Simulation of Ground-Water Flow and Land Subsidence,

Antelope Valley Ground-Water Basin, California

Prepared in cooperation with the Antelope Valley Water Group

Water-Resources Investigations Report 03-4016

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY
Simulation of Ground-Water Flow and Land 

Subsidence in the Antelope Valley GroundWater Basin, California

By David A. Leighton and Steven P. Phillips

Prepared in cooperation with the

ANTELOPE VALLEY WATER GROUP

Sacramento, California

2003

Water-Resources Investigations Report 03-4016

U.S. GEOLOGICAL SURVEY 7212-53
For additional information write to:

District Chief

U.S. Geological Survey

Placer Hall—Suite 2012

6000 J Street

Sacramento, California 95819-6129

http://ca.water.usgs.gov

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does 

not imply endorsement by the U.S. Government.

Copies of this report can be purchased from:

U.S. Geological Survey

Information Services

Building 810

Box 25286, Federal Center

Denver, CO 80225-0286

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director
Contents iii

CONTENTS

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

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

Purpose and Scope ...................................................................................................................................... 3

Description of Study Area........................................................................................................................... 3

Acknowledgments....................................................................................................................................... 6

Geohydrology....................................................................................................................................................... 6

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

Aquifer System and Boundaries.................................................................................................................. 7

Pre-Development Conditions ...................................................................................................................... 8

Recharge............................................................................................................................................. 9

Discharge ........................................................................................................................................... 11

Post-Development Conditions .................................................................................................................... 11

Recharge............................................................................................................................................. 11

Discharge ........................................................................................................................................... 13

Ground-Water Levels and Movement......................................................................................................... 17

Land Subsidence And Aquifer-system Compaction ............................................................................................ 22

Simulation Of Ground-Water Flow...................................................................................................................... 25

Model Discretization and Boundaries......................................................................................................... 25

Model Parameters........................................................................................................................................ 27

Hydraulic Conductivity and Transmissivity ...................................................................................... 27

Vertical Leakance .............................................................................................................................. 28

Storage Coefficient ............................................................................................................................ 29

Preconsolidation Head ....................................................................................................................... 31

Horizontal-Flow Barriers ................................................................................................................... 32

Model Stresses ............................................................................................................................................ 32

Natural Recharge................................................................................................................................ 32

Artificial Recharge............................................................................................................................. 34

Irrigation-Return Flow .............................................................................................................. 34

Treated Wastewater .................................................................................................................. 36

Natural Discharge .............................................................................................................................. 36

Pumpage............................................................................................................................................. 36

Model Calibration ....................................................................................................................................... 40

Steady-State Simulation..................................................................................................................... 40

Transient-State Simulation................................................................................................................. 44

Model Results.............................................................................................................................................. 52

Water Levels ...................................................................................................................................... 52

Land Subsidence ................................................................................................................................ 64

Water Budget ..................................................................................................................................... 67

Model Sensitivity Analysis ......................................................................................................................... 72

Limitations of the Model............................................................................................................................. 74

Simulation of Aquifer-System Response to Pumping Scenarios................................................................ 82

Summary .............................................................................................................................................................. 88

References Cited .................................................................................................................................................. 89

Appendix: Water use 1992–95............................................................................................................................. 93
iv Contents

Ground Water.............................................................................................................................................. 94

Surface Water.............................................................................................................................................. 95

Local Surface Water........................................................................................................................... 95

Imported Water .................................................................................................................................. 95

Reclaimed Wastewater................................................................................................................................ 95
Figures v

FIGURES

Figure 1. Map showing location of study area, Antelope Valley, California.................................................... 4

Figure 2. Map showing location of faults, ground-water subbasins, line of geologic section, and 

approximate areal extent of lacustrine deposits in the Antelope Valley ground-water 

subbasin, California ........................................................................................................................... 5

Figure 3. Generalized geologic section showing relation of lacustrine deposits to aquifers in the Lancaster 

and the North Muroc subbasins in the Antelope Valley ground-water basin, California.................. 9

Figure 4. Map showing ground-water levels in 1915 and location of areas of potential natural recharge, 

natural discharge as ground-water underflow, and alkali soils in the Antelope Valley ground-water 

basin, California................................................................................................................................. 10

Figure 5. Graph showing estimated ground-water pumpage in Antelope Valley, California, 1915–95........... 14

Figure 6. Map showing distribution of pumpage in Antelope Valley, California............................................. 18

Figure 7. Map showing ground-water levels in spring 1996 and location of area of natural discharge as 

ground-water underflow in the Antelope Valley ground-water basin, California ............................. 21

Figure 8. Map showing measured subsidence in the Antelope Valley ground-water basin, California, 

1930–92.............................................................................................................................................. 23

Figure 9. Graph showing paired water-level and land-subsidence data for sites near and east of Lancaster,

Antelope Valley, California...............................................................................................................24

Figure 10. Map showing model grid and boundaries of model layers in the ground-water flow model of the

Antelope Valley ground-water basin, California ............................................................................... 26

Figure 11. Map showing location of barriers to horizontal ground-water flow simulated in the 

ground-water flow model of the Antelope Valley ground-water basin, California........................... 33

Figure 12. Map showing location of model cells used to simulate natural recharge, recharge of imported 

water used for irrigation, and recharge of treated wastewater in the ground-water flow model 

of the Antelope Valley ground-water basin, California..................................................................... 35

Figure 13. Map showing location of model cells used to simulate natural ground-water discharge in the 

ground-water flow model of the Antelope Valley ground-water basin, California........................... 37

Figure 14. Graph showing time-varying specified hydraulic head used for the north boundary of the 

ground-water flow model of the Antelope Valley ground-water basin, California........................... 38

Figure 15. Map showing location of wells and bench marks used to calibrate the transient-state model 

of the Antelope Valley ground-water basin, California..................................................................... 39

Figure 16. Map showing location of wells used to calibrate the steady-state simulation and measured and 

simulated steady-state water levels from the ground-water flow model of the Antelope Valley 

ground-water basin, California .......................................................................................................... 41

Figure 17. Map showing areal distribution of natural recharge specified in the ground-water flow model 

of the Antelope Valley ground-water basin, California..................................................................... 43

Figure 18. Map showing areal distribution of hydraulic conductivity for layer 1 and transmissivity for 

layer 2 and layer 3 in the ground-water flow model of the Antelope Valley ground-water basin,

California ........................................................................................................................................... 45

Figure 19. Map showing areal distribution of vertical leakance between layers 1 and 2 and layers 2 and 3 

in the ground-water flow model of the Antelope Valley ground-water basin, California................. 49

Figure 20. Map showing areal distribution of specific yield in layer 1 of the ground-water flow model 

in the Antelope Valley ground-water basin, California ..................................................................... 52
vi Figures

Figure 21. Map showing areal distribution of the storage coefficient representing the compressibility of 

water for layer 1 and layer 2 in the ground-water flow model of the Antelope Valley 

ground-water basin, California .......................................................................................................... 54

Figure 22. Map showing areal distribution of the elastic skeletal storage coefficient for layer 1 and layer 2

in the ground-water flow model of the Antelope Valley ground-water basin, California................. 55

Figure 23. Map showing areal distribution of the inelastic skeletal storage coefficient for layer 1 and layer 2

in the ground-water flow model of the Antelope Valley ground-water basin, California................. 57

Figure 24. Map showing difference between steady-state water levels and preconsolidation head in the 

ground-water flow model of the Antelope Valley ground-water basin, California........................... 59

Figure 25. Graphs showing measured and simulated water levels at selected wells in the Antelope Valley 

ground-water basin, California, 1915–95 .......................................................................................... 60

Figure 26. Map showing measured (1996) and simulated (1995) water levels from the ground-water flow 

model of the Antelope Valley ground-water basin, California.......................................................... 65

Figure 27. Graphs showing measured and simulated total land subsidence at selected bench marks in the 

Antelope Valley ground-water basin, California, 1915–95 ............................................................... 66

Figure 28. Graphs showing simulated annual volumes of recharge, discharge, and recharge in relation to 

discharge in the Antelope Valley ground-water basin, California, 1915–95..................................... 71

Figure 29. Graph showing cumulative change in simulated ground-water storage in the Antelope Valley 

ground-water basin, California, 1915–95 .......................................................................................... 72

Figure 30. Diagram showing components of the simulated water budget for selected periods from the 

ground-water flow model of the Antelope Valley ground-water basin, California........................... 73

Figure 31. Graphs showing simulated water levels for two pumping scenarios for the Antelope Valley 

ground-water basin, California, 1995–2025 ...................................................................................... 86

Figure 32. Graphs showing simulated land subsidence near indicated bench marks for two pumping 

scenarios for the Antelope Valley ground-water basin, California, 1995–2025................................ 89

Figure A1. Graph showing sources of water supply in the Antelope Valley ground-water basin, 

California, 1947–95 ........................................................................................................................... 96

Figure A3. Graph showing wastewater use in Antelope Valley ground-water basin, California, 1975–95 ........ 99
Tables vii

TABLES

Table 1. Annual treated wastewater discharged to ponds and spreading grounds, and potential annual 

infiltration of the treated wastewater in the Antelope Valley ground-water basin 1975–95 ............. 12

Table 2. Unit consumptive use of crops grown in Antelope Valley, California, 1952–95.............................. 14

Table 3. Crop area acreage, annual crop consumptive use, and total applied water used for irrigation in 

the Los Angeles County part of Antelope Valley, California, 1952–95............................................ 16

Table 4. Specific storage values used in calculating storage coefficients for layers 1 and 2 in the 

ground-water flow model of the Antelope Valley ground-water basin, California........................... 31

Table 5. Hydraulic characteristics of the horizontal-flow barriers simulated in the ground-water flow 

model of the Antelope Valley ground-water basin, California.......................................................... 34

Table 6. Measured and simulated (layer 1) water levels for wells used to calibrate the steady-state 

simulation of the ground-water flow model of the Antelope Valley ground-water basin, 

California ........................................................................................................................................... 42

Table 7. Measured and simulated water levels at two sites with nested piezometers completed at multiple 

depths in the Lancaster subbasin of the Antelope Valley ground-water basin, California................ 63

Table 8. Simulated recharge, discharge, and change in storage for the Antelope Valley ground-water basin, 

California, 1915–95 ........................................................................................................................... 68

Table 9. Change in simulated water levels at the end of the transient period (1995) resulting from the 

sensitivity analysis of the ground-water flow model of the Antelope Valley ground-water basin, 

California ........................................................................................................................................... 75

Table 10. Change in simulated land subsidence at the end of the transient period (1995) resulting from 

changes in selected model input parameters and stresses during the sensitivity analysis of the 

ground-water flow model of the Antelope Valley ground-water basin, California........................... 80

Table A1. Water-use information for public water suppliers in Antelope Valley, California, by water-supply 

sources, 1992–955.............................................................................................................................. 100

Table A2. Water-use information for self-supplied water users in Antelope Valley, California, by 

water-supply sources, 1992–95.......................................................................................................... 104

Table A3. Deliveries of imported water to Antelope Valley from the California Aqueduct, 1992–95.............. 107

Table A4. Use of reclaimed wastewater in Antelope Valley, California, 1992–95............................................ 107
viii Conversion Factors, Vertical Datum, and Abbreviationa

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS

CONVERSION FACTORS

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

°C = (°F – 32) / 1.8.

Vertical Datum

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD 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.

Abbreviations

AVEK Antelope Valley/East Kern Water Agency

AVWG Antelope Valley Water Group

BCF Block-Centered Flow Package

CDPW California Department of Public Works

CDWR California Department of Water Resources

CIMIS California Irrigation Management Information System

HFB Horizontal Flow Barrier Package

IBS1 Interbed Storage 1 Package

INSAR interferometric synthetic apecture radar

MODFLOW modular three-dimensional finite-difference ground-water flow model

SWP state water project

SWRCB State Water Resources Control Board (California)

Multiply By To obtain

acre 0.4047 hectare

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

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

foot (ft) 0.3048 meter

foot per day (ft/d) 0.3048 meter per day

foot per year (ft/yr) 0.3048 meter per year

square foot per day (ft2/d) 0.09290 square meter per day 

gallon per minute per foot [(gal/min)/ft)] 0.2070 liter per second per meter

inch (in.) 2.54 centimeter

inch per year (in./yr) 25.4 millimeter per year

mile (mi) 1.609 kilometer

square mile (mi2) 259.0 hectare
Conversion Factors, Vertical Datum, and Abbreviations ix

UCCE University of California Cooperative Extension

USGS U.S. Geological Survey

d–1 per day

ft–1 per foot
x Conversion Factors and Vertical Datum

WELL-NUMBERING SYSTEM

Wells are identified and numbered according to their location in the rectangular system for the subdivision of public 

lands. Identification consists of the township number, north or south; the range number, east or west; and the section number. 

Each section is divided into sixteen 40-acre tracts lettered consecutively (except I and O), beginning with “A” in the northeast 

corner of the section and progressing in a sinusoidal manner to “R” in the southeast corner. Within the 40-acre tract, wells are 

sequentially numbered in the order they are inventoried. The final letter refers to the base line and meridian. In California, 

there are three base lines and meridians; Humboldt (H), Mount Diablo (M), and San Bernardino (S). All wells in the study area 

are referenced to the San Bernardino base line and meridian (S). Well numbers consist of 15 characters and follow the format 

007N012W27F005S. In this report, well numbers are abbreviated and written 7N/12W-27F5. Wells in the same township and 

range are referred to only by their section designation, 27F5. The following diagram shows how the number for well

7N/12W-27F5 is derived.

7N/12W-27F5

D C B A

E F G H

M L K J

N P Q R

6 5 4 3 2 1

7 8 9 10 11 12

18 17 16 15 14 13

19 20 21 22 23 24

30 29 28 26 25

31 32 33 34 35 36

27

R11W R10W

T8N

T9N

T10N

R12W

RANGE

TOWNSHIP

R14W R13W

T7N

T6N

Approximately

6 miles

Approximately

1 mile

Approximately

1/4 mile

R12W

Well-numbering diagram (Note: maps in this report use abbreviated well numbers such as "27F5")

SECTION 27

T7N
Abstract 1

Simulation of Ground-Water Flow and Land Subsidence 

in the Antelope Valley Ground-Water Basin, California

By David A. Leighton and Steven P. Phillips

ABSTRACT

Antelope Valley, California, is a 

topographically closed basin in the western part of 

the Mojave Desert, about 50 miles northeast of 

Los Angeles. The Antelope Valley ground-water 

basin is about 940 square miles and is separated 

from the northern part of Antelope Valley by faults 

and low-lying hills. Prior to 1972, ground water 

provided more than 90 percent of the total water 

supply in the valley; since 1972, it has provided 

between 50 and 90 percent. Most ground-water 

pumping in the valley occurs in the Antelope 

Valley ground-water basin, which includes the 

rapidly growing cities of Lancaster and Palmdale. 

Ground-water-level declines of more than 200 feet 

in some parts of the ground-water basin have 

resulted in an increase in pumping lifts, reduced 

well efficiency, and land subsidence of more than 

6 feet in some areas. Future urban growth and 

limits on the supply of imported water may 

continue to increase reliance on ground water. To 

better understand the ground-water flow system 

and to develop a tool to aid in effectively 

managing the water resources, a numerical model 

of ground-water flow and land subsidence in the 

Antelope Valley ground-water basin was 

developed using old and new geohydrologic 

information.

The ground-water flow system consists of 

three aquifers: the upper, middle, and lower 

aquifers. The aquifers, which were identified on 

the basis of the hydrologic properties, age, and 

depth of the unconsolidated deposits, consist of 

gravel, sand, silt, and clay alluvial deposits and 

clay and silty clay lacustrine deposits. Prior to 

ground-water development in the valley, recharge 

was primarily the infiltration of runoff from the 

surrounding mountains. Ground water flowed 

from the recharge areas to discharge areas around 

the playas where it discharged either from the 

aquifer system as evapotranspiration or from 

springs. Partial barriers to horizontal ground-water 

flow, such as faults, have been identified in the 

ground-water basin. Water-level declines owing to 

ground-water development have eliminated the 

natural sources of discharge, and pumping for 

agricultural and urban uses have become the 

primary source of discharge from the groundwater system. Infiltration of return flows from 

agricultural irrigation has become an important 

source of recharge to the aquifer system.

The ground-water flow model of the basin 

was discretized horizontally into a grid of 43 rows 

and 60 columns of square cells 1 mile on a side, 

and vertically into three layers representing the 

upper, middle, and lower aquifers. Faults that were 

thought to act as horizontal-flow barriers were 

simulated in the model. The model was calibrated 

to simulate steady-state conditions, represented by 

1915 water levels and transient-state conditions 

during 1915–95 using water-level and subsidence 

data. Initial estimates of the aquifer-system 

properties and stresses were obtained from a 

previously published numerical model of the 

Antelope Valley ground-water basin; estimates 

also were obtained from recently collected 

hydrologic data and from results of simulations of 

ground-water flow and land subsidence models of 

the Edwards Air Force Base area. Some of these 

initial estimates were modified during model 

calibration. Ground-water pumpage for agriculture 
2 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

was estimated on the basis of irrigated crop 

acreage and crop consumptive-use data. Pumpage 

for public supply, which is metered, was compiled 

and entered into a database used for this study. 

Estimated annual pumpage peaked at 

395,000 acre-feet (acre-ft) in 1952 and then 

declined because of declining agricultural 

production. Recharge from irrigation-return flows 

was estimated to be 30 percent of agricultural 

pumpage; the irrigation-return flows were 

simulated as recharge to the regional water table 

10 years following application at land surface. The 

annual quantity of natural recharge initially was 

based on estimates from previous studies. During 

model calibration, natural recharge was reduced 

from the initial estimate of 40,700 acre-ft per year 

(acre-ft/yr) to 30,300 acre-ft/yr.

Results of the model simulations indicate 

that ground-water storage declined more than 8.5 

million acre-ft from 1915 to 1995. During the 

period of peak pumping (1949–53), pumpage 

averaged 363,000 acre-ft/yr, and 79 percent of the 

ground water withdrawn came from storage 

primarily from layer 1 (the upper aquifer). Water 

released from compaction of the aquitards 

accounted for about 21,600 acre-ft/yr of the 

ground water removed from storage. Downward 

leakage from layer 1 into layer 2 (the middle 

aquifer) accounted for most (86 percent) of the 

pumpage from layer 2. For the simulation period 

1991–95 (a period representing current conditions 

when pumpage for public supply exceeded 

agricultural pumpage), pumpage averaged 81,700 

acre-ft/yr, and most of the ground water 

withdrawn from layer 2 came from downward 

leakage from layer 1. During this period, ground 

water removed from storage accounted for 

17 percent of the total pumpage and recharge from 

irrigation return accounted for about 39 percent of 

the total pumpage. Ground water removed from 

storage as a result of compaction of aquitards was 

reduced to about 3,800 acre-ft/yr. 

The calibrated model was used to simulate 

the response of the aquifer to future pumping 

scenarios. Results of the simulation of scenario 1, 

for which total annual pumpage for 1996–2025 

remained at the level specified for 1995, showed 

that water levels continued to rise (as much as 36 

feet) in agricultural areas, continuing the longterm recovery from drawdown caused by historical 

agricultural pumpage. In the areas where pumping 

for public supply is concentrated, water levels 

continued to decline and subsidence continued in 

the central part of the ground-water basin. Waterlevel declines were largest (more than 100 feet) in 

the south-central part of the ground-water basin; 

most of the public-supply pumpage occurs in this 

area. As much as 1.9 feet of additional subsidence 

was simulated in the central part of the groundwater basin from 1996 to 2025. For scenario 2, 

public-supply pumpage was increased by 

3.3 percent annually, and annual agricultural 

pumpage was increased by 75 percent more than 

that specified for 1995. Pumpage increases for 

scenario 2 resulted in significant water-level 

declines in the southern and northeastern part of 

the Lancaster subbasin; most pumping for public 

supply occurs in these areas. Results of this 

simulation showed that water levels declined more 

than 150 feet in the south-central part of the 

ground-water basin and that an additional 5 feet of 

subsidence was simulated in the central part of the 

basin.

INTRODUCTION

Ground water is an important component of the 

water supply in Antelope Valley. Prior to 1972, ground 

water provided more than 90 percent of the total water 

supply in the valley. From the mid 1960s through the 

mid 1980s, ground-water pumpage declined owing to 

declines in agricultural production and, beginning in 

1972, availability of imported water from the State 

Water Project (SWP). This steady decline in groundwater pumpage ceased in the mid 1980s due to 

increased urban growth and the associated demand for 

ground water. Since 1972, between 50 and 90 percent 

of the total water demand in the valley has been met 

using ground water (Templin and others, 1995). 

Ground-water-level declines have increased pumping 

lifts, reduced well efficiency, and caused aquifersystem compaction and more than 6 ft of land 
Introduction 3

subsidence in some areas (Ikehara and Phillips, 1994). 

Projected urban growth and limits on the available 

imported water may continue to increase the reliance 

on ground water and exacerbate aquifer-system 

compaction and land subsidence (Galloway and others, 

1998).

Projections of water supply and demand indicate 

that the current supply may fall short of demand early 

in the 21st century (Kennedy/Jenks, 1995). 

Conjunctive use of surface and ground water, along 

with methods that can enhance or better use the 

ground-water resource, will likely become an 

important part of water-resource management in 

Antelope Valley. A thorough understanding of the 

ground-water system is needed to effectively manage 

the ground-water resource.

In the 1970s, the U.S. Geological Survey 

(USGS) developed a numerical ground-water flow 

model that was used by water managers to help make 

decisions regarding imported water from the SWP, 

reclaimed wastewater, and captured floodwater 

(Durbin, 1978). Since the development of this model, 

ground-water use in the valley has decreased 

substantially, and areas of ground-water withdrawals 

have changed from primarily agricultural areas to 

primarily urban areas. These changes in the state of the 

ground-water system emphasize the need for a better 

understanding of the system and the effects of watermanagement practices.

Purpose and Scope

In 1992, the USGS began working with the 

Antelope Valley Water Group (AVWG) to provide 

information needed to manage the water resources in 

Antelope Valley. Results from two studies completed as 

part of that work are presented in reports by Templin 

and others (1995) and Ikehara and Phillips (1994). 

Templin and others (1995) describes land use, water 

supply and demand (1919–91), and water demand 

forecasts in the Antelope Valley. Ikehara and Phillips 

(1994) describes land subsidence and its relation to 

ground-water withdrawals. The results of these studies 

and improvements in modeling capabilities, combined 

with data collected since the development of the 

ground-water flow model of Antelope Valley in the 

1970’s (Durbin, 1978), have made it possible to 

develop an updated numerical model of ground-water 

flow in Antelope Valley that includes the simulation of 

aquifer-system compaction and land subsidence. The 

model was developed to assist Antelope Valley water 

managers and planners. 

The purpose of this report is to describe a 

conceptual model of the Antelope Valley ground-water 

basin, to describe the development and calibration of a 

numerical model of ground-water flow, aquifer-system 

compaction, and land subsidence, and to present results 

of simulated future pumping scenarios being 

considered by water managers. Available 

geohydrologic data and data collected during this study 

were used to develop the revised conceptual model of 

the flow system that forms the basis of the revised, 

updated numerical model of the Antelope Valley 

ground-water basin. The numerical model was 

calibrated and simulates ground-water flow, aquifersystem compaction, and land subsidence using waterlevel data for 1915–95 and land subsidence data for 

1926–92. The model was used to provide insight into 

the geohydrology of the Antelope Valley ground-water 

basin, to test the sensitivity of the new model to 

aquifer-system parameters and hydrologic stresses, and 

to compare the potential effects of future pumping 

scenarios. Further, the results of this study can be used 

to guide future data-collection and aid in making 

informed water-management decisions.

Description of Study Area

Antelope Valley, which is located in parts of 

Kern, Los Angeles, and San Bernardino Counties in the 

western part of the Mojave Desert, is about 50 mi 

northeast of Los Angeles (fig. 1). The valley is bounded 

on the south by the southeast-trending San Gabriel 

Mountains and on the northwest by the northeasttrending Tehachapi Mountains. The northern and 

eastern boundaries of the valley are formed by lower 

hills, ridges, and buttes. The valley is a topographically 

closed basin and the valley floor slopes gently toward 

several playas; surface-water runoff terminates in these 

playas. The altitudes of the valley floor, the interior 

hills, and the foothills range from 2,270 to 3,500 ft 

above sea level, and the surrounding mountains rise as 

high as 10,064 ft above sea level.
4 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 1. Location of study area, Antelope Valley, California.

0

0 10

10

20

20 Kilometers

Miles

EXPLANATION

Antelope Valley

drainage basin

Study area—Antelope

Valley ground-water

basin (modified from

Carlson and others,

1998)

Edwards Air Force

Base

Playa surface

Bedrock

14

58

14

133

138

Tehachapi Mts

San Gabriel Mts

Little

Buttes

Antelope

Buttes

Alpine

Buttes

Lovejoy

Buttes

34o30'

35o

00'

118o

00'

118o

30'

SAN BERNARDINO

COUNTY

LOS ANGELES COUNTY

KERN COUNTY

Boron

Palmdale

Rosamond

Mojave

Lancaster

Quartz

Hill

Littlerock

EAFB

Main Base

Wash

Rock

Cottonwood

Buckhorn

Lake (dry)

Rogers

Lake

(dry)

Rosamond

Lake

(dry)

Big

Wash

Amargosa

Rock

Little

Bissell Hills

Hills Rosamond

Fremont

Valley

Creek

Creek

Boundaries—

Edwards Base Air Force

Los Angeles

CALIFORNIA

San

Francisco

San Diego

Mojave

Desert

Antelope

Valley

Pacific

Ocean
Introduction 5 Figure 2. Location of faults, ground-water subbasins, line of geologic section, and approximate areal extent of lacustrine deposits in the Antelope Valley ground-water subbasin, California.

Tehachapi Mts

San Gabriel Mts

EXPLANATION

Antelope Valley drainage basin

Bedrock

Playa surface

Boundaries—

Line of geologic section

Subbasin and name

Lacustrine deposits

(modified from Durbin, 1978)

0

0

10

10

20

20 Kilometers

Miles

(modified from Bloyd, 1967)

A

A'

A A'

Study area—Antelope Valley groundwater basin (modified from Carlson

and others, 1998)

34°30'

35°00'

118°30'

Palmdale

Rosamond

Mojave

Lancaster

QuartzHill

Littlerock

Boron

Bissell Hills

Fremont

Valley

Rogers

Lake

(dry)

Rosamond

Lake

(dry)

Rosamond Hills

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

LANCASTER

CHAFFEE

Wash

Rock

Big

Wash

Amargosa

Rock

Little

118° 00'

PEERLESS

Cottonwood

Little

Buttes

AntelopeButtes

AlpineButtes

Creek

Creek Fault—Dashed where inferred

(modified from Dibblee, 1963;Ward and others, 1993;Nishikawa and others, 2001)

SAN ANDREAS FAULT ZONE

GARLOCK

FAULT

ZONE

WI LLOW SPRINGS FAULT

SPRING

FAULT

RANDSBURG–

FAULT

MUROC

EL MIRAGE FAULT

BLAKE RANCH

FAULT

MOJAVE

FAULT

NEENACH FAULT

FAULT ZONE

ANTELOPE VALLEY

EAFB

Main

Base

LovejoyButtes

Buckhorn Lake

(dry)

Edwards Base Air Force
6 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

The climate in the study area is semiarid to arid. 

Average annual precipitation in the interior of the 

valley is less than 10 in. (Rantz, 1969), humidity is low, 

and temperatures range from below 32οF in the winter 

to more than 100οF in the summer. Most precipitation 

occurs between October and March. Land use in the 

valley is primarily urban, agricultural, industrial, and 

military. Lancaster and Palmdale are the largest cities 

in the valley; in 1988, they had a combined population 

of about 244,000 (California Department of Finance, 

1998).

The Antelope Valley ground-water basin, which 

is the focus of this report, was defined by Carlson and 

others (1998) and is part of the Antelope Valley 

drainage basin (fig. 2). The Antelope Valley drainage 

basin has been divided into 12 ground-water subbasins 

(fig. 2) on the basis of faults, consolidated rocks, 

ground-water divides, and, in some cases, arbitrary 

boundaries (Thayer, 1946; Bloyd, 1967). The Antelope 

Valley ground-water basin covers about 920 mi2, and 

consists of seven of these subbasins; the Buttes, Finger 

Buttes, Lancaster, Neenach, North Muroc, Pearland, 

and West Antelope (fig. 2). The Lancaster subbasin is 

the largest and most developed of the subbasins.The 

Antelope Valley ground-water basin is separated from 

the northern part of Antelope Valley by faults and lowlying hills. Most of the urban and agricultural 

development and associated ground-water pumping in 

Antelope Valley occurs within the study area. 

Acknowledgments

The authors gratefully acknowledge the 

members of the Antelope Valley Water Group for their 

assistance during this study. They provided data, local 

knowledge, and advice that were important to the 

successful completion of the study. We also thank 

Loren Metzger of the USGS for his invaluable 

assistance in compiling the water-use data.

GEOHYDROLOGY

The geohydrology of Antelope Valley is 

described in detail by previous investigators. The 

general geologic structure of Antelope Valley was 

inferred on the basis of a gravity survey by Mabey 

(1960). The surficial geology of the valley was mapped 

and described by Dibblee (1952, 1957, 1958a, 1958b, 

1959a, 1959b, 1959c, 1959d, 1960a, 1960b, 1963, 

1967, 1981) and Noble (1953). Surveys by Johnson 

(1911) and Thompson (1929) provide information on 

ground-water conditions during the early ground-water 

development. Additional studies on the ground-water 

resources in Antelope Valley are documented in reports 

by Thayer (1946), the California Department of Water 

Resources (1947), the California Department of Public 

Works (1955), Snyder (1955), Dutcher and Worts 

(1963), Weir and others (1965), Bloyd (1967), Duell 

(1987), Londquist and others (1993), Rewis (1995), 

Carlson and others (1998), Carlson and Phillips (1998), 

and Nishikawa and others (2001). The geohydrology of 

Antelope Valley is summarized in the following 

sections, but the reader is referred to the 

aforementioned reports for a more detailed description.

Geologic Setting

Underlying Antelope Valley are large sedimentfilled structural depressions that are downfaulted 

between the Garlock and the San Andreas Fault zones. 

The bedrock complex in the valley forms the margins 

and the base of the ground-water basin and crops out in 

the highlands that surround the valley. This bedrock 

complex consists of pre-Cenozoic igneous rocks and 

consolidated Tertiary sedimentary rocks (Hewett, 1954; 

Dibblee, 1963).

In the Antelope Valley ground-water basin, a 

series of unconsolidated deposits of Quaternary age, 

some more than 5,000 ft thick (Benda and others, 1960; 

Mabey, 1960; R.C. Jachens, U.S. Geological Survey, 

written commun., 1991), overlies consolidated rocks 

and forms the basin fill. On the basis of the mode of 

deposition, Dutcher and Worts (1963) mapped these 

deposits as either alluvial or lacustrine. The alluvium 

consists of unconsolidated to moderately indurated, 

poorly sorted gravels, sands, silts, and clays. The older 

deep units within the alluvium typically are more 

compacted and indurated than the younger shallow 

units (Dutcher and Worts, 1963; Durbin, 1978). The 

fine-grained lacustrine deposits consist of sands, silts, 

and clays that accumulated in a large lake or marsh that 

at times covered large parts of the study area (Dibblee, 

1967). These lacustrine deposits consist primarily of 

thick layers of blue-green silty clay, known locally as 

the blue clay member of the lacustrine deposits 
Geohydrology 7

(Dutcher and Worts, 1963), and a brown clay 

containing thin interbedded layers of sand and silt. 

Individual clay beds are as much as 100 ft thick and are 

interbedded with lenses of coarser material as much as 

20 ft thick. The entire sequence of lacustrine deposits is 

as much as 300 ft thick in some areas (Dutcher and 

Worts, 1963). These deposits are overlain by as much 

as 800 ft of alluvium in the southern part of the 

Lancaster subbasin near Palmdale, become 

progressively shallower northward, and are exposed at 

the surface near the southern edge of Rogers Lake. 

Alluvial fans that were formed by the erosion of 

materials from the San Gabriel Mountains encroached 

upon an ancient lake where the lacustrine deposits were 

accumulating, forcing the the ancient lake, and 

associated lacustrine deposits, northward with time 

(Durbin, 1978). The areal extent of the lacustrine 

deposits is not well defined, but its approximate extent 

is shown in figure 2.

Antelope Valley contains numerous faults 

(fig. 2), some of which act as partial barriers to groundwater flow. Most of these faults are described in reports 

by Mabey (1960), Dibblee (1960b, 1963), Dutcher and 

Worts (1963), and Ward and others (1993). More recent 

data and analysis have extended previously described 

faults and identified a previously unknown fault. 

Nishikawa and others (2001) suggest that the Muroc 

and the El Mirage Faults extend across Rogers Lake 

(fig. 2); the extensions of these faults were based on 

water-level data and results from sub-regional groundwater flow simulations. Nishikawa and others (2001) 

also identified a fault that trends from the northwest 

corner of Rosamond Lake southeast along the southern 

edge of Buckhorn Lake to the eastern edge of the study 

area (fig. 2). This fault, which may be an extension of 

the Willow Springs Fault, was inferred on the basis of 

water-level data; water levels are as much as 65 ft 

lower on the northeast side of the fault than on the 

southwest side. Large water-level differences between 

nearby wells in the Buttes subbasin suggest the 

existence of a previously unknown fault; this fault is 

thought to trend southeast of Lovejoy Buttes, parallel 

to the northeastern boundary of the Buttes subbasin 

(fig. 2).

Aquifer System and Boundaries

The lateral boundaries of the Antelope Valley 

ground-water basin are formed, in most cases, by 

shallow or exposed bedrock. North of the Finger Buttes 

and the Neenach subbasins, the boundary of the 

ground-water basin is formed by the Willow Springs 

Fault (fig. 2). This fault is assumed to be an effective 

barrier to ground-water flow to and from subbasins to 

the north (Durbin, 1978). This assumption is supported 

by evidence that springs existed along the fault prior to 

ground-water development and, more recently, by large 

water-level differences over short distances across the 

fault (Carlson and others, 1998).

