GROUND-WATER FLOW AND

SIMULATED EFFECTS OF DEVELOPMENT

IN PARADISE VALLEY, A BASIN TRIBUTARY

TO THE HUMBOLDT RIVER IN

HUMBOLDT COUNTY, NEVADA

~1

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1409-F
AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY

Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the currentyear issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey 

publications released prior to the current year are listed in the most recent annual "Price and Availability List." Publications that are 

listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability 

List" are no longer available.

Reports released through the NTIS may be obtained by writing to the National Technical Information Service, U.S. Department of 

Commerce, Springfield, VA 22161; please include NTIS report number with inquiry.

Order U.S. Geological Survey publications by mail or over the counter from the offices given below.

BY MAIL 

Books

Professional Papers, Bulletins, Water-Supply Papers, Techniques of Water-Resources Investigations, Circulars, publications 

of general interest (such as leaflets, pamphlets, booklets), single 

copies of Earthquakes & Volcanoes, Preliminary Determination of 

Epicenters, and some miscellaneous reports, including some of 

the foregoing series that have gone out of print at the Superintendent of Documents, are obtainable by mail from

U.S. Geological Survey, Information Services

Box 25286, Federal Center

Denver, CO 80225

Subscriptions to periodicals (Earthquakes & Volcanoes and 

Preliminary Determination of Epicenters) can be obtained ONLY 

from the

Superintendent of Documents

Government Printing Office

Washington, DC 20402

(Check or money order must be payable to Superintendent of 

Documents.)

Maps

For maps, address mail orders to

U.S. Geological Survey, Map Distribution

Box 25286, BIdg. 810, Federal Center

Denver, CO 80225

Residents of Alaska may order maps from

U.S. Geological Survey, Earth Science Information Center

101 Twelfth Ave., Box 12

Fairbanks. AK 99701

OVER THE COUNTER 

Books and Maps

Books and maps of the U.S. Geological Survey are available 

over the counter at the following U.S. Geological Survey offices, 

all of which are authorized agents of the Superintendent of Documents.

 ANCHORAGE, Alaska 4230 University Dr., Rm. 101

 LAKEWOOD, Colorado Federal Center, Bldg. 810

 MENLO PARK, California Bldg. 3, Rm. 3128, 345 Middlefield Rd.

 RESTON, Virginia National Center, Rm. IC402, 12201 

Sunrise Valley Dr.

 SALT LAKE CITY, Utah Federal Bldg., Rm. 8105, 125 

South State St.

 SPOKANE, Washington U.S. Post Office Bldg., Rm. 135, 

W. 904 Riverside Ave.

 WASHINGTON, D.C. Main Interior Bldg., Rm. 2650, 18th 

and C Sts., NW.

Maps Only

Maps may be purchased over the counter at the U.S. Geological Survey offices:

 FAIRBANKS, Alaska New Federal Building, 101 Twelfth 

Ave.

 ROLLA, Missouri 1400 Independence Rd

 STENNIS SPACE CENTER, Mississippi Bldg. 3101
Ground-Water Flow and Simulated Effects 

of Development in Paradise Valley, 

A BasinTributary to the Humboldt River 

in Humboldt County, Nevada

By DAVID E. PRUDIC and MARC E. HERMAN

REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1409-F

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1996
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

Any use of trade names and trademarks

in this publication is for descriptive

purposes only and does not constitute

endorsement by the U.S. Geological Survey

Library of Congress Cataloging-in-Publication Data

Prudic, David E.

Ground-water flow and simulated effects of development in Paradise Valley, a basin tributary to the 

Humboldt River in Humboldt County, Nevada / by David E. Prudic and Marc E. Herman.

p. cm. (Regional aquifer system analysis Great Basin, Nevada-Utah) (United States Geological Survey 

professional paper: 1409-F)

Includes bibliographic references.

Supt. of Docs, no.: I 19.16: 1409-F

1. Groundwater flow Nevada Paradise Valley. I. Herman, Marc E. n. Title. HI. Series. IV. Series: U.S. 

Geological Survey professional paper ; 1409-F.

GB1197.7.P78 1995 95-35543 

551.49'09793'54-dc20 CIP

For sale by U.S. Geological Survey, Information Services 

Box 25286, Federal Center, Denver, CO 80225
FOREWORD

THE REGIONAL AQUIFER-SYSTEM ANALYSIS PROGRAM

The Regional Aquifer-System Analysis (RASA) Program was started in 

1978 following a congressional mandate to develop quantitative appraisals of 

the major ground-water systems of the United States. The RASA Program 

represents a systematic effort to study a number of the Nation's most 

important aquifer systems, which in aggregate underlie much of the country 

and which represent an important component of the Nation's total water 

supply. In general, the boundaries of these studies are identified by the 

hydrologic extent of each system and accordingly transcend the political 

subdivisions to which investigations have often arbitrarily been limited in the 

past. The broad objective for each study is to assemble geologic, hydrologic, 

and geochemical information, to analyze and develop an understanding of the 

system, and to develop predictive capabilities that will contribute to the 

effective management of the system. The use of computer simulation is an 

important element of the RASA studies, both to develop an understanding of 

the natural, undisturbed hydrologic system and the changes brought about in 

it by human activities, and to provide a means of predicting the regional 

effects of future pumping or other stresses.

The final interpretive results of the RASA Program are presented in a series 

of U.S. Geological Survey Professional Papers that describe the geology, 

hydrology, and geochemistry of each regional aquifer system. Each study 

within the RASA Program is assigned a single Professional Paper number, 

and where the volume of interpretive material warrants, separate topical 

chapters that consider the principal elements of the investigation may be 

published. The series of RASA interpretive reports begins with Professional 

Paper 1400 and thereafter will continue in numerical sequence as the interpretive products of subsequent studies become available.

Gordon P. Eaton 

Director

CONTENTS

iiUDHd^l* Ahatrart __ - __ __ _______ - ____________________

Introduction 

Purpose and scope 

Location and general features of study area 

Previous investigations 

Inventory of wells and springs 

Acknowledgments 

Hydrogeologic setting 

General character of hydrogeologic units 

Geologic history during late Tertiary and Quaternary

Page 

TTI j_ j_

F2 

F3 

F3 

F5 

F5 

F5 

F5 

F5

Hydrologic setting F9 

Climate ... .... .- .- ..- .- F9

Surface water F 1 1 

Ground water - F13

Basin-fill aquifer F14

Areal extent and thickness F14

Hydraulic properties F17

Hydraulic conductivity F19

Storage coefficient F21

Ground water in storage F22

Ground-water recharge F22 

Precipitation on valley floor F22 

Subsurface inflow from adjacent mountains F25 

Infiltration of water from streams F25 

Infiltration of water from Humboldt River F26 

Subsurface inflow along Humboldt River F26

Page

Ground-water discharge F26

Evapotranspiration F27

Subsurface outflow to Humboldt River Valley - F27

Subsurface outflow along Humboldt River F27

Ground-water pumpage F27

Simulation of ground-water flow F29

Digital computer model F32

General features of model F32

Stream leakage F35

Evapotranspiration F36

Initial conditions and hydraulic properties F38

Results of simulation F38

Predevelopment conditions F38

Calibration of steady-state simulations F39

Simulated ground-water flow F43

Effects of development, 1948 through 1982 F51

Selection of stress periods for simulation F51

Calibration of transient simulations F54

Aquifer response F56

Effects of reduced recharge F61

Simulated response to selected development

conditions F64

Selection of scenarios F66

Discussion of results F67

Summary and conclusions F86

CltGCl ~" ----------------- -- - « -- , ,-_.--- _p yy

ILLUSTRATIONS

Page

FIGURE 1. Map showing location of Paradise Valley study area relative to Humboldt River drainage area and Great Basin

studv area ______________________________________________________________ F2

2. Map showing general features, stream-gaging stations, and precipitation stations in and adjacent to Paradise

Valley, Humboldt County, Nevada - - F4

3. Diagram showing numbering system for wells and springs in Nevada F6

4. Map showing distribution of hydrogeologic units in Paradise Valley, Humboldt County, Nevada F10 

5 -7. Graphs showing:

5. Monthly distribution of average annual precipitation at Paradise Valley and near Winnemucca, Nevada Fll

6. Average monthly streamflows as percentage of average annual streamflow for Martin Creek and Little

Humboldt River where they enter Paradise Valley and for Humboldt River at Comus, Nevada F12

7. Annual streamflow and cumulative departure from average annual streamflow for Martin Creek where it enters

Paradise Valley, Humboldt County, Nevada, water years 1923-82 F13 

8-12. Maps showing:

8. Depth to ground water prior to large quantities of pumpage, Paradise Valley, Humboldt County, Nevada F15

9. Ground-water levels, Paradise Valley, Humboldt County, Nevada, spring 1968 F16

10. Thickness of basin fill in Paradise Valley, Humboldt Valley, Nevada F18
CONTENTS

11. Distribution of hydraulic conductivity in upper 600 feet of basin fill as determined from specific-capacity

data in Paradise Valley, Humboldt County, Nevada F20

12. Distribution of specific yield in upper 200 feet of saturated basin fill as determined from drillers' logs,

Paradise Valley, Humboldt County, Nevada F23

13. Graphs showing changes in annual ground-water pumpage, 1948-82, for Paradise Valley and adjacent

segment of Humboldt River Valley, Humboldt County, Nevada F29

14. Map showing distribution of irrigated lands and irrigation wells as of 1968, Paradise Valley, Humboldt

County, Nevada F30

15. Map showing distribution of irrigated lands and irrigation wells as of 1981, Paradise Valley, Humboldt

C ounty, Nevada - - F31

16. Schematic three-dimensional diagram of basin-fill aquifer, and same diagram with basin fill represented

by blocks for computer simulation, Paradise Valley, Humboldt County, Nevada F33

17. Map showing finite-difference grid used to simulate ground-water flow in the basin-fill aquifer, Paradise

Valley, Humboldt County, Nevada F34

18. Map showing distribution of model blocks used to simulate recharge from or discharge to streams, and

blocks assigned a constant recharge rate, Paradise Valley, Humboldt County, Nevada F37

19. Graph showing cumulative percentage of absolute differences between simulated and measured water

levels for best-fit steady-state simulation, Paradise Valley, Humboldt County, Nevada F40

20. Map showing simulated and measured ground-water levels in upper 600 feet of basin fill for period

1948-68, Paradise Valley, Humboldt County, Nevada F41

21-23. Maps showing distribution of aquifer properties used in best-fit model simulations of Paradise Valley, 

Humboldt County, Nevada:

21. Layer-one hydraulic conductivity and saturated thickness F42

22. Layer-two and layer-three transmissivities F44

23. Leakance between layers one and two and layers two and three F46 

24-26. Maps showing:

24. Simulated evapotranspiration rates and mapped phreatophyte areas, Paradise Valley, Humboldt

County, Nevada----- -- ------- -- ---- - ------ - F48

25. Water levels in model layers one, two, and three for best-fit steady-state simulation, Paradise Valley,

Humboldt County, Nevada F49

26. Ground-water level declines between 1968 and fall 1982, Paradise Valley, Humboldt County, Nevada F52

27. Graph showing cumulative percentage of absolute differences between simulated and measured water

levels, for fall seasons of 1968, 1972, 1975, and 1978, Paradise Valley, Humboldt County, Nevada F57

28. Graph showing cumulative percentage of absolute differences between simulated and measured water

levels, for fall and spring seasons, 1979-82, Paradise Valley, Humboldt County, Nevada F58

29. Map showing simulated and measured ground-water levels in upper 600 feet of basin fill for spring 1982,

Paradise Valley, Humboldt County, Nevada - F60

30. Hydrographs showing measured water levels in selected wells and simulated water levels in corresponding

model blocks from best-fit transient simulations, 1968-82, Paradise Valley, Humboldt County, Nevada - F62

31. Graphs showing cumulative change in annual ground-water discharge, recharge, and storage from results of

best-fit transient simulations, 1968-82, Paradise Valley, Humboldt County, Nevada F66

32. Maps showing water-level decline between model simulation for 14-year period 1969-82, assuming average 

streamflow rate for that period, and simulations for same 14-year period but assuming streamflow rate 

equal to average values for long-term period 1923-82 and 14-year period of lowest flow (1923-36), 

Paradise Valley, Humboldt County, Nevada - F68

33. Graphs showing water levels at six selected model blocks in layer one showing differences in simulations

caused by varying streamflow rate, Paradise Valley, Humboldt County, Nevada F70 

34-38. Maps and graphs showing response of basin-fill aquifer to selected development scenarios, Paradise Valley, 

Humboldt County, Nevada, including water-level declines after pumpage, average water-level declines in 

pumped areas, changes in rate of evapotranspiration and underflow to and from Humboldt River Valley, 

cumulative change in storage, and sources of pumped water at end of selected time periods: 

34. Scenario one: net pumpage equal to estimated rate of 36,000 acre-feet per year for 1982 and

distributed to match location of that pumpage; an additional 2,800 acre-feet per year of pumpage 

simulated in Humboldt River Valley F73 

35 Scenario two: net pumpage, 72,000 acre-feet per year, concentrated in southern end of Paradise

Valley ____________________________________________________________ F76

36. Scenario three: net pumpage, 72,000 acre-feet per year, concentrated in the northern end of Paradise

Valley -------------------------------------------------------------------------------------------------------------------- F78

37. Scenario four: net pumpage, 72,000 acre-feet per year, concentrated in central part of Paradise Valley - F82

38. Scenario five: net pumpage, 72,000 acre-feet per year, concentrated in area of evapotranspiration F84
CONTENTS vii

TABLES

Page 

TABLE 1. Description of hydrogeologic units and their general hydrologic properties in Paradise Valley, Humboldt

County Nevada ____________________________________________________________ F8

2. Estimated annual streamflow of Little Humboldt River near confluence with Humboldt River, Humboldt

County, Nevada, 1948-82 .~.~..---~-~-.--~..~..~.~~-....~.......-.-...----.......~.~.---~----~-~---~-~-~-----~--~~-~-~~~ F14

3. Comparison of basin-fill thickness at five sites in Paradise Valley, Humboldt County, Nevada, estimated using

seismic-refraction and gravity methods F19

4. Estimated specific yield of lithologies described in drillers' logs, Paradise Valley, Humboldt County, Nevada F22

5. Estimates of annual ground-water recharge and discharge for basin-fill aquifer in Paradise Valley, Humboldt

County, Nevada, and adjacent segment of Humboldt River Valley prior to large quantities of pumpage F24

6. Estimates of annual ground-water pumpage by crop type and irrigation system, Paradise Valley, Humboldt

County, Nevada---------------------------------------------------------------------------------------------------------------------------------------- F28

7. Average annual ground-water recharge and discharge for basin-fill aquifer in Paradise Valley, Humboldt

County, Nevada, and adjacent segment of Humboldt River Valley prior to large quantities of pumpage for

best-fit steady-state simulation F50

8. Estimates of net ground-water pumpage in both Paradise Valley and adjacent segment of Humboldt River Valley, 

Humboldt County, Nevada, streamflow of gaged streams, and percentage of long-term mean flow at Martin 

Creek for selected model-stress periods, 1948-78 F53

9. Estimates of net ground-water pumpage in both Paradise Valley and adjacent segment of Humboldt River Valley, 

Humboldt County, Nevada, streamflow of gaged streams, and percentage of long-term mean flow at Martin 

Creek for 3-month periods during 1979-82 F55

10. Estimated and simulated annual streamflow of Little Humboldt River near confluence with Humboldt River,

Humboldt County, Nevada, 1948-82 F56

11. Simulated ground-water budgets for basin-fill aquifer in Paradise Valley, Humboldt County, Nevada, for

selected years during 1948-82 - F59

12. Simulated ground-water budgets for basin-fill aquifer in Paradise Valley, Humboldt County, Nevada, for

three-month periods in 1981 - F67

13. Description of simulations for selected development scenarios, Paradise Valley, Humboldt County, Nevada F71 

14-18. Simulated ground-water budgets after selected periods of pumping, Paradise Valley, Humboldt County, 

Nevada, for:

14. Development scenario one F75

15. Development scenario two F80

16. Development scenario three F81

17. Development scenario four F86

18. Development scenario five F87 

19. Summary of hydrologic effects on basin-fill aquifer in Paradise Valley, Humboldt County, Nevada after 50

years of pumping, using five selected development scenarios F88
Vlll CONTENTS

CONVERSION FACTORS AND ABBREVIATIONS

Multiply By To obtain

acre 0.4047 

acre-foot (acre-ft) 1,233

acre-foot per year (acre-ft/yr) 0.001233

foot (ft) 0.3048

foot per foot (ft/ft) 1.000

foot per second (ft/s) 0.3048

foot per day (ft/d) 0.3048

foot per year (ft/yr) 0.3048

cubic foot per second (ft3/s) 0.02832

gallon per minute (gal/min) 0.06309

inch (in.) 25.4

mile (mi) 1.609

pound per cubic foot (Ib/ft3) 16.02

square mile (mi2) 2.590

square hectometer

cubic meter

cubic hectometer per year

meter

meter per meter

meter per second

meter per day

meter per year

cubic meter per second

liter per second

millimeter

kilometer

kilogram per cubic meter

square kilometer

Sea level: In this report "sea level" refers to the National Geodetic Vertical Datum of 1929 a 

geodetic datum derived from a general adjustment of the first-order level nets of 

both the United States and Canada, formerly called "Sea-Level Datum of 1929."
REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN 

PARADISE VALLEY, A BASIN TRIBUTARY TO THE HUMBOLDT RIVER IN

HUMBOLDT COUNTY, NEVADA

By DAVID E. PRUDIC AND MARC E. HERMAN

ABSTRACT

Ground-water flow in Paradise Valley, a basin tributary to 

the Humboldt River in north-central Nevada, was studied as 

part of a regional aquifer-system analysis in the Great Basin 

region of Nevada, Utah, and adjacent States. The valley was 

chosen because it is typical of the many basins that drain into 

the river. The principal technique used to analyze ground-water 

flow in Paradise Valley was with a computer program that 

simulates ground-water flow in three dimensions. Results from 

computer simulations are used to illustrate the possible effects 

that increased pumpage could have on ground-water flow in 

Paradise Valley and, by analogy, in other similar basins tributary to the Humboldt River.

Basin fill, which consists mostly of discontinuous lenses of 

gravel, sand, silt, and clay, and lesser quantities of volcanic deposits, forms the primary aquifer in Paradise Valley. The deposits may exceed 8,000 feet in thickness near the center of the 

valley but pinch out around the valley edges where consolidated rocks are exposed. The elongate valley (at most 13 miles 

wide and about 40 miles long) trends northeasterly and is 

bounded by mountains on the north, west, and east sides; it 

merges with Humboldt River Valley to the south.

Recharge to the basin-fill aquifer is primarily from streams 

that enter the valley from the surrounding mountains and from 

two streams that enter the northeastern part of the valley from 

adjacent areas by way of narrow canyons. Estimated average 

annual streamflow into the valley is about 72,000 acre-feet. 

During periods of high streamflow, surface water flows to sand 

dunes that cross the southern end of the valley, forming a lake 

that remains until the water seeps into the ground, is evaporated, or is drained to the Humboldt River if a temporary channel is dredged through the dunes.

Discharge from the basin-fill aquifer is primarily from 

evapotranspiration in the valley lowlands adjacent to streams. 

Results of a simulation of conditions prior to ground-water 

pumpage indicates that southward ground-water flow from 

Paradise Valley into Humboldt River Valley was only 1,800 

acre-feet per year, whereas as much as 1,300 acre-feet per year 

may have been flowing northwestward from Humboldt River 

Valley into Paradise Valley near Golconda Butte.

Ground-water pumpage in Paradise Valley increased slowly 

from about 200 acre-feet in 1948 to 6,800 acre-feet in 1970. 

Pumpage increased dramatically in the 1970's when the southern end of the valley was determined to be an ideal location for 

growing potatoes; in 1982 pumpage totaled about 44,000 acrefeet. The increase in pumpage altered the direction of groundwater flow, which prior to development was from the margins 

of the valley toward its axis and then southward toward the 

Humboldt River. As of 1982, ground-water flow in Paradise 

Valley was toward a water-table depression near the heavily 

pumped area in the southern end of the valley.

Five different development scenarios were simulated in 

which pumpage was concentrated in different areas of Paradise 

Valley. The purpose of these simulations was to illustrate the 

effects of different ground-water development patterns on 

ground-water flow in Paradise Valley. The first scenario assumed pumpage equal to net pumpage (total pumpage less 

what was estimated to return to the aquifer) of about 39,000 

acre-feet per year estimated for 1982: 36,000 acre-feet per year 

in Paradise Valley and about 2,800 acre-feet per year in adjacent Humboldt River Valley. After 300 years of pumpage, results showed water-level declines in the southern part of 

Paradise Valley of more than 200 feet. These declines were 

near the area where pumpage was most concentrated in 1982. 

Ground-water flow from Paradise Valley to Humboldt River 

Valley had decreased 1,700 acre-feet per year, whereas groundwater flow from Humboldt River Valley into Paradise Valley 

increased 7,400 acre-feet per year. Net pumpage for the other 

four scenarios was set equal to 72,000 acre-feet per year, but 

the location of pumpage in Paradise Valley changed. The distribution of pumpage in the valley for each simulation included, 

respectively, wells concentrated at the southern end; wells concentrated at the northern end; wells concentrated along the 

central part; and wells distributed throughout the area of 

evapotranspiration prior to pumpage. Concentrating pumpage 

at either end of the valley resulted in simulated water-level declines that locally exceeded 400 feet after only 75 years of 

pumping in the northern end and after 100 years of pumping in 

the southern end. In addition, pumpage concentrated at the 

southern end of the valley produced a reversal of net flow between Paradise Valley and Humboldt River Valley. Prior to 

pumping, the estimated net flow was 500 acre-feet per year 

from Paradise Valley into Humboldt River Valley, whereas after a simulated period of 50 years, the net flow was 15,000 

acre-feet per year from Humboldt River Valley into Paradise 

Valley. Simulations in which pumpage was concentrated in the 

central part of the valley and distributed throughout the area 

of evapotranspiration resulted in water-level declines of generally less than 200 feet after 300 years; both simulations nearly 

reached a new equilibrium and captured much of the 

predevelopment evapotranspiration.

Fl
F2 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

In conclusion, concentrating pumpage in the northern and 

southern areas of Paradise Valley might produce large waterlevel declines without effectively reducing natural discharge in 

the central part of the valley. Concentrating pumpage in the 

southern end might also induce flow from Humboldt River Valley and, depending on the quantity of pumpage, might ultimately affect flow in the river.

INTRODUCTION

Paradise Valley, a basin tributary to the Humboldt River in north-central Nevada (fig. 1), was 

chosen as one of several areas to be studied in detail as part of the Great Basin Regional Aquifer1200 115°

40°

35°

Paradise

Valley 

study area

CALIFORNIA

ARIZONA

100 MILES

100 KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000 and 1:250,000

Albers Equal-Area Conic projection

Standard parallels 29°30' and 45°30', central meridian -114°

EXPLANATION

Boundary of Great Basin study area

 Boundary of Humboldt River drainage area

FIGURE 1. Location of Paradise Valley study area relative to Humboldt River drainage area and Great Basin

study area.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F3

System Analysis (RASA) project. The Great Basin 

RASA project includes much of Nevada, the western 

half of Utah, and small parts of Arizona, California, Oregon, and Idaho. The purpose and objectives 

of the Great Basin RASA project are discussed by 

Harrill and others (1983). Paradise Valley was chosen because it has characteristics similar to those 

of many basins that drain to the Humboldt River, 

and because recent increases in ground-water 

pumping in Paradise Valley have produced a water-table decline of as much as 80 ft. The watertable decline allowed for an improved calibration of 

a computer model.

The Humboldt River begins in northeastern Nevada (fig. 1) and flows in a westerly to southwesterly direction across the north- to northeasttrending mountains and basins that characterize 

the Great Basin Region of Nevada and Utah. The 

river ends at the Humboldt Sink in western Nevada (fig. 1), but during years of exceptionally high 

runoff, some of the accumulated inflow to the Humboldt Sink may spill into the neighboring Carson 

Sink. The Humboldt River has a drainage area of 

16,800 mi2 and includes 33 basins (Scott and others, 1971, p. 31). Because the river and its alluvium 

connect many of the basins, its drainage area can 

be considered one large regional system. Instead of 

analyzing the entire system, one basin was selected 

to illustrate the possible effects of ground-water development in a tributary basin on the water resources of the Humboldt River.

PURPOSE AND SCOPE

The purposes of this report are to describe and 

analyze the ground-water flow system in Paradise 

Valley and to evaluate, by using a ground-water 

flow model, the response of the flow system to selected development scenarios. The selected scenarios are designed to be compared with results 

from similar investigations in other selected basins 

within the Great Basin RASA study area.

Field work began in March 1981 and continued 

through December 1982. The work consisted of (1) 

canvassing most of the wells in the valley, (2) making multiple measurements of water levels in wells 

to ascertain seasonal and long-term trends and 

gathering previously collected data, (3) obtaining 

estimates of pumpage, (4) mapping land use and 

types of crops, and estimating water use by crop 

type, (5) mapping geologic and hydrologic features, 

and (6) making detailed gravity and seismic measurements for the purpose of determining the

thickness of basin fill. In addition, continuous 

streamflow data were collected at three sites in or 

near the study area during and before the study as 

part of the stream-gaging network in Nevada. The 

gravity data are presented by Schaefer and others 

(1986) and Schaefer (1988).

The principal technique used to analyze groundwater flow in Paradise Valley was a finite-difference model (McDonald and Harbaugh, 1988) that 

simulates flow in three dimensions. The model was 

used to evaluate the aquifer properties and to determine the response of the flow system to five different development scenarios, including the 1982 

distribution of pumpage. Each scenario was simulated for a pumping period that ranged from 75 to 

300 years in duration, and for a recovery period of 

300 years. Similar scenarios were used for the 

other basins studied as part of the Great Basin 

RASA project. The long time periods were used to 

determine how long each basin took to reach a new 

state of equilibrium.

LOCATION AND GENERAL FEATURES OF STUDY AREA

The study area (fig. 2) includes all or part of two 

hydrographic areas as defined by Rush (1968): 

Paradise Valley (area number 69) and part of the 

Winnemucca segment of Humboldt River from 

Golconda to Winnemucca (area number 70); the latter is referred to as the Humboldt River Valley in 

this report. The boundary between the two areas is 

shown in figure 2.

Paradise Valley is long and narrow, extending 

about 40 mi northward from the Humboldt River 

near Winnemucca (fig. 2). The valley is bordered by 

the Santa Rosa Range and the Bloody Run Hills to 

the west, the Santa Rosa Range and low-lying volcanic hills to the north and northeast, the Hot 

Springs Range to the east, and Humboldt River 

Valley to the south. The valley has a maximum 

width of 13 mi and an area of about 330 mi2 . Humboldt River Valley is included in this study because 

ground-water flow is not impeded between the two 

areas. The Humboldt River generally flows from 

east to west through the study area and is bordered on the south by the Sonoma Range.

The mountain ranges in the study area trend 

generally northward. Altitudes of the crests range 

from about 6,500 ft above sea level in the Hot 

Springs Range to more than 9,000 ft in the Santa 

Rosa Range, where Granite Peak reaches an altitude of 9,779 ft. The altitude of the valley floor 

near the town of Paradise Valley is about 4,520 ft.
F4 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45' 117°30' 117°15'

41°45'

41°30'

41°00'

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

Universal Mercator projection

zone 11 EXPLANATION

10 MILES

0 10 KILOMETERS

Approximate extent of ephemeral 

Gumboot Lake

 Boundary of study area

 Boundary between Paradise

Valley and Winnemucca segment 

of Humboldt River Valley-Dotted 

where approximately located

A

A

A 

<$>

O

Stream-gaging station 

Streamflow measurement site 

Partial-record gaging station 

Precipitation station

Flowing hot well N37E39 03DC1-

Letters and numbers identify location 

(see fig. 3)
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F5

The valley floor gently slopes southward to Humboldt River Valley. The altitude of the Humboldt 

River near Golconda is about 4,340 ft; near Winnemucca, it is about 4,260 ft.

PREVIOUS INVESTIGATIONS

The earliest comprehensive study of ground-water flow in Paradise Valley was by Loeltz and others (1949). Their study provided information during 

a period of little pumpage. The distribution of 

gravel deposits in the valley was described by 

Bredehoeft (1963). He also presented estimates of 

hydraulic conductivity for stream-associated gravel 

deposits in the lower Humboldt River drainage basin. Another comprehensive study of the valley was 

reported by Harrill and Moore (1970); it included a 

period when ground water was being developed as 

a supplemental source for the irrigation of meadows and alfalfa. They also reported estimates of 

streamflow losses in the valley. A Bouguer gravity 

map of the valley and water-chemistry data for selected wells were included in a geothermal-resource 

appraisal of the valley by Flynn (1981). Philip 

Cohen authored several reports pertaining to aquifer characteristics and water resources along the 

reach of the Humboldt River that forms the southern boundary of this study (Cohen, 1961, 1962, 

1963a, b, 1964; Cohen and others, 1965).

Although no comprehensive study on the basinfill aquifer in Paradise Valley has been published 

since 1970, data on ground-water levels, streamflows into the valley, and crop types and the number of active irrigation wells have been routinely 

collected by the Nevada Division of Water Resources and by the U.S. Geological Survey. These 

data were used in this study.

INVENTORY OF WELLS AND SPRINGS

Data on most wells, including location, altitude, 

water levels, depth, diameter, lithologic descriptions (when available), and construction, were entered into the U.S. Geological Survey data-base 

system known as WATSTORE (National Water Data 

Storage and Retrieval system). Data about springs 

and stream-measuring sites in or near Paradise 

Valley also are stored on the WATSTORE system.

FIGURE 2. General features, stream-gaging stations, and precipitation stations in and adjacent to Paradise Valley, Humboldt County, Nevada.

The local site-identification system used in this 

report is based on an index of hydrographic areas 

in Nevada (Rush, 1968) and the rectangular subdivision of the public lands referenced to the Mount 

Diablo base line and meridian. Each site designation consists of four units: The first unit is the hydrographic area number. The second unit is the 

township, preceded by an N or S to indicate location north or south of the base line. The third unit 

is the range, preceded by an E to indicate location 

east of the meridian. The fourth unit consists of 

the section number and letters designating the 

quarter section, quarter-quarter section, and so on 

(A, B, C, and D indicate the northeastern, northwestern, southwestern, and southeastern quarters, 

respectively), followed by a number indicating the 

sequence in which the site was recorded (fig. 3). 

For example, well 69 N40E39 01AAA1 is in Paradise Valley and is the first well recorded in the 

northeast quarter of the northeast quarter of the 

northeast quarter of section 1 in Township 40 

North and Range 39 East, Mount Diablo base line 

and meridian.

