of Carson Valley from the 14 

perennial watersheds for 1990–2002 totaled 14,400 acre-ft, 

more than twice the 6,600 acre-ft estimated by Maurer and 

Berger (2007; table 4) using the water-yield method. In most 

cases, greater volumes of simulated ground-water inflow 

coincided with greater volumes estimated by Maurer and 

Berger (2007). The watershed models simulated groundwater inflow from Water Canyon and Fredericksburg Canyon 

watersheds, whereas Maurer and Berger (2007) estimated no 

ground-water inflow using the water-yield method.

Ephemeral Watersheds

Lacking measured streamflow data, calibration of the 

ephemeral watershed models was limited to the adjustment 

of precipitation volumes to match that estimated by Maurer 

and Halford (2004) because the amount of ephemeral 

runoff is uncertain. Simulated precipitation rates generally 

were less than those simulated for the perennial watersheds 

(tables 4 and 5), as would be expected because of the lower 

altitude of most of the ephemeral watersheds. Similarly, 

simulated ET rates generally were less than those for the 

perennial watersheds, primarily because of the lower rates of 

precipitation.

Simulated runoff and ground-water inflow for the 

ephemeral watersheds of the Carson Range depend greatly on 

the selected index model and precipitation inputs (table 5). For 

those watersheds that used the Daggett Creek index model, 

simulated runoff rates and volumes were similar in magnitude 

to simulated ground-water inflow rates and volumes. For those 

watersheds that used the Fredericksburg Canyon index model, 

simulated runoff rates and volumes were considerably greater 

than simulated ground-water inflow rates and volumes. The 

two ephemeral watersheds that have large volumes of runoff 

(watersheds 5e and 10e, table 5 and fig. 3) are large in area 

and, more importantly, have HRUs at altitudes greater than 

8,000 ft, thus receiving proportionately more precipitation.

Simulated mean annual runoff rates ranged from about 

5 to 7 in. for ephemeral watersheds using Daggett Creek 

watershed model as an index model, and from 9 to 13 in. for 

ephemeral watersheds using Fredericksburg Canyon as an 

index model (table 5). Mean annual ephemeral runoff from the 

Carson Range simulated from the models totaled 9,900 acre-ft 

with an overall runoff rate of 8.4 in., similar to the volume of 

8,000 acre-ft and rate of 7 in. estimated by Maurer and others 

(2004, p. 14).

The large area of ephemeral runoff modeled near the 

Pine Nut Mountains (watershed 11e, fig. 3) had a mean annual 

simulated runoff volume of 800 acre-ft, for the area of 78,200 

acres, or a rate of 0.1 in. The area of the watershed model near 

the Pine Nut Mountains was selected to include the general 

area of exposed semiconsolidated sediments (fig. 3). In this 

study, runoff from the eastern side of the valley floor underlain 

by alluvial fans was assumed to be negligible.

Mean annual ground-water inflow rates simulated for 

ephemeral watersheds of the Carson Range ranged from 0.07 

to 0.7 in. for watersheds using the Fredericksburg Canyon 

index model, and from about 5 to 7 in. for watersheds using 

the Daggett Creek index model (table 5). The mean annual 

ground-water inflow simulated from ephemeral watersheds 

of the Carson Range totaled 3,500 acre-ft. Simulated mean 

annual ground-water inflow from the ephemeral watershed 

on the eastern side of the valley (watershed 11e) totaled 5,700 

acre-ft, for an annual rate of 0.9 in. (table 5).

44 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Table 5. Summary of model results for selected ephemeral watersheds in Carson Valley, Nevada and California, water years 

1990–2002. 

[Values in inches are volumes in acre-feet, divided by watershed area, in acres, multiplied by 12. Watershed No.: “e” indicates ephemeral watershed. 

Locations are shown in figure 3. Index model: Watershed model of gaged watershed (see table 1) used as index model for watershed model of ephemeral 

watershed. Simulated runoff efficiency: Runoff as a percentage of precipitation. Simulated mean annual ground-water inflow: Ground-water inflow is 

defined as ground-water inflow to basin-fill aquifers of Carson Valley. Abbreviations: acre-ft, acre-feet; in., inch]

Watershed 

No.

Drainage area 

(acres, rounded) Index model

Simulated

Mean annual 

precipitation Mean annual 

evapotranspiration

Mean annual 

runoff Runoff 

efficiency

(percent)

Mean annual 

ground-water inflow

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

acre-ft

(in.)