The historical conceptual model of the aquifer 

system in the Antelope Valley ground-water basin 

utilized a lithostratigraphic approach to divide the 

basin sediments into two major aquifers; an upper 

unconfined aquifer known locally as the “principal” 

aquifer and a “deep” aquifer overlain and confined by 

lacustrine deposits (Dutcher and Worts, 1963; Bloyd, 

1967; Durbin, 1978). The principal aquifer was defined 

as the aluvial deposits that overlie the lacustrine 

deposits in the Antelope Valley ground-water basin 

south and west of Rogers Lake. The principal aquifer 

was assumed to be unconfined throughout its entire 

extent. The deep aquifer was defined as the alluvial 

deposits that underlie the lacustrine deposits 

throughout the Antelope Valley ground-water basin and 

the lacustrine and alluvial deposits in the Antelope 

Valley ground-water basin east and north of Rogers 

Lake. The deep aquifer was assumed confined in areas 

where it is overlain by the lacustrine deposits and 

unconfined to semiconfined in the Rogers Lake area 

where the principal aquifer and lacustrine deposits 

were assumed not to exist.

Paleomagnetic analyses of core samples 

collected during the drilling of monitoring site 

7N/12W-27P5–8, south of Lancaster, indicate a change 

from normal polarity at 344 ft below land surface to 

reversed polarity at 450 ft below land surface (Fram 

and others, 2002). This reversal in polarity is 

interpreted as the transition from the Brunhes to the 

Matuyama polarity-chronostratigraphic units (John 

Hillhouse, U.S. Geological Survey, written commun., 

1998), which occurred about 780,000 years ago (Cande 

and Kent, 1995). The lacustrine deposits were 
8 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

encountered at a depth of about 740 ft below land 

surface at the monitoring site, indicating that these 

deposits are significantly older than 780,000 years. In 

contrast, the lacustrine deposits collected from less 

than 100 ft below land surface at Edwards Air Force 

Base interfinger with alluvial deposits less than 14,000 

years old (Ponti, 1985).Therefore, the historical 

conceptual model groups alluvial deposits that are 

younger than 14,000 years with deposits that are older 

than 780,000 years in the same aquifer. In general, the 

alluvial deposits become more consolidated and 

indurated (hardened) with age, which decreases the 

ability of the aquifer material to transmit and store 

water. Because the hydraulic properties of the alluvial 

deposits change with time, the grouping of deposits of 

significantly different ages into the same aquifer is 

probably not reasonable.

Stratigraphic, hydrologic, and water-quality data 

collected since the early 1990s (Londquist and others, 

1993; Rewis, 1993; Metzger and others, 2002) were 

used in this study to redefine the conceptual mode of 

the Antelope Valley ground-water basin. The new 

conceptual model utilizes a chronostratigraphic 

approach instead of a lithostratigraphic approach to 

divide the ground-water basin into an upper, middle, 

and lower aquifer. Lithologic and geophysical logs of 

wells drilled in Lancaster (Metzger and others, 2002) 

and at Edwards Air Force Base south of Rogers Lake 

(Londquist and others, 1993; Rewis, 1993) indicate 

that the alluvial deposits become less permeable and 

more indurated at approximately 1,950 and 1,550 ft 

above sea level. These changes in properties were 

assumed to represent chronostratigraphic boundaries 

and were used to divide the ground-water basin into the 

three aquifers. The upper aquifer extends from the 

water table to an altitude of about 1,950 ft above sea 

level, the middle aquifer extends from 1,950 to 1,550 ft 

above sea level, and the lower aquifer extends from 

1,550 ft above sea level to the altitude at which bedrock 

is encountered (fig. 3). Geophysical data are limited or 

nonexistent elsewhere in the basin and thus it was 

assumed that these changes in properties of the 

alluvium with depth were laterally extensive 

throughout the basin. The lacustrine deposits were 

assumed to be included in these aquifers.

The upper aquifer varies from unconfined to 

confined depending on the presence and vertical 

position of the thick lacustrine deposits within the 

aquifer. In the south part of the Lancaster subbasin, 

from Palmdale to where Little Rock Wash crosses 

section A-A ́, the lacustrine deposits are below the 

upper aquifer, and the upper aquifer generally is 

unconfined. The upper aquifer may be locally confined 

in this area and in areas outside the extent of the 

lacustrine deposits owing to the presence of 

discontinuous interbedded aquitards. North of Little 

Rock Wash, the lacustrine deposits are present at 

shallower depths and are considered a part of the upper 

aquifer. In the northern part of the study area around 

Rogers Lake, the lacustrine deposits are exposed at 

land surface and form the upper part of the upper 

aquifer. In these areas where the lacustrine deposits are 

a part of the upper aquifer, the upper aquifer is confined 

below the lacustrine deposits. 

In the southern part of the Lancaster subbasin, 

where the lacustrine deposits are deepest, the lacustrine 

deposits are part of the middle aquifer; but in the 

northern part of the subbasin, these deposits overlie the 

middle aquifer. Owing to the overlying lacustrine 

deposits and the discontinuous interbedded aquitards, 

the middle aquifer is assumed confined. If water levels 

were to decline below the confining aquitards, the 

middle aquifer could become unconfined in places.

The alluvium in the lower aquifer becomes 

increasingly consolidated and indurated with depth 

and, in the deepest parts of the basin, probably is able 

to transmit and store only small quantities of water. The 

lacustrine deposits overlie this aquifer except possibly 

in areas around Palmdale and Lancaster where the 

lacustrine may be partly contained within the lower 

aquifer. The lower aquifer is confined by the overlying 

lacustrine deposits and the discontinuous interbedded 

aquitards in the middle aquifer.

Pre-Development Conditions

Prior to ground-water development in Antelope 

Valley, long-term ground-water conditions in the study 

area were in a state of dynamic equilibrium. That is, on 

a time scale of several years or decades, average annual 

natural recharge to the basin was balanced by average 

annual natural discharge, and ground-water levels 

generally fluctuated about long-term mean water levels 

that remained constant over time. Although the 

equilibrium of recharge and discharge was affected by 

dry and wet climatic cycles, the equilibrium was 

maintained over the long term.
Geohydrology 9

Recharge

The primary source of natural recharge to the 

basin is infiltration of precipitation runoff from the 

surrounding mountains (primarily from the San Gabriel 

Mountains south of the valley) in ephemeral stream 

channels. This recharge, defined as mountain-front 

recharge, generally occurs at the heads of the alluvial 

fans and along the stream channels near where the 

streams enter the valley (fig. 4). During periods of high 

runoff, these streams can flow onto the valley floor, 

which may result in some recharge along stream 

channels and washes. Other sources of natural recharge 

include direct infiltration of precipitation and lateral 

ground-water underflow from adjacent bedrock areas 

and basins, both of which probably are small compared 

with mountain-front recharge. Precipitation over the 

valley floor generally is less than 10 in./yr (Rantz, 

1969) and evapotranspiration rates [pan evaporation 

rate is about 114 in./yr (Bloyd, 1967)] and soil 

moisture requirements are high; therefore, recharge 

from direct infiltration of precipitation is negligible 

(Snyder, 1955; Durbin, 1978). Lateral ground-water 

flow from fractures in adjacent bedrock, from the 

Willow Springs subbasin south across the Willow 

Springs Fault, and from other areas adjacent to the 

study area also may recharge the basin, but the quantity 

of recharge from these sources is unknown and 

probably is negligible (Bloyd, 1967).

Figure 3. Generalized geologic section showing relation of lacustrine deposits to aquifers in the Lancaster and the North Muroc subbasins in 

the Antelope Valley ground-water basin, California (modified from Londquist and others, 1993). Line of section is shown on figure 2.

5,000

4,000

3,000

3,000

2,000

2,000

1,000

1,000

Upper aquifer Upper aquifer

Land surface

Lower aquifer

Middle aquifer

FEET

A A'

Sea

level

0

0

10

10

20

20 Kilometers

Miles

Interbedded

aquitards

Lancaster subbasin

Palmdale

Lncaster

Rogers Lake

North Muroc

subbasin

VERTICAL SCALE GREATLY EXAGGERATED

Little RockWash

Bedrock

deposits

Lacustrine
10 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 4. Ground-water levels in 1915 and location of areas of potential natural recharge, natural discharge as ground-water underflow, and alkali soils in the Antelope Valley ground-water basin, California.

0

0

10

10

20

20 Kilometers

Miles

Tehachapi Mts

EXPLANATION

Alkali soils—Queried where unknown (Durbin, 1978)

BedrockPlaya surface

Area of potential natural recharge

Water-level contour—Altitude of water level, in feet,

1915 (modified from Durbin,1978). Contour interval

is variable. Datum is sea level

Fault—Dashed where inferred (modified

Area of discharge as ground-water underflow

from Dibblee, 1963; Ward and others,1993; Nishikawa and others, 2001)

Antelope Valley drainage basin

Boundaries—

Subbasin (modified from Bloyd, 1967)

Study area—Antelope Valley ground-water basin (modified from Carlson and others, 1998)

34o30'

35o00'

118o30'

Rosamond Hills

Fremont

Valley

NORTH MUROC

OAK CREEK

NEENACH

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Rosamond

Lake

(dry)

FINGE

R B

UTTES

LANCASTER

San

Gabriel Mts

PEERLESS

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

Cottonwood

Creek

Wash

Wash

Amargosa

Creek

Rock Little

Rock

Big

2,700

2,600

2,500

2 8, 00

2,700

2,500

2,600

2 600 ,

2,500

2,400

2,600

2,

2,800

700

2,900

3,000

3,100

3,200

3,300

118o00'

2,700

2,900

3,000

3,100

3,200

2,400

2,400

2,320

2,340

2,380

2,380

2,360

2,300

2,280

2,2

2,240

20

2,200

2,260

00 2,5

2,600

2,500

2,400

2,400

2,380

GARLOCK

FAULT

ZONE

WI LLOW SPRINGS FAULT

SPRING

FAULT

RANDSBURGMUROC

FAULT

EL MIRAGE

FAULT

FAULT

BLAKE RANCH

MOJAVE

FAULT

FAULT

NEENACH

FAULT ZONE

ANTELOPE VALLEY

EAFB

Main

Base

LovejoyButtes

Buckhorn

Lake

(dry)

Mojave

Boron

Rosamond

Quartz Hill

Lancaster

Palmdale

Littlerock

Edwards Base Air Force

Rogers Lake

(dry)

Bissell Hills
Geohydrology 11

The quantity of mountain-front recharge in 

Antelope Valley was estimated during previous 

investigations: all estimates were based on rainfall, 

runoff, and channel-geometry data. Londquist and 

others (1993) summarized these estimates and 

concluded that those by Bloyd (1967) and Durbin 

(1978) probably are the most representative of actual 

recharge in the valley because their estimates were 

based on long-term discharge and climatological data. 

Bloyd (1967) estimated that annual mountain-front 

recharge was about 58,000 acre-ft using a surfacewater drainage area of the entire Antelope Valley (558 

mi2). Durbin (1978) estimated that the annual 

mountain-front recharge was about 40,700 acre-ft, 

which is based on the surface-water drainage area of 

the Antelope Valley ground-water basin (385 mi2). 

Bloyd’s (1967) and Durbin’s (1978) estimates resulted 

in similar values for mountain-front recharge—104 and 

106 acre-ft/mi2 of surface-water drainage area, 

respectively. Applying Bloyd’s (1967) estimate of 

recharge per square mile to the surface-water drainage 

area used by Durbin (1978) resulted in an estimated 

annual mountain-front recharge of about 40,040 acre-ft 

for the Antelope Valley ground-water basin, which is 

similar to Durbin’s (1978) estimate of annual 

mountain-front recharge (40,700 acre-ft). Results from 

a study of the infiltration of surface runoff in the 

Mojave River Basin (Izbicki and others, 1995), which 

is immediately east of Antelope Valley, indicate that 

recharge from surface runoff in ephemeral streams is 

limited in this arid environment. Izbicki and others 

(1995) used water-quality analyses, ground-water agedating techniques, and ground-water flow modeling to 

estimate recharge. The results from Izbicki and others 

(1995) suggest that natural recharge in the Antelope 

Valley ground-water basin may be less than that 

estimated by Bloyd (1967) and Durbin (1978). 

Discharge

The primary source of discharge of water from 

the basin prior to ground-water development was from 

evapotranspiration in the lower parts of the valley 

where the water table was within 10 ft of land surface 

(Lee, 1912). The pan evaporation rate in Antelope 

Valley is about 114 in./yr (Bloyd, 1967) and represents 

the upper limit of bare-soil evaporation. A large area of 

alkali soils (fig. 4) (Durbin, 1978) and the existence of 

phreatophytes in the north central part of the groundwater basin, which require saturated soil within the root 

zone, indicate that the water table was near land surface 

at one time and that evapotranspiration was significant 

(Thompson, 1929). Evapotranspiration by mesquite, a 

common phreatophyte in the study area, ranges 

between 0.1 and 1.4 ft/yr, depending on areal density 

(Lines and Bilhorn, 1996). Durbin (1978) estimated 

that prior to ground-water development, discharge from 

the basin owing to evapotranspiration was about 39,400 

acre-ft/yr; he based this estimate on a mass balance. 

Other types of discharge from the basin included lateral 

ground-water underflow and springs. Bloyd (1967) and 

Durbin (1978) stated that ground-water underflow 

occurred through a gap in the bedrock in the northwest 

corner of the North Muroc subbasin into the Fremont 

Valley Basin. Bloyd (1967) estimated that 100 to 500 

acre-ft/yr and Durbin (1978) estimated that about 

1,000 acre-ft/yr flowed through this gap. Discharge by 

springs was thought to be less than 300 acre-ft/yr 

(Johnson, 1911; Thompson, 1929).

Post-Development Conditions

Development of the ground-water resource in 

Antelope Valley has caused significant changes in the 

amount, distribution, and type of recharge and 

discharge. New sources of recharge include irrigation 

return flow and infiltration of treated wastewater, and 

the primary source of discharge, evapotranspiration, 

has been replaced by ground-water pumping.

Recharge

Since the development of irrigated agriculture in 

the Antelope Valley ground-water basin, large amounts 

of irrigation water have been applied to crops; much of 

this water may have percolated below the root zone and 

contributed recharge to the ground-water basin. Snyder 

(1955) reported that agricultural recharge probably 

reached the water table by the early 1950s. Durbin 

(1978), however, assumed that this water had not 

reached the water table in 1961 based on water-quality 

data, which indicated that the dissolved-solids 

concentration in ground water had not changed. He 

reported that the existence of layers of fine-grained 

material above the water table may have prevented or 

delayed the downward migration of this water. Durbin 

(1978) also reported that the concentration of dissolved 

solids started to increase in the 1960s, which indicated 

that irrigation water may have begun to reach the water 
12 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

table. Rising water levels and high nitrate 

concentrations in areas that historically have been used 

for agricultural production since the mid 1970s support 

the assumption that infiltration of irrigation water has 

contributed recharge to the ground-water basin.

Infiltration of treated wastewater may also 

contribute recharge to the ground-water basin. The 

largest producers of treated wastewater in the study 

area are the Palmdale Water Reclamation Plant and the 

Lancaster Water Reclamation Plant (Templin and 

others, 1995). Beginning in 1975, treated wastewater 

has been disposed of in ponds or on spreading grounds 

(areas where water is spread over the land surface to 

evaporate or infiltrate below land surface). A small 

amount of the treated wastewater is reclaimed and used 

primarily for agriculture (Templin and others, 1995). 

The quantity of disposed wastewater available for 

infiltration and potential recharge was estimated by 

subtracting estimated evaporation from the quantity of 

treated wastewater that is disposed of in ponds or on 

spreading grounds (David Lambert, County Sanitation 

District of Los Angeles County, written commun., 

1996). Treated wastewater from the Palmdale Water 

Reclamation Plant is spread on approximately 60 acres 

of land. At the Lancaster Water Reclamation Plant, 

treated wastewater is disposed of in ponds that 

encompass about 430 acres. On the basis of a pan 

evaporation rate of 114 in./yr (9.5 ft/yr) for Antelope 

Valley (Bloyd, 1967), about 570 acre-ft/yr of the 

treated wastewater from the Palmdale Water 

Reclamation Plant and about 4,085 acre-ft/yr of the 

treated wastewater from the Lancaster Reclamation 

Plant is lost to evaporation. The annual quantity of 

treated wastewater discharged to spreading ponds and 

the estimated potential annual infiltration of wastewater 

in the ponds are shown in table 1. Results of studies at 

the Lancaster Water Reclamation Plant indicate that 

infiltration of the ponded water probably does not reach 

the regional water table owing to the high clay content 

of the sediments (David Lambert, County Sanitation 

District of Los Angeles County, written commun., 

1996).

Table 1. Annual treated wastewater discharged to ponds and spreading 

grounds, and potential annual infiltration of the treated wastewater in the 

Antelope Valley ground-water basin, 1975–95

[Discharge data from David Lambert (County Sanitation Districts of Los Angeles 

County, written commun., 1996). acre-ft, acre-feet. —, no data]

Year

Lancaster Water

Reclamation Plant

Palmdale Water

Reclamation Plant

Wastewater

discharge

(acre-ft)

Potential

 infiltration

of wastewater

(acre-ft)

Wastewater 

discharge

(acre-ft)

Potential

infiltration

of wastewater

(acre-ft)

1975 840 0 — —

1976 1,280 0 — —

1977 1,700 0 — —

1978 2,160 0 — —

1979 1,980 0 — —

1980 2,170 0 — —

1981 2,320 0 — —

1982 2,120 0 — —

1983 2,770 0 — —

1984 2,590 0 1,100 530

1985 3,090 0 2,000 1,430

1986 4,210 125 2,580 2,010

1987 5,140 1,055 3,510 2,940

1988 3,660 0 3,730 3,160

1989 2,100 0 3,960 3,390

1990 2,270 0 5,440 4,870

1991 2,410 0 5,110 4,540

1992 3,400 0 6,150 5,580

1993 5,150 1,065 7,080 6,510

1994 4,980 895 7,480 6,910

1995 7,000 2,915 8,070 7,500
Geohydrology 13

Mountain-front recharge is affected by climatic 

conditions, which have not changed significantly 

during the years represented by this study. On the basis 

of the limited data available on mountain-front 

recharge, we assumed that the quantity of mountainfront recharge probably has remained fairly constant 

over time. However, the encroachment of land 

development into areas where mountain-front recharge 

occurs may affect this source of recharge. Lateral 

ground-water flow from adjacent areas is being 

affected by changes in the water-level gradient, but the 

quantity of lateral flow is small and the changes in this 

component of natural recharge have little effect on total 

natural recharge in the basin. 

Discharge

The primary form of discharge from the groundwater basin is ground-water pumpage. The use of 

ground water for irrigation in the Antelope Valley 

began in the 1800s; but, until about 1915, the quantity 

of ground-water pumpage was small. Beginning in 

1915, the number of wells drilled in Antelope Valley 

increased significantly resulting in increases in annual 

pumpage. Historical pumpage was estimated by Snyder 

(1955), Durbin (1978), California Department of Water 

Resources (1980, 1990, and 1991), and Templin and 

others (1995); their estimates are presented in figure 5

along with estimates calculated for this current study. 

The large differences in the estimates of pumpage may 

be due to differences in the methods used to estimate 

pumpage and in the area represented by the estimate. In 

1919, pumpage was estimated to be about 31,000 acreft (California Department of Water Resources, 1980). 

By the early to mid 1950s, pumpage had increased to 

its highest levels; estimates of peak annual pumpage 

ranged from about 260,000 acre-ft/yr (Templin and 

others, 1995) to about 480,000 acre-ft/yr (California 

Department of Water Resource, 1980). The pumpage 

database developed by Templin and others (1995) 

underestimates the pumpage in the ground-water basin, 

because it does not include agricultural pumpage 

estimates for the Kern County part of the study area. 

Increased pumping costs owing to increased pumping 

lifts and rising electricity costs resulted in a decline in 

pumpage beginning in the mid 1950s. In 1972, 

imported water from northern California became 

available further reducing the demand for ground 

water.

Owing to the differences and uncertainties in the 

previous estimates of pumpage and the incomplete 

record for the model period (1915–95), annual 

pumpage was recalculated for this study (fig. 5). The 

revised estimates, which were calculated using the 

previous estimates and the new data collected during 

this study, indicate that pumpage reached a high of 

395,000 acre-ft in 1951 and a modern (post 1915) low 

of 70,600 acre-ft in 1990. Pumpage for the period 

1915–51 was based on the estimates of Snyder (1955). 

Snyder (1955) estimated pumpage for 1924–51 using 

both annual power-consumption data and crop 

consumptive-use data for intermittent years. The 

estimates of pumpage from these data were nearly 

equal (fig. 5), and were assumed valid for this study. 

The pumpage for 1952–95 was calculated for this study 

using irrigated crop acreage data, crop consumptiveuse data, and data from the pumpage database created 

by Templin and others (1995).

 Owing to the known limitations in the 

agricultural component of the pumpage data in the 

pumpage database created by Templin and others 

1995), only the public-supply data from the pumpage 

database presented by Templin and others (1995) were 

used for 1952–95 estimates presented in this study. 

Pumpage for public supply is metered and therefore 

was assumed to be well documented in the pumpage 

database. Data compiled from public-supply agencies 

support this assumption. Pumping of small quantities 

of ground water for domestic use occurs in the study 

area, but, because it was not measured, it was not 

included in estimates of annual pumpage. 
14 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 5. Estimated ground-water pumpage in Antelope Valley, California, 1915–95.

Pumpage database, modified

from Templin

and others (1995)

Durbin (1978)

Power

consumption

data, (Snyder, 1955)

Snyder (1955)

Antelope Valley

United Water Purveyors

(Mark Johnstone, written

commun., 1991)

500

400

300

200

100

0

PUMPAGE, IN THOUSAND ACRE-FEET

1915 1925 1935 1945 1955 1965 1975 1985 1995

YEAR

California Department of

Water Resources (1980,

1990, 1991) Estimate made

for this study

Table 2. Unit consumptive use of crops grown in Antelope Valley, 

California, 1952–95

[Unit consumptive use in acre-feet per acre; CDPW, California Department of 

Public Works; CIMIS, California Irrigation Management Information System; 

UCCE, University of California Cooperative Extension. —, no data]

1 Reference evapotranspiration (ETo) × crop coefficient (Kc) [ETo from 

California Irrigation Management Information System (CIMIS) (2001) and Kc 

from University of California Cooperative Extension (1994)].

Crop

Source

Snyder (1955) CDPW

(1955)

Templin

and others

(1995)

CIMIS/

UCCE 1

(1994)

Alfalfa 3.37 3.6 4.3 4.8

Pasture 3.18 3.4 4.3 4.8

Orchard 2.6 2.8 2.6 —

Sugar beets 2.54 2.6 — —

Field crops 2.1 2.1 2.2 —

Truck crops 1.92 2.0 1.5 —
Geohydrology 15

The agricultural component of annual pumpage 

for 1952–95 was estimated by calculating the total 

annual crop consumptive use from irrigated crop 

acreage data obtained from the Los Angeles County 

Agricultural Commissioner and unit consumptive-use 

data for the crops. Unit consumptive use is defined as 

the quantity of water, in acre-feet, used per acre of crop 

grown. Published estimates of the unit consumptive use 

of crops grown in Antelope Valley (table 2) are from 

the California Department of Public Works (1955), 

Snyder (1955), and Templin and others (1995). The 

estimates reported by Templin and others (1995) were 

from the California Department of Water Resources 

(CDWR). Estimates also were calculated for the unit 

consumptive use of alfalfa and pasture (table 2); these 

estimates were calculated using crop coefficients 

(University of California Cooperative Extension, 1994) 

and the reference evapotranspiration rate for Antelope 

Valley. The reference evapotranspiration rate data are 

from the California Irrigation Management 

Information System (CIMIS), a repository of 

climatological data used for irrigation management and 

operated by the CDWR. 

CIMIS uses local climatological data to 

determine a reference evapotranspiration rate (ETo) for 

unstressed (well-watered) pasture. The unit 

consumptive use (ETc) for a given crop is calculated as 

the product of ETo and the crop coefficient (Kc) that 

relates the evapotranspiration rate of the given crop to a 

reference crop (pasture). The normal year ETo for the 

ground-water basin was estimated by averaging the 

normal year ETo data for Lancaster and Palmdale 

obtained from CIMIS. For this study, ground-water 

pumping for irrigation of alfalfa was assumed to occur 

only from March through October: the total ETo for 

these months in a normal year is 4.8 ft. The University 

of California Cooperative Extension (1994) reports that 

the Kc for alfalfa ranges from 0.4 to 1.2, depending on 

the stage of growth, but that some researchers 

recommend using a Kc value of 1.0 for alfalfa. A Kc

value of 1.0 was used for this study, which resulted in a 

unit consumptive use of 4.8 ft, which was the same as 

that for pasture.

The ETc values for orchard, sugar beets, and 

field crops are consistent among the sources shown in 

table 2. The ETc values estimated by Snyder (1955) for 

these crops were used to calculate the annual 

consumptive use of these crops for 1952–95 so that the 

values were consistent with those used by Snyder 

(1955) to estimate agricultural pumpage for 1915–51. 

Because the estimates of ETc for alfalfa and pasture are 

not consistent among the sources shown in table 2, the 

annual consumptive use for alfalfa and pasture for 

1952–95 was calculated using the ETc values estimated 

from Kc and ETo data. The ETc for alfalfa and pasture 

(4.8 acre-ft/acre) was used to calculate annual 

consumptive use for 1952–95 because these values 

were based on the most current crop consumptive-use 

studies. However, annual consumptive-use estimates 

for alfalfa and pasture were not recalculated for 

1915–51 using the current unit consumptive-use values 

of 4.8 acre-ft/acre because annual crop acreage data 

were not available for this period.

Annual crop acreage data for 1952–95 are shown 

in table 3. Onions were assumed to be a field crop and, 

therefore, the ETc for field crops reported by Snyder 

(1955) (table 2) was used to calculate the total annual 

consumptive use of onions. The total annual crop 

consumptive use in the study area for 1952–95 (table 3) 

was calculated using the following equation:

(1)

+

where

CUT is the total annual crop consumptive use 

[L3],

Aalf is the area of irrigated alfalfa [L2],

CUalf is the unit consumptive use for alfalfa [L],

Apast is the area of irrigated pasture [L2],

CUpast is the unit consumptive use for pasture [L],

Aorch is the area of irrigated orchards [L2],

CUorch is the unit consumptive use for orchards 

[L],

Abeets is the area of irrigated sugar beets [L2], 

CUbeets is the unit consumptive use for beets [L],

Aonions is the area of irrigated onions [L2], and

CUonions is the unit consumptive use for onions [L].

CUT Aalf CUalf = ( × ) +

Apast CUpast ( × ) Aorch CUorch + ( × )

Abeets CUbeets ( × ) Aonions CUonions + ( × )
16 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Table 3. Crop area acreage, annual crop consumptive use, and total applied water used for irrigation in the Los Angeles County part of Antelope Valley, 

California, 1952–95

[Crop area data from Los Angeles County Agricultural Commissioner (1952–95), written commun.]

Year

Crop area, in acres Total annual crop

consumptive use,

in thousand acre-feet

Total applied water,

in thousand

Alfalfa Orchard Pasture Onions Beets acre-feet

1952 36,000 3,408 4,108 0 0 199.8 285.5

1953 36,400 3,530 4,300 0 0 202.8 289.8

1954 33,200 3,616 4,400 0 0 188.2 268.8

1955 34,800 3,830 4,060 0 0 196.0 280.0

1956 35,900 3,740 4,000 70 0 200.8 286.9

1957 34,000 2,645 3,700 140 0 185.8 265.4

1958 31,800 2,644 3,800 415 0 176.1 251.5

1959 32,600 2,716 3,800 640 0 180.7 258.2

1960 32,500 2,772 1,900 670 0 175.7 250.9

1961 32,000 2,396 1,800 50 435 171.0 244.3

1962 32,000 2,432 1,600 50 2,125 174.9 249.9

1963 36,500 2,470 1,400 90 2,150 196.3 280.5

1964 38,000 2,420 1,700 100 2,660 205.4 293.4

1965 38,000 2,384 2,000 160 1,466 203.1 290.1

1966 36,000 2,385 2,000 170 1,470 193.5 276.5

1967 34,000 2,088 2,000 0 1,660 182.6 260.9

1968 32,000 2,097 1,800 80 1,584 172.5 246.5

1969 30,000 1,838 1,500 0 1,520 160.6 229.4

1970 27,700 1,855 1,500 60 1,500 149.7 213.9

1971 25,400 1,867 1,000 0 1,500 137.3 196.1

1972 22,400 1,591 1,000 80 1,500 121.7 173.9

1973 21,400 1,590 400 240 1,220 115.0 164.3

1974 19,800 1,540 400 250 1,070 106.7 152.4

1975 19,000 1,393 400 700 1,200 103.4 147.8

1976 20,000 1,162 375 1,200 1,868 109.8 156.9

1977 23,000 1,162 375 2,500 3,700 131.6 188.0

1978 23,000 1,180 400 1,700 3,200 128.8 184.0

1979 22,800 1,219 0 1,715 2,200 124.5 177.8

1980 22,500 1,349 100 425 3,860 125.4 179.2

1981 20,000 1,015 100 977 2,775 110.2 157.5

1982 16,200 1,046 100 1,433 340 86.9 124.2

1983 13,757 1,104 200 1,810 317 76.5 109.2

1984 12,176 820 0 1,477 260 66.1 94.5

1985 10,671 852 0 1,580 0 58.6 83.8

1986 8,413 704 0 1,481 0 46.9 67.0

1987 8,895 700 0 1,497 0 49.2 70.3

1988 7,620 700 0 1,702 0 43.5 62.2

1989 6,300 800 0 1,675 0 37.6 53.7

1990 6,211 815 0 1,550 0 37.0 52.8

1991 5,768 705 0 1,690 0 34.6 49.5

1992 5,222 728 0 1,665 0 32.1 45.8

1993 5,532 738 0 1,564 0 33.4 47.7

1994 5,565 830 0 1,346 0 33.5 47.9

1995 5,480 842 0 1,669 0 33.9 48.4
Geohydrology 17

The total water applied for agriculture in the Los 

Angeles county section of the ground-water basin 

(table 3) was calculated by dividing total annual crop 

consumptive use by irrigation efficiency. Irrigation 

efficiency was assumed to be 70 percent on the basis of 

previous studies (California Department of Public 

Works, 1955; Snyder, 1955), a comparison of water 

application rates (Orloff and others, 1989), and crop 

consumptive-use rates for alfalfa (University of 

California Cooperative Extension, 1994). The actual 

irrigation efficiency likely is spatially and temporally 

variable and controlled by several factors including 

irrigation practices and soil characteristics; this 

variability was not represented in this study. The 

agricultural component of annual pumpage for 

1952–95 was estimated by subtracting imported water, 

local surface-water diversions, and reclaimed 

wastewater used for agriculture from the total annual 

water applied for agriculture.

Records of annual irrigated crop acreage and 

agricultural pumpage are not available for Kern County 

and, therefore, estimated agricultural pumpage for that 

part of the study area was based on the relation 

between land use and ground-water use for 1961 and 

1987. Land-use maps and agricultural pumpage data 

for Los Angeles County were used to estimate the 

quantity of ground-water pumpage per acre of 

agricultural land in 1961 and 1987. This ratio of 

pumpage per acre of agricultural land was then applied 

to agricultural land-use data for Kern County to 

estimate agricultural pumpage for the Kern County part 

of the study area for those years. In both 1961 and 

1987, agricultural pumpage in the Kern County part of 

the study area was about 18 percent of the annual 

agricultural pumpage in the Los Angeles County part 

of the study area. This relation was assumed constant 

for the period 1952–95.

The spatial distribution of pumpage in the study 

area changed as agriculture declined in the late 1960s 

and 1970s and as urban areas grew in the 1980s. Data 

from the pumpage database were used to show changes 

in the spatial distribution of pumpage in the groundwater basin. Although the agricultural component of 

the pumpage database is known to be incomplete, it 

was assumed that the spatial distribution of pumpage in 

the database is representative of the spatial distribution 

of actual pumpage in the basin. Prior to the 1980s, 

ground water was pumped primarily for agricultural 

use and mainly in the western and eastern parts of the 

Lancaster subbasin (fig. 6A). Since the 1980s, much of 

the pumpage has been for urban use, and the pumping 

centers have shifted from agricultural areas to urban 

areas near Rosamond, Edwards Air Force Base, 

Lancaster, and Palmdale (fig. 6B). 

Natural discharge from evapotranspiration is 

greatly affected by changes in water levels caused by 

ground-water pumping. The water table has declined to 

a depth at which natural discharge from 

evapotranspiration is minimal. As with natural 

recharge, natural discharge as ground-water underflow 

is affected by changes in water-level gradients, but 

ground-water underflow is only a small component of 

the overall water budget for the basin.

Ground-Water Levels and Movement

Prior to ground-water development, the depth to 

water in the Lancaster subbasin was less than or equal 

to 50 ft below land surface in most of the subbasin, 

and, in the areas around the playas, artesian conditions 

existed. In the western part of the Lancaster subbasin 

and in the southern part near Palmdale, the depth to 

water was about 200 ft below land surface. Data on the 

depth to water in the Buttes, Finger Buttes, Neenach, 

Pearland, and West Antelope subbasins are limited, 

especially for the upslope parts of the these subbasins. 

Available data indicate that the depth to water in these 

subbasins ranged from about 50 ft below land surface 

in the lower part of the Neenach subbasin to about 200 

ft below land surface in the higher parts of the Buttes, 

Pearland, and Finger Buttes subbasins. In the North 

Muroc subbasin, depths to water ranged from 50 to 100 

ft below land surface. Water-level altitudes were 

highest in the Finger Buttes (3,300 ft above sea level) 

and Pearland (3,200 ft above sea level) subbasins 

(fig. 4) and lowest around the playas in the northeast 

part of the Lancaster subbasin (2,300 ft above sea level) 

and in the North Muroc subbasin (2,200 ft above sea 

level) (fig. 4). Around the playas, water levels were 

near land surface, and ground water was discharged in 

these areas largely by evapotranspiration and springs. 
18 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 6. Distribution of pumpage in Antelope Valley, California. 

A, 1956; 

B, 1995.

0

0

10

10

20

20 Kilometers

Miles

Tehachapi Mts

San Gabriel Mts

EXPLANATION

Bedrock

Playa surface

Antelope Valley drainage basin

Subbasin (modified from Bloyd,1967)

Edwards Air Force Base

less than 1,5001,500 to 3,0003,000 to 4,500greater than 4,500

Boundaries—

Study area—Antelope Valley ground-water

Pumpage in 1956, in acre-feet

basin (modified from Carlson and others, 1998)

Fault—Dashed where inferred

(modified from Dibblee, 1963;Ward and others, 1993;Nishikawa and others, 2001)

Fremont

Valley

34o30'

35o00'

118o30'

Bissell Hills

Rogers

Lake

(dry) Rosamond

Lake

(dry)

Rosamond Hills

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

LANCASTER

118o00'

PEERLESS

A

Creek

Little

Buttes

AntelopeButtes

AlpineButtes

Rock

Rock

Wash

Amargosa

Creek

Cottonwood

Big

Little

SAN BERNARDINO

COUNTY

LOS ANGELES COUNTY

KERN COUNTY

GARLOCK

FAULT

ZONE

WI LLOW SPRINGS FAULT

SPRING

FAULT

RANDSBURGMUROC

FAULT

MOJAVE

FAULT

FAULT

NEENACH

FAULT ZONE

ANTELOPE VALLEY

EL MIRAGE

FAULT

FAULT

BLAKE RANCH

EAFB

Main

Base

LovejoyButtes

Buckhorn

Lake

(dry)

Mojave

Boron

Rosamond

Quartz Hill

Lancaster

Palmdale

Littlerock

Edwards Base Air Force
Geohydrology 19 Figure 6.—Continued.

