U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the Coachella Valley Water District

Detection and Measurement of Land Subsidence Using 

Global Positioning System Surveying and Interferometric 

Synthetic Aperture Radar, Coachella Valley, California, 

1996–2005

Scientific Investigations Report 2007–5251

Version 2.0, June 2013
ii

Detection and Measurement of Land 

Subsidence Using Global Positioning 

System Surveying and Interferometric 

Synthetic Aperture Radar, Coachella Valley, 

California, 1996–2005

By Michelle Sneed and Justin T. Brandt

Prepared in cooperation with Coachella Valley Water District

Scientific Investigations Report 2007–5251

Version 2.0, June 2013

U.S. Department of the Interior

U.S. Geological Survey
iii

U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

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

Revised: 2013 

For product and ordering information:

World Wide Web: http://www.usgs.gov/pubprod

Telephone: 1-888-ASK-USGS

For more information on the USGS--the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment:

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

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

reproduce any copyrighted materials contained within this report.

Suggested reference:

Sneed, Michelle, and Brandt, Justin, 2007, Detection and Measurement of Land Subsidence Using Global 

Positioning System Surveying and Interferometric Synthetic Aperture Radar, Coachella Valley, California, 

1996–2005: U.S. Geological Survey Scientific Investigations Report 2007–5251, 30 p. 
iv

Contents

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

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

Purpose and Scope ..............................................................................................................................2

Description of Study Area ...................................................................................................................2

Previous Land-Subsidence Studies...................................................................................................4

Geohydrologic Setting...................................................................................................................................4

Mechanics of Pumping-Induced Land Subsidence.................................................................................6

Global Positioning System (GPS) Surveys.................................................................................................6

Land-Subsidence Monitoring Network.............................................................................................6

Determination of Ellipsoid Heights ....................................................................................................8

1996 GPS Survey ..........................................................................................................................8

1998 GPS Survey ..........................................................................................................................8

2000 GPS Survey ..........................................................................................................................9

2005 GPS Survey ..........................................................................................................................9

GPS Results............................................................................................................................................9

Ground-Water Levels .........................................................................................................................14

InSAR Methodology.....................................................................................................................................14

InSAR Results......................................................................................................................................22

Land Subsidence in the Palm Desert Area (Area 1) ............................................................22

Land Subsidence in the Indian Wells Area (Area 2)............................................................24

Land Subsidence in the La Quinta Area (Area 3) .................................................................24

Deformation in the Indio-Coachella Area..............................................................................24

Ground-Water Levels ................................................................................................................25

Comparison of InSAR and GPS Results ...................................................................................................25

Future Monitoring ........................................................................................................................................28

Summary........................................................................................................................................................28

Acknowledgments ......................................................................................................................................29

References....................................................................................................................................................29
v

Figures

Figure 1. Map showing location of study area and of six Continuous Global Positioning

System (CGPS) stations in or near Coachella Valley, California. ..................... 3

Figure 2. Map showing generalized geology of the Coachella Valley, California................ 5

Figure 3. Map showing network of Global Positioning System (GPS) stations and wells

used to monitor vertical changes in land surface and ground-water levels,

respectively, in the southern Coachella Valley, California. ........................... 7

Figure 4. Hydrographs showing (A) water-surface elevations for selected wells (between

1995 and 2005), and ellipsoid-height changes (relative to the first measurement)

for geodetic monuments measured at least twice, and (B) water-surface

elevations for a subset of the wells in A for 1925-2005. ................................. 11

Figure 5. Image showing land-surface features, consolidated rock, Global Positioning

System (GPS) stations, two Continuous Global Positioning System (CGPS)

stations, three areas of subsidence, and selected roads and production wells,

Coachella Valley, California. ............................................................... 15

Figure 6. Areas of subsidence, linearities at subsidence margins, consolidated rock, GPS

stations, and two CGPS stations in the Coachella Valley, California, for November

30, 2003, through May 23, 2004, (A) as shown on the interferogram, and (B) as

shown by subsidence contours interpreted from the interferogram in A............. 16

Figure 7. Areas of subsidence, consolidated rock, GPS stations, and two CGPS stations in

the Coachella Valley, California, for August 1, 2004, through September 5, 2004,

(A) as shown on the interferogram, and (B) as shown by subsidence contours

interpreted from the interferogram in A. ................................................ 18

Figure 8. Areas of subsidence, consolidated rock, GPS stations, and two CGPS stations in

the Coachella Valley, California, for October 26, 2003, through June 12, 2005, (A)

as shown on the interferogram, and (B) as shown by subsidence contours

interpreted from the interferogram in A. ................................................ 20

Figure 9. Hydrographs showing (A) water-surface elevations for selected production 

wells, and InSAR timeseries showing land subsidence for 5/7/2003–9/25/2005, 

and (B) water-surface elevations for the same production wells for 1970–2005 

in the three InSAR-detected land subsidence areas in the Coachella Valley, 

California. .................................................................................... 26

Tables

Table 1. Horizontal positions and ellipsoid heights for 1996, 1998, 2000, and 2005, and 

ellipsoid-height changes relative to the first measurement of geodetic 

monuments in the Coachella Valley, California........................................... 10

Table 2. Vertical change measured using interferometric synthetic aperture radar 

(InSAR) for 3 areas in the Coachella Valley, California, 2003–2005. .................. 23
vi

Conversion Factors

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in)

millimeter (mm) 0.03937 inch (in)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2

) 0.3861 square mile (mi2)

Rate

meter per day (m/d) 3.281 foot per day (ft/d)

meter per year (m/yr) 3.281 foot per year (ft/yr) 

millimeter per day (mm/d) 0.003281 foot per day (ft/d)

millimeter per month (mm/mo) 0.003281 foot per month (ft/mo)

millimeter per year (mm/yr) 0.03937 inch per year (in/yr) 

kilometer per hour (km/h) 0.6214 mile per hour (mi/h)

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

 °F=(1.8×°C)+32

Vertical displacements determined by InSAR and coordinates determined by Global Positioning 

System (GPS) surveying generally are reported in metric units. The industry standard for 

GPS usage is that field measurements and subsequent computations, including standard 

error determinations, are done in the metric system. The use of dual units in this report is 

intended to facilitate application of the data by maintaining the integrity of the original units of 

measurement for GPS surveying.

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 Sates and Canada, formerly called Sea Level Datum of 1929.

Ellipsoid heights: In this report, Global Positioning System (GPS) measurements of horizontal 

coordinates and ellipsoid heights are based on the North American Datum of 1983 (NAD83).
vii

Abbreviations and Acronyms

Caltrans California Department of Transportation

CGPS Continuous Global Positioning System

CVWD Coachella Valley Water District

DEM digital elevation model

ESA European Space Agency

GPS Global Positioning System

IGS International GPS Service

InSAR Interferometric Synthetic Aperture Radar

NGS National Geodetic Survey

SAR Synthetic Aperture Radar

SCIGN Southern California Integrated GPS Network

SOPAC Scripps Orbit and Permanent Array Center

UNAVCO University NAVSTAR (Navigation Signal Timing and Ranging) Consortium

USGS United States Geological Survey
viii

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 005S006E23K002S. In this report, well numbers are abbreviated and written 5S/6E-23K2. 

Wells in the same township and range are referred to only by their section designation, 23K2. 

The following diagram shows how the number for well 5S/6E-23K2 is derived.

R7ER6E R8E

naidireM

olbaiD tnuoM 

 T4S

 T5S

 T6S

RANGE

PIHSNWOT

 R1W R1E

27

R6E

T5S

Well-numbering diagram

3456 2 1

7

18 13

8 9 10 11 12

17 16 15 14

19 24

30 25

31 36

20 21 22 23

262829

32 33 34 35

SECTION 23

ACD

E F G H

JKLM

N P Q R

B

5S/6E-23K2
ix

This page intentionally left blank.
Abstract 

Land subsidence associated with ground-water-level 

declines has been investigated by the U.S. Geological Survey 

in the Coachella Valley, California, since 1996. Ground 

water has been a major source of agricultural, municipal, and 

domestic supply in the valley since the early 1920s. Pumping 

of ground water resulted in water-level declines as large 

as 15 meters (50 feet) through the late 1940s. In 1949, the 

importation of Colorado River water to the southern Coachella 

Valley began, resulting in a reduction in ground-water 

pumping and a recovery of water levels during the 1950s 

through the 1970s. Since the late 1970s, demand for water in 

the valley has exceeded deliveries of imported surface water, 

resulting in increased pumping and associated ground-waterlevel declines and, consequently, an increase in the potential 

for land subsidence caused by aquifer-system compaction.

Global Positioning System (GPS) surveying and 

interferometric synthetic aperture radar (InSAR) methods were 

used to determine the location, extent, and magnitude of the 

vertical land-surface changes in the southern Coachella Valley. 

GPS measurements made at 13 geodetic monuments in 1996 

and in 2005 in the southern Coachella Valley indicate that the 

elevation of the land surface had a net decline of 124 to 9 mm 

±54 mm (0.41 to 0.03 ft ±0.18 ft) during the 9-year period. 

Changes at 9 of the 13 monuments exceeded the maximum 

expected uncertainty of ±54 mm (±0.18 ft) at the 95-percent 

confidence level, indicating that subsidence occurred at 

these monuments between June 1996 and August 2005. GPS 

measurements made at 20 geodetic monuments in 2000 and 

in 2005 indicate that the elevation of the land surface changed 

–192 to +51 mm ±36 mm (–0.63 to +0.17 ft ±0.12 ft) during 

the 5-year period. Changes at 6 of the 20 monuments exceeded 

the maximum expected uncertainty of ±36 mm (±0.12 ft) at 

the 95-percent confidence level—subsidence occurred at five 

monuments and uplift occurred at one monument between 

August 2000 and August 2005. GPS measurements at two 

of the five subsiding monuments for which subsidence rates 

could be compared indicate that subsidence rates decreased 

during this period compared with subsidence rates before 

2000. 