1e 2,120 Daggett Creek 3,980 2,090 930 23 960

(23) (12) (5.3) (5.4)

2e 600 Fredericksburg Canyon1 1,150 590 530 46 4

(23) (12) (11) (0.08)

3e 1,320 Fredericksburg Canyon 2,430 1,320 1,020 42 8

(22) (12) (9.3) (0.07)

4e 500 Fredericksburg Canyon 830 410 370 45 4

(20) (9.8) (9) (0.1)

5e 2,270 Fredericksburg Canyon 4,330 2,350 1,760 41 30

(23) (12) (9.3) (0.2)

6e 2,190 Daggett Creek 3,930 1,660 980 25 1,230

(22) (9.1) (5.4) (6.7)

7e 340 Daggett Creek 750 350 200 27 210

(27) (12) (7.3) (7.4)

8e 1,700 Daggett Creek 3,460 1,670 950 27 910

(24) (12) (6.7) (6.4)

9e 720 Fredericksburg Canyon 1,290 640 590 46 8

(22) (11) (9.8) (0.1)

10e 2,500 Fredericksburg Canyon 5,790 2,890 2,610 43 150

(28) (14) (13) (0.7)

Subtotal, Carson Range (rounded)

14,300 27,900 14,000 9,900 36 3,500

(23) (12) (8.3) (2.9)

Subtotal Pine Nut Mountains 11e

78,200 Buckeye Creek 58,300 51,500 800 1 5,700

(8.9) (7.9) (0.1) (0.9)

Total (rounded)

92,500 86,200 65,500 10,700 12 9,200

(11) (8.5) (1.4) (1.2)

1Simulated using Fredricksburg Canyon index model because of small outcrop of metamorphic rocks near top of watershed.

Results of Watershed Modeling and Comparison with Previous Estimates 45
Ground-Water Inflow Simulated from 

Watershed Models and Variation from Dry to 

Wet Conditions.

The simulated ground-water inflow from the perennial 

and ephemeral watersheds was combined with estimates of the 

infiltration of simulated ephemeral runoff to provide the total 

volumes of ground-water inflow to the basin-fill aquifers of 

Carson Valley from the Carson Range and Pine Nut Mountains 

(table 6). Application of the watershed models provides insight 

into the effect of climate variability on the water resources of 

Carson Valley. For this reason, ground-water inflow simulated 

from the watershed models was summarized for water years 

1990–2002, for dry conditions during water years 1990–92, 

and for wet conditions during water years 1995–97 to show 

the variability in ground-water inflow.

 Maurer and Berger (2007, p. 36) assumed all ephemeral 

runoff infiltrates the western alluvial fans and becomes 

ground-water inflow, supported by evidence that little 

ephemeral runoff from the Carson Range reaches the valley 

floor. Studies by Constantz and others (1994, p. 3261) in 

New Mexico, and Ronan and others (1998, p. 2142) in Eagle 

Valley, Nev., show that 4 to 6 percent of runoff from similar 

ephemeral streams is lost to evaporation and near-channel 

evapotranspiration. For this reason, the volumes of simulated 

ephemeral runoff that were assumed to infiltrate and become 

ground-water inflow were decreased by 5 percent. During 

extreme runoff events, some runoff likely reaches the valley 

floor. However, such events are rare and runoff reaching the 

valley floor is assumed to be a small percentage of mean 

annual runoff, and can be neglected.

Table 6. Mean annual ground-water inflow to basin-fill deposits of Carson Valley simulated with watershed models, water 

years 1990–2002, and compared with mean annual inflow simulated during dry conditions, water years 1990–92, and wet 

conditions, water years 1995–97, Nevada and California. 

{Values are rounded to two significant figures. Mean annual ground-water inflow, dry conditions: If MAG is mean annual ground-water 

inflow, percent difference calculated as 100*(MAGdry conditions–MAG1990–2002/MAG1990–2002; wet conditons: If MAG is mean annual ground-water 

inflow, percent difference calculated as 100*(MAGwet conditions–MAG1990–2002/MAG1990–2002. Abbreviations: acre-ft, acre-feet]

Ground-water inflow source 

Simulated mean annual ground-water inflow

Water years 

1990–2002 

(acre-feet)

Dry conditions, 

water years 1990–92

Wet conditions, 

water years 1995–97

(acre-ft) (Percent 

difference) (acre-ft) (Percent difference)

Carson Range

Ground-water inflow from watersheds

Perennial 16,200 3,400 -45 9,900 60

Ephemeral 23,500 1,200 -66 5,200 49

Infiltration of ephemeral runoff 39,400 2,600 -72 17,000 81

Subtotal (rounded) 19,000 7,200 -62 32,000 68

Pine Nut Mountains

Ground-water inflow from watersheds

Perennial 18,200 100 -99 21,000 156

Ephemeral 25,700 0 -100 18,000 216

Infiltration of ephemeral runoff 42,100 470 -78 4,800 128

Subtotal (rounded) 16,000 570 -96 44,000 175

Total for Carson Range and Pine Nut Mountains

Total (rounded) 35,000 7,800 -78 76,000 117

1 From table 4.

2 From table 5. 

3 From table 5, simulated mean annual ephemeral runoff, 9,900 acre-ft, less 5 percent loss to evapotranspiration, 500 acre-ft.