ACKNOWLEDGMENTS

The residents of Paradise Valley were very cooperative in allowing access to their wells. Winnemucca Farms also provided detailed information on 

well construction, well tests, and lithologic logs of 

their wells. Nevada First Corporation, Winnemucca 

Farms, and many other ranchers provided information about the acreage and types of crops irrigated, 

and the methods and approximate rates used to irrigate the crops. Roger Johnson (Nevada Division 

of Water Resources) provided water-level measurements of numerous wells in the valley and pumpage estimates determined from the number of 

irrigation wells and types of crops irrigated. 

Donald Schaefer (U.S. Geological Survey) did the 

seismic refraction profiles at five locations and interpreted the data. He also provided instruction 

and assistance in estimating the thickness of basin 

fill from the gravity data.

HYDROGEOLOGIC SETTING

GENERAL CHARACTER OF HYDROGEOLOGIC UNITS

Hydrogeologic units in the study area are divided into two groups on the basis of their ability 

to store and transmit water. The first group consists of basin fill that includes dune sand; older
F6 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

and younger alluvium of gravel, sand, silt, and 

clay; and lesser quantities of lacustrine and volcanic deposits. In places, the older alluvium is consolidated. The second group consists of rocks 

exposed in the surrounding mountains and includes indurated and metamorphosed sediments,

igneous intrusives, and lava flows. In this report, 

rocks in the surrounding mountains are referred to 

collectively as consolidated rocks and are presumed 

to underlie the basin fill. The hydrogeologic units 

and their general hydrologic properties are described in table 1 and are based on work by

T. 40 N.

6

7

18

19

30

31

5

8

17

20

29

32

4

9

16

21

28

33

3

10

15

22

27

34

2

11

14

23

26

35

12

13

24

25

36

B

Paradise Valley (69) 

69 N40E39 01AAA1

_______\

B -A- iU? 1-

D

D

R. 39 E.

T. 40 N.

T. 39 N.

T. 38 N.

T. 37 N.

R. 37 E. R. 38 E. R. 39 E. R. 40 E. 

FIGURE 3. Numbering system for wells and springs in Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F7

Willden (1964) and Harrill and Moore (1970). Distribution of hydrogeologic units is shown in figure 4.

In general, the consolidated rocks have a low porosity and permeability that restricts their ability 

to store and transmit water. However, the Tertiary 

lava flows, along the northern edge of Paradise 

Valley (fig. 4) and in the highlands over which the 

tributaries to Martin Creek and the Little Humboldt River flow, can store and transmit water because they are commonly jointed and fractured. 

These rocks may underlie the basin fill at the 

northern end of the valley (Loeltz and others, 1949, 

p. 26). Drillers' logs for a few of the deeper wells 

(400 to 650 ft) reported lava rocks between unconsolidated deposits of gravel, sand, silt, and clay, 

but it is uncertain whether these lava flows are 

connected to those exposed in the mountains. The 

quantity of water available in lava flows beneath 

Paradise Valley is unknown. Reported yields of 

wells that encountered lava flows are less than 500 

gal/min. Wells completed in the unconsolidated deposits in the basin fill generally yield less than 500 

gal/min along the margins of the valley and more 

than 3,500 gal/min in the central part.

A basalt flow (or flows) extends eastward from 

Winnemucca Mountain in the extreme southwestern part of the valley (fig. 4). These basaltic rocks 

are Quaternary in age (Stewart, 1980, p. 108) and 

may overlie older alluvium, as indicated by basinfill thicknesses estimated from gravity and seismic 

surveys (see section titled "Areal Extent and Thickness"). Even if the basalt extends into the basin fill 

at depth, the rocks are well jointed and fractured 

and may not restrict movement of ground water in 

the area.

The basin fill generally has a much higher porosity and permeability than the consolidated 

rocks, except perhaps some of the basalts, and thus 

stores and transmits much greater quantities of 

water. These deposits constitute the principal aquifers in the study area.

GEOLOGIC HISTORY DURING LATE TERTIARY AND 

QUATERNARY TIME

A major change in the tectonic activity of Nevada began about 17 million years ago when major 

structural forces changed from compressional to 

tensional (Stewart, 1980, p. 110). Block faulting 

caused by extension produced basins and ranges 

that are characteristic of the present-day topography throughout Nevada. The movement along the 

predominately northeast-trending normal faults resulted in relative uplift of linear segments to form 

mountains and a relative sinking of adjacent segments to form basins. Vertical displacement along 

the complex system of faults is generally 6,000 to 

15,000 ft (Stewart, 1980, p. 110). In addition to the 

northeast-trending normal faults, six northwesttrending lineaments have been identified by Sales 

(1966) in the vicinity of Paradise Valley. He interpreted the lineaments to be shears caused by tensional strike-slip faulting. These shears have 

structurally altered the rocks in the mountain 

blocks and may extend beneath the basin fill.

At about the same time (17 million years ago), 

the volcanic rock composition changed from generally rhyolitic to generally basaltic (Stewart, 1980, 

p. 102). The basalt flows at the northern end of 

Paradise Valley preceded the basin and range 

faulting (Loeltz and others, 1949, p. 29). However, 

the basalt flow at the southwestern end of the valley (fig. 4) has been dated at less than 6 million 

years old (Stewart, 1980, p. 108) and, as previously 

noted, may overlie older alluvium.

Movement along the faults that formed the 

mountains and basins has probably continued intermittently throughout the past 17 million years, 

and with the formation of the mountains came the 

continuing accretion of basin fill in the valleys. 

These deposits consist of a variety of fluvial and 

lacustrine units and contain variable quantities of 

volcanic deposits.

The present Humboldt River drainage system 

developed prior to Lake Lahontan, a Pleistocene 

lake that formed over many basins in northwestern 

Nevada (Loeltz and others, 1949, p. 29). During the 

Pleistocene, Lake Lahontan extended into Paradise 

Valley at least twice, and each time it deposited a 

thin layer of lake sediments in the lower end of 

Paradise Valley (Loeltz and others, 1949, p. 30). 

Both the Little Humboldt and Humboldt Rivers deposited sediments in their channels upstream from 

the lake and formed deltas where they entered the 

lake. After the last retreat of Lake Lahontan in 

late Pleistocene time, both rivers began eroding 

sediments previously deposited and the Humboldt 

River developed meander scrolls and oxbow lakes 

in its flood plain (Loeltz and others, 1949, p. 30). 

Sand dunes drifted across the southern end of 

Paradise Valley and periodically blocked the flow of 

the Little Humboldt River. How often the cycle of 

deposition and erosion has occurred in the valley 

as a result of changes in stages of lakes in the area 

is uncertain. However, many cycles of wet and dry 

periods may have occurred over the past several 

million years.
F8 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

TABLE 1. Description of hydrogeologic units and their general hydrologic properties in Paradise Valley,

Humboldt County, Nevada

[Modified from Harrill and Moore (1970, table 2)]

5

Bc/5

c/5

>"

<3

Z

|

ID

a

C/5

Mc/5

W

Z

M 

U

3o

ffi

z

y

o

a

^j

z

y 8

HH

W

£

Z

U

g

1&H

Hydrogeologic

unit

Dune sand

Humboldt River

flood-plain

deposits

Younger basin

fill

Older basin fill

Estimated

thickness

(feet)

0-75

0-20

0-150±

0-8,000±?

Lithology

Sand, medium-grained

and well-sorted.

Gravel, sand, silt, and

clay, poorly sorted to

well-sorted. Contains

thin layers of volcanic

ash and windblown

material.

Interbedded sand,

gravel, silt, and clay,

poorly sorted to wellsorted. Deposits form

lenticular bodies.

Includes lacustrine

deposits.

Gravel, sand, silt, and

clay, poorly sorted to

well-sorted. Partially

consolidated

(cemented) locally and

at depth. Deposits at

depth in center of

valley generally

moderately to well

sorted. Some lacustrine

deposits may be

present.

Occurrence

Eolian deposits at south end

of Paradise Valley, where

dunes obstruct channel of

Little Humboldt River.

Along Humboldt River,

includes coarse-grained

channel deposits and finegrained deposits in oxbow

lakes, drainage channels,

and other depressions.

Primarily stream-channel

deposits in center of

Paradise Valley; includes

some slope wash and

ephemeral stream deposits

around margin of Paradise

Valley. Superficial amounts

of lacustrine deposits

associated with Gumboot

Lake. Underlain by more

extensive lacustrine

deposits associated with

Lake Lahontan in southern

part of Paradise Valley and

parts of Humboldt River

Valley.

Along margin of Paradise

Valley, primarily as fan

deposits; also slope wash,

talus, and upland alluvial

surfaces. Fan deposits have

been dissected by younger

stream channels. Occurs at

depth in center of Paradise

Valley primarily as streamchannel deposits. Deposits

may overlie basin fill of

older age not exposed in

area.

General hydrologic properties

Porosity estimated at 20 to 30

percent; permeability

moderate to high. Water

readily infiltrates from

surface to saturated zone;

functions as recharge area

when Gumboot Lake is

formed.

Sand and gravel deposits are

highly permeable and finer

grained deposits are

relatively impermeable.

Recharge is largely by

seepage from streams and

by overbank flooding. Unit

stores and transmits large

amounts of water.

Sand and gravel deposits are

highly permeable and can

yield large quantities of

water to wells. Streamchannel deposits form most

productive units. Finer

grained or poorly sorted

deposits are less capable of

yielding water to wells.

Sand and gravel deposits

associated with buried

stream channels are highly

permeable and readily yield

water to wells. Finer

grained deposits generally

have low permeability and

do not transmit large

quantities of water.

Porosity and permeability

may decrease with depth

due to compaction by

overburden.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F9

TABLE 1. Description of hydrogeologic units and their general hydrologic properties in Paradise Valley,

Humboldt County, Nevada Continued

s

05

05

S

<

§

w

5

P

a

>

<

b

w

05 ^

o <i

w 2 U H

hi w

w P

u

ffi 

a

ID 05

0 P 

0< O

ffi w P u

U H

05 U

05 p<

^ U

£

a

o

D

o

H ~

z ^

^ w pi eu

PQ

^

U

Hydrogeologic

unit

Basalt flows

Volcanic rocks

Intrusive rocks

Metamorphic

rocks

Sedimentary

rocks

Estimated

thickness

(feet) Lithology

Vesicular olivine basalt,

well-jointed.

Primarily rhyolite,

dacite, andesite, and

basalt. Includes some

interbedded

sedimentary rocks.

Mostly granodiorite.

Primarily phyllite, slate,

quartzite, and slightly

metamorphosed

mudstone; some

calcareous shale,

calcareous sandstone,

and lenses of limestone

and dolomite.

Sequences of quartzite,

chert, limestone,

dolomite, sandstone,

shale, and

conglomerate.

Interstratified volcanic

deposits present in

parts of section.

Occurrence

Near confluence of Little

Humboldt and Humboldt

Rivers in extreme southwest

corner of Paradise Valley.

Possibly overlies older

basin-fill deposits.

Primarily at north end of

Paradise Valley. May extend

beneath or into basin fill.

Lesser amounts are

exposed along margins of

Santa Rosa and Hot Springs

Ranges and Osgood

Mountains.

Exposed primarily along core

of Santa Rosa Range.

Mostly along flanks of Santa

Rosa Range and Bloody

Run Hills. Localized

exposures in Hot Springs

Range and northeastern end

of Paradise Valley.

Predominant rock type in Hot

Springs Range and Osgood

Mountains.

General hydrologic properties

Basalt is well fractured and,

where saturated, can allow

water to transmit through it.

However, basalt flows are

generally above saturated

zone.

Commonly have little or no

interstitial porosity, except

where highly vesicular. May

transmit water through

joints and zones between

basalt flows.

Virtually no interstitial

porosity and permeability;

may transmit small

quantities of water where

fractured and weathered.

Very low porosity and

permeability; some water

may be transmitted along

fractures.

Generally have low

interstitial porosity and

permeability. May transmit

some water along fractures

or where solution features

have developed in carbonate

rocks.

HYDROLOGIC SETTING

CLIMATE

The climate of Paradise Valley is arid to semiarid, has large diurnal fluctuations in temperature, 

is strongly influenced by the prevailing westerly

winds, and is largely controlled by the orographic 

effect of the Sierra Nevada, which are approximately 150 mi to the west. Warm moist air masses 

from the Pacific Ocean are forced aloft at the Sierra Nevada causing the air masses to cool and 

moisture to condense, resulting in heavy precipitation. Consequently, the air masses moving eastward across western Nevada and the study area
F10 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45' 117°30'

41°30'

41°00'

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

EXPLANATION

Dune sand

I Humboldt River floodplain deposits

_J Younger basin fill 

H Older basin fill 

I Basalt flows 

I Volcanic rocks 

| Intrusive rocks 

_j Metamorphic rocks 

	Sedimentary rocks

Boundary of study 

area

Boundary between 

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

FIGURE 4. Distribution of hydrogeologic units in Paradise Valley, Humboldt County, Nevada. Geology from Harrill and

Moore (1970, pi. 1) and Willden (1964, pi. 1).
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY Fll

are usually moisture deficient. Local mountains 

surrounding Paradise Valley have a similar but 

somewhat lesser effect on the local climate. The 

valley floor commonly receives less moisture than 

do the mountains. Daily temperature fluctuations 

of as much as 40°F are not uncommon. The mean 

daily temperature is slightly below 50°F. The maximum summer temperature may exceed 100°F, and 

the winter minimum may drop below 0°F.

Annual precipitation at the town of Paradise 

Valley in the northern end of the valley averaged 

9.43 in. for the period 1955-82. Annual precipitation at Winnemucca, which is at the southwestern 

corner of the study area, averaged 8.07 in. for the 

same period and 8.37 in. for the 112-year period 

1871-1982. The difference in precipitation between 

the two stations is attributed to differences in altitude and variations in winter-storm tracks. Precipitation in the mountains usually exceeds 20 in. 

annually (Hardman, 1936; Harrill and Moore, 

1970, p. 12).

Almost half of the average yearly precipitation 

falls from November through February (fig. 5) and 

is usually in the form of snow. The period of July 

through September usually has the least quantity 

of precipitation. Summer precipitation generally is 

the result of localized thunderstorms of short duration and high intensity.

20

15

10

A. Paradise Valley, 1955-82

20

g 15

10

B. Near Winnemucca, 1871-1982

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

Figure 5. Monthly distribution of average annual precipitation (A) at Paradise Valley (1955-82) and (B) near 

Winnemucca (1871-1982), Nevada.

SURFACE WATER

The two major streams in Paradise Valley are 

Martin Creek and the Little Humboldt River (fig. 

2). Martin Creek enters the valley through a narrow canyon at the northeastern corner, about 6 mi 

northeast of the town of Paradise Valley. The Little 

Humboldt River enters the valley by way of a narrow passage cut through the northern end of the 

Hot Springs Range. The two streams join through a 

series of channels about halfway through the valley. The Little Humboldt River joins the Humboldt 

River at the southwest corner of Paradise Valley. 

During periods of high runoff, water flows as far as 

the sand dunes (fig. 2) that block the channel of 

the Little Humboldt River near the southern end of 

the valley. Water collects behind the sand dunes to 

form Gumboot Lake, which remains until the water 

seeps into the ground, is evaporated, or a channel 

is dredged through the dunes.

Numerous streams begin on the eastern and 

southern slopes of the Santa Rosa Range and flow 

generally eastward or southward to the valley 

floor. Many of these streams join Big Cottonwood 

Creek, which flows along the western side of the 

valley floor, parallel to Martin Creek and Little 

Humboldt River (fig. 2). Most streams are perennial in the mountains but become intermittent in 

the valley, particularly during the late summer and 

fall. Runoff usually reaches the valley floor from 

late winter to early summer, where it is diverted 

for irrigation. Streams that begin in the Bloody 

Run Hills along the southwestern margin of the 

valley seldom flow to the valley floor, but they do 

reach the bordering fans during the late winter 

and early spring. Streams that head in the lower 

and drier Hot Springs Range on the eastern side of 

the valley are intermittent, and runoff occurs only 

after major storms.

A gaging station that continuously records 

stream stage has been operated on Martin Creek 

where it enters Paradise Valley since October 1921, 

although records are incomplete until 1922. Gaging 

stations also have been operated on Little 

Humboldt River where it enters Paradise Valley 

from October 1921 to June 1928 and continuously 

since October 1943, and on Humboldt River near 

Comus (about 5 mi east of Golconda) intermittently 

from October 1894 to September 1926 and continuously since October 1945. Locations of these gaging 

stations are shown in figure 2. Streamflow data for 

these stations prior to water year 1961 (water 

years are from October 1 through September 30) 

are published in U.S. Geological Survey Water-
F12 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

Supply Papers 1314 and 1734 (1960 and 1963, respectively); data for water years 1961-83 are published in annual volumes of Water Resources Data 

for Nevada (U.S. Geological Survey, 1962-84).

Most of the streamflow that enters Paradise Valley is runoff from snowmelt (Harrill and Moore, 

1970, p. 41). Greatest streamflows are generally 

from March through June (fig. 6), whereas the 

least quantities are during August through October.

Peak discharge for Humboldt River near Comus 

is generally later in the year than either Martin 

Creek or Little Humboldt River where they enter 

Paradise Valley (fig. 6). The delay in peak discharge of Humboldt River near Comus is caused by

A. Martin Creek

B. Little Humboldt River

C. Humboldt River

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

Figure 6. Average monthly streamflows as percentage of 

average annual streamflow for (A) Martin Creek where it 

enters Paradise Valley, (B) Little Humboldt River where 

it enters Paradise Valley, and (C) Humboldt River at 

Comus, Nevada. Average monthly values are based on 60 

years of record (1923-82) for Martin Creek, 28 years 

(1944-71) for Little Humboldt River, and 37 years (1946- 

82) for Humboldt River.

later snowmelt from high mountainous areas in the 

upper Humboldt basin near Elko (fig. 1). Similarly, 

the slight delay in peak discharge for Martin Creek 

compared with Little Humboldt River is caused by 

later snowmelt from high altitudes in the Martin 

Creek drainage area.

Average annual streamflow at the Martin Creek 

gage for water years 1923-82 (a 60-year period) 

was 23,000 acre-ft/yr. The largest annual streamflow was 64,000 acre-ft, in 1952 (fig. 7A). Streamflow was generally below average for water years 

1923-42 as shown by the downward slope on the 

graph of cumulative departure from average (fig. 

75). Between water years 1969 and 1982, streamflow at the Martin Creek gage was generally above 

average.

Variations in annual discharge of Little Humboldt River for water years 1946-82 are similar to 

those for Martin Creek except after 1975, when 

Chimney Reservoir (location shown in fig. 2), 11 mi 

upstream from the gage on Little Humboldt River, 

began storing runoff. Average annual streamflow 

at the Little Humboldt River gage for a 45-year period of record spanning 1921-82 was 18,000 acreft/yr.

Streamflow usually reaches the southern end of 

Paradise Valley during spring snowmelt, but on the 

average Gumboot Lake contains appreciable water 

only about once in 5 years (Harrill and Moore, 

1970, p. 81). Relatively large lakes formed three 

times between 1950 and 1982 (in 1952, 1958, and 

1969) when the annual combined discharge for 

Martin Creek and Little Humboldt River exceeded 

70,000 acre-ft/yr. Large lakes also formed in 1983 

and again in 1984 both of which were years of abnormally high streamflow.

Prior to development, water flowed from Paradise Valley to the Humboldt River only when the 

sand dunes were breached. Such occurrences were 

recorded in 1890, 1907, 1910, and 1914 (Harrill 

and Moore, 1970, p. 69). Beginning in the early 

1950's, the lake was drained by dredging a channel 

through the dunes so flooded lands could be used 

for agriculture. Flow in the channel of Little Humboldt River below the sand dunes was observed in 

12 of the 30 years between 1953 and 1982 (table 2). 

Streamflow estimates ranged from no flow for several years to 33,000 acre-ft in 1958.

The Humboldt River is the largest stream in the 

study area. Average annual discharge at a gage 

near Comus (location shown in fig. 2) for a 68-year 

period of record spanning water years 1894-1982 is 

about 214,000 acre-ft/yr (U.S. Geological Survey, 

1983, p. 170). Annual streamflow ranged from as
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F13

little as 27,000 acre-ft during water year 1920 to 

688,000 acre-ft during water year 1907. More than 

1,000,000 acre-ft of streamflow was estimated during water year 1983 (U.S. Geological Survey, 1984, 

p. 148).

GROUND WATER

Ground water in Paradise Valley and the adjacent Humboldt River Valley originates as precipitation. Recharge to ground water is primarily by 

percolation of precipitation, infiltration of streamflow, and percolation of irrigation water.

Most of the readily available ground water in 

the study area occurs in unconsolidated deposits

(basin fill) under both unconfined (water-table) and 

confined conditions. In general, water levels in the 

central and southern parts of Paradise Valley do 

not vary between adjacent wells of different 

depths, suggesting little vertical flow. In the northern end, however, water levels in shallow wells are 

higher than water levels in deeper wells, indicating 

a downward component of flow. Except for a flowing 

hot well in the southeastern part of the valley (see 

fig. 2), water levels in wells are at or below land 

surface. In a few localized areas, water levels in 

deeper wells are higher than shallow wells, indicating an upward flow component. These localized areas are usually near the contact between the older 

and younger alluvium (fig. 4), where lenses of silt 

and clay confine water in the underlying deposits.

 I U_ <

w

oq ID CC -I LU 

LL LL LL

^ < CO

t LU D

OVJ

70

60

50

40

30

20 

10

n

A.

_

-

-

-

-

_

i i

CO

Average annual ?

i^ discharge

CM

1

II

III

ill

\

1 1

1

1

CM

O>

CO

s

I ^~

(1 1 1

1 1

_

-

o>

CO

C3> 

Q CM

I 1

CO 00

o> 35

1

I

- T1

-

-

_

20

-20

&<% -40 

Q 2 Q

-60

- -80

-100

1920 1925 1930 1935 1940 1945 1950 1955 1960 1965

WATER YEARS

1970 1975 1980 1985

FIGURE 7. Annual streamflow (A) and cumulative departure from average annual streamflow (B) for Martin 

Creek where it enters Paradise Valley, Humboldt County, Nevada, water years 1923-82.
F14 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

TABLE 2. Estimated annual streamflow of Little

Humboldt River near confluence with Humboldt

River, Humboldt County, Nevada, 1948-82

[ , no streamflow reported]

Years

1948-52

1953

1954-57

1958

1959-68

1969

1970

1971

1972

1973

1974

1975

1976-77

1978

1979

1980

1981

1982

Period of 

observed flow 

(month/day)

spring2

3 summer

4/09-6/13

5/25-6/26

2/01-6/30

3/11-5/05

3/14-3/22

4/08-5/05

6/12-7/03

_

5/19-6/30

6/01-6/23

5/15-6/10

Estimated 

streamflow 

(acre-feet 

per year)

0

25,000

0

33,000

0

22,000

3,000

22,000

17,000

50

2,000

700

0

2,500

0

1,100

0

1,100

Estimated volumes of streamflow and 

periods of observed flow are from Roger Johnson 

(Nevada Division of Water Resources, written 

commun., 1984)

f\

Channel excavated through sand dunes 

during spring 1953 (Harrill and Moore, 1970, p. 81)

Channel excavated through sand dunes in June 

and July 1958 (Harrill and Moore, 1970, p. 81)

Depth to ground water in 1968, prior to large 

quantities of ground-water pumpage, was generally 

less than 10 ft along the valley bottom and Humboldt River (fig. 8). Depths, however, increased to 

more than 100 ft on the alluvial fans adjacent to 

the mountains. The configuration of the water 

table in 1968 is shown in figure 9.

The general direction of ground-water flow in 

Paradise Valley is from the adjacent mountains to 

the valley lowlands, then southward toward the 

Humboldt River Valley (based on the assumption 

that ground-water movement is generally perpendicular to the water-table contours). Much of the 

recharge to ground water in Paradise Valley is by 

infiltration from streams in the valley bottom; 

much of this ground water subsequently is discharged by evapotranspiration. Ground water not 

discharged by evapotranspiration flows into the

Humboldt River Valley. Ground-water flow in the 

Humboldt River Valley is generally westward and 

parallel to the river.

BASIN-FILL AQUIFER

The basin fill generally functions as one hydraulic unit, even though it consists of a mixture of discontinuous lenses of gravel, sand, silt, and clay 

with minor quantities of volcanic rocks; near the 

margins, the system also consists of heterogeneous 

mixtures of gravel and sand in a silt and clay matrix. No extensive unit that can be classified as an 

aquifer has been identified from the drillers' logs. 

Cohen and others (1965) did map a predominantly 

sand and gravel unit along the Humboldt River at 

the southern boundary of the study area. This unit 

could perhaps be considered a single aquifer. 

Bredehoeft (1963, p. 32) mapped the percentage of 

gravels in the upper 100 ft of basin fill in Paradise 

Valley and concluded that the gravels were associated with major streams. Whether the gravels 

mapped by Bredehoeft constitute a single aquifer is 

uncertain. The entire basin fill in Paradise Valley 

and adjacent Humboldt River Valley, however, can 

be considered as one aquifer and will be referred to 

as the basin-fill aquifer.

AREAL EXTENT AND THICKNESS

The contact between consolidated rocks and basin fill marks the outer boundary of the basin-fill 

aquifer in Paradise Valley and adjacent Humboldt 

River Valley. Narrow bands of alluvial deposits associated with the Humboldt River extend upstream 

and downstream from the study area and provide a 

continuous link to the Humboldt River.

Gravity surveys were used to estimate the thickness of the basin fill because wells drilled in the 

study area, which range in depth from about 15 ft 

to about 800 ft, generally do not extend into the 

consolidated rocks. The magnitude of gravity at 

any location is dependent on latitude, altitude, 

tidal effects, topography of the surrounding terrain, 

and density distribution in the subsurface (Telford 

and others, 1976, p. 14). Typically, basin fill has 

much lower densities than the adjacent and underlying consolidated rocks. This difference is used to 

estimate thickness of basin fill after the gravity 

values have been corrected for the other factors.

About 400 gravity stations were used to construct a Bouguer anomaly map of Paradise Valley
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY 

117°45' 117°30'

F15

41°30'

41°00'

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

EXPLANATION

Basin fill 

Consolidated rocks

 30 Line of equal depth to

water-Dashed where 

approximately located. Interval, 

in feet, is variable. Datum is 

land surface

__ . . Boundary of study area

 - Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

FIGURE 8. Depth to ground water prior to large quantities of pumpage (pre-1969), Paradise Valley, Humboldt County, Nevada. Modified from Harrill and Moore (1970, fig. 5) and Loeltz and others (1949, pi. 1.). In recharge areas on the apron 

at north and northwest end of valley, depth to water varies with well depth. Depth to water shown on map in these 

areas is for wells deeper than 100 feet.
F16 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45' 117°30'

41°30'

41°00'

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

EXPLANATION

Basin fill 

Consolidated rocks

 4640 Water-level contourShows altitude of groundwater level, spring 1968. 

Dashed where approximately 

located. Contour interval, in 

feet, is variable. Datum is sea 

level. Water levels in northwest 

part of valley are based on 

data for deeper wells; water 

levels in shallow wells might 

have been higher. Modified 

from Harrill and Moore 

(1970, pi. 1)

 Boundary of study area

 Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximatly located

03DC0 Flowing hot wellAbbreviated site designation 

is indicated

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

FIGURE 9. Ground-water levels, Paradise Valley, Humboldt County, Nevada, spring 1968.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY FIT

and the adjacent part of Humboldt River Valley 

(Flynn, 1981; Schaefer and others, 1986; Schaefer, 

1988). The thickness of basin fill in the study area 

was determined from the Bouguer anomalies. 

Briefly, a regional surface was determined for all 

anomalies corresponding to outcrops of consolidated rocks, using a computer program that compares the observed surface with surfaces generated 

from mathematical formulas (Davis, 1973). The observed regional surface was reasonably approximated by a first-order (linear) trend surface. The 

computed regional surface was subtracted from the 

Bouguer anomalies, producing residual values that 

represent the gravity field of the lower-density basin fill.

Thickness of the basin fill was estimated from 

these residual values, using a three-dimensional 

gravity inversion model (Cordell, 1970), by specifying a density contrast between basin fill and consolidated rocks. A density contrast of 31.2 lb/ft3 

(0.5 g/cm3) was used in estimating the thickness of 

basin fill; this value was based on an average density for saturated basin fill of 135.4 lb/ft3 (2.17 g/ 

cm3 ) and an average density for consolidated rocks 

of 166.7 lb/ft3 (2.67 g/cm3 ). The density used for basin fill is within the range of densities determined 

from borehole gravity data for two wells in Paradise Valley (Robbins and others, 1985, p. 14-16).

The estimated thickness of basin fill is shown in 

figure 10. The valley is divided into at least four 

structural depressions, which suggest that complex 

structures are present beneath the valley. Maximum thickness of basin fill exceeds 8,000 ft in the 

center of the valley. On the basis of topography 

and geology in the mountains surrounding Paradise Valley, Sales (1966, pi. 11) drew northwesttrending shears that he interpreted as being 

caused by strike-slip faulting. These features generally coincide with the areas between structural 

depressions (fig. 10). On the basis of the basin-fill 

thickness, additional shears (not mapped by Sales) 

may trend in the same direction. Thus, in addition 

to the predominant northeast-trending normal 

faults that bound the valley on the eastern and 

western sides, several faults, which have both vertical and horizontal displacement, may structurally 

divide the valley into several smaller basins. Thermal springs in the area are located near the intersection of the northeast-trending normal faults and 

the northwest-trending shears (Flynn, 1981, p. 

100), which suggests that small quantities of water 

might be moving along these features.

Reversed seismic-refraction profiles were taken 

at five locations in the valley to estimate the thickness of basin fill for comparison with estimates 

from gravity measurements (Donald H. Schaefer, 

U.S. Geological Survey, written commun., 1992). 

Locations of the seismic profiles are shown in figure 10. Measurements were taken using 12- and 

24-channel seismographs. Explosives were used as 

the energy source for generating sound waves and 

were placed at progressively greater distances at 

the end of either side of the geophones along each 

profile. The geophones were spaced at intervals of 

100 ft.

Thickness of the basin fill was estimated along 

each profile by determining a change in velocity on 

time-distance plots of the data, as explained by 

Haeni (1988, p. 3). Velocity of the basin fill is generally about 6,000 ft/s, whereas the velocity of the 

consolidated rocks is generally 10,000 ft/s or 

greater. Thickness of the basin fill was determined 

from the seismic profiles by Donald H. Schaefer 

(U.S. Geological Survey, written commun., 1992) 

and is summarized in table 3. Thicknesses estimated from gravity measurements also are listed 

for comparison. For the three profiles where the 

basin fill exceeds 2,000 ft (SI, S3, and S5), estimated thicknesses from seismic-refraction profiles 

are less than or equal to those from gravity data. 