SAN BERNARDINO

COUNTY

LOS ANGELES COUNTY

KERN COUNTY

0

0

10

10

20

20 Kilometers

Miles

EXPLANATION

less than 1,5001,500 to 3,0003,000 to 4,500greater than 4,500

Pumpage in 1995, in acre-feet

34o30'

35o00'

118°30'

Rosamond

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

118o00'

LANCASTER

Fremont

Valley

Little

Buttes

AntelopeButtes

AlpineButtes

Amargosa

PEERLESS

Creek

Cottonwood

Wash

Rock

Big

Wash

Rock Little

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

Creek

B

EAFB

Main

Base

LovejoyButtes

Buckhorn

Lake

(dry)

Mojave

Boron

Rosamond

Quartz Hill

Lancaster

Palmdale

Littlerock

Edwards Base

Rogers Lake

(dry)

Bissell Hills Air Force

Fault—Dashed where inferred (modified

from Dibblee, 1963; Ward and others,1993; Nishikawa and others, 2001)

GARLOCK

FAULT

ZONE

WI LLOW SPRINGS FAULT

SPRING

FAULT

RANDSBURGMUROC

FAULT

EL MIRAGE

FAULT

FAULT

BLAKE RANCH

MOJAVE

FAULT

FAULT

NEENACH

FAULT ZONE

ANTELOPE VALLEY
20 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Ground water moves from areas of high waterlevel altitudes to areas of low water-level altitudes; 

therefore, the general direction of ground-water flow 

can be inferred from contours of water level. Ground 

water flowed from areas of recharge along the 

mountain fronts and stream channels toward areas of 

discharge around Rosamond, Buckhorn, and Rogers 

Lakes (dry) (fig. 4). In the Finger Buttes and West 

Antelope subbasins, ground water generally moved 

from northwest to southeast. In the Neenach subbasin, 

ground water generally moved from west to east. In the 

Buttes and Pearland subbasins, ground water generally 

moved from southeast to northwest. In the Lancaster 

subbasin, ground water moved from the upslope areas 

in the southwestern, southern, and southeastern parts of 

the subbasin to the discharge areas in the northern and 

northeastern part of the subbasin. In the North Muroc 

subbasin, there was a small water-level gradient toward 

the north where some ground water flowed into the 

Fremont Valley Basin.

Since the 1920s, ground-water use has exceeded 

estimated natural recharge. This overdraft has caused 

water levels to decline by more than 200 ft in some 

areas and by at least 100 ft in most of the study area. In 

agricultural areas, declining water levels began to level 

off in the late 1970s and, in some areas, water levels 

began to rise. Since 1983, water levels have risen by as 

much as 45 ft in areas where land use is predominately 

agriculture (Carlson and others, 1998). In urban areas, 

water levels have continued to decline. 

Water-level data collected in spring 1996 

(Carlson and others, 1998) represent regional water 

levels after more than 75 years of ground-water 

development in the basin (fig. 7). In the Lancaster 

subbasin, depth to water is more than 100 ft below land 

surface throughout most of the subbasin and the water 

table has declined to a level that has eliminated the 

discharge of ground water by evapotranspiration. In the 

eastern and western parts of the subbasin where most 

of the agricultural pumping has occurred, depth to 

water is more than 200 ft below land surface; in some 

areas, depth to water is more than 300 ft below land 

surface. In the area around Palmdale, where most of the 

pumping for public supply has occurred, depth to water 

is more than 500 ft below land surface. In the Finger 

Buttes, Neenach, and West Antelope subbasins, depth 

to water ranges from about 150 ft to more than 350 ft 

below land surface. In the Buttes and Pearland 

subbasins, depth to water ranges from about 50 ft to 

about 250 ft below land surface, and in the North 

Muroc subbasin, depth to water ranges from about 100 

ft to near 200 ft below land surface. Water-level 

altitudes are highest in the Neenach (2,800 ft above sea 

level) Pearland (2,800 ft above sea level) and Finger 

Buttes subbasins (data from a single data point in the 

Finger Buttes subbasin suggest that the water-level 

altitudes in this subbasin may be about 3,200 ft above 

sea level) (Carlson and others, 1998). The lowest 

water-level altitude is in the Lancaster subbasin in the 

area around Palmdale (2,050 ft above sea level) (fig. 7). 

In the Neenach subbasin, ground water now 

moves to the northeast and flows into the Lancaster 

subbasin. In the Buttes and Pearland subbasins, ground 

water generally continues to move southeast to 

northwest. In the Lancaster subbasin, ground water 

flows from areas of natural recharge toward areas of 

low water-level altitude in the south-central part of this 

subbasin (fig. 7). Although not evident from the 

contours shown on figure 7, there also is an area of low 

water-level altitude centered near the primary 

production wells at Edwards Air Force Base, near the 

south end of Rogers Lake (Carlson and others, 1998); 

ground water flows from the boundary between the 

Lancaster and North Muroc subbasin toward this 

ground-water low (Rewis, 1995). An area of high 

water-level altitude exists in the central part of the 

Lancaster subbasin southwest of Rosamond Lake

(fig. 7); the high water levels may be the result of 

limited agricultural pumping and low-permeability 

alluvial material in this area. Because pumping for 

agriculture has been limited, little drawdown has 

occurred over time. Recharge from the infiltration of 

wastewater from the Lancaster Water Reclamation 

Plant discharged to ponds in the area also may be 

contributing to the high water-level altitudes. In the 

North Muroc subbasin, the water-level gradient is fairly 

flat, but a small amount of water may continue to flow 

toward the Fremont Valley Basin from the North Muroc 

subbasin.
Geohydrology 21 Figure 7. Ground-water levels in spring 1996 and location of area of natural discharge as ground-water underflow in the Antelope Valley ground-water basin, California.

0

0

10

10

20

20 Kilometers

Miles

Tehachapi Mts

EXPLANATION

Bedrock

Playa surface

Line of equal water levels, 1996—Approximately located; dashed where uncertain.

Contour interval variable, in feet. Datumis sea level (modified from Carlson and others, 1998)

Fault—Dashed where inferred (modified

Boundaries—

from Dibblee, 1963; Ward and others,1993; Nishikawa and others, 2001)

Antelope Valley drainage basin

Subbasin (modified from Bloyd, 1967)

Study area—Antelope Valley ground-water

basin (modified from Carlson and others, 1998)

Area of natural discharge as ground-water underflow

34o30'

35o00'

118o30'

Rosamond Hills

118o00'

NORTHMUROC

OAK CREEK

NEENACH

WEST ANTELOPE

BUTTES

PEARLAND

CHAFFEE

Fremont

Valley

2,175

2,175

2,225

2,220

2,225

2,250

2,220

2,220

2,225

2,225

2,300

2,600

2,600

2,500

2,500

2,400

2,400

2,400

2,500

2,300

2,500

2,300

2,500

2,400

2,600

2,700

2,800

2,400

2,250

2,225

2,700

2,800

2,600

2,700

2,800

2,250

2,250

2,050 2,100

2,150

WILLOW

SPRINGS

GLOSTER

Rosamond

Lake

(dry) Buckhorn Lake

(dry)

FINGER BUTTES

LANCASTER

Little

Buttes

AntelopeButtes

AlpineButtes

Cot ot nwood

Creek

Wash

Amargosa Creek

Rock Little

Wash

Rock Big

PEERLESS

2,175

2,400

San Gabriel Mts

Rogers Lake

(dry)

EAFB

Main

Base

LovejoyButtes

Mojave

Boron

Rosamond

Quartz Hill

Lancaster

Palmdale

Littlerock

Edwards Base

Bissell Hills Air Force
22 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

LAND SUBSIDENCE AND AQUIFERSYSTEM COMPACTION

Land subsidence is the gradual settling or sudden 

sinking of the Earth’s surface owing to subsurface 

movement of earth materials. One of the principal 

causes of land subsidence is the gradual compaction of 

susceptible aquifer systems that can accompany 

ground-water level declines caused by ground-water 

pumping (Galloway and others, 1999). Results of 

Global Positioning System and spirit leveling surveys 

indicate that as much as 6.6 ft of subsidence occurred 

in the valley between 1930 and 1992 (fig. 8) (Ikehara 

and Phillips, 1994). The spatial variability in the 

amount of land subsidence in Antelope Valley is 

affected by the magnitude of water-level declines and 

the distribution of compressible sediments. The large 

amount of subsidence measured around bench marks 

BM 474 and BM 1171A and between Little Buttes and 

Rosamond (fig. 8) is the result of water-level declines 

coupled with a significant thickness of compressible 

sediments in the aquifer system. No measurable land 

subsidence was detected near Palmdale, although it is 

an area of large water-level declines (Carlson and 

others, 1998). The lack of subsidence in this area 

indicates that compressible sediments may not exist or 

water levels may not have declined to the level at which 

inelastic (permanent) compaction of the sediments 

would occur. The results of a more recent study, which 

used satellite-based interferometric synthetic aperture 

radar (InSAR) to measure land subsidence during the 

period October 20, 1993, to December 22, 1995, 

indicated that locally, more than 0.16 ft of subsidence 

occurred and likely is still occurring in the valley 

(Galloway and others, 1998). Detrimental effects of 

land subsidence include the loss of aquifer storage, 

increased flooding, cracks and fissures at land surface, 

damage to man-made structures, and intangible 

economic costs.

Compaction of the aquifer system occurs when 

the hydraulic head or fluid pressure in compressible, 

fine-grained sediments declines, releasing porewater in 

the compressible sediments from storage (Fluid 

pressure has units of stress and is equal to hydraulic 

head times the specific weight of water). For a constant 

total stress on the aquifer system the associated 

decrease in fluid pressure is accompanied by an 

equivalent increase in the effective or intergranular 

stress on the granular matrix or skeleton of the aquifer 

system, resulting in aquifer-system compaction. The 

magnitude of the compaction is governed by the 

compressibility of the sediments which varies by an 

order of magnitude or more depending on whether the 

intergranular stress changes are in the elastic or 

inelastic range of stress for the compacting sediments. 

Elastic compaction is compaction that occurs when the 

skeletal structure of the sediments is not permanently 

rearranged: it can be reversed by an associated rise in 

hydraulic head. Inelastic compaction is compaction 

that occurs when there is a permanent rearrangement of 

the skeletal structure of the sedimentary matrix; it 

cannot be reversed by a rise in hydraulic head, and, 

therefore, results in a permanent lowering of land 

surface and a loss of ground-water storage capacity. 

The point to which hydraulic heads must decline to 

cause inelastic compaction in the compressible 

sediments is termed the preconsolidation head. When 

hydraulic head in the compressible sediments declines 

below the existing preconsolidation head, permanent 

compaction can occur and a new lower 

preconsolidation head is established. When heads 

fluctuate above the preconsolidation head, generally 

small magnitude elastic (reversible) compaction 

occurs. Detailed discussions of the mechanics of 

compaction and its relation to land subsidence are 

given in reports by Leake and Prudic (1991), Ikehara 

and Phillips (1994), Galloway and others (1998), and 

Galloway and others (1999). 
Land Subsidence And Aquifer-system Compaction 23 Figure 8. Measured subsidence in the Antelope Valley ground-water basin, California, 1930–92.

0

0

10

10

20

20 Kilometers

Miles

Tehachapi Mts

EXPLANATION

Playa surface

Well and number

Bench mark and number

Bedrock

Line of equal measured subsidence—Dashed

where approximately located. Interval 1 foot(modified from Ikehara and Phillips, 1994)

Antelope Valley drainage basin

Subbasin (modified from Bloyd,1967)

Boundaries—

Study area—Antelope Valley ground-water

basin (modified from Carlson and others,1998)

34o30'

35o00'

118o30'

Rosamond Hills

Rock

Big

Wash

Amargosa

118o00'

NORTH MUROC

OAK CREEK

NEENACH

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Rosamond

Lake

(dry) Buckhorn Lake

(dry)

FINGER BUTTES

1

1

3

3

3

3

4

4

4

6

5 5

5

6

2

2 2

2

Fremont

Valley

Little

Buttes

AntelopeButtes

AlpineButtes

2

Rogers Lake

(dry)

LANCASTER

Wash

7N/10W-5E1

Rock Little

Creek

7N/12W-15F1

BM 474 BM 1171A

7N/12W-15F1

BM 474

PEERLESS

Creek

Cottonwood

San Gabriel Mts

EAFB

Main

Base

LovejoyButtes

Mojave

Boron

Rosamond

Quartz Hill

Lancaster

Palmdale

Littlerock

Edwards Base

Bissell Hills Air Force

Fault—Dashed where inferred (modified

from Dibblee, 1963; Ward and others,1993; Nishikawa and others, 2001)
24 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

As noted earlier, the ground-water system in 

Antelope Valley is made up of alluvial and lacustrine 

sedimentary deposits. The alluvial deposits consist of 

sand and gravel interbedded with thin, fine-grained silt 

and clay layers. The lacustrine deposits consist of thick 

clay layers interbedded with thin coarse-grained 

material. Compaction can occur in both the thin and the 

thick fine-grained silt and clay layers that form 

confining beds, or aquitards; little compaction, 

however, can occur in the sand and gravel deposits. As 

described by Freeze and Cherry (1979), “... the term 

aquitard has been coined to describe the less-permeable 

beds in a stratigraphic sequence. These beds may be 

permeable enough to transmit water in quantities that 

are significant in the study of regional ground-water 

flow, but their permeability is not sufficient to allow the 

completion of production wells within them.” The 

thickness of the aquitards affects the rate and the 

duration of aquifer-system compaction. The thickness 

of the aquitard affects the rate at which the fluid 

pressure of the aquitard equilibrates with the fluid 

pressure of the surrounding coarse-grained material; 

thin aquitards equilibrate faster than thick aquitards. 

Hydraulic heads in aquifer material surrounding the 

thick aquitards may recover to levels higher than 

preconsolidation head, but compaction can continue to 

occur until the hydraulic heads in the thick aquitards 

equilibrate with hydraulic heads in the surrounding 

coarse-grained deposits. This equilibration can take 

years to complete and is termed residual compaction. 

The fluid-pressure equilibration between thick or thin 

aquitards and the surrounding aquifer results in release 

from or uptake to storage in the aquitards and involves 

fluid-flow between the aquitards and aquifer. This flow 

is primarily vertical as the lateral extent of aquitards is 

generally much greater than their thickness.

The relation between hydraulic head, which is 

measured as water levels in wells, and compaction, 

which is typically measured as land subsidence at land 

surface, can be seen in figure 9. The measured land 

subsidence at BM 474 near Lancaster is directly related 

to the continuous water-level decline measured in 

Figure 9. Paired water-level and land-subsidence data for sites near and east of Lancaster, Antelope Valley, 

California (modified from Ikehara and Phillips, 1994). Location of bench marks and wells are shown on figure 8.

1930 1940 1950 1960 1970 1980 1990

0

4

8

12

WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

SUBSIDENCE, IN FEET

no data

Sites near Lancaster

Sites east of Lancaster

0

4

8

12

YEAR

Water level

7N/12W-15F1

Subsidence

BM 474

Subsidence

BM 1171A

Water level

7N/10W-5E1

2,200

2,300

2,350

2,150

2,250

2,200

2,300

2,350

2,150

2,250
Simulation Of Ground-Water Flow 25

nearby well 7N/12W-15F1. The measured land 

subsidence at BM 1171A east of Lancaster is related to 

the water-level decline measured in nearby well 

7N/10W-5E1 from about 1950–70, however the 

continued measured land subsidence from 1970s to the 

early 1990s does not correspond to the measured 

water-level recovery in the nearby well during this 

same time period. The subsidence that occurred at 

BM 1171A from the 1970s to the early 1990s may be 

the result of residual compaction.

SIMULATION OF GROUND-WATER FLOW

The objective of constructing a numerical 

ground-water flow model of the Antelope Valley 

ground-water basin was to gain a better understanding 

of the aquifer system and to develop a tool for 

evaluating and predicting aquifer responses to various 

water-management alternatives. Because land 

subsidence has been occurring in the Antelope Valley 

since the 1930s (Ikehara and Phillips, 1994; Galloway 

and others, 1998), a significant amount of the water 

being pumped in the valley may come from the 

compacting sediments. It is important, therefore, that a 

model of the valley have the capability to simulate 

compaction. Results of aquifer-system compaction 

simulations can be used to evaluate the potential for 

future compaction and land subsidence due to waterlevel declines in the valley.

The numerical model used for this study is the 

USGS modular three-dimensional finite-difference 

ground-water flow model (MODFLOW) (McDonald 

and Harbaugh, 1988). The basic MODFLOW code was 

used with the Interbed Storage 1 (IBS1) Package 

(Leake and Prudic, 1991) to simulate aquifer-system 

compaction and land subsidence and the Horizontal 

Flow Barrier (HFB) Package (Hsieh and Freckleton, 

1993) to simulate the effect of horizontal barriers, such 

as faults, to ground-water flow. Ground-water levels 

were calculated at discrete points by solving 

simultaneous equations that approximate the partial 

differential equation for ground-water flow. The 

discrete points are the result of discretization of the 

model area into a series of layered rectangular model 

cells with the points (or nodes) located at the center of 

model cells. Land subsidence is computed at a model 

cell by summing the compaction simulated in each of 

the model layers, and is reported for the model cell in 

the uppermost layer. 

The model can simulate ground-water levels and 

fluxes and aquifer-system compaction on the basis of 

the ability of the aquifer system to transmit water 

(transmissivity), its capacity to store and release water 

(storage coefficient), and the applied hydrologic 

stresses (recharge and discharge). The model, however, 

is only an approximation of the aquifer system being 

simulated and, therefore, cannot exactly duplicate or 

represent the actual system. Because model 

development requires the use of data, assumptions, and 

simplifications to approximate the system, the model is 

only as accurate as the assumptions and data used to 

develop the model.

Model Discretization and Boundaries

The model grid consists of 43 rows and 60 

columns with a total of 2,580 square cells (fig. 10). 

Each cell represents 1 mi2 with a distance of 5,280 ft (1 

mi) on a side. The aquifer system was discretized 

vertically into three layers. Layer 1 represents the 

upper aquifer and is unconfined throughout most of the 

ground-water basin. Around the southern part of 

Rogers Lake and west to Rosamond Lake, where 

surface clays act as a confining unit for the aquifer, 

layer 1 was simulated as confined or unconfined, 

depending on the water level. Where layer 1 is 

unconfined, the upper boundary of the layer is the 

water table. Where layer 1 is confined, the upper 

boundary of the layer is the bottom of the confining 

clay, which is 61 to 285 ft below land surface. The 

lower boundary of layer 1 is at an altitude of 1,950 ft 

above sea level. Layer 2 is confined and represents the 

middle aquifer, which extends from 1,950 to 1,550 ft 

above sea level. Layer 3 is confined and represents the 

lower aquifer, which extends from 1,550 to 1,000 ft 

above sea level. Layers 1, 2, and 3 have 921, 626, and 

536 active model cells, respectively. The lacustrine 

deposits in each aquifer are included in the layers 

representing the aquifers. Alluvial material at depths 

below 1,000 ft above sea level was assumed to be wellindurated, impermeable, and not a significant part of 

the regional flow system. Where the altitude of bedrock 

is above the defined layer bottom, the layer bottom is 

equal to the altitude of bedrock. The model grid and the 

lateral boundaries of the model layers are shown in 

figure 10.
26 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 10. Model grid and boundaries of model layers in the ground-water flow model of the Antelope Valley ground-water basin, California.

118o30'

Rogers

Lake

(dry)

Buckhorn

Lake

(dry)

Fremont

Valley

Rosamond

Lake

(dry)

Rosamond Hills

ROW 1

1 10 20 40 50 60

1020

30

40

43

10

10

00

20

20 Kilometers

Miles

118o00'

PEERLESS

LANCASTER

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

San Gabriel Mts

Little

Buttes

Amargosa

Creek

Cottonwood

Wash

Rock

Big

Wash

Creek

Rock Little

COLUMN

35o00'

34o30'

Tehachapi Mts NORTH MUROC

AlpineButtes

AntelopeButtes

30

EAFB

Main

Base

LovejoyButtes

Mojave

Boron

Rosamond

Quartz Hill

Lancaster

Palmdale

Littlerock

Edwards Base

Bissell Hills Air Force

Fault—Dashed where inferred (modified

from Dibblee, 1963; Ward and others,1993; Nishikawa and others, 2001)

Bedrock

Playa surface

Antelope Valley drainage

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope

Valley ground-waterbasin (modified fromCarlson and others, 1998)

Layer 1Layer 2Layer 3

Model boundaries (no flow)—Model cell

Time-varying specified

head cell

EXPLANATION
Simulation Of Ground-Water Flow 27

Temporally, the model was discretized into 81 

stress periods, each 1 year in length, in which specified 

stresses were held constant. These 1-year periods were 

selected to correspond to the intervals when groundwater pumpage was reported and water levels in wells 

in the monitoring network were measured. Water levels 

and aquifer-system compaction in each active model 

cell were output from the model at the end of each 

stress period.

Except for the area around Rogers Lake where 

layer 1 may be confined by clay, the upper boundary of 

the model is the water table. It was simulated as a freesurface boundary that was allowed to move vertically 

in response to imbalances in the inflows and outflows 

to the model. The lateral boundaries of the model are 

all no-flow boundaries, except one boundary cell 

representing the area north of Rogers Lake where 

ground water discharges into the Fremont Valley. No 

water enters or leaves the system at the no-flow 

boundaries. These lateral boundaries are located at the 

contact between the aquifer and bedrock or barrier 

faults. To simulate discharge into Fremont Valley, the 

model cell for layer 1 for this location was designated 

as a time-varying specified-head boundary (fig. 10)

where water can enter or leave the system as 

determined by the water-level gradient between this 

cell and adjacent active cells. The specified head in this 

cell was varied for each stress period on the basis of 

water-level data from nearby wells (Nishikawa and 

others, 2001). The lower boundary of the model also is 

a no-flow boundary. This no-flow boundary is located 

where the aquifer comes into contact with bedrock or at 

an altitude of1,000 ft above sea level, below which the 

deposits were assumed to be non-water-bearing.

Model Parameters

Simulation of ground-water flow and fluxes and 

aquifer-system compaction requires specifying aquifersystem properties and stresses. Aquifer-system 

properties can vary considerably both horizontally and 

vertically and thus cannot be precisely represented in a 

numerical model. The aquifer-system properties 

specified for each active cell in the model are estimates 

of the average conditions in the area represented by the 

cell. Similarly, stresses applied to the system (recharge 

and discharge) are estimates for the area represented by 

each cell. The initial aquifer-system properties, with 

the exception of the storage coefficients for confined 

aquifers specified for layers 1 and 2, were obtained 

from the Durbin (1978) model. Recharge and pumpage 

were estimated as described in earlier sections of this 

report. Selected properties and stresses were modified 

within reasonable limits during model calibration: the 

modifications were made on the basis of recently 

collected hydrologic data and parameters used in the 

ground-water flow models of the Edwards Air Force 

Base area (Sneed and Galloway, 2000; Nishikawa and 

others, 2001).

Hydraulic Conductivity and Transmissivity

Ground-water flow within the model layers was 

assumed to be horizontal. Hydraulic conductivity and 

transmissivity are properties that, in conjunction with 

the horizontal hydraulic gradient, control horizontal 

flow of ground water. Hydraulic conductivity is a 

measure of the water transmitting properties of aquifer 

material; coarse and (or) well-sorted material have a 

higher hydraulic conductivity than fine and (or) poorly 

sorted material. Transmissivity is the product of 

hydraulic conductivity and saturated thickness and 

represents the water-transmitting properties of the 

saturated section of the aquifer. Hydraulic conductivity 

was specified for layer 1 and transmissivity was 

specified for layers 2 and 3, because layer 1 is 

unconfined throughout most of the basin and layers 2 

and 3 are confined. Hydraulic conductivity was 

specified for layer 1 to allow the model to compute 

changes in the transmissivity as the saturated thickness 

changes in the aquifer.
28 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Total aquifer-system transmissivity (the 

combined transmissivities represented by model layers 

1–3, in feet squared per day) was estimated from 

specific-capacity data by multiplying the specific 

capacity (in gallons per minute per foot of drawdown) 

by a conversion factor of 230 (Thomasson and others, 

1960). The specific-capacity data used to calculate 

transmissivity for this current study were from Bloyd 

(1967) and from more recent data from wells owned by 

the Los Angeles County Department of Public Works 

(James Hong, Los Angeles County Department of 

Public Works, Waterworks and Sewer Maintenance 

Division, written commun., 1997). The current 

estimates of transmissivity were consistent with those 

used in the Durbin (1978) model, which were obtained 

using data from Bloyd (1967). Transmissivities 

estimated from specific-capacity data probably are only 

approximations of the total transmissivity of the 

aquifer system because the wells from which the 

specific-capacity data were obtained were not 

perforated over the entire thickness of the aquifer 

system.

The initial transmissivity of layer 2 was 

calculated as the product of the saturated thickness 

(400 ft, except where bedrock is higher than 1,550 ft 

above sea level) and a hydraulic conductivity of 10 ft/d. 

The initial transmissivity of layer 3 was calculated as 

the product of the saturated thickness (550 ft, except 

where bedrock is higher than 1,000 ft above sea level) 

and a hydraulic conductivity of 2 ft/d. The hydraulicconductivity values used for layers 2 and 3 were based 

on values from the Edwards Air Force Base model 

(Nishikawa and others, 2001) and on the preliminary 

results of modeling of the southern part of the 

Lancaster subbasin (Phillips and others, in press). The 

initial transmissivity of layer 1 was calculated by 

subtracting the sum of the initial transmissivities for 

layers 2 and 3 from the total transmissivity calculated 

from the specific-capacity data. The initial hydraulic 

conductivity for layer 1 was then calculated by dividing 

the initial layer 1 transmissivity by the predevelopment saturated thickness of layer 1, which was 

estimated using water-level estimates from Durbin 

(1978) (fig. 4). To avoid unreasonably low values of 

hydraulic conductivity in layer 1, a minimum 

hydraulic-conductivity value of 2 ft/d was specified for 

the cells in that layer. The transmissivity of layers 2 and 

3 remained constant throughout the entire simulation 

period because the water table never declined below 

the top of layer 2. Initial hydraulic-conductivity and 

transmissivity values for the area around Rogers Lake 

were modified to generally agree with the values used 

in a three-dimensional model developed by for the 

Edwards Air Force Base area (Nishikawa and others, 

2001). 

Vertical Leakance

Ground-water flow between model layers was 

assumed to be vertical and to occur when there is a 

difference in hydraulic head between layers. The 

vertical conductance between layers, which represents 

the ability of the aquifer to transmit water vertically, is 

calculated by the model using a specified vertical 

leakance value and the cell dimensions. The vertical 

leakance between model cells, which is a function of 

cell thickness and vertical hydraulic conductivity, was 

calculated outside the model using the following 

equation from McDonald and Harbaugh (1988):

, (2)

where

Equation 2 strongly weights the smaller of the 

two vertical hydraulic conductivity values. For 

example, if one layer contains thick lacustrine deposits 

of silt and clay and the other layer contains mostly 

alluvial deposits of sand and gravel, the vertical 

leakance between the layers is dependant mostly on the 

vertical hydraulic conductivity of the lacustrine 

deposits. The vertical hydraulic conductivities of layers 

1, 2, and 3 were assumed to be one-hundreth of the 

horizontal hydraulic conductivities in areas where the 

lacustrine deposits are not present between the centers 

of adjacent layers. Where lacustrine deposits are 

λk+1/2 is the vertical leakance between layers

k and k+1 [t–1],

∆zk is the thickness of layer k [L],

∆zk+1 is the thickness of layer k+1 [L],

Kzk is the vertical hydraulic conductivity 

of layer k [Lt–1], and

Kzk+1 is the vertical hydraulic conductivity 

of layer k+1 [Lt–1].

λk + 1 2⁄

1

∆zk ⁄ 2

Kzk

------------------ ∆zk + 1 ⁄ 2

Kzk + 1

+ -------------------------

= ---------------------------------------------------
Simulation Of Ground-Water Flow 29

present in a layer, the vertical hydraulic conductivity of 

the lacustrine deposits was used for that layer. An 

estimate of 1.0×10−2 ft/d was used for the vertical 

hydraulic conductivity of the lacustrine deposits, which 

is consistent with the value used by Durbin (1978) and 

three orders of magnitude higher than the value used by 

Nishikawa and others (2001).

Storage Coefficient

The storage (specific yield or storage coefficient) 

of water-bearing material is the quantity of water 

released from storage per unit area per unit decline in 

hydraulic head. The water released from storage is 

derived from the compression of the granular matrix 

(skeleton) of the aquifer system and the expansion of 

fluid. In confined and unconfined aquifer systems the 

release of water from storage in low-permeability, 

unconsolidated fine-grained sediments is accompanied 

by some degree of compression of the fine-grained 

sediments. The relation between changes in head, 

expressed as an equivalent change in pore-fluid 

pressure, and compression of the aquifer system is 

based on the principle of effective stress first proposed 

by Terzaghi (1925) for one-dimensional vertical 

consolidation of saturated sediment,

σe = σT – p, (3)

where effective or intergranular stress (σe) is the 

difference between the total stress (σT) and the porefluid pressure (p). Under this principle, when the total 

stress remains constant, a change in pore-fluid pressure 

causes an equivalent change in effective stress within 

the aquifer system, which causes the aquifer system to 

expand or compress under the new load. In aquifer 

systems, conditions that cause changes in the total 

stress include the erosion or aggradation of sediment at 

land surface, or more commonly a change in the 

position of the water table overlying confined aquifers. 

For purposes of this discussion, the total stress is 

assumed constant.

When the effective stress is decreased by an 

increase in pore-fluid pressure, the aquifer system 

expands elastically. When the effective stress is 

increased by a reduction in pore-fluid pressure and the 

effective stress does not exceed the maximum past 

effective stress, the aquifer system compresses 

elastically. When a reduction in pore-fluid pressure 

causes an increase in effective stress that exceeds the 

previous maximum effective stress, the pore structure 

of the fine-grained sediments (aquitards) in the aquifer 

system undergoes significant rearrangement, resulting 

in permanent (inelastic) rearrangement of the granular 

structure, a reduction in pore volume and permanent 

compaction of the aquitards.

The elastic and inelastic skeletal 

compressibilities, α′k, of the aquitards are expressed in 

terms of the skeletal specific storages, S′sk,

S′sk = S′ske = α′kepg, σe ≤ σe(max), (4)

S′sk = S′skv = α′kvpg, σe > σe(max),

where the primes denote aquitard properties, the 

subscript k refers to the skeletal component of specific 

storage, or compressibility, subscripts e and v refer to 

the elastic and virgin (inelastic) properties, p, is fluid 

density, and g is gravitational acceleration. For a 

change in effective stress, the aquitard deforms 

elastically when the effective stress is less than the 

previous maximum effective stress, σe(max); when the 

effective stress is greater than σe(max), the aquitard 

deforms inelastically. The previous maximum stress is 

termed the preconsolidation stress or, expressed as an 

equivalent hydraulic head is termed the 

preconsolidation head.

In typical aquifer systems composed of 

unconsolidated to semi-consolidated Cenozoic 

sediments, S′skv is generally 30 to several hundred 

times larger than S′ske (Ireland and others, 1984). The 

product of the elastic or inelastic skeletal specific 

storage and the aggregate thickness of the aquitards, 

∑b′, is the aquitard skeletal storage coefficient S′k:

S′k = S′ke = S′ske (∑b′), σe ≤ σe(max), (5)

 S′k = S′kv = S′skv (∑b′), σe > σe(max),

for the elastic (S′ke) and inelastic (S′kv) range of skeletal 

compressibility, respectively. A similar set of 

equations, one for the coarse-grained aquifers and one 

for pore water, relates the compressibility of the aquifer 

skeleton (αk) to the aquifer skeletal storage coefficient 

(Sk) and the compressibility of water (βw) to the 

component of aquifer-system storage attributed to the 

pore water (Sw):

Sk = Ssk (∑b) = αkpg(∑b), (6)

Sw = βwpg[n(∑b) + n′ (∑b′)], (7)
30 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

where ∑b is the aggregate thickness of the aquifers and 

n and n′ are the porosities of the aquifers and aquitards, 

respectively. For coarse-grained aquifers interbedded 

with compressible aquitards, the difference between 

the elastic and inelastic compressibilities of the aquifer 

skeleton is considered relatively insignificant, and 

αk ≅ αke.

The aquifer-system storage coefficient S is 

defined as the sum of the skeletal storage coefficients 

of the aquitards and aquifers (equations 5–6) plus the 

storage attributed to water compressibility (equation 7). 

Thus,

S = S′k + Sk + Sw. (8)

For compacting aquifer systems, S′skv >> Ssw

(specific storage of water), and the inelastic storage 

coefficient of the aquifer system is approximately equal 

to the inelastic aquitard skeletal storage coefficient, Sv

≅ S′kv. In confined aquifer systems subject to largescale overdraft, the volume of water derived from 

permanent aquitard compaction can typically range 

from 10 to 30 percent of the total volume of water 

pumped and represents a one-time mining of stored 

ground water and a small permanent reduction in the 

storage capacity of the aquifer system.

In unconfined aquifer systems the skeletal 

storage coefficients described above also govern the 

compressibility of the fine-grained sediments below the 

water table and contribute to the volume of water 

released from storage when heads decline, and is 

defined by the specific yield, Sy, of the aquifer system. 

Water derived from storage in unconfined aquifer 

systems primarily results from the gravity drainage of 

pore water from the sediments and its value is typically 

in the range of 0.1–0.3, somewhat less than the 

porosity, and somewhat greater than the specific 

retention of the sediments. Typically, Sy >> S by two to 

three orders of magnitude.