4 From table 5, plus runoff of Pine Nut and Buckeye Creeks, less 5 percent loss to evapotranspiration.

46 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Variability in ground-water recharge to basin-fill aquifers 

of Carson Valley reflects the year-to-year differences in 

climatic conditions. Quantifying potential changes in groundwater recharge during wet and dry hydrologic conditions is 

useful for estimating the ground-water and surface-water 

response to changing conditions, as well as for evaluating the 

hypothetical effects of long-term climate change on groundwater inflow to Carson Valley if annual precipitation is 

reduced. The mean annual ground-water inflow to basin-fill 

aquifers of Carson Valley simulated by the watersheds models 

for water years 1990–2002 was 35,000 acre-ft, with 19,000 

acre-ft from the Carson Range and 16,000 acre-ft from the 

Pine Nut Mountains (table 6). Simulated mean annual groundwater inflow varied an order of magnitude, from 7,800 acre-ft 

during dry conditions (water years 1990–92), to 76,000 acre-ft 

during wet conditions (1995–97). The variation in groundwater inflow from dry to wet conditions is less in the Carson 

Range than the Pine Nut Mountains.

The large variability in ground-water inflow indicates 

that the annual volume of this source of recharge to basinfill aquifers of Carson Valley depends greatly on climate. 

Knowledge of the potential range in ground-water inflow 

from wet to dry conditions is useful in developing droughtmitigation plans by water managers. Long-term climate 

changes that reduce the amount of annual precipitation have 

the potential to greatly affect ground-water inflow to the basinfill aquifers of Carson Valley.

Uncertainty in Estimates of Simulated GroundWater Inflow

A major source of uncertainty in the estimates of groundwater inflow simulated by the watershed models was the 

selection of index models for the ephemeral watersheds of the 

Carson Range. For the ephemeral watersheds where runoff 

has not been measured, bedrock type was the only basis for 

index model selection. Therefore, simulated runoff could 

not be verified. The uncertainty in ground-water inflow from 

ungaged perennial watersheds from index model selection was 

considered much less because model parameters were adjusted 

to match the reconstructed runoff from each watershed. The 

uncertainty in ground-water inflow and runoff from the area of 

ephemeral runoff on the eastern side of the valley (watershed 

11e, fig. 3) also is considered small because the Buckeye 

Creek index model represents an area with surficial geology 

similar to that of the area of ephemeral runoff.

The uncertainty involved with selection of the appropriate 

index model for ephemeral watersheds was evaluated by 

applying the mean annual unit-area rates obtained for 

watersheds modeled with each index model type to the entire 

area of ephemeral runoff from the Carson Range (table 7). 

The index models developed for the Daggett Creek and 

Fredericksburg Canyon watersheds may be viewed as endmembers for estimates of ground-water inflow and ephemeral 

runoff from the Carson Range.

The mean annual unit-area values for runoff and groundwater inflow from the combined area of ephemeral watersheds 

of the Carson Range were 10.5 and 0.3 in., respectively for 

watersheds using the Fredericksburg Canyon index model, and 

5.8 and 6.2 in., respectively for watersheds using the Daggett 

Creek index model (table 7). Applying these unit-area values 

to the entire area of all ephemeral watersheds, 14,300 acres, 

results in volumes of mean annual runoff ranging from 6,900 

to 12,500 acre-ft, and volumes of mean annual ground-water 

inflow ranging from 400 to 7,400 acre-ft.

The potential range of ground-water inflow from the 

Carson Range can be assessed by substituting the low- and 

high-range values from the uncertainty analysis for ephemeral 

watersheds of the Carson Range in table 6. The resulting 

totals for annual ground-water inflow, after reducing the 

range in ephemeral runoff by 5 percent for evapotranspiration 

losses, range from 13,000 to 26,000 acre-ft. This range is 

considerably less than the range in annual ground-water inflow 

from dry to wet conditions, 7,200 to 32,000 acre-ft.