For the other two profiles (S2 and S4), estimated 

thicknesses from the seismic-refraction profiles exceed those estimated from gravity data. The latter 

two profiles are along the southwestern side of the 

valley where the depth to ground water exceeds 

100 ft (fig. 8).

Thickness of basin fill calculated from gravity 

measurements is underestimated near the margins 

of the valley. A large part of the basin fill is unsaturated near the valley margins, where depth to 

ground water can exceed 100 ft. Unsaturated basin 

fill has a lower density than saturated basin fill 

(Robbins and others, 1985). The computer program 

used to calculate thickness from gravity is based on 

one density contrast. The value chosen for this 

study is the density difference between saturated 

basin fill and consolidated rocks. The use of a density contrast greater than the one chosen, to account 

for the unsaturated sediments, is not warranted 

because unsaturated sediments are a fraction of 

the total basin-fill thickness except along the margins.

HYDRAULIC PROPERTIES

The water-transmitting properties of the basin 

fill are determined by estimating the aggregate
F18

41°30'

41°00'

REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH 

117°45' 117°30'

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

EXPLANATION

Basin fill 

Consolidated rocks

 500 Line of equal thickness 

of basin fillDashed where approximately 

located. Interval 1,000 feet, 

with 500-foot line near the 

margins of basin

Northwest-trending

shears-Modified from Sales, 

(1966). Dashed where 

projected across basin fill

 - - Boundary of study area

 Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River 

Valley-l > >nr.a where 

approximately located

S2 Seismic refraction profile

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

FIGURE 10. Thickness of basin fill in Paradise Valley, Humboldt County, Nevada. Thickness estimated from gravity 

measurements by Schaefer and others (1986) and Flynn (1981).
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F19

Table 3. Comparison of basin-fill thickness at five 

sites in Paradise Valley, Humboldt County, Nevada, 

estimated using seismic-refraction and gravity 

methods

refraction profile

(fig. 10)

SI

S2

S3

S4

S5

Thickness of basin

Gravity

3,000-3,500

<500

2,000-4,000

<500

5,000-6,000

fill (feet)

Seismic

refraction

2,000

700

3,000

1,300

5,700

Beneath seismic-refraction profiles, thicknesses 

determined by Donald H. Schaefer (U.S. Geological Survey). 

Thicknesses calculated from gravity measurements differ from 

place to place, as shown in figure 10.

hydraulic conductivity of the many discontinuous 

lenses of gravel, sand, silt, and clay, whereas the 

quantity of water that the deposits can store is determined by estimating the aggregate storage coefficient of the deposits. Both of these properties 

depend on the environment of deposition as well as 

the types of earth materials that compose the basin 

fill. Deposits derived from the Hot Springs Range, 

which consists mostly of older sedimentary rocks, 

are potentially more productive than deposits from 

the Santa Rosa Range, where the rocks are mostly 

granitic and fine-grained metamorphic rocks that 

tend to decompose more readily to clay (Harrill and 

Moore, 1970, p. 21). Clean sand and gravel deposits 

in the basin fill usually produce the greatest quantities of water; thus, identifying areas of sand and 

gravel deposits usually results in locating the most 

productive areas for development. The percent of 

gravel in the upper 100 ft of basin fill in Paradise 

Valley was mapped by Bredehoeft (1963, p. 32) using data from drillers' logs. The greatest accumulations of gravel are just below points where Martin 

Creek and the Little Humboldt River enter Paradise Valley. Additional information from drillers' 

logs of deeper wells supports this observation and 

indicates that the gravel deposits continue to 

depths of at least 400 ft.

HYDRAULIC CONDUCTIVITY

Estimates of hydraulic conductivity of the basin 

fill were obtained from specific-capacity data reported on drillers' logs, from values of transmissivity derived by Harrill and Moore (1970), and from

aquifer tests of several wells drilled on the southwestern side of the valley. Theis (1963) presented an 

equation for estimating transmissivity (hydraulic 

conductivity multiplied by thickness of the aquifer) 

from specific-capacity data assuming no difference 

in water level between the well and aquifer material a short distance from the well. The equation 

can be written as:

T = 0.000177(Q/s) -0.577 - In (1)

where Q/s = specific capacity, in gallons per 

minute per foot of drawdown; 

Q = pumping rate, in gallons per minute; 

s = drawdown of the well, in feet; 

T = transmissivity, in feet squared per

second;

t = pumping period, in seconds; 

r = effective well radius, in feet; and 

S = storage coefficient (dimensionless).

Specific capacity of a well usually is less than an 

ideal well because well entrance losses produce 

lower water levels in the well than in the aquifer 

immediately adjacent to the well (Meyer, 1963, 

p. 339). Specific capacity of a well also is affected 

by pumping period and effective well radius (Walton, 1962, p. 12-13; Meyer, 1963, p. 339). However, 

specific capacity values do not change greatly for 

tests exceeding 8 hours (28,800 seconds), nor do 

the values change greatly for wells with a radius 

from 0.67 to 1.08 ft (Bredehoeft, 1963, p. 35), the 

normal radius of irrigation wells drilled in Paradise Valley.

Estimates of hydraulic conductivity were determined for 90 wells in Paradise Valley by dividing 

the estimated transmissivity determined from 

specific-capacity data by the length of the screened 

interval of the well. The average hydraulic conductivity of the upper 600 ft of basin fill (approximate 

interval of the wells), assuming a storage coefficient equal to a specific yield of 0.3, was 3.7xlO~4 

ft/s (32 ft/d) with a standard deviation of SxlO"4 ft/ 

s (69 ft/d). The average hydraulic conductivity assuming a specific yield of 0.1 was 4.1xlO~4 ft/s (35 

ft/d) with a standard deviation of 9X1Q-4 ft/s (78 ft/ 

d). The minimum estimate of hydraulic conductivity was 6xlO~6 ft/s (0.5 ft/d), whereas the maximum 

was 2xlO~3 ft/s (173 ft/d).

Distribution of hydraulic conductivity in the upper 600 ft of basin fill as determined from specificcapacity tests is shown in figure 11. In general, the
F20 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45' 117°30'

41°30'

41°00'

R. 37 E. R. 38 E. R. 39 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

EXPLANATION

Consolidated rocks

Estimated hydraulic conductivity 

of basin fill-in feet per second

Not estimated

Greater than or equal to 

0.0001

Less than 0.0001 

Boundary of study area

Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

Well with specific-capacity data

FIGURE 11. Distribution of hydraulic conductivity in upper 600 feet of basin fill as determined from specific-capacity data,

Paradise Valley, Humboldt County, Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F21

higher values of hydraulic conductivity are in the 

center of the valley, with the area of higher values 

increasing in width from north to south. The approximate contact between basin fill with hydraulic 

conductivities less than IxlO"4 ft/s (9 ft/d) and 

basin fill with hydraulic conductivities greater than 

IxlO"4 ft/s is similar to the contact between older 

and younger alluvium (compare figs. 4 and 11). 

Although values of hydraulic conductivity as determined from specific-capacity data are only approximate, the values indicate that permeability of the 

basin fill, at least in the upper 600 ft, is less on the 

valley margins than in the center of the valley. The 

hydraulic conductivity of the basin fill below the 

deepest water wells is unknown, but for purposes of 

this study, it is assumed to be similar in distribution to the values determined for the upper 600 ft. 

The errors involved in calculating transmissivity, 

and therefore hydraulic conductivity, from specificcapacity data result in values that are probably 

low. Specific-capacity values of a well are generally 

lower than specific-capacity values of the aquifer 

because of well losses, which in turn lower the estimates of transmissivity and, therefore, hydraulic 

conductivity. The low values may be in part offset 

by having underestimated the effective well radius, 

which is probably greater than the radius of the 

well casing or the gravel pack (if any) used in the 

calculations. Well development most likely causes 

the effective well radius to extend beyond the casing or gravel pack (Bredehoeft, 1963, p. 36). Uncertainties in the actual storage coefficients also 

result in an uncertainty in the estimate of transmissivity, but large changes in storage coefficient 

only result in small changes in transmissivity.

The estimates of horizontal hydraulic conductivity from specific-capacity data from wells may be 

high when comparing the values with an average 

value that includes the finer grained deposits because most wells are screened only next to the 

more permeable (coarser) deposits.

STORAGE COEFFICIENT

The term storage coefficient is used to describe 

water released from or taken into storage in an 

aquifer. Water from storage is derived from (1) expansion of water, (2) compression of the aquifer, (3) 

compression of clay beds or lenses within the basin-fill aquifer, and (4) gravity drainage of the pore 

spaces in the unconfined zone. The volume of water 

released by gravity drainage of the pore spaces is 

referred to as specific yield and is expressed as a

percentage of the volume of drained aquifer. The 

volume of water released per unit change in head 

is usually much greater than the volume released 

by the other three processes. Therefore, the storage 

coefficient in the unconfined part of the basin-fill 

aquifer is assumed equal to the specific yield.

Estimates of average specific yield in the upper 

200 ft of saturated basin fill were made from lithologic descriptions from drillers' logs, laboratory 

analyses of samples collected along the Humboldt 

River and reported by Cohen (1963a), and results of 

borehole-gravity surveys of two wells in the valley.

The lithologic descriptions from drillers' logs 

were divided into six categories and were assigned 

specific-yield values (table 4) that were based on 

results by Cohen (1961, 1963a), Morris and Johnson 

(1966), and Harrill and Moore (1970). Silts normally have a specific yield of less than 10 percent; 

Cohen (1961, p. 44), however, reported an average 

specific yield for silts of 19 percent for samples 

along the Humboldt River near Winnemucca. This 

was the specific-yield value assigned to silts in 

Paradise Valley. Cohen (1963a, p. 23) noted that 

the higher-than-normal specific yield of the silts 

might be caused by their relatively high porosity, 

the compaction of the material during the laboratory tests, and the centrifuge-moisture equivalent 

tests used to compute specific yield. Because the 

centrifuge tends to expel more water than would 

otherwise drain by gravity, the specific yield reported by Cohen from the centrifuge test could be 

too high, particularly for fine-grained material 

(Smith, 1961, p. 11).

Distribution of the estimated specific yield for 

Paradise Valley is shown in figure 12, which is 

similar to the distribution estimated by Harrill and 

Moore (1970, p. 28). In general, the highest specific 

yields are in areas of major streams. The high specific yields at the southern end of the valley are 

the result of buried channel deposits from the 

Humboldt River, from the Little Humboldt River, 

or from both (Harrill and Moore, 1970, p. 26). Low 

specific-yield values generally are associated with 

fan deposits, particularly along the western side of 

the valley.

Specific yield was estimated at two wells in 

Paradise Valley from borehole gravity surveys (location of wells shown in fig. 12). Bulk densities of 

the deposits were determined from repeated gravity measurements at selected depth intervals in 

each well as described by Robbins and others 

(1985). The difference in bulk densities above and 

below the water table was assumed to be caused 

only by the difference in the quantity of water
F22 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

Table 4. Estimated specific yield of lithologies described in drillers' logs, Paradise Valley, Humboldt County, Nevada

Terms used by well drillers

Assigned 

specific 

yield1

(percent)

Sand ............................ 30

Sand and gravel; sand and cobbles; sand and

boulders; cobbles; gravel ............. 25

Silt .............................. 19

Boulders, silt, and clay; cobbles, silt, and clay;

gravel and clay; cemented gravel; gravel, sand,

silt, and clay; sand and silt; sand, gravel, and

clay ............................ 15

Clay and sand; sand and clay; sand, some clay;

silt and clay ...................... 10

Clay ............................... 6

Based on information from Cohen (1961, p. 44; 

1963a, p. M19), Morris and Johnson (1966, p. 36), and 

Harrill and Moore (1970, p. 27)

within the pores; that is, grain density and porosity were assumed constant. The average bulk density for 20 ft above the water table in the northern 

well (well 02AA1 in fig. 12) was 119.2 lb/ft3 (1.91 g/ 

cm3), whereas the average bulk density for 55 ft 

below the water table was 131.7 lb/ft3 (2.11 g/cm3 ), 

or a difference of 12.5 lb/ft3 (0.2 g/cm3 ). Assuming 

1 Ib of water is equal to 0.016 ft3 of water, the volume of water drained per total volume was 0.2 ft3/ 

ft3 , resulting in an estimated specific yield of 20 

percent. This compares to a specific-yield estimate 

of 14 percent from the lithologic description of materials found in the well. The difference in bulk 

density above and below the water table in the well 

at the southern end of the valley (well 23BDA1 in 

fig. 12) was 18.7 lb/ft3 (0.3 g/cm3 ), which results in 

a specific-yield estimate of 30 percent. The estimate of specific yield from the lithologic description 

was 20 percent. On the basis of results from these 

two wells, specific yield estimated from the borehole gravity data was higher than that estimated 

from lithologic logs.

The estimated specific yields from the borehole 

gravity data may be in error because both the 

grain density and the porosity can vary depending 

on the types of deposits found with depth in the 

wells. However, estimates of specific yield from 

lithologic descriptions also may be in error owing 

to inaccuracies in the description of the type of deposits reported in drillers' logs and to the actual 

specific yield of a particular type of deposit being 

different than the assigned value. Although the

borehole gravity surveys give better estimates of 

specific yield, lithologic descriptions from drillers' 

logs are used to estimate specific yield throughout 

the valley because only two estimates of specific 

yield are available from borehole gravity data.

GROUND WATER IN STORAGE

A large quantity of ground water is in storage in 

the basin-fill aquifer. Approximately 1.8 million 

acre-ft of water is estimated to be stored in the upper 50 ft of saturated basin fill in the entire study 

area, on the basis of the product of the area, thickness, and distribution of specific yield shown in figure 12. About 1.6 million acre-ft of water is stored 

in the upper 50 ft of saturated basin fill in Paradise Valley slightly less than the estimate of 1.8 

million acre-ft reported by Harrill and Moore 

(1970, p. 72). The lower estimate for this study is 

the result of slightly lower estimated specific yields 

along the northern and western sides of the valley. 

The quantity of water stored in the upper 200 ft of 

saturated basin fill is approximately 7 million acreft for the entire study area (includes Humboldt 

River Valley) and about 6.2 million acre-ft for 

Paradise Valley.

GROUND-WATER RECHARGE

Almost all the water that recharges the basin-fill 

aquifer in Paradise Valley is from precipitation in 

the drainage basin. Recharge to the basin-fill aquifer is from (1) infiltration of precipitation on the 

valley floor, (2) subsurface inflow from adjacent 

mountains, (3) infiltration of water from streams 

that cross the basin fill, and (4) infiltration of applied irrigation water. Infiltration of applied irrigation water is discussed in later sections titled 

"Infiltration of Water from Streams" and "GroundWater Pumpage." A summary of recharge estimates 

prior to large quantities of pumpage is presented in 

table 5.

PRECIPITATION ON VALLEY FLOOR

An average of about 250,000 acre-ft/yr of precipitation falls on the drainage basin of Paradise Valley (Harrill and Moore, 1970, p. 39). Most of this 

precipitation is directly evaporated, but some of it 

runs off as surface flow, some replenishes soil
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F23

117°45' 117°30'

41°30' -

41°00' -

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

EXPLANATION

Consolidated rocks

Estimated specific yieldIn percent, for upper 200 feet of 

saturated basin fill; queried 

where uncertain

Less than 10 

10 to 14 

15 to 19 

More than 20

 Boundary of study area

 Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

02AA1 , Well where specific yield 

was estimated from 

borehole qravitv dataAbbreviated site designation 

is indicated

FIGURE 12. Distribution of specific yield in upper 200 feet of saturated basin fill as determined from drillers' logs, Paradise

Valley, Humboldt County, Nevada.
F24 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

TABLE 5. Estimates of annual ground-water recharge and discharge for basin-fill aquifer in Paradise Valley, Humboldt County, Nevada, and adjacent segment of Humboldt River Valley prior to large quantities of pumpage^

[Values in acre-feet per year and reported to two significant figures]

Water-budget component Estimated quantity

RECHARGE

Paradise Valley

Precipitation on valley floor

Leakage from streams

Recharge near contact between basin fill and consolidated rocks

Total

Humboldt River Valley

Precipitation on valley floor 

Underflow upstream from study area 

Recharge from Osgood Mountains 

Recharge from Sonoma Range 

Leakage from Humboldt River 

Underflow from Paradise Valley

Combined total recharge

Total

Paradise and Humboldt River Valleys

minor

40,000

1,000

41,000

minor

350-700

1,000

3,000-4,000

11,000-18,000

3,000-3,500

18,000-27,000

59,000-68,000

DISCHARGE

Evapotranspiration

Underflow to Humboldt River Valley

Evapotranspiration

Underflow downstream from study area

Combined total discharge

Paradise Valley

Total

Humboldt River Valley

Total

Paradise and Humboldt River Valleys

40,000 

3,000-3,500

43,000-44,000

13,000-25,000 

2,000

15,000-27,000

58,000-71,000

Values are based on estimates of Harrill and Moore (1970, table 14) for Paradise Valley and Cohen and others (1965, p. 47, 78, 

and 91) for Humboldt River Valley. See text for discussion of estimates.

Harrill and Moore (1970, p. 65) estimate that, for average conditions, about half of streamflow entering Paradise Valley is lost to 

evapotranspiration prior to reaching aquifer. Much of this loss, however, is in area of evapotranspiration from ground water. Because 

amount of streamflow evapotraaspiration was unknown for different penods of varying streamflow, results of model simulations assume that 

stream leakage into aquifer system was equal to inflow less outflow. Thus, estimates of evapotranspiration in model simulations include 

direct evapotranspiration of surface water.

moisture that is later transpired by plants, and 

some eventually infiltrates to the water table. 

However, precipitation on the valley floor averages 

about 9 in/yr, and most of this precipitation is 

evaporated directly or used to support plant

growth. Loeltz and others (1949) estimated that, on 

average, 9 in/yr of precipitation is evapotranspired 

in the Martin Creek drainage above the stream 

gage. At least that much is probably lost in Paradise Valley.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F25

About half of the precipitation in the study area 

falls during December through March, when potential evapotranspiration is small. The winter precipitation is usually as snow. A small part of this 

precipitation probably recharges the basin-fill aquifer, particularly in the valley lowlands where depth 

to water is less than 10 ft during the winter 

months. What does recharge the aquifer in the valley lowlands during the winter months is probably 

used by plants during the following summer. Thus, 

average annual recharge to the basin-fill aquifer 

from valley-floor precipitation is probably a small 

component of the total recharge to the basin, except perhaps during years of exceptionally high 

precipitation, such as 1983.

SUBSURFACE INFLOW FROM ADJACENT MOUNTAINS

The subsurface inflow from the adjacent mountains to the basin-fill aquifer is considered small 

because permeability of the consolidated rocks is 

generally low. Harrill and Moore (1970, p. 62) estimated subsurface inflow to be about 1,000 acre-ft/ 

yr. Loeltz and others (1949, p. 33) reported that 

some water from consolidated rocks probably recharges the basin-fill aquifer because several thermal springs and one thermal well (well 03DC1 in 

fig. 2) are in or near Paradise Valley, but the quantity of inflow is probably small because the temperature of water in all other wells pumped in the 

valley was cool, below 70°F. Water in most wells 

drilled since 1950 also has a temperature below 

70°F.

INFILTRATION OF WATER FROM STREAMS

Recharge to the basin-fill aquifer is primarily 

from infiltration of water through stream channels 

of intermittent and perennial streams that flow 

across the basin fill. Additional recharge occurs 

from the infiltration of surface water that has been 

diverted for irrigation.

Average annual runoff into Paradise Valley was 

estimated by Harrill and Moore (1970, p. 51-53) to 

be about 70,000 acre-ft/yr. The value was revised 

during this study to 72,000 acre-ft/yr on the basis 

of a greater average flow in Martin Creek for the 

period 1923-82. About 41,000 acre-ft/yr of this total runoff (57 percent) is from the combined annual 

flow of Martin Creek and Little Humboldt River. 

Of the remaining 31,000 acre-ft/yr, about 27,000 

acre-ft/yr is runoff from the Santa Rosa Range and

volcanic rocks that border the northwestern side 

and northern end of Paradise Valley (Harrill and 

Moore, 1970, p. 53).

Runoff into Paradise Valley is largely lost within 

the valley by infiltration to ground water, by 

evaporation and transpiration along the stream 

and irrigation channels, and by consumption from 

irrigated crops. Only a small percentage of the runoff reaches the Humboldt River and then only 

when the sand dunes that block the channel of the 

Little Humboldt River are breached or excavated to 

drain Gumboot Lake. The annual surface outflow 

to Humboldt River was estimated by Harrill 

and Moore (1970, p. 69) to be about 2,000 acre-ft. 

However, the estimated annual outflow for 1948 

through 1982 (table 2) was about 3,700 acre-ft.

Only about one-third to one-half of the runoff 

into the valley recharged the basin-fill aquifer, according to Loeltz and others (1949, p. 39). The average annual recharge to the basin-fill aquifer in 

Paradise Valley was estimated by Harrill and 

Moore (1970, p. 65) at about 40,000 acre-ft; this included small quantities of water that entered the 

aquifer from consolidated rocks and as underflow 

beneath the channels of Martin Creek and Little 

Humboldt River.

Each time Gumboot Lake forms, some water recharges the ground water at the southern end of 

Paradise Valley, even though the surficial sediments in the area are generally fine grained. Because a lake of appropriate size forms, on average, 

only about once in 5 years, with large accumulations even less frequent, the annual recharge is estimated to be only 1,000 acre-ft (Harrill and Moore, 

1970, p. 81). However, significant recharge does periodically occur from Gumboot Lake. For example, 

in 1952 and 1953, a large lake covered an area of 

about 10,000 acres and may have averaged 4 to 5 ft 

deep prior to it being drained. Water levels rose 

more than 10 ft in one nearby well. Recharge from 

the lake was estimated at 6,000 acre-ft during 

1952-53 (Harrill and Moore, 1970, p. 81). In this 

report, recharge from Gumboot Lake is, for modeling purposes, included in the estimate of recharge 

from stream leakage.

Areas that are irrigated from diversions of 

streamflow account for most of the streamflow loss 

by evapotranspiration and are usually found where 

the water table is within a few feet of land surface; 

much of the water applied during the spring may 

actually reach the water table, from which it is 

consumed by the crops in the summer when 

streamflows are low. Although about half of the average annual streamflow entering Paradise Valley
F26 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

is lost to evapotranspiration prior to recharging the 

aquifer (Harrill and Moore, 1970, p. 65), estimates 

of direct evapotranspiration of surface water for selected time intervals with varying quantities of 

runoff are unknown. To simplify the model simulations in this report, none of the streamflow was 

lost directly to evapotranspiration in the model 

simulations prior to recharging the basin-fill aquifer, but rather surface water was allowed to recharge the aquifer where it was then discharged 

nearby as evapotranspiration. The final result is 

the same in that most of the water (precipitation, 

streamflow, and ground water) in Paradise Valley 

is discharged by evapotranspiration.

INFILTRATION OF WATER FROM HUMBOLDT RIVER

The deposits along the Humboldt River are generally in hydraulic continuity with the river. Seepage losses from the river to the basin-fill aquifer in 

Humboldt River Valley occur at a few localities 

throughout the year, but most of the infiltration of 

river water to the basin-fill aquifer occurs between 

April and July when the river's stage and flow are 

normally at their peaks (Cohen and others, 1965, 

p. 80). The average annual loss in streamflow measured between the Comus gage (about 21 mi east of 

Winnemucca, fig. 2) and the Rose Creek gage 

(about 15 mi southwest of Winnemucca, fig. 2) for 

the 14-year period 1949-62 is 17,000 acre-ft (Cohen, 

1964, p. 41). The average loss between the months 

of February through June of each year from 1949 

to 1962 is 28,000 acre-ft, whereas for the months of 

July through January of each year the river gains 

11,000 acre-ft. This increase is due to ground water 

discharging into the river, mostly from bank storage of river water that had infiltrated into the 

flood-plain deposits during the previous spring 

when runoff was high (Cohen, 1964, p. 42).

Most of the measured loss in streamflow in the 

Humboldt River from February through June was 

along the reach between Comus and Winnemucca 

and is based on several measurements between the 

Comus and Rose Creek gaging stations taken during the months of April and June of years 1960-62 

(Cohen and others, 1965, p. 49-56). Between 80 

and 95 percent of the measured total loss in 

streamflow was between Comus and Winnemucca, 

and between 50 to 75 percent of the total loss was 

between Golconda and Winnemucca (fig. 2), the 

reach of the river that lies within the study area. 

Assuming that the measured losses along the Humboldt River on specific dates are typical of losses 

from February through June, between 14,000 and 

21,000 acre-ft is lost along the reach between 

Golconda and Winnemucca during this 5-month period. In addition, about 30 percent of the total increase in streamflow was measured between 

Golconda and Winnemucca on the basis of several 

measurements of streamflow between the Comus 

and Rose Creek gages between August and December of years 1959-63. Assuming these measured 

gains are representative for the 7-month period 

from July through January, the increased flow for 

the period is about 3,300 acre-ft. Combining the 

two estimates results in an annual loss along the 

Humboldt River from Golconda to Winnemucca of 

11,000 to 18,000 acre-ft.

Much of the streamflow lost between Golconda 

and Winnemucca temporarily recharges the basinfill aquifer near the river, where it is later evapotranspired by both native vegetation and cropland. 

Some streamflow is trapped in shallow depressions 

and oxbow lakes in the flood plain, where it is 

evaporated, but the water table near the standing 

bodies of water is usually close to the water level 

in the lakes and ponds; thus, the standing bodies 

of water can be considered part of the basin-fill 

aquifer.

SUBSURFACE INFLOW ALONG HUMBOLDT RIVER

Some water flows beneath the Humboldt River 

where it enters the study area. Underflow near the 

Comus gage (see fig. 2 for location) is about 350 to 

700 acre-ft/yr (Cohen and others, 1965, p. 78). 

Underflow along the Humboldt River increases 

near Golconda because of leakage from the Humboldt River, inflow to the valley from the Sonoma 

Range, and inflow to the valley from the hot 

springs at Golconda. About 3,000 to 4,000 acre-ft/yr 

is estimated as underflow from tributary areas in 

the Sonoma Range. This underflow enters the 

Humboldt River Valley near Golconda and, to a 

lesser extent, to the west (Cohen and others, 1965, 

p. 77).

GROUND-WATER DISCHARGE

Ground-water discharge from the basin-fill aquifer in Paradise Valley is by evapotranspiration 

from irrigated crops, native vegetation, and bare 

soils where the water table is shallow; by subsurface outflow to the adjacent Humboldt River Val-
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F27

ley; and by pumping of ground water for irrigation, 

stock watering, and domestic use. A summary of 

discharge from the basin-fill aquifer is presented in 

table 5.

EVAPOTRANSPIRATION

Prior to the early 1970's, the principal form of 

ground-water discharge from the basin-fill aquifer 

was evapotranspiration from phreatophytes in areas where depth to ground water was generally 

less than 20 ft. Ground water also discharged directly from evaporation where the water table was 

close to land surface.

In Paradise Valley, about 100,000 acres of 

phreatophytes and crops annually consumed approximately 70,000 acre-ft through evapotranspiration from 1949 to 1968 (Harrill and Moore, 

1970, p. 67), about 40,000 acre-ft of which was estimated from ground water. Rates of evapotranspiration ranged from 2.5 ft/yr for crops (primarily 

alfalfa and pasture) to 0.1 ft/yr for low-density 

stands of greasewood and rabbitbrush near the 

southern end of Paradise Valley.

Evapotranspiration from phreatophytes and 

crops is also the principal form of ground-water 

discharge from the basin-fill aquifer in Humboldt 

River Valley. Although evapotranspiration of 

ground water along the reach of the Humboldt 

River in the study area has not been estimated, 

about 25,000 to 50,000 acre-ft/yr was estimated as 

the quantity of evapotranspiration along Humboldt 

River Valley between Comus and Rose Creek (fig. 

2) for water years 1949-62 (Cohen and others, 

1965, p. 91). The area of evapotranspiration used in 

this estimate is about twice the area included in 

the present study. Thus, annual evapotranspiration 

along the segment of Humboldt River included in 

this study is assumed to be between about 13,000 

and 25,000 acre-ft.

SUBSURFACE OUTFLOW TO HUMBOLDT RIVER VALLEY

Prior to the early 1970's, ground-water flow 

was generally southward in Paradise Valley to 

Humboldt River Valley, where the predominant 

flow direction was westward, parallel to the river 

(fig. 9). The quantity of ground-water flow leaving 

Paradise Valley was estimated by Loeltz and others (1949, p. 42) to be about 3,200 acre-ft/yr. Their 

estimate was based on a streamflow gain of 4.4

ft3/s between Golconda and Winnemucca on the 

Humboldt River (fig. 2) measured in September 

and October 1947. A range between 3,000 and 

3,500 acre-ft/yr was reported by Cohen (1963b, p. 

65). His estimate was based on a streamflow gain 

of 2.7 ft3/s measured in the falls of 1960 and 1961 

and included an estimate in the gain in underflow 

that was moving parallel to the river.

Some of the gains in flow of the Humboldt River 

measured by Loeltz and others (1949) and Cohen 

(1963b) may be water that seeped into the floodplain deposits during spring runoff of snowmelt 

only to discharge back to the river when the river 

stage declined (referred to as bank storage by 

Cohen and others, 1965, p. 83). Thus, the actual 

volume of ground water discharging from Paradise 

Valley into the Humboldt River Valley prior to 

large-scale pumping may be less than previously 

reported.

SUBSURFACE OUTFLOW ALONG HUMBOLDT RIVER

Some water leaves the study area as underflow 

beneath the channel of the Humboldt River Valley. 

The quantity of underflow is estimated to be about 

2,000 acre-ft/yr (2.8 ft3/s) near Winnemucca. This 

value is based on the reported extent of a gravel 

unit (Cohen and others, 1965, pi. 1), on a waterlevel gradient of 0.001 ft/ft (Cohen and others, 

1965, pi. 3), and on a representative hydraulic conductivity of about 8xlO~3 ft/s (650 ft/d; Cohen and 

others, 1965, p. 33).

GROUND-WATER PUMPAGE

Prior to 1948, water pumped from wells was 

used primarily for domestic purposes and for livestock. The total quantity of water pumped in 1947 

was about 200 acre-ft from 100 wells equipped 

mostly with pumps that had a capacity of about 5 

gal/min (Loeltz and others, 1949, p. 39). Estimates 

of water pumped from wells for domestic purposes 

and to supply water for the school and public buildings in the town of Paradise Valley increased from 

30 acre-ft/yr in 1948 (Harrill and Moore, 1970, 

p. 71) to about 120 acre-ft/yr in 1982. These estimates are based on the number of people who were 

living in the valley and the number of wells that 

were used for domestic purposes. The quantity of 

water pumped from wells for stock watering remained at about 100 acre-ft/yr from 1948 to 1966
F28 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

(Harrill and Moore, 1970, p. 71) and increased to 

about 120 acre-ft/yr between 1967 and 1982. These 

estimates are based on the number of wells used 

for stock watering and discussions with local 

ranchers.