InSAR measurements made between May 7, 2003, and 

September 25, 2005, indicate that land subsidence, ranging 

from about 75 to 180 millimeters (0.25 to 0.59 foot), occurred 

in three areas of the Coachella Valley: near Palm Desert, 

Indian Wells, and La Quinta; the equivalent subsidence 

rates range from about 3 to more than 6 mm/month (0.01 to 

0.02 ft/month). The subsiding areas near Palm Desert, Indian 

Wells, and La Quinta were previously identified using InSAR 

measurements for 1996–2000, which indicated that about 35 

to 150 mm (0.11 to 0.49 ft) of subsidence occurred during the 

four-year period; the equivalent subsidence rates range from 

about 1 to 3 mm/month (0.003 to 0.01 ft/month). Comparison 

of the InSAR results indicates that subsidence rates have 

increased 2 to 4 times since 2000 in these three areas. 

Water-level measurements made at wells near the 

subsiding monuments and in the three subsiding areas 

generally indicated that the water levels fluctuated seasonally 

and declined annually between 1996 and 2005; some water 

levels in 2005 were at the lowest levels in their recorded 

histories. The coincident areas of subsidence and declining 

water levels suggest that aquifer-system compaction may be 

causing subsidence. If the stresses imposed by the historically 

lowest water levels exceeded the preconsolidation stress, the 

aquifer-system compaction and associated land subsidence 

may be permanent. Although the localized character of 

the subsidence signals is typical of the type of subsidence 

characteristically caused by localized ground-water pumping, 

the subsidence may also be related to tectonic activity in the 

valley.

Detection and Measurement of Land Subsidence Using 

Global Positioning System Surveying and Interferometric 

Synthetic Aperture Radar, Coachella Valley, California, 

1996–2005

By Michelle Sneed and Justin T. Brandt
2 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005

Introduction 

Ground water has been a major source of agricultural, 

municipal, and domestic water supply in Coachella Valley, 

California (fig. 1), since the early 1920s. Pumping of ground 

water resulted in water-level declines as large as 15 m 

(50 ft) between the early 1920s and late 1940s. In 1949, the 

importation of Colorado River water through the Coachella 

Branch of the All-American Canal to the southern Coachella 

Valley began. As a result of the importation of surface water, 

pumping of ground water decreased in the southern Coachella 

Valley during the 1950s through the 1970s, and water levels 

in some wells in the lower valley recovered as much as 15 m 

(50 ft). Since the late 1970s, however, the demand for water 

in the southern Coachella Valley has exceeded the deliveries 

of imported surface water, pumping has increased, and water 

levels have again declined. By 2005, water levels in many 

wells in the southern Coachella Valley had declined 15 to 

30 m (50 to 100 ft) and water levels in some wells were at 

their lowest recorded levels.

Declining water levels can contribute to, or induce, land 

subsidence in aquifer systems that consist of a significant 

fraction of unconsolidated fine-grained sediments (silts and 

clays). Ikehara and others (1997) reported that as much as 

150 mm ± 90 mm (0.5 ft ± 0.3 ft) of subsidence occurred 

in the southern parts of the Coachella Valley between 1930 

and 1996. Land subsidence can disrupt surface drainage; 

cause earth fissures; and damage wells, buildings, roads, and 

utility infrastructure. A large earth fissure was discovered in 

1948 about 3 km (2 mi) north of Lake Cahuilla in La Quinta. 

Because subsidence had not been documented in the southern 

parts of the Coachella Valley prior to the report by Ikehara and 

others (1997), it is not known if this fissure formed in response 

to differential land subsidence during the earlier period (early 

1920s–late 1940s) of ground-water-level declines. However, 

fissuring is recurring in this area (Clay Stevens, TerraPacific 

Consultants, Inc., written commun., 2006). Subsidencerelated earth fissures and reactivated surface faults have been 

identified in many other ground-water basins in the western 

United States (Holzer, 1984).

The Coachella Valley Water District (CVWD) works 

cooperatively with local stakeholders to manage the water 

supply for a large part of the Coachella Valley (fig. 1). 

Because of the potential for ground-water pumping to cause 

land subsidence, the CVWD entered into a cooperative 

agreement with the U.S. Geological Survey (USGS) to 

monitor vertical changes in land surface to determine if 

land subsidence was occurring in the Coachella Valley. In 

1996, the USGS, in cooperation with CVWD, established a 

geodetic network of monuments to monitor vertical changes 

in land surface in the southern Coachella Valley using Global 

Positioning System (GPS) surveys and to establish baseline 

values for comparisons with results of future surveys. 

The geodetic network needs to be surveyed intermittently to 

determine the distribution and amount of land subsidence. 

In addition, interferometric synthetic aperture radar (InSAR) 

data collected since 1996 have been used to detect and 

quantify land subsidence in areas removed from the geodetic 

monuments.

Purpose and Scope

The objectives of this study are to detect and quantify 

land subsidence that has occurred in the Coachella Valley 

from 1996 through 2005 by completing GPS surveys at the 

established geodetic network of monuments and by using 

InSAR data. This report presents the results and interpretations 

of GPS data collected at the monuments in the monitoring 

network during surveys in 1996, 1998, 2000, and 2005, and 

also of spatially detailed maps of vertical land-surface changes 

generated using InSAR data collected between 1996 and 2005. 

The InSAR-generated maps extend from near Palm Springs 

to near the Salton Sea (fig. 1). Data showing ground-waterlevel change during 1996–2005 were examined and compared 

with the GPS measurements and the InSAR-generated maps 

to determine if the vertical changes in land surface may be 

related to the changes in ground-water levels.

Description of Study Area

The Coachella Valley is a 100-km (65 mi) long, 

northwest-trending valley in southeastern California (fig. 1). 

The valley covers about 1,000 km2 (400 mi2) (California 

Department of Water Resources, 1964) and includes the cities 

of Cathedral City, Coachella, Desert Hot Springs, Indio, La 

Quinta, Palm Desert, Palm Springs, and Rancho Mirage. 

The valley is bordered by the San Jacinto and Santa Rosa 

Mountains on the west, the San Bernardino and the Little 

San Bernardino Mountains on the north, the Cottonwood 

Mountains and the Mecca Hills on the east, and the Salton Sea 

on the south (fig. 1). The Coachella Valley is drained primarily 

by the Whitewater River, which flows into the Whitewater 

Stormwater Channel and eventually discharges into the 

Salton Sea (fig. 1). Land-surface elevations vary from more 

than 70 m (230 ft) below sea level at the Salton Sea to more 

than 3,000 m (10,000 ft) above sea level at the peaks of the 

surrounding mountains.

The climate of the Coachella Valley floor is arid. Average 

annual rainfall ranges from 80 mm (3 in) on the valley floor 

to more than 760 mm (30 in) on the crests of the mountains 

to the west and north of the valley (California Department of 

Water Resources, 1964). Temperatures range from about 50oC 

(120oF) on the valley floor in the summer to below 0oC (32oF) 

in the surrounding mountains in the winter.
Introduction 3

Figure 1. Map showing location of study area and of six Continuous Global Positioning System (CGPS) stations in or near Coachella 

Valley, California.

 San

Francisco

 Los

Angeles

EXPLANATION

Continuous Global Positioning System (CGPS) station and name

 Area of 

enlargement

Colorado 

 River

Cottonwood Mts

San Jacinto Mts

Little San Bernardino Mts

San Bernardino Mts

San Gorgonio Pass

PIN1

COTD

Point 

Happy

COACHELLA BRANCH OF

THE ALL-AMERICAN CANAL

 

WHITEWATER

STORMWATER

CHANNEL

Yucaipa

Indio

Durmid

DHLG

TMAP

DHLG

Salton Sea

Base prepared by U.S. Geological Survey 

from digital elevation data, 1:1,000,000, 1987 

North American Datum 1927

0

0

50 MILES

50 KILOMETERS

 Coachella Valley

Water District boundary

 Lake 

Cahuilla

117°00' 116°30' 116°00' 115°30'

33°00'

33°30'

34°00'

C A L I F O R N I A 

111

Santa Rosa Mts

Palm

Springs

Indian 

Wells

Thermal

10

Whitewater

 River

Palm 

Desert

Cathedral

 City Coachella

Mecca Hills

WIDC

 La 

Quinta

Coachella

Valley

CRFP

Desert Hot 

Springs

Rancho 

Mirage 10

111

111

Mecca

86

86

Indio Hills
4 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005

Previous Land-Subsidence Studies

This study is the fourth in a series of Coachella Valley 

land-subsidence studies that have been completed by the 

USGS in cooperation with CVWD. Ikehara and others (1997) 

documented the development of the geodetic monitoring 

network and areas of possible land subsidence in Coachella 

Valley by comparing historical leveling measurements with 

GPS surveying measurements made in 1996. The vertical 

changes in land surface between 1996 and the earliest 

measurements at monuments in the monitoring network do 

not exceed 150 mm (0.5 ft) (Ikehara and others, 1997). The 

range of uncertainty (±90 mm or ±0.3 ft) of these calculated 

vertical changes in land surface, however, is large because 

the historical leveling surveys were done at different times 

and sometimes by different agencies using different methods. 

Furthermore, the methods used for the leveling surveys 

had different standards of accuracy and the networks were 

of different geographic extents (Ikehara and others, 1997). 