Watersheds of the Carson Range underlain by 

metamorphic rocks had runoff efficiencies of 38 to 45 percent, 

with the exception of Sierra Canyon (table 1). With the 

exceptions of the anomalous high-runoff-efficiency watersheds 

of Mott Canyon, Monument Creek, and Sheridan Creek, and 

the anomalous low-runoff efficiency watershed of Stutler 

Canyon, watersheds underlain by granitic rocks had runoff 

efficiencies of 21 to 31 percent. Thus, bedrock type appears 

to affect hydrologic processes controlling runoff and groundwater inflow to the basin-fill deposits of Carson Valley. For 

this reason, the volumes simulated for ephemeral watersheds 

of the Carson Range using the index model selected on the 

basis of bedrock type is considered to be the best and most 

reasonable estimate.

Results of Watershed Modeling and Comparison with Previous Estimates 47
Ground-Water Inflow Simulated from 

Watershed Models Compared with 

Previous Estimates

Ground-water inflow and ephemeral runoff simulated 

using the watershed models of the Carson Range and Pine Nut 

Mountains were combined with previous estimates of groundwater inflow to the northern part of Carson Valley, and groundwater recharge from precipitation on the western alluvial 

fans and eolian sand and gravel deposits made by Maurer and 

Berger (2007), for comparison with the previous estimates of 

ground-water inflow. The estimates for ground-water inflow 

and runoff from ephemeral watersheds of the Carson Range 

using index models selected on the basis of bedrock type, as 

described above, were used in calculating the totals.

Mean annual ground-water inflow to the basin-fill 

deposits of Carson Valley from the Carson Range simulated 

from the ephemeral and perennial watersheds totals 20,000 

acre-ft. The volume of 20,000 acre-ft is 7,000 acre-ft 

less than the estimate obtained from the chloride-balance 

method and almost double the estimate from the wateryield method (table 8). Inflow simulated from the Pine Nut 

Mountains and the eastern alluvial fans was 16,000 acre-ft, 

which is almost 50 percent greater than the 11,000 acre-ft 

estimated from the chloride-balance method. For both the 

Carson Range and the Pine Nut Mountains, the estimates of 

ground-water inflow simulated from the watershed models 

were considerably greater than the estimate obtained using 

the water-yield method. This is in part because the models 

simulated greater volumes of ground-water inflow from the 

perennial watersheds, and in part because the models indicate 

that ground-water inflow does take place from the ephemeral 

watersheds, which was assumed to be negligible by Maurer 

and Berger (2007, p. 31).

Maurer and others (2007, p. 28) used soil-chloride data to 

determine that ground-water recharge from precipitation was 

not taking place on the eastern side of Carson Valley. However, 

the soil-chloride data were collected only near the tops of hills 

in the area of ephemeral runoff, and not in ephemeral stream 

channels. The soil-chloride data and watershed modeling 

results suggest ground-water inflow estimated from watershed 

11e likely is derived from infiltration of runoff beneath 

ephemeral stream channels.

The total mean annual ground-water inflow simulated 

from the watershed models for Carson Valley was 38,000 acreft, similar to the volume obtained from the chloride-balance 

method, 40,000 acre-ft.

Table 7. Potential range in estimates of runoff and ground-water inflow to basin-fill aquifers of Carson Valley from ephemeral 

watersheds of the Carson Range, Nevada and California. 

[Values in inches are volumes in acre-feet, divided by watershed area, in acres, multiplied by 12. Simulated mean annual runoff: Values may not match 

presented values due to rounding. Simulated mean annual ground-water inflow: Ground-water inflow defined as ground-water inflow to basin-fill sediments 

of Carson Valley. Abbreviations: acre-ft, acre-feet; in., inch]

Watershed and index model

Drainage area 

(acres, 

rounded)

Simulated mean annual

Runoff Ground-water inflow

(acre-ft) (in.) (acre-ft) (in.)

All ephemeral watersheds1 14,300 9,900 28.3 3,500 22.9

Ephemeral watersheds using Fredericksburg Canyon index model1 7,900 6,900 210.5 200 20.3

Ephemeral watersheds using Daggett Creek index model1 6,400 3,100 25.8 3,300 26.2

All ephemeral watersheds using unit-area rates for Fredericksburg Canyon 

index watersheds

14,300 312,500 10.5 3 400 0.3

All ephemeral watersheds using unit-area rates for Daggett Creek index 

watersheds

14,300 46,900 5.8 47,400 6.2

1From table 5.

2 Unit-area runoff and ground-water inflow, calculated by dividing runoff or ground-water inflow, in acre-feet, by drainage area, in acres, and multiplying 

by 12.

3 Calculated by dividing unit-area runoff and ground-water inflow for ephemeral watershed models using Fredericksburg canyon index model by 12, and 

multiplying by drainage area, in acres.

4 Calculated from unit-area runoff and ground-water inflow for ephemeral watershed models using Daggett Creek index model by 12, and multiplying by 

drainage area, in acres.