Estimates of ground-water pumpage for irrigation from 1948 through 1968 were obtained from 

Harrill and Moore (1970, p. 71). Pumpage from 

1969 through 1982 was estimated from the number 

of irrigation wells drilled in the valley, the types 

of crops irrigated, and the methods used to irrigate 

the crops. Power consumption records were not 

available between 1969 and 1980 because the 

power companies routinely disposed of the records 

after a few years. In addition, the greatest pumpage in Paradise Valley is at the southwestern part 

of the valley, where an integrated irrigation system 

with several booster pumps and interconnected distribution lines make estimates using power consumption tenuous.

Estimates of ground-water use per crop type and 

irrigation system are listed in table 6. These estimates are based on information furnished by local 

residents. In general, more water is used to flood 

irrigate a field than is used by sprinklers. Estimates of water use per acre of crop at Winnemucca 

Farms are based on values supplied by farm manager A.J. Evans (Winnemucca, Nev., oral commun., 

1982) and are the lower value for sprinkler systems 

in table 6. Also, wells used for flood irrigation are 

generally used to supplement irrigation needs not 

met by streamflow and are normally used only during the late summer and early fall. During years of 

above-normal streamflows, such as 1980 and 1982, 

some irrigation wells were not used at all.

Only a small quantity of ground water was 

pumped for irrigation in 1947 (Loeltz and others, 

1949, p. 51). Ground-water pumpage in Paradise 

Valley began to increase in the mid-1950's, when 

11 wells were drilled to irrigate crops. Most of the 

wells were drilled along the flood plain of Little 

Humboldt River and were used primarily to supplement surface-water supplies during periods when 

streamflow was insufficient to irrigate crops. 

Pumpage increased slowly until 1966 (fig. ISA), 

when below-normal runoff in 1966 and 1968 (see 

fig. 7) resulted in a substantial increase. Pumpage 

decreased substantially in 1969 (fig. ISA) because 

runoff into Paradise Valley was 200 percent of normal and many supplemental wells were not used.

According to drillers' logs submitted to the Nevada State Engineer's office, only 36 irrigation 

wells were drilled in Paradise Valley prior to 1968. 

These wells and the distribution of irrigated lands

TABLE 6. Estimates of annual ground-water pumpage 

by crop type and irrigation system, Paradise Valley, 

Humboldt County, Nevada

[Values in acre-feet per acre. Symbol: "--," irrigation type is 

not used for irrigated crop type.]

Crop type

Alfalfa

Grain (wheat, barley)

Potatoes

Pasture and hay

Flood

irrigation

0-3

0-1

-

0-3

Sprinkler

irrigation

2.5-2.8

0.8-1.0

2.5-2.8

--

1 Range in values depends on whether well

supplements surface-water supplies and on the amount 

of runoff available during the year.

Lower values were used for Winnemucca 

Farms; slightly higher values were used for systems in 

remainder of study area. Lower use rate for grain is 

for special varieties of wheat; otherwise, 1.0 acre-foot 

per acre was used throughout the study area.

for 1968 are shown in figure 14. Water from only 

two wells was pumped into sprinkler systems in

1968 (Harrill and Moore, 1970, pi. 1); the other irrigation wells were used to supplement surface water.

An additional 91 wells were drilled in the valley 

between 1972 and 1982, of which 19 were drilled to 

replace older wells. Thirty-one irrigation wells 

were drilled in 1973 the most drilled during a 

single year in Paradise Valley. In addition to the 

wells drilled in Paradise Valley, eight irrigation 

wells were drilled in 1972-73 just east of Golconda 

Butte in Humboldt River Valley. Pumping from 

these wells affects ground-water flow between 

Paradise Valley and Humboldt River Valley. The 

quantity of pumpage from wells in the adjacent 

segment of Humboldt River Valley ranged from an 

estimated 1,900 acre-ft/yr in 1973 to 5,300 acre-ft/ 

yr in 1977 (fig. 13B).

Most of the new irrigation wells drilled between

1969 and 1982 are located in the southern part of 

Paradise Valley (fig. 15). This area uses ground 

water as the principal source for irrigation, and 

thus pumpage increased rapidly between 1969 and 

1981. Pumpage increased from about 6,800 acre-ft 

in 1970 to about 47,000 acre-ft in 1981 (fig. ISA). 

An additional 3,700 acre-ft was pumped in 1981 

from wells located in the adjacent segment of 

Humboldt River Valley (fig. 13B). Pumpage estimates in 1980 and 1982 were less than in 1981 because some wells that are used to supplement 

streamflows were not used owing to above-normal 

streamflows. Pumpage in Paradise Valley was esti-
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F29

mated at 43,000 acre-ft in 1980 and 44,000 acre-ft 

in 1982; an additional 2,600 and 3,800 acre-ft was 

pumped in 1980 and 1982, respectively, in the 

Humboldt River Valley. Although not estimated, 

pumpage for 1983 and 1984 most likely was less 

than 1981 because of continued above-average 

streamflows.

Not all the ground water pumped from wells is 

consumed; some water returns to the basin-fill 

aquifer, particularly along the flood plains of Martin Creek and Little Humboldt River, where depths 

to water are only a few feet below land surface. 

Net pumpage shown in figure 13 is an estimate of 

the quantity of pumpage consumed by the plants or 

evaporated from the soils. The quantity of irrigation pumpage that returns to the basin-fill aquifer 

is dependent on the method of irrigation, the character of the soil, the slope of the field, and other 

factors (Harrill and Moore, 1970, p. 70). This quantity probably ranges from 10 percent of the total in 

fields where ground water is pumped through pressured sprinklers, to about 60 percent in some fields 

near streams where ground water is pumped to 

supplement surface-water irrigation. Prior to the

1970's, most of the ground water was pumped into 

unlined ditches in the valley bottom and the quantity of recirculated pumpage averaged about 40 

percent (Harrill and Moore, 1970, p. 70). In the 

1970's, much of the ground water pumped was applied using pressurized sprinkling systems, which 

reduced the quantity of water that returned to the 

basin-fill aquifer. Because of the pressurized sprinkling systems, only about 20 percent of the total 

pumpage was estimated to return to the basin-fill 

aquifer between 1972 and 1982. For example, total 

pumpage for Paradise Valley of 47,000 acre-ft in 

1981 resulted in an estimated net pumpage of 

about 38,000 acre-ft.

SIMULATION OF GROUND-WATER FLOW

The principal technique used to analyze groundwater flow and yield of the basin-fill aquifer was 

with a digital computer model. The remainder of 

this report describes the type of model used, the 

general features of the model, and the model 

results. The model was first calibrated to a period

CC 

LLJ

CC 

LLJ 

D.

LLJ 

LLJ 

LL

LLJ 

OC 

O

U_ 

O

D

50

40

30

20

10

A. Paradise Valley

TOTAL PUMPAGE 

NET PUMPAGE

u

0

I i I I I I I

B. Adjacent segment of Humboldt River Valley

i

1945 1950

i

1955

I

1960

I

1965

YEARS

, .Mil

1970 1975

Mill

1980 19J

FIGURE 13. Annual ground-water pumpage, 1948-82, for (A) Paradise Valley and (B) adjacent segment of Humboldt 

River Valley, Humboldt County, Nevada. Net pumpage equals total pumpage minus amount estimated to return 

to basin-fill aquifer.
F30 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45' 117°30'

41°30'

41°00'

R. 37 E. R. 38 E. R. 39 E.

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

Universal Mercator projection 

Zone 11

R. 40 E. R. 41 E.

EXPLANATION

Basin fill 

Consolidated rocks

Irrigated field in which 

ground water is 

principal source of 

water

Irrigated field in which 

ground water supplements surface water

 - Boundary of study area

 . . . . Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

 Irrigation well

10 MILES

10 KILOMETERS

FIGURE 14. Distribution of irrigated lands and irrigation wells as of 1968, Paradise Valley, Humboldt County, Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F31

117°45' 117°30'

41°30'

41°15

41°00

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

EXPLANATION

Basin fill 

Consolidated rocks

Irrigated field in which 

ground water is 

principal source of 

water

Irrigated field in which 

ground water supplements surface water

 Boundary of study area

 - - - - Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted wnere 

approximately located

 Irrigation well

10 KILOMETERS

FIGURE 15. Distribution of irrigated lands and irrigation wells as of 1981, Paradise Valley, Humboldt County, Nevada.
F32 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

of average conditions with little ground-water 

pumpage (1948-68) and then recalibrated to selected periods of varying climatic conditions and 

changes in ground-water pumpage (1948-82). The 

calibrated model was used to simulate long-term 

trends that describe probable future response to selected ground-water development in the valley.

DIGITAL COMPUTER MODEL

A computer program written by McDonald and 

Harbaugh (1988) was used to simulate ground-water flow in Paradise Valley. The program solves the 

three-dimensional equation of ground-water flow 

using finite-difference approximations. The equation solved by the program can be written as follows:

(2)

"s

h = 

t =

Kxx> Kyy

W =

where S0 = specific storage, in per foot; 

hydraulic head, in feet; 

time, in seconds;

hydraulic conductivity in the principal horizontal directions, in feet per 

second;

hydraulic conductivity in the vertical 

direction, in feet per second; 

volumetric flux of recharge or discharge per unit volume, in per foot; 

and

x, y, z = Cartesian coordinates, in feet, aligned 

along the major axes of hydraulic 

conductivity.

The continuous derivatives in equation 2 are replaced with finite-difference approximations at a 

point or node. Surrounding each node is a model 

block with dimensions x, y, and z, in which the hydraulic properties are assumed to be uniform. 

Thus, to simulate the field conditions using the 

computer program, the aquifer was divided into 

blocks, and values of aquifer properties were estimated for each block.

The strongly implicit procedure was used in the 

computer program to solve the unknown head for 

each time step in the model simulations (McDonald 

and Harbaugh, 1988, p. 12-1 through 12-65). The 

unknown head was solved by iterating through the 

finite-difference equations for each node until the 

head change between iterations was less than a

specified value. The value specified for the model 

simulations of Paradise Valley was 0.1 ft. Once 

this criterion was met, the model advanced to a 

new time interval and the process of computing 

head values at each node was repeated. The numerical technique used to solve the ground-water 

flow equation is discussed in detail by McDonald 

and Harbaugh (1988).

GENERAL FEATURES OF MODEL

A simplified diagram (fig. 16A) shows the general pattern of recharge, discharge, and ground-water flow in Paradise Valley. The computer model 

can simulate many elements of the basin-fill aquifer (fig. 16B), including recharge from precipitation, stream leakage, and irrigated crops, and 

discharge by evapotranspiration, pumping, and 

stream leakage.

To simulate ground-water flow with the computer program, the basin-fill aquifer was divided 

into model blocks with horizontal dimensions of 

2,500 ft on a side. A finite-difference grid of 33 columns and 89 rows was superimposed over a map of 

the study area and oriented so that a minimum 

number of blocks were outside the study area (fig. 

17). At most, three layers of model blocks were 

used to represent the basin-fill aquifer vertically. 

The thickness of model blocks differed among layers and varied within a single layer. The uppermost layer (layer one in fig. 16B) corresponds to 

the interval incorporating at least parts of screened 

intervals for all wells. Layer one is present wherever the thickness of basin fill exceeds 250 ft, and 

it has a maximum thickness of 600 ft. Layer two is 

present wherever basin fill exceeds 600 ft, and it 

has a maximum thickness of 600 ft and, thus, a 

maximum depth of 1,200 ft. Layer two corresponds 

to an interval that is penetrated by only a few 

wells. Layer three, the bottom layer, represents basin fill below a depth of 1,200 ft. The thickness of 

model blocks in this layer may exceed 6,000 ft locally. Layer three corresponds to an interval in the 

basin fill for which no wells nor information on hydraulic properties exist. Layers two and three are 

included primarily to account for water stored in 

these intervals and for the small quantities of water that flow through them. Layer one is assumed 

to be unconfined, whereas layers two and three are 

considered to be confined. Numbers in the grid 

shown in figure 17 correspond to the number of 

layers used to simulate flow in the basin fill.

The thickness of layer one is dependent on the 

depth of wells that have been drilled in the central
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F33

EXPLANATION

Basin-fill aquifer 

Consolidated rocks

Direction of groundwater movement

Fault Arrows indicate 

direction of movement

Abbreviations:

R Recharge from stream leakage 

and as flow from bedrock

ET Discharge from evapotranspiration 

W Discharge of pumped ground water

FIGURE 16. Schematic three-dimensional diagram of basin-fill aquifer (A), and 

same diagram with basin fill represented by blocks for computer simulation 

(B), Paradise Valley, Humboldt County, Nevada.
F34 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45' 117°30'

41°30'

41°00'

Winnemucca

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

EXPLANATION

Basin fill 

Consolidated rocks

Finite-difference model 

blocks

Layer one only 

Layers one and two 

Layers one, two, and three

 Boundary of active model 

blocks

 - Boundary of study area

 - Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-boned where 

approximately located

FIGURE 17. Finite-difference grid used to simulate ground-water flow in the basin-fill aquifer, Paradise Valley, Humboldt

County, Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F35

and southern parts of Paradise Valley and water 

levels in wells. The response to pumping in this 

part of the valley suggests that the upper 600 ft of 

basin fill is essentially unconfined. Water levels 

vary little between wells of different depths (deepest wells are less than 800 ft below land surface) in 

most of the valley, and except for a flowing hot 

well (see fig. 2 for location) in the south-central 

part of Paradise Valley, water levels in wells are at 

or below land surface. The flowing hot well has a 

measured depth of 60 ft and is at a site of an old 

hot springs (Loeltz and others, 1949, p. 34). Wells 

drilled to depths of 500 ft within a few miles of the 

flowing well are neither hot nor flowing.

Downward hydraulic gradients, however, exist 

near the northwestern edge of the basin-fill aquifer 

and are caused by both lower permeabilities of the 

deposits and greater quantities of recharge than at 

other locations along the margins of the valley. The 

thickness of layer one was not decreased to simulate observed vertical gradients in this area because a greater thickness for layer one was needed 

to simulate large water-level declines for the hypothetical pumping patterns.

Model blocks in the finite-difference grid were 

designated either active or inactive. Model blocks 

corresponding to basin fill were generally designated as active except along the margins of the valley where the thickness of basin fill was less than 

250 ft. Consolidated rocks were considered to have 

a much lower permeability than the basin fill, and 

for the purposes of the model, model blocks corresponding to consolidated rocks were designated inactive. Although Golconda Butte near the southeast 

corner of the study area (see fig. 17) also was assumed to be impermeable, the younger basalt flows 

near the southwest corner of the study area were 

assumed capable of storing and transmitting water, 

and the model blocks corresponding to these basalt 

flows were designated as active.

Model blocks south of the Humboldt River also 

were designated inactive because the Humboldt 

River was used to simulate the southern boundary 

of flow in Paradise Valley. Although some ground 

water enters Humboldt River Valley from the 

Sonoma Range to the south, much of this flow enters near Golconda. The general ground-water flow 

direction south of the river is parallel to the river 

with a small component to the river (Cohen, 1963b, 

p. 60). The small quantity of ground-water flow entering Humboldt River Valley from the south was 

incorporated into the estimated seepage from the 

Humboldt River. In addition, some ground water 

flows through alluvium where the Humboldt River

exits the model area near Winnemucca; in the 

model, this flow was simulated as leakage to the 

Humboldt River.

STREAM LEAKAGE

Most of the recharge to the basin-fill aquifer is 

by seepage loss (leakage) from streams that cross 

the basin fill (Harrill and Moore, 1970, p. 62). 

Streamflows vary from year to year; consequently, 

recharge to the basin-fill aquifer is variable. To account for the variable recharge from streamflows, 

stream leakage was simulated in the model of 

Paradise Valley using a streamflow-routing program (Prudic, 1989) written specifically for the 

computer program of McDonald and Harbaugh 

(1988). In this program, the quantity of leakage to 

the aquifer is limited to the quantity of streamflow 

that enters the modeled area. To account for 

streamflows, streams are divided into two categories: reaches and segments. Each reach corresponds 

to individual model blocks in the finite-difference 

grid. Segments are groups of reaches connected in 

downstream order. Streamflows are specified for 

the first reach in each segment that enters the 

modeled area. The program then computes streamflow into adjacent downstream reaches in each 

stream segment as equal to streamflow in the upstream reach plus or minus leakage from or to the 

aquifer in the upstream reach. When streamflows 

of one or more segments are combined into one 

downstream segment, the inflow to the downstream 

segment is the sum of outflow from each tributary 

segment.

Leakage between a stream reach and model 

block is controlled by the head difference between 

the reach and model block and by a conductance 

term for the streambed (Prudic, 1989, p. 7). Leakage between a stream reach and model block is 

limited to the quantity of streamflow that enters 

the reach. If inflow to a reach is zero, then leakage 

from a reach to a corresponding model block is not 

allowed. However, if the head in a model block is 

greater than the altitude of the streambed in a corresponding stream reach, then leakage from the 

model block to the reach is simulated.

Actual altitudes of stream stage and channel are 

not known for every model block representing a 

stream reach. The average channel altitude for 

each reach was estimated from topographic maps. 

The error in these estimates is ±10 ft on the valley 

floor and ±20 ft on the adjacent alluvial fans. 

Stream stage typically is only 1 to 2 ft above the
F36 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

stream channel. Consequently, average streamstage altitude for each reach was simply assigned 

the estimated channel altitude. The value of streambed conductance varied for each reach and was estimated from the length of the stream in a model 

block, the average stream width, the estimated hydraulic conductivity of the streambed that was the 

same as those estimated for the basin-fill aquifer 

(lxlO~5 ft/s along the alluvial fans to IxlO"4 ft/s in 

the valley bottoms), and a streambed thickness of 

3ft.

A total of 274 stream reaches and 27 segments 

was used to simulate stream leakage, including the 

section of the Humboldt River used as the southern 

boundary of the modeled area. The distribution of 

reaches used in the simulations are shown in figure 18. Average streamflow for each stream was 

specified where streams entered the modeled area. 

Streamflow entering the modeled area was averaged for each simulation period on the basis of 

streamflow gaging records for Martin Creek, Little 

Humboldt River, and the Humboldt River. For 

ungaged streams, streamflow was related to flow in 

Martin Creek on the basis of drainage area and altitude in a manner described by Moore (1968).

Constant recharge rates were assigned to model 

blocks along the margins of the valley to account 

for underflow from the adjacent mountains. In addition, streams for which average annual discharge 

did not exceed 1,200 acre-ft/yr (1.7 ft3/s) are included in the constant recharge rates. The constant 

recharge rates are distributed over model blocks 

corresponding to areas of underflow and to the 

smaller streams. Values of recharge range from 

0.001 to 0.8 ft3/s. The distribution of blocks assigned a constant recharge rate is shown in figure 

18. Several blocks, particularly along the east flank 

of the Santa Rosa Mountains (northwestern side of 

model grid), are assigned both a stream reach and 

a constant recharge rate.

The streamflow-routing program is a simplified 

technique that allows recharge to be simulated in 

the center of Paradise Valley from cyclic or periodic 

pulses of runoff. Assumptions used in the simulation of stream leakage that may affect results include the following: (1) streamflow entering the 

modeled area is instantaneously available to all 

downstream reaches; (2) leakage between streams 

and aquifer is instantaneous even if the stream 

and aquifer are separated by an unsaturated zone; 

and (3) none of the streamflow is lost directly to 

evapotranspiration prior to seeping into the ground. 

The first assumption probably does not affect the 

simulation results because streamflow entering the

valley passes through it in a few days, whereas the 

changes in ground-water flow in the simulations 

were averaged over months and years. The second 

assumption may not be valid in areas where the 

unsaturated zone is many tens to hundreds of feet. 

Such conditions exist only near the margins of the 

valley where leakage from streamflow is generally 

constant with time. The third assumption was 

made to simplify transient simulations where rates 

of direct evapotranspiration of streamflow are unknown. Generally, however, direct evapotranspiration from streamflow is concentrated in the valley 

lowlands, where depth to ground water is only a 

few feet and where evapotranspiration from ground 

water is also concentrated. Thus, model results of 

evapotranspiration presented in this report include 

both evapotranspiration of ground water and surface water.

The version of the package used in this study 

does not include stream dynamics, in part because 

of the lack of information regarding the relations of 

stream width and stream stage to the discharge of 

the streams for each model reach. The package 

used to analyze ground-water flow and yield in 

Paradise Valley did, however, adequately simulate 

the effect of cyclic and periodic pulses of runoff in 

the valley.

EVAPOTRANSPIRATION

Most of the ground-water discharge in Paradise 

Valley prior to development was by evapotranspiration. Only a small part of the ground-water flow 

may have actually discharged to the Humboldt 

River. Discharge by evapotranspiration from the 

model was simulated with a head-dependent function that decreased linearly with depth (McDonald 

and Harbaugh, 1988, p. 316-320). A maximum 

evapotranspiration rate was simulated when the 

water table in layer one was at land surface. The 

maximum rate was assumed to be 3 ft/yr: this 

equals the rate of evaporation from open bodies of 

water (lakes and ponds) near Winnemucca, which 

is about 3.7 ft during the growing season (Robinson, 

1965, p. 90), minus the average precipitation, 

which is about 0.7 ft/yr. The rate was decreased 

linearly to zero at a specified depth of 20 ft below 

land surface. To simulate discharge by evapotranspiration, values of land-surface altitude, of depth 

where evapotranspiration becomes zero, and of a 

maximum rate of evapotranspiration were specified 

for each active block in layer one.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F37

117°45' 117°30'

41°30'

41°00'

R. 37 E. R. 38 E. R. 39 E.

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

Universal Mercator projection 

Zone 11

R. 40 E. R. 41 E.

10 MILES

10 KILOMETERS

D

EXPLANATION

Basin fill 

Consolidated rocks

Finite-difference model 

blocks

Stream blocks

Recharge-In cubic feet per 

second

No recharge assigned 

0.001 to 0.01 

0.01 to 0.1 

0.1 to 0.8

 Boundary of active model 

blocks

 Boundary of study area

 Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

FIGURE 18. Distribution of model blocks used to simulate recharge from or discharge to streams, and blocks assigned a

constant recharge rate, Paradise Valley, Humboldt County, Nevada.
F38 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

INITIAL CONDITIONS AND HYDRAULIC PROPERTIES

The initial water-level distribution for model 

layer one is based on spring 1968 water-level measurements (fig. 9). These water levels are assumed 

to represent equilibrium conditions that existed 

prior to the withdrawal of large quantities of 

ground water from the basin-fill aquifer beginning 

in the early 1970's. The same water levels were initially used for model layers two and three because 

no water-level data were available for these layers.

Transmissivities were assigned to the model 

blocks using two approaches. For model layer one, 

the transmissivity was calculated by the computer 

program. The saturated thickness was calculated 

during each model iteration by subtracting the bottom altitude of each block in layer one from the 

computed water level from the previous model 

iteration. This value was then multiplied by the assigned hydraulic conductivity to obtain the transmissivity. The value of hydraulic conductivity 

assigned to each model block is based on the distribution shown in figure 11. Transmissivities were 

assigned directly to model layers two and three 

and remained constant during a simulation. Transmissivities were initially determined as the product 

of the layer thickness and an assigned hydraulic 

conductivity. Hydraulic conductivity of the basin 

fill for model layers two and three are unknown, 

but initial estimates were determined assuming 

that hydraulic conductivity decreased with depth 

due to overburden pressures. Hydraulic conductivity used in model layer one was decreased 50 percent for every 1,200 ft of depth below layer one and 

is based on a relation reported by Durbin and others (1978, p. 76). Estimates of hydraulic conductivity were adjusted during model calibration, but the 

relation of decreased hydraulic conductivity with 

depth did not change. Thus, if values of hydraulic 

conductivity were decreased in model layer one, so 

were the values in model layers two and three.

Flow between model layers was simulated using 

a leakance term, which is expressed as the ratio of 

vertical hydraulic conductivity to the thickness of a 

confining unit (Lohman, 1979, p. 30). For purposes 

of the model simulations, the thickness used to determine leakance values was represented as the 

distance between the midpoints of two model 

blocks in adjacent layers. Because the basin fill is 

composed of numerous discontinuous lenses of 

coarse- and fine-grained deposits, an equivalent 

leakance value between model layers was used in 

the simulation. Initial estimates of vertical hydraulic conductivity were determined for the upper 600

ft of basin fill using the thicknesses of coarse- and 

fine-grained deposits reported in drillers' logs and 

the following equation:

K=- (3)

K.

where Kv = equivalent vertical hydraulic conductivity, in feet per second; 

b = total thickness, in feet; 

bc , bf = sum of the thicknesses of coarseand fine-grained deposits, respectively, in feet; and

Kvc , Kvf = vertical hydraulic conductivities of 

coarse- and fine-grained deposits, 

respectively, in feet per second.

Vertical hydraulic conductivity of the finegrained deposits was assumed to be lxlO~7 ft/s 

(0.003 ft/d) and is based on analyses of more than 

200 core samples from fine-grained deposits in 

California (Johnson and others, 1968, table 5). Vertical hydraulic conductivity of the coarse-grained 

deposits was assumed equal to the hydraulic conductivity determined from specific-capacity data. 

The vertical hydraulic conductivity also was assumed to decrease with increasing depth in the 

same manner as the horizontal hydraulic conductivity. Vertical hydraulic-conductivity values were 

adjusted also during calibration of the model.

Specific-yield values were used as the storage coefficient in model layer one (an unconfined aquifer) 

for the transient simulations. The distribution of 

specific yield is shown in figure 12. The storage coefficients in model layers two and three varied according to the thickness assigned to each model 

block and were estimated by multiplying the thickness with a specific storage of 2xlO~6 per ft. This 

value was used to represent the specific storage of 

basin fill that consists of a mixture of coarse- and 

fine-grained deposits. The value was obtained from 

studies in similar types of sediments (Nelson, 1982; 

Williamson and others, 1989).

RESULTS OF SIMULATION

PREDEVELOPMENT CONDITIONS

Prior to the withdrawal of water from wells, 

ground-water levels fluctuated only in response to 

variations in streamflow and to seasonal changes
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F39

in the quantity of evapotranspiration. Water levels 

were generally highest in the spring and early 

summer, owing to infiltration of runoff from the 

surrounding mountains, and lowest in the fall and 

early winter, owing to discharge by evapotranspiration in the valley bottom during the previous summer. Yearly variations in ground-water levels were 

primarily caused by the abundance or lack of runoff. The first valley-wide measurement of water 

levels in wells was made in September 1947 (Loeltz 

and others, 1949), the next was in February 1968, 

and a third occurred in November 1968 (Harrill 

and Moore, 1970, p. 75). The difference in water 

levels in wells between the fall of 1947 and fall of 

1968 was less than 5 ft. This difference is less than 

the seasonal fluctuations reported by Loeltz and 

others (1949, p. 75) from measurements in 10 wells 

during 1946 and 1947, and it is also less than fluctuations reported by Harrill and Moore (1970, 

p. 75) from measurements in many wells during 

1968. Thus, the basin-fill aquifer in Paradise Valley was in a general state of equilibrium (referred 

to as steady state) between September 1947 and 

November 1968, as there was no long-term increase 

nor decrease in ground-water levels and, therefore, 

no net change in ground-water storage.

Water levels measured in the valley in September 1947 and November 1968 may not be the same 

as those when the valley was first settled in the 

1800's. The practice of diverting streams for irrigation of crops in the late 1800's and early 1900's increased the quantity of recharge to the basin-fill 

aquifer (Loeltz and others, 1949, p. 33), particularly in that part of the valley north of T. 39 N. 

This increased recharge probably raised water levels over much of the valley. Thus, the steady-state 

simulations described in the following paragraphs 

are representative of water levels after the diversion of streams began in the late 1800's and early 

1900's, and before the withdrawal of large quantities of water began in the early 1970's.

CALIBRATION OF STEADY-STATE SIMULATIONS

Calibration of a ground-water flow model is usually achieved by changing the values of aquifer 

properties or the quantity and distribution of recharge and discharge, or both, until the model-calculated water levels match the measured water 

levels in the aquifer. The sequence of calibration 

used in the steady-state simulation was to adjust 

only the values of vertical and horizontal hydraulic 

conductivity and streambed conductance. The

thickness of basin fill, streamflow entering the 

modeled area, recharge along the edges of the modeled area, maximum evapotranspiration rate, and 

depth where evapotranspiration ceases were assumed correct and not adjusted.

The model was considered calibrated on the basis of the following: (1) The mean departure of 

model-calculated water levels from measured water 

levels was near zero for the 169 model blocks corresponding to wells in layer one; (2) more than 95 

percent of the model-calculated water levels were 

within 20 ft of measured water levels; (3) the simulated distribution of evapotranspiration approximated the estimated distribution; and (4) leakage 

from streams approximated streamflow losses.

Horizontal hydraulic conductivities were adjusted by uniformly changing the hydraulic conductivity throughout the modeled area, keeping the 

general pattern of hydraulic conductivity estimated 

from specific-capacity data. Next, model blocks associated with the major streams entering Paradise 

Valley and associated with the Humboldt River 

were adjusted to reflect suspected areas of higher 

conductivities. Vertical hydraulic conductivities 

were uniformly adjusted throughout the modeled 

area but were not adjusted between individual 

model blocks because no evidence existed to support such changes. Finally, streambed-conductance 

values were adjusted for model blocks that contained stream reaches until leakage per mile of 

stream channel approximated streamflow losses reported by Loeltz and others (1949) and all the average streamflow in Paradise Valley was simulated 

as leaking into the basin-fill aquifer. Even though 

some of the streamflow has discharged to the Humboldt River since 1953, most of this flow was the 

result of a channel being dredged through the sand 

dunes. The steady-state simulation presented in 

this report represents a time period when Gumboot 

Lake was not drained by dredging. The discharge 

of streamflow from Paradise Valley was simulated 

in the transient simulations presented in the section titled "Effects of Development, 1948 through 

1982." Streambed-conductance values for model 

blocks that contain reaches of the Humboldt River 

were adjusted until leakage from the Humboldt 

River approximately equaled the estimated annual 

loss in streamflow between Golconda and Winnemucca of 11,000 to 18,000 acre-ft.