Sneed and others (2001) reported that GPS measurements 

indicated small amounts of subsidence between 1996 and 

1998 at some monuments in the monitoring network; Sneed 

and others (2002) reported that GPS measurements indicated 

most monuments were fairly stable between 1998 and 2000. 

Sneed and others (2001, 2002) also used InSAR to detect and 

quantify land subsidence throughout much of the Coachella 

Valley. InSAR measurements made between 1996 and 2000 

indicated that as much as 150 mm (0.49 ft) of land subsidence 

occurred in areas near Palm Desert, Indian Wells, and La 

Quinta (Sneed, 2001, 2002).

Geohydrologic Setting

The Coachella Valley is the northernmost extent of 

the Salton Trough, which is the landward extension of a 

ridge/transform fault system (the East Pacific Rise) of the 

Gulf of California (McKibben, 1993). Near the end of the 

Miocene epoch, a spreading center separating the western 

Farallon plate from the eastern Pacific plate was obliquely 

subducted under the North American continent (McKibben, 

1993). The modern Gulf of California and the Salton Trough 

formed about 12 million years ago during a period when 

subduction ceased and when the formation of an inland belt 

of east-west extension, alkali basalt volcanism, and crustalspreading-induced subsidence and basin sedimentation 

began (McKibben, 1993). Prior to about 6 million years ago, 

the shear zone constituting the principal tectonic boundary 

between the Pacific and North American plates appears to 

have shifted about 250 km (155 mi) inland into this belt, 

initiating the formation of the modern Gulf of California and 

the Salton Trough (McKibben, 1993). As the Salton Trough 

opened, it was filled with sediment from the delta of the 

Colorado River. The river has been building its delta from 

the east into the trough since about 5 million years ago, and 

sedimentation has apparently kept pace with the crustalspreading induced subsidence (McKibben, 1993). The relation 

between subsidence that has occurred on a geologic time scale, 

and vertical land-subsidence changes measured during this 

study are unknown.

The Coachella Valley is filled with as much as 3,700 m 

(12,000 ft) of sediments; the upper 610 m (2,000 ft) are waterbearing (California Department of Water Resources, 1979). 

In this report, the water-bearing deposits are referred to as the 

aquifer system, which consists of a complex unconsolidated 

to partly consolidated assemblage of gravel, sand, silt, and 

clay of alluvial and lacustrine origins (fig. 2). Sediments 

tend to be finer grained (contain more silt and clay) in the 

southern part of the valley than in the northern part because 

of the greater depositional distance from mountain runoff and 

from lacustrine deposition from ancient Lake Cahuilla. In 

the southern Coachella Valley, the aquifer system consists of, 

from top to bottom: a semiperched zone that is fairly persistent 

southeast of Indio; an upper aquifer; a confining layer; and 

a lower aquifer (California Department of Water Resources, 

1964, 1979).

The near-surface semiperched zone overlies the upper 

aquifer southeast of Indio and consists of silts, clays, and 

fine sand. The semiperched zone is as much as 30 m (100 ft) 

thick and generally is an effective barrier to deep percolation 

(California Department of Water Resources, 1964, 1979). The 

upper aquifer is present throughout the Coachella Valley and 

consists of unconsolidated and partly consolidated silty sands 

and gravels with interbeds of silt and clay. In general, the 

upper aquifer is 45 to 90 m (150 to 300 ft) thick. The aquifer 

is unconfined except where it is overlain by the semiperched 

zone, southeast of Indio. In the southern Coachella Valley, 

the upper aquifer is separated from the lower aquifer by a 

confining layer of silt and clay that is 30 to 60 m (100 to 

200 ft) thick. The lower aquifer is the most productive source 

of ground water in the southern Coachella Valley; it consists of 

unconsolidated and partly consolidated silty sands and gravels 

with interbeds of silt and clay. The top of the lower aquifer 

is about 90 to 180 m (300 to 600 ft) below land surface. 

Available data indicate that the lower aquifer is at least 150 m 

(500 ft) thick and may be as much as 600 m (2,000 ft) thick 

(California Department of Water Resources, 1964, 1979). 

Geologic structures in the Coachella Valley have 

a marked influence on the occurrence and movement 

of ground water. The principal structural features of 

Coachella Valley are faults and fault-related drag and 

compressional folds. The most notable fault system is the 

northwest-trending San Andreas Fault Zone that flanks 
Geohydrologic Setting 5

the eastern side of the valley (fig. 2). Although movement 

within the San Andreas Fault Zone is predominantly right 

lateral (across the fault, movement is to the right), vertical 

displacement has downdropped the southwest block 

(California Department of Water Resources, 1964). The faults 

have either juxtaposed consolidated rocks against partly 

consolidated or unconsolidated water-bearing deposits or 

displaced preferential flow paths in the partly consolidated or 

unconsolidated water-bearing deposits. This juxtaposition and 

displacement, in conjunction with cementation, compaction, 

and extreme deformation of water-bearing deposits adjacent 

to faults, can create low-permeability zones that can act as 

barriers to ground-water flow. 

Figure 2. Map showing generalized geology of the Coachella Valley, California.

0 5

0 5 10 KILOMETERS

10 MILES

 San

Francisco

 Los

Angeles

SALTON SEA

Unconsolidated deposits 

Fault

Partly consolidated deposits 

Consolidated rock 

EXPLANATION

SAN

JACINTO

MOUNTAINS

SAN BERNARDINO MOUNTAINS

SANTA

ROSA

MOUNTAINS

LITTLE

SAN

BERNARDINO

MOUNTAINS

C O A C H E L L A

V A L L E Y

116°45'

34°00'

33°45'

33°30'

116°30'

116°15'

116°00'

Palm

Desert

Palm

Springs

La

Quinta

Indio

Mecca

Coachella

Thermal

COACHELLA BRANCH OF THE ALL-AMERICAN CANAL

Aquifer system

Indian 

Wells

 Lake 

Cahuilla

86

111

111

San Andreas Fault Zone

10

INDIO

HILLS
6 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005

Mechanics of Pumping-Induced Land 

Subsidence

Land subsidence is known to occur in valleys containing 

aquifer systems that are, at least in part, made up of finegrained sediments and that have undergone extensive groundwater development. The pore structure of a sedimentary 

aquifer system is supported by the granular skeleton of the 

aquifer system and the pore-fluid pressure of the ground water 

that fills the intergranular pore space (Meinzer, 1928). When 

ground water is withdrawn in quantities that result in reduced 

pore-fluid pressures and water-level declines, the reduction 

of the pore-fluid-pressure support increases the intergranular 

stress, or effective stress, on the skeleton. A change in 

effective stress deforms the skeleton—an increase in effective 

stress compresses it and a decrease in effective stress causes 

it to expand. The vertical component of this compression 

sometimes results in nonrecoverable compaction of the aquifer 

system and land subsidence. An aquifer-system skeleton 

that primarily consists of fine-grained sediments, such as silt 

and clay, is much more compressible than one that primarily 

consists of coarse-grained sediments, such as sand and gravel. 

Inelastic (nonrecoverable) compaction of coarse-grained 

sediment is negligible.

Aquifer-system deformation is elastic (recoverable) if 

the effective stress imposed on the skeleton is smaller than 

any previous effective stress (Leake and Prudic, 1991). 

The largest historical effective stress imposed on an aquifer 

system—sometimes as a result of the lowest ground-water 

level—is the “preconsolidation stress.” If a stress imposed 

on the skeleton is greater than the preconsolidation stress, 

the pore structure of the granular matrix of the fine-grained 

sediments is rearranged; this new configuration results in 

a reduction of pore volume and, thus, inelastic (largely 

irreversible) compaction of the aquifer system. Furthermore, 

the compressibility of the fine-grained sediments, and 

any resulting compaction under stresses greater than the 

preconsolidation stress, are 20 to more than 100 times greater 

than they are under stresses less than the preconsolidation 

stress (Riley, 1998). 

For an aquifer-system skeleton that contains an 

appreciable thickness of fine-grained sediments, a significant 

part of the total compaction may be residual compaction 

(delayed compaction that occurs in thick fine-grained 

interbeds and confining layers while heads equilibrate with 

heads in the adjacent aquifers [Terzaghi, 1925]). Depending 

on the thickness and the vertical hydraulic diffusivity 

of a confining layer, pressure equilibration—and thus 

compaction—lags behind pressure, or head, changes in the 

adjacent aquifers. For a more complete description of aquifersystem compaction, see Poland (1984), and for a review and 

selected case studies of land subsidence caused by aquifersystem compaction in the United States, see Galloway and 

others (1999).

Global Positioning System (GPS) 

Surveys

GPS is a U.S. Department of Defense satellite-based 

navigation system designed to provide continuous worldwide 

positioning and navigation capability. For this study, GPS 

surveys were done to determine the three-dimensional position 

of monuments in the geodetic monitoring network. The 

network was established in 1996 by the USGS to determine 

changes in land-surface elevations in the network (Ikehara and 

others, 1997) and to establish baseline values for comparisons 

with results of future surveys.

Land-Subsidence Monitoring Network

The geodetic monitoring network, henceforth referred 

to as the land-subsidence monitoring network, consists of 

geodetic monuments used as GPS stations (fig. 3). Most 

geodetic monuments are flat metal disks that are anchored in 

the ground or to a structure and that can be used in making 

repeated surveying measurements of horizontal and (or) 

vertical positions. During the 1996 study by Ikehara and 

others (1997), historical data for monuments in the southern 

Coachella Valley were compiled and reviewed to determine 

the location and the quality of the vertical-control data. 