48 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Table 8. Estimates of mean annual ground-water inflow to basin-fill aquifers of Carson Valley using 

water-yield and chloride-balance methods by Maurer and Berger (2007) and simulated with watershed 

models of this study, Nevada and California. 

[Mean annual ground-water inflow: From yield and chloride-balance methods from Maurer and Berger (2007, 

p. 38); represents values estimated using precipitation estimates for 1971–2000, and runoff estimates for 1990–2002. 

Abbreviations: –, indicates information not available.]

Ground-water 

inflow source

Mean annual ground-water inflow

(acre-feet)

Simulated with 

watershed models, 

water years 

1990–2002

Water-yield 

method

Chloridebalance 

method 

Northern Carson Valley

Ground-water inflow from Eagle Valley1 1,450 1,450 1,450

Precipitation on eolian sand and gravel deposits 250 250 250

Subtotal (rounded) 1,700 1,700 1,700

Carson Range and western alluvial fans

Precipitation on alluvial fans 500 500 –

Ground-water inflow from watersheds

Perennial 26,200 2,400 –

Ephemeral 33,500 0 –

Infiltration of ephemeral runoff 49,400 8,000 –

Subtotal (rounded) 20,000 11,000 27,000

Pine Nut Mountains and eastern alluvial fans

Ground-water inflow from watersheds

Perennial 28,200 4,300 –

Ephemeral 35,700 0 –

Infiltration of ephemeral runoff 52,100 5,000 –

Subtotal (rounded) 16,000 9,300 11,000

Total for Carson Valley 

Total (rounded) 38,000 22,000 40,000

1From Maurer and Thodal (2000, p. 33–34).

2From table 4. 

3From table 5.

4From table 5, simulated mean annual ephemeral runoff, 9,900 acre-ft, less 5 percent loss to evapotranspiration, 500 

acre-ft.

5From table 5, plus runoff of Buckeye and Pine Nut Creeks, less 5 percent loss to evapotranspiration.

Ground-Water Inflow Simulated from Watershed Models Compared with Previous Estimates 49
Updated Ground-Water Budget for 

Basin-fill Aquifers of Carson Valley

An updated water budget for the basin-fill aquifers of 

Carson Valley was calculated using estimates of groundwater inflow and ephemeral runoff from the Carson Range 

and Pine Nut Mountains simulated from the watershed 

models, combined with estimates of other ground-water 

budget components made by Maurer and Berger (2007, p. 

53). Estimates of mean annual ground-water inflow for water 

years 1990–2002 were assumed to be representative of water 

years 1990–2005, the period for which the other water-budget 

components were derived.

Mean annual ground-water recharge using ground-water 

inflow simulated from the watershed models ranged from 

51,000 to 54,000 acre-ft (table 9). Estimates of mean annual 

ground-water discharge ranged from 44,000 to 47,000 acre-ft, 

including an increase of 3,000 acre-ft/yr from the previous 

estimate of net ground-water pumping by Maurer and Berger 

(2007, p. 42). Maurer and Berger (2007, p. 43) subtracted 

estimates of 3,000 acre-ft for return flow from ground water 

pumped for irrigation and for a U.S. Fish and Wildlife fish 

hatchery from total pumping for water years 1990–2005 to 

obtain estimates of net ground-water pumping. The return 

flow to irrigation ditches, however, is likely to be diverted 

further downstream in Carson Valley for irrigation. Thus, the 

return flow may effectively be removed from the hydrologic 

system prior to leaving Carson Valley and not be available 

for ground-water recharge. This is especially true during dry 

years when ground-water pumping for irrigation is greatest. 

For these reasons, estimates of net ground-water pumping for 

water years 1990–2005 were increased from the estimate made 

by Maurer and Berger (2007, p. 43; 15,000–18,000) by 3,000 

acre-ft/yr, to range from 18,000 to 21,000 acre-ft.

 Estimates of ground-water recharge using results of the 

watershed models were somewhat greater than estimates of 

ground-water discharge. The difference is likely because of the 

uncertainties in both estimates, rather than an actual difference 

between recharge and discharge. Estimates of ground-water 

Table 9. Updated ground-water budget for basin-fill aquifers of Carson Valley using previous 

estimates by Maurer and Berger (2007), and estimates simulated from watershed models in this 

study, water years 1990–2005. 