For confined and unconfined aquifers, the IBS1 

Package requires that storage coefficient terms be 

specified for the elastic skeletal storage coefficient 

(Ske), and inelastic aquitard skeletal storage coeffficient 

(S′kv) (Leake and Prudic, 1991). For confined aquifers, 

in order to account for the component of storage related 

to the compressibility of water, Sw was entered as the 

storage coefficient in the BCF package of MODFLOW. 

Within MODFLOW these three storage components 

(Ske,S′kv, and Sw) are summed and the storage 

coefficient of the aquifer system, S, is implemented for 

each model layer. For unconfined aquifers, IBS1 

requires the two components of the skeletal storage 

coefficient. In contrast with the procedure used to 

implement the aquifer-system storage coefficient for 

confined aquifers, the specific yield (Sy) was entered as 

the storage term in the input file for the BCF package 

for layer 1, and this value was used by the model where 

and when unconfined aquifer conditions occurred in 

that model layer. Note that the specific yield of an 

unconfined aquifer is many orders of magnitude greater 

than storage coefficient associated with the 

compressibility of water. Therefore, the water released 

from storage owing to the expansion of water is 

negligible with respect to the amount released by the 

gravity drainage of pore water. In this model, it was 

assumed that compaction occurs only in layers 1 and 2. 

Because little pumping occurs in layer 3 and because 

sediments in layer 3 have been subjected to fairly large 

overburden stress, it was assumed that there is little 

potential for compaction of this layer.

The initial storage coefficients for the model 

were calculated using specific-storage values obtained 

from one-dimensional (Sneed and Galloway, 2000) and 

three-dimensional (Nishikawa and others, 2001) 

models of ground-water flow and aquifer-system 

compaction at Edwards Air Force Base. The specific 

storage values range from 4.2×10−7 ft−1 for the 

compressibility of water (Ssw)to 3.5×10−4 ft−1 for the 

inelastic skeletal specific storage (S′skv) of thick 

(greater than 18 ft) aquitards (table 4). The initial 

storage coefficients for the compressibility of water 

(Sw) and elastic skeletal storage (Sk) for layers 1 and 2 

were calculated as the product of the respective 

specific-storage value and the saturated thickness of the 

layer. The initial inelastic aquitard skeletal storage 

coefficients (S′kv) were calculated as the product of the 

inelastic specific storage of thick aquitards and the 

estimated total thickness of aquitards within the 

aquifer. 
Simulation Of Ground-Water Flow 31

The total thickness of the aquitards in layers 1 

and 2 was estimated from the percentage of the finegrained sediments in these layers that was determined 

from descriptions of the aquifer material noted in 

selected well drillers’ logs. The percentage of finegrained sediments ranged from 13 to 50 percent of the 

thickness of each layer. The inelastic aquitard skeletal 

storage coefficient was specified only for those areas of 

layers 1 and 2 where subsidence of more than 1 ft had 

been measured in the study area (fig. 8). Compaction 

was not simulated for layer 3; therefore, the storage 

coefficient for layer 3 was estimated by multiplying the 

specific storage of the aquifer by the thickness of the 

layer (550 ft). A specific storage of 2.0×10−6 ft-1 was 

assumed representative of the aquifer materials in layer 

3, resulting in a storage coefficient of 1.0×10−3. This 

value was used throughout layer 3, regardless of the 

thickness of the layer, except for the model area near 

Rogers Lake, north of the Willow Springs Fault. The 

storage coefficient calibrated by Nishikawa and others 

(2001) during the simulation of ground-water flow and 

land subsidence at Edwards Air Force Base 

(5.71×10−4) was used in the model area north of 

Willow Springs Fault. 

Specific-yield values used in the Durbin (1978) 

model for the unconfined aquifer ranged from 0.05 to 

0.20: these values were used as initial values for the 

upper aquifer. Microgravity measurements collected 

from 1996–98 as part of an injection, storage, and 

recovery test at Lancaster were used to estimate a 

specific yield of about 0.13 (Howle and others, 2003).

Preconsolidation Head

As noted earlier, inelastic compaction of 

compressible sediments occurs when water levels 

decline below the preconsolidation head. Accurate 

estimates of preconsolidation head values are critical 

for the simulation of subsidence (Sneed and Galloway, 

2000); the initial values of preconsolidation head for 

the model were based on results from the onedimensional model of ground-water flow at Edwards 

Air Force Base (Sneed and Galloway, 2000). Initial 

preconsolidation head values were specified from 0 to 

50 ft below pre-development water levels only for 

those areas that have 1 ft of measurable subsidence (fig. 

8). If future water levels decline below 

preconsolidation heads outside the areas of subsidence 

shown in figure 8, then subsidence may occur in those 

areas. The magnitude and distribution of 

preconsolidation heads for the areas that have no 

measurable subsidence are not known and, therefore, 

calibration of preconsolidation heads for these areas is 

not possible. Subsidence was not simulated for those 

areas because there is no constraint for the range of 

preconsolidation heads.

Table 4. Specific storage values used in calculating storage coefficients 

for layers 1 and 2 in the ground-water flow model of the Antelope Valley 

ground-water basin, California

[Data from Sneed and Calloway, 2000; Nishikawa and others, 2001. 

ft−1, per foot]

Specific storage

(ft−1)

Compressibility of water............ 4.2×10−7

Elastic skeletal specific storage.. 1.7×10−6

Inelastic skeletal specific storage for thin 

aquitards (less than or equal to 18 feet thick) 4.0×10−5

Inelastic skeletal specific storage for thick 

aquitards (greater than 18 feet thick) 3.5×10−4
32 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Horizontal-Flow Barriers

Nine faults that transect the ground-water basin 

were simulated as partial barriers to ground-water flow 

(fig.11, table 5). The Horizontal-Flow Barrier (HFB) 

package (Hsieh and Freckleton, 1993) was used to 

simulate these faults as horizontal-flow barriers. The 

HFB package allows for the simulation of thin, vertical, 

low-permeability geologic features, such as vertical 

faults and fine-grained material, that act as partial 

barriers to horizontal ground-water flow. The function 

of each simulated barrier is to lower the horizontal 

conductances between two adjacent model cells. The 

barriers are defined by a hydraulic characteristic, which 

for unconfined aquifers is the hydraulic conductivity of 

the fault divided by the width of the fault and for 

confined aquifers is the transmissivity of the fault 

divided by the width of the fault. Each barrier may be 

subdivided into segments and each segment may have a 

different hydraulic characteristic. All the barriers 

simulated in the model were assumed to extend 

through all three model layers. The hydraulic 

characteristic value for each segment (table 5) was 

determined by model calibration.

The simulated barriers include an unnamed fault 

between Finger Buttes and West Antelope subbasins 

(barrier 1), the Randsburg–Mojave Fault (barrier 2), the 

Neenach Fault (barrier 3), and an unnamed fault 

between the Buttes and Pearland subbasins (barrier 4) 

(fig. 11, table 5). These four barriers were simulated as 

partial barriers to ground-water flow in the Durbin 

(1978) model. The fault separating the Buttes and 

Pearland subbasins from the Lancaster subbasin (fig. 

11) was not simulated as a barrier to flow in the Durbin 

(1978) model. This fault also was not simulated as a 

barrier to flow in this model. Five of the faults 

simulated as partial barriers to flow were not simulated 

as barriers in the Durbin (1978) model. These faults 

include the extensions of the Muroc Fault (barrier 5) 

and the El Mirage Fault (barrier 6) across Rogers Lake 

and an extension of the Willow Springs fault from the 

northwest corner of Rosamond Lake southeast along 

the southern edge of Buckhorn Lake to the eastern edge 

of the study area (barrier 7). These faults were 

simulated as partial barriers to flow in the Edwards Air 

Force Base model (Nishikawa and others, 2001). Two 

additional partial barriers to flow were inferred from 

water-level data and model calibration; one barrier 

southeast of Lovejoy Buttes, parallel to the northeast 

boundary of the Buttes subbasin (barrier 8), and one 

barrier south of Rosamond Lake, trending northwestsoutheast from the Neenach Fault to the eastern edge of 

the study area (barrier 9). These barriers are believed to 

be related to faults that are not exposed at land surface.

Model Stresses

Hydraulic heads in the ground-water flow system 

respond to stresses on the system, which correspond to 

recharge and discharge. As noted earlier, recharge to 

the ground-water system includes natural recharge 

from mountain-front runoff and stream infiltration in 

the upper reaches of ephemeral streams and artificial 

recharge of irrigation-return flow and treated 

wastewater. Discharge from the ground-water systems 

includes evapotranspiration, ground-water outflow, and 

ground-water pumpage.

Natural Recharge

Natural recharge from mountain-front runoff and 

stream infiltration was simulated as areal recharge to 

layer 1, the location of the recharge cells are shown in 

figure 12. The initial value of total annual natural 

recharge was assumed to be 40,700 acre-ft, the value 

simulated in the Durbin (1978) model. The distribution 

of natural recharge was based on the location and size 

of the intermittent streams used to estimate natural 

recharge (Durbin, 1978). The initial annual recharge 

specified for these cells ranged from 65 to 3,800 acre-ft 

for each cell. Natural recharge did not vary from year 

to year because data were limited, which precluded 

simulating seasonal or annual variations in natural 

recharge. Results from a study by Bouwer (1982) 

indicate that seasonal and annual fluctuations in 

infiltration are attenuated as a function of sediment 

particle size in the unsaturated zone and vertical 

distance to the water table. Natural recharge was not 

specified for the entire reach of streams in the basin 

because the streams are intermittent and flow does not 

always occur over the entire length of the stream.
Simulation Of Ground-Water Flow 33

Figure 11. Location of barriers to horizontal ground-water flow simulated in the ground-water flow model of the Antelope Valley ground-water basin, California.

118 o30' Mojave

Boron

Rogers Lake

(dry)

Rosamond

Lake

(dry)

Buckhorn

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

Rock

Creek

Big

Creek

Cottonwood

Amargosa

118o00'

LANCASTER

Wash Rock

Fremont

Valley

COLUMN

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

Quartz Hill

PEERLESS

34o30'

0

0

10

10

20

20 Kilometers

Miles

Palmdale

Littlerock

Lancaster

Rosamond

35o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

2b

3b

3a

3c

2a

1

8

7

6

5

4a

4b

9

Playa surface

Edwards Air Force Base

Bedrock

Antelope Valley drainage

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope

Valley ground-water basin (modified fromCarlson and others, 1998)

Model layer 1

EXPLANATION

Fault—Dashed where

inferred (modified fromDibblee, 1963; Wardand others, 1993;

Nishikawa and others, 2001)

Cell boundaries representing flow barriers

Barrier number (3) and

segment identifier (a)(See table 5)

3a

Model cell

Edwards

Base

Air Force

EAFB

Main

Base

Edwards Base Air Force
34 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Artificial Recharge

Artificial recharge in the ground-water basin, as 

noted earlier, includes the infiltration of irrigationreturn flows of pumped ground water and imported 

water used for agriculture and treated wastewater 

discharged to spreading ponds. 

Irrigation-Return Flow

Irrigation-return flow is that portion of the water 

applied to crops that is not consumptively used by the 

crops. Irrigation efficiency, which is defined as the 

percentage of applied water used by the crops, was 

assumed to be 70 percent, leaving as much as 30 

percent of the applied irrigation water available to 

return to the water table as irrigation-return flow. In 

Antelope Valley, most of the applied water is for the 

production of alfalfa. The irrigation efficiency was 

estimated on the basis of the quantity of irrigation 

water applied to alfalfa [approximately 

6.6 ft/yr (Orloff and others, 1989)] and the quantity of 

water consumed by alfalfa [approximately 4.8 ft/yr 

(table 2)]. Estimates of irrigation efficiency by Snyder 

(1955) and by the California Department of Public 

Works (1955) were about 50 percent; however, 

consumptive-use estimates at the time of these two 

studies (3.4–3.6 ft/yr) were lower than current 

estimates (4.8 ft/yr). The current consumptive-use 

estimates were considered more accurate than the 

consumptive-use estimates used by researchers in the 

1950s; therefore, an irrigation efficiency of 70 percent 

was assumed valid for the entire simulation period. 

Because pumpage has caused ground-water 

levels to decline more than 100 ft throughout most of 

the ground-water basin and owing to the existence of 

thin aquitards within the aquifers, recharge from water 

applied for agriculture probably did not reach 

(recharge) the water table until about 10 years after 

application. The actual delay in irrigation-return flow 

reaching the water table probably is variable depending 

on the depth to water and the existence of fine-grained 

layers in the unsaturated zone. Irrigation-return flows 

were simulated as wells that had positive flow rates 

(i.e., flow recharging the ground-water flow system) at 

the cells where agricultural pumpage was simulated 

(fig. 5). The areas that had irrigation-return flows 

remained constant during 1915–51 but varied annually 

during 1952–95. Annual agricultural recharge varied 

from 0 to 111,000 acre-ft. 

Table 5. Hydraulic characteristics of the horizontal-flow barriers simulated in the ground-water flow model of the Antelope Valley ground-water basin, 

California

[d-1, per day; ft/d, foot per day. —, no barrier simulated in this layer]

1 Unnamed

Barrier 

No. Segment Barrier name

Hydraulic characteristic

Layer 1 (d-1) Layer 2 (ft/d) Layer 3 (ft/d)

1 (

1) 0.00008 0.0008 0.0008

2 a Randsburgq–Mojave Fault .00007 .0007 .0007

b .00002 .0002 .0002

3 a Neenach Fault .0008 .008 .008

b .002 .02 .02

c .004 .04 .04

4 a (

1) .0004 — —

b .0003 — —

5 Muroc Fault .001 .01 .01

6 El Mirage Fault .001 .01 .01

7 Willow Springs Fault .0001 .001 .001

8 (

1) .00001 — —

9 (

1) .00001 .0001 —
Simulation Of Ground-Water Flow 35

Figure 12. Location of model cells used to simulate natural recharge, recharge of imported water used for irrigation, and recharge of treated wastewater in the ground-water flow model of the Antelope Valley ground-water basin, California.

Cottonwood

Quartz

Hill

118o30'

118o30'

Mojave

Boron

Rosamond

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER

BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Creek

Wash

Amargosa

Creek

Rock Li

Fremont

ttle

Valley

Palmdale

Lancaster

LANCASTER

Rosamond

Little

Buttes

Antelope Buttes

Alpine Buttes

Lovejoy Buttes

ROW 1

1 10 20 40 50 60

10

20

30

40

43

34o30'

0

0

10

10

20

20 Kilometers

Miles

Wash

Rock

Big

Littlerock

Natural rechargeImported irrigation water

Natural recharge and

imported irrigation water

Treated wastewater

Recharge cells—

35o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

PEERLESS

Antelope Valley drainage

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope

Valley ground-water basin (modified fromCarlson and others, 1998)

EXPLANATION

Bedrock

Playa surface

Model cell

Model layer 1

COLUMN

EAFB

Main

Base

Rogers

Lake

(dry)

Buckhorn

Lake

(dry)

30
36 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Beginning in 1972, water was imported from 

northern California to Antelope Valley by way of the 

California aqueduct. Records of deliveries of imported 

water from the Antelope Valley–East Kern Water 

Agency (AVEK) show that growers began using large 

quantities of imported surface water in 1976. The 

records also indicate that most of the imported water 

was delivered to two areas of the valley; (1) the western 

part of the Lancaster subbasin, east of Antelope Buttes, 

and (2) the far western part of the study area, in the 

Finger Buttes, Neenach, and West Antelope subbasins 

(fig. 12). Thirty percent of the annual imported water 

delivered to these areas was specified as irrigationreturn flow and was simulated as wells that had positive 

flow rates into layer 1 of the model 10 years after the 

water was applied at land surface.

Treated Wastewater

The estimated annual quantity of treated 

wastewater that could infiltrate into the unsaturated 

zone is shown in table 1. The treated wastewater is 

from urbanized parts of the study area that are served 

by the water reclamation plants. Recharge from septic 

systems in the rural parts of the study area was 

assumed to be negligible. Recharge from treated 

wastewater was assumed to reach the water table in the 

year that it was applied at land surface because this 

source of water is essentially constant and the rate of 

infiltration per acre is much greater than that for 

agriculture. Recharge from the Palmdale Water 

Reclamation Plant was applied to only one cell (fig. 12)

for 1984–95, the years in which recharge from the 

treated wastewater was estimated to occur (table 1). On 

the basis of results of infiltration studies at the 

Lancaster Water Reclamation Plant, the assumption 

was made that recharge of treated wastewater from the 

plant does not reach the regional water table, and, 

therefore, it was not simulated for this site.

Natural Discharge

Evaporation from bare-soil and transpiration by 

phreatophytes in areas were the water table was near 

land surface were simulated using the 

Evapotranspiration Package developed by McDonald 

and Harbaugh (1988). These areas were identified 

using maps that show the area of flowing wells in 1908 

(Johnson, 1911) and alkali soils (Durbin, 1978) (fig. 

13). Estimates of evapotranspiration rates in Antelope 

Valley were based on results reported by Lines and 

Bilhorn (1996) in the nearby Mojave River Basin. An 

annual maximum evapotranspiration rate of 

0.6 ft/yr was specified when the water table was at land 

surface and was decreased linearly to zero when the 

water table reached a depth of 10 ft below land surface.

Durbin (1978) estimated that 1,000 acre-ft/yr of 

ground water is discharged as ground-water underflow 

north of Rogers Lake into Fremont Valley: this estimate 

was based on the water-level gradient and the crosssectional area of the aquifer. Water-level data from 

nearby wells indicate that the gradient at that location 

has not been constant over time, which suggests that 

subsurface ground-water flow has not been constant 

(Nishikawa and others, 2001). Variable subsurface 

ground-water flow was specified in the transient-state 

simulation using a time-varying specified-head cell 

(fig. 13). The water level at the specified-head cell (fig. 

14) was based on water-level data from nearby wells 

(Nishikawa and others, 2001), and flow out of the study 

area into Fremont Valley was calculated by the model 

using the gradient between the specified-head cell and 

adjacent active cells.

Pumpage

Total annual pumpage specified in the model is 

shown in figure 5. The spatial distribution of pumpage 

for 1915–51 was based on the Durbin (1978) model. 

The spatial distribution of pumpage for 1915–51 was 

concentrated primarily in agricultural areas and did not 

vary over time. The spatial distribution of pumpage for 

1952–95 was based on the spatial distribution of 

pumpage in the database created by Templin and others 

(1995) and updated for this study (see Appendix: Water 

Use 1992–95). The pumpage database contains annual 

pumpage data for individual wells and information on 

the location of these wells. Well location data allowed 

the spatial distribution of pumpage in the model to vary 

for 1952–95, years when the primary pumping centers 

moved from agricultural areas to urban areas. The 

pumpage database, however, does not contain data for 

all agricultural pumpage in the study area; therefore, 

land-use data were used in conjunction with the 

database to simulate the distribution of agricultural 

pumpage.
Simulation Of Ground-Water Flow 37

Figure 13. Location of model cells used to simulate natural ground-water discharge in the ground-water flow model of the Antelope Valley ground-water basin, California.

Creek

Cottonwood

118o30' Mojave

Boron

NORTH MUROC

OAK CREEK

NEENACH

FINGER

BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

Rock Big

Wash

Creek

Rock Lit

Fremont

tle

Valley

Lancaster

Littlerock

LANCASTER

ROW 1

1 10 20 40 50 60

1020

30

40

43

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

Amargosa

Bissell Hills

Rosamond Hills

34o30'

Rosamond

Lake

(dry)

Rosamond Rosamond Buckhorn Lake

(dry)

Rogers

Lake

(dry)

QuartzHill

Model cells where evapotranspiration was simulated

Time-varying, specified-head

cell

35o00'

Tehachapi Mts

San Gabriel Mts

0

0

10

10

20

20 Kilometers

Miles

Palmdale

118o00' COLUMN

30

PEERLESS

Antelope Valley drainage

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope

Valley ground-waterbasin (modified fromCarlson and others, 1998)

EXPLANATION

BedrockPlaya surface

Model cell

Alkali soils (modified from

Model layer 1

Durbin, 1978)

EAFB

Main

Base
38 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

A comparison of the spatial distribution of 

pumpage in the database and land-use data for 1961 

and 1987 indicated that the database does not have 

pumpage data for areas of agricultural land use in the 

West Antelope and the western Neenach subbasins. 

The land-use data showed that about 6.8 percent of the 

total agricultural land in the study area was in these 

areas; therefore, the annual agricultural pumpage for 

these areas was assumed to be 6.8 percent of the total 

annual agricultural pumpage. Agricultural pumpage in 

the West Antelope and the western Neenach subbasins 

was distributed to model cells corresponding to the 

location of the agricultural land use. Pumpage in these 

areas was assumed to have occurred between 1934 and 

1986: this assumption was based on a comparison of 

simulated water levels and measured water levels for 

well 8N/17W-1N1 (well location shown in fig. 15) in 

the West Antelope subbasin. 

The spatial distribution and quantity of pumpage 

for public supply for 1919–91was determined from the 

pumpage database compiled by Templin and others 

(1995) and for 1992–95 from water-use information 

compiled for this study (Table A1 in the Appendix). 

The location and quantity of pumpage from public 

supply wells is well documented, and was not changed 

during the calibration process.

Because there was limited well-construction data 

available, all wells were assumed to be fully perforated 

in both layers 1 and 2. The proportion of pumpage from 

a layer was determined by dividing the transmissivity 

of that layer by the sum of the transmissivity of layers 1 

and 2. The transmissivity of layer 1 was calculated as 

the product of hydraulic conductivity and initial (1915) 

saturated thickness. The vertical distribution of 

pumpage from layers 1 and 2 varied spatially but did 

not vary with time; therefore, a limitation of this 

approach is that the vertical distribution of pumpage 

does not change as the water table declines. In the 

aquifer system, changes in the saturated thickness of 

the upper aquifer changes the transmissivity of the 

upper aquifer, which affects the flow of water to wells. 

It was assumed that there was no pumpage from layer 3 

because few wells in Antelope Valley are deep enough 

to penetrate the lower aquifer and because the 

transmissivity of this layer is low. This assumption is 

valid particularly for the earlier part of the simulation 

period when rates for total annual pumpage were 

highest. During the latter part of the simulation period, 

wells were drilled in the lower aquifer (layer 3) and 

thus some pumping occurred from this aquifer. The 

limited pumping that occurred only from the lower 

aquifer was simulated as pumpage from layers 1 and 2.

Figure 14. Time-varying specified hydraulic head used for the north boundary of the ground-water flow 

model of the Antelope Valley ground-water basin, California (modified from Nishikawa and others, 2001).

2,160

2,170

2,180

2,190

2,200

2,210

1915 1925 1935 1945 1955 1965 1975 1985 1995

YEAR

HYDRAULIC HEAD, IN FEET ABOVE SEA LEVEL
Simulation Of Ground-Water Flow 39

Figure 15. Location of wells and bench marks used to calibrate the transient-state model of the Antelope Valley ground-water basin, California.

Creek

Cottonwood

R 17 W

T8N

T 10 N

T6N

T4NT2N

R 15 W R9W R7W

118o30' Mojave

Boron

Rogers

Lake

(dry)

Rosamond

Lake

(dry) Buckhorn Lake

(dry)

Littlerock

LANCASTER

Palmdale

Rosamond

0

0

10

10

20

20 Kilometers

Miles

Lancaster

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

1N1

34o30'

Quartz Hill

COLUMN

20B1

9K1

23G1

35M1

27F5-7

31M1

33J1

6N1 34D1

19E6

34D2

8R3

1Q1-3

10R1

11N1

13A1

19R1

ROW 1

1 10 20 30 40 50 60

10

20

30

4043

LovejoyButtes

Little

Buttes

AntelopeButtes

Creek

Wash

Amargosa

Rock Little

Wash

Big

Rock

Rock

Little

AlpineButtes

4E1

35o00'

36R1

R 13 W R 11 W

PEERLESS

OAK CREEK

NEENACH

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

CHAFFEE

NORTH MUROC

FINGER BUTTES

PEARLAND

Fremont

Valley

118o00'

EAFB

Main

Base

5N/10W-6N1

Bench mark and number

Well and numberNested piezometersite and number

Antelope Valley drainage basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope

Valley ground-waterbasin (modified fromCarlson and others, 1998)

EXPLANATION

Bedrock

Playa surface

Model layer 1

Model cell

1Q1-3

Fault—Dashed where inferred (modified

from Dibblee, 1963; Ward and others,1993; Nishikawa and others, 2001)
40 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Model Calibration

Model calibration is the process of making 

adjustments, within justifiable ranges, to initial 

estimates of selected model parameters and stresses to 

obtain reasonable agreement between simulated and 

measured values (for this model, water levels and land 

subsidence). Modifications were made to the initial 

estimates of the hydraulic conductivity of layer 1, the 

transmissivity of layer 2, specific yield, natural 

recharge, aquitard thickness, hydraulic characteristics 

of horizontal flow barriers, and preconsolidation head 

using a trial-and-error approach. Vertical leakance was 

recalculated after changes were made to any of the 

values used to calculate vertical leakance; hydraulic 

conductivity, transmissivity, or saturated thickness. The 

values of transmissivity and storage coefficient of layer 

3 were not changed from the initial values during the 

model calibration process because reasonable changes 

in these values had negligible affect on model results.

Prior to 1915, there was little ground-water 

development in Antelope Valley and the ground-water 

flow system was in a time-averaged state of 

equilibrium. Inflows from recharge were balanced by 

outflows as evapotranspiration and ground-water 

underflow, and water levels were essentially 

unchanging. This state of equilibrium was simulated by 

the steady-state model that represents conditions in 

1915. The addition of stress to the ground-water flow 

system owing to pumping resulted in an imbalance 

between inflows and outflows, which disturbed the 

state of equilibrium and resulted in time-varying or 

transient-state conditions. Ground-water conditions 

during the period 1915–95 were simulated with a 

transient-state model. During the calibration process 

both steady-state and transient-state simulations were 

used: the steady-state simulation was used to provide 

initial conditions for the transient-state simulation. Any 

changes made to the transient-state simulation were 

incorporated into the steady-state simulation and the 

steady-state simulation was rerun to ensure that the 

changes made during the transient-state simulation 

produced reasonable results for steady-state conditions. 

This process was repeated until a satisfactory match 

between measured and simulated results was obtained.

Steady-State Simulation

The steady-state simulation of 1915 conditions 

was made to provide initial conditions for the transientstate simulation. The steady-state simulation requires 

initial estimates of hydraulic conductivity, 

transmissivity, vertical leakance, hydraulic 

characteristics of horizontal flow barriers, natural 

recharge, and evapotranspiration (maximum 

evapotranspiration rate and extinction depth). Storage 

coefficients are not required for a steady-state 

simulation. 

For this study, only estimates of natural recharge 

and evapotranspiration were modified during the initial 

steady-state calibration. Initial estimates of hydraulic 

conductivity, transmissivity, vertical leakance, and 

hydraulic characteristics were modified during the 

transient-state calibration. A subsequent steady-state 

simulation was then run to verify that the changes 

made during the transient-state simulation to these 

parameters resulted in a reasonable steady-state 

simulation of 1915 conditions. Ground-water level 

measurements, made around 1915, from 21 wells were 

used to determine if the steady-state simulation 

provided reasonable initial conditions for the transientstate simulation (fig. 16, table 6). 

The final calibrated distribution of natural 

recharge is shown in figure 17; recharge ranged from 

65 to 3,250 acre-ft/yr per cell.Total natural recharge in 

the calibrated steady-state simulation was 30,300 acreft/yr, 10,400 acre-ft/yr less than the natural recharge 

simulated in the Durbin (1978) model (40,700 acreft/yr). Most of the reduction in simulated natural 

recharge occurred in the Pearland and Buttes 

subbasins; natural recharge was decreased from an 

initial estimate of 26,500 acre-ft/yr (Durbin, 1978) to 

16,200 acre-ft/yr. Simulated water levels were higher 

than the measured water levels in these subbasins when 

the initial value of natural recharge was simulated. No 

reasonable combination of hydraulic conductivity, 

transmissivity, and values of hydraulic characteristic of 

flow barriers resulted in acceptable simulated water 

levels for these subbasins when the initial value of 

natural recharge was used in the steady-state 

simulation. 
Simulation Of Ground-Water Flow 41

Figure 16. Location of wells used to calibrate the steady-state simulation and measured and simulated steady-state water levels from the ground-water flow model of the Antelope Valley groundwater basin, California.

WEST ANTELOPE

Mojave

Boron

Rogers Lake

(dry)

Buckhorn

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash Rock

Wash

Creek

Rock Little LANCASTER

Fremont Valley

PEERLESS 50

ROW 1

1 10 20 30 40 60

10

20

30

40

43

Creek Cottonwood

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

Amargosa

0

0

10

10

20

20 Kilometers

Miles

2,260

COLUMN

Rosamond

Lake

(dry)

Big

3,000

2,340

2,360

2,300

2,320

2,380

2,380

2,400

36D2

2 400 ,

2 600 ,

2,360

2,340

2,800

3,200

2,900

2,800

2,700

2,600

2,500

2,900

3,100

3,000

2,500

2 500 ,

2,380 ,400 2

2,600

2,500

2,900

3 0, 00

3,100

3,200

3,300

2,800

2,700

2,600

2,240

2,700

3,100

2,500

3,200

2,900

2,600

360 2,

3,000

2,380

2,320

2,340

2,360

2,300

280 2,

, 2400

2,800

2,400

2,600

2,500

2,800

2,900

2,800

2,900

2,900

2,7 00

, 2600

2,380

2,400

2,240

2,700

2,

2,220

200

2,280

Palmdale

Lancaster

Littlerock

Rosamond

Quartz Hill

2,260

2,600

2,700

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

26Z1

30K2

10E1 6Q2

30D1 24B1

22D1

11D5

19A4 21A1

10D1

5D1

31A1

5N2

14R1

9(162)

20(6)

34(3)

14Z1

21D4

2,500

2,600

Line of equal water level altitude—

Interval variable, in feet. Datum issea level. Contour interval is variable

Measured (1915)—(modified from

Durbin, 1978)

Simulated—(steady-state simulation)

Well and number (table 6) 10E1

Antelope Valley drainage basin

Subbasin (modified from Bloyd,1967)

Study area—Antelope Valley ground- water basin (modified from Carlson

and others, 1998)

Model layer 1

Fault—Dashed where inferred

Model cell

(modified from Dibblee, 1963; Wardand others, 1993; Nishikawa andothers, 2001)

EXPLANATION

Bedrock

Playa surface

Boundaries—

35o00'

118o30'

118o00'

34o30'

T8N

T6N

T4NT2N

T 10 N

R 17 W R 15 W R9W R 13 W R 11 W R 7 W

EAFB

Main

Base
42 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

The initial maximum simulated 

evapotranspiration rate of 0.6 ft/yr and extinction depth 

of 10 ft below land surface were unchanged. 

Specifying a higher maximum rate had little effect on 

model results, and specifying a lower maximum 

evapotranspiration rate resulted in simulated water 

levels that were significantly higher than the measured 

water levels. 

The simulated steady-state water levels for layer 

1 ranged from 22 ft lower to 49 ft higher than the 

measured water levels (table 6). The simulated water 

levels for wells in the Lancaster subbasin were within 

12 ft of the measured water levels except for well 

9N/9W-20(6) for which the simulated water levels 

were 22 ft lower than the measured water levels. The 

simulated water levels ranged from 19 to 49 ft higher 

than the measured water levels in wells in the Neenach 

and West Antelope subbasins. The simulated water 

level for the single calibration well in the Pearland 

subbasin was 30 ft higher than the measured water 

level. The differences between the simulated and 

measured water levels in the Neenach, West Antelope, 

and Pearland subbasins were large because hydrologic 

data for these subbasins were limited. For wells in the 

Buttes and Finger Buttes subbasins, there were no 

water-level measurements available to calibrate the 

steady-state model.

Table 6. Measured and simulated (layer 1) water levels for wells used to calibrate the steady-state simulation of the ground-water flow model of the 

Antelope Valley ground-water basin, California

[State well No.: see well-numbering diagram; see figure 17 for location of wells; well depth in feet below land surface; water levels in feet above sea level; —

, no data]

1Number in parenthesis is the map number of the well as recorded by Thompson (1929, p. 348) 2Measured after 1915; Thompson (1929, p. 364) 3Flowing

State well No. Subbasin Well depth Year of 

measurement

Water levels Difference,

Measured feet Simulated

5N/11W-5D1 Pearland 403 1917 2,600 2,630 30

6N/11W-10D1 Lancaster 445 1915 2,430 2,434 4

7N/10W-5N2 Lancaster 404 1921 2,380 2,381 1

7N/10W-14R1 Lancaster — 1921 2,403 2,414 11

7N/10W-31A1 Lancaster 300 1921 2,421 2,424 3

7N/12W-21A1 Lancaster 301 1915 2,354 2,346 −8

7N/13W-11D5 Lancaster 351 1917 2,341 2,351 10

7N/13W-19A4 Lancaster 75 1908 2,368 2,367 −1

7N/13W-36D2 Lancaster 466 1914 2,368 2,356 −12

8N/10W-9 (162)1 Lancaster 25± 1921 2,303 2,308 5

8N/12W-22D1 Lancaster 371 1910 2,278 2,283 5

8N/13W-14Z1 Lancaster 200 1907 2,348 2,357 9

8N/14W-26Z1 Lancaster — 1909 2,376 2,382 6

8N/16W-6Q2 West Antelope 302 1909 2,824 2,847 23

8N/16W-10E1 Neenach — 1909 2,682 2,701 19

9N/9W-20 (6)1 Lancaster — 1917 2,2753 2,253 −22

9N/12W-21D4 Lancaster 89 1909 2,316 2,318 2

9N/13W-24B1 Lancaster 63 1908 2,359 2,353 −6

9N/13W-30D1 Neenach 62 1908 2,400 2,439 39

9N/14W-30K2 Neenach 255 1908 2,445 2,494 49

11N/9W-34 (3)1 North Muroc 260 —2 2,196 2,224 28
Simulation Of Ground-Water Flow 43

Figure 17. Areal distribution of natural recharge specified in the ground-water flow model of the Antelope Valley ground-water basin, California.

Wash

LANCASTER

118o30' Mojave

Boron

Rogers Lake

(dry)

Rosamond

Lake

(dry)

Buckhorn

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

Rock

Creek

Big

Creek

Rock

Little

Cottonwood

Amargosa

Fremont

Valley

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

COLUMN

ROW 1

1 10 20 30 50 60

1020

30

40

43

Quartz Hill

PEERLESS 40

34o30'

Palmdale

Littlerock

Lancaster

Rosamond

35o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

118o00'

Antelope Valley drainage

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope

Valley ground-waterbasin (modified fromCarlson and others, 1998)

EXPLANATION

Bedrock

Playa surface

Model cell

Model layer 1

0

0

10

10

20

20 Kilometers

Miles

250 to 500

1 to 250

1,500 to 5,000

Annual natural recharge, in

500 to 1,500

acre-feet—

EAFB

Main

Base
44 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Contours of measured and simulated layer 1 

water levels for 1915 are plotted together for 

comparison purposes on figure 16. Ground-water flow 

direction inferred from the contours of simulated water 

levels is similar to flow direction inferred from the 

1915 measured water-level contours. Ground-water 

flow is from recharge areas along the valley margins to 

discharge areas around the playas and the north 

boundary of the model. In the north Lancaster and 

North Muroc subbasins, the simulated water-level 

gradient to the north is less than the measured gradient. 