Usually, only one well corresponded to a model 

block (surface area of about 0.25 mi2 ); in the few 

blocks having more than one well, the measured 

water levels from all wells within the model block 

were averaged. For the best-fit simulation, about
F40 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

96 percent of the simulated water levels in layer 

one were within 20 ft of the measured water levels 

(fig. 19). In calibrating the model, differences of 

less than 20 ft were considered tolerable because 

altitudes of many wells in the valley were estimated from topographic maps that had a contour 

interval of 20 ft in the valley and 40 ft along the 

margins. Thus, errors in estimating the water-level 

altitudes measured from wells along the margins of 

the valley could be as much as half the contour interval or 20 ft. In addition, differences of more 

than 20 ft between the simulated and measured 

water levels in the northwestern part of the study 

area may be the result of downward gradients in 

the area. Simulated water levels are a composite 

over the thickness of the model block, whereas 

measured water levels either represent the measurement from one well or the average of a few 

wells.

The mean difference between simulated and 

measured water levels for the 169 model blocks 

was -0.77 ft with a standard deviation of 9.6 ft. On

100 iABSOLUTE DIFFERENCES BETWEEN SIMULATED

AND MEASURED WATER LEVELS,

IN FEET

FIGURE 19. Cumulative percentage of absolute differences 

between simulated and measured water levels for best-fit 

steady-state simulation, Paradise Valley, Humboldt 

County, Nevada.

the average, the simulated water levels were 

slightly lower than the measured water levels. 

Overall, however, the simulated water levels 

matched measured water levels as shown by contours of both simulated and measured water levels 

(fig. 20). The contours of measured water levels are 

from figure 9.

The distribution of horizontal hydraulic conductivity from the best-fit steady-state simulation for 

model layer one is shown in figure 21. Where layers two and three are present, distribution of hydraulic conductivities were the same but the values 

of vertical and horizontal hydraulic conductivities 

were decreased to account for compaction by overburden, as discussed in the section "Initial Conditions and Hydraulic Properties." The average 

horizontal hydraulic conductivity for layer one was 

2xlO~4 fl/s (17 ft/d) and is about two times less 

than the average estimated from specific-capacity 

data. Most of the wells used to estimate hydraulic 

conductivity are perforated next to the coarser 

grained deposits. If only the thickness of the 

coarser grained deposits had been used in the 

model computations instead of the total thickness, 

the average model calibrated hydraulic conductivity 

would be about the same as the average estimated 

from specific-capacity and pumping-test data.

The general distribution of hydraulic conductivities for layer one is similar to that estimated from 

specific-capacity data (compare figs. 11 and 21). 

The highest computed hydraulic conductivities are 

along the Humboldt River and in the central part 

of Paradise Valley. These values are associated 

with well-sorted stream deposits. The lowest computed hydraulic conductivities are along the northern and western sides of Paradise Valley. The 

lower hydraulic conductivities along the western 

side of the valley are attributed to the weathering 

of granitic and metamorphic rocks eroded from the 

mountains to the west into silts and clays (Harrill 

and Moore, 1970, p. 24). Saturated thickness of 

layer one also is shown in figure 21; it is based on 

the difference between the simulated water level 

and the bottom altitude of layer one. The saturated 

thickness is greater than 500 ft throughout much 

of the valley. Only along the margins adjacent to 

the mountain ranges is the saturated thickness 

less than 250 ft.

Transmissivities in layer two, shown in figure 

22A, generally reflect the distribution of hydraulic 

conductivity in layer one. Transmissivities in layer 

two range from 6xlO~5 to 8.6xlQ-2 ft2/s (5 to 7,500 

ft2/d). The lowest values are along the margins of
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F41

117°45' 117°30'

41°30' -

41°00' 

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

EXPLANATION

Basin fill 

Consolidated rocks

Simulated and measured 

water-level contoursShows altitude of groundwater level. Contour interval, 

in feet, is variable. Datum is 

sea level

 4310 Simulated water levels in 

model layer one for 

period 1948-68

 4310 - Measured water levels. 

1948-68. Contours 

at north end of valley 

are based on data for 

wells deeper than 

100 feet. Dashed 

where approximately 

located

 Boundary of study area

 .... Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

 ^^^m General direction of

simulated ground-water 

flow in model layer one

FIGURE 20. Simulated and measured ground-water levels in upper 600 feet of basin fill for period 1948-68, Paradise

Valley, Humboldt County, Nevada.
F42 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH 

117°45' 117°30'

41°30'

41°00'

Winnemucca

R. 37 E. R. 38 E. R. 39 E.

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

Universal Mercator projection 

Zone 11

R. 40 E. R. 41 E.

10 MILES

10 KILOMETERS

-250

EXPLANATION

Basin fill 

Consolidated rocks

Hydraulic conductivity of 

model blocks in layer oneIn feet per second

l.OxlO-5 

2.2xlO-5 

3.6xlO-5 

l.SxlO4 

3.6xlO-4

Line of equal saturated 

thickness of layer

one-Interval 250 feet

 Boundary of active model 

blocks, layer one

 ^~ Boundary of study area

Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

FIGURE 21. Distribution of layer-one hydraulic conductivity and saturated thickness used in best-fit model simulations,

Paradise Valley, Humboldt County, Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F43

the valley and correspond to areas of lower hydraulic conductivity and areas where the thickness of 

layer two is less than 600 ft. Transmissivities in 

layer three, shown in figure 225, are similar to 

those in layer two except in the center of the valley, where values range from IxlO"1 to GxlO"1 ft2/s 

(8,640 to 50,000 ft2/d). These high transmissivities 

are the result of including the entire thickness of 

basin fill below a depth of 1,200 ft in layer three 

and do not necessarily indicate a highly permeable 

zone.

The average vertical hydraulic conductivity is 

3xlO~6 ft/s (0.3 ft/d) between layers one and two 

and is 5xlO~7 ft/s (0.04 ft/d) between layers two 

and three. Vertical hydraulic conductivity is incorporated in the model as a leakance term. Leakance 

is defined for the model of Paradise Valley as the 

vertical hydraulic conductivity divided by the distance between midpoints of blocks in adjacent layers. The distribution of leakance between layers 

one and two is shown in figure 23A. Values range 

from 9xlO~10 to 3xlO~8 per second. Highest 

leakances are simulated in the north-central part 

of Paradise Valley, along the southeastern margin 

of the valley (adjacent to the southwestern flank of 

the Hot Springs Range), and along the Humboldt 

River. The distribution of leakance between layers 

two and three is shown in figure 235. Values range 

from lxlO~10 to 2xlO~8 per second. Generally, 

leakance values are less between layers two and 

three than between layers one and two, for two 

reasons: a slightly lower vertical hydraulic conductivity, and a greater distance between the midpoints of blocks.

In the model simulations, the areal distribution 

of evapotranspiration was not specified as a boundary, except that discharge was simulated in areas 

where the calculated water level in layer one was 

less than 20 ft below land surface. The distribution 

of evapotranspiration from the best-fit steady-state 

simulation is shown in figure 24. The distribution 

approximates zones of phreatophytes mapped by 

Harrill and Moore (1970, pi. 1) in Paradise Valley 

and by Cohen (1964, fig. 6) in Humboldt River Valley. The distribution also corresponds to the more 

densely vegetated areas as determined from Landsat imagery in the early 1980's (J. LaRue Smith, 

U.S. Geological Survey, written commun., 1984).

SIMULATED GROUND-WATER FLOW

Results of the best-fit simulation show that water-level altitudes in model layers two and three

are generally lower than water levels in layer one 

in the northern end of Paradise Valley (fig. 25), 

where layer one receives much of its recharge. This 

trend indicates downward flow from layer one to 

layers two and three in an area where water-level 

differences between shallow and deeper wells also 

suggest downward flow. Water-level altitudes in 

layers two and three are generally higher than 

those in layer one near the southern end of the valley and along the western half of the Humboldt 

River, where any remaining flow in the model 

simulations must discharge. Water levels in layer 

two are lower than layer one where the Humboldt 

River enters the study area near Golconda, indicating downward leakage in this area.

Most of the ground-water flow in the best-fit 

steady-state simulation was in model layer one, 

which corresponds to the upper 600 ft of basin-fill 

deposits. Generally, recharge to this layer was from 

stream leakage in the valley lowlands, and discharge was by evapotranspiration near the streams. 

Only about 700 acre-ft/yr, or about 1 percent of the 

quantity recharged to the basin-fill aquifer, was 

simulated as flow in model layers two and three, 

which represents flow in deposits deeper than 600 

ft.

A total of about 74,000 acre-ft/yr was simulated 

as recharge into the basin-fill aquifer in Paradise 

Valley, and another 20,000 acre-ft/yr was simulated in Humboldt River Valley north of the river 

(table 7). Of the recharge in Paradise Valley, about 

72,000 acre-ft/yr was simulated as either streamflow entering the model area or as constant recharge along the edge of the model and is based on 

the long-term (1923-82) estimate of streamflows 

into the valley. About 800 acre-ft/yr of ground water was simulated as discharging into streams in 

the upper part of the valley, which was recharged 

back into the basin-fill aquifer farther down valley. 

In the steady-state simulations, all streamflow in 

Paradise Valley was assumed to recharge the basin-fill aquifer, even though some surface water 

has discharged to Humboldt River since 1953. Most 

of this flow was the result of a channel being 

dredged through the sand dunes to drain Gumboot 

Lake. Prior to 1953, the sand dunes were not 

dredged and rarely was streamflow from Paradise 

Valley discharged to Humboldt River. Thus, the 

steady-state simulation represents a time period 

when Gumboot Lake was not drained by dredging a 

channel. However, discharge of streamflows from 

Paradise Valley was simulated in the transient 

simulations, as discussed in the following section.
F44 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45' 117°30'

41°30'

41°00'

Winnemucca,

R. 37 E. R. 38 E. R. 39 E. R. 40 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

EXPLANATION

Basin fill 

Consolidated rocks

Transmissivity of model 

blocks in layer twoIn feet squared per 

second

Less than l.OxlO-3 

l.OxlO-3 to l.OxlO-2 

l.OxlO-2 to 1.0x10!

 Boundary of active model 

blocks, layer two

 . . _ Boundary of study area

 - - Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

FIGURE 22. Distribution of (A) layer two and (B) layer three transmissivities used in best-fit model simulations of Paradise Valley, Humboldt County, Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F45

117°45' 117°30'

41°30'

41°00'

B.

Winnemucca

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

EXPLANATION

J Basin fill 

I Consolidated rocks

Transmissivity of model blocks 

in layer three-In feet 

squared per second

Less than LOxlO'3 

l.OxlO-3 to l.OxlO-2 

l.OxlO-2 to 1.0x10! 

l.OxlO-1 to 6.0x10-*

 Boundary of active model 

blocks, layer three

 - - Boundary of study area

 Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

FIGURE 22. Continued.
F46 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45' 117°30'

41°30'

41°00'

A.

")

Winnemucca

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

EXPLANATION

Basin fill 

Consolidated rocks

Leakance between model 

layers one and two-In

per second

l.OxlO-10 to l.OxlO-9 

l.OxlO-9 to l.OxlO'8 

l.OxlO-8 to S.OxlO-8

 Boundary of active model 

blocks, layer two

 - - Boundary of study area

 _ . . . . Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

FIGURE 23. Distribution of leakance between (A) layers one and two and OB) layers two and three used in best-fit model

simulations, Paradise Valley, Humboldt County, Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F47

117°45' 117°30'

41°30'

41°00'

a.

Winnemucca

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

EXPLANATION

Basin fill 

Consolidated rocks

Leakance between model layers

two and three-In per second

EB l.OxlO-10 to l.OxlO 9 

191 l.OxlO-9 to l.OxlO 8

I l.OxlO-8 toS.OxlO 8

 Boundary of active model 

blocks, layer three

 - - - Boundary of study area

 - Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

FIGURE 23. Continued.
F48 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45' 117°30'

41°30'

41°00'

Winnemucca.,

R. 37 E. R. 38 E. R. 39 E.

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

Universal Mercator projection 

Zone 11

0

R. 40 E. R. 41 E.

10 MILES

EXPLANATION

Consolidated rocks

Phreatophyte areas on basin fillModified from Harrill and Moore 

(1970, pi. 1) and Cohen (1964, 

fig- 6)

Primarily rabbitbrush and 

greasewood, with some areas 

that contain saltgrass and 

native hay

Primarily native hay and pasture, 

but can contain some alfalfa. 

Also includes some willow and 

silver buffaloberry

Primarily xerophytic plants

Line of equal simulated 

evapotranspirationInterval 1 foot per year

 Boundary of active model 

blocks

 Boundary of study area

Boundary between 

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

0510 KILOMETERS

FIGURE 24. Simulated evapotranspiration rates and mapped phreatophyte areas, Paradise Valley, Humboldt County, Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F49

117°45' 117°30'

41°30'

41°00'

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

EXPLANATION

Basin fill 

Consolidated rocks

Simulated water-level contoursShows altitude of groundwater level. Contour interval, 

in feet, is variable. Datum is sea 

level

 4310 Model layer one

 4310 Model layer two

 4310 Model layer three

 Boundary of study area

Boundary between 

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

FIGURE 25. Water levels in model layers one, two, and three for best-fit steady-state simulation, Paradise Valley,

Humboldt County, Nevada.
F50 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

TABLE 7. Average annual ground-water recharge and discharge for basin-fill aquifer in Paradise Valley, Humboldt 

County, Nevada, and adjacent segment of Humboldt River Valley prior to large quantities of pumpage for best-fit 

steady-state simulation 1

[Acre-feet per year reported to two significant figures]

Water-budget component Estimated quantity

RECHARGE

Paradise Valley

Recharge near contact between basin fill and consolidated rocks 

Leakage from streams in Paradise Valley 

Underflow from Humboldt River Valley

Humboldt River Valley

f\

Recharge from Osgood Mountains near contact between basin fill and consolidated rocks 

Leakage from Humboldt River 

Underflow from Paradise Valley

Total

Total

Paradise and Humboldt River Valleys

Combined total recharge

7,200

65,000

1,300

74,000

1,000

17,000

1,800

20,000

94,000

DISCHARGE

Evapotranspiration 

Leakage to streams 

Underflow to Humboldt River Valley

Evapotranspiration 

Underflow to Paradise Valley

Combined total discharge

Paradise Valley

Total

Humboldt River Valley

Total

Paradise and Humboldt River Valleys

71,000

800

1,800

74,000

18,000

1,300

19,000

93,000

1 Model-computed differences between combined total recharge and discharge was 600 acre-feet per year, or less than 1 percent. 

Includes leakage from streams where estimated annual flow is less than 1,200 acre-feet per year.

Harrill and Moore (1970, p. 65) estimate that, for average conditions, about half of streamflow entering Paradise Valley is lost to 

evapotranspiration prior to reaching aquifer. Much of this loss, however, is in an area of evapotranspiration of ground water. Because 

amount of streamflow evapotranspiration was unknown for different periods of varying streamflows (but streamflows into and out of valley 

were known), stream leakage into basin-fill aquifer was assumed equal to inflow less outflow. Thus, evapotranspiration calculated in all 

model simulations includes evapotranspiration of both ground water and surface water.

Includes evapotranspiration of streamflow, as explained in footnote 3.

The steady-state simulation also assumes that 

none of the streamflow entering the study area is 

lost directly to evapotranspiration. A previous 

study estimated that about half of the average annual streamflow entering Paradise Valley was lost

to evapotranspiration prior to actually recharging 

the basin-fill aquifer (Harrill and Moore, 1970, 

p. 65), but that much of this evapotranspiration 

was in the same area as evapotranspiration of 

ground water. Because the quantity of evapotrans-
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F51

piration directly from streams is in the same general area as evapotranspiration from ground water 

and because the quantity of evapotranspiration directly from streams is unknown for different periods of time, stream leakage into the basin-fill 

aquifer included direct evapotranspiration of 

streamflow. Similarly, recharge from stream leakage along the Humboldt River in the steady-state 

simulation was calibrated to approximate the average river loss between Golconda and Winnemucca, 

Nev. (fig. 2), and includes direct evapotranspiration 

of streamflow.

Ground-water flow from Paradise Valley into 

Humboldt River Valley was simulated at 1,800 

acre-ft/yr (table 7). This underflow was near the 

southwestern corner of the study area near where 

Little Humboldt River enters Humboldt River Valley (fig. 25). In addition, about 1,300 acre-ft/yr was 

simulated as underflow from Humboldt River Valley into Paradise Valley in the vicinity of Golconda 

Butte (fig. 25). This underflow continued in a 

northwesterly direction in the model simulations 

until reaching the center of Paradise Valley, where 

the predominant direction changed to the southwest. Thus, much of the water that was simulated 

as underflow from Paradise Valley into Humboldt 

River Valley may be ground water entering Paradise 

Valley as underflow from Humboldt River Valley.

Underflow from Paradise Valley to Humboldt 

River Valley computed in the steady-state simulation is about half that estimated by Loeltz and others (1949, p. 42) and Cohen and others (1965, p. 

77). Their estimates are based on measured inflow 

along the Humboldt River between Golconda and 

Winnemucca during low-flow periods and might include ground-water flow moving parallel with the 

river or water from bank storage that entered the 

flood-plain deposits next to the river during periods 

of high streamflows.

EFFECTS OF DEVELOPMENT, 1948 THROUGH 1982

Flow in the basin-fill aquifer was simulated for 

the period 1948-82 to determine the effects of increased ground-water withdrawals and natural 

variations in streamflow; this period was simulated 

because pumpage increased from about 200 acre-ft/ 

yr in 1948 to about 47,000 acre-ft/yr in 1981. (An 

additional 3,700 acre-ft was pumped in the adjacent segment of Humboldt River Valley during 

1981.)

Since the early 1970's, the direction of groundwater flow has been altered because of increased

pumpage in the southern end of Paradise Valley 

and the eastern part of Humboldt River Valley. As 

of 1982, this increased pumpage produced waterlevel declines of more than 80 ft (fig. 26), causing 

ground water to move toward the areas of greatest 

decline. The measured response to increased pumpage in the study area provided the basis for evaluation of yield in the basin-fill aquifer between 1948 

and 1982 and for evaluation of results from the 

simulation of selected development scenarios. The 

interval 1948-82 was divided into three separate 

periods: 1948-68, 1969-78, and 1979-82.

SELECTION OF STRESS PERIODS FOR SIMULATION

Although changes in ground-water levels in 

Paradise Valley between 1948 and 1968 were less 

than 5 ft and the period was assumed steady state 

during the initial model simulations, transient 

simulations were made also for the period because 

pumpage increased from only 200 acre-ft/yr in 1948 

to about 13,000 acre-ft/yr in 1968 (fig. 13). In addition, some years between 1948 and 1968 had distinctly more runoff and others considerably less 

(see fig. 7). Therefore, the purpose of the transient 

simulation from 1948 to 1968 was to determine if 

the basin-fill aquifer was in equilibrium (no net 

change in ground-water storage) and how the increased pumpage affected flow into and out of the 

basin-fill aquifer.

The 21-year period 1948-68 was divided into 

four stress periods, 1948-53, 1954-58, 1959-65, 

and 1966-68, to approximate variations in pumpage and streamflows (table 8). Each stress period 

was divided into equal time steps of 1-year duration. Thus, the first stress period (1948-53) has six 

time steps; the second (1954-58) has five; the third 

(1959-65) has seven; and the last (1966-68) has 

three. In another simulation, the number of time 

steps was increased to 10 for each of the first three 

stress periods and to 6 for the fourth period. Model 

results were the same for both simulations, indicating that the simulation with fewer time steps was 

adequate. Estimates of pumpage and streamflows 

were averaged over each stress period, as was recharge near the contact between basin fill and consolidated rocks. Streamflows from ungaged streams 

and recharge near the contact between basin fill 

and consolidated rocks were estimated by multiplying the values used in the steady-state simulations 

with the ratio of average streamflow of Martin 

Creek for the stress period to the average streamflow for the period 1923-82.
F52 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45' 117°30'

41°30'

41°00'

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

EXPLANATION

Consolidated rocks

Water-level change in basin fill 

from 1968 to fall 1982

No definable trend; natural 

fluctuations are as great as 

20 feet in northern part of 

valley

Declines from 1 to 10 feet 

Declines from 11 to 20 feet 

Declines from 21 to 40 feet 

Declines from 41 to 60 feet 

Declines from 61 to 80 feet 

Declines of 81 feet or more

 Boundary of study area

 - - - - Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

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

Universal Mercator projection 

Zone 11

10 MILES

0510 KILOMETERS

FIGURE 26. Ground-water level declines between 1968 and fall 1982, Paradise Valley, Humboldt County, Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F53

TABLE 8. Estimates of net ground-water pumpage in both Paradise Valley and adjacent segment of 

Humboldt River Valley, Humboldt County, Nevada, streamflow of gaged streams, and percentage 

of long-term mean flow at Martin Creek for selected model-stress periods, 1948-78

[Abbreviation: ft3/s, cubic feet per second]

Average streamflow of gaged streams

Martin Creek

Stress period 

(calendar year)

1948-53

1954-58

1959-65

1966-68

1969

1970

1971

1972

1973

1974

1975

1976

1977

1978

Net ground-water 

pumpage (ft /s)

0.7

3.1

5.6

8.5

3.7

5.9

7.5

16.0

21.9

34.3

37.0

41.6

45.6

52.6

Humboldt River 

(ft3/s)

307

208

229

159

549

336

701

314

440

275

737

189

73

261

Little Humboldt 

River (ft3/s)

30.9

25.5

18.3

12.9

71.3

28.6

37.8

35.7

27.2

25.8

24.3

18.0

8.8

30.7

Cubic feet 

per second

39.2

34.1

27.2

23.5

65.6

42.1

48.8

40.0

30.0

37.5

46.9

23.4

13.7

45.9

Percentage of longterm average 

annual streamflow

122

107

85

73

205

132

153

125

94

117

147

73

43

143

Values used to estimate streamflow at ungaged streams and recharge near contact between basin fill 

and consolidated rocks. Average annual flow of Martin Creek for period 1923-82, 32 ft /s.

The purpose of the second transient simulation 

period, 1969-78, was to determine the effects of increased pumpage on ground-water flow in the valley. The 10-year period was divided into 10 stress 

periods of 1-year duration. Each stress period was 

divided into two time steps. The first time step for 

each period was 146 days and the second was 219 

days. Doubling the number of time steps for each 

stress period did not change the model results. 

Pumpage and streamflows into the valley for gaged 

streams were averaged for each stress period (table 

8). Streamflows of ungaged streams and recharge 

near the contact between basin fill and consolidated rocks were estimated in the same manner as 

in the first transient simulation.

The purpose of the third transient simulation period, 1979-82, was to determine the effects of cyclic 

runoff and pumpage on ground-water flow during 

each of 4 years. Most of the streamflow enters the 

valley from January through June (see fig. 6), 

whereas pumpage and evapotranspiration dominate 

from April through September. Thus, to simulate 

the cyclic changes in recharge and discharge in 

Paradise Valley, the 4-year simulation period was 

divided into 16 stress periods of 3-month duration:

January-March, April-June, July-September, and 

October-December. Each 3-month stress period 

was divided into two time steps. The first was 36.5 

days and the second was 54.8 days. Doubling the 

number of time steps for each stress period resulted in a slight increase or decrease in water levels at the end of the simulation (generally less 

than 0.2 ft) and a slight increase in the total volumes of water entering and leaving storage. (Volumes increased by about 3 percent.) This in turn 

resulted in an increase in total inflow and outflow 

of about 1 percent during the simulation, which is 

well within the uncertainties of the model results 

and estimated volumes.

Pumpage and evapotranspiration were simulated 

during only the two stress periods that included 

the period from April through September of each 

year. Streamflows into the modeled area for the 

Humboldt and Little Humboldt Rivers and Martin 

Creek were averaged over each 3-month period. 

Streamflows of ungaged streams, including streams 

that were simulated as constant recharge near the 

contact between basin fill and consolidated rocks 

were estimated by first multiplying the average annual streamflows and recharge values used in the
F54 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

steady-state model by the percent of average annual streamflow that occurred during each 3-month 

interval at Martin Creek for the period of record. 

These 3-month average values were then adjusted 

for each 3-month stress period from 1979 through 

1982 by multiplying them by the ratio of the average streamflow at Martin Creek for each 3-month 

stress period to the long-term average streamflow 

for the corresponding 3-month period. Estimated 

net ground-water pumpage, average streamflows at 

Humboldt and Little Humboldt Rivers and Martin 

Creek, and percentage of long-term average 

streamflow at Martin Creek are shown in table 9.

CALIBRATION OF TRANSIENT SIMULATIONS

The same hydraulic properties of the basin-fill 

aquifer that were determined from the best-fit 

steady-state simulation were used in the transient 

simulations for 1948-82. Storage values for each 

model block were needed in the transient simulations because ground-water levels can change as a 

result of changing the quantity and distribution of 

recharge, discharge, or both. Estimates of specific 

yield were used in layer one and storage coefficients were used in layers two and three as explained in the section "Initial Conditions and 

Hydraulic Properties." Water-levels generated from 

the steady-state model were used as starting water 

levels in the first transient simulations from 1948 

through 1968. Water levels generated at the end of 

the simulation from 1948 through 1968 were used 

as starting water levels in the transient simulation 

from 1969 through 1978, and water levels generated at the end of the simulation from 1969 

through 1978 were used as starting water levels in 

the transient simulation from 1979 through 1982.

Calibration of the transient simulations was 

done primarily by adjusting specific yield of model 

layer one. Minor changes to the vertical and horizontal hydraulic conductivities also were made, in 

which case a steady-state simulation was repeated 

with the new values and the computed water levels 

were used as starting water levels in the transient 

simulations. The specific-yield estimates were reduced to 90 percent of the original estimates 

throughout the model in order to duplicate waterlevel fluctuations, particularly in the most heavily 

pumped areas. Perhaps the decrease in calibrated 

specific yield could be a slow drainage of the deposits; however, the 10-percent reduction is not unreasonable considering how specific-yield values were 

estimated. Alternatively, pumpage could have been

increased by 10 percent and the results would have 

been similar. Either case is possible because the 

change is within the accuracy of both estimates of 

specific yield and pumpage.

Conductance values of streambed deposits also 

were adjusted in the transient simulations so as to 

approximate the discharge of Little Humboldt River 

just upstream from where it enters Humboldt 

River (fig. 2). In particular, conductance values of 

streambed deposits were increased 1.2 to 2 times 

for stress periods in which streamflows were well 

above normal. Increasing the conductance values 

for stress periods with above-normal streamflows is 

reasonable in that the width of the streambed increases during high flows, especially when ephemeral Guinboot Lake forms where the sand dunes 

block the channel of Little Humboldt River. In addition, the version of the computer program used to 

model streamflows in Paradise Valley did not account for changing head in the streams during a 

stress period. Although the variation in head is 

less important than stream width during high 

flows, a better technique, if data had been available, would have been to compute the head in the 

stream and allow the conductance value to change 

as a function of discharge.

Streambed-conductance values were not adjusted 

during low streamflow periods because the location 

where streams ceased flowing in the valley was not 

known precisely for each low-flow stress period and 

because most streams ceased flowing only a short 

distance into the valley. Also, streambed-conductance values were not adjusted in transient simulations for stress periods with slightly above normal 

to slightly below normal streamflow.

Adjusting the streambed conductance values 

during the transient simulations resulted in large 

changes in flow to layer one but only small changes 

in simulated water levels. For example, increasing 

streambed-conductance values by 2 for stress periods April-June 1980 and April-June 1982 resulted 

in an increase in stream leakage of 77 ft3/s in 

Paradise Valley for the April-June 1980 stress period and an increase of 38 ft3/s for the April-June 

stress period in 1982. Yet, the mean difference between simulated and observed water levels in 96 

model blocks for the fall of 1982 changed from -0.52 

ft to -0.88 ft and the standard deviation changed 

from 10.5 ft to 10.6 ft. Much of the additional recharge from stream leakage in the simulation was 

discharged as evapotranspiration.

Outflow of the Little Humboldt River in the 

transient simulations is similar to outflow estimated for the period 1948-82, as shown in table
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F55

TABLE 9. Estimates of net ground-water pumpage in both Paradise Valley and adjacent segment of Humboldt River 

Valley, Humboldt County, Nevada, streamflow of gaged streams, and percentage of long-term mean flow at Martin Creek for 3-month periods during 1979-82

[Abbreviation: ft /s, cubic feet per second]

Average streamflow of gaged streams

Martin Creek

Stress period

Year Month/day

1979 1/1-3/31

4/1-6/30

7/1-9/30

10/1-12/31

1980 1/1-3/31

4/1-6/30

7/1-9/30

10/1-12/31

1981 1/1-3/31

4/1-6/30

7/1-9/30

10/1-12/31

1982 1/1-3/31

4/1-6/30

7/1-9/30

10/1-12/30

Net groundwater pumpage 

(ft3/s)

0.1

108

108

.1

.1

105

105

.1

.1

111

111

.1

.1

107

107

.1

Humboldt River

(ft3/s)

540

840

87

40

510

1,300

360

86

160

110

6.4

.4

440

1,200

260

290

Little Humboldt 

River (ft3/s)

8.5

43

19

7.4

11

40

12

7.6

7.6

14

6.8

7.8

11

37

30

8.7

Cubic feet per 

second

28

66

7.0

8.4

68

133

10

11

14

33

4.5

21

74

111

11

12

Percentage of 

long-term 

average 

streamflow

86

80

89

89

209

159

122

115

44

40

57

221

226

133

138

129

1 Annual net pumpage equals sum of four 3-month averages, divided by four.

2 Values used to estimate streamflow at ungaged streams and recharge near contact between basin fill and consolidated rocks. Average 

streamflows of Martin Creek for period 1923-82: January-March, 32.7 fr/s; April-June, 83.3 ft3/s; July-September, 7.88 ft3/s; and 

October-December, 9.40 ft3/s.

10; however, considerable differences exist for individual years. Further adjustments of streambedconductance values during each stress period may 

result in an even better match but are not justified 

because estimated outflows were determined from 

once-a-day readings of a staff gage on the Little 

Humboldt River and because stage-discharge relations were estimated from only a few streamflow 

measurements.

Water levels computed from the transient simulations were compared with measured water levels 

in wells at the end of selected time periods. Water 

levels at the end of the 1948-68 simulation period 

were compared with measured water levels for November 1968 (Harrill and Moore, 1970, table 22). A 

total of 101 model blocks in layer one correspond to 

wells in which water levels were measured. As in 

the steady-state simulation, 95 percent of the simulated water levels were within 20 ft of the measured water levels and more than 70 percent were

within 10 ft (fig. 27). Also shown in figure 27 are 

the percentage of the absolute differences between 

simulated and measured water levels for stress periods ending in 1972, 1975, and 1978. Water levels 

were actually measured in November and December but were assumed the same as the end of the 

year. More than 95 percent of water levels computed from the simulations were within 20 ft of the 

measured water levels at the end of the selected 

years. The distribution of the absolute differences 

is slightly different for the end of 1972 when compared with the other distributions in figure 27. 