Source of ground-water recharge 

to and discharge from basin-fill 

aquifers of Carson Valley

Estimated mean annual volume

(acre-feet)

Maurer and Berger 

(2007) Current study

Ground-water recharge

Ground-water inflow from Carson Range, Pine Nut 

Mountains, and Eagle Valley, and recharge from 

precipitation on alluvial fans eolian sand, and 

gravel deposits 

122,000 – 40,000 238,000

Ground-water recharge from runoff of the 

Carson River

110,000 110,000

Secondary recharge of pumped ground water 13,000 – 6,000 13,000 – 6,000

Total 35,000 – 56,000 51,000 – 54,000

Ground-water discharge

Ground-water evapotranspiration from 

phreatophytic and riparian vegetation and 

non-irrigated pasture grasses 

111,000

Ground-water discharge to streamflow of the 

Carson River

115,000

Net ground-water pumping 318,000 – 21,000

Total 44,000 – 47,000

1From Maurer and Berger (2007, p. 53).

2From table 8.

3From Maurer and Berger (2007, p. 42) with the addition of 3,000 acre-ft/yr assumed unavailable for ground-water 

recharge in this study. Includes domestic pumping in California portion of study area.

50 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
inflow simulated from the watershed models were in close 

agreement with those obtained from the chloride-balance 

method (table 8). This provides more confidence that the 

relatively independent estimates from the chloride-balance 

method and simulated values from the watershed models 

provide a reasonably accurate volume for estimates of 

ground-water recharge components. The two estimates are 

not completely independent, however, because they use 

the same distribution of annual precipitation. The chloridebalance method uses physical data on runoff and the chloride 

concentration of precipitation, runoff, and ground water; 

whereas the watershed models use physical data on vegetation, 

soils, and topography, and daily data on runoff and climate.

The estimate for mean annual ground-water recharge 

at the low end of the range, 51,000 acre-ft, is similar to the 

estimate for mean ground-water discharge at the high end 

of the range, 47,000 acre-ft (table 9). Thus, a mean annual 

volume of about 50,000 acre-ft is a reasonable estimate for 

ground-water recharge to and discharge from the basin-fill 

aquifers of Carson Valley.

Estimates of infiltrated ephemeral runoff and mean 

annual ground-water inflow from the mountains simulated 

using the watershed models vary over an order of magnitude 

from dry to wet conditions from 7,800 to 76,000 acre-ft, 

respectively (table 6). Ground-water inflow is only one 

component of recharge for the ground-water budget, although 

it is the largest in magnitude. Ground-water recharge from 

runoff of the Carson River would likely be greater in wet 

years and lesser in dry years, but the magnitude of change 

is uncertain. Secondary recharge or return flows of pumped 

ground water from municipal and domestic pumping would 

likely not change significantly from wet to dry years. During 

multi-year drought conditions, the watershed simulations 

indicate that ground-water recharge could be as much as 80 

percent less than the mean annual volume of 50,000 acre-ft.

Summary and Conclusions

To address concerns over increased development in 

Carson Valley, the U.S. Geological Survey (USGS) recently 

made estimates of ground-water inflow to basin-fill aquifers 

of Carson Valley from the adjacent Carson Range and Pine 

Nut Mountains. Ground-water inflow was estimated to range 

from 22,000 acre-ft/yr using a water-yield method, to 40,000 

acre-ft/yr using a chloride-balance method. Because of the 

relatively large range in these estimates, and uncertainties in 

each method, watershed models were developed for perennial 

watersheds of the Carson Range and Pine Nut Mountains to 

provide an independent estimate of ground-water inflow to 

Carson Valley

The model used for this study was the PrecipitationRunoff Modeling System (PRMS), a physically based, 

distributed-parameter model. A Geographic Information 

System (GIS) program, the Weasel Toolbox was used to 

manage spatial data and characterize model drainages and to 

develop HRUs.

Models were developed first for the four perennial 

watersheds having gaged daily mean runoff; Daggett Creek, 

Fredericksburg Canyon, Pine Nut Creek, and Buckeye Creek 

watersheds. Models were then developed for 10 ungaged 

perennial watersheds in the Carson Range using the models 

developed for either the Daggett Creek or the Fredericksburg 

Canyon watersheds as an index model. Selection of the 

gaged watershed to be used as an index model was based on 

similarity between the major bedrock type and the percentage 

of precipitation that becomes runoff in each watershed. 

Finally, models were developed for 10 ephemeral watersheds 

in the Carson Range and a large area of ephemeral runoff 

near the Pine Nut Mountains to estimate the quantity of 

ephemeral runoff tributary to Carson Valley and the potential 

for ground-water inflow from ephemeral watersheds. Because 

the ephemeral runoff is uncertain, selection of the index 

model was based only on the bedrock type underlying the 

ephemeral watershed. The Buckeye Creek watershed model 

was used as an index model for the area of ephemeral runoff 

near the Pine Nut Mountains because of the similarity of 

geologic units exposed in the two areas. Model calibration was 

constrained by daily mean flows for four gaged watersheds 

in Carson Valley and ten ungaged watersheds in the Carson 

Range estimated in a previous study. The models were further 

constrained by annual precipitation volumes estimated in a 

previous study to provide estimates of ground-water inflow 

using similar water input.