The largest differences between the measured and 

simulated water-level contours are in the Finger Buttes 

and Pearland subbasins: in these subbasins, the 

simulated water-level gradient is less than the 

measured gradient. The accuracy of the measured 1915 

water-level contours for these two subbasins, however, 

is uncertain owing to the lack of available water-level 

data.

Transient-State Simulation

Calibration of the transient-state model involved 

trial-and-error adjustments of horizontal hydraulic 

conductivity, transmissivity, vertical leakance, storage 

coefficient, hydraulic characteristic of barriers, 

preconsolidation head, and artificial recharge of 

irrigation-return flows. New values of vertical leakance 

were calculated during the calibration process to 

incorporate changes in the hydraulic conductivity and 

saturated thickness of layer 1 and the transmissivity of 

layers 2 and 3. Model parameters for the area north of 

Willow Springs Fault (barrier 7 on figure 11) were 

modified from values used in the Edwards Air Force 

Base ground-water flow and land subsidence model 

(Nishikawa and others, 2001).

The transient-state model was calibrated using 

available water-level data from 24 wells for the period 

1915–95 and subsidence data from 10 bench marks for 

the period 1926–92 (fig. 15). Data from 19 of the 24 

wells were used to compare measured and simulated 

water levels over time; the wells were selected on the 

basis of the length of water-level records and the spatial 

distribution of the wells. Data from two nested 

piezometer sites (wells 7N/12W-27F5–27F7 near 

Lancaster and wells 8N/10W-1Q1–1Q3 south of 

Rogers Lake) were used to compare the simulated and 

measured vertical hydraulic-head gradient between 

layers. The selection of the bench marks was based on 

the length of subsidence record and spatial distribution 

of the bench marks. The transient-state model was 

assumed to be calibrated when the simulated water 

levels matched the general magnitude and trend of the 

measured water levels, the general flow directions 

inferred from contours of the simulated water levels 

matched flow directions inferred from the contours of 

measured water levels, the onset and magnitude of land 

subsidence matched measured land subsidence, and the 

model parameters were within reasonable limits 

supported by the available geohydrologic data. 

The calibrated values of the horizontal hydraulic 

conductivities used for layer 1 ranged from 2 to 30 ft/d 

(fig. 18). Modifications were made to the initial values 

of horizontal hydraulic conductivity primarily for the 

areas southwest, south, and east of Rosamond Lake and 

for the Buttes subbasin. For these areas, few, if any, 

aquifer-test data were available to estimate the 

transmissive properties of the aquifer. In the area 

around Rosamond Lake, water levels that were 

simulated using the initial values of horizontal 

hydraulic conductivity were too low; therefore, the 

initial values were decreased to increase the simulated 

water levels. Lacustrine deposits are present in the 

upper aquifer in this part of the basin (fig. 3), which 

may explain the low simulated hydraulic conductivity 

values. In the southeast part of Buttes subbasin, the 

horizontal hydraulic conductivity was decreased from 

an initial value of 10 ft/d to a value of 2 ft/d. In the 

northwest part of the subbasin, horizontal hydraulic 

conductivity was increased from an initial value of 25 

to 30 ft/d in order to lower simulated water levels in the 

northwestern parts of the Buttes and Pearland 

subbasins.
Simulation Of Ground-Water Flow 45Figure 18. Areal distribution of (A) hydraulic conductivity for layer 1 and transmissivity for (B) layer 2 and (C) layer 3 in the ground-water flow model of the Antelope Valley ground-water basin, California.

Wash

A

WEST

ANTELOPE

118o30' Mojave

Boron

Rogers

Lake

(dry)

Rosamond Lake

(dry)

Buckhorn

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

Rock

Creek

Big

Creek

Rock

Little

Cottonwood

Amargosa

Fremont Valley

LANCASTER

COLUMN

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

Quartz Hill

PEERLESS

34o30'

Palmdale

Littlerock

Lancaster

Rosamond

35o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

0

0

10

10

20

20 Kilometers

Miles

118o00'

Hydraulic conductivity

(layer 1), in feet per day

2

5

10

15

24

30

AntelopeButtes

AlpineButtes

LovejoyButtes

Antelope Valley drainage

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope

Valley ground-waterbasin (modified fromCarlson and others, 1998)

EXPLANATION

Bedrock

Playa surface

Model layer 1

Model cell

EAFB

Main

Base
46 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 18.—Continued.

Wash

B

118o30' Mojave

Boron

Rogers

Lake

Rosamond

Lake

(dry)

Buckhorn

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

Rock

Creek

Big

Creek

Rock

Little

Cottonwood

Amargosa

Fremont Valley

(Dry)

LANCASTER

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

Quartz Hill

PEERLESS

34o30'

Palmdale

Littlerock

Lancaster

Rosamond

35o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

0

0

10

10

20

20 Kilometers

Miles

Transmissivity (layer 2),

in squared feet per day

118o00'

COLUMN

Model layer 2

EXPLANATION (Continued)

Less than 1,500

1,500 to 3,000

3,000 to 4,500

4,500 to 6,180

EAFB

Main

Base
Simulation Of Ground-Water Flow 47

Figure 18.—Continued.

C

118o30'

Rosamond

Lake

(dry)

Buckhorn

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

118o00'

LANCASTER

Rosamond

Fremont

Hills

COLUMN

ROW 1

1 10 20 30 40 50 60

102030

40

43

Tehachapi Mts

Biss

San Gabriel Mts

ell Hills Rosamond Hills

Transmissivity (layer 3),

in squared feet per day

EXPLANATION (Continued)

Palmdale

Quartz

Hill

Rogers Lake

(dry)

Mojave

Boron

0

0

10

10

20

20 Kilometers

Miles

PEERLESS

Creek

Cottonwood

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

34o30'

35o00'

Lancaster

Wash

Rock Big

Wash

Amargosa

Creek

Rock

Little

Model layer 3

Littlerock

Less than 200

200 to 500

500 to 800800 to 1,100

EAFB

Main

Base
48 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Transmissivity was specified for layers 2 and 3 in 

the model. Transmissivity was calculated outside the 

model using horizontal hydraulic conductivity and 

layer thickness. The horizontal hydraulic conductivity 

used to calculate the initial values of transmissivity for 

layer 2 was 10 ft/d. The thickness of layer 2 is 400 ft, 

except where the altitude of bedrock is higher than the 

1,550 ft above sea level. During the calibration process, 

the horizontal hydraulic conductivity of layer 2 was 

adjusted in some areas to represent a distribution of 

sediments, which, in most cases, are coarse near the 

mountain fronts and fine near the valley center. For the 

area surrounding Rosamond Lake and south nearly to 

the city of Lancaster, the horizontal hydraulic 

conductivity used to calculate transmissivity for layer 2 

was decreased to 2 ft/d. A transition zone having a 

horizontal hydraulic conductivity of 5 ft/d was 

specified between this area and the area to the south, 

which has a hydraulic conductivity of 10 ft/d. As 

required in layer 1, the horizontal hydraulic 

conductivity of layer 2 was decreased from 10 ft/d to 2 

ft/d for the Finger Buttes and West Antelope subbasins 

and the western part of the Neenach subbasin. The 

horizontal hydraulic conductivity around the city of 

Palmdale was decreased from 10 ft/d to 5 ft/d to 

simulate the measured water-level declines in this area. 

Transmissivity for the area around Edwards Air Force 

Base was calculated using a horizontal hydraulic 

conductivity of 15 ft/d (Nishikawa and others, 2001). 

The calibrated transmissivities of layer 2 (fig. 18B)

ranged from 11 to 6,000 ft2/d.

The transmissivity of layer 3 was calculated 

using a hydraulic conductivity of 2 ft/d. The thickness 

of layer 3 is 550 ft, except where the altitude of 

bedrock is greater than 1,000 ft above sea level. The 

transmissivities of layer 3 (fig. 18C) ranged from 24 to 

1,100 ft2/d and were not adjusted during the calibration 

process.

The vertical leakance between layers was 

calculated outside of the model using equation 2. The 

vertical hydraulic conductivity of a layer that contains 

lacustrine deposits was assumed equal to 1.0×10−2 ft/d. 

The vertical hydraulic conductivity of a layer that does 

not contain lacustrine deposits was assumed equal to 

one-hundredth of the horizontal hydraulic conductivity 

of that layer. Vertical-leakance values were recalculated 

to reflect changes in horizontal hydraulic conductivity, 

transmissivity, and saturated thickness. The final 

calibrated values for vertical leakance ranged from 

5.1×10−8 to 8.1×10−4 ft/d between layers 1 and 2 and 

from 7.1×10−6 to 1.04×10−4 ft/d between layers 2 and 3 

(fig. 19). Calibration of vertical leakance in the model 

was difficult because the vertical hydraulic-head 

gradient has been measured at only a few sites.

Barriers to horizontal ground-water flow, such as 

faults, simulated in the model are shown in figure 11

and the final calibrated hydraulic characteristic values 

are presented in table 5. The hydraulic characteristic 

value of most of the faults simulated in this model 

initially were based on results from previous groundwater flow models [barriers 1–4 (Durbin, 1978) and 

barriers 5–7 (Nishikawa and others, 2001)]. The initial 

hydraulic-characteristic values of the barriers were 

modified during the calibration process to obtain 

acceptable water-level differences across the barriers. 

The northwest-southeast trending barrier (8), southeast 

of Lovejoy Buttes, was added to the model because the 

simulated water levels for well 6N/9W-11N1 (fig. 15) 

were consistently too high in the absence of a partial 

barrier to flow. Additional data are needed to verify the 

existence, location, and extent of this barrier. Barrier 9 

(fig. 11) was added to the model to simulate the change 

in horizontal-flow characteristics where lacustrine 

deposits rise towards land surface and transect the 

upper and middle aquifers south of Rogers Lake (dry) 

(fig. 3). At this location, the lacustrine deposits may 

restrict the horizontal flow of ground water to areas of 

pumping to the south (Rewis, 1995, fig. 4). The delay 

and attenuated response, to pumpage, of water levels in 

well 8N/10W-8R3, located north of where the 

lacustrine deposits transect the upper and middle 

aquifers, compared to water levels in well 8N/11

W-34D2, located south of the lacustrine deposits, could 

not be simulated without simulating a partial barrier 

(barrier 9, fig. 11) to ground-water flow at this location.

Initial values of specific yield in layer 1 were 

adjusted for several parts of the study area during the 

calibration process. The specific-yield values specified 

for the Neenach subbasin (0.12), for some parts of the 

Lancaster subbasin (0.12), and for areas east and north 

of Rogers Lake (0.10) were decreased from initial 

values (0.15 to 0.20). The calibrated specific-yield 

value for the part of the Lancaster subbasin near 

Lancaster (0.12) is consistent with values estimated 

using coupled microgravity and water-level data (0.13) 

(Jim Howle, U.S. Geological Survey, written commun., 

2002). The specific-yield value specified for the area 

around Rosamond Lake (0.10) was increased from the 

initial value (0.05). The final distribution of specific 

yield (layer 1) is shown in figure 20.
Simulation Of Ground-Water Flow 49Figure 19. Areal distribution of vertical leakance between (A) layers 1 and 2 and (B) layers 2 and 3 in the ground-water flow model of the Antelope Valley ground-water basin, California.

A

118o30' Mojave

Boron

Rogers Lake

(dry)

Rosamond Lake

(dry)

Buckhorn

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

Rock Big

Wash

Amargasa

Creek

Rock

Little

LANCASTER

118o00'

Palmdale

Lancaster

Quartz Hill

Littlerock

Rosamond

Fremont

Valley

COLUMN

ROW 1

1 10 20 30 50 60

10

20

30

40

43

40

PEERLESS

Bissell Hills Rosamond Hills

Tehachapi Mts

San Gabriel Mts

0

0

10

10

20

20 Kilometers

Miles

Creek

Cottonwood

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

Antelope Valley drainage

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope

Valley ground-waterbasin (modified fromCarlson and others, 1998)

EXPLANATION

Bedrock

Playa surface

Model layer 2

Model cell

Less than 5

5 to 10

10 to 25

Greater than 25

Vertical leakance between

layers 1 and 2, x10 per day -5

35o00'

34o30'

EAFB

Main

Base
50 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 19.—Continued.

B

Rogers Lake

(dry)

Rosamond

Lake

(dry)

Buckhorn Lake

(dry)

Wash

Rock Big

Wash

Amargosa

Creek

Rock

Li

118

ttle

o00'

Fremont

Valley

COLUMN

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

Palmdale

Quartz Hill

Mojave

Boron

Lancaster

Littlerock

Rosamond

San Gabriel Mts

0

0

10

10

20

20 Kilometers

Miles

Creek

Cottonwood

34o30'

35o00'

118o30'

Tehachapi

Mts

San Gabriel Mts

Bissell Hills

Rosamond Hills

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

LANCASTER

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

PEERLESS

EXPLANATION (Continued)

Vertical leakance between

layers 2 and 3, x10 per day -5

Model layer 3

Less than 5

5 to 10

10 to 25

EAFB

Main

Base
Simulation Of Ground-Water Flow 51 Figure 20. Areal distribution of specific yield in layer 1 of the ground-water flow model in the Antelope Valley ground-water basin, California.

Wash

118o30' Mojave

Boron

Rogers

Lake

(dry)

Rosamond

Lake

(dry)

Buckhorn

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

Rock

Creek

Big

Creek

Rock

Little

Cottonwood

Amargosa

118o00'

LANCASTER

Fremont

Valley

COLUMN

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

Quartz Hill

PEERLESS

34o30'

Palmdale

Littlerock

Lancaster

Rosamond

35o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts Specific yield (layer 1)

0.10

0.120.14

San Gabriel Mts

0

10

10 20 Kilometers

Miles 0 20

LovejoyButtes

Little

Buttes

AntelopeButtes

Antelope Valley drainage

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope

Valley ground-waterbasin (modified fromCarlson and others, 1998)

EXPLANATION

Bedrock

Playa surface

Model Layer 1

Model cell

EAFB

Main

Base
52 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

The initial storage coefficients representing the 

compressibility of water and elastic skeletal storage 

were not changed during the calibration process. The 

storage coefficient representing the compressibility of 

water ranged from 0.3×10−4 to 5.1×10−4 in layer 1 

(fig. 21A) and from 0.1×10−4 to 1.7×10−4 in layer 2 

(fig. 21B), depending upon the thickness of saturated 

sediments in these layers. The elastic skeletal storage 

coefficient ranged from 1.0×10−4 to 2.07×10−3 in layer 

1 (fig. 22A) and from 1.2×10−5 to 6.8×10−4 in layer 2 

(fig. 22B). The final inelastic storage coefficient was 

calculated using an inelastic skeletal specific storage of 

1.6×10−4 ft−1, which is between the inelastic skeletal 

specific storage values for thick aquitards 

(3.5×10−4 ft−1) and thin aquitards (4.0×10−5 ft−1) 

reported by Sneed and Galloway (2000). The inelastic 

skeletal storage coefficient ranged from 2.9×10−3 to 

3.11×10−2 in layer 1 (fig. 23A) and from 3.2×10−5 to 

2.88×10−2 in layer 2 (fig. 23B). An inelastic skeletal 

storage coefficient was not specified for areas where 

subsidence has not been measured historically.

Calibrated preconsolidation head ranged from 0 

to 160 ft below steady-state water levels in the area 

where subsidence was simulated (fig. 24). The 

preconsolidation head was adjusted until the timing of 

the onset of simulated subsidence matched measured 

subsidence. The variability in the calibrated 

preconsolidation head can be attributed to 

overconsolidation of the alluvium. Overconsolidlation 

of an alluvial basin can be caused by removal of 

overburden by erosion, prehistoric ground-water level 

declines, desiccation, and diagenesis (Holzer, 1981).

Irrigation-return flows were simulated as 30 

percent of the annual quantity of water applied for 

agricultural irrigation. During the transient-state 

calibration process it was determined that irrigationreturn flows recharged the underlying aquifer 10 years 

after the water was applied for irrigation. The 

calibrated delay between the application of irrigation 

water and the recharge of the irrigation-return flows 

was supported by the results of a simple unsaturatedzone model completed for this study using 

representative soil properties and depth to water 

measurements (Alan Flint, U.S. Geological Survey, 

written commun., 1999). Irrigation-return flows were 

applied directly to the model cells where agricultural 

pumping was simulated. In addition, irrigation-return 

flows were applied to the model cells where imported 

water was used for irrigation (fig. 12). 

Model Results

Water Levels

Water-level hydrographs for 19 wells were used 

to compare simulated and measured water levels over 

time (fig. 25) (well locations shown on figure 15). The 

measured water levels for two wells (8N/10W-1Q3 and 

8N/10W-4E1) were combined into one hydrograph to 

form a more complete period of record. The simulated 

water levels generally matched the trends of the 

measured water levels but did not always match the 

magnitude. 

Twelve of the hydrographs compared simulated 

and measured water levels in the Lancaster subbasin. In 

general, the simulated water levels matched the 

measured water declines of more than 300 ft, which 

began in the 1920s, soon after pumpage exceeded 

estimates of natural recharge. In the southern part of 

the Lancaster subbasin (wells 6N/11W-19E6 and 

7N/11W-31M1), the simulated water levels were more 

than 20 ft higher than the measured water levels after 

about 1970. In the western part of the Lancaster 

subbasin, east of Antelope Buttes (wells 7N/14W13A1, 8N/13W-35M1, and 8N/14W-23G1), the 

simulated water levels generally were about 30 ft lower 

than the measured water levels. In the northeastern part 

of the Lancaster subbasin, the simulated water level in 

layer 3 at well 8N/10W-8R3 was about 20 ft lower than 

the measured water level after the late-1950s. 
Simulation Of Ground-Water Flow 53 Figure 21. Areal distribution of the storage coefficient representing the compressibility of water for (A) layer 1 and (B) layer 2 in the ground-water flow model of the Antelope Valley ground-water 

basin, California.

Wash

Rogers

Lake

(dry)

Rosamond

Lake

(dry)

Buckhorn

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

Rock

Creek

Big

Creek

Rock

Little

Cottonwood

Amargosa

LANCASTER

Fremont

Valley

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

PEERLESS

34o30'

35o00'

118o30'

118o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts Storage coefficient represent- ing the compressibility of water in layer 1, x10

0.1 to 1.5

1.5 to 2.5

2.5 to 3.5

3.5 to 4.5

4.5 to 5.1

-4

San Gabriel Mts

0

0

10

10

20

20 Kilometers

Miles

Antelope Valley drainage

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

EXPLANATION

BedrockPlaya surface

Model layer 1

Model cell

Mojave

Boron

Palmdale

Littlerock

Lancaster

Quartz Hill

COLUMN

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

A

EAFB

Main

Base
54 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 21.—Continued.

Wash

B

118o30' Mojave

Boron

Rogers Lake

(dry)

Rosamond

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

Rock

Creek

Big

Creek

Rock

Little

Cottonwood

Amargosa

118o00'

Fremont

Valley

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

COLUMN

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

Quartz Hill

PEERLESS

Model layer 2

LANCASTER

34o30'

Palmdale

Littlerock

Lancaster

Rosamond

35o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

EXPLANATION (Continued)

0.1 to 1.5

1.5 to 2.5

San Gabriel Mts

0

0

10

10

20

20 Kilometers

Miles

Storage coefficient representing the compressibility of

water in layer 2, x10-4

EAFB

Main

Base
Simulation Of Ground-Water Flow 55Figure 22. Areal distribution of the elastic skeletal storage coefficient for (A) layer 1 and (B) layer 2 in the ground-water flow model of the Antelope Valley ground-water basin, California.

A

118o30' Mojave

Boron

Rogers

Lake

(dry)

Rosamond

Lake

(dry) Buckhorn

Lake

(dry)

118o00' COLUMN

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

Quartz Hill

Wash

34 o30'

Fremont

Valley

Palmdale

Littlerock

Lancaster

Bissell Hills

Rosamond Hills

Tehachapi Mts

Wash

Rock

Creek

Big

Creek

Rock

Little

Cottonwood

Amargosa

San Gabriel Mts

0

0

10

10

20

20 Kilometers

Miles

AlpineButtes

LovejoyButtes

Little

Buttes

AntelopeButtes

PEERLESS

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

LANCASTER

Antelope Valley drainage

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope Valley

ground-water basin (modifiedfrom Carlson and others, 1998)

EXPLANATION

Bedrock

Playa surface

Model layer 1

Model cell

1.0 to 4.0

4.0 to 8.0

8.0 to 12.0

12.0 to 16.0

16.0 to 20.7

Elastic skeletal storagecoefficient in layer 1, x10-4

35o00'

Rosamond

EAFB

Main

Base
56 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 22.—Continued.

Wash

B

118o30' Mojave

Boron

Rogers Lake

(dry)

Rosamond

Lake

(dry) Buckhorn

Lake

(dry)

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

Rock

Creek

Big

Creek

Rock

Little

Cottonwood

Amargosa

118o00'

LANCASTER

Fremont

Valley

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

COLUMN

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

Quartz Hill

PEERLESS

34o30'

Palmdale

Littlerock

Lancaster

Rosamond

35o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

EXPLANATION (Continued)

Elastic skeletal storagecoefficient in layer 2, x10 -4

0

0

10

10

20

20 Kilometers

Miles

0.12 to 4.0

4.0 to 6.8

Model layer 2

EAFB

Main

Base
Simulation Of Ground-Water Flow 57 Figure 23. Areal distribution of the inelastic skeletal storage coefficient for (A) layer 1 and (B) layer 2 in the ground-water flow model of the Antelope Valley ground-water basin, California.

A

118o30' Mojave

Boron

Rogers

Lake

(dry)

Rosamond

Lake

(dry)

Buckhorn

Lake

(dry)

118o00'

Fremont

Valley

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

PEERLESS

34o30'

Palmdale

Rosamond

35o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

00

10

10

20

20 Kilometers

Miles

Littlerock

Quartz Hill

Lancaster

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

Inelastic skeletal storage

coefficient in layer 1, x10-3

2.9 to 6.0

6.0 to 12.0

Antelope Valley drainage

12.0 to 18.0

18.0 to 24.0

24.0 to 31.1

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope

Valley ground-waterbasin (modified fromCarlson and others, 1998)

EXPLANATION

Bedrock

Playa surface

Model cell

Model layer 1

Wash

Rock

Creek

Big

Creek

Rock

Cottonwood

Amargosa

Wash

Little

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

LANCASTER

COLUMN

EAFB

Main

Base
58 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 23.—Continued.

B

118o30' Mojave

Boron

Rogers Lake

(dry)

Rosamond

Lake

(dry)

Buckhorn

Lake

(dry)

118o00'

LANCASTER

Fremont

Valley

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes

COLUMN

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

Quartz Hill

34o30'

Palmdale

Littlerock

Lancaster

Rosamond

35o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

EXPLANATION (Continued)

Inelastic skeletal storage

coefficient in layer 2, x10-3

12.0 to 18.0

0.03 to 6.0

6.0 to 12.0

18.0 to 24.0

24.0 to 28.8

San Gabriel Mts

0

0

10

10

20

20 Kilometers

Miles

Model layer 2

PEERLESS

NORTH MUROC

OAK CREEK

NEENACH

FINGER

BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

Wash

Rock

Creek

Big

Creek

Rock

Cottonwood

Amargosa

Wash

Little

EAFB

Main

Base
Simulation Of Ground-Water Flow 59 Figure 24. Difference between steady-state water levels and preconsolidation head in the ground-water flow model of the Antelope Valley ground-water basin, California.

118o30' Mojave

Boron

Rogers

Lake

(dry)

Rosamond

Lake

(dry)

Buckhorn

Lake

(dry)

118 00'

Fremont

Valley

ROW 1

1 10 20 30 40 50 60

1020

30

40

43

PEERLESS

Lancaster

Palmdale

35o00'

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

00

10

10

20

20 Kilometers

Miles

Quartz Hill

Littlerock

Little

Buttes

AntelopeButtes

AlpineButtes

LovejoyButtes Antelope Valley drainage

basin

Subbasin (modified from

Bloyd,1967)

Boundaries—

Study area—Antelope

Valley ground-waterbasin (modified fromCarlson and others, 1998)

EXPLANATION

Bedrock

Playa surface

Model cell

Model layer 1

Wash

Rock

Creek

Big

Creek

Rock

Cottonwood

Amargosa

Wash

Little

Rosamond

Difference between steadystate water levels and preconsolidation head

0

Unknown

10

50

85

125

160

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST

ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

PEARLAND

CHAFFEE

LANCASTER

COLUMN

34o30'

EAFB

Main

Base
60 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 25. Measured and simulated water levels at selected wells in the Antelope Valley ground-water basin, California, 1915–95. (See figure 15 for 

location of wells.)

2,500

2,600

2,700

2,800

2,900

5N/10W-6N1

Depth—304 feet

Perforations unknown

2,300

2,400

2,500

2,600

2,700

6N/9W-11N1

Depth—295 feet

Perforations unknown

2,000

2,100

2,200

2,300

2,400

2,500

6N/11W-19E6

Depth—848 feet

Perforations—398–848 feet

2,100

2,200

2,300

2,400

2,500

7N/10W-33J1

Depth—415 feet

Perforations unknown

1915 1935 1955 1975 1995

YEAR

2,100

2,200

2,300

2,400

2,500

7N/11W-31M1

Depth—386 feet

Perforations unknown

1915 1935 1955 1975 1995

2,400

2,500

2,600

2,700

2,800

6N/10W-34D1

Depth—300 feet

Perforations unknown

WATER LEVEL, IN FEET ABOVE SEA LEVEL

EXPLANATION

Pearland subbasin

Buttes subbasin

Buttes subbasin

Lancaster subbasin

Lancaster subbasin

Lancaster subbasin

Land surface—2,777 feet above sea level

Land surface—2,586 feet above sea level

Land surface—2,538 feet above sea level

Land surface—2,468 feet above sea level

Land surface—2,666 feet above sea level

Land surface—2,706 feet above sea level

Simulated layer 1

Simulated layer 2

Simulated layer 3

Measured
Simulation Of Ground-Water Flow 61

Figure 25.—Continued.

1915 1935 1955 1975 1995

YEAR

1915 1935 1955 1975 1995

WATER LEVEL, IN FEET ABOVE SEA LEVEL

EXPLANATION

Lancaster subbasin

Simulated layer 1

Simulated layer 2

Simulated layer 3

Measured

2,000

2,100

2,200

2,300

2,400

8N/13W-9K1

Depth unknown

Perforations unknown

Land surface—2,412 feet above sea level

4E1 1Q3

Lancaster subbasin

Lancaster subbasin

7N/14W-13A1

Depth—519 feet

Perforations—249–519 feet

Land surface—2,467 feet above sea level

2,000

2,100

2,200

2,300

2,400

2,000

2,100

2,200

2,300

2,400

7N/12W-19R1

Depth—400 feet

Perforations—100–400 feet

Land surface—2,386 feet above sea level

Lancaster subbasin

2,000

2,100

2,200

2,300

2,400

8N/10W-1Q3

Depth—475 feet

Perforations—430–460 feet

8N/10W-4E1

Depth—129 feet

Perforations unknown

Land surface—2,301 feet above sea level

Land surface—2,300 feet above sea level

2,000

2,100

2,200

2,300

2,400

8N/10W-8R3

Depth—238 feet

Perforations unknown

Lancaster subbasin

Land surface—2,318 feet above sea level

2,000

2,100

2,200

2,300

2,400

8N/11W-34D2

Depth—250 feet

Perforations unknown

Lancaster subbasin

Land surface—2,340 feet above sea level
62 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 25.—Continued.

YEAR

1915 1935 1955 1975 1995

EXPLANATION

Simulated layer 1

Simulated layer 2

Simulated layer 3

Measured

2,000

2,100

2,200

2,300

2,400 Lancaster subbasin

8N/13W-35M1

Depth—255 feet

Perforations unknown

Land surface—2,354 feet above sea level

1915 1935 1955 1975 1995

WATER LEVEL, IN FEET ABOVE SEA LEVEL

2,000

2,100

2,200

2,300

2,400

11N/9W-36R1

Depth—254 feet

Perforations—100–132 feet

Land surface—2,311 feet above sea level

8N/17W-1N1

Depth—787 feet

Perforations unknown

Land surface—2,955 feet above sea level

Land surface—2,656 feet above sea level

Lancaster subbasin

2,100

2,200

2,300

2,400

2,500

2,500

2,600

2,700

2,800

2,900 Lancaster subbasin West Antelope subbasin

9N/9W-10R1

Depth—98 feet

Perforations unknown

Land surface—2,281 feet above sea level

8N/14W-23G1

Depth—420 feet

Perforations unknown

Land surface—2,500 feet above sea level

9N/14W-20B1

Depth— 540 feet

Perforations—290–540 feet

Neenach subbasin

North Muroc subbasin

2,000

2,100

2,200

2,300

2,400

2,200

2,300

2,400

2,500

2,600
Simulation Of Ground-Water Flow 63

In the Buttes subbasin (wells 6N/9W-11N1 and 

6N/10W-34D1), measured and simulated water levels 

matched well. In the Pearland subbasin (well 

5N/10W-6N1), the simulated water levels were higher 

than the measured water levels prior to the 1970s and 

were lower than the measured water levels after the 

1970s. The simulated water level was about 24 ft lower 

than the measured water level by the end of the 

simulation period. In the West Antelope subbasin 

(well 8N/17W-1N1), the simulated water levels 

matched the measured water levels well through the 

1970s, but the simulated water level overestimated the 

measured water-level rise that occurred from the mid 

1970s to 1995 by as much as 65 ft. Because there are 

virtually no data for this subbasin in the pumpage 

database, the estimated quantity and distribution of 

annual pumpage were based only on 1961 land-use 

data. In addition to the lack of pumpage data for the 

West Antelope subbasin, there are uncertainties in the 

estimates of the quantity and distribution of recharge 

from irrigation-return flows of water delivered by the 

AVEK Water Agency. It was assumed that water 

delivered by the AVEK Water Agency was applied to 

fields near the area where the water was discharged 

from the aqueduct. In the Neenach subbasin (well 

9N/14W-20B1) and the North Muroc subbasin (well 

11N/19W-36R1), the simulated and measured water 

levels matched well.

The simulated water-level gradient between 

model layers at the end of the model simulation (1995) 

was compared with the measured February 1996 waterlevel gradient at nested piezometers 7N/12W-27F5

–27F7 in the southern part of the Lancaster subbasin 

and the measured October 1995 water-level gradient at 

nested piezometers 8N/10W-1Q1-3 in the northeastern 

part of the Lancaster subbasin (table 7). In the southern 

Lancaster subbasin, the measured data indicated that 

there was an upward water-level gradient, with the 

largest water-level difference (14 ft) between the 

middle and lower aquifers (layers 2 and 3). The 

lacustrine deposits separate the middle and lower 

aquifers in this part of the subbasin (fig. 3).The model 

simulated an upward water-level gradient at this site, 

but the simulated water-level difference between layers 

2 and 3 was 11 ft, about 3 ft less than measured waterlevel difference. In the northeastern Lancaster 

subbasin, the measured data indicated that there was a 

small downward water-level gradient; the difference 

between measured water levels for wells 8N/10W

-1Q1–1Q3 was 1–2 ft (table 7). Simulated water levels 

for the three layers were within 1 ft of each other at this 

site, indicating little or no vertical ground-water 

movement at this site. The lacustrine deposits are near 

land surface in this area (Londquist and others, 1993); 

these three wells are all perforated below the lacustrine 

deposits.

Table 7. Measured and simulated water levels at two sites with nested piezometers completed at multiple depths in the Lancaster subbasin of the 

Antelope Valley ground-water basin, California.

[State well No.: See well-numbering in text]

1 Above the lacustrine clay.

2 Below the lacustrine clay.

Layer

Wells 7N/12W-27F5–7

Land surface altitude: 

2,443 feet above sea level

Wells 8N/10W-1Q1–3

Land surface altitude: 

2,301 feet above sea level

State 

well No. 

of nested 

piezometer

Perforated

interval, 

in feet 

below land

surface

Measured 

water level, 

February 1996, 

in feet 

above sea level

Simulated 

water level, 1995, 

in feet 

above sea level

State 

well No.

of nested 

piezometer

Perforated

interval, 

in feet 

below land 

surface

Measured 

water level, 

October 1995, 

in feet above 

sea level

Simulated 

water level, 1995, 

in feet above 

sea level

1 127F7 505–525 2,138 2,156 21Q3 430–460 2,154 2,159

2 127F6 705–725 2,139 2,161 21Q2 605–635 2,153 2,159

3 227F5 905–925 2,153 2,172 21Q1 980–1,010 2,152 2,160
64 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Contours of simulated 1995 and measured 1996 

(Carlson and others, 1998) water levels for layer 1 are 

shown in figure 26. The measured 1996 water-level 

contours were assumed to be representative of 1995 

conditions and were used to qualitatively evaluate the 

transient-state simulation. The model does a good job 

of simulating the observed pumping depression near 

Lancaster and Palmdale, an area of recent extensive 

pumping for public supply. However, the simulated 

water levels were lower than measured water levels in 

the eastern and western parts of the Lancaster subbasin. 

These areas historically were subject to large amounts 

of agricultural pumping, which was not metered and 

therefore difficult to estimate. The simulated flat waterlevel gradient in the northern part of the Lancaster 

subbasin and the North Muroc subbasin matched the 

measured water-level gradient in these areas. The 

simulated water levels matched the measured water 

levels throughout most of the Neenach subbasin except 

in the western part of the subbasin. The simulated and 

measured water levels matched well in much of the 

Buttes and Pearland subbasins even though the 

hydrogeologic and agricultural pumpage data for these 

subbasins were limited. Because of insufficient waterlevel data for the Finger Buttes, West Antelope, and 

parts of the Buttes and Pearland subbasins, 

comparisons could not be made for these subbasins.