However, only 56 water-level measurements were 

made in wells near the end of 1972, and this small 

number of measurements may account for the 

variation. Similar distributions of the absolute differences between simulated and measured water 

levels are shown in figure 28 for the simulation period 1979-82, which included seasonal variations 

in streamflow, evapotranspiration, and pumpage.
F56 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

TABLE 10. Estimated and simulated annual 

streamflow of Little Humboldt River near 

confluence with Humboldt River, Humboldt 

County, Nevada, 1948-82

Streamflow

(acre-feet per year)

Simulation

period 

(years)

1948-533 

1954-584

1959-68

1969

1970

1971

1972

1973

1974

1975

1976

1977

1978

1979

1980

1981

1982

Period of

observed flow 

(month/day) 1

not recorded 

not recorded

no flow

4/09-6/13

5/25-6/26

2/01-6/30

3/11-5/05

3/14-3/22

4/08-5/13

6/12-7/03

no flow

no flow

5/19-6/30

no flow

6/01-6/23

no flow

5/15-6/10

Estimated

25,000 

33,000

0

22,000

3,000

22,000

17,000

50

2,000

700

0

0

2,500

0

1,100

0

1,300

Simulated 

flow2

35,000 

4,500

0

39,000

2,000

16,000

7,000

0

0

2,500

0

0

0

0

10,000

0

5,700

Total, 1948-82, rounded 130,000 120,000

Estimated volumes of streamflow and period of 

observed flow are from Roger Johnson (Nevada Division of 

Water Resources, written commun., 1984).

Model results are sum for each simulation period.

Channel excavated in sand dunes in spring 1953 

(Harrill and Moore, 1970, p. 81).

Channel excavated in sand dunes in June and July 

1958 (Harrill and Moore, 1970, p. 81).

The absolute differences between simulated and 

measured water levels were determined for the 

spring and fall of each year.

AQUIFER RESPONSE

Water levels in most parts of Paradise Valley 

changed little in the transient simulation from 

1948 through 1968. Generally, the changes were 

less than 5 ft in the central part of the valley, although water levels rose more than 10 ft at the extreme northern end of the valley. The cumulative 

quantity of water entering storage from 1948 to 

1968 equaled the cumulative quantity leaving storage. Water entering storage averaged about 5,000 

acre-ft/yr (table 11), which is less than 10 percent 

of the total simulated inflow. Thus, during the period 1948-68, the valley can be considered in a 

state of dynamic equilibrium because water levels 

changed little and because the quantity of water 

entering or leaving storage was a small component 

of the ground-water budget.

Total inflow into the basin-fill aquifer was 

nearly the same as in the steady-state simulation 

and averaged 74,000 acre-ft/yr (table 11) for Paradise Valley. However, discharge from the transient 

model included pumpage, which averaged 3,000 

acre-ft/yr over the simulation period. This reduced 

the quantity of evapotranspiration computed by the 

steady-state simulation, which did not include 

pumpage, from 71,000 to 68,000 acre-ft/yr (compare 

tables 7 and 11).

The transient simulation for 1969-82 was during 

a period when streamflows were generally above 

normal (fig. 7) and pumpage for irrigation increased dramatically. Simulated water levels generally replicated measured water levels for the 

spring of 1982 after a total transient simulation 

period of 35 years, as shown by water-level contours of simulated and measured water levels in 

figure 29. Hydrographs of 16 selected wells, which 

were distributed throughout the valley, are shown 

in figure 30. Locations of the selected wells are 

shown in figure 29. Water levels simulated for the 

spring of 1982 closely matched measured water levels in the central part of the valley (fig. 29), including seasonal fluctuations in the areas of major 

pumpage (fig. 30; major pumping areas are shown 

in fig. 15). However, simulated water levels near 

the northern end of the valley did not match the 

measured water levels as closely. Some of the difference between simulated and measured water 

levels in the northern end of Paradise Valley may 

be caused by uncertainty in the altitudes of wells 

in that part of the valley. Land-surface altitudes of 

many wells in the northern part of the valley are 

not known within 20 ft, and because altitudes of 

water levels are obtained by subtracting depth to 

water from land-surface altitudes, the uncertainty 

in measured water levels is also 20 ft.

The difference also could be caused by differences in location of the screened interval of a well 

with respect to the model node, which is located at 

the center of a model block. Because the model 

simulates an average water level for a block at the 

node, any difference between location of the node 

and the screened interval of a well could result in 

differences between simulated and measured water
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F57

levels, particularly where large vertical and horizontal gradients exist. Both horizontal and vertical 

gradients are larger in the northern end of Paradise Valley than elsewhere in the modeled area.

The general direction of ground-water flow in 

Paradise Valley prior to development was southward toward the Humboldt River. Ground-water 

flow in the adjacent segment of Humboldt River 

Valley was generally parallel to the river and moving westward. Most of the ground-water recharge 

in Paradise Valley was discharged by evapotranspiration along the center of the valley, and little 

ground water from Paradise Valley actually flowed 

into Humboldt River Valley. Since 1968, the result

of increased pumpage in Paradise Valley and in the 

adjacent segment of Humboldt River Valley, particularly near the southern end of the study area, 

has been to alter the direction of ground-water 

flow. As of 1982, pumpage has produced a watertable depression near the southwestern part of 

Paradise Valley and a smaller depression east of 

Golconda Butte (located in Humboldt River Valley), 

causing water to move toward the depressions. Results of model simulations indicate pumpage in 

Paradise Valley reduced evapotranspiration (table 

11). In addition, pumpage near Golconda Butte resulted in a decrease in the quantity of ground-water flow entering Paradise Valley from Humboldt

10

ABSOLUTE DIFFERENCES BETWEEN SIMULATED AND MEASURED WATER LEVELS,

IN FEET

FIGURE 27. Cumulative percentage of absolute differences between simulated and measured water 

levels for fall seasons of 1968, 1972, 1975, and 1978, Paradise Valley, Humboldt County, Nevada.
Q

a »

oT H 

< to

JL °°

CO '|

CD co

-J O

CD tr

i S95 to

SBi-< 

SB

co" &

tD

<!

c ^

IIrT »>

O &

2 § P p.

d-

<<j a

n> co < c p3 i-j

CL 5

03OfC HmDm

m 

z 

O m 

to

03m

m o

z om

toc

3)

m o

m 

3)

i m

m 

to

CUMULATIVE PERCENTAGE OF ABSOLUTE DIFFERENCES BETWEEN 

SIMULATED AND MEASURED WATER LEVELS

tji «+ hd p

o EL P 2 

3 p^3 3

^ £'*$ &

CO S- Oq <<<

Oi M ^ ^ 

co K x-^

^°CD ^ ^

O vi PT'

^, (-J

l_i P CD CO

co 2. ._, o° nh <^ I-1 ISD

ISD tJ

si

CD T3 

. P

evapotranspiration 

in fire3LA. The igu

2 °

pr co

CD <^

O O P l~t

*

&:. 

11o fD 

SP

§»

Oq <

s I

p' ff

c+ O

? 3

o i-1 <

rfi> CO oT

't 00 H-"

O . CD 

O ^

P 3 pj9 ^^ 

CD _ i-j

^^S 

C3~ o co 

75 pr1 CD 

p Pcr "i 

CD crq pi, 

^ CD i-j

1 i p p U; <^ CD P-" 

|_i p O

CO co P

rfx CD pi

00 f^^<

g HI* cr

P O CD 

pi, a <rt-

^ ^

is8

s p p

1

S3 

S

tr1 

p O

"-1 

Oq 

» 

«s 

?S

3 

cr 

pr1 

CD 

co 

P' 

^ 

s

e» * 

h-K CD5

>-1

^5'

o' CD co hi

,-, "i O5 P

CO p 00 ^

I * oq P

"o m P &- 

o 0 P S'

O 14, O- CD
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F59

TABLE 11. Simulated ground-water budgets for basin-fill aquifer in Paradise Valley, Humboldt County, Nevada, for

selected years during 1948-82

[Values in acre-feet per year]

1948-68 1969 1973 1981 1982

RECHARGE

Recharge near contact between basin fill and

consolidated rocks 

Leakage from streams 

Underflow from Humboldt River Valley

Total recharge (rounded)

7,600

65,000

1,300

74,000

15,000

118,000

1,100

134,000

6,800

64,000

1,100

4,300

34,000

800

72,000 39,000

11,000

86,000

700

98,000

DISCHARGE

Net pumpage2

Evapotranspiration

Leakage to streams

Underflow to Himboldt River Valley

Total discharge (rounded)

3,000

68,000

900

1,800

74,000

2,700

73,000

700

2,400

14,000

72,000

700

1,400

38,000

43,000

800

1,700

36,000

52,000

900

1,700

79,000 88,000 84,000 91,000

CHANGE IN STORAGE

Net change in storage

Water into storage

Water out of storage

Model computation error, in percent4

0 55,000 -16,000 -45,000 7,000

5,100 55,000 2,600 29,000 62,000

5,100 100 19,000 74,000 55,000

0.1 0.1 0.1 0.3 0.2

Includes leakage from streams where estimated annual flow is less than 1,200 acre-feet per year.

Total amount pumped, less that which is estimated to return to basin-fill aquifer.

Net change m storage is difference between water added to storage and water removed from storage. Negative value means more 

water is removed from storage than added to storage.

Error is due primarily to truncation and rounding during model computations. Percentage error is calculated from difference between 

all recharge (including water removed from storage) and all discharge (including water added to storage), divided by average of all recharge 

and discharge, and multiplied by 100. Because values for each component in this table are rounded, errors of recharge and discharge do not 

exactly match model computation error.

basin-fill aquifer (fig. 31C). However, the quantity 

of water in storage decreased dramatically after 

1972 because of increased pumpage. Between 1972 

and 1982, a total of 185,000 acre-ft was taken from 

storage. A total net depletion of 110,000 acre-ft 

was computed for the period 1968 through 1982. 

Thus, about 60 percent of the nearly 300,000 acreft of net pumpage (fig. 3LA) was removed from 

storage, or about 50 percent of the 370,000 acre-ft 

of total pumpage. Although most, if not all, pumped 

ground water is removed from storage, the water 

removed is partly replaced by an increase in recharge and a decrease in natural discharge (fig. 

31).

Assessing the quantity of water available in the 

future for pumpage in Paradise Valley is difficult, 

mainly because of the variability of streamflow and 

the location of irrigation wells. The basin seems

suitable for conjunctive use of surface and ground 

water, where ground water is pumped during periods of low streamflow and replenished during periods of high streamflow. For example, model results 

indicate that storage decreased 45,000 acre-ft during the dry year of 1981, whereas during the wet 

year of 1982 storage increased 7,000 acre-ft (table 

11). Replenishment of the basin-fill aquifer occurs 

even during dry years such as 1981. Water is 

added to storage by stream leakage during the 

January-March and October-December periods of 

each year, when pumpage and evapotranspiration 

are minor (table 12). Water is taken from storage 

by pumpage and evapotranspiration during AprilSeptember, when streamflow into the valley is receding. From 1982 through 1984, streamflows were 

consistently above normal. The 1984 water year 

had the greatest streamflows of record for the
F60 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°30'

41°30'

41°00

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

EXPLANATION

Basin fill 

Consolidated rocks

Simulated and measured waterlevel contours-Shows

altitude of ground-water level. 

Contour interval, in feet, is variable. 

Datum is sea level

Simulated water levels in model 

layer one for period one 

ending March 31, 1982

Measured water levels, March 

29-31,1982. Contours at north 

end of valley are based on data 

for wells deeper than 100 feet

Boundary of active model blocks, 

layer one

- - Boundary of study area

~ Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

-^~^ General direction of

simulated ground-water 

flow in model layer one

-4310-

-4310-

21AA, Well used to compare 

measured water levels 

with simulated levels 

in corresponding model 

blocks in layer oneAbbreviated site designation is 

indicated. See figure 30

10 KILOMETERS

FIGURE 29. Simulated and measured ground-water levels in upper 600 feet of basin fill for spring 1982, Paradise Valley,

Humboldt County, Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F61

Humboldt River basin. As a result, water levels 

rose several feet throughout much of Paradise Valley, and thus the quantity of water in storage increased.

EFFECTS OF REDUCED RECHARGE

The withdrawal of large quantities of ground water from the basin-fill aquifer from 1972 through 

1982 coincided with a period of generally above-average streamflow and, hence, recharge in Paradise 

Valley. Results of detailed model simulations indicate that most of the recharge to the southern part 

of Paradise Valley occurred during periods when 

streamflow was sufficient to reach that part of the 

valley. Because pumpage of large quantities of water from the basin-fill aquifer coincided with a period of above-average streamflow, three additional 

simulations were made to determine the effects 

that pumpage may have on the aquifer during periods of less streamflow. Pumpage was divided into 

14 periods of 1-year duration, with the average annual net pumpage for the period 1969-82 used in 

each simulation. Initial water levels for each simulation were the computed water levels at the end of 

the 1948 68 transient simulation. The first simulation assumed that streamflow into the modeled 

area was equal to the long-term average rate 

(1923-82); the second assumed that streamflow 

was equal to a 14-year period of lowest streamflows 

observed at the Martin Creek gage (1923-36; fig. 

7), which averaged 74 percent of the long-term 

average; the third assumed average annual streamflow for the 14-year period 1969-82, which averaged 120 percent of long-term average. The first 

simulation is referred to as average streamflows, 

the second as lowest streamflow, and the third as 

actual streamflows. Simulations of long-term average and lowest streamflows were compared with 

the results of actual streamflows for the period 

1969-82.

Differences in the water-levels at the end of two 

14-year simulations of average and lowest streamflow conditions with respect to the simulation of 

actual streamflows are shown in figure 32A and B. 

Differences in water-levels between the first simulation assuming long-term average streamflows 

and the simulation of actual streamflows for 1969- 

82 were less than 5 ft except at the extreme northern end of the valley, the northwestern side of the 

valley, and the south-central part of the valley 

where water levels were as much as 20 ft lower 

(fig. 32A). The large declines in the northern part

of the valley are the result of lower recharge rates 

assigned to model blocks at the edge of the modeled area. Much of this recharge is from small 

streams, that were not simulated as streams, but 

rather a constant rate was assigned to the first 

model block. The large declines in the south-central 

part of the valley result from streamflows not being sufficient to reach that part of the valley. Thus, 

in the simulation assuming average streamflows, 

more water was removed from storage in the vicinity of the heavily pumped area. When the 14-year 

period of lowest streamflows was simulated, the 

differences in water levels compared with the simulation of actual streamflows for the period 1969-82 

were considerably more (fig. 32.B). A much larger 

area of the valley had additional declines greater 

than 5 ft. Differences of 20 ft or more were simulated at several locations in the valley and result 

from reduced recharge to the basin-fill aquifer.

Hydrographs of water-level changes at six selected model blocks for all transient simulations of 

the 14-year period 1969-82 are shown in figure 33. 

Location of the six blocks is shown in figures 32A 

and 32.B. Water levels in model blocks near where 

major streams enter Paradise Valley and along the 

Humboldt River did not vary between simulations 

(for example, see fig. 33.B). The seasonal change of 

water levels measured in wells near where streams 

are perennial is usually less than 10 ft. Differences 

in water levels between the model simulations increase downstream toward the southern end of the 

valley, as shown in figures 33B-F. These differences are the result of changes in the quantity of 

leakage from streams. The greatest difference in 

water levels among the simulations is along Little 

Humboldt River just east of the most heavily 

pumped area (fig. 33F) and is caused by the presence or lack of streamflow near the model block. 

Results of the simulation suggest that if the climate from 1969 through 1982 had been similar to 

that from 1923 through 1936, the water level in 

well 17AA (location shown in fig. 29 and corresponding to model block 64, 13 in fig. 32) would 

have been about 15 ft lower than that actually observed. However, water levels within the most 

heavily pumped area declined more than 80 ft in 

all simulations (fig. 33.E) and varied less than 7 ft 

between simulations. Water-level declines in this 

area (particularly on the western side) do not seem 

to be as sensitive to changes in streamflows along 

the Little Humboldt River, at least for the 14-year 

period of simulation. This suggests that most of the 

water pumped from the southern end of Paradise 

Valley is from storage.
F62 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

Results of these model simulations suggest that 

if pumpage from 1969 through 1982 had occurred 

during a period of average streamflows, the net 

depletion of ground-water in storage would have 

been 175,000 acre-ft, or about 65,000 acre-ft more 

than was simulated assuming actual streamflows. 

In this simulation, recharge decreased by about 

500 acre-ft/yr at the end of the 14-year period from 

that simulated for 1948-68 and is primarily the result of decreased underflow from Humboldt River 

Valley caused by ground-water pumpage east of 

Golconda Butte. Underflow from Paradise Valley to 

Humboldt River Valley decreased by 700 acre-ft/yr 

after 14 years in the simulation assuming average 

streamflows and was about the same as in the 

simulation using actual streamflows.

If pumpage from 1969 through 1982 had occurred during a period corresponding to lowest 

streamflows from 1923 through 1936, the net 

depletion of ground-water in storage in Paradise 

Valley would have been 240,000 acre-ft, or 130,000 

acre-ft more than was simulated assuming actual 

streamflows. Recharge decreased by 18,000 acre-ft/ 

yr and evapotranspiration decreased by 25,000 

acre-ft/yr at the end of the 14-year simulation from 

that simulated for the period 1948 68. Underflow 

from Humboldt River Valley into Paradise Valley 

decreased by about 400 acre-ft/yr at the end of the 

14-year simulation. Underflow from Paradise Valley to Humboldt River Valley decreased by 700 

acre-ft/yr, the same as in the other simulations. 

Thus, even simulating lowest average streamflows,

4,310

Southwest near Humboldt River

LLJ 

>

LLJ

4,300 -

4,290

WELL 22DD - Altitude, 4,323 feet 

MODEL BLOCK- Row 81, Column 8

LU 4,320 

O

CD

Southeast near Golconda Butte

4,310

£ 4,300

4,290

4,280

WELL 20CDA - Altitude 4,360 feet 

MODEL BLOCK - Row 78, Column 27

MEASURED 

SIMULATED

4,310

4,300

4,290

4,320

4,310

4,300

4,290

4,280

South near Golconda Butte

WELL 15CBC - Altitude, 4,325 feet 

MODEL BLOCK- Row 77, Column 18

South near sand dunes

WELL 36AD - Altitude 4,328 feet 

MODEL BLOCK - Row 71, Column 10

i i i ' i i I I I I I L.

1968 1970 1972 1974 1976 1978 1980 1982 1968 1970 1972 1974 1976 1978 1980 1982

YEAR

FIGURE 30. Measured water levels in selected wells and simulated water levels in corresponding model blocks 

from best-fit transient simulations, 1968-82, Paradise Valley, Humboldt County, Nevada. Location of wells 

is shown in figure 29; model grid blocks are shown in figure 17. Land-surface altitude at well is given.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F63

no additional water was induced from Humboldt 

River Valley to Paradise Valley by pumpage at the 

southern end of Paradise Valley during the 14-year 

period of simulation. This result again illustrates 

the large storage capacity of the basin-fill aquifer 

in Paradise Valley, which acts to buffer short-term 

changes in recharge and discharge.

In summary, reducing recharge over a 14-year 

period to simulate drier conditions resulted in a 

moderate lowering of the water table throughout 

much of the valley, which reduced the quantity of 

water discharged by evapotranspiration. However, 

the simulations did not greatly change the effects 

of ground-water pumping near the southern end of

B

4,320

4,300

4,280

4,260

LU

LU 4,240

CO

LU

West side of heavily pumped area

4,220

4,320

£ 4,310

H 

<

4,300

4,290

WELL 11 ADA - Altitude, 4,384 feet 

MODEL BLOCK - Row 63, Column 7

i i i i i i i i i

4,320

4,300

4,280

4,260

4,240

Near center of heavily pumped area

WELL 6BAD - Altitude, 4,325 feet 

MODEL BLOCK - Row 60, Column 10

i i i i i i i i i i

East side of heavily pumped area

4,280

WELL 17AA-Altitude, 4,322 feet 

MODEL BLOCK-Row 64, Column 13

4,320

4,310

4,300

4,290

East of heavily pumped area

1968 1970 1972 1974 1976 1978 1980 1982

4,280

i i i

WELL 21AA-Altitude, 4,315 feet 

MODEL BLOCK - Row 65 Column 16

1968 1970 1972 1974 1976 1978 1980 1982

YEAR

FIGURE 30. Continued.
F64 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

the valley, nor did the drier conditions greatly increase the underflow from Humboldt River Valley 

during the 14-year period.

SIMULATED RESPONSE TO SELECTED 

DEVELOPMENT SCENARIOS

The general response of the basin-fill aquifer in 

Paradise Valley to five selected development scenarios was evaluated using the calibrated groundwater flow model. Model simulations were initially 

made for an arbitrary period of 600 years: 300 

years of pumping and 300 years of recovery. The 

length of the period was designed to allow the basin-fill aquifer to approach a new equilibrium, and 

then allow it to recover toward original conditions. 

For comparison purposes, the length of the pumping and recovery periods was the same for all basins studied as part of the Great Basin RASA 

project. In two of the scenarios (scenarios two and

three), the length of the pumping period was 

reduced because water levels in several model 

blocks declined below the bottom altitude of the 

block, causing the block to be removed from further 

model computations. The model blocks could not 

resaturate during the recovery period, and recharge assigned to model blocks that went inactive 

was excluded from further computations, thus 

making the simulations unrealistic.

Hydraulic properties of the basin-fill aquifer 

were the same as those used in the best-fit model 

simulations. Streamflows and recharge values assigned to model blocks near the contact between 

the basin fill and consolidated rocks were set equal 

to the long-term average (1923-82). The number 

and locations of wells within the selected pumping 

areas were constrained by the following limitations: (1) only one well was permitted in each 2,500 

by 2,500 ft model block; (2) maximum pumping 

rate was 720 acre-ft/yr (1 ft3/s); (3) no wells were 

located where the initial depth to water exceeded 

200 ft; (4) no wells were located where sand dunes

UJ

>

UJ _l

<

UJ

O

m

4,340

4,330

4'320

North of heavily pumped area

UJ 

UJ

u. 4,310

uj 4,360 

>

UJ _i 

cr

UJ

WELL 12AC - Altitude, 4,368 feet 

MODEL BLOCK - Row 50, Column 7

Central near Little Humboldt River

4,350

n MEASURED 

 SIMULATED

WELL 30BC - Altitude, 4,362 feet 

MODEL BLOCK - Row 42, Column 20

4,340

South central near Little Humboldt River

4,330 -

4,320 -

4,310

4,420

4,410

WELL 13CC - Altitude, 4,334 feet 

MODEL BLOCK - Row 52, Column 18

Northeast near Little Humboldt River

WELL 28ADD - Altitude, 4,418 feet 

MODEL BLOCK - Row 28, Column 23

4,340 I ' I I I I " " " I I I I I i I 4,400

1968 1970 1972 1974 1976 1978 1980 1982 1968 1970 1972 1974 1976 1978 1980 1982

YEAR

FIGURE 30. Continued.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F65

crossed the southern end of the valley; and (5) no 

wells were located in model blocks within layer one 

bounded on two or more sides by inactive blocks.

Ground-water pumpage was assumed equal to 

net pumpage during the hypothetical simulations 

to avoid the necessity of estimating and simulating 

recirculation of some of the pumped water back 

into the aquifer. Ground-water pumpage for the 

first scenario was set equal to net pumpage estimated for 1982. For the last four scenarios, groundwater pumpage was set equal to about 72,000 

acre-ft, or the long-term average annual streamflow into Paradise Valley used in the steady-state

simulations. The five selected scenarios include the 

following:

1. Wells distributed as of 1982, a distribution 

that includes some wells in the adjacent Humboldt 

River Valley;

2. Wells concentrated at the southern end of 

Paradise Valley;

3. Wells concentrated at the northern end of 

Paradise Valley;

4. Wells concentrated along the central part of 

Paradise Valley; and

5. Wells generally distributed throughout the 

area of simulated evapotranspiration in Paradise

LU 

CO 

LU 

>

o

CO

cc

LU

4,440

4,430

4,420

4,410

4,640

4,630

4,620

4,610

West near base of alluvial fan

I I I I I

WELL 23DCB - Altitude, 4,465 feet 

MODEL BLOCK - Row 28. Column 14

I__I

North near town of Paradise Valley

4,600

I I I I I I I I I WELL 14AA - Altitude, 4,635 feet 

MODEL BLOCK- Row 12, Column 12

I I I I

I I I I I I I I

4,520

4,510

4,500

4,490

4,550

4,540

4,530

4,520

North near Big Cottonwood Creek

I I I I I I I I I I I

WELL 25CAC - Altitude, 4,523 feet 

MODEL BLOCK- Row 17, Column 14

I I I

I I I I I I

North near town of Paradise Valley

1968 1970 1972 1974 1976 1978 1980 1982

4,510

I I I I I I I I I I I I I I WELL 20DBAA - Altitude, 4,546 feet 

MODEL BLOCK - Row 14 Column 19

I I I I I I I I I I I 1968 1970 1972 1974 1976 1978 1980 1982

YEAR

FIGURE 30. Continued.
F66 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

Valley prior to ground-water pumpage (fig. 24). 

Characteristics of the five patterns are summarized 

in table 13. Details of the simulations are presented in tables 14-18 and figures 34-38.

SELECTION OF SCENARIOS

The first scenario was evaluated to estimate the 

long-term effects of recent withdrawals, assuming 

climatic conditions equal to average conditions for 

1923-82. Net pumpage for 1982 was used because

it represents pumpage in a relatively stable agricultural community that developed rapidly in the 

1970's. Scenarios two through five were simulated 

to test the concept of sustained yield in basins 

tributary to the Humboldt River where streams flow 

across, and supply water to, the basin-fill aquifer. 

To prevent long-term water-level declines, the 

States of Nevada and Utah, which contain most of 

the Great Basin, allocate water rights for each basin on the basis of the estimated average annual 

recharge. However, in long narrow basins like Paradise Valley and several others, the concentration of 

pumping in a particular area may produce excessive

O

LLJ

=) 

O

300

200 -

100 -

LLJ 

LLJ 

LL

LLJ 

EC 

O

LL -100

O

0) 

Q

200

100

0)

O

i0

LU 

O

-100

200

100

B. Recharge Total recharge

-100

-200

C. Storage

Total storage

1968 1970 1972 1974 1976 1978 1980 1982

FIGURE 31. Cumulative change in (A) annual ground-water discharge, (B) recharge, and (C) storage from results of best-fit transient simulations, 1968-82, Paradise Valley, Humboldt 

County, Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F67

TABLE 12. Simulated ground-water budgets for basin-fill aquifer in Paradise Valley, 

Humboldt County, Nevada, for 3-month periods in 1981

[Values in acre-feet per year]

JanuaryMarch

AprilJune

JulySeptember

OctoberDecember

Total for 

1981

RECHARGE

Recharge near contact between basin fill and

consolidated rocks 3 

Leakage from streams 

Underflow from Humboldt River Valley

Total recharge (rounded)

800

7,000

200

8,000

1,800

15,000

200

17,000

200

2,900

200

3,300

1,500

9,100

200

11,000

4,300

34,000

800

39,000

DISCHARGE

2 Net pumpage

Evapotranspiration

Leakage to streams

Underflow to Humboldt River Valley

Total discharge (rounded)

24

0

400

200

600

19,000

25,000

100

400

44,000

19,000

18,000

100

700

38,000

24

0

200

400

600

38,000

43,000

800

1,700

84,000

CHANGE IN STORAGE

Net change in storage 3

Water into storage

Water out of storage

Model computation error, in percent i

7,500 -27,000 -34,000

13,000 720 14

5,500 28,000 34,000

0.5 0.1 0.1

10,000 -45,000

16,000 29,000

5,700 74,000

0.4 0.3

Includes leakage from streams where estimated annual flow is less than 1,200 acre-feet per year. 1

Total amount pumped, less that which is estimated to return to basin-fill aquifer.

^ Net change in storage is difference between water added to storage and water removed from storage. Negative value means more 

water is removed from storage than added to storage.

Error is due primarily to truncation and rounding during model computations. Percentage error is calculated from difference between 

all recharge (including water removed from storage) and all discharge (including water added to storage), divided by average of all recharge 

and discharge, and multiplied by 100. Because values for each budget component in this table are rounded, errors of recharge and discharge 

do not exactly match model computation error.

water-level declines without reducing the natural 

evapotranspiration in other parts of the basin.

The scenarios were chosen as examples of possible alternatives of future development in basins 

tributary to the Humboldt River. The scenarios did 

not consider the economics of pumping ground water nor, did they include the effects of compacting 

fine-grained sediments that may result from substantial water-level declines in an aquifer. This 

process, which results in subsidence of the land 

surface, has been documented in several areas of 

the western United States (Poland and Davis, 

1969; Chi and Reilinger, 1984) including Las Vegas 

Valley (Bell, 1981). Initially, compaction of the 

fine-grained sediments increases the quantity of 

water released from storage, but as compaction 

continues, the quantity of water decreases with

time. More importantly, much of the water released from compaction of the fine-grained sediments is a one-time occurrence, which can never be 

replaced once pumping ceases and water levels recover. Whether or not pumpage from the basin-fill 

aquifer in Paradise Valley will result in substantial 

compaction of fine-grained sediments is unknown.

DISCUSSION OF RESULTS

Results for each scenario are summarized in 

tables 14 through 18 and figures 34 through 38. 

The results include illustrations depicting waterlevel declines in model layers one and two; changes 

in the average water-level declines within the
F68 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45r 117°30'

41°30'

41°00'

A.

Winnemucca .

 j

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

52,18

EXPLANATION

Basin fill 

Consolidated rocks

Model block selected to illustrate 

differences in water-level 

change during 14-year 

simulation period for 

different streamflow ratesNumbers identify row and column 

of block in model grid. 

See figure 33

Line of equal water-level 

decline-Shows decline 

between model simulation 

for 14-year period 1969-82, 

assuming average streamflow 

rate for that period, and simulations for same 14-year period 

but assuming streamflow rate 

equal to average values for 

long-term period 1923-82. 

Interval 5 feet

Boundary of active model blocks 

Boundary of study area

Boundary between 

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

FIGURE 32. Water-level decline between model simulation for 14-year period 1969-82, assuming average streamflow rate for 

that period, and simulations for same 14-year period but assuming streamflow rate equal to average values for (A) longterm period 1923-82 and (B) 14-year period of lowest flow (1923-36), Paradise Valley, Humboldt County, Nevada.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F69

117°45' 117°30'

41°30'

41°00'

B.

Winnemucca,

R. 37 E. R. 39 E. R. 40 E.

52,18

EXPLANATION

Basin fill 

Consolidated rocks

Model block selected to illustrate 

differences in water-level 

change during 14-year 

simulation period for 

different streamflow ratesNumbers identify row and column 

of block in model grid. 