Sources of the data include NOAA’s (National Oceanic and 

Atmospheric Administration) National Geodetic Survey (NGS 

[formerly the U.S. Coast and Geodetic Survey]), the California 

Department of Transportation (Caltrans), the U.S. Bureau of 

Reclamation, and the CVWD (Ikehara and others, 1997). The 

geodetic monuments were examined before each of the GPS 

surveys in 1996, 1998, 2000, and 2005 to determine whether 

any had been damaged or destroyed and to evaluate their 

suitability for GPS observations.

The original subsidence monitoring network in the 

southern Coachella Valley was established in 1996 and 

consisted of 17 geodetic monuments. The network was 

modified for the 1998 GPS survey by replacing two 

monuments that had been destroyed (D1299 Tie [D12T] and 

Caltrans 14.3 Reset 1994 [C143]) with two nearby monuments 

(G70 1928 [G70] and Caltrans 13.2 1986 [C132]) (fig. 3). The 

network was again modified for the 2000 GPS survey because 

monument 54JA was horizontally unstable; the replacement 

monument (JA54) was installed about 6 m (20 ft) northwest of 

monument 54JA (fig. 3). In addition, four new monuments—

MAGF, MANI, OSDO, and DEEP—were constructed and 

added in the Palm Desert and Indian Wells areas for the 2000 

GPS survey (fig. 3) because the InSAR maps processed for 

1996–2000 showed subsidence in these areas (Sneed and 

others, 2001, 2002). The monument SWC was destroyed by 

flooding in the Whitewater Stormwater Channel in early 2005, 

and thus could not be included in the 2005 survey (fig. 3). 

The spacing between the monuments meets the generalized 

network design criterion established by Zilkoski and others 

(1997), which requires that the distance between local network 

points not exceed 10 km (6 mi).
Global Positioning System (GPS) Surveys 7

Figure 3. Map showing network of Global Positioning System (GPS) stations and wells used to monitor vertical changes in land surface 

and ground-water levels, respectively, in the southern Coachella Valley, California.

Salton

 Sea

EXPLANATION

0 5 10 MILES

0 5 10 KILOMETERS

Destroyed or abandoned GPS station and identifier

GPS station and identifier

Geodetic monuments

Well and identifier

GPS control station for one or more of the GPS surveys

Destroyed GPS control station and identifier

Continuous Global Positioning System (CGPS) station and identifier

111

86

111

10

10

Coachella

Indian

 Wells

 Palm

Desert

116°30' 20' 10' 115°50'

 45'

33°50'

33°30'

40'

35'

116°00'

COTD

5S/7E-9F1

5S/7E-8Q1

5S/8E-17N1

5S/8E-20C2

6S/7E-23D3

6S/8E-19D1

6S/8E-5P1

6S/8E-5R2

6S/8E-2D1

6S/8E-2F1

6S/8E-12Q1

6S/8E-27C1

6S/8E-32R1 7S/7E-1C1 7S/9E-7H2

7S/9E-17K1

7S/9E-23N1

7S/9E-30M1

7S/8E-20H1 7S/8E-22K1

7S/8E-28G1

7S/8E-34G1

8S/8E-11A4

8S/8E-24A1

8S/8E-24L1

8S/8E-24L1

7S/10E-27A1

5S/6E-17E1 San Andreas Fault Zone

5S/6E-23M1

5S/6E-24M1

DUNE

COCH

R70R

JA54 54JA 5211

CAHU

S753

C132

PAIN

K572

JOHN

C101

C101

C427

C427

P572 SWC

K70

54JA

G70

C143

D12T

D12T

COTD

MAGF

DEEP

OSDO

MANI
8 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005

Determination of Ellipsoid Heights 

GPS measurements were made at the geodetic 

monuments to determine their horizontal positions and 

ellipsoid heights. Ellipsoid height is the vertical coordinate 

relative to a geodetically defined reference ellipse; the 

ellipsoid that closely approximates the Earth’s shape in the 

study area is the North American Datum of 1983 (NAD83). 

To determine changes in ellipsoid heights, the heights from 

successive GPS surveys are compared; then, the differences in 

the heights are used to determine the location and magnitude 

of any vertical land-surface changes. The GPS surveying 

in 1996, 1998, 2000, and 2005 was done in accordance 

with “Guidelines for Establishing GPS-Derived Ellipsoid 

Height” by Zilkoski and others (1997) with one minor 

variation common to all 4 GPS surveys: single baseline, 

rather than multi-baseline, processing software was used 

for postprocessing. There are no known conclusive tests 

that objectively evaluate the effect of using single-baseline, 

rather than multi-baseline, processing software (Craymer and 

Beck, 1992). Other variations to the guidelines are specific to 

particular surveys and are described in the following sections. 

All of the GPS survey data were recomputed during this 

current study to eliminate the effects of variable processing 

methodologies used by assorted software and to standardize 

processing procedures for an improved comparison of threedimensional positions derived from data collected during each 

GPS survey. Software used for the baseline and least-squares 

adjustment computations was Trimble Geomatics Office 

version 1.63.

1996 GPS Survey

GPS measurements for the 1996 survey were made using 

six dual-frequency, half-wavelength P-code GPS receivers 

(Ashtech LD-XII and Ashtech MD-XII) and choke-ring 

antennas (Dorne-Margolin) at the 17 geodetic monuments 

between June 3 and 14, 1996, to determine horizontal 

positions and ellipsoid heights (Ikehara and others, 1997). For 

this survey, the duration of the GPS measurements was nearly 

tripled compared with the duration specified by Zilkoski 

and others (1997) to compensate for using half-wavelength 

GPS receivers rather than the full-wavelength GPS receivers 

(Ikehara and others, 1997). GPS measurements were made 

at the 17 geodetic monuments on at least 2 different days, 

and data were recorded during 2.5- to 3-hour observation 

periods (Ikehara and others, 1997). Six of the 17 geodetic 

monuments—C101, CAHU, COCH, PAIN, D12T, and 

DUNE (fig. 3)—also were network control stations; GPS 

measurements were made at these six stations on 3 additional 

days, and data were recorded during 6-hour observation 

periods. 

Determining the ellipsoid heights of the 17 geodetic 

monuments in the network involved two phases of leastsquares adjustments. During the first phase of least-squares 

adjustments, the horizontal coordinates and ellipsoid heights 

for the six Coachella Valley network control monuments were 

determined by processing the GPS measurements made at 

these monuments with measurements made simultaneously 

at three Continuous Global Positioning System (CGPS) 

stations (DHLG, PIN1, and CRFP) in southern California 

(fig. 1), and by using precise satellite orbital data and 

accurate coordinates of the CGPS stations produced by the 

International GPS Service (IGS) and the Scripps Orbit and 

Permanent Array Center (SOPAC), respectively. The GPS 

observations of the CGPS stations were recorded continually 

(at 30-second intervals), and were archived by SOPAC, a 

member of the Southern California Integrated GPS network 

(SCIGN). The network control monuments were selected on 

the basis of geographic distribution; they are at the perimeters 

of the monitoring network. During the second phase of 

least-squares adjustments, the positions of the six Coachella 

Valley network control monuments were held fixed at the 

positions determined during the first phase, and the horizontal 

coordinates and ellipsoid heights for the other 11 monuments 

were determined. The level of uncertainty for these heights is 

±50 mm (±0.16 ft) at the 95-percent confidence level. 

1998 GPS Survey

GPS measurements for the 1998 survey were made using 

five dual-frequency, full-wavelength P-code GPS receivers 

(Ashtech MD-XII) and choke-ring antennas (Dorne-Margolin) 

at the 17 geodetic monuments between October 5 and 9, 

1998, to determine horizontal positions and ellipsoid heights. 

GPS measurements were made at the 17 geodetic monuments 

on at least 2 different days, and data were recorded during 

45-minute observation periods. Five of the 17 geodetic 

monuments—COCH, CAHU, PAIN, C101, and G70 (fig. 3)—

also were network control stations; GPS measurements were 

made at these five stations on 3 additional days, and data were 

recorded during 4.5-hour observation periods. 

Determining the ellipsoid heights of the 17 geodetic 

monuments in the network involved two phases of leastsquares adjustments. During the first phase of least-squares 

adjustments, horizontal coordinates and ellipsoid heights for 

the five Coachella Valley network control monuments were 

determined by processing the GPS measurements made at 

these monuments using measurements made simultaneously 

at three CGPS stations (DHLG, PIN1, and WIDC) in southern 

California (fig. 1), and by using precise satellite orbital data 

and accurate coordinates of the CGPS stations produced 

by IGS and SOPAC, respectively. The GPS observations of 

the CGPS stations were recorded continually (at 30-second 

intervals) and were archived by SOPAC. During the second 

phase of least-squares adjustments, the positions of the five 

Coachella Valley network control monuments were held 

fixed at the positions determined during the first phase, and 

the horizontal coordinates and ellipsoid heights for the other 

12 monuments were determined. The level of uncertainty for 

these heights is ±20 mm (±0.07 ft) at a 95-percent confidence 

level. 
Global Positioning System (GPS) Surveys 9

2000 GPS Survey

GPS measurements for the 2000 survey were made 

using six dual-frequency, full-wavelength, P-code GPS 

receivers (5 Trimble 4000SSIs and 1 Trimble 4000SSE) and 

compact L1/L2 Trimble antennas (with ground plane) at the 

21 geodetic monuments between August 28 and September 1, 

2000, to determine horizontal positions and ellipsoid heights. 

GPS measurements were made at the monuments on at least 

2 different days, and data were recorded during 35-minute 

observation periods. Six of the 21 geodetic monuments were 

used as network control stations—COCH, DEEP, CAHU, 

PAIN, C101, and G70 (fig. 3). GPS measurements were 

made at these six stations on 3 additional days, and data were 

recorded during 5-hour observation periods. 