The calibration periods were water years 1990–2002 

for watersheds in the Carson Range, the period for which 

reconstructed runoff was available for ungaged perennial 

watersheds, and water years 1981–97 for Pine Nut Creek 

and Buckeye Creek watersheds. Simulations for water years 

1990–2002 were then made using the calibrated models for 

Pine Nut Creek and Buckeye Creek watersheds to obtain daily 

mean values for the 1990–2002 period.

The watershed models were affected by the assumption 

that the ungaged perennial and ephemeral watersheds are 

hydrologically similar to the index watersheds, the scale of 

available soil data, the adequacy of available climate data and 

accuracy of precipitation estimates using the linear-relations, 

and the accuracy of the reconstructed daily mean runoff used 

for calibration of the ungaged perennial watersheds.

The error of the resulting models was determined for 

watersheds having gaged runoff data. Mean annual bias for 

the period of record for Daggett Creek and Fredericksburg 

Canyon watersheds was negligible, relative error was about 6 

and 12 percent, respectively, and RMSE was about 1 and 6 in., 

respectively. A satisfactory overall fit was obtained between 

simulated and measured runoff for Daggett Creek for the 

1993–98 period of high runoff (and periods of higher groundwater inflow); however, runoff is underestimated for the drier 

years (1990–92, 1994).

Summary and Conclusions 51
Overall, mean annual water budget volumes indicate 

that the Daggett Creek and Fredericksburg Canyon watershed 

model simulations are in agreement with previous estimates 

for the 1990–2002 period. The mean annual runoff efficiency 

using the simulated runoff and simulated precipitation was 

20 percent for Daggett Creek watershed and 45 percent 

for Fredericksburg Canyon watershed, both comparable to 

the efficiency calculated with the measured flow. With the 

exception of the April–June season, calibration statistics for 

the seasonal aggregates are considered satisfactory for both 

the Daggett Creek and Fredericksburg Canyon watershed 

simulations.

Error for the period of record for the Pine Nut and 

Buckeye Creek watersheds was greater, in part due to the 

sensitivity of the calibration statistic for days with zero and 

low runoff whereby differences in runoff were assigned a large 

relative error. In addition, the spatial and temporal distribution 

of precipitation on the east side of Carson Valley may not be 

adequately represented due to the more localized nature of 

storm events, and the lack of high-altitude precipitation data. 

The mean annual runoff efficiency for the 1990–2002 period 

using the simulated runoff and simulated precipitation was 2 

percent for Pine Nut Creek and 2 percent for Buckeye Creek, 

both comparable to the efficiency calculated with measured 

flow.

The Pine Nut Creek watershed model underestimates 

runoff for all but the wet years in the latter part of the record, 

while adequately simulating the bulk of spring runoff for 

most years. The Pine Nut Creek watershed model has a large 

negative bias, and under-estimates mean annual runoff on 

average by 11 percent. Overall. the simulated hydrograph 

for Buckeye Creek indicates a much quicker response to 

precipitation than measured at the gage and the Buckeye Creek 

model tends to over-estimate runoff. For water years 1981–97, 

the mean annual error is about –5 percent when water year 

1994 is removed. For the February–April period, the Buckeye 

Creek model has a large negative bias and 5 percent relative 

error. The bias and error of the calibrated models are within 

generally accepted limits for watershed models, indicating 

the simulated rates and volumes of runoff and ground-water 

inflow are reasonable.

The daily mean values of precipitation, runoff, ET, and 

ground-water inflow simulated from the watershed models 

were summed to provide annual mean rates and volumes 

for each year of the simulations, and mean annual rates and 

volumes for water years 1990–2002. Daily mean and annual 

mean simulated runoff matched measured or reconstructed 

runoff reasonably well for most watersheds, with the 

exceptions of Monument Canyon, Sheridan Creek, and Jobs 

Canyon. The difference between mean annual simulated and 

measured or reconstructed runoff was 11 percent or less, also 

with the exceptions of Monument Creek, Sheridan Creek, and 

Jobs Canyon.