See figure 33

Line of equal water-level 

decline-Shows decline 

between model simulation 

for 14-year period 1969-82, 

assuming average streamflow 

rate for that period, and simulations for same 14-year period 

but assuming streamflow rate 

equal to average values for 

14-year period 1923-36. 

Interval 5 feet

Boundary of active model blocks 

Boundary of study area

Boundary between 

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

FIGURE 32. Continued
F70

4,440

4,430

LU 

LU

LU 

C/D

LU

o

CD

LU 

LU 

LL

LU 

Q

4,420

4,410

REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

4,340

A. Model block: row 28, column 14

4,410

i i r i i i i i T i i i i i r 

B. Model block: row 28, column 23

C. Model block: row 42, column 20

4,340

1968 1971 1974 1977 1980 1983

4,330

i i i i r r r i i i 

D. Model block: row 52, column 18

4,320

4,320

4,300

4,280

4,260

4,240

4,220

4,320

4,310 

4,300 

4,290 

4,280 

4,270 

4,260' l

niiiiiiii \ 

E. Model block: row 63, column 7

i i i i i

i i i i i i i i i 

F. Model block: row 64, column 13

1968 1971 1974 1977 1980 1983

EXPLANATION

 Water level from best-fit transient simulation

 Water level assuming actual streamflow 

averaged for 1969-82

 Water level assuming streamflow averaged 

for long-term period (1923-82)

A Water level assuming streamflow averaged

for 14-year period of lowest recorded flow 

(1923-36)

FIGURE 33. Water levels at six selected model blocks in layer one showing differences in simulations caused by 

varying streamflow rate, Paradise Valley, Humboldt County, Nevada. Location of model blocks is shown in 

figure 32.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F71

TABLE 13. Description of simulations for selected development scenarios, Paradise Valley, Humboldt County, Nevada

Scenario

1

2

3

4

5

Pumpage1

(acre-feet

per year)

36,000

72,000

72,000

72,000

72,000

Layers and number of 

model blocks with 

pumpage

Distribution of 

2 

pumpage Layers

As of 1982 1

South 1 and 2

North 1 and 2

Central 1

Area of 1

evapotranspiration

Blocks

184

400

340

200

200

Length of pumping and 

recovery periods (years)

Pumping

300

100

75

300

300

Recovery

300

300

300

300

300

Tables and figures 

that summarize 

simulation results

Table

14

15

16

17

18

Figure

34

35

36

37

38

1 All pumpage is assumed to be consumed.

Geographical designations refer to location of simulated pumping on valley floor. In scenario one, areas of pumping 

coincide with those of 1982, and therefore 2,800 acre-ft/yr of pumpage also was simulated in adjacent Humboldt River 

Valley. In scenario five, area of pumping coincides with area of phreatophytes as of 1982.

Pumping periods in scenarios two and three were shortened because water levels in several model blocks declined 

below bottom of block during simulation, and thus specified recharge and discharge were eliminated for remainder of 

simulation.

pumped areas over the simulation period; changes 

in the rate of evapotranspiration and underflow to 

and from Humboldt River Valley, and cumulative 

change in storage during each scenario; and pie 

diagrams showing percentage changes in the quantity of water removed from storage, the quantity of 

decreased evapotranspiration, and the quantity of 

underflow between Paradise Valley and adjacent 

Humboldt River Valley in relation to pumpage. A 

table summarizes changes in the water budget and 

water-level declines at the end of selected time periods for each scenario. The table and figures associated with each scenario are listed in table 13.

The results of the five selected scenarios are consistent with the following statement by Theis 

(1940, p. 277):

Under natural conditions, therefore, previous to development of wells, aquifers are in a state of approximate dynamic equilibrium. Discharge by wells is thus a new 

discharge superimposed upon a previously stable system, 

and it must be balanced by an increase in the recharge to 

the aquifer, or by a decrease in the old natural discharge, 

or by a loss of storage in the aquifer, or by a combination of 

these.

Each scenario includes the processes described 

by Theis in that water is removed from storage, 

natural discharge is decreased, and recharge is increased during the pumping periods.

The water-level declines computed for each scenario are not designed for predicting future water 

levels in Paradise Valley but instead are used to 

describe the effects of different development scenarios on ground-water flow in Paradise Valley

and, hopefully, for similar tributary basins to the 

Humboldt River. Actual future declines in Paradise 

Valley may be different from those simulated because the actual distribution and quantity of 

pumpage may be different from those in the simulations. In addition, the scenarios assume that (1) 

average climatic conditions from 1923 through 

1982 will exist for hundreds of years, (2) all 

pumped water is consumed or the quantity of 

pumpage is a net value (total pumpage less that 

recirculated), (3) all streamflow recharges the basin-fill aquifer as leakage (that is, none is lost directly to evapotranspiration, nor is any leakage 

stored in the unsaturated zone), and (4) no water is 

released by permanent compaction of fine-grained 

deposits as water levels decline.

Although net pumpage was set equal to the longterm average annual streamflow into Paradise Valley for scenarios two through five, in reality not all 

streamflow will be available for capture from 

pumped wells. In the model simulations that describe ground-water flow during the period 1948- 

82, the assumption is that no streamflow is lost to 

evapotranspiration prior to recharging the basinfill aquifer; thus, all streamflow becomes available 

for pumpage. This assumption is reasonable for the 

simulation period 1948-82 because net pumpage 

was considerably less than available streamflow. 

The assumption simplified the model simulations 

for that period. However, the assumption may not 

be reasonable for the selected scenarios, as some 

streamflow will continue to be lost to evapotranspiration. Even though the scenarios may produce 

depths to water exceeding 20 ft below land surface
F72 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

throughout much of the valley and evapotranspiration will cease in the model simulations, plants will 

continue to extract moisture from the unsaturated 

zone near streams or some streamflow will continued to be used for flood irrigation. Thus, the scenarios are limited in their response as to what may 

actually result from the assumed pumpage.

For the first scenario, pumpage was assumed 

equal to the net pumpage for 1982. The estimated 

net pumpage for 1982 was 36,000 acre-ft/yr for 

Paradise Valley and 2,800 acre-ft/yr in Humboldt 

River Valley east of Golconda Butte (fig. 34A). The 

distribution of model blocks that coincide with the 

location of wells that pumped more than 7 acre-ft/ 

yr in 1982 is shown in figure 34A. Model blocks 

with pumpage less than 7 acre-ft/yr are not shown. 

Pumpage was in model layer one, as none of the 

wells pumped in 1982 extended beyond a depth of 

600 ft.

The decline in water levels simulated after 12.5 

years (closest time step in the simulation to actual 

period of drawdown; fig. 34A) is similar to the measured decline between the fall of 1968 and fall of 

1982 (see fig. 26). The slightly greater water-level 

declines in this simulation are the result of at least 

two factors. First, the measured water-level declines are actually for an 11-year period, as pumpage in the valley was minimal until 1972. Second, 

the estimated rate of net pumpage in the study 

area (including adjacent Humboldt River Valley) 

between 1972 and 1982 was not constant at the 

1982 rate but increased from about 12,000 acre-ft/ 

yr in 1972 to about 41,000 acre-ft/yr in 1981 and 

averaged only 78 percent of the quantity simulated.

Maximum water-level decline simulated after 

12.5 years was 89 ft. Water-level declines were 

more than 10 ft in three areas (fig. 34A): (1) at the 

northern end of the valley where Martin Creek enters; (2) in Humboldt River Valley east of Golconda 

Butte; and (3) a large area in T. 38 and 39 N. 

where almost three quarters of the pumpage is located. Elsewhere, water levels were not affected by 

pumping. Underflow from Paradise Valley to Humboldt River Valley decreased 600 acre-ft/yr, and 

underflow from Humboldt River Valley into Paradise Valley also decreased by 160 acre-ft/yr because 

of pumping east of Golconda Butte.

Water-level declines after a simulation period of 

300 years were more than 10 ft throughout the 

southern half of the valley and a small area near 

where Martin Creek enters the valley (fig. 34A). 

The maximum water-level decline was 273 ft along 

the western edge of the most heavily pumped area 

in the southwest part of the valley. The large declines are a result of concentrated pumpage near 

where the basin fill thins rapidly and are less permeable and where little water recharges from 

nearby mountains.

Less than 2 percent of the water pumped after 

300 years was from storage depletion (table 14, fig. 

34£); thus, the simulation was approaching a new 

equilibrium. In this scenario, a total of 1.5 million 

acre-ft of water was depleted from storage in 

Paradise Valley after 300 years (fig. 34D). This accounted for only 14 percent of the total net pumpage. The increase in discharge due to pumping of 

ground water resulted in a decrease of natural discharge by evapotranspiration of 25,000 acre-ft/yr 

(table 14, fig. 34C). It also resulted in an increase 

in underflow from Humboldt River Valley of 7,400 

acre-ft/yr and a decrease in outflow to Humboldt 

River Valley of 1,700 acre-ft/yr (table 14, fig. 34C).

Pumping of ground water at the 1982 rate could, 

in the future, cause water from Humboldt River 

Valley to move northward into Paradise Valley. On 

the basis of the model simulations, if the 1982 

pumping rate continues for 300 years and longterm average streamflows into Paradise Valley remain the same as those estimated for 1923-82, the 

change in ground-water flow between Paradise Valley and Humboldt River Valley would be approximately 9,100 acre-ft/yr, or about 5 percent of the 

average annual streamflow of the Humboldt River 

near Comus.

The scenarios where pumping was concentrated 

either at the southern end (scenario two) or the 

northern end (scenario three) resulted in localized 

water-level declines exceeding 400 ft (figs. 35 and 

36). In the scenario with pumping concentrated at 

the southern end, pumping had little effect on the 

water resources of the northern end of Paradise 

Valley after 100 years. Similarly, concentrating 

pumping at the northern end had little effect on 

the water resources at the southern end of the valley. Concentrating pumping at the southern end of 

the valley produced a reversal in the net flow between Paradise Valley and Humboldt River Valley. 

Prior to development, the estimated net flow of 

ground water was about 500 acre-ft/yr from Paradise Valley into Humboldt River Valley (1,800 acreft of flow out of Paradise Valley less 1,300 acre-ft 

of flow into Paradise Valley; table 15). After 50 

years the net flow was about 15,000 acre-ft/yr into 

Paradise Valley, and after 100 years it was about 

21,000 acre-ft/yr (table 15). Concentrating pumping 

in the northern end of Paradise Valley did not affect 

underflow from Humboldt River Valley (table 16).

Scenarios where pumping was concentrated in 

the central part of Paradise Valley (scenario four) 

and where pumping was distributed throughout the 

area of evapotranspiration (scenario five) extended 

to 300 years as water-level declines never exceeded
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY

117°45' 117°30'

F73

41°30'

41°00'

Winnemucca,-.,

R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

D

EXPLANATION

Basin fill 

Consolidated rocks

Model block with pumped 

irrigation and commercial wells as of 1982

Lines of equal water-level 

decline in model layer one 

(uppermost 600 ft)-Interval, 

in feet, is variable

After 12.5 years of pumping 

After 300 years of pumping

Boundary of active model 

blocks

 - - Boundary of study area

 Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt Rver 

Valley Dotted u nere 

approximately located

-50-

-50-

FIGURE 34. Response of basin-fill aquifer to development scenario one, Paradise Valley, Humboldt County, Nevada. Net pumpage equal to estimated rate of 36,000 acre-feet per year for 1982 and distributed to match location of that pumpage; an 

additional 2,800 acre-feet per year of pumpage simulated in Humboldt River Valley. (A) Water-level declines in model layer 

one after 12.5 and 300 years; (B) average water-level declines in model blocks with pumpage during pumping and recovery 

periods; (C) changes in rate of evapotranspiration and underflow to and from Humboldt River Valley during pumping and 

recovery periods; (D) cumulative change in storage during pumping and recovery periods; and (E) sources of pumped water 

at end of selected time periods.
F74 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

PUMPING RECOVERY

300

10

c.

CE 

U. <

-

O

-10

-20

-30

 x» Inflow from Humboldt River Valley

......... Pytf'OW !°. ............ Tl T^T-. T-v^35

Humboldt River Vafley"

|/12.5 years

Evapotranspiration

1.5 YEARS 25 YEARS 100 YEARS 300 YEARS

EXPLANATION

Sources of pumped water, in percent, 

at end of selected time periods

Decreased outflow to 

Humboldt River Valley

Increased inflow from 

Humboldt River Valley

Water from storage

Reduction in evapotranspiration

FIGURE 34. Continued
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F75

TABLE 14. Simulated ground-water budgets after selected periods of pumping, Paradise Valley, Humboldt

County, Nevada, development scenario one

[Values in acre-feet per year]

Predevelopment

conditions

Conditions after indicated 

period of pumping

1.5

years

12.5 

years

25 

years

50 

years

300 

years

RECHARGE 

Recharge near contact between basin fill and

consolidated rocks1

Leakage from streams

Underflow from Humboldt River Valley

Total recharge (rounded)

DISCHARGE 

Pumpage

Evapotranspiration

Leakage to streams

Underflow to Humboldt River Valley

Total discharge (rounded)

DIFFERENCE (discharge minus recharge) 

COMPUTED STORAGE DEPLETION3

7,200

65,000

1,300

74,000

minor

71,000

800

1,800

74,000

0 

0

7,200

65,000

1,000

73,000

36,000

64,000

800

1,800

103,000

30,000 

28,000

7,200

65,000

1,100

73,000

36,000

55,000

800

1,400

93,000

20,000 

19,000

7,200

65,000

2,000

74,000

36,000

53,000

700

600

90,000

16,000 

15,000

7,200

65,000

4,000

76,000

36,000

50,000

700

300

87,000

11,000 

10,000

7,200

65,000

8,700

81,000

36,000

46,000

700

100

83,000

2,000 

1,000

1 Includes leakage from streams where estimated annual flow is less than 1,200 acre-feet per year.

An additional pumpage of 2,800 acre-feet per year in Humboldt River Valley is included in simulation 

Paradise Valley.

3 Difference between estimates of recharge and discharge and storage depletion represents computational 

truncation and rounding.

but not in budget for 

errors due primarily to

the thickness of layer one. Water-level declines in 

these scenarios were much less than when pumping was concentrated in the southern or northern 

ends (compare figs. 37 and 38 to 35 and 36). These 

lesser water-level declines resulted in a lesser 

quantity of water removed from storage (compare 

figs. 37D and 38D to 35D and 36D). At the end of 

the 300-year pumping period, both scenarios had 

nearly reached a new equilibrium, as less than 5 

percent of the pumped water was from storage 

depletion (tables 17 and 18; figs. 37E and 38E). 

Concentrating pumpage in the central part resulted in water-level declines of more than 200 ft 

after 300 years (fig. 37A); however, average waterlevel declines in the pumped area were less than 

200 ft (fig. 37B). This scenario captured the greatest quantity of evapotranspiration (compare figs. 

34C-38C), as after 300 years only 8,100 acre-ft/yr 

was still being discharged as evapotranspiration 

(table 17). This is even less than in scenario five, 

where pumping was distributed throughout the 

area of evapotranspiration (table 18). Even so, scenario four caused ground water to flow from Humboldt River into Paradise Valley. The net flow, after 300 years, was simulated at 4,300 acre-ft/yr 

(table 17).

Water-level declines in scenario five were even 

less than in scenario four, although shifted to the 

south (compare figs. 37A and 38A). Scenario five 

resulted in the least quantity of water removed 

from storage when compared to the volume of water pumped. However, water-level declines could 

have been further reduced if about 15,000 of the 

20,000 acre-ft/yr of pumpage in T. 37 and 38 N. 

had been moved north of T. 41 N. (see fig. 38A). 

This would have increased declines at the northern 

end of the valley, where about 14,000 acre-ft/yr of 

evapotranspiration was still simulated after 300 

years (table 18) and decreased the quantity of 

underflow induced from Humboldt River Valley.

Concentrating the pumping in the southern and 

northern ends of the valley resulted in substantial 

water-level declines in model layer two (figs. 35B 

and 36B) compared with scenarios where pumping
F76 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH 

117°45' 117°30'

41°30'

41°00'

Winnemucca

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

D

EXPLANATION

Basin fill

Consolidated rocks 

Model block with pumping

Lines of equal water-level 

decline in basin fill 

after 100 years 

of pumping-Interval, in feet, 

is variable

Model layer one (uppermost 

600 feet)

Model layer two (depth interval 

600-1,200 feet)

Boundary of active model 

blocks

 Boundary of study area

 Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

FIGURE 35. Response of basin-fill aquifer to development scenario two, Paradise Valley, Humboldt County, Nevada. Net 

pumpage, 72,000 acre-feet per year, concentrated in southern end of Paradise Valley. (A) Water-level declines in model 

layers one and two after 100 years; (B) average water-level declines in pumped area during pumping and recovery 

periods; (C) changes in rate of evapotranspiration and underflow to and from Humboldt River Valley during pumping 

and recovery periods; (D) cumulative change in storage during pumping and recovery periods; and (E) sources of pumped 

water at end of selected time periods.
CUMULATIVE CHANGE

IN STORAGE, 

IN MILLIONS OF ACRE-FEET

CHANGE IN FLOW RATE,

IN THOUSANDS OF 

ACRE-FEET PER YEAR

AVERAGE WATER-LEVEL

DECLINE IN PUMPED AREA,

IN FEET

 P*. co ro > > 

oooooo 8 8
F78 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH 

117°45' 117°30'

41°30'

41°00'

A.

Winnemucca,

R. 38 E. R. 39 E. R. 40 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

D

EXPLANATION

Basin fill

Consolidated rocks 

Model block with pumping

Lines of equal water-level 

decline in basin fill 

after 75 years 

of pumping-Interval,

in feet, is variable

Model layer one (uppermost 

600 feet)

Model layer two (depth interval 

600-1,200 feet)

Boundary of active model 

blocks

^ Boundary of study area

 Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

-50-

-50-

FIGURE 36. Response of basin-fill aquifer to development scenario three, Paradise Valley, Humboldt County, Nevada. Net 

pumpage, 72,000 acre-feet per year, concentrated in northern end of Paradise Valley. (A) Water-level declines in model 

layers one and two after 75 years; CB) average water-level declines in pumped area during pumping and recovery periods; (C) changes in rate of evapotranspiration and underflow to and from Humboldt River Valley during pumping and 

recovery periods; (D) cumulative change in storage during pumping and recovery periods; and (E) sources of pumped 

water at the end of selected time periods.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F79

B. PUMPING RECOVERY

-60

No change in underlow to or from Humbotclt River Valley

350 400

1.5 YEARS 6.5 YEARS 25 YEARS 75 YEARS

EXPLANATION

Sources of pumped water, in percent, 

at end of selected time periods

Reduction in 

evapotranspiration | Water from storage

FIGURE 36. Continued
F80 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

TABLE 15. Simulated ground-water budgets after selected periods of pumping, Paradise Valley, Humboldt County,

Nevada, development scenario two

[Values in acre-feet per year]

Predevelopment

conditions

Conditions after indicated period of pumping

1.5 

years

12.5 

years

25 

years

50 

years

100 

years

RECHARGE

Recharge near contact between basin fill and 

consolidated rocks 1

Leakage from streams 

Underflow from Humboldt River Valley 

Total recharge (rounded)

7,200

65,000

1,300

74,000

7,200 7,200

65,000 65,000

1,500 4,700

74,000 77,000

7,200

65,000

8,900

81,000

7,200

65,000

15,000

87,000

7,200

65,000

21,000

93,000

DISCHARGE

Pumpage

Evapotranspiration

Leakage to streams

Underflow to Humboldt River Valley

Total discharge (rounded)

DIFFERENCE (discharge minus recharge) 

COMPUTED STORAGE DEPLETION2

minor

71,000

800

1,800

74,000

0 

0

72,000

61,000

800

1,300

135,000

61,000 

59,000

72,000

55,000

800

300

128,000

51,000 

51,000

72,000

52,000

800

200

125,000

44,000 

44,000

72,000

48,000

800

100

121,000

34,000 

33,000

72,000

43,000

800

50

116,000

23,000 

23,000

1 Includes leakage from streams where estimated annual flow is less than 1,200 acre-feet per year.

2 Difference between estimates of recharge and discharge and storage depletion represents computational errors due primarily to 

truncation and rounding.

was concentrated in the central part and distributed throughout the area of evapotranspiration 

(figs. 37B and 38B). The greater declines in layer 

two are the result of simulating pumpage in that 

layer in an attempt to reduce declines in layer one. 

Reducing water-level declines in layer one restricted pumping periods to less than 100 years because water-level declines exceeded the thickness 

of model layer one in several model blocks. The 

greater declines in layer two when pumping at the 

northern end as compared with pumping at the 

southern end is the result of blocks with assigned 

pumping being closer to inactive blocks (no-flow 

boundaries) than at the southern end, and because 

the basin fill thins rapidly near the pumped area, 

resulting in lower transmissivities and storage coefficients in layer two. In addition, pumping at the 

southern end induced additional flow from the 

Humboldt River, thus reducing water-level declines 

in the area.

Leakage from streams in Paradise Valley did not 

increase in the scenarios (tables 14-18) when computed for the entire valley because all streamflow

in these simulations recharged the basin-fill aquifer in Paradise Valley. The only difference between 

the scenarios was where streams stopped flowing 

in the valley. In the steady-state simulations, 

streamflow nearly reached the Humboldt River, 

whereas streamflow ceased several miles farther 

upstream in the selected development scenarios.

A slight reduction (less than 1,000 acre-ft/yr) in 

stream leakage into the basin-fill aquifer was 

simulated when pumping was concentrated at the 

northern end (scenario three). In the steady-state 

simulation, some ground water discharged to a few 

stream reaches near the town of Paradise Valley 

and was simulated as leakage back into the aquifer 

farther downstream. However, in the scenario 

where pumping was concentrated in the northern 

end of the valley, no ground water discharged to 

streams near the town, and therefore the total 

quantity of stream leakage decreased.

Most of the storage in the valley is replaced 

within the first 100 years after termination of 

pumping, and water levels eventually recover to 

within a few feet of their initial levels. The water
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F81

TABLE 16. Simulated ground-water budgets after selected periods of pumping, Paradise Valley, Humboldt County,

Nevada, development scenario three

[Values in acre-feet per year]

Predevelopment

conditions

Conditions after indicated period of pumping

1.5 

years

12.5 

years

25 

years

50 

years

75 

years

RECHARGE

Recharge near contact between basin fill 

and consolidated rocks 1

Leakage from streams 

Underflow from Humboldt River Valley 

Total recharge (rounded)

7,200

65,000

1,300

74,000

7,200

65,000

1,300

74,000

7,200

65,000

1,300

74,000

7,200

65,000

1,300

74,000

7,200

65,000

1,300

74,000

7,200

65,000

1,300

74,000

DISCHARGE

Pumpage

Evapotranspiration

Leakage to streams

Underflow to Humboldt River Valley

Total discharge (rounded)

DIFFERENCE (discharge minus recharge) 

COMPUTED STORAGE DEPLETION2

minor

71,000

800

1,800

74,000

0 

0

72,000

50,000

300

1,800

124,000

50,000 

50,000

72,000

34,000

200

1,800

108,000

34,000 

35,000

72,000

30,000

200

1,800

104,000

30,000 

30,000

72,000

24,000

100

1,800

98,000

24,000 

24,000

72,000

20,000

60

1,800

94,000

20,000 

20,000

1 Includes leakage from streams where estimated annual flow is less than 1,200 acre-feet per year.

2 Difference between estimates of recharge and discharge and storage depletion represents computational errors due primarily to 

truncation and rounding.

removed from storage during pumping is not mined 

because once pumping ceases, storage in the basinfill aquifer is replenished much as it is on a yearly 

basis when the aquifer is replenished in the winter 

and spring and depleted during the summer and 

fall. If pumping should result in the irreversible 

compaction of the fine-grained deposits, then water 

released for the compaction is a one-time source 

that cannot be replenished once pumping stops and 

can be considered as mined. However, this process 

was not analyzed in any of the development scenarios. The effects of irreversible compaction on 

the basin-fill aquifer in Paradise Valley would have 

been to reduce water-level declines in the aquifer 

and to increase the quantity of water removed from 

storage.

In summary, maximum water-level declines and 

consequently the quantity of water removed from 

storage were more in the scenarios where pumping 

was concentrated away from the central part of the 

valley the principal area of stream leakage and

natural evapotranspiration. Because two scenarios 

could not be simulated for the entire 300-year 

period, comparison of the scenarios is summarized 

after 50 years in table 19. In general, concentrating pumping in the northern and central parts of 

the valley and in the area of evapotranspiration 

resulted in the greatest reduction in evapotranspiration, whereas concentrating pumping in the 

southern end of the valley caused the greatest increase in underflow from the adjacent Humboldt 

River Valley and also produced the most water removal from storage, mostly because of higher specific yields in the southern part of the valley. Even 

pumping ground water at the rate and distribution 

estimated for 1982 (where actual pumpage is concentrated at the southern end) also resulted in an 

increase in underflow from Humboldt River Valley 

after 50 years (table 19). Concentrating pumping in 

the northern end of the valley did not affect 

ground-water flow in the southern end of the valley, but water levels in the pumped area could be
F82 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

117°45' 117°30'

41°30'

41°00'

Winnemucca

R. 37 E. R. 38 E. R. 39 E. R. 40 E. R. 41 E.

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

Universal Mercator projection 

Zone 11

10 MILES

10 KILOMETERS

EXPLANATION

Basin fill

Consolidated rocks

Model block with pumping

Lines of equal water-level 

decline in basin fill 

after 300 years of 

pumping-Interval, in feet, 

is variable

Model layer one (uppermost 

600 feet)

Model layer two (depth interval 

600-1.200 feet)

Boundary of active model 

blocks

 Boundary of study area

 Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

-50-

-50-

FIGURE 37. Response of basin-fill aquifer to development scenario four, Paradise Valley, Humboldt County, Nevada. Net 

pumpage, 72,000 acre-feet per year, concentrated in central part of Paradise Valley. (A) Water-level declines in model 

layers one and two after 300 years; CB) average water-level declines in pumped area during pumping and recovery periods; (C) changes in rate of evapotranspiration and underflow to and from Humboldt River Valley during pumping and 

recovery periods; (D) cumulative change in storage during pumping and recovery periods; and (E) sources of pumped 

water at end of selected time periods.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY 

B. PUMPING RECOVERY

F83

Inflow from Humboldt River Valley

Outflow to 

Humboldt River Valley

1 .5 YEARS 25 YEARS 100 YEARS 

EXPLANATION

Sources of pumped water, in percent, 

at end of selected time periods

Decreased outflow to __ Water from storage 

Humboldt River Valley

300 YEARS

Increased inflow from 

Humboldt River Valley

Reduction in evapotranspiration

FIGURE 37. Continued
F84 REGIONAL AQUIFER SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH 

117°45' 117n30'

41°30'

41°00'

A.

Winnemucca,-,

R. 37 E. R. 38 E. R. 39 E.

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

Universal Mercator projection 

Zone 11

R. 40 E. R. 41 E.

10 MILES

10 KILOMETERS

EXPLANATION

Basin fill 

Consolidated rocks

Area of pumped wellsModel blocks with wells are 

shown individually

Lines of equal water-level 

decline in basin fill 

after 300 years 

of pumping-Interval, in feet, 

is variable

Model layer one (uppermost 

600 feet)

Model layer two (depth interval 

600-1,200 feet)

Boundary of active model 

blocks

 . . Boundary of study area

 . . . . Boundary between

Paradise Valley and 

Winnemucca segment 

of Humboldt River

Valley-Dotted where 

approximately located

FIGURE 38. Response of basin-fill aquifer to development scenario five, Paradise Valley, Humboldt County, Nevada. Net 

pumpage, 72,000 acre-feet per year, concentrated in area of evapotranspiration. (A) Water-level declines in model 

layers one and two after 300 years; (B) average water-level declines in pumped area during pumping and recovery 

periods; (C) changes in rate of evapotranspiration and underflow to and from Humboldt River Valley during pumping 

and recovery periods; (D) cumulative change in storage during pumping and recovery periods; and (E) sources of 

pumped water at the end of selected time periods.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY 

B. PUMPING RECOVERY

F85

150

w

UJ TT UL

OH uj 5? ^ cc I-<2

o ^

20

0

-20

-40

-60

-80

c.

Inflow frprn HUrirtbQldt River Valley

' l ' : ' l "i1>T "' 1 " --«

25 YEARS 100 YEARS 300 YEARS

EXPLANATION

Sources of pumped water, in percent, 

at end of selected time periods

Decreased outflow to 

Humboldt River Valley

Increased inflow from 

Humboldt River Valley

Water from storage

Reduction in evapotranspiration

FIGURE 38. Continued.
F86 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

TABLE 17. Simulated ground-water budgets after selected periods of pumping, Paradise Valley, Humboldt County,

Nevada, development scenario four

[Values in acre-feet per year]

Conditions after indicated period of pumping

Predevelopment

conditions

1.5 

years

12.5 

years

25 

years

50 

years

300 

years

RECHARGE

Recharge near contact between basin fill 

and consolidated rocks1

Leakage from streams

Underflow from Humboldt 

River Valley

Total recharge (rounded)

7,200

65,000

1,300

74,000

7,200

65,000

1,300

74,000

7,200

65,000

1,300

74,000

7,200

65,000

1,300

74,000

7,200

65,000

1,400

74,000

7,200

65,000

4,500

77,000

DISCHARGE 

Pumpage

Evapotranspiration

Leakage to streams

Underflow to Humboldt 

River Valley

Total discharge (rounded)

DIFFERENCE (discharge minus recharge) 

COMPUTED STORAGE DEPLETION2

minor

71,000

800

1,800

74,000

0 

0

72,000

37,000

700

1,800

112,000

38,000 

36,000

72,000

21,000

400

1,800

95,000

21,000 

21,000

72,000

17,000

300

1,700

91,000

17,000 

18,000

72,000

14,000

300

1,500

88,000

14,000 

14,000

72,000

8,100

300

200

81,000

4,000 

3,600

1 Includes leakage from streams where estimated annual flow is less than 1,200 acre-feet per year.

2 Difference between estimates of recharge and discharge and storage depletion represents computational errors due 

primarily to truncation and rounding.

lowered below levels that are economical. Thus, 

concentrating pumping in certain areas of the valley could, with time, produce large water-level declines and induce flow from Humboldt River Valley, 

a process that could, in turn, induce flow from the 

Humboldt River.