Determining the ellipsoid heights of the 21 geodetic 

monuments in the network involved two phases of leastsquares adjustments. During the first phase of least-squares 

adjustments, horizontal coordinates and ellipsoid heights of 

the six Coachella Valley network control monuments were 

determined by processing the GPS measurements made at 

these monuments with measurements made simultaneously 

at the same three CGPS stations (DHLG, PIN1, and WIDC) 

used in processing the 1998 GPS survey data (fig. 1), and by 

using precise satellite orbital data and accurate coordinates of 

the CGPS stations produced by IGS and SOPAC, respectively. 

The GPS observation frequency of the CGPS stations was set 

at 30 seconds, and the observations were archived by SOPAC. 

During the second phase of least-squares adjustments, the 

positions of the six network control monuments were held 

fixed at the positions determined during the first phase, and 

the horizontal coordinates and ellipsoid heights for the other 

15 monuments were determined. The accuracy of these 

ellipsoid heights is ±20 mm (±0.07 ft) at the 95-percent 

confidence level. 

2005 GPS Survey

GPS measurements for the 2005 survey were made using 

six dual-frequency, full-wavelength, P-code GPS receivers 

(Topcon GB1000) and compact antennas (with ground plane) 

(Topcon PG-A1 Geodetic) at the 20 geodetic monuments 

between August 15 and 19, 2005, to determine horizontal 

positions and ellipsoid heights. GPS measurements were 

made at the monuments on at least 2 different days, and data 

were recorded during 1-hour observation periods. Six of 

the 20 geodetic monuments were used as network control 

stations—COCH, DEEP, CAHU, PAIN, C101, and G70 

(fig. 3); GPS measurements were made at these six stations 

on 3 additional days, and data were recorded during 6.5-hour 

observation periods. 

Determining the ellipsoid heights of the 20 geodetic 

monuments in the network involved two phases of leastsquares adjustments. During the first phase of least-squares 

adjustments, horizontal coordinates and ellipsoid heights of 

the six Coachella Valley network control monuments were 

determined by processing the GPS measurements made at 

these monuments using measurements made simultaneously at 

the same three CGPS stations (DHLG, PIN1, and WIDC) used 

in processing both the 1998 and 2000 GPS survey data, and by 

using precise satellite orbital data and accurate coordinates of 

the CGPS stations produced by IGS and SOPAC, respectively. 

The GPS observation frequency of the CGPS stations was set 

at 30 seconds, and the observations were archived by SOPAC. 

During the second phase of least-squares adjustments, the 

positions of the six network control monuments were held 

fixed at the positions determined during the first phase, and 

the horizontal coordinates and ellipsoid heights for the other 

14 monuments were determined. The accuracy of these 

ellipsoid heights is ±20 mm (±0.07 ft) at the 95-percent 

confidence level. 

GPS Results

The horizontal coordinates and the ellipsoid heights of 

the monuments determined from each of the four GPS surveys 

were compared to determine the magnitude of horizontal and 

vertical land-surface changes at the monuments, respectively. 

The horizontal changes at the monuments were consistent with 

the northwest movement of the Pacific Plate (with respect to 

the North American plate) (Shen, Z.-K. and others, 2003). 

The ellipsoid heights are given in table 1, and ellipsoid-height 

changes, adjusted to show ellipsoid height values relative to 

the first GPS measurement for a particular monument (that is, 

the first measurement was set to equal 0), are given in table 1

and shown in figure 4A. 

Comparison of GPS measurements made at the 13 

geodetic monuments surveyed in 1996 and in 2005 in the 

southern Coachella Valley indicate that the elevation of the 

land surface had a net decline of 124 to 9 mm ±54 mm (0.41 

to 0.03 ft ±0.18 ft) during the 9-year period (table 1). Changes 

at 9 of the 13 monuments (DUNE, R70R, 5211, CAHU, 

S753, K572, C101, P572, and C427) exceeded the maximum 

expected uncertainty of ±54 mm (±0.18 ft) at the 95-percent 

confidence level, indicating that subsidence occurred at these 

monuments between June 1996 and August 2005. Changes at 

4 of the 13 monuments (COCH, PAIN, JOHN, and K70) did 

not exceed the maximum expected uncertainty of ±54 mm 

(±0.18 ft) at the 95-percent confidence level, indicating that 

the vertical positions of these monuments in June 1996 and in 

August 2005 were similar. 

Comparisons of GPS measurements made at 20 geodetic 

monuments in 2000 and in 2005 indicate that the elevation 

of the land surface changed –192 to +51 mm ±36 mm (–0.63 

to +0.17 ft ±0.12 ft) during the 5-year period (table 1). 

Changes at 6 of the 20 monuments (MANI, MAGF, OSDO, 

R70R, JA54, and COCH) exceeded the maximum expected 

uncertainty of ±36 mm (±0.12 ft) at the 95-percent confidence 

level—subsidence occurred at five of these monuments 

(MANI, MAGF, OSDO, R70R, and JA54) and uplift occurred 

at COCH between August 2000 and August 2005. Changes at 

14 of the 20 monuments (DEEP, DUNE, 5211, CAHU, S753, 
10 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005 GPS Station Monument name Latitude Longitude Ellipsoid height (m) Ellipsoid-height change from 1st measurement (mm) Ellipsoid-height change from 1st measurement (ft) 1996 (±0.05 m) 1998 (±0.02 m) 2000 (±0.03 m) 2005 (±0.02 m) 1996 1998 2000 2005 1996 1998 2000 2005 DUNE DUNEPORT Azimuth 33°44’46” 116°16’10” –17.354 –17.371 –17.407 –17.436 0 –17 –53 –82 0 –0.056 –0.174 –0.269 COCH COACH 1931 33°44’25” 116°09’30” 33.427 33.436 33.367 33.418 0 9 –60 –9 0 0.030 –0.197 –0.030 MAGF Magnesium Falls Drive 33°44’11” 116°23’27”

—

— 27.742 27.604

—

— 0 –138

—

— 0 –0.453

MANI Manitou Drive 33°43’11” 116°19’03”

—

— 2.962 2.916

—

— 0 –46

—

— 0 –0.151

OSDO Osage Trail/ElDorado Drive 33°43’06” 116°20’19”

—

— 13.484 13.292

—

— 0 –192

—

— 0 –0.630

R70R R70 Reset 1958 33°40’49” 116°10’26” –54.402 –54.433 –54.471 –54.509 0 –31 –69 –107 0 –0.102 –0.226 –0.351

DEEP Deep Canyon 33°40’21” 116°22’34”

—

— 190.409 190.402

—

— 0 –7

—

— 0 –0.023

5211 USBR 52.11 33°40’17” 116°06’43” –32.682 –32.698 –32.740 –32.737 0 –16 –58 –55 0 –0.052 –0.190 –0.180

54JA Ave 54 and Jackson (old) 33°39’24” 116°13’00” –46.348 –46.392

—

— 0 –44

—

— 0 –0.144

—

—

JA54 Jackson and Ave 54 (new) 33°39’24” 116°13’00”

—

— –46.907 –46.991

—

— 0 –84

—

— 0 –0.276

CAHU Lake Cahuilla 33°38’19” 116°16’25” –30.738 –30.778 –30.815 –30.822 0 –40 –77 –84 0 –0.131 –0.253 –0.276

S753 S753 1945 33°38’13” 116°09’49” –68.190 –68.231 –68.276 –68.268 0 –41 –86 –78 0 –0.135 –0.282 –0.256

PAIN Painted Canyon 33°36’43” 116°00’30” 93.365 93.352 93.318 93.343 0 –13 –47 –22 0 –0.043 –0.154 –0.072

C143 Caltrans 14.3 reset 1994 33°35’54” 116°10’52” –72.025

—

—

— 0 —

—

— 0 —

—

—

C132 Caltrans 13.2 1986 33°34’59” 116°10’54”

— –74.001 –74.043 –74.065

— 0 –42 –64

— 0 –0.138 –0.210

K572 K572 1939 33°34’09” 116°05’42” –91.484 –91.515 –91.523 –91.540 0 –31 –39 –56 0 –0.102 –0.128 –0.184

JOHN Johnson 33°33’03” 116°03’18” –94.146 –94.158 –94.170 –94.184 0 –12 –24 –38 0 –0.039 –0.079 –0.125

C101 Caltrans 10.1 1986 33°32’44” 116°09’16” –50.336 –50.396 –50.419 –50.443 0 –60 –83 –107 0 –0.197 –0.272 –0.352

K70 K70 1928 33°32’09” 116°00’21” –91.483 –91.507 –91.536 –91.525 0 –24 –53 –42 0 –0.079 –0.174 –0.138

P572 P572 1939 33°31’32” 116°06’46” –91.233 –91.259 –91.283 –91.311 0 –26 –50 –78 0 –0.085 –0.164 –0.256

SWC Stormwater Channel 33°31’27” 116°04’42” –100.250 –100.280 –100.300

— 0 –30 –50

— 0 –0.098 –0.164

—

D12T D1299 Tie 33°30’42” 115°55’11” –93.664

—

—

— 0 —

—

— 0 —

—

—

G70 G70 1928 33°30’27” 115°54’51”

— –93.078 –93.111 –93.098

— 0 –33 –20

— 0 –0.108 –0.066

C427 Caltrans 4.27 1987 33°28’25” 116°06’27” –73.183 –73.323 –73.272 –73.307 0 –140 –89 –124 0 –0.459 –0.292 –0.407

Table 1. Horizontal positions and ellipsoid heights for 1996, 1998, 2000, and 2005, and ellipsoid-height changes relative to the first measurement of geodetic monuments in the Coachella Valley, California.[Latitude, longitude, and ellipsoid height are referenced to the North American Datum of 1983. Negative values for ellipsoid–height change indicate subsidence. m, meter, mm, millimeter; ft, foot; ––, no data]
Global Positioning System (GPS) Surveys 11 Figure 4. Hydrographs showing (A) water-surface elevations for selected wells (between 1995 and 2005), and ellipsoid-height changes (relative to the first measurement) for geodetic monuments measured at least twice, and (B) water-surface elevations for a subset of the wells in A for 1925-2005. (See figure 3 for well locations.)