Model results were consistent with a previous study, in 

that no subsurface flow was simulated from Mott Canyon, 

Monument Creek, and Sheridan Creek watersheds, and 

subsurface flow may be taking place from the Stutler Canyon 

to the Sheridan Creek watershed. However, the watershed 

models simulated ground-water inflow from the Water Canyon 

and Fredericksburg Canyon watersheds, and ground-water 

inflow from ephemeral watersheds in the Carson Range and 

Pine Nut Mountains. The simulated mean annual volume of 

ground-water inflow for the 14 perennial watersheds totaled 

14,400 acre-ft. The annual ground-water inflow simulated 

from the 10 ephemeral watersheds of the Carson Range totaled 

3,500 acre-ft, whereas a previous study assumed ground-water 

inflow from ephemeral watersheds of the Carson Range was 

negligible. Simulated ground-water inflow from the ephemeral 

watershed near the Pine Nut Mountains was 5,700 acre-ft.

Simulated mean annual runoff rates ranged from about 

5 to 7 inches for ephemeral watersheds using Daggett Creek 

as an index station and from 9 to 13 inches for ephemeral 

watersheds using Fredericksburg Canyon as an index station. 

Mean annual ephemeral runoff from the Carson Range 

simulated from the models totaled 9,900 acre-feet. For the area 

of ephemeral runoff near the Pine Nut Mountains, the mean 

annual ephemeral runoff rate simulated from the model was 

0.1 inch for a total runoff of 800 acre-feet.

The mean annual ground-water inflow to basin-fill 

aquifers of Carson Valley from the Carson Range and the Pine 

Nut Mountains simulated by the watersheds models for water 

years 1990–2002 was 35,000 acre-feet, with 19,000 acre-feet 

from the Carson Range and 16,000 acre-feet from the Pine 

Nut Mountains. The simulated mean annual inflow varied 

over an order of magnitude, from 7,800 acre-feet during dry 

conditions (water years 1990–92), to 76,000 acre-feet during 

wet conditions (1995–97).

The uncertainty in simulated annual runoff and groundwater inflow from ephemeral watersheds of the Carson Range 

caused by selection of the index model ranged from 13,000 

to 26,000 acre-feet, considerably less than the range from dry 

to wet conditions. Because bedrock type appears to affect the 

volumes of runoff and ground-water inflow from gaged and 

ungaged perennial watersheds, volumes simulated for the 

ephemeral watersheds using the appropriate index model were 

considered to be the best and most reasonable estimate.

Total mean annual ground-water inflow simulated by the 

models is 38,000 acre-feet with the addition of ground-water 

inflow from Eagle Valley and recharge from precipitation 

on eolian sand and gravel deposits, 1,700 acre-feet, and 

ground-water recharge from precipitation on the western 

alluvial fans, 500 acre-feet. The estimate of 38,000 acre-feet 

for mean annual ground-water inflow simulated from the 

watershed models, was in close agreement with that obtained 

from the chloride-balance method, 40,000 acre-feet, but was 

considerably greater than the estimate obtained from the 

water-yield method, 22,000 acre-feet from a previous study. 

The similar estimates obtained from the watershed models and 

chloride-balance method, two relatively independent methods, 

provide more confidence that they represent a reasonably 

accurate volume of mean annual ground-water inflow to 

52 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
Carson Valley. However, the two estimates are not completely 

independent because they use the same distribution of annual 

precipitation.

Annual ground-water recharge of the basin-fill aquifers 

in Carson Valley ranged from 51,000 to 54,000 acre-feet using 

estimates of ground-water inflow to Carson Valley simulated 

from the watershed models combined with estimates of other 

ground-water budget components from a previous study. 

Estimates of mean annual ground-water discharge ranged from 

44,000 to 47,000 acre-feet, including an increase of 3,000 

acre-ft/yr in the amount of net ground-water pumping from the 

estimate in a previous study.

The low range estimate for ground-water recharge, 

51,000 acre-feet per year, is most similar to the high range 

estimate for ground-water discharge, 47,000 acre-feet per year. 

Thus, an average annual volume of about 50,000 acre-feet is 

a reasonable estimate for mean annual ground-water recharge 

to and discharge from the basin-fill aquifers in Carson Valley. 

However, the results of watershed models indicate that 

significant interannual variability in the volumes of groundwater inflow is caused by climate variations. During multiyear drought conditions, the watershed simulations indicate 

that ground-water recharge could be as much as 80 percent 

less than the mean annual volume of 50,000 acre-feet per year.

Acknowledgments

The authors thank Kathy Braton of the U.S. Forest 

Service in Carson City for providing digital vegetation maps 

of the Carson Range.

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56 Precipitation, Runoff, Ground-Water Inflow, and Ground-Water Budgets, Carson Valley, Nevada and California
For more information contact:

Director, Nevada Water Science Center

U.S. Geological Survey

2730 N. Deer Run Road

Carson City, Nevada 89701

http://nevada.usgs.gov
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