Land Subsidence 

Simulated land subsidence was compared with 

periodic surveyed (measured) data collected at 10 

bench marks (locations shown in figure 15) since about 

1930 (fig 27). Simulated land subsidence is the sum of 

aquifer-system compaction in layers 1 and 2. Recall, 

compaction was assumed to be minimal in layer 3, and 

was not simulated in the model. Pumping-induced 

subsidence is controlled by the thickness of 

compressible sediments, preconsolidation head, and 

water-level declines. Where simulated water-level 

declines are greater than actual water-level declines or 

where the aquifer contains a smaller thickness of 

compressible sediments than was represented in the 

model, simulated subsidence will be larger than 

measured subsidence. Simulated subsidence will be 

smaller than measured subsidence where simulated 

water-level declines are less than actual water-level 

declines or where the aquifer contains a larger 

thickness of compressible sediments than was 

represented in the model. The MODFLOW package, 

IBS1, simulates an instantaneous release of water from 

the compressible interbeds (aquitards) and thus 

subsidence—and does not account for hydrodynamic 

lag or residual compaction. This limitation is further 

discussed in the “Limitations of the Model” section of 

this report.

Simulated subsidence closely matched measured 

subsidence at all of the10 bench marks (fig. 27). 

Simulated subsidence began at most locations in the 

1930s, but as early as 1928 at bench mark BM 479 and 

as late as 1950 at bench mark BM 474. Simulated 

subsidence was greatest (6.3 ft) at bench mark BM 474 

near Lancaster; the maximum measured subsidence 

also was at this bench mark (Ikehara and Phillips, 

1994). Large water-level declines have occurred near 

bench mark BM 474, and the aquifer contains a 

substantial thickness of compressible sediments. 

Simulated subsidence was lowest at bench marks BM 

2317 (2.0 ft) and BM 823 (2.17 ft). These two sites are 

located in areas that historically have been subjected to 

large amounts of pumpage, but the aquifers in the area 

contain fewer compressible sediments than aquifers in 

areas that had greater subsidence. Simulated 

subsidence also was small at bench mark BM 483 

(2.2 ft) even though the aquifer in this area consists of a 

thick layer of compressible sediments. However, there 

has been minimal pumping and associated water-level 

declines in this area. The abrupt increase in simulated 

subsidence at bench marks BM 474, BM 2180, and 

BM 2317 in about 1977 corresponds to the increase in 

pumpage for public supply in 1977 (fig. A2) from the 

aquifer near these benchmarks.

Although water levels have declined more than 

200 ft throughout much of the study area, subsidence 

greater than 1 ft has been documented only in the 

central part of the study area (fig. 8). In the area around 

Palmdale where water-level declines have been large, 

no measurable subsidence has occurred (Ikehara and 

Phillips, 1994). This lack of measurable subsidence 

suggests that this area may not be susceptible to 

subsidence even though lacustrine deposits have been 

mapped in this area (fig 3). However, it is possible that 

water levels may not yet have declined below the 

preconsolidation head in areas where subsidence has 

not occurred. Subsidence can be simulated in the 

model only where inelastic storage is specified; 

inelastic storage was specified only for areas where 

measurements have shown that subsidence has 

occurred. 
Simulation Of Ground-Water Flow 65Figure 26. Measured (1996) and simulated (1995) water levels from the ground-water flow model of the Antelope Valley ground-water basin, California.

Wash

Mojave

Boron

Rogers Lake

(dry)

Rosamond

Lake

(dry)

Buckhorn

Lake

(dry)

Big

Fremont

Valley

Wash

Rock

Creek

Creek

Rock Little

Cottonwood

Amargosa

LANCASTER

COLUMN

WOR 1

1 10 20 30 40 50 60

1020

30

40

43

Quartz Hill

Palmdale

Littlerock

Rosamond

Lancaster

Bissell Hills

Rosamond Hills

Tehachapi Mts

San Gabriel Mts

00

10

10

20

20 Kilometers

Miles

PEARLAND

2,400

Line of equal water-level altitude—

Interval variable, in feet. Datum issea level

3 0, 00

29, 00

2 8, 00

, 2 07 0 2 6, 00

2 6, 00

2,500

2 5, 00

2 4, 00

2 4, 00

2 3, 00

2 3, 00

2 1, 75

2 2, 00

2,200

22, 25 , 2 52 0 , 2 72 5

22, 25

2, 2 05

2 2, 25

2,200

2 2, 25

2 2, 50

2,150

2 1, 75

2,200 2,175

2,220

2,400

2 6, 00

2 900 ,

2,800 3, 2 00

3, 2 00

Alpine Buttes

Fault—Dashed where

inferred (modified fromDibblee, 1963; Ward andothers, 1993; Nishikawaand others, 2001)

2 2, 25

2 7, 00

2,500

3 1, 00

3,000

32, 00

2,175

2,200

008, 2

2,900

2 8, 00

2 7, 00

2 7, 00

2 6, 00

2 5, 00

28, 00

2 2, 00

009, 1

0, 2 00

01, 2 0

2,150

2,275

2,225

2, 2 57

2,600

Lovejoy Buttes

Little

Buttes

Antelope Buttes

118o30'

34o30'

35o00'

2,175

2,400

2,500

2,600

2,800

2,700

2,600

2,500

2,400

2,400

2,300 2,300

2,200

2,200

2,200

2,250

2,250

2,250 2,250

2,250

2,225

2,225

2,225

2,150

2,050

2,175

2,175

2,3002,400

2,400

2,500

2,500

2,600

700 2,

2,700

2,800

2,800

2,225

2,400

2,500

PEERLESS

NORTH MUROC

OAK CREEK

NEENACH

FINGER BUTTES

WEST ANTELOPE

WILLOW

SPRINGS

GLOSTER

BUTTES

CHAFFEE

2,100

Antelope Valley drainage basin

Subbasin (modified from Bloyd,1967)

Boundaries—

Study area—Antelope Valley groundEXPLANATION

water basin (modified from Carlsonand others, 1998)

Model cell

Measured (1996)—(modified from

Carlson and others, 1998)

Simulated (1995)—(transient-state

simulation)

Bedrock

Playa surface

Model layer 1

2,225

118o00'

EAFB

Main

Base
66 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 27. Measured and simulated total land subsidence at selected bench marks in the Antelope Valley ground-water basin, California, 1915–95. (See 

figure 15 for location of bench marks.)

1915 1935 1955 1975 1995

YEAR

BM 2317

1915 1935 1955 1975 1995

7

6

5

4

3

2

1

0

BM 823

7

6

5

4

3

2

1 BM 479

7

6

5

4

3

2

1 BM 474

BM 2180

BM 1159

BM 2169

7

6

5

4

3

2

1 BM 537

BM 1469

7

6

5

4

3

2

1

0

0

0

0

BM 483

TOTAL LAND SUBSIDENCE, IN FEET

Simulated

Measured
Simulation Of Ground-Water Flow 67

Because of the limitations of the IBS1 Package 

in the simulation of subsidence, a match between 

simulated and measured subsidence does not 

necessarily indicate that the parameters controlling 

subsidence are accurately represented by the model. 

The IBS1 Package simulates subsidence 

instantaneously after a decline in hydraulic head below 

the preconsolidation head; therefore, there is no time 

delay in the simulated subsidence to account for the 

delayed equilibration of hydraulic heads in the thick 

aquitards. Results from the one-dimensional model 

developed by Sneed and Galloway (2000) and from a 

comparison of paired water-level and subsidence data 

(Ikehara and Phillips, 1994) (fig. 9) indicate that the 

delayed drainage of the thick aquitards is an important 

process in the occurrence of subsidence in Antelope 

Valley. Therefore, the model developed for this study 

may simulate subsidence before it actually occurs, 

owing to hydrodynamic lag and residual compaction 

and land subsidence. Additionally, simulated 

subsidence is dependent on simulated drawdown. If 

simulated drawdown does not match actual drawdown, 

then simulated subsidence would not be expected to 

match measured subsidence.

Water Budget

The simulated annual volumes of recharge, 

discharge, and change in storage for Antelope Valley 

ground-water basin are shown in table 8. Graphs of the 

simulated recharge and discharge components are 

shown in figure 28 and a graph of simulated cumulative 

change in storage for the entire simulation period is 

shown in figure 29. Results of the transient-state 

simulation indicate that more than 8.5 million acre-ft of 

ground water was removed from storage during 1915–

95, with most of the storage change occurring between 

about 1945 and 1975. Ground-water storage changed 

little during the final 10 years of simulation period 

because discharge by pumpage had declined 

sufficiently to be balanced by recharge (fig. 28C). 

Water-budget components for the steady-state 

simulation and for the 1949–53 and 1991–95 periods of 

the transient-state simulation are shown in figure 30. 

The period 1949–53 was selected to represent 

hydrologic conditions when agricultural production 

and associated pumping were at a maximum. The 

period 1991–95 was selected to represent conditions 

when pumping for public supply was at a maximum 

and pumping for agricultural production was at a recent 

minimum. All components of recharge and the 

pumpage component of discharge were specified as 

model input parameters. Evapotranspiration, groundwater underflow, flow between model layers, and 

changes in aquifer and aquitard storage were simulated 

by the model.

Under steady-state conditions, recharge from 

natural sources was balanced by discharge as 

evapotranspiration and ground-water underflow from 

the North Muroc subbasin into Fremont Valley, and 

there were no changes in aquifer storage. The 

simulated ground-water underflow into Fremont Valley 

(400 acre-ft/yr) was less than half the amount estimated 

by Durbin (1978) (1,000 acre-ft/yr). Flow northward 

across the Willow Springs Fault, southeast of Rogers 

Lake (barrier 7, fig. 11), was equal to the ground-water 

underflow out of the basin. The model simulated that 

evapotranspiration averaged 29,900 acre-ft/yr; all of 

the evapotranspiration simulated by the model occurred 

in the area of alkali soils (fig. 4) south of barrier 7. 

During the 1949–53 period, pumpage reached a 

maximum of 363,000 acre-ft/yr and recharge averaged 

77,800 acre-ft/yr (fig. 30). Model results indicate that 

79 percent of the ground-water pumpage was 

contributed from aquifer storage (71 percent or 

265,100 acre-ft/yr) and aquitard storage (8 percent or 

21,600 acre-ft/yr); of that, more than 95 percent 

(263,000 acre-ft/yr) came from storage in layer 1. 

Leakage from layer 1 into layer 2 accounted for 

86 percent of the ground-water pumpage from layer 2. 

Recharge from irrigation-return flows was 47,500 acreft/yr; about 13 percent of the ground-water pumpage 

(fig. 30). As a result of water-level declines (fig.25), 

evapotranspiration was only 1,200 acre-ft/yr, about 4 

percent compared to steady-state conditions. 
68 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California Table 8. Simulated recharge, discharge, and change in storage for the Antelope Valley ground-water basin, California, 1915–95 [AVEK, Antelope Valley–East Kern Water Agency; evapotranspiration and ground-water underflow are model computed values; all other values are model inputs; units in thousand acre-feet; positive numbers represent water added to the system, and negative numbers represent water removed from the system] Recharge Discharge Total Change in storage Irrigation-return flows Pumpage Natural

Year Pumpage

AVEK 

deliveries Natural

Wastewater Public supply Agriculture Total Evapotran- spiration Ground-water underflow Recharge Discharge Annual Cumulative

1915 0.0 0.0 30.3 0.0 0.0 0.0 0.0 −30.0 −0.4 30.3 −30.4 −0.1 −0.11916 .0 .0 30.3 .0 .0 −1.9 −1.9 −29.8 −.4 30.3 −32.1 −1.8 −1.91917 .0 .0 30.3 .0 .0 −5.8 −5.8 −29.5 −.4 30.3 −35.7 −5.4 −7.31918 .0 .0 30.3 .0 .0 −10.7 −10.7 −28.9 −.4 30.3 −40.0 −9.7 −17.01919 .0 .0 30.3 .0 .0 −15.5 −15.5 −28.1 −.4 30.3 −44.0 −13.7 −30.71920 .0 .0 30.3 .0 .0 −22.3 −22.3 −27.1 −.4 30.3 −49.8 −19.5 −50.21921 .0 .0 30.3 .0 .0 −29.1 −29.1 −25.8 −.4 30.3 −55.3 −25.0 −75.21922 .0 .0 30.3 .0 .0 −35.9 −35.9 −24.4 −.4 30.3 −60.7 −30.4 −105.61923 .0 .0 30.3 .0 .0 −40.7 −40.7 −23.0 −.4 30.3 −64.1 −33.8 −139.41924 .0 .0 30.3 .0 .0 −50.4 −50.4 −21.4 −.4 30.3 −72.2 −41.9 −181.31925 .0 .0 30.3 .0 .0 −64.0 −64.0 −19.7 −.4 30.3 −84.1 −53.8 −235.11926 .6 .0 30.3 .0 .0 −81.4 −81.4 −17.8 −.4 30.9 −99.6 −68.7 −303.81927 1.7 .0 30.3 .0 .0 −98.9 −98.9 −15.8 −.4 32.0 −115.1 −83.1 −386.91928 3.2 .0 30.3 .0 .0 −125.1 −125.1 −13.7 −.4 33.5 −139.2 −105.7 −492.61929 4.7 .0 30.3 .0 .0 −157.1 −157.1 −11.6 −.4 35.0 −169.1 −134.1 −626.71930 6.7 .0 30.3 .0 .0 −166.8 −166.8 −9.8 −.4 37.0 −177.0 −140.0 −766.71931 8.7 .0 30.3 .0 .0 −145.4 −145.4 −8.6 −.4 39.0 −154.4 −115.4 −882.11932 10.8 .0 30.3 .0 .0 −108.6 −108.6 −7.8 −.4 41.1 −116.8 −75.7 −957.81933 12.2 .0 30.3 .0 .0 −99.9 −99.9 −7.3 −.4 42.5 −107.6 −65.1 −1,022.91934 15.1 .0 30.3 .0 .0 −111.8 −111.8 −6.7 −.4 45.4 −118.9 −73.5 −1,096.41935 19.2 .0 30.3 .0 .0 −119.1 −119.1 −6.2 −.4 49.5 −125.7 −76.2 −1,172.61936 24.4 .0 30.3 .0 .0 −124.3 −124.3 −5.7 −.4 54.7 −130.4 −75.7 −1,248.31937 29.7 .0 30.3 .0 .0 −132.5 −132.5 −5.3 −.4 60.0 −138.2 −78.2 −1,326.51938 37.5 .0 30.3 .0 .0 −136.7 −136.7 −4.9 −.4 67.8 −142.0 −74.2 −1,400.71939 47.1 .0 30.3 .0 .0 −143.9 −143.9 −4.6 −.4 77.4 −148.9 −71.5 −1,472.21940 50.0 .0 30.3 .0 .0 −149.1 −149.1 −4.2 −.4 80.3 −153.7 −73.4 −1,545.61941 43.6 .0 30.3 .0 .0 −156.4 −156.4 −3.8 −.4 73.9 −160.6 −86.7 −1,632.31942 32.6 .0 30.3 .0 .0 −165.7 −165.7 −3.3 −.4 62.9 −169.4 −106.5 −1,738.8
Simulation Of Ground-Water Flow 69

1943 30.0 .0 30.3 .0 .0 −176.0 −176.0 −2.9 −.4 60.3 −179.3 −119.0 −1,857.81944 33.5 .0 30.3 .0 .0 −186.4 −186.4 −2.6 −.4 63.8 −189.4 −125.6 −1,983.41945 35.7 .0 30.3 .0 .0 −204.0 −204.0 −2.4 −.4 66.0 −206.8 −140.8 −2,124.21946 37.3 0.0 30.3 0.0 0.0 −226.8 −226.8 −2.1 −0.4 67.6 −229.3 −161.7 −2,285.91947 39.8 .0 30.3 .0 −.6 −269.6 −270.2 −1.9 −.4 70.1 −272.5 −202.4 −2,488.31948 41.0 .0 30.3 .0 −.7 −330.4 −331.1 −1.7 −.4 71.3 −333.2 −261.9 −2,750.21949 43.2 .0 30.3 .0 −.6 −357.0 −357.6 −1.6 −.4 73.5 −359.6 −286.1 −3,036.31950 44.7 .0 30.3 .0 −.7 −373.0 −373.7 −1.4 −.4 75.0 −375.5 −300.5 −3,336.81951 46.9 .0 30.3 .0 −.8 −394.6 −395.4 −1.2 −.5 77.2 −397.1 −319.9 −3,656.71952 49.7 .0 30.3 .0 −6.7 −333.0 −339.7 −1.0 −.5 80.0 −341.2 −261.2 −3,917.91953 52.8 .0 30.3 .0 −9.2 −339.0 −348.2 −.8 −.5 83.1 −349.5 −266.4 −4,184.31954 55.9 .0 30.3 .0 −9.6 −313.0 −322.6 −.6 −.5 86.2 −323.7 −237.5 −4,421.81955 61.2 .0 30.3 .0 −7.0 −324.5 −331.5 −.5 −.5 91.5 −332.5 −241.0 −4,662.81956 68.0 .0 30.3 .0 −13.5 −332.2 −345.7 −.5 −.5 98.3 −346.7 −248.4 −4,911.21957 80.9 .0 30.3 .0 −13.9 −309.4 −323.3 −.4 −.5 111.2 −324.2 −213.0 −5,124.21958 99.1 .0 30.3 .0 −12.7 −293.6 −306.3 −.3 −.5 129.4 −307.1 −177.7 −5,301.91959 107.1 .0 30.3 .0 −15.6 −301.0 −316.6 −.3 −.5 137.4 −317.4 −180.0 −5,481.91960 111.9 .0 30.3 .0 −16.9 −285.5 −302.4 −.3 −.5 142.2 −303.2 −161.0 −5,642.91961 118.4 .0 30.3 .0 −23.3 −278.5 −301.8 −.3 −.5 148.7 −302.6 −153.9 −5,796.81962 100.0 .0 30.3 .0 −28.5 −284.4 −312.9 −.2 −.5 130.3 −313.6 −183.3 −5,980.11963 101.7 .0 30.3 .0 −22.5 −317.5 −340.0 −.2 −.5 132.0 −340.7 −208.7 −6,188.81964 93.9 .0 30.3 .0 −24.7 −332.5 −357.2 −.2 −.5 124.2 −357.9 −233.7 −6,422.51965 97.4 .0 30.3 .0 −26.5 −331.3 −357.8 −.2 −.4 127.7 −358.4 −230.7 −6,653.21966 99.7 .0 30.3 .0 −29.1 −316.3 −345.4 −.1 −.4 130.0 −345.9 −215.9 −6,869.11967 92.8 .0 30.3 .0 −26.0 −297.8 −323.8 −.1 −.4 123.1 −324.3 −201.2 −7,070.31968 88.1 .0 30.3 .0 −28.6 −279.0 −307.6 −.1 −.4 118.4 −308.1 −189.7 −7,259.91969 90.3 .0 30.3 .0 −35.7 −258.3 −294.0 −.1 −.4 120.6 −294.5 −173.9 −7,433.81970 85.6 .0 30.3 .0 −30.1 −240.0 −270.1 −.1 −.4 115.9 −270.6 −154.7 −7,588.51971 83.5 .0 30.3 .0 −32.3 −217.1 −249.4 −.1 −.3 113.8 −249.8 −136.0 −7,724.6

Recharge Discharge Total Change in storage

Irrigation-return flows Pumpage Natural

Year Pumpage AVEK deliveries Natural Waste- water Public supply Agriculture Total Evapotran- spiration Ground-water underflow Recharge Discharge Annual Cumulative

Table 8. Simulated recharge, discharge, and change in storage for the Antelope Valley ground-water basin, California, 1915–95—Continued
70 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California 1972 85.3 .0 30.3 .0 −32.4 −192.2 −224.6 −.1 −.3 115.6 −225.0 −109.4 −7,834.0 1973 95.3 .0 30.3 .0 −33.8 −178.6 −212.4 .0 −.3 125.6 −212.7 −87.1 −7,921.1 1974 100.8 .0 30.3 .0 −32.2 −164.9 −197.1 .0 −.3 131.1 −197.4 −66.3 −7,987.4 1975 99.4 .0 30.3 .0 −30.3 −161.1 −191.4 .0 −.3 129.7 −191.7 −62.0 −8,049.4 1976 94.9 .0 30.3 .0 −31.7 −138.0 −169.7 .0 −.3 125.2 −170.0 −44.8 −8,094.2 1977 89.3 .0 30.3 .0 −29.0 −166.3 −195.3 .0 −.3 119.6 −195.6 −76.0 −8,170.2 1978 83.7 .0 30.3 .0 −36.4 −155.8 −192.2 .0 −.3 114.0 −192.5 −78.5 −8,248.7 1979 77.5 0.0 30.3 0.0 −26.0 −135.3 −161.3 0.0 −0.3 107.8 −161.6 −53.8 −8,302.4 1980 72.0 .0 30.3 .0 −26.1 −128.4 −154.5 .0 −.3 102.3 −154.8 −52.5 −8,354.9 1981 65.1 .0 30.3 .0 −26.9 −93.9 −120.8 .0 −.3 95.4 −121.1 −25.7 −8,380.6 1982 57.7 .0 30.3 .0 −25.4 −86.1 −111.5 .0 −.3 88.0 −111.8 −23.8 −8,404.4 1983 53.6 .0 30.3 .0 −20.9 −91.7 −112.6 .0 −.3 83.9 −112.9 −29.0 −8,433.4 1984 49.5 .0 30.3 .5 −27.0 −80.9 −107.9 .0 −.2 80.3 −108.1 −27.8 −8,461.1 1985 48.3 .0 30.3 1.4 −26.5 −64.3 −90.8 .0 −.2 80.0 −91.0 −11.0 −8,472.1 1986 41.4 7.9 30.3 2.0 −31.5 −55.1 −86.6 .0 −.2 81.6 −86.8 −5.2 −8,477.3 1987 44.4 9.1 30.3 2.9 −33.0 −60.6 −93.6 .0 −.2 86.7 −93.8 −7.1 −8,484.4 1988 39.8 10.2 30.3 3.2 −23.1 −47.8 −70.9 .0 −.2 83.5 −71.1 12.4 −8,472.0 1989 35.8 13.5 30.3 3.4 −39.1 −33.7 −72.8 .0 −.2 82.9 −73.0 9.9 −8,462.0 1990 34.8 14.8 30.3 4.9 −36.2 −34.5 −70.7 .0 −.2 84.8 −70.9 13.9 −8,448.2 1991 26.0 16.2 30.3 4.5 −56.5 −47.6 −104.1 .0 −.2 77.0 −104.3 −27.3 −8,475.5 1992 24.4 9.8 30.3 5.6 −38.3 −42.7 −81.0 .0 −.2 70.1 −81.2 −11.1 −8,486.6 1993 25.7 5.1 30.3 6.5 −33.4 −39.7 −73.1 .0 −.2 67.6 −73.3 −5.7 −8,492.3 1994 22.7 4.4 30.3 6.9 −40.2 −35.6 −75.8 .0 −.2 64.3 −76.0 −11.7 −8,504.0 1995 18.7 5.0 30.3 7.5 −40.4 −34.1 −74.5 .0 −.2 61.5 −74.7 −13.2 −8,517.1 Recharge Discharge Total Change in storage Irrigation-return flows Pumpage Natural

Year Pumpage

AVEK 

deliveries Natural

Wastewater Public supply Agriculture Total Evapotran- spiration Ground-water underflow Recharge Discharge Annual Cumulative

Table 8. Simulated recharge, discharge, and change in storage for the Antelope Valley ground-water basin, California, 1915–95—Continued
Simulation Of Ground-Water Flow 71

Figure 28. Simulated annual volumes of (A) recharge, (B) discharge, and (C) recharge in relation to discharge in the Antelope Valley ground-water basin, 

California, 1915–95.

0

100

200

300

400

100

200

300

400

100

200

300

400

1915

0

0

1925 1935 1945 1955 1965 1975 1985 1995

YEAR

Recharge and Discharge—

Recharge—

Discharge—

Total discharge

Pumpage—Total

Pumpage—Agriculture

Pumpage—Public Supply

Total

Agriculture—pumpage

Total discharge

Total recharge

Natural

Agriculture—Antelope Valley–East Kern

Water Agency deliveries

Natural (Evaportranspiration

and outflow)

Wastewater

ANNUAL VOLUME, IN THOUSAND ACRE-FEET

B

C

A
72 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

During the1991–95 period, pumpage averaged 

81,700 acre-ft/yr, which is only 23 percent of the 

pumpage during the 1949–53 period and total recharge 

averaged 68,100 acre-ft/yr, which is about 86 percent 

of the total recharge during the 1949-53 period. Model 

results indicate that about 13,700 acre-ft/yr of ground 

water was being removed from aquifer and aquitard 

storage, which is about 17 percent of the total 

pumpage. Compaction of the aquitards accounted for 

3,800 acre-ft/yr of water being removed from storage, 

which is 28 percent of the change in storage. Similar to 

the1949–53 period, the source of nearly all the groundwater pumpage from layer 2 was leakage from layer 1. 

Continued water-level declines (fig. 25), resulted in the 

cessation of simulated evapotranspiration and a 50-

percent reduction of ground-water underflow from the 

North Muroc subbasin compared to steady-state 

conditions.

Model Sensitivity Analysis

A sensitivity analysis was done to determine the 

sensitivity of the model to changes in model input 

parameters. Sensitivity analysis can help determine 

which model parameters have the greatest effect on a 

model; results of the analysis can guide future data 

collection efforts that will reduce model errors. The 

sensitivity simulations were done by changing one 

input parameter at a time, while holding all others 

constant. A limitation of this approach is that the 

effects of simultaneous changes of multiple input 

parameters are not evaluated. The sensitivity of the 

model was evaluated by comparing water levels and 

subsidence from the sensitivity simulations with those 

from the calibrated transient-state model at the end of 

the transient period (1995). Sensitivity simulations also 

were done for the steady-state model; results generally 

were similar to the results of the transient-state model 

and therefore are not discussed here.

Figure 29. Cumulative change in simulated ground-water storage in the Antelope Valley ground-water basin, 

California, 1915–95.

-10,000

-8,000

-6,000

-4,000

-2,000

0

1915 1925 1935 1945 1955 1965 1975 1985 1995

YEAR

CUMULATIVE STORAGE CHANGE,

IN THOUSAND 0F ACRE-FEET
Simulation Of Ground-Water Flow 73

Figure 30. Components of the simulated water budget for selected 

periods from the ground-water flow model of the Antelope Valley groundwater basin, California. (Units are in thousand acre-feet.)

Pumpage

Aquitard storage = -8.3

Aquitard storage = -13.3

Aquifer storage = -0.3

Aquifer storage = -263.0

108.2 254.8

Pumpage

26.5 55.2

6.2

1949–53 Average

1991–95 Average

Recharge

30.3

Evapotranspiration

1.2

Natural

recharge

Natural

recharge

Leakage

92.8

Agricultural

recharge

30.3

Leakage

24.4

Wastewater

recharge

Leakage

1.8

Evapotranspiration

29.9

0.5

Layer 1

Layer 2

Layer 3

Layer 1

Layer 2

Layer 3

Layer 1

Layer 2

Layer 3

Steady-state

Outflow

to north

Outflow

to north

0.2

Outflow

to north

47.5

30.3

Agricultural

recharge

31.6

0.4

Aquifer storage = -1.8

Aquitard storage = -1.8

Aquifer storage = -9.9

Aquitard storage = -2.0

Aquifer storage = 0.0

Aquifer storage = 0.0
74 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Model sensitivity was determined for variations 

in hydraulic conductivity (layer 1), transmissivity 

(layers 2 and 3), confined and unconfined storage 

coefficients, vertical leakance, pumpage, recharge, and 

the hydraulic-characteristic values of the flow barriers. 

The magnitude of these variations was somewhat 

subjective, but based loosely on the range of reasonable 

values for each parameter and on the sensitivity 

observed during the calibration process. Hydraulic 

conductivity, transmissivity, and specific yield were 

varied from 0.5 to 2 times calibrated values. Vertical 

leakance and confined storage coefficients were varied 

from 0.1 to 10 times calibrated values. Total pumpage, 

agricultural pumpage, and recharge were increased and 

decreased by 10 percent. The sensitivity of the model 

to the effects of the flow barriers was analyzed by 

removing the barriers (no restriction to flow) and 

reducing the hydraulic-characteristic values of the 

barriers to one-half the calibrated values (increased 

restriction to flow). Sensitivity-analysis results were 

aggregated into four subareas because the simulated 

water levels within each subarea showed a similar 

response to changes in the input parameters. These 

subareas are (1) the western subarea (the Finger Buttes, 

Neenach, and West Antelope subbasins); (2) the 

southeastern subarea (the Buttes and Pearland 

subbasins); (3) the northern subarea [the North Muroc 

subbasin and the part of the Lancaster subbasin north 

of barrier 7 (figure 11)]; and (4) the central subarea (the 

remainder of the Lancaster subbasin south of barrier 7). 

Water-level changes resulting from the 

sensitivity analysis are shown in table 9. Simulated 

water levels were most sensitive to changes in the 

hydraulic characteristic of the flow barrier. The largest 

water-level changes resulting from changes in the 

hydraulic characteristic of the flow barriers occurred in 

the western and southeastern subareas. Water levels in 

the northern and central subareas were relatively 

insensitive to changes in the hydraulic characteristics 

of the flow barriers compared with water levels in the 

western and southeastern subareas. The western and 

southern subareas also were sensitive to changes in 

hydraulic conductivity, transmissivity of layer 2, 

specific yield, and natural recharge.

Water levels in the northern and central subareas 

were most sensitive to changes in hydraulic 

conductivity, specific yield, inelastic skeletal storage 

coefficient, and vertical leakance between layers 1 and 

2. These subareas also were sensitive to the changes in 

total pumpage and agricultural pumpage. The 

insensitivity of the model to changes in transmissivity 

of layer 3 indicates that defining the base of the model 

at an altitude of 1,000 ft above sea level was 

reasonable.

The sensitivity of simulated land subsidence at 

the end of the transient period (1995) to selected model 

input parameters is shown in table 10. All the bench 

marks used for the subsidence analysis are located in 

the Lancaster subbasin (fig. 15), and, therefore, the 

results of the subsidence sensitivity analysis are for this 

subbasin only. Pumping-induced subsidence is 

controlled by the inelastic skeletal storage coefficient 

and the water-level drawdown below the 

preconsolidation head. Simulated subsidence, 

therefore, was most sensitive to the changes in inelastic 

skeletal storage and specific yield.

In summary, the results of the sensitivity analysis 

indicate that the model is sensitive to different 

parameters in different areas. In the northern and 

central subareas, the model is most sensitive to changes 

in hydraulic conductivity of layer 1, specific yield, 

inelastic skeletal storage coefficient, vertical leakance 

between layers 1 and 2, and pumpage. In the western 

and southeastern subbasins, the model is most sensitive 

to changes in hydraulic conductivity of layer 1, 

transmissivity of layer 2, specific yield, natural 

recharge, and the hydraulic-characteristic values. 

Because changes in one model parameter may be offset 

by changes in another, improving the understanding of 

one parameter may aid in decreasing the uncertainty of 

other parameters.