CA-3408_fig 04a_Page 1

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-10-20-30-40-50

0

5040302010

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-100-110

-10-20-30-40-50-60-70-80-90

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-10-20-30

0

70605040302010

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-100

-10-20-30-40-50-60-70-80-90

0

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-100-110-120-130-140-150

-50-60-70-80-90

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-1-110-120-130-140-150

00

-50-60-70-80-90

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-100-110-120-130-140-150-160-170

-70-80-90

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-100-110-120-130-140-150-160-170

-70-80-90

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-1.4

-0.2-0.4-0.6-0.8-1.0-1.2

0.40.20.0 -100

-110-120-130-140-150-160-170-180

-80-90

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-100

-10-20-30-40-50-60-70-80-90

0

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

ELLIPSOID HEIGHT (FEET RELATIVE TO THE FIRST MEASUREMENT)

WATER-SURFACE ELEVATION (FEET RELATIVE TO SEA LEVEL)

5S/6E-17E1 (screened in the lower aquifer)

5S/7E-8Q1 (screened in the upper aquifer)

5S/7E-9F1 (screened in the perched and upper aquifers)

DUNE

5S/8E-17N1 (screened in the  upper aquifer)

COCH

5S/6E-23M1 (screened in the upper  and lower aquifers)

OSDO

5S/6E-24M1 (screened in the upper  and lower aquifers)

MANI

6S/8E-5P1 (screened in the perched aquifer)

6S/8E-5R2 (screened in the upper aquifer)

R70R

6S/8E-2D1 (screened in the upper aquifer) 6S/8E-12Q1 (screened in the upper aquifer)

5211

JA54 (new)

6S/7E-23D3 (screened in the upper aquifer)

6S/8E-19D1 (screened in the lower aquifer)

6S/7E-23D3 (screened in the upper aquifer)

6S/8E-19D1 (screened in the lower aquifer)

54JA (old) CAHU

6S/8E-19D1 (screened in the lower aquifer)

6S/8E-27C1 (screened in the upper and lower aquifers)

S753

6S/8E-2F1 (screened in the upper and lower aquifers)

DEEP

WATER-SURFACE ELEVATION (FEET RELATIVE TO SEA LEVEL)

WATER-SURFACE ELEVATION (FEET RELATIVE TO SEA LEVEL)

ELLIPSOID HEIGHT (FEET RELATIVE TO THE FIRST MEASUREMENT)

ELLIPSOID HEIGHT (FEET RELATIVE TO THE FIRST MEASUREMENT)

5S/8E-20C2 (screened in the upper aquifer)

MAGF

A
12 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005

CA-3408_fig 04a_Page 2

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-120-130-140-150-160-170-180-190-200-210-220

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-150-160-170-180-190-200-210-220-230-240-250

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-115-125-135-145-155-165-175-185-195-205-215

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-250-260-270-280-290-300-310-320-330-340-350

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-275

-175-185-195-205-215-225-235-245-255-265

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-200-210-220-230-240-250-260-270-280-290-300

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0 -10

-20-30-40-50-60-70-80-90

0

10

-1.4

-0.2-0.4-0.6-0.8-1.0-1.2

0.40.20.0

-100-110-120-130-140-150-160-170

-70-80-90

-0.2-0.4-0.6-0.8-1.0-1.2-1.4

0.40.20.0

-175-185-195-205-215-225-235-245-255-265-275

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

6S/8E-32R1 (screened in perched, upper, and lower aquifers)

7S/7E-1C1 (screened in the upper aquifer)

C132

PAIN

7S/9E-7H2 (screened in the upper aquifer)

K572

7S/9E-17K1 (screened in the upper  and lower aquifers)

JOHN

7S/9E-30M1 (screened in the perched  and upper aquifers)

SWC

7S/8E-22K1 (screened in the upper and lower aquifers)

7S/8E-28G1 (screened in the upper aquifer)

7S/8E-20H1 (screened in the upper aquifer)

C101

P572

7S/8E-34G1 (screened in the perched aquifer)

7S/9E-23N1 (screened in the upper aquifer)

K70

8S/8E-24A1 (screened in the lower aquifer) 8S/8E-24L1 (screened 

in the upper aquifer)

8S/8E-11A4 (screened in the upper aquifer)

C427

7S/10E-27A1 (unknown screened interval)

G70

ELLIPSOID HEIGHT (FEET RELATIVE TO THE FIRST MEASUREMENT)

WATER-SURFACE ELEVATION (FEET RELATIVE TO SEA LEVEL)

WATER-SURFACE ELEVATION (FEET RELATIVE TO SEA LEVEL)

WATER-SURFACE ELEVATION (FEET RELATIVE TO SEA LEVEL)

ELLIPSOID HEIGHT (FEET RELATIVE TO THE FIRST MEASUREMENT)

ELLIPSOID HEIGHT (FEET RELATIVE TO THE FIRST MEASUREMENT)

A

Figure 4. Continued.
Global Positioning System (GPS) Surveys 13

Figure 4. Continued. WATER-SURFACE ELEVATION (FEET RELATIVE TO SEA LEVEL)

YEAR

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

20

40

60

80

-320

-300

-280

-260

-240

-220

-200

-180

-160

-140

-120

-100

-80

-60

1925 1935 1945 1955 1965 1975 1985 1995 2005

 6S/8E-2D1 

(screened in the upper aquifer)

 6S/8E-27C1 

(screened in the upper and lower aquifers)

6S/8E-19D1 

(screened in the lower aquifer)

 5S/8E-17N1 

(screened in the upper aquifer)

 5S/6E-23M1 

(screened in the upper and lower aquifers)

 5S/7E-9F1 

(screened in the perched and upper aquifers)

 7S/8E-34G1 

(screened in the perched aquifer)

 7S/9E-7H2 

(screened in the upper aquifer)

8S/8E-24L1 

(screened in the 

upper aquifer)

 7S/9E-23N1 

(screened in the upper aquifer)

B

PAIN, C132, K572, JOHN, C101, K70, P572, G70, and C427) 

did not exceed the maximum expected uncertainty of ±36 mm 

(±0.12 ft) at the 95-percent confidence level, indicating that 

the vertical positions of these monuments in August 2000 and 

in August 2005 were similar.

GPS measurements were made at 16 geodetic monuments 

(DUNE, COCH, R70R, 5211, CAHU, S753, C132, PAIN, 

C101, K572, JOHN, P572, SWC, K70, C427, and G70) during 

at least 3 of the 4 surveys, thus permitting calculations and 

comparisons of subsidence rates. A seventeenth monument, 

54JA, was surveyed in 1996 and 1998 and was then replaced 

with monument JA54 (about 6 m [20 ft] northwest from 

54JA) for the 2000 and 2005 surveys; although the monument 

location was changed slightly, rates of subsidence were 

compared. Because GPS data indicated that the heights of 

PAIN, JOHN, K70, SWC, and G70 were fairly stable (fig. 

4A), the subsidence rates of the other 12 monuments are 

discussed. Eleven of the twelve monuments (DUNE, COCH, 

R70R, 5211, 54JA/JA54, CAHU, S753, C132, C101, K572, 

and P572) show decreased subsidence rates between 2000 and 

2005 compared with the subsidence rates between 1998 and 

2000, a period when the largest rates were computed at these 

11 monuments (fig. 4A). The most marked subsidence-rate 

decreases between these two periods occurred at monuments 

COCH, 5211, CAHU, and S753, and the least marked 

subsidence-rate changes occurred at 54JA/JA54. Subsidence 

rates between 2000 and 2005 at DUNE, R70R, and P572 

decreased by factors ranging from 2 to 3, and C132 decreased 

by a factor of about 5, compared to rates between 1998 and 

2000. Calculated subsidence rates at monuments C101 and 

K572 continually decreased during 1996–2005. GPS results 

for the twelfth monument—C427— indicated subsidence 

between 1996 and 1998 and between 2000 and 2005, and 

uplift between 1998 and 2000, resulting in insignificant 

vertical position differences between 1998 and 2005. A power 

pole adjacent to C427 may have degraded the quality of the 

GPS observations; it is suspected that GPS observations at 

C427 had higher-than-expected errors. 
14 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005

Ground-Water Levels

In the northwestern part of the geodetic network (near 

MANI, MAGF, OSDO, R70R, and JA54), where significant 

land subsidence was measured by 2005, and near DUNE, 

where small amounts of subsidence were measured by 

2005, water levels generally showed seasonal fluctuations 

superimposed on longer-term water-level declines during 

1995–2005 (fig. 4A). In the northeastern part of the network, 

at COCH, where significant uplift was measured by 2005, 

water levels in nearby wells also showed seasonal fluctuations 

superimposed on longer-term water-level declines during 

1995–2005 (fig. 4A). However, wells 5S/8E-17N1 and 5S/8E20C2, in which water levels were measured near COCH, are 

on the west side of the San Andreas Fault (fig. 4A) and the 

geodetic monument COCH is on the east side of the fault 

(fig. 3); thus, hydrologic conditions in the two wells probably 

do not represent hydrologic conditions at COCH. 

In the southwestern part of the network near monuments 

C101, C132, P572, S753, and C427, where small amounts 

of subsidence were measured by 2005, water levels showed 

seasonal fluctuations superimposed on longer-term water-level 

declines during 1995–2005 (fig. 4A).