SUMMARY AND CONCLUSIONS

Paradise Valley, in north-central Nevada near 

Winnemucca, was chosen as one of several basins 

to be studied as part of the Great Basin Regional 

Aquifer-System Analysis (RASA) project. The overall Great Basin RASA project includes much of Nevada, the western half of Utah, and small parts of 

Arizona, California, Oregon, and Idaho. Paradise 

Valley was chosen to represent the many basins 

that drain to the Humboldt River because recent

large increases in ground-water pumping in this 

valley produced water-level declines of more than 

80 ft; the increased pumpage and resulting waterlevel declines helped the analysis of ground-water 

flow by providing an observed stress and response 

that was used to calibrate a model of the basin-fill 

aquifer. The principal technique used to analyze 

flow in the basin-fill aquifer of Paradise Valley and 

to determine the effects of selected ground-water 

development scenarios was a computer program 

that simulates ground-water flow in three dimensions. The valley is an elongate basin that trends 

northeasterly. It is at most 13 mi wide and about 

40 mi long and is bounded by mountains on the 

northern, western, and eastern sides. To the south, 

it merges with Humboldt River Valley.

The major hydrogeologic units in the study area 

were divided into two groups: basin fill that includes dune sands, younger and older alluvial
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F87

TABLE 18. Simulated ground-water budgets after selected periods of pumping, Paradise Valley, Humboldt County,

Nevada, development scenario five

[Values in acre-feet per year]

Predevelopment

conditions

Conditions after indicated period of pumping

1.5 

years

12.5 

years

25 

years

50 

years

300 

years

RECHARGE 

Recharge near contact between basin

fill and consolidated rocks1 7,200

Leakage from streams 65,000

Underflow from Humboldt

River Valley 1,300

Total recharge (rounded) 74,000

7,200

65,000

1,300

74,000

7,200

65,000

2,100

74,000

7,200

65,000

3,400

76,000

7,200

65,000

5,700

78,000

7,200

65,000

12,000

84,000

DISCHARGE

Pumpage

Evapotranspiration

Leakage to streams

Underflow to Humboldt

River Valley

Total discharge (rounded)

DIFFERENCE (discharge minus recharge) 

COMPUTED STORAGE DEPLETION2

minor

71,000

800

1,800

74,000

0 

0

72,000

43,000

400

1,800

117,000

43,000 

42,000

72,000

27,000

300

1,200

100,000

26,000 

26,000

72,000

23,000

200

1,000

96,000

20,000 

20,000

72,000

20,000

200

600

93,000

15,000 

15,000

72,000

14,000

200

100

86,000

2,000 

2,600

1 Includes leakage from streams where estimated annual flow is less than 1,200 acre-feet per year.

2 Difference between estimates of recharge and discharge and storage depletion represents computational errors due primarily to 

truncation and rounding.

gravel, sand, silt, and clay, and lesser quantities of 

lacustrine and volcanic deposits; and consolidated 

rocks, which are exposed in the surrounding mountains and presumably underlie the basin fill. The 

basin fill forms the principal aquifer in Paradise 

Valley. These deposits may exceed 8,000 ft in 

thickness near the middle of the valley.

Both steady-state and transient models were 

used in the analyses of the basin-fill aquifer. The 

steady-state model was calibrated primarily by adjusting the vertical and horizontal hydraulic conductivities until simulated water levels matched 

measured water levels between 1948 and 1968. 

The conductance values of streambed deposits also 

were adjusted until simulated stream losses approximated the estimated losses. Three transient 

models were used to simulate ground-water flow 

from 1948 through 1982. The first transient model 

simulated the period 1948-68, in which streamflows and pumpage were averaged for 3- to 6-year 

periods. The second transient model simulated the 

period 1969-78, in which streamflows and pumpage were averaged for each year. The third model 

simulated the period 1979-82, in which streamflows and pumpage were averaged for 16 threemonth periods. These transient models were 

calibrated primarily by adjusting the specific yield 

of the basin-fill aquifer and the conductance values 

of streambed deposits until simulated water levels 

matched measured water levels at the end of 12 selected time periods between 1948 and 1982. During 

the transient simulations, streambed-conductance 

values were increased for time periods of abovenormal streamflow because stream widths and 

depths generally increased, resulting in greater infiltration.

Estimates of hydraulic conductivity in the upper 

600 ft of basin fill were determined mainly from
F88 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

TABLE 19. Summary of hydrologic effects on basin-fill aquifer in Paradise Valley, Humboldt County, Nevada after 50 

years of pumping, using five selected development scenarios

Pumpage at net 

rate estimated for

1992; wells

distributed as in

1982

Pumpage at estimated rate of recharge; wells concentrated in:

Southern end Northern end Central part of Area of 

of valley of valley valley evapotranspiration

Development scenario 1234 

Pumpage 

(acre-feet per year) a36,000 72,000 72,000 72,000

Increased underflow from Humboldt 

River Valley (acre-feet per year)b 2,700 13,000 0 120

Decreased underflow to Humboldt

River Valley (acre-feet per year)b 1,500 1,700 0 300 

Decreased evapotranspiration

(acre-feet per year)6 21,000 24,000 48,000 57,000 

Storage depletion

(millions of acre-feet) 0.7 2.1 1.5 0.9

Maximum water-level decline (feet)c

Layer 1 170 280 310 110 

Layer 2 130 330 440 96

5

72,000

4,500

1,600

51,000

1.0

99

82

a Does not include net pumpage of 2,800 acre-feet per year in adjacent Humboldt River Valley, which was included in model 

simulation.

Changes are relative to results from model simulations of predevelopment conditions (1948-68).

c Model layer one corresponds to uppermost 600 feet of basin fill. Model layer two corresponds to basin fill between 

depths of 600 and 1,200 feet.

specific-capacity data. The average hydraulic 

conductivity for 90 wells is S.TxlO"4 ft/s (32 ft/d), 

assuming a specific yield of 0.3, and 4.1X10"4 ft/s 

(35 ft/d), assuming a specific yield of 0.1. Higher 

hydraulic conductivities are generally in the center 

of the valley, where well-sorted stream deposits are 

common, and less along the margins, where poorly 

sorted fan deposits are dominant. The average hydraulic conductivity in model layer one is 2xlO~4 ft/ 

s (17 ft/d) for the calibrated model, or a factor of 

two less than that estimated from specific-capacity 

data, but the general distribution is the same. The 

reason for a decrease in the model-calculated hydraulic conductivities is that the values represent 

an average of both coarse- and fine-grained deposits, whereas hydraulic conductivities estimated 

from specific-capacity data generally represent the 

coarser deposits.

The same distribution of horizontal hydraulic 

conductivity is used in model layers two and three, 

except that the values are reduced 50 percent for 

every 1,200 ft of additional depth. Vertical hydraulic conductivities used to simulate flow between 

model layers averaged 3xlO~6 ft/s (0.3 ft/d) between

model layers one and two and 5x10 7 ft/s (0.04 ft/d) 

between model layers two and three.

Specific yield for the upper 200 ft of saturated 

basin fill was estimated by dividing the terms (generally lithologic descriptions) described in drillers' 

logs into six categories, each of which was assigned 

a specific-yield value. The highest specific yield is 

more than 20 percent, whereas the lowest value is 

less than 10 percent. The distribution of specific 

yield is similar to the distribution of hydraulic conductivity, whereby higher values are generally in 

the center of the valley and lower values along the 

margins. Specific yield was reduced by 10 percent 

during calibration of the model to duplicate the water-table depression near the southern end of the 

valley and seasonal water-level fluctuations 

throughout the study area. A specific-storage value 

of 2xlO~6 per foot was used for the deeper deposits, 

on the basis of information obtained in similar basins that contain a mixture of coarse- and finegrained deposits.

Recharge to the basin-fill aquifer is primarily 

from streams. Numerous small streams begin in 

the surrounding mountains, mostly at the northern
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F89

end of the valley. The streams may be perennial in 

the mountains but usually lose their flow as they 

cross the fans into the valley. Streamflow onto the 

valley floor occurs normally during spring snowmelt. Two major streams (Martin Creek and Little 

Humboldt River) enter the valley through narrow 

canyons along the northeastern side. These 

streams join about halfway down the center of the 

valley and account for more than half of the estimated average annual recharge. During periods of 

high runoff, water flows to sand dunes that cross 

the southern end of the valley, where it forms a 

lake that remains until the water seeps into the 

ground, is evaporated, or is drained when a channel is dredged through the dunes. Prior to the 

early 1970's, discharge from the basin-fill aquifer 

in Paradise Valley was mainly by evapotranspiration, primarily along the valley floor where the 

depth to ground water was less than 25 ft. Evapotranspiration was highest in areas where the water 

table was near land surface and decreased as the 

depth to water increased. Much of the evapotranspiration was in the areas where streams were the 

source of ground water; thus, most of the water 

that recharged the basin-fill aquifer was discharged nearby. In the model simulations, no 

evapotranspiration was assumed when the depth to 

water below land surface exceeded 25 ft.

Prior to large quantities of pumpage in Paradise 

Valley, ground water flowed toward the Humboldt 

River; however, only a small part of the total recharge to the valley may have actually reached the 

river. Results from the best-fit steady-state simulation indicate that only about 1,800 acre-ft/yr of 

ground water left Paradise Valley near the channel 

of the Little Humboldt River as underflow to the 

adjoining Humboldt River Valley, and that perhaps 

as much as 1,300 acre-ft/yr entered Paradise Valley 

as underflow from Humboldt River Valley near 

Golconda Butte.

The quantity of water pumped from wells prior 

to 1948 was estimated to be less than 200 acreft/yr and was used for domestic purposes and livestock. Pumping of ground water began to increase 

in the mid 1950's, when several wells were drilled 

to supplement surface-water supplies used mostly 

to irrigate alfalfa and hay. Pumpage increased 

slowly to about 6,800 acre-ft/yr in 1970. It increased dramatically in the 1970's, when the southern end of the valley was determined to be ideal 

for growing potatoes. The estimated quantity of 

ground water pumped in 1982 was about 44,000 

acre-ft, concentrated in the southern end of the valley. An additional 3,800 acre-ft was pumped from

the basin fill in the adjacent Humboldt River Valley.

The increased pumpage has altered the direction 

of ground-water flow. The general direction of flow 

prior to development was from the margins of the 

valley to the center and then southward toward the 

Humboldt River, even though most of the water 

was discharged by evapotranspiration in the valley. 

By 1982, ground-water flow had shifted generally 

toward the water-table depression caused by pumping near the southern end of the valley.

The increase in pumpage occurred during a 14- 

year period of generally above-normal streamflows 

into the valley (120 percent of the long-term average for 1923-82). An extra 120,000 acre-ft of water 

was simulated as recharge to the basin-fill aquifer 

from 1969 through 1982. The quantity of water removed from storage between 1969 and 1982 was 

110,000 acre-ft. Water in storage increased 75,000 

acre-ft from 1969 through 1972, then decreased 

185,000 acre-ft from 1973 through 1982. The quantity of water removed from storage from 1972 

through 1982 accounted for about 50 percent of the 

total pumpage and 60 percent of the net pumpage.

Simulations assuming different quantities of 

streamflow indicate that if development had occurred during a period when flow equaled the longterm average for 1923-82, water-level declines near 

the southern end of the valley might have been as 

much as 20 ft more and an additional 65,000 acreft might have been removed from storage due to a 

reduction in recharge near the southern end of the 

valley. If, instead, development had occurred during a period when flow equaled the lowest recorded 

14-year period from 1923 through 1936 (74 percent 

of the long-term average for 1923-82), water-level 

declines in the southern end would be similar to 

those of average conditions, but because of reduced 

recharge farther up valley, water levels might have 

declined 5 ft throughout much of the valley and an 

additional 130,000 acre-ft of water might have 

been removed from storage.

Five different development scenarios were simulated to determine what effects different pumping 

patterns might have on the basin-fill aquifer in 

Paradise Valley and, by analogy, in other tributary 

basins to the Humboldt River. Net pumpage for the 

first scenario was set equal to that estimated for 

1982, and was about 36,000 acre-ft/yr in Paradise 

Valley and 2,800 acre-ft/yr in adjacent Humboldt 

River Valley. This scenario was designed to test 

the long-term effects of the recent pumpage on the 

basin-fill aquifer. Net pumpage in the last four scenarios was set equal to 72,000 acre-ft/yr, but the
F90 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

location of pumpage in Paradise Valley changed. 

The distribution of pumpage in the valley for each 

simulation included, respectively, wells concentrated at the southern end; wells concentrated at 

the northern end; wells concentrated along the central part; and wells distributed throughout the 

area of evapotranspiration prior to pumpage. All 

five scenarios are based on the assumptions that 

average climatic conditions for 1923-82 would continue for hundreds of years, that all streamflow recharges the basin-fill aquifer as leakage, and that 

no water is released from permanent compaction of 

fine-grained deposits. Although these assumptions 

limit the results of the hypothetical simulations, 

the general conclusions regarding the model simulations are nonetheless valid.

Results from the first scenario, which is based 

on an assumed net pumpage equal to that of 1982, 

produced water-level declines in the southern part 

of the valley of more than 200 ft after 300 years. 

These declines were near the area where pumpage 

was most concentrated in 1982. The simulation 

also indicated ground-water flow from Humboldt 

River Valley into Paradise Valley. After 50 years, 

ground-water inflow to Paradise Valley from Humboldt River Valley increased about 2,700 acre-ft/yr; 

after 300 years, the flow increased about 7,400 

acre-ft/yr. Similarly, ground-water outflow from 

Paradise Valley to Humboldt River Valley decreased 1,500 acre-ft/yr after 50 years, and 1,700 

acre-ft/yr after 300 years.

Concentrating pumpage at the northern and 

southern ends of Paradise Valley and away from 

the major area of stream leakage and natural 

evapotranspiration resulted in the greatest waterlevel declines, which exceeded 400 ft after 75 years 

of pumping in the northern end and 100 years of 

pumping in the southern end. Both scenarios resulted in greater quantities of water being removed 

from storage. In addition, concentrating pumpage 

at the southern end of the valley produced a reversal in the net flow between Paradise Valley and 

Humboldt River Valley. Prior to development, the 

estimated net flow of ground water was about 500 

acre-ft/yr from Paradise Valley into Humboldt 

River Valley. After 50 years with pumping concentrated at the southern end of the valley, the net 

flow was from Humboldt River Valley into Paradise 

Valley at a rate of about 15,000 acre-ft/yr and increased to about 21,000 acre-ft/yr after 100 years.

Concentrating pumpage in the central part of 

the valley near the area where major streams recharge the basin-fill aquifer and where natural 

evapotranspiration occurs resulted in water-level

declines generally less than 200 ft after 300 years. 

Water-level declines were slightly less when wells 

were distributed throughout the area of evapotranspiration. This simulation also had the least 

quantity of water removed from storage compared 

with the volume of water pumped. However, the 

simulation where pumpage was distributed throughout the area of evapotranspiration resulted in less 

capture of evapotranspiration and more underflow 

from Humboldt River Valley than the simulation 

where pumpage was concentrated in the central 

part. These differences were caused by pumpage 

in the area of evapotranspiration extending farther 

south, closer to the boundary between the two valleys.

In conclusion, concentrating pumpage in the 

northern and southern ends of Paradise Valley 

might produce large water-level declines without 

effectively reducing the natural discharge of ground 

water in the central part of the valley. In addition, 

concentrating pumpage in the southern end of the 

valley (the present-day pattern) might induce flow 

from Humboldt River Valley; depending on the 

quantity of pumpage, this in turn could affect the 

flow in the Humboldt River.

REFERENCES CITED

Bell, J.W., 1981, Subsidence in Las Vegas Valley: Nevada Bureau of Mines and Geology Bulletin 95, 84 p.

Bredehoeft, J.D., 1963, Hydrogeology of the lower Humboldt 

River basin, Nevada: Nevada Department of Conservation 

and Natural Resources, Water Resources Bulletin 21, 50 p.

Chi, S.C., and Reilinger, R.E., 1984, Geodetic evidence for subsidence due to ground-water withdrawal in many parts of 

the United States of America: Journal of Hydrology, v. 67, 

no. 2, p. 155-182.

Cohen, Philip, 1961, Specific yield of sediments of the Humboldt River Valley, Humboldt County, Nevada, in Geological Survey Research 1961: U.S. Geological Survey 

Professional Paper 424-C, p. 43-45.

 1962, Estimating porosity from specific gravity, in Geological Survey Research 1962: U.S. Geological Survey Professional Paper 450-B, p. 41-43.

 1963a, Specific-yield and particle-size relations of Quaternary alluvium, Humboldt River Valley, Nevada: U.S. 

Geological Survey Water-Supply Paper 1669-M, 24 p. 

-1963b, An evaluation of the water resources of the Humboldt River Valley near Winnemucca, Nevada: Nevada Department of Conservation and Natural Resources, Water 

Resources Bulletin 24, 104 p.

 1964, Water in the Humboldt River Valley near 

Winnemucca, Nevada: Nevada Department of Conservation 

and Natural Resources, Water Resources Bulletin 27, 68 p.

Cohen, Philip, and others, 1965, Water resources of the Humboldt River Valley near Winnemucca, Nevada: U.S. Geological Survey Water-Supply Paper 1795, 143 p.
GROUND-WATER FLOW AND SIMULATED EFFECTS OF DEVELOPMENT IN PARADISE VALLEY F91

Cordell, Lindreth, 1970, Iterative three-dimensional solution of 

gravity anomaly data: U.S. Geological Survey Computer 

Contribution 10, 13 p. [Available only from National Technical Information Service, U.S. Department of Commerce, 

Springfield, VA 22161, accession no. PB-196 979.]

Davis, J.C., 1973, Statistics and data analysis in geology: New 

York, John Wiley, 550 p.

Durbin, T.J., Kapple, G.W., and Freckleton, J.R., 1978, Twodimensional and three-dimensional digital flow models of 

the Salinas Valley ground-water basin, California: U.S. 

Geological Survey Water-Resources Investigations Report 

78-113, 134 p.

Flynn, Thomas, 1981, Paradise Valley study area, in Trexler, 

D.T., Koenig, B.A., Flynn, Thomas, Bruce, J.L., and 

Ghusm, George, Jr., Low-to-moderate temperature geothermal resource assessment for Nevada, area specific studies: 

Nevada Bureau of Mines and Geology Final Report DOE/ 

NV/10039-3 (June 1, 1980-August 30, 1981), p. 83-159.

Haeni, F.P., 1988, Application of seismic-refraction techniques 

to hydrologic studies: U.S. Geological Survey Techniques of 

Water-Resources Investigations, Book 2, Chap. D2, 86 p.

Hardman, George, 1936, Nevada precipitation and acreages of 

land by rainfall zones: University of Nevada, Reno, Agricultural Experiment Station report, 10 p.

Harrill, J.R., and Moore, D.O., 1970, Effects of ground-water 

development on the water regimen of Paradise Valley, 

Humboldt County, Nevada, 1948-68, and hydrologic reconnaissance of the tributary areas: Nevada Division of Water 

Resources, Bulletin 39, 123 p.

Harrill, J.R., Welch, A.H., Prudic, D.E., Thomas, J.M., Carman, 

R.L., Plume, R.W., Gates, J.S., and Mason, J.L., 1983, 

Aquifer systems in the Great Basin region of Nevada, 

Utah, and adjacent states A study plan: U.S. Geological 

Survey Open-File Report 82-445, 49 p.

Johnson, A.I., Moston, R.P., and Morris, D.A., 1968, Physical 

and hydrologic properties of water-bearing deposits in subsiding areas in central California: U.S. Geological Survey 

Professional Paper 497-A, 71 p.

Loeltz, O.J., Phoenix, D.A., and Robinson, T.W., 1949, Ground 

water in Paradise Valley, Humboldt County, Nevada: Nevada State Engineer, Water Resources Bulletin 10, 61 p.

Lohman, S.W., 1979, Ground-water hydraulics: U.S. Geological 

Survey Professional Paper 708, 70 p.

McDonald, M.G., and Harbaugh, A.W., 1988, A modular threedimensional finite-difference ground-water flow model: 

U.S. Geological Survey Techniques of Water-Resources Investigations, book 6, chap. Al, 586 p.

Meyer, R.R., 1963, A chart relating well diameter, specific 

capacity, and storage, in Bentall, Ray, ed., Methods of determining permeability, transmissibility, and drawdown: 

U.S. Geological Survey Water-Supply Paper 1536-1, p. 338- 

340.

Moore, D.O., 1968, Estimating mean runoff in ungaged semiarid areas: Nevada Division of Water Resources, Bulletin 

36, 11 p.

Morris, D.A., and Johnson, A.I., 1966, Summary of hydrologic 

and physical properties of rock and soil materials, as analyzed by the Hydrologic Laboratory of the U.S. Geological 

Survey, 1948-60: U.S. Geological Survey Water-Supply Paper 1839-D, 41 p.

Nelson, G.L., 1982, Vertical movement of ground water under 

the Merrill Field landfill, Anchorage, Alaska: U.S. Geological Survey Open-File Report 82-1016, 24 p.

Poland, J.F., and Davis, G.H., 1969, Land subsidence due to

withdrawal of fluids, in Varnes, D.J., and Kiersch, George, 

eds., Reviews in engineering geology, v. II: Boulder, Colo., 

Geological Society of America, p. 187-269.

Prudic, D.E., 1989, Documentation of a computer program to 

simulate stream-aquifer relations using a modular, finitedifference, ground-water flow model: U.S. Geological Survey Open-File Report 88-729, lia p.

Robbins, S.L., Prudic, D.E., Schaefer, D.H., and Clutsom, F.G., 

1985, Principal facts and density estimates for borehole 

gravity stations in three water wells located in Dixie and 

Paradise Valleys, Nevada: U.S. Geological Survey OpenFile Report 85-426, 20 p.

Robinson, T.W., 1965, Water-use studies utilizing evapotranspiration tanks, in Cohen, Philip, and others, Water resources 

of the Humboldt River Valley near Winnemucca, Nevada: 

U.S. Geological Survey Water-Supply Paper 1795, p. 83-93.

Rush, F.E., 1968, Index of hydrographic areas: Nevada Division of Water Resources, Information Series Report 6, 38 p.

Sales, J.K., 1966, Structural analyses of the Basin and Range 

Province in terms of wrench faulting: University of Nevada-Reno, Ph.D. thesis, 178 p.

Schaefer, D.H., 1988, Bouguer gravity anomaly maps of Paradise, Stagecoach, Dixie, Fairview, and Stingaree Valleys, 

northwestern Nevada: U.S. Geolological Survey Geophysical Investigations Map GP-985.

Schaefer, D.H., Duffrin, E.G., and Plume, R.W., 1986, Principal 

facts for gravity stations in Paradise and Stagecoach Valleys, Humboldt and Lyon Counties, Nevada: U.S. Geological Survey Open-File Report 85-694, 15 p.

Scott, B.R., Smales, T.J., Rush, R.E., and Van Denburgh, A.S., 

1971, Nevada's water resources: Nevada Division of Water 

Resources, Water for Nevada Report 3, 87 p.

Smith, W.O., 1961, Mechanism of gravity drainage and its relation to specific yield of uniform sands: U.S. Geological Survey Professional Paper 402-A, 12 p.

Stewart, J.H., 1980, Geology of Nevada: Nevada Bureau of 

Mines and Geology Special Publication 4, 136 p.

Telford, W.M., Geldart, C.D., Sheriff, R.E., and Keys, D.A., 

1976, Applied geophysics: Cambridge, England, Cambridge 

University Press, 860 p.

Theis, C.V., 1940, The source of water derived from wells; essential factors controlling the response of an aquifer to development: Civil Engineering, v. 10, no. 5, p. 277-280.

 1963, Estimating the transmissibility of a water-table 

aquifer from the specific capacity of a well, in Bentall, Ray, 

ed., Methods of determining permeability, transmissibility, 

and drawdown: U.S. Geological Survey Water-Supply Paper 1536-1, p. 332-336.

U.S. Geological Survey, 1960, Compilation of records of surface 

waters of the United States through September 1950, part 

10, the Great Basin: U.S. Geological Survey Water-Supply 

Paper 1314, 485 p.

 1963, Compilation of records of surface waters of the 

United States, October 1950 to September 1960, part 10, 

the Great Basin: U.S. Geological Survey Water-Supply 

Paper 1734, 318 p. 

-1962-65, Surface water records for Nevada, 1961-64:

Carson City, Nev., U.S. Geological Survey water-data reports (published annually).

 1966-75, Water resources data for Nevada, 1965-74: 

Carson City, Nev., U.S. Geological Survey water-data reports (published annually).

 1976-84, Water resources data, Nevada, water years 

1975-83: U.S. Geological Survey Water-Data Reports NV-
F92 REGIONAL AQUIFER-SYSTEM ANALYSIS GREAT BASIN, NEVADA-UTAH

75-1 to NV-83-1 (published annually). 

Walton, W.C., 1962, Selected analytical methods for well and

aquifer evaluation: Illinois State Water Survey Bulletin 49,

81 p. 

Willden, Ronald, 1964, Geology and mineral deposits of Humboldt County, Nevada: Nevada Bureau of Mines Bulletin 

59, 154 p.

Williamson, A.K., Prudic, D.E., and Swain, L.A., 1989, Regional 

aquifer-system analysis of the Central Valley of California: 

U.S. Geological Survey Professional Paper 1401-D, 127 p.

U.S. GOVERNMENT PRINTING OFFICE: 1996 - 774-045 / 20022 REGION NO. 8
SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS

Periodicals

Earthquakes & Volcanoes (issued bimonthly). 

Preliminary Determination of Epicenters (issued monthlv).

Technical Books and Reports

Professional Papers are mainl) comprehensive scientific reports 

of wide and lasting intetest and importance to professional scientists 

and engineers. Included are reports 0:1 the results of resource studies 

and of topographic, hydrologic, and geologic imestigations. The) also 

include collections of related papers addressing different aspects rf;, 

single scientific topic,

Bulletins contain significant data and interpretations that are of losting scientific interest but are general!) more limited in acone or t^eo 

graphic coverage than Professional Papers The) include the results, nf 

resource studies and of geologic and typographic investigations, as %ejl 

as collection^ of short papers related 'o a specific topic.

Water-Supply Papers an: compreneiwve reports that present sic 

nificant interpretive results ol hydrologic investigations of wide interest 

to professional geologists. h\dn"logists. and engineers. The series cover\ 

investigations in all phases of hydrology including hydtogeology. amiability of water, quality of wate;. and use of water

Circulars present administrate infommtinn or important sn^ntific information of \\ide popular interest m a format designed for ct'stnhution at no cost to the public, inlorniatiun is usually ot shori-term 

interest

Water-Resource Investigations Reports are papers oJ at; 

interpretive natuie made nvmlable to the publ;*. ouLskde the tormai 

USGS publications series. Copies are reproduced or_ request unlike 

formal USUS publications, and (he\ aru also available for public 

inspection at depositories indicated m TSGS catalogs.

Open-File Reports include unpublished manuscript reports, maps, 

and other material that are made available foi public cousuitation a; 

depositories. They are a nonpcrmai.ent form of publication that ma\ 

be cited in other publications as sources (f information

Maps

Geologic Quadrangle Maps ate multicolor geologic maps uc t',> 

pographic bases in 7 /^- or 15-minute quadrangle formats locales nianHv 

1:24.000 or 1.62JOO) showing bedrock, surl'icial. or engineering geology. Maps generally include bnef *e\ts. some maps include stru-.'turc 

and columnar sections only.

Geophysical Investigations Maps ate jr. topographic or platnmet 

ric bases at various scales: the} sho\\ lesuits of sur.eys usmt. 

geophysical techniques, such as gravity magnetic, seismic or radioactinty, \\hich reflect subsurface structures that are of economic o; geei'^gic significance. Many map.s include correlations with the geology

Miscellaneous Investigations Series Maps are on planimetrit or 

topographic bases nf icgular and irregular areas at various scales thc\ 

present a wide variety ul format and suhject matter. The senes also 

includes 7 Xz-minutc quadrangle photog^ologic maps on plan<metric 

bases thai sho\\ geology as interpreted rr<)?n aeriai photographs. Ser^s 

also includes maps of Mnra and the Moon.

Coal Investigations Maps are geologic maps on topographic or 

planimetric bases at various scales showing bedrock or surficial geology, stratigraphy and structural relations in certain coal-resource 

areas.

Uil and Gas Investigations Charts show stratigraphic information for certain oil and gas fields and other areas having petroleum 

potential.

Miscellaneous Field Studies Maps are multicolor or black-anj- 

\^hitJ maps on topographic nr planimctric bases on quadrangle or irregular areas »[ various scales, ^re-1971 maps show bedrock geology 

m reiatmn to specific mining or mineral-deposit problems; post-1971 

maps ar? primarily black-and-white map^ on various subjects, such as 

environment:!] studies or wilderness mineral investigations.

Hydrologic Investigations Atlases are multicoloi or hlack-and- 

\vhile maps ^n topographic or plam'nietric h;tses presenting a wide range 

"f genh\drolygk" dara of both regular and irregular areas: principal 

sculp is !.24,000, and regional studies are at 1:250,000 scale or ^mallei.

Catalogs

Permanent catalogs, as \tell as some others, giving comprehensive 

icings of V S Geological Sur\cy publications are axailabb under the 

'.oncitions indicated below from the t\S. GeologicaJ Survey. Books 

/ind (Jpen-l'ile Reports Sales. Federal Center. Hox 252R6. Denver, CO 

S'l?2\ iSee latest Price and Availability List t

"[publications of the Geological Survey, 1879-1961" may be purUtiisru ^\ mail and o\er the countct in paperback book form and as a 

act of microfiche

"Publications of the Geological Survey, 1962-1970" may be purchased by mml and over the counter in paperback book form and as a 

set of 'inciofiche.

"PtiSUicntions of the Geological Survey, 1971-1981" may he purchjsttd by nuil and o\er the counter in paperback book form (two 

volumes, publications listing and index; and as a set of microfiche.

Supplements for 1982. I9P3. W&l. 198$. 1986. and for subseuueiiL \fars »n)ce !h^ la&t permanent catalog may he purchased by mail 

tmd ».\{ Htc counter ir paperback bunk form.

hhit-; catalogs '\isi 01 L" S OeM'^icai ^ur\f"\ Gvologic and 

Wa^ei Supply Reports and Maps For iState!." may be purchased by 

mail and o\er the counter m paperback bt^oklet form only.

"Prire and Availability Lisi of U.S. Geological Survey Publications." issued annuall'.. i> available )ree of charge m papciback hooklet turn 'inly

Selected copies of a monthly catalog "New Publications of the 

I. .,\. Geulugtcal Sunev' are available tree of charge by mail or may 

br obtahieJ over the counter in paperback booklet fonu only. Tho%e 

^ish.na v' iree .subscription M the monthly catalog 'New Publications 

yt fhv TS. Geological Survey" should write to the U.S. Geological 

Suney. **S2 National Center. Rcston, VA 22092.

\ote. Prices of Government publications listed in older catalogs, 

dfinwuncfmenis. and publications may be incorrect. Therefore, the prices 

..barged may differ from the ptices in catalogs, announcements, and