Limitations of the Model

A ground-water flow model is a valuable tool for 

testing the conceptualization of the ground-water flow 

system and for predicting the response of the system to 

changes in aquifer stresses. However, a model is only 

an approximation of the actual aquifer system and, 

therefore, will not exactly simulate the system being 

modeled. The model relies on estimates of aquifer 

properties and stresses, which have some degree of 

uncertainty, and it lacks the small-scale spatial and 

temporal variability present in the actual system. 
Simulation Of Ground-Water Flow 75

Water-level change, in feet

Western subarea Southeastern subarea Northern subarea Central subarea

Change in parameter 

or stress Layer Range Mean Median Range Mean Median Range Mean Median Range Mean Median

Flow barriers not simulated 1 −611/12 −192 −198 −125/73 −44 −48 −25/15 6 11 −52/29 −2 0

2 −626/16 −172 −52 −26/18 7 12 −36/27 −2 03 −628/14 −160 −34 −24/20 7 12 −36/25 −2 −1

Hydraulic characteristics of 

flow barriers × 0.5

1 2/278 118 128 −62/172 50 38 −12/4 −6 1 −6/52 1 02 4/273 98 14 −12/2 −6 −7 −5/17 1 03 4/273 94 11 −12/2 −7 −11 −5/14 1 0

Hydraulic conductivity of 

layer 1 × 0.5

1 12/245 104 105 27/340 162 130 −11/12 5 6 −29/126 14 62 14/142 91 102 −3/9 4 6 −15/113 11 53 14/138 89 101 −3/9 3 2 −11/112 11 5

Specific yield of layer 1 × 0.5 1 −26/−116 −76 −68 −119/89 −19 −19 −81/0 −25 −26 −184/131 −108 −110

2 −36/−113 −82 −84 −86/−22 −25 −26 −177/0 −115 −1103 −36/−111 −83 −98 −88/−22 −26 −26 −164/−62 −115 −111

Hydraulic conductivity of 

layer 1 × 2

1 −177/−9 −82 −87 −186/−8 −105 −94 −12/11 −6 −8 −106/14 −19 −142 −108/−11 −74 −72 −10/0 −6 −8 −101/3 −18 −133 −106/−11 −72 −84 −9/0 −5 −4 −100/2 −17 −12

Specific yield of layer 1 × 2 1 5/75 46 40 2/102 25 22 0/52 17 18 6/166 72 74

2 10/75 51 51 12/54 17 18 0/145 75 743 12/75 53 62 14/56 17 16 29/138 74 73

Natural recharge × 0.9 1 −56/−8 −34 −40 −36/0 −22 −23 −2/1 0 0 −24/0 −8 −7

2 −51/−9 −31 −34 −3/1 0 0 −23/0 −8 −73 −50/−9 −31 −29 −3/1 0 0 −23/−2 −8 −7

Table 9. Change in simulated water levels at the end of the transient period (1995) resulting from the sensitivity analysis of the ground-water flow model of the Antelope Valley ground-water basin, California[Subarea: Western (Finger Buttes, Neenach, and West Antelope subbasins); Southeastern (Buttes and Pearland subbasins); Northern (North Muroc and the part of the Lancaster subbasin north of barrier 7); Central (the part of the Lancaster subbasin south of barrier 7). Order of presentation: from most sensitive (highest median water-level change) to least sensitive (lowest median water-level change)]
76 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California Natural recharge × 1.1 1 9/54 34 40 0/35 21 21 0/2 0 0 −26/23 6 6

2 9/49 31 34 0/2 0 0 −19/23 6 63 9/48 30 29 0/2 0 0 −1/22 7 6

Inelastic skeletal storage 

coefficient of layer 2 × 10

1 0/27 4 1 0/32 2 0 0/59 12 7 0/63 36 282 0/26 5 1 0/65 16 8 0/89 41 423 0/26 6 2 0/62 20 25 0/69 42 44

Inelastic skeletal storage 

coefficient of layer 1 × 10

1 0/27 4 1 −1/23 1 0 0/56 12 6 0/56 31 322 0/26 5 1 0/50 13 7 0/51 32 333 0/26 5 1 0/49 17 21 2/49 33 34

Transmissivity of layer 2 × 2 1 −59/−1 −29 −30 −24/0 −3 −2 −14/3 0 0 −55/17 −8 −6

2 −64/3 −30 −30 −14/7 0 0 −61/33 −9 −83 −63/2 −29 −29 −5/4 1 1 −59/24 −8 −7

Transmissivity of layer 2 

× 0.5

1 0/39 21 21 0/15 3 2 −3/14 1 0 −26/37 5 32 −1/41 21 21 −9/16 0 0 −42/43 5 43 −1/41 21 21 −5/6 0 0 −33/41 5 3

Vertical leakance between 

layers 1 and 2 × 0.1

1 3/27 13 15 0/11 2 2 −2/15 2 2 −5/40 9 72 −36/26 4 7 −20/−1 −10 −7 −64/13 −10 −73 −34/25 4 7 −19/−4 −11 −14 −60/8 −10 −7

Transmissivity of layer 3 × 2 1 −28/0 −12 −11 −3/0 −1 −1 −4/1 0 0 −22/4 −2 −2

2 −30/1 −12 −11 −6/1 0 0 −23/4 −3 −23 −36/3 −12 −11 −6/2 0 0 −28/17 −3 −2

Water-level change, in feet

Western subarea Southeastern subarea Northern subarea Central subarea

Change in parameter 

or stress Layer Range Mean Median Range Mean Median Range Mean Median Range Mean Median

Table 9. Changes in simulated water levels at the end of the transient period (1995) resulting from the sensitivity analysis of the ground-water flow model of the Antelope Valley ground-water basin, California—Continued
Simulation Of Ground-Water Flow 77

Inelastic skeletal storage 

coefficient of layer 2 × 0.1

1 −5/0 −1 0 −7/0 0 0 −16/0 −5 −3 −15/0 −8 −82 −4/0 −1 0 −16/0 −6 −3 −15/0 −9 −93 −4/0 −1 0 −15/0 −7 −10 −15/0 −9 −9

Pumpage increased by 10 

percent

1 −7/0 −4 −4 −9/0 −2 −1 −8/0 −4 −3 −48/0 −8 −82 −7/0 −4 −5 −7/−2 −4 −4 −39/0 −9 −83 −8/0 −4 −5 −8/−2 −5 −5 −35/0 −9 −9

Agricultural pumpage 

decreased by 10 percent

1 0/7 3 4 0/3 1 1 0/3 0 0 −10/11 5 62 0/7 4 4 0/3 0 0 −7/10 5 63 0/7 4 5 0/3 0 0 −2/9 6 6

Pumpage decreased by 10 

percent

1 0/7 4 4 0/5 2 1 0/8 4 3 −8/40 7 72 0/7 4 5 2/8 4 4 −6/36 7 73 0/8 4 5 2/7 5 5 −1/32 8 8

Transmissivity of layer 3 

× 0.5

1 0/16 7 7 0/2 1 1 0/5 0 0 −3/13 2 12 0/17 7 7 −1/6 0 0 −5/14 2 13 −3/20 7 7 −2/7 0 0 −11/16 2 1

Agricultural pumpage 

increased by 10 percent

1 −7/0 −4 −4 −7/0 −1 −1 −3/0 0 0 −12/0 −6 −72 −7/0 −4 −5 −5/0 0 0 −11/0 −7 −73 −7/0 −4 −5 −4/0 0 0 −9/−3 −7 −7

Storage coefficient of layer 3 

× 10

1 0/9 6 6 −2/2 0 0 0/6 2 2 −13/13 5 72 1/9 6 7 1/5 3 3 −10/13 6 73 0/10 6 7 2/6 3 4 −6/17 6 6

Inelastic skeletal storage 

coefficient of layer 1 × 0.1

1 −4/0 −1 0 −4/1 0 0 −23/1 −4 −2 −18/0 −6 −62 −4/0 −1 0 −18/1 −4 2 −12/0 −6 −63 −4/0 −1 0 −13/1 −5 −7 −11/0 −6 −6

Water-level change, in feet

Western subarea Southeastern subarea Northern subarea Central subarea

Change in parameter 

or stress Layer Range Mean Median Range Mean Median Range Mean Median Range Mean Median

Table 9. Changes in simulated water levels at the end of the transient period (1995) resulting from the sensitivity analysis of the ground-water flow model of the Antelope Valley ground-water basin, California—Continued
78 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Vertical leakance between 

layers 1 and 2 × 10

1 −12/−1 −6 −4 −7/0 −1 0 −3/3 0 0 −21/4 −3 −22 −18/11 −4 −3 −1/6 2 1 −18/15 −1 03 −17/5 −4 −3 −1/5 2 2 −13/13 −1 0

Vertical leakance between 

layers 2 and 3 × 0.1

1 −1/7 2 2 0/1 1 1 −2/13 −1 −1 −12/19 1 02 −1/7 2 2 −2/15 0 −1 −12/21 1 03 −37/9 −1 1 −6/6 0 −1 −35/74 3 4

Elastic storage coefficient of 

layer 1 × 10

1 −4/5 2 2 −2/2 1 1 0/3 1 2 −17/4 0 12 −4/5 2 2 0/3 1 2 −15/4 0 13 −4/5 2 2 0/2 1 2 −8/3 1 1

Elastic storage coefficient of 

layer 2 × 10

1 −2/2 1 1 −3/1 0 0 0/3 2 2 −18/2 0 12 −3/2 1 1 −1/3 2 2 −16/2 −1 03 −3/2 1 1 −1/3 2 2 −10/2 0 0

Vertical leakance between 

layers 2 and 3 × 10

1 −2/1 −1 −1 −1/0 0 0 −7/1 0 0 −13/5 0 02 −3/1 −1 −1 −9/1 0 0 −13/10 −1 03 −6/5 0 0 −7/1 0 0 −19/9 −1 0

Storage coefficient 

representing the compressibility of water for layer 2 × 10

1 0/2 1 1 −4/1 0 0 0/2 0 0 −18/3 1 12 0/2 1 1 0/2 1 1 −15/3 1 13 0/2 1 1 0/2 1 1 −9/2 1 1

Storage coefficient of layer 3 

× 0.1

1 −1/0 −1 −1 −1/1 0 0 −1/0 −1 0 −1/0 −1 −12 −1/0 −1 −1 −1/0 −1 0 −1/0 −1 −13 −1/0 −1 −1 −2/0 −1 0 −2/0 −1 −1

Water-level change, in feet

Western subarea Southeastern subarea Northern subarea Central subarea

Change in parameter 

or stress Layer Range Mean Median Range Mean Median Range Mean Median Range Mean Median

Table 9. Changes in simulated water levels at the end of the transient period (1995) resulting from the sensitivity analysis of the ground-water flow model of the Antelope Valley ground-water basin, California—Continued
Simulation Of Ground-Water Flow 79

Wastewater recharge × 0.5 1 0 0 0 −3/0 0 0 0/1 0 0 −28/1 −1 0

2 0 0 0 0/1 0 0 −23/0 −1 03 0 0 0 0/1 0 0 −7/0 −1 0

Wastewater recharge × 2 1 0 0 0 0/6 0 0 0/1 0 0 0/51 1 0

2 0 0 0 0/1 0 0 0/43 1 03 0 0 0 0/1 0 0 0/14 1 0

Storage coefficient 

representing the compressibility of water for layer 1 × 0.1

1 0 0 0 0 0 0 −1/0 0 0 0 0 02 0 0 0 −1/0 0 0 −1/0 0 03 0 0 0 −1/0 0 0 0 0 0

Storage coefficient 

representing the compressibility of water for layer 1 × 10

1 0 0 0 0 0 0 0/1 0 0 0/1 0 02 0 0 0 0/1 0 0 0/1 0 03 0/1 0 0 0/1 0 0 0/1 0 0

Storage coefficient 

representing the compressibility of water for layer 2 × 0.1

1 −1/0 0 0 −1/0 0 0 −1/0 0 0 −1/0 0 02 −1/0 0 0 −1/0 0 0 −1/0 0 03 −1/0 0 0 −1/0 0 0 −1/0 0 0

Elastic skeletal storage 

coefficient of layer 1 × 0.1

1 −1/1 0 0 −1/0 0 0 −1/0 0 0 −1/0 0 02 −1/1 0 0 −1/0 0 0 −1/0 0 03 −1/1 0 0 −1/0 0 0 −1/0 0 0

Elastic skeletal storage 

coefficient of layer 2 × 0.1

1 −1/1 0 0 −1/0 0 0 −1/0 0 0 −1/1 0 02 −1/0 0 0 −1/0 0 0 −1/1 0 03 −1/1 0 0 −1/0 0 0 −1/0 0 0

Water-level change, in feet

Western subarea Southeastern subarea Northern subarea Central subarea

Change in parameter 

or stress Layer Range Mean Median Range Mean Median Range Mean Median Range Mean Median

Table 9. Changes in simulated water levels at the end of the transient period (1995) resulting from the sensitivity analysis of the ground-water flow model of the Antelope Valley ground-water basin, California—Continued
80 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Table 10. Change in simulated land subsidence at the end of the transient period (1995) resulting from changes in selected model input parameters and 

stresses during the sensitivity analysis of the ground-water flow model of the Antelope Valley ground-water basin, California

[Order of presentation: from most sensitive (highest median subsidence change) to least sensitive (lowest median subsidence change)]

Change in parameter or stress

Change in simulated subsidence, in feet

Range Mean Median

Layer 2 inelastic skeletal storage coefficient × 10 1.65/14.20 6.08 5.94

Layer 1 inelastic skeletal storage coefficient × 10 2.81/8.47 5.25 5.24

Layer 1 specific yield × 0.5 1.90/7.98 4.08 3.40

Layer 1 specific yield × 2 −3.99/−1.37 −2.29 −1.93

Layer 2 inelastic skeletal storage coefficient × 0.1 −4.03/−.61 −1.54 −1.39

Layer 1 inelastic skeletal storage coefficient × 0.1 .21/1.53 1.53 .42

Pumpage increased by 10 percent −.01/.95 .38 .29

Agricultural pumpage increased by 10 percent −.01/.73 .31 .28

Layer 1 elastic skeletal storage coefficient × 10 −.09/.73 .31 .23

Layer 2 elastic skeletal storage coefficient × 10 −.06/.65 .28 .23

Layer 3 storage coefficient × 10 −.41/−.15 −.25 −.20

Pumpage decreased by 10 percent −.49/−.09 −.21 −.20

Natural recharge × 1.1 −.41/−.05 −.18 −.17

Natural recharge × 0.9 .04/.46 .18 .16

Agricultural pumpage decreased by 10 percent −.24/−.04 −.14 −.15

Hydraulic conductivity of layer 1 × 2 −.32/1.05 .33 .14

Vertical leakance between layers 1 and 2 × 0.1 −.26/.42 .08 .06

Hydraulic conductivity of layer 1 × 0.5 −.56/.38 −.08 −.06

Vertical leakance between layers 1 and 2 × 10 −.72/.12 −.12 −.05

Transmissivity of layer 3 × 2 −.07/.29 .06 .04

Layer 2 storage coefficient representing the compressibility of water ×10 −.09/−.03 .05 .04

Vertical leakance between layers 2 and 3 × 0.1 −.54/.12 −.07 .03

Layer 1 elastic skeletal storage coefficient × 0.1 −.07/.0 −.03 −.02

Transmissivity of layer 2 × 2 −.33/.62 .05 −.02

Layer 2 elastic skeletal storage coefficient × 0.1 −.06/.0 −.03 −.02

Layer 3 storage coefficient × 0.1 .01/.05 .03 .02

Vertical leakance between layers 2 and 3 × 10 −.29/.19 −.01 −.02

Transmissivity of layer 2 × 0.5 −.57/.54 −.01 .02

Layer 2 storage coefficient representing the compressibility of water × 0.1 −.01/.0 −.01 −.01

Hydraulic characteristics of low barriers × 0.5 −.04/.09 .00 .01

Wastewater recharge × 0.5 .0/.01 .00 .00

Wastewater recharge × 2 −.01/.0 .00 .00

Flow barriers not simulated −.34/.53 .04 .00

Transmissivity of layer 3 × 0.5 −.30/.04 −.05 .00

Layer 1 storage coefficient representing the compressibility of water × 0.1 −.03/.08 .00 .00

Layer 1 storage coefficient representing the compressibility of water × 10 .0/.01 .00 .00
Simulation Of Ground-Water Flow 81

Water levels and land subsidence calculated by 

the model are average values for the area represented 

by each model cell. Simulated water levels can vary 

considerably from measured water levels because of 

well location, depth, and construction. For example, 

wells may be screened over a depth represented by 

more than one model layer, whereas, measured water 

levels may be a composite of the actual water levels in 

each layer. The size of the model cell and the length of 

the stress period of the model are appropriate for the 

resolution of available data and for simulations on a 

regional scale. Because model uncertainty increases 

significantly with the decreasing size of the area of 

interest, the model generally should not be used to 

address local-scale problems.

Little is known about the geohydrology of the 

Finger Buttes, West Antelope, Neenach, Pearland, and 

Buttes subbasins. Consequently, hydraulic properties 

specified in the model for these subbasins were based 

on limited data. Available data indicate that hydraulic 

conductivity of the aquifer material is lower in the 

upslope areas adjacent to the mountain fronts than in 

the downslope areas, which is contrary to what would 

be expected for areas with typical alluvial fan 

development, where coarse-grained material is 

deposited at the fan heads (higher hydraulic 

conductivity) and fine-grained material is deposited at 

the fan margins (lower conductivity). In these five 

subbasins, which have depths to water greater than the 

other subbasins, the water table may be below the more 

transmissive coarse-grained material. Tectonic 

processes, such as uplift and erosion, also may affect 

the hydrologic properties of the aquifers. The waterlevel data for these subbasins used to calibrate the 

model also were limited; consequently, the differences 

between the simulated and the measured water levels 

were greatest in these subbasins. Although the 

simulated water levels for Finger Buttes, West 

Antelope, Neenach, Pearland, and Buttes subbasins 

provide reasonable boundary conditions for simulating 

the water levels in the Lancaster subbasin for the 

calibration period, the high degree of uncertainty in the 

model input for these subbasins greatly reduces the 

potential for accurate predictions of ground-water 

conditions in these subbasins. Additional 

geohydrologic data would improve the accuracy of the 

model for these subbasins. 

The model is sensitive to the location and 

simulated barrier effect of faults. It is likely that there 

are additional concealed faults crossing the study area 

that have not yet been identified in areas that are not 

currently being stressed. The barrier effect of these 

faults may become apparent in the future, if pumping 

or recharge occurs near unknown faults. If these faults 

significantly affect ground-water flow, the faults should 

be added to the model.

The quantity and distribution of agricultural 

pumpage is uncertain. As shown in the sensitivity 

analysis, the variability in estimates of pumpage can 

significantly affect model results. More accurate 

estimates of agricultural pumpage would improve the 

model results. Results from simulations of future 

conditions that include pumpage for areas where 

pumping had not previously occurred should be 

interpreted carefully because the stresses from 

pumping were not simulated during the calibration 

process of the model. 

Natural and agricultural recharge are difficult to 

measure and, therefore, the recharge rates and temporal 

distribution of recharge were based on the model 

calibration results. The calibration process resulted in a 

lower rate of natural recharge than had been estimated 

for previous studies. Additional geohydrologic data are 

needed to confirm that the natural recharge rates used 

in the model are accurate; however, collection of 

additional data was beyond the scope of this study. The 

travel time for irrigation-return flows to reach the water 

table was simulated as a constant (10 years) for the 

entire model area. Model results probably could be 

improved by more accurately specifying the travel time 

for each area on the basis of the depth-to-water and 

aquifer material.

The approach taken in this study to simulate 

aquifer-system compaction in unconfined portions of 

the model layer 1 using the IBS1 package will tend to 

overestimate compaction in that layer, where the water 

table declines, and underlying mode layers. IBS1 does 

not account for changes in the total stress that occur 

when the water table rises and lowers, as it may in 

model layer 1. Changes in the position of the water 

table cause changes in the total stress exerted on the 

underlying sediment owing to the overlying weight of 

water that changes when the water table fluctuates. 

These effects are relatively small and the overestimated 

subsidence in the model simulation is expected to be in 

the range of 1.18 to 1.33 percent, and is primarily 

dependent upon the porosity of the sediments in model 

layer 1 in the zone of water-table fluctuation.
82 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Although the model does a relatively good job of 

simulating the measured quantity of land subsidence, 

the IBS1 Package used to simulate aquifer compaction 

does not accurately simulate the delayed drainage in 

the thick aquitards or the timing of subsidence in areas 

where thick aquitards are a major contributor to 

subsidence. ISB1 simulates the instantaneous release 

of water from storage from fine-grained, compressible 

interbeds for a head decline in the surrounding aquifer. 

As such, the heads in the interbeds are assumed to 

equilibrate instantaneously with head changes in the 

aquifers. This treatment ignores the delayed 

equilibration of head associated with the low 

permeability interbeds and aquitards which is further 

exacerbated by their thickness—the time constants 

governing head equilibration in these units is 

proportional to their squared thickness. Additionally, 

the model does not simulate subsidence throughout the 

modeled area because values of inelastic storage only 

were specified in areas where subsidence previously 

had been measured. In areas where inelastic skeletal 

storage was not specified, future water-level declines 

below preconsolidation heads could cause subsidence 

where compressible sediments exist in these areas. 

Subsidence cannot be simulated for these areas unless 

inelastic skeletal storage coefficients and 

preconsolidation heads are specified for these areas.

Owing to uncertainty in some parameters used in 

the model, especially in the agricultural component of 

pumpage, model results from the predictive simulation 

should be used with caution. The model, like most 

models, is not ideally suited for predicting absolute 

changes in water levels or subsidence. The most 

appropriate application of the model is comparing the 

relative effects of different water-management 

scenarios on the aquifer system.

Simulation of Aquifer-System Response to 

Pumping Scenarios

A calibrated flow model can be used as a tool to 

evaluate and compare the responses of an aquifer 

system to potential future stresses. Management 

actions involving changes in the quantity and 

distribution of pumpage or recharge can be simulated 

and the aquifer-system responses compared to evaluate 

the effectiveness of these actions satisfying 

management goals. Although water levels and 

subsidence simulated for a given scenario may not 

accurately represent the values in the real system, the 

relative differences in water levels and subsidence over 

time can be compared to provide managers with useful 

information for planning and decision making.

For this study, the model was used to simulate 

the aquifer-system response to two potential pumping 

scenarios for 1995–2025. For both scenarios, all model 

parameters were unchanged from those specified in the 

transient-state simulation. Natural recharge and 

artificial recharge from irrigation-return flows and from 

reclaimed wastewater were specified equal to the 

quantities specified for those sources for 1995. For both 

scenarios, recharge from irrigation-return flows was 

calculated as 30 percent of the water used for irrigation 

and was assumed to recharge the water table 10 years 

after the irrigation water was applied. For scenario 1, 

total annual pumpage for 1995–2025 was specified 

equal to total annual pumpage in 1995. For scenario 2, 

public-supply pumpage was increased 3.3 percent 

annually and agricultural pumpage was assumed to be 

75 percent greater than agricultural pumpage in 1995 

for the simulated period 1995–2025. Recharge from 

irrigation-return flows was correspondingly increased 

by 75 percent. The annual increase in public-supply 

pumpage was based on population growth projections 

for Palmdale and Lancaster from the Southern 

California Association of Governments (2001). The 

increase in agricultural pumpage was based on cropacreage data from the Los Angeles County Agricultural 

Commissioner which indicated that agricultural 

production in the study area increased as much as 75 

percent during 1995–98. The spatial distribution of 

pumpage for both scenarios was the same as was 

specified for 1995. 

The simulated water-level (layer 1) and landsubsidence values for both scenarios are shown in 

figures 31 and 32, respectively. Recall that the 

simulated water-level and land-subsidence values are 

averages for the entire model cell and, therefore, may 

be different from the measurements for specific wells 

and bench marks.
Simulation Of Ground-Water Flow 83

Figure 31. Simulated water levels for two pumping scenarios for the Antelope Valley ground-water basin, California, 1995–2025.

2,500

2,600

2,700

2,800

2,900

5N/10W-6N1

2,300

2,400

2,500

2,600

2,700

6N/9W-11N1

1,700

1,800

1,900

2,000

2,100

6N/11W-19E6

2,000

2,100

2,200

2,300

2,400

7N/10W-33J1

1995 2005 2010 2000 2015 2020 2025 1995 2005 2010 2000 2015 2020 2025

YEAR

2,000

2,100

2,200

2,300

2,400

7N/11W-31M1

2,400

2,500

2,600

2,700

2,800

6N/10W-34D1

SIMULATED WATER LEVEL, IN FEET ABOVE SEA LEVEL

Scenario 1, layer 1

Scenario 2, layer 1

EXPLANATION

Pearland subbasin

Buttes subbasin

Buttes subbasin

Lancaster subbasin

Lancaster subbasin

Lancaster subbasin

Below 1,950 feet above sea level, the water

table is below the bottom of layer 1; the

water levels for layers 2 and 3 are not shown
84 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 31.—Continued.

2,000

2,100

2,200

2,300

2,400

2,000

2,100

2,200

2,300

2,400

2,000

2,100

2,200

2,300

2,400

2,000

2,100

2,200

2,300

2,400

1995 2005 2010 2000 2015 2020 2025 1995 2005 2010 2000 2015 2020 2025

YEAR

2,000

2,100

2,200

2,300

2,400

2,000

2,100

2,200

2,300

WA

2,400

TER LEVEL, IN FEET ABOVE SEA LEVEL

Lancaster subbasin

Lancaster subbasin

Lancaster subbasin

Lancaster subbasin

Lancaster subbasin Lancaster subbasin

7N/12W-19R1 8N/10W-8R3

7N/14W-13A1 8N/11W-34D2

8N/10W-1Q3 8N/13W-9K1
Simulation Of Ground-Water Flow 85

Figure 31.—Continued.

2,000

2,100

2,200

2,300

2,400

2,000

2,100

2,200

2,300

2,400

WATER LEVEL, IN FEET ABOVE SEA LEVEL

Lancaster subbasin

Lancaster subbasin

Lancaster subbasin

2,100

2,200

2,300

2,400

2,500

8N/13W-35M1

9N/9W-10R1

8N/14W-23G1

1995 2005 2010 2000 2015 2020 2025 1995 2005 2010 2000 2015 2020 2025

YEAR

2,000

2,100

2,200

2,300

2,400

Neenach subbasin

West Antelope subbasin

North Muroc subbasin

2,200

2,300

2,400

2,500

2,600

2,500

2,600

2,700

2,800

2,900

8N/17W-1N1

11N/9W-36R1

9N/14W-20B1
86 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Figure 32. Simulated land subsidence near indicated bench marks for two pumping scenarios for the Antelope Valley ground-water basin, 

California, 1995–2025.

BM 2317

3

2

1

4

5

6

0

3

2

1

4

5

6

0

3

2

1

4

5

6

0

3

2

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-1

-1

-1

-1

-1

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BM 823

BM 479

BM 474

BM 2180

BM 1159

BM 2169

BM 537

BM 1469

BM 483

SIMULATED LAND SUBSIDENCE, IN FEET

1995 2000 2005 2010 2015 2020 2025 1995 2000 2005 2010 2015 2020 2025

YEAR

Scenario 1

Scenario 2

EXPLANATION
Simulation Of Ground-Water Flow 87

For scenario 1, water levels rose in the western 

Lancaster subbasin and in the Neenach and West 

Antelope subbasins, continuing the long-term recovery 

from drawdown caused by the much greater historical 

agricultural pumpage (Carlson and others, 1998; 

Carlson and Phillips, 1998). Water levels rose as much 

as 11 ft at well 9N/14W-20B1 in the Neenach subbasin 

and as much as 36 ft at well 8N/17W-1N1 in the West 

Antelope subbasin; however, the rate of the water-level 

rise declined over time (fig. 31). The decline in the rate 

of water-level rise was caused, in part, by the 10-year 

delay in recharge from irrigation-return flows. Even 

though the simulated annual pumpage was constant 

from 1995 to 2025, recharge from irrigation-return 

flows was based on agricultural pumpage prior to 1995, 

which was higher than in 1995. From 1996 to 2004, the 

annual quantity of recharge from irrigation-return flows 

gradually declined; in 2005, recharge from irrigationreturn flows remained constant for the remainder of the 

simulation period. In the southern, eastern, and 

northern part of the Lancaster subbasin and in the 

Buttes, Pearland, and North Muroc subbasins, water 

levels generally declined as a result of the scenario 1 

pumpage, except at well 7N/10W-33J1 in the eastern 

part of the Lancaster subbasin where water levels did 

not decline. The largest decline in the simulated water 

levels (more than 100 ft) was at well 6N/11W-19E6, 

where the water level declined below the bottom of 

model layer 1 into layer 2 in 2006. The water level in 

layer 2 continued to decline after 2006 (water levels for 

layer 2 are not shown in fig. 31). Simulated water-level 

declines were greatest at this well because most of the 

pumping for public supply occurs in this area. Further 

land subsidence was simulated in the central part of the 

Lancaster subbasin north and east of the city of 

Lancaster. The maximum simulated subsidence for 

scenario 1 occurred at bench mark BM 479 (1.9 ft). 

These model results indicate that pumpage for public 

supply at 1995 rates in the Lancaster and Palmdale 

areas will result in significant water-level declines and 

land subsidence, indicating that future pumpage may 

have to be redistributed or augmented by artificial 

recharge. 

For scenario 2, public supply pumpage was 

increased 3.3 percent annually and annual agricultural 

pumpage and irrigation-return flows were 75 percent 

greater than the values simulated for scenario 1. 

Similar to scenario 1, water levels rose in the western 

Lancaster subbasin; however, the water-level rise was 

not as great. In the Neenach subbasin, the water levels 

for well 9N/14W-20B1 remained unchanged from 

1995 to 2025. In the southern, eastern, and northern 

part of the Lancaster subbasin and in the Buttes and 

Pearland subbasins, water levels declined more than 

the water levels for scenario 1. Pumpage increases for 

scenario 2 resulted in significant water-level declines in 

the southern and northeastern part of the Lancaster 

subbasin (wells 6N/11W-19E6, 7N/12W-19R1, and 

8N/10W-1Q3) because most pumping for public 

supply occurs in these areas. Water-level declines were 

as great as 150 ft in the south-central part of the 

Lancaster subbasin. Simulated subsidence at bench 

marks BM 474, BM 479, BM 537, and BM 2180 was 

greater for scenario 2 than for scenario 1, and the 

maximum simulated subsidence for 1995–2025 was 

about 5 ft at bench mark BM 474. The simulated 

subsidence was the greatest in the central Lancaster 

subbasin north and east of the city of Lancaster, near 

bench marks BM 474, BM 479, and BM 2180, where 

combined public supply and agricultural pumping are 

greatest. Because inelastic storage coefficients were 

specified only for areas where subsidence has 

previously been measured, neither scenario 1 nor 2 is 

able to predict subsidence from future water-level 

declines outside this area.
88 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

SUMMARY

Ground-water pumpage has provided from 50 

percent to more than 90 percent of the water supply in 

Antelope Valley since the early 1900s. This long-term 

ground-water pumpage has caused water-level declines 

and associated increased pumping lifts; it also has 

reduced well efficiencies and caused land subsidence. 

Urban growth and limited available surface-water 

supply are likely to continue to increase reliance on 

ground water. A numerical ground-water flow and 

land-subsidence model of the Antelope Valley groundwater basin was developed to improve the 

understanding of the ground-water flow system. The 

model can be used as a tool in making informed watermanagement decisions.

The Antelope Valley ground-water basin consists 

of unconsolidated alluvial and lacustrine deposits, 

more than 5,000 ft thick in places. The alluvium 

consists of poorly sorted gravels, sands, silts, and clays. 

Older, deep alluvial deposits are more compacted and 

indurated than the younger, shallow deposits. The 

lacustrine deposits are as much as 300 ft thick and are 

composed mostly of clay and silty clay with some 

layers of sand and silt. The lacustrine deposits are as 

much as 800 ft below land surface near Palmdale, 

become progressively shallower northward, and are 

exposed at the surface near the southern edge of Rogers 

Lake.

The study area was conceptually divided into 

seven ground-water subbasins on the basis of faults, 

bedrock outcrops, ground-water divides, and arbitrary 

boundaries. Some faults seem to act as barriers to 

ground-water flow. Geophysical logs from previous 

studies show that induration of the alluvial material 

increases with depth, which suggests a decrease in the 

ability to transmit and store water with depth. Data 

from test wells drilled in the Lancaster area and at 

Edwards Air Force Base indicate that there is a change 

in the properties of the aquifer materials at altitudes of 

about 1,950 ft and 1,550 ft above sea level. 

Unconsolidated material at altitudes of 1,950 ft above 

sea level and greater was designated as the upper 

aquifer, unconsolidated material between 1,950 and 

1,550 ft above sea level was designated as the middle 

aquifer, and unconsolidated material below 1,550 ft 

above sea level was designated as the lower aquifer. 

The lacustrine deposits are contained within the upper 

aquifer in the northern part of the Lancaster subbasin 

and primarily within the middle aquifer in the southern 

part of the Lancaster subbasin. The upper aquifer is 

unconfined to confined and the middle and lower 

aquifers are confined.

Prior to ground-water development in Antelope 

Valley, recharge to the ground-water system was 

primarily from the infiltration of precipitation runoff 

near the valley margins. Precipitation over the valley 

floor generally is less than 10 in./yr and probably 

contributes little, if any, recharging to the aquifer 

system owing to the high evapotranspiration rates in 

the study area. In the lowland parts of the valley, 

discharge from the aquifer system was primarily from 

evapotranspiration. A small amount of ground water is 

discharged from the valley north into the Fremont 

Valley Basin. 

Development of the ground-water system began 

around 1915 and increased rapidly into the 1950s. 

Ground-water pumping has caused large water-level 

declines in the ground-water basin; as a result, 

evapotranspiration has decreased to an insignificant 

amount. The water-level declines from pumping also 

have caused land subsidence owing to the compaction 

of compressible sediments. The major source of 

discharge in the valley has changed from 

evapotranspiration to ground-water pumping; ground 

water now flows from areas of recharge toward the 

major pumping centers rather than to natural discharge 

areas where evapotranspiration had occurred. Recharge 

from the infiltration of irrigation-return flows is a major 

contributor of recharge to the aquifer system. 

A numerical ground-water flow model was 

developed and calibrated for steady-state predevelopment (1915) and transient-state (1915–95) 

conditions. The model aggregates old and new 

geohydrologic information to aid in better 

understanding the ground-water flow system and to aid 

in making informed water-management decisions. The 

model was vertically discretized into three layers. 

Layer 1 (upper aquifer) extends from the water table to 

an altitude of 1,950 ft above sea level or to bedrock, 

whichever is higher; layer 2 (middle aquifer) extends 

from 1,950 to 1,550 ft above sea level or to bedrock, 

whichever is higher; layer 3 (lower aquifer) extends 

from 1,550 to 1,000 ft above sea level or to bedrock, 

whichever is higher. The bottom of layer 3 was set to 

an altitude of 1,000 ft because it was assumed that the 

alluvial material below this depth was not a significant 

part of the flow system owing to compaction and 

induration of this older material. 
References Cited 89

The model was calibrated by adjusting hydraulic 

conductivity, transmissivity, specific yield, natural 

recharge, aquitard thickness, hydraulic characteristic of 

flow barriers, and preconsolidation head within 

reasonable limits to obtain reasonable agreement 

between simulated and measured water levels and 

subsidence. The model did well in simulating water 

levels in the Lancaster, Neenach, Pearland, and Buttes 

subbasins where the geohydrology is well known. In 

the North Muroc Subbasin, measured and simulated 

horizontal and vertical water-level gradients match 

well; however, the simulated water levels were higher 

than the measured water levels. In the Finger Buttes 

and West Antelope subbasins, where few 

geohydrologic data are available, the match between 

the simulated and the measured water levels was not as 

good. Measured and simulated land subsidence data 

also were compared and matched well at all the bench 

marks used for calibration.

During model calibration, natural recharge was 

reduced from an initial estimate of 40,700 acre-ft/yr to 

30,300 acre-ft/yr. Results of the transient-state 

simulation indicate that more than 8.5 million acre-ft of 

ground water was removed from storage during 1915–

95, with most of the storage change occurring between 

about 1945 and 1975. Ground-water storage changed 

little during the final 10 years of simulation period 

because discharge by pumpage had declined 

sufficiently to be balanced by recharge. Model results 

show that during the period of peak pumping 

(1949–53) 79 percent of the ground water withdrawn 

from the aquifer came from storage. Water released 

from compaction of the aquitards accounted for about 

21,600 acre-ft/yr of the ground water removed from 

storage. Pumpage from layer 2 induced leakage of 

ground water from layer 1, which accounted for about 

86 percent of the total pumpage in layer 2. During the 

last 5 years of the simulation (1991–95), only 17 

percent of pumpage came from storage.

Results of the sensitivity analysis showed that 

the model was most sensitive to changes in the 

hydraulic characteristic of flow barriers, specific yield, 

hydraulic conductivity of layer 1, natural recharge, 

inelastic skeletal storage coefficient, transmissivity of 

layer 2, and pumpage. The sensitivity of the model 

varied spatially. The model was not sensitive to the 

transmissivity of layer 3, which indicates that 

specifying the bottom of the model at 1,000 ft above 

sea level was a reasonable assumption.

The calibrated model was used to test the aquifer 

response to two future pumping scenarios for 1995 to 

2025. For scenario 1, annual pumpage remained the 

same as pumpage specified for 1995. Water levels rose 

in the western Lancaster subbasin and in the Neenach 

and West Antelope subbasins, continuing the long-term 

recovery from drawdown caused by the much greater 

historical agricultural pumpage. In areas where 

pumping for public supply is concentrated, water levels 

continued to decline and subsidence continued in the 

central part of the Lancaster subbasin. Water-level 

declines were greatest (more than 100 ft) in the southcentral part of the basin because most of the public 

supply pumpage occurs in this area; as much as 1.9 ft 

of additional subsidence was simulated in the central 

part of the ground-water basin for 1995 through 2025. 

For scenario 2, public supply pumpage was increased 

3.3 percent annually compared with that specified for 

1995 and agricultural pumpage was increased 75 

percent. This scenario resulted in significant waterlevel declines in the southern and eastern part of the 

Lancaster subbasin because most of the public supply 

and agricultural pumping occurs in these areas. Results 

of this simulation showed that water levels declined 

more than 150 feet in the south-central part of the 

ground-water basin and that an additional 5 feet of 

subsidence was simulated in the central part of the 

basin.