In the southeastern part of the network near K572, JOHN, 

K70, and G70, and in the northeastern part of the network 

near 5211, where small or insignificant changes in elevation 

occurred, water levels generally showed seasonal variability 

superimposed on fairly stable or rising water levels during 

1995 and 2005 (fig. 4A). 

The relationship between ground-water-level changes and 

concurrent vertical changes at the geodetic monuments is not 

clearly defined. Complications that contribute to the difficulty 

in deciphering the relationship include the low frequency of 

both GPS and water-level measurements, and the complex, 

often significantly delayed mechanical responses of the aquifer 

system to ground-water-level changes. However, the locations 

of the monuments that subsided between 1996 and 2005 are 

coincident with areas where water levels generally declined 

during this period and during most of the last century (fig. 4). 

Similarly, the locations of the monuments that were fairly 

stable between 1996 and 2005 are coincident with areas where 

water levels generally were stable or recovered during this 

period. The coincident areas of subsidence and declining water 

levels, and of elevation stability and stable or recovering water 

levels, indicate that aquifer-system compaction may be causing 

subsidence. In the areas of subsidence, if water levels have 

declined sufficiently such that the effective stresses exceeded 

the preconsolidation stresses as is suggested by the historically 

low water levels shown in figure 4B, the subsidence may be 

permanent. Although this longer term relationship seems more 

straightforward, tectonically-induced subsidence also occurs 

on longer time scales. However, the CGPS stations used as 

constraints for each of the GPS datasets were fairly stable 

between 1996 and 2005, indicating that tectonic-induced 

vertical crustal motion was not included in the subsidence 

measurements at the geodetic monuments in the network. 

InSAR Methodology

Using Interferometric Synthetic Aperture Radar (InSAR) 

is an effective way to measure vertical changes of land 

surface. InSAR is a satellite-based remote sensing technique 

that can detect centimeter-level ground-surface deformation 

over a 100 km2 area with a spatial resolution of 90 m or less. 

Synthetic Aperture Radar (SAR) imagery is produced by 

reflecting radar signals off a target area and measuring the 

two-way travel time between the target area and the satellite. 

InSAR uses two SAR scenes of the same area taken at 

different times and “interferes” (differences) them, resulting 

in maps called interferograms that show line-of-sight groundsurface displacement (range change) between the two time 

periods. The generation of an interferogram produces two 

components, amplitude and phase. The amplitude is the 

measure of the radar signal intensity returned to the satellite 

and shows roads, mountains, and other reflective features 

(similar to the image shown in fig. 5); the phase component 

is proportional to range change and shows the coherent 

displacements imaged by the radar (figs. 6A, 7A, 8A). If the 

ground has moved away from (subsidence) or towards (uplift) 

the satellite between the times of the two acquisitions (the 

“timeline”), a slightly different portion of the wavelength is 

reflected back to the satellite resulting in a measurable phase 

shift that is proportional to range change. The map of phase 

shifts, or interferogram, is depicted with a repeating color 

scale that shows relative range change between the first and 

the second acquisitions. In this report, one complete color 

cycle (fringe) represents 28.3 mm (0.09 ft) of range change. 

Assuming all the motion is vertical, the indicated range 

change is about 90- to 95-percent of true vertical ground 

motion, depending on the satellite look angle and the location 

of the target area. The direction of change—subsidence or 

uplift—is indicated by the color progression of the fringe(s) 

from the outer edge of a deforming feature toward its center. 

For interferograms in this report, the color-fringe progression 

of yellow-green-blue-pink indicates subsidence; the opposite 

progression indicates uplift.

InSAR signal quality depends partly on satellite position, 

atmospheric effects, ground cover, land-use practices, and 

timeline of the interferogram. Strict orbital control is required 

to precisely control the look angle and position of the satellite. 

Successful application of the InSAR technique is contingent 

on looking at the same point on the ground from the same 

position in space so that the horizontal distance between 

each satellite pass, or perpendicular baseline, is minimized. 

Perpendicular baselines generally greater than about 

200 m (656 ft) usually produce excessive topographic effects 

(parallax) that can mask the deformation signal. Phase shifts 

can be caused by varying atmospheric mass that is associated 

with different elevations. A digital elevation model (DEM) 

is used in the interferogram generation process to reduce the 

atmospheric effects caused by elevation differences (and also 

to georeference the image). Phase shifts also can be caused by 
InSAR Methodology 15

Lake Cahuilla

Coachella Branch of the All-American Canal

111

!(

111

!(

74

!(

10

§ ̈¦

Palm Desert (Area 1)

Indian Wells (Area 2)

La Quinta (Area 3)

48th St

60th St

Monroe St

Country Club Dr

Cook St

Bob Hope Dr

Frank Sinatra Dr

Monterey Ave

Clancy Ln

Fred Waring Dr

Mountain Cove Dr

Monterey Ave

Rancho Palmeras Dr

Jefferson St Club Dr

Indian Wells Ln

Whitewater River

TMAP

COTD

5S/6E-7M1

5S/6E-17M2

6S/7E-6B1

6S/7E-21D1

6S/7E-16A2

6S/7E-16R2

5S/6E-23K2

5S/7E-31Q2

5S/6E-8N3

5S/6E-25A1

5S/6E-23N1

5S/6E-16M1

5S/6E-22B1

5S/6E-5Q1

5S/6E-24F1

Indio

Coachella

DEEP

OSDO MANI

MAGF

C143

C132

S753

54JA/JA54

CAHU

R70R

COCH DUNE

Santa Rosa Mountains

Indio Hills

San Jacinto Mountains

33°45'33°37'

2 0 Miles

2 0 Kilometers

Consolidated Rock or Partly Consolidated Deposits

GPS station and identifier OSDOWell and identifier 5S/7E-31Q2

CGPS station and identifier COTD

116°7' 116°15' 116°22'

Figure 5. Image showing land-surface features, consolidated rock, Global Positioning System (GPS) stations, two Continuous Global Positioning System (CGPS) stations, three areas of subsidence, and selected roads and production wells, Coachella Valley, California. (Hydrographs for production wells are shown in figure 9.)
16 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005

Figure 6. Areas of subsidence, linearities at subsidence margins, consolidated rock, GPS stations, and two CGPS stations in the Coachella Valley, California, for November 30, 2003, through May 23, 2004, (A) as shown on the interferogram, and (B) as shown by subsidence contours interpreted from the interferogram in A. 

Coachella Branch of the All-American Canal

Santa Rosa Mountains

San Jacinto Mountains

Indio Hills

Nov 30, 2003 - May 23, 2004

111

!(

111

!(

74

!(

10

§ ̈¦

Palm Desert (Area 1)

Indian Wells (Area 2)

La Quinta (Area 3)

TMAP

COTD

Indio

Coachella

DEEP

OSDO MANI MAGF

C143

C132

S753

54JA/JA54

CAHU

R70R

COCH DUNE

Trace of linearities at subsidence margins

0 -28 mm +28 mm 

relative 

subsidence uplift

2 0 Miles

2 0 Kilometers

Consolidated Rock or Partly Consolidated Deposits

GPS station and identifier OSDO

CGPS station and identifier COTD

33°45'33°37'

116°7' 116°15' 116°22'

A
InSAR Methodology 17

Nov 30, 2003 - May 23, 2004

TMAP

COTD

Indio

Coachella

Santa Rosa Mountains

San Jacinto Mountains

Indio Hills

33°45'33°37'

111 !(

111 !(

74 !(

10 § ̈¦

2 0 Miles

2 0 Kilometers

Subsidence Contour-Interval 10 mm

Consolidated Rock or Partly Consolidated Deposits

GPS station and identifier OSDO

CGPS station and identifier COTD

DEEP

OSDO MANI MAGF

C143

C132

S753

54JA/JA54

CAHU

R70R

COCH DUNE

116°7' 116°15' 116°22'

30 10

30

30

20

20

10

10

10

20 20

20

30

20

10 20 20 20 20

20

Indian Wells (Area 2)

La Quinta (Area 3)

Palm Desert (Area 1) Coachella Branch of the All-American Canal

B

Figure 6. Continued.
18 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005 33°45' 33°37'

Coachella Branch of the All-American Canal

Santa Rosa Mountains

San Jacinto Mountains

Aug 1, 2004 - Sept 5, 2004

Indio Hills

111

!(

111

!(

74

!(

10

§ ̈¦

Palm Desert (Area 1)

Indian Wells (Area 2)

La Quinta (Area 3)

TMAP

COTD

Indio

Coachella

DEEP

OSDO MANI MAGF

C143

C132

S753

54JA/JA54

CAHU

R70R

COCH DUNE

0 -28 mm +28 mm 

relative 

subsidence uplift

2 0 Miles

2 0 Kilometers

Consolidated Rock or Partly Consolidated Deposits

GPS station and identifier OSDO

CGPS station and identifier COTD

116°7' 116°15' 116°22'

A

Figure 7. Areas of subsidence, consolidated rock, GPS stations, and two CGPS stations in the Coachella Valley, California, for August 1, 2004, through September 5, 2004, (A) as shown on the interferogram, and (B) as shown by subsidence contours interpreted from the interferogram in A.
InSAR Methodology 19 Figure 7. Continued.