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Appendix: Water use 1992–95 93

APPENDIX: WATER USE 1992–95

Water managers and planners require 

comprehensive and accurate water-use data to make 

informed water-management decisions. Templin and 

others (1995) compiled available water-use data for 

Antelope Valley for 1919–92 (1992 data were 

incomplete). For the purpose of this study, annual 

water-use data for 1992–95 were compiled to extend 

the period of record reported by Templin and others 

(1995) for use in the ground-water flow and subsidence 

model developed for this study. 

The methodology, sources, and areal extent 

[Antelope Valley drainage basin (fig. 1)] used to obtain 

the water-use data for 1992–95 were consistent with 

those used by Templin and others (1995) so that data 

for all years could be compared and analyzed. As a part 

of their work, Templin and others (1995) developed a 

database of ground-water pumpage for 1947–92; 

during this current study, pumpage data for 1992–95 

were collected and added to the 1947–92 database. 

Some additional data for 1947–91 also were obtained 

and added to the database. The tables in this appendix 

include data only for 1992–95, but the graphs show 

data for the entire period of the pumpage database 

(1947–95) and, therefore, can show trends in water use 

over time.

Water supply for Antelope Valley was obtained 

from four sources; (1) ground-water pumping, (2) local 

surface-water diversions, (3) imported water, and (4) 

reclaimed wastewater. Each of these components and 

total annual water supply for 1947–95 are shown in 

figure A1. Total water supply increased during 

1992–95 because of increases in imported surface 

water in 1992 and 1993, increases in ground-water 

pumping in 1994 and 1995, and increased use of 

reclaimed wastewater. Historically, ground-water 

pumping has been the primary source of water supply 

in the valley, and remained the primary source during 

1992–95. Supply from local surface-water sources was 

small and generally remained steady during 1992–95.

Figure A1. Sources of water supply in the Antelope Valley ground-water basin, California, 1947–95.

Annual water supplies—

Total supply

Ground-water pumpage

Local surface water

Imported water

Reclaimed wastewater

YEAR

WATER SUPPLY, IN ACRE-FEET

300,000

250,000

200,000

150,000

100,000

50,000

0

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995
94 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Ground Water

Templin and others (1995) divided ground-water 

use into two categories, public supply and self supply. 

Ground-water pumpage for public supply represents 

ground water that is withdrawn by public or private 

entities for sale and delivery to customers, usually for 

domestic, commercial, and industrial uses. Groundwater pumpage for self supply represents ground water 

that is withdrawn by private entities for use by that 

entity. In Antelope Valley, most ground-water pumpage 

for self supply is used for agriculture and in this report 

is referred to as agricultural pumpage. Most of the 

ground-water-use data for public supply was obtained 

by contacting the suppliers directly; however, some of 

the data were obtained from pumpage records 

maintained by the California State Water Resources 

Control Board (SWRCB). Agricultural-pumpage data 

were obtained primarily from the records of the 

SWRCB, but these records are limited to wells in the 

Los Angeles County and San Bernardino County parts 

of Antelope Valley. Because the SWRCB does not 

require that agricultural pumpage in Kern County be 

reported, data for that part of Antelope Valley are 

nonexistent.

Ground-water pumpage by user is shown in 

tables A1 (public supply) and A2 (agricultural supply). 

Figure A2 shows annual ground-water pumpage for the 

entire period of record (1947–95) in the pumpage 

database. Note that the agricultural pumping presented 

in the data base (figure A2) is less than the agricultural 

pumpage estimated for this study (table 8). Templin 

and others (1995) noted that ground-water pumpage 

reported to the SWRCB may not accurately reflect 

actual pumpage in the valley because of evidence of 

underreporting and overreporting of annual pumpage, 

reporting of identical amounts of pumpage year after 

year, and inaccurate methods of estimating pumpage. 

Also, although agricultural-pumpage data for the Kern 

County part of the study areas does not exist, the data 

reported in table A2 are the best available data at the 

time of this current study. Additional work is needed to 

improve estimates of the quantity and spatial 

distribution of agricultural pumpage.

Figure A2. Ground-water pumpage recorded in the pumpage database for Antelope Valley, California, 1947–95.

YEAR

PUMPAGE, IN ACRE-FEET

300,000

250,000

200,000

150,000

100,000

50,000

0

1945 1945 1955 1960 1965 1970 1975 1980 1985 1990 1995

Ground-water pumpage—

Total

Public supply

Agricultural
Appendix: Water use 1992–95 95

Surface Water

Water supply from surface water comes from 

local surface-water diversions and from imported water 

by way of the California Aqueduct. Imported water 

provides a much larger proportion of surface-water 

supply than local surface-water diversions. The 

availability of imported water is controlled primarily 

by rainfall conditions in northern California. Minimal 

local rainfall and limited storage facilities prevent local 

surface water from becoming a significant component 

of water supply in Antelope Valley.

Local Surface Water

Local surface-water diversions are used for 

public supply and agriculture. Data on local surfacewater diversions for public supply were obtained 

directly from the public supply entities (table A1). 

Palmdale Water District was the only user of local 

surface water for public supply for which data were 

available during 1992–95 (table A1). 

Data on local surface-water diversions for 

agricultural supply (table A2) were obtained from the 

SWRCB, Division of Water Rights. These data and the 

self-supplied surface-water data reported by Templin 

and others (1995) indicate that, for many users, the 

quantity of reported local surface-water use often is 

constant over a period of several years. These constant 

values probably are due to users reporting their waterrights entitlement rather than their actual usage.

Imported Water

Data on the annual quantity of imported water 

was obtained directly from the public entities that 

distribute the water (table A3). The annual quantity of 

water imported by the Antelope Valley–East Kern 

Water Agency (AVEK) represents only those deliveries 

made within the study area defined in this report. 

Imported water averaged about 48,900 acre-ft/yr for 

1992–95 (table A3), which is less than one-third of the 

annual entitlement of 158,000 acre-ft reported by 

Templin and others (1995). Imported water is used for 

both public supply and agriculture.

Reclaimed Wastewater

Data on water supply from reclaimed wastewater 

from the Lancaster and Palmdale Water Reclamation 

Plants (David Lambert, County Sanitations Districts of 

Los Angeles County, written commun., 1996) are 

shown in table A4. These two facilities are the largest 

treatment plants in the study area; there are about 10 

additional treatment plants that treat much smaller 

quantities of wastewater. Templin and others (1995) 

reported that the Lancaster and Palmdale facilities 

accounted for 84 percent of the treated wastewater in 

Antelope Valley in 1990 (a year when data were 

available for all treatment plants). Discharge of treated 

wastewater from the Lancaster Water Reclamation 

Plant used for wetlands (table A4) is slightly higher 

than the wastewater discharge shown in table 1 because 

a small amount of the treated wastewater discharge 

from the Lancaster Water Reclamation Plant is diverted 

to a wildlife pond.

The quantity of reclaimed wastewater available 

for water supply has increased almost every year since 

1975 (fig. A3) due to increases in population and in 

treatment capacities. In 1995, reclaimed wastewater 

represented about 12 percent of the total available 

supply in Antelope Valley. Treated wastewater disposed 

to land surfaces is subject to evapotranspiration and 

infiltration to the ground-water system. There is 

potential for identifying more beneficial uses for this 

component of reclaimed wastewater.
96 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Owing to the depth to the water table and the 

existence of thin aquitards, a time delay is likely 

between the onset of irrigation and the recharge of this 

water to the regional water table. Snyder (1955) stated 

that agricultural recharge probably had reached the 

water table by the early 1950s, but Durbin (1978) 

assumed that no irrigation water had reached the water 

table by 1961. Durbin (1978) based this assumption on 

water-chemistry data collected from wells in 

agricultural areas that showed little change in dissolved 

solids over time. However, it is likely that water had 

reached the water table much sooner than estimated by 

Snyder (1955) or Durbin (1978). Results from a simple 

model of the unsaturated zone indicate that, in a silt 

loam, recharge will infiltrate to a depth of about 120 ft 

approximately 10 years after the water is applied at 

land surface (Alan Flint, U.S. Geological Survey, 

written commun., 1999). 

The largest producers of reclaimed wastewater in 

the study area are the Palmdale Water Reclamation 

Plant and the Lancaster Water Reclamation Plant 

(Templin and others, 1995). Beginning in 1975, 

reclaimed wastewater has been disposed of in ponds or 

on spreading grounds where the water is spread over 

land surface to evaporate or infiltrate below land 

surface. A small amount of reclaimed wastewater is 

reused primarily for agriculture (Templin and others, 

1995). The quantity of disposed wastewater to reach 

the regional water table as recharge was estimated by 

subtracting the estimated evaporation from the quantity 

of reclaimed water that is disposed of in the ponds or 

on spreading grounds. At the Palmdale Water 

Reclamation Plant, reclaimed wastewater is spread on 

approximately 60 acres of land. On the basis of a pan 

evaporation rate of 114 in./yr for Antelope Valley 

(Bloyd, 1967), it was estimated for this study that about 

570 acre-ft/yr is lost to evaporation. At the Lancaster 

Water Reclamation Plant, wastewater is disposed of in 

ponds with an area of approximately 430 acres and 

evaporation was estimated to be about 4,080 acre-ft/yr. 

The estimated evaporation was subtracted from the 

quantity of reclaimed wastewater (David Lambert, 

County Sanitation Districts of Los Angeles County, 

written commun., 1996) to estimate the recharge to the 

water table at these sites (table 1) (fig. 12).

Figure A3. Wastewater use in Antelope Valley ground-water basin, California, 1975–95.

1975

20,000

18,000

16,000

14,000

12,000

10,000

8,000

6,000

4,000

2,000

0

76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 1995

YEAR

WASTEWATER USE, IN ACRE-FEET

Wastewater Use

Land disposal

Agriculture

Wetlands
Appendix: Water use 1992–95 97

Table A1. Water-use information for public water suppliers in Antelope Valley, California, by water-supply sources, 1992–955[Units are in acre-feet. USAF, United States Air Force. —, no data]

Year

Antelope Park Mutual

Water Company

Antelope Valley 

Indian Museum

Antelope Valley Union 

High School District Antelope Valley Water Company Aqua J Mutual Water Company Inc. Averydale Mutual Water Company

Ground

water

Ground

water

Ground

water

Ground

water

Purchased

water Total Ground water Ground water

1992 161.1 0.5 — 569.7 207.0 776.7 53.6 287.81993 149.5 .5 236.0 616.3 176.0 792.3 58.2 296.11994 162.5 .5 238.0 — 171.0 171.0 59.0 317.61995 162.0 .5 — — 171.0 171.0 64.2 312.2

Year

Bleich Flat Mutual 

Water Company

Boeing

(Rockwell) 

USAF Plant 42

Boron Community Service District California Poppy Reserve

Ground

water

Ground

water

Ground

water

Purchased

water Total Ground water Purchased water Total

1992 17.2 149.6 253.0 253.0 506.0 0.5 16.0 16.51993 16.3 80.9 305.0 305.0 610.0 .5 .0 .51994 16.9 129.3 — 548.0 548.0 .8 .0 .81995 21.0 120.5 — 569.0 569.0 .7 .0 .7

Year

Desert Lake Community Services District

Edgemont Acres

Mutual Water

Company

Edwards Air Force Base

 (Main Base)

Edwards Air

Force Base

 (Rocket Site)

Ground

water

Purchased

water Total Purchased water Ground water Purchased water Total Ground water

1992 348.0 24.0 372.0 70.0 4,794.2 0.0 4,794.2 431.81993 353.0 43.0 396.0 53.0 3,498.8 1,345.0 4,843.8 415.01994 — 174.0 174.0 27.0 3,162.3 2,103.0 5,265.3 419.41995 — 314.0 314.0 45.0 3,803.8 1,171.0 4,974.8 435.1

Year

El Dorado Mutual Water Company Evergreen Mutual Water Company Landale Mutual Water Company Land Projects Mutual Water Company Little Baldy Water Company

Ground

water

Purchased

water Total Ground water Ground water Purchased water Total Ground water Surface water

1992 117.4 186.6 304.0 80.0 0.0 1.0 1.0 795.5 21.71993 195.3 114.8 210.1 81.0 220.7 15.0 235.7 782.6 21.71994 39.6 302.0 341.6 82.0 — .0 .0 915.4 21.71995 47.5 297.7 345.2 81.0 — .0 .0 869.7 —
98 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Year

Littlerock Creek Irrigation District Lockhead Martin USAF Plant 42 Los Angeles County Los Angeles County Sheriff Mira Loma Facility

Ground

water 

Surface

water

Purchased

water Total Ground water Purchased water Total Surface water Ground water

1992 1,212.0 1,420 251.0 2,882

— 12.0 12.0 8.7 188.7

1993 1,270.0 1,105 735.0 3,110 74.4 14.3 88.7 8.7 .01994 1,615.0 1,100 1,100.0 3,815 9.3 1.2 10.5 8.7 81.21995 1,630.0 6 480.0 2,116 7.1 .6 7.7 8.7 235.0

Year

Los Angeles County Waterworks District No. 4 Los Angeles County Waterworks District No. 24

Los Angeles County

Waterworks

District No. 27

Ground

water

Purchased

water Total Ground water Purchased water Total Ground water

1992 13,771.8 12,691.0 26,462.8 117.3 219.0 336.3 366.81993 13,368.8 16,765.0 30,133.8 66.3 513.0 579.3 196.11994 14,942.9 16,757.0 31,699.9 4.5 579.0 583.5 426.91995 17,782.6 13,850.0 31,632.6 42.8 495.0 537.8 835.6

Year

Los Angeles County Waterworks District No. 33 Los Angeles County Waterworks District No. 34 Los Angeles County Waterworks District No. 35

Ground

water

Purchased

water Total Ground water Purchased water Total Ground water Purchased water Total

1992 0.0 823.0 823.0 258.5 2,738.0 2,996.5 86.8 161.7 248.51993 .0 991.0 991.0 199.3 3,649.0 3,848.3 26.0 240.7 266.71994 .0 1,049.0 1,049.0 224.0 4,035.0 4,259.0 79.0 217.1 296.11995 .0 776.0 776.0 438.3 4,023.0 4,461.3 82.2 219.4 301.6

Year

Los Angeles County Waterworks District No. 38 Los Angeles County Waterworks District No. 39 Mojave Public Utility District

Ground

water

Purchased

water Total Ground water Purchased water Total Ground water Purchased water Total

1992 200.5 2,068.7 2,269.2 239.0 0.0 239.0 0.0 433.0 433.01993 264.2 2,248.2 2,512.4 267.1 .0 267.1

— 78.0 78.0

1994 1,059.5 1,689.0 2,748.5 228.2 20.5 248.7

— 380.0 380.0

1995 478.8 2,327.8 2,806.6 208.4 .0 208.4

— 118.0 118.0

Table A1. Water-use information for public water suppliers in Antelope Valley, California, by water-supply sources, 1992–95—Continued
Appendix: Water use 1992–95 99

Year

North Edwards

Water District

Northrop

Corporation

B-2 Division

Oak Springs

Valley Water

Company

Palmdale Water District

Ground

water

Ground

water

Ground

water

Ground

water

Surface

water

Purchased 

water Total

1992 0.0 138.6 0.0 10,295.0 3,449.0 3,845.0 17,589.01993 — 136.9 — 8,209.0 2,538.0 10,136.0 20,883.01994 — 128.2 — 11,458.0 1,123.0 8,037.0 20,618.01995 — 117.8 — 11,277.0 3,771.0 6,613.0 21,661.0

Year

Palm Ranch Irrigation District Quartz Hill Water District Rosamond Community Service District

Ground

water

Purchased

water Total Ground water Purchased water Total Ground water Purchased water Total

1992 682.0 679.0 1,361.0 1,028.0 1,646.0 2,674.0 1,090.0 877.7 1,967.71993 1,151.0 175.0 1,326.0 811.8 1,833.0 2,644.8 1,025.0 1,295.1 2,320.11994 962.0 515.0 1,477.0 1,044.6 2,485.0 3,529.6 1,025.0 1,457.7 2,482.71995 758.0 736.0 1,494.0 — 2,098.0 2,098.0 826.0 1,632.6 2,458.6

Year

Saddleback

Butte

State Park

Saint Andrews

Priory San Bernardino County Service Area No. 70L Shadow Acres Mutual Water Company

Purchased

water

Ground

water

Ground

water

Surface

water Total Ground water Purchased water Total

1992 0.9 — 874.3 0.0 874.3 3.7 133.0 136.71993 .9 — 934.9 .0 934.9 4.0 160.0 164.01994 .9 — 678.2 .0 678.2 4.3 154.0 158.31995 .9 321.0 906.8 .0 906.8 4.6 163.0 167.6

Year

Sunnyside Farms Mutual Water Company

Tierra Bonita

Mutual Water 

Company

U.S. Borax and Chemical Corporation

Ground

water

Purchased

water Total Ground water Ground water Purchased water Total

1992 4.6 226.0 230.6 16.9 1,436.3 595.4 2,031.71993 4.6 219.0 223.6 16.9 1,289.0 705.9 1,994.91994 4.6 236.0 240.6 16.9 386.7 1,556.0 1,942.71995 4.6 242.0 246.6 16.9 21.5 2,538.1 2,559.6

Table A1. Water-use information for public water suppliers in Antelope Valley, California, by water-supply sources, 1992–95—Continued
100 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Year

West Side Park Mutual Water Company

West Valley County 

Water District White Fence Farms Mutual Water Company 2

White Fence Farms 

Mutual Water

Company 3

Ground

water

Purchased

water Total Ground water Ground water Purchased water Total Purchased water

1992 230.0 0.0 230.0 141.2 590.4 21.8 612.2 391.01993 176.0 47.0 223.0 141.2 257.5 398.2 655.7 382.01994 96.7 131.2 227.9 165.7 304.9 319.6 624.5 425.01995 238.0 24.0 262.0 153.4 583.5 119.7 703.2 414.0

Year

Total

Grand

total Ground

water

Purchased 

water

Surface 

water

1992 46,129.8 3,575.0 28,319.8 78,024.61993 43,571.7 2,664.0 41,903.1 88,138.81994 46,212.6 1,249.0 43,370.1 90,831.61995 49,333.1 3,897.0 38,958.8 92,188.8

Table A1. Water-use information for public water suppliers in Antelope Valley, California, by water-supply sources, 1992–95—Continued
Appendix: Water use 1992–95 101

Table A2. Water-use information for self-supplied water users in Antelope Valley, California, by water-supply sources, 1992–95[Units are in acre-feet. —, no data

Year

No owner 

recorded Alesso Farms Almondale Farms Antelope Valley Country Club Association of Irrigation Water Users Baicy, John (Rumar)

Ground

 water

Ground

 water

Purchased 

water

Ground 

water

Purchased 

water Total Purchased water Ground water Purchased water Total

1992 84.0 0.0 725.0 208.0 277.0 485.0 27.0 488.0 -488.0 0.01993 160.0 — 1,102.0 14.6 402.0 416.6 31.0 .0 .0 .01994 62.6 — 1,156.0 .0 473.0 473.0 27.0 .0 .0 .01995 .0 — 925.0 .0 417.0 417.0 31.0 .0 333.0 333.0

Year

Ball, 

William and 

Mildred

Beery Ranch Bell, Louis and Sandra Bio Gro Systems, Inc. Biscaichipy Ranch Blalock-Eddy Ranch Co. Blua, Andrew

Surface 

water

Ground 

water

Purchased 

water Total Surface water Purchased water Purchased water Surface water Ground water

1992 22.4 — 0.0 0.0 63.9 0.0 253.0 312 0.01993 22.4 — 845.0 845.0 63.9 .0 431.0 368 —1994 22.4 — 509.0 509.0 63.9 1,112.0 930.0 578 —1995 22.4 — 509.0 509.0 63.9 854.0 947.0 916 —

Year

Bonnie AC Ranch Bozigian Ranch Bryden, Lloyd W. Bushnell, David P. Buchanan, Virginia Calandri Ranch

Ground 

water

Surface 

water Total Ground water Purchased water Total Ground water Ground water Surface water Ground water Purchased water Total

1992 0.0 — 0.0 90.0 -90.0 0.0 0.0 0.0 14.5 — 0.0 0.01993 — — — — .0 .0 — — — — .0 .01994 — — — — .0 .0 — — — — .0 .01995 — — — — 972.0 972.0 — — — — .0 .0

Year

California Portland Cement Company

California 

Resources

Enterprises, Inc.

Calmat Co. Cameo Ranching Co. Carter, Maurice R. Castronova, Daniel Caton, Robert and Richard

Ground 

water

Surface 

water Total Ground water Ground water Ground water Ground water Purchased water Ground water

1992 0.0 — 0.0 0.0 389.5 870.3 0.0 7.0 0.01993 — 166.4 166.4 — 258.9 1,233.9 — 9.0 —1994 — 155.6 155.6 — .0 877.5 — 6.0 —1995 — 159.0 159.0 — 310.3 1,175.9 — 7.0 —
102 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Year

Christoff,

Chris A.

Church of 

Latter Day 

Saints

Circle JM

Ranch

City 

Ranch

Clark, 

Dick

Clayton, 

Richard, M.

Cole, 

J.G., and Sons

Coor-Pender, 

R.L. and 

Ruth B.

Compton,

 Alan and Carol

(previously 

Jerome 

Thompson)

Ground

 water

Ground

 water

Ground

 water

Purchased 

water

Purchased 

water

Ground

water

Ground 

water

Ground

water

Surface

water

1992 128.0 0.0 0.0 0.0 6.0 0.0 0.0 0.0 3.11993 110.0

—

— .0 6.0

—

—

— 3.1

1994 129.0

—

— .0 6.0

—

—

— 3.1

1995 129.0

—

— .0 6.0

—

—

— 3.1

Year

Corpus Cenon, 

and Regina

Davis, 

Shelton

Delia, 

Joseph, E.

Derosier, Lionel 

P. and Particia

Derrick, 

Olin E.

Dustin,

Doug DVM

EPIC/Smith 

Development 

Company

Fabe

Ground

 water Ground water Ground water Ground water Ground water Ground water Ground water Ground water Purchased water

1992 0.0 0.0 34.3 0.0 0.0 0.0 0.0 0.0 0.01993

—

— 45.5

—

—

—

—

— .0

1994

—

— 65.0

—

—

—

—

— .0

1995

—

— 45.5

—

—

—

—

— .0

Year

Freund,

Jerry

Frisella, 

Josef Fuson Gagik Galstian, 

Trustee

Gallin, Leo 

and Ruth 

Morton

Gonzales, 

Avelino

and Hazel

Graham, John 

and others

Grainger, 

Donald L.

Greco, 

Connie Marie

Purchased 

water

Ground

water

Purchased 

water

Ground

water

Ground 

water

Surface 

water

Surface

 water

Ground

water Surface water

1992 1.0 0.0 −230.0 0.0 0.0 0.3 1.1 0.0 0.81993 .0

— .0

—

— .3 1.1

— .8

1994 5.0

— .0

—

— .3 1.1

— .8

1995 6.0

— .0

—

— .4 1.1

— .8

Year

Griffen, Laura Groven, Dennis L. Harter, Leo A. Hathaway Ranch Healy Enterprises Inc. Hecht, Nathaniel Hee, Thornton, and Patti Heiner, David R.

Ground 

water

Ground

 water

Ground 

water

Ground

water

Ground

 water

Surface 

water

Ground

 water

Ground

 water

1992 0.0 600.0 0.0 0.0 0.0

— 0.0 0.0

1993

— 600.0

—

—

—

—

—

—

1994

— 600.0

—

—

—

—

—

—

1995

— 360.0

—

—

— 0.8

—

—

Table A2. Water-use information for self-supplied water users in Antelope Valley, California, by water-supply sources, 1992–95—Continued
Appendix: Water use 1992–95 103

Year

Hicks, 

Lucius B.

Hines, 

Robert G. Hughes

Hughes 

Development 

Corporation

Hughes, Rodger Iarussi, Armando Johnson, Malachi S. Johnston, Arch D. Kadivar, Steve

Ground

 water

Ground

water

Purchased 

water

Purchased

 water

Purchased 

water

Purchased 

water

Ground

water

Ground

water

Ground

water

1992 0.0 0.0 -99.0 0.0 7.0 2.0 0.0 84.9 0.01993 .0 — .0 .0 21.0 7.0 — 84.9 —1994 .0 — .0 .0 23.0 9.0 — 84.9 —1995 20.0 — .0 .0 17.0 57.0 — 94.9 —

Year

Kaufman and Broad Land Company Kellerman, Pat Kelly Ranch Kindig, George B. Kindig, Paul S. Kirby, James and Robert Kleksted Tree Farm

Ground

water

Purchased 

water Total Purchased water Purchased water Ground water Ground water Surface water Purchased water

1992 0.0 0.0 0.0 6.0 0.0 0.0 0.0 2.9 0.01993 — .0 .0 6.0 .0 .0 .0 2.9 .01994 — .0 .0 6.0 .0 .0 .0 1.0 .01995 — 16.0 16.0 7.0 525.0 .0 .0 1.0 .0

Year

Kuete,

Les

Kungl,

Karl

Kyle, 

J.W. and 

G.W.

Lade 

R.M./Hartford 

Management 

Co.

Lake, 

Twyla and 

Larry

Lane, Frank A. Larsen Brothers

Purchased 

water

Ground 

water

Ground 

water

Ground 

water

Ground 

water

Ground 

water

Purchased 

water Total Ground water Purchased water Total

1992 6.0 15.0 6,639.0 0.0 12.0 397.0 31.0 428.0 0.0 0.0 0.01993 6.0 15.0 6,359.8 — 686.0 397.0 43.0 440.0 — .0 .01994 6.0 .0 5,343.0 — 15.0 300.0 58.0 358.0 — .0 .01995 6.0 .1 7,108.0 — 2,744.0 300.0 39.0 339.0 — .0 .0

Year

Leona Valley 

Estates Ltd.

Leviste 

Management 

Systems

Littlerock 

Aggregate 

Company 

Llarena, Albert

Los Angeles 

Department of 

Airports

Los Angeles 

Firemen’s Relief 

Assoc.

Lowe, 

John and 

Becky

Margaretten, 

Joel

Montemayer, 

Abel and

 others

Purchased 

water

Ground

water

Ground

 water

Ground

 water

Ground

water

Ground

water

Surface

 water

Surface

water

Surface

water

1992 4.0 0.0 305.0 0.0 5,097.5 0.0 2.2 19.7 5.11993 .0 .0 305.0 .0 6,376.0 — 2.2 19.7 5.11994 .0 .0 270.0 .0 5,723.0 3,295.0 2.2 19.7 5.11995 .0 .0 270.0 .0 6,445.0 — 2.2 19.7 5.1

Table A2. Water-use information for self-supplied water users in Antelope Valley, California, by water-supply sources, 1992–95—Continued
104 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Year

McCormick, 

Raymond W.

Mescal Creek 

Water, Inc.

Miccolis, 

F.P. Adele Bruno Milford, Terry Miller, Keith Mitchel and Gunning Monsello, Andrew Morgan, Carlos, Estate of Morris,

Wayne F. and 

Annette L.

Ground 

water

Surface

water

Ground 

water

Purchased 

water

Purchased 

water

Purchased 

water

Ground

 water

Ground

water

Surface 

water

1992 0.0 915.8 0.0 6.0 11.0 46.0 0.0 5.0 1.61993

— 915.8

— 6.0 10.0 482.0

— 2.0

—

1994

— 1,220.7

— 6.0 11.0 826.0

— .0

—

1995

— 1,220.7

— 6.0 9.0 851.0

— .0

—

Year

Mountain Glen 

Ranch

Mountain 

High—

Holiday Hill 

Company

Nakasone 

Development 

Company

Nebeker Ranch Nishimoto, Jimmie M. Nishimoto, Roy Oakwood Enterprises Ordway, Ben

Ground

 water

Ground 

water

Ground

 water

Ground 

water

Reclaimed 

water Total Ground water Ground water Surface water Surface water

1992 0.0 0.0 0.0 323.0 3,640.0 3,963.0 0.0 0.0 6.1 29.01993

— 0.0

— 259.0 2,997.0 3,256.0

—

— 6.1 29.0

1994

— 0.0

— 286.0 3,711.0 3,997.0

—

— 6.1 29.0

1995

— 0.0

— 240.0 3,226.0 3,466.0

—

— 6.1 29.0

Year

Pablo, 

Mr. and Mrs. 

Pastor

Peachland Farms Piani, Gino Poncedeleon, Modesto Portanova Pratt, Dr. W.H. Proctor, Carl Pulsipher Enterprises

Ground

 water

Purchased 

water

Ground

 water

Purchased 

water

Purchased

 water

Ground

 water

Ground 

water

Purchased 

water

1992 0.0 288.0 0.0 6.0 0.0 0.0 0.0 8.01993

— 264.0

— 6.0 .0

— .0 9.0

1994

— 436.0

— 7.0 .0

— .0 12.0

1995

— 339.0

— 9.0 .0

— .0 11.0

Year

Punchbowl

Canyon Water 

Association

R and M 

Ranch, Inc. RR Ranch Rabinov, David MD Rancho Corona Del Valle Corporation Rancho Vista Development Reca, Dominique Retlaw Enterprises Incorporated

Surface

 water

Ground

 water

Purchased

 water

Ground

 water

Surface

 water

Purchased

 water

Ground 

water Ground water

1992 27.5 3,950.0 479.0 0.0 31.5 0.0 0.0 6,914.01993 27.5 3,567.0 1,194.0

— 31.5 .0

— 1,500.0

1994 27.5 2,837.0 1,357.0

— 31.5 .0

— 2,250.0

1995 27.5 3,674.0 919.0

— 31.5 .0

— 1,800.0

Table A2. Water-use information for self-supplied water users in Antelope Valley, California, by water-supply sources, 1992–95—Continued
Appendix: Water use 1992–95 105

Year

Ritter and Godde Robbins, David Robinson, F. Willard and others Rosen, Sandee S&D Sasland Farms Spivak-Brown

Ground

 water

Purchased 

water Total Purchased water Surface water Purchased water Purchased water Ground water

1992 2,275.1 1,124.0 3,399.1 8.0 — 6.0 0.0 0.01993 1,139.3 2,316.0 3,455.3 7.0 — 6.0 .0 —1994 415.6 2,841.0 3,256.6 6.0 — 1.0 .0 —1995 1,993.0 2,611.0 4,604.0 8.0 — 4.0 .0 —

Year

Schnaidt, Harold Searcy, Travis Seiki Investment Corporation Silva, Don Simi, Roy Southern California Edison Company

Ground 

water

Purchased

 water Total Purchased water Ground water Purchased water Purchased water Gro water

1992 — 65.0 65.0 6.0 0.0 10.0 0.0 10.11993 — 56.0 56.0 7.0 — 11.0 .0 11.21994 — 81.0 81.0 13.0 — 11.0 .0 12.71995 — 68.0 68.0 8.0 — 10.0 .0 .0

Year

Stevens, 

William E. Stoner Sundown Ranch Company Tapia Brothers Taunton, Windsor P. Tejon Ranch Traweek, S.V.

Ground

 water

Purchased 

water

Ground

water

Purchased

water

Ground

water

Ground

water

Purchased 

water Total Ground water

1992 0.0 0.0 0.0 402.0 0.0 1,006.0 −230.0 776.0 0.01993 — .0 — 238.0 — — .0 .0 —1994 — .0 — 205.0 — — .0 .0 —1995 — .0 — 795.0 — — .0 .0 —

Year

U.S. Forest Service,

Angeles National Forest

Union Wilshire 

Incorporated

Unnamed spring 

group

Vandereyk Vaught, Amelia Wade, Thomas H. Ward, J.W./Lyman Champlain

Ground

 water

Surface

 water Total Ground water Surface water Purchased water Purchased water Ground water Ground water

1992 0.0 24 24 0.0 18.1 0.0 6.0 0.0 0.01993 — 24 24 — 18.1 .0 6.0 .0 —1994 — 24 24 — 18.1 .0 7.0 .0 —1995 — 2.5 2.5 — 18.1 .0 6.0 3.3 —

Table A2. Water-use information for self-supplied water users in Antelope Valley, California, by water-supply sources, 1992–95—Continued
106 Simulation of Ground-Water Flow and Land Subsidence in the Antelope Valley Ground-Water Basin, California

Year

Weaver

White,

J.F. Jr., H.B.,

and D.B.

White, 

James B. 

or Dee Ann

White, 

Michael G.

White, 

Richard A.

Williams, 

Claude Wilmar Farms Zamrzla, Johnny

Purchased

 water

Surface

 water

Ground 

water

Ground

 water

Ground 

water

Ground

 water

Purchased

 water

Ground

 water

1992 0.0 0.8 0.0 0.0 0.0 0.0 0.0 0.01993 .0

— .0

— .0

— 1,157.6

—

1994 .0

— .0

— .0

— 2,139.0

—

1995 .0

— 24.0

— 5.7

— 2,119.0

—

Year

Total

Grand total

Ground 

water

Surface 

water

Purchased 

water

1992 29,925.7 888.5 2,692.0 33,506.21993 23,015.1 .0 8,690.6 31,705.71994 22,437.3 .0 12,833.0 35,270.31995 26,613.7 .0 13,447.0 40,060.7

Table A2. Water-use information for self-supplied water users in Antelope Valley, California, by water-supply sources, 1992–95—Continued
Appendix: Water use 1992–95 107

Table A3. Deliveries of imported water to Antelope Valley from the California Aqueduct, 1992–95 

[Units are in acre-feet per year]

1Russell Fuller, Antelope Valley–East Kern Water Agency, written commun., 1998. 2Brad Jones, Littlerock Creek Irrigation District, written commun., 1996. 3Matt Knudson, Palmdale Water District, written commun., 1996.

Table A4. Use of reclaimed wastewater in Antelope Valley, California, 1992–95

[Units are in acre-feet. Data from David Lambert (County Sanitation Districts of Los Angeles County, written commun., 1996)]

Year

Antelope Valley–

East Kern 

Water Agency1

Littlerock Creek

Irrigation District2 Palmdale Water District3 Total

1992 27,663 251 3,845 31,759

1993 40,928 735 10,136 51,799

1994 49,536 1,100 8,037 58,673

1995 46,091 480 6,613 53,184

Year

Lancaster Water Reclamation Plant Palmdale Water Reclamation Plant

Wetlands Irrigation Total Land disposal Irrigation Total

1992 3,520 3,640 7,160 6,150 21 6,170

1993 5,280 3,000 8,280 7,080 42 7,120

1994 5,110 3,700 8,810 7,480 51 7,530

1995 7,140 3,225 10,360 8,070 67 8,140