33°45'33°37'

Coachella Branch of the All-American Canal

Santa Rosa Mountains

San Jacinto Mountains

Aug 1, 2004 - Sept 5, 2004

Indio Hills

111 !(

111 !(

74 !(

10 § ̈¦

Palm Desert (Area 1)

Indian Wells (Area 2)

La Quinta (Area 3)

TMAP

COTD

Indio

Coachella

DEEP

OSDO MANI MAGF

C143

C132

S753

54JA/JA54

CAHU

R70R

COCH DUNE

$

2 Miles

2 Kilometers

Consolidated Rock or Partly Consolidated Deposits

GPS station and identifier

OSDO

CGPS station and identifier COTD

Subsidence Contour -Interval 10 mm

2 0 Miles

2 0 Kilometers

Subsidence Contour-Interval 10 mm

Consolidated Rock or Partly Consolidated Deposits

GPS station and identifier OSDO

CGPS station and identifier COTD

10

10

B

116°7' 116°15' 116°22'
20 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005

Figure 8. Areas of subsidence, consolidated rock, GPS stations, and two CGPS stations in the Coachella Valley, California, for October 26, 2003, through

June 12, 2005, (A) as shown on the interferogram, and (B) as shown by subsidence contours interpreted from the interferogram in A.

33°45'33°37'

116°7' 116°15' 116°22'

Coachella Branch of the All-American Canal

Santa Rosa Mountains

San Jacinto Mountains

Indio Hills

Oct 26, 2003 - June 12, 2005

111

!(

111

!(

74

!(

10

§ ̈¦

Palm Desert (Area 1)

Indian Wells (Area 2)

La Quinta (Area 3)

TMAP

COTD

Indio

Coachella

DEEP

OSDO MANI MAGF

C143

C132

S753

54JA/JA54

CAHU

R70R

COCH DUNE

$

2 Miles

2 Kilometers

Consolidated Rock or Partly Consolidated Deposits

GPS station and identifier

OSDO

CGPS station and identifier COTD

0 -28 mm +28 mm 

relative 

subsidence uplift

2 0 Miles

2 0 Kilometers

Consolidated Rock or Partly Consolidated Deposits

GPS station and identifier OSDO

CGPS station and identifier COTD

A
InSAR Methodology 21 Figure 8. Continued.

33°45'33°37'

116°07' 116°15' 116°22'

Coachella Branch of the All-American Canal

Santa Rosa Mountains

San Jacinto Mountains

Indio Hills

Oct 26, 2003 - June 12, 2005

111

!(

111

!(

74

!(

10

§ ̈¦

Palm Desert (Area 1)

Indian Wells (Area 2)

La Quinta (Area 3)

TMAP

COTD

Indio

Coachella

DEEP

OSDO MANI MAGF

C143

C132

S753

54JA/JA54

CAHU

R70R

COCH DUNE

2 0 Miles

2 0 Kilometers

Subsidence Contour-Interval 10 mm

Consolidated Rock or Partly Consolidated Deposits

GPS station and identifier OSDO

CGPS station and identifier COTD

10

10

10

20

10

60

30

80

70

80

50

40

20

30

40

50

60

80

90

70

30

30

40

40 50 60

60 50 60 50

70

20

20

30

40 50

60 70

80

90

40

90

90

100

110

100

B
laterally variable atmospheric conditions such as clouds or fog, 

as the non-uniform distribution of water vapor differentially 

slows the radar signal over an image. Atmospheric artifacts 

can be identified by using several independent interferograms, 

which are defined as interferograms that do not share a 

common SAR image. When apparent ground motion is 

detected in only one interferogram, or a set of interferograms 

sharing a common SAR image, then the apparent motion 

likely is due to atmospheric phase delay or other error source 

and can be discounted. 

The type and density of ground cover also can 

significantly affect interferogram quality. Densely forested 

areas are prone to reflect poor signals because the C-band 

wavelength (56.6 mm or 0.18 ft) cannot effectively penetrate 

thick vegetation and is either absorbed or reflected back to 

the satellite from varying depths within the canopy resulting 

in incoherent signal (shown as randomized colors on an 

interferogram). Sparsely vegetated areas and urban centers, 

however, generally reflect coherent signals because bare 

ground, roads, and buildings have high reflectivities and 

are relatively uniform during at least some range of InSAR 

timelines. Certain land-use practices, such as farming, which 

is prevalent in the Coachella Valley, also cause incoherent 

signal return. The tilling and plowing of farm fields causes 

large and nonuniform ground-surface change that cannot be 

resolved with InSAR. In both urban and non-urban areas, 

signal quality also is adversely affected by longer timelines, as 

there is more opportunity for nonuniform change and temporal 

decorrelation of the radar signal. Because Coachella Valley is 

fairly flat and contains several urban centers, the area lends 

itself to confident InSAR interpretations because most of the 

error sources are minimized. The agricultural fields in the 

area, however, cause significant InSAR signal incoherence 

that cannot be reliably interpreted using the coherent InSAR 

techniques described here.

Data from the European Space Agency’s (ESA) 

ENVISAT satellite were obtained for analysis. The multimission ENVISAT platform was launched in 2002 and is 

currently (2007) the only ESA-owned fully functional SAR 

satellite. (The previous studies [Sneed and others 2001, 

2002] used ESA’s ERS-1 and -2 satellites; ERS-1 was turned 

off in 1999 and ERS-2 is no longer routinely suitable for 

interferometry). The satellite is side-looking and orbits the 

Earth at an altitude of approximately 800 km (500 mi), and has 

a 35-day repeat orbit. Twenty SAR images, acquired between 

February 26, 2003 and September 25, 2005, were used to 

produce 22 interferograms having timelines that range from 

35 to 595 days. The three interferograms shown in this report 

were selected on the basis of overall interferogram quality 

and timeline length. Figures 6, 7, and 8 show interferograms 

representing timelines ranging from 35 days to 595 days; 

the variable timelines demonstrate temporal decorrelation 

of an interferogram (coherency) and on subsidence feature 

characteristics, such as geographic extent. 

InSAR Results

The interferograms of the Coachella Valley show 

significant land-surface-elevation changes in at least four 

areas. Land subsidence occurred in three of the areas—Palm 

Desert (Area 1), Indian Wells (Area 2), and La Quinta (Area 

3) (figs. 6, 7, 8; table 2)—and both subsidence and uplift 

apparently occurred in one of the areas—Indio-Coachella—

between February 26, 2003, and September 25, 2005. The 

interferograms show that other local areas in the Coachella 

Valley also may have deformed (figs. 6, 7, 8), but the extent of 

these areas and the amount of deformation generally are small 

compared with the three areas of land subsidence discussed in 

this section.

Land Subsidence in the Palm Desert Area 

(Area 1)

A subsidence signal was detected in Palm Desert (Area 1 

in figs. 5, 6, 7, 8); this signal was previously detected by 

Sneed and others (2001, 2002) using InSAR methods. All 22 

interferograms analyzed for this study show subsidence in 

this area (for example, figs 6, 7, 8; table 2). The part of the 

signal that has the largest magnitude is nearly circular (slightly 

elongated north to south); in longer-term interferograms, it is 

as large as about 2 km (1.2 mi) in diameter and has an area 

of about 4 km2 (1.5 mi2) (fig. 8). This part of the signal is 

approximately bounded by Clancy Lane on the north, Fred 

Waring Drive on the south, Highway 111 and Bob Hope on 

the west, and Monterey Avenue on the east (fig. 5). The part of 

the signal that is smaller in magnitude extends to the north and 

east, has a pronounced northwest–southeast elongation, and 

has a much larger extent. The extent of this part of the signal is 

larger in interferograms representing longer timelines (fig. 8) 

than interferograms representing shorter timelines (fig. 7), 

but generally extends to the northwest where Frank Sinatra 

Drive intersects the Whitewater River channel, to the north 

beyond Country Club Drive, and to the east as far as Cook 

Street (fig. 5). The San Jacinto and Santa Rosa Mountains, 

which are outcropping consolidated rock, may act as barriers 

to subsidence farther to the south and southwest; and the Indio 

Hills, which are outcropping partly consolidated deposits, 

may act as barriers to subsidence farther to the northeast 

(figs. 2, 5). A lack of barriers to the northwest and southeast 

may explain the pronounced elongation of the subsidence 

signal in these directions. Several deformation timeseries 

can be constructed from InSAR data. The longest timeseries 

timeline (840 days)—May 7, 2003 to September 25, 2005—

was constructed using 3 interferograms (5/7/2003-9/8/2004; 

9/5/2004-4/3/2005; 5/8/2005-9/25/2005) and indicates that 

about 180 mm (0.59 ft) of subsidence occurred in the Palm 

Desert area during this time—a rate of more than 6 mm/month 

(0.02 ft/month) (Area 1 in figs. 5, 6, 7, 8, 9A). Sneed (2001; 

22 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005
Acquisition dates Palm Desert (Area 1) Indian Wells (Area 2) La Quinta (Area 3) West bowl East bowl North Central South

start date-end date

timeline 

(days)

magnitude 

(mm)

magnitude 

(ft)

magnitude 

(mm)

magnitude 

(ft)

magnitude 

(mm)

magnitude 

(ft)

magnitude 

(mm)

magnitude 

(ft)

magnitude 

(mm)

magnitude 

(ft)

magnitude 

(mm)

magnitude 

(ft)

2/26/2003–6/11/2003 105 –20 –0.07 –5 –0.02 0 0 i i i i i i

5/7/2003–9/8/2004 490 –90 –0.30 –60 –0.20 –50 –0.16 –90 –0.30 –120 –0.39 –60 –0.20

9/24/2003–8/4/2004 315 –80 –0.26 –30 –0.10 –30 –0.10 –50 –0.16 –60 –0.20 –60 –0.20

10/26/2003–6/27/2004 245 –45 –0.15 –25 –0.08 –25 –0.08 –30 –0.10 –45 –0.15 i i

10/26/2003–11/14/2004 385 –70 –0.23 –40 –0.13 –35 –0.11 –40 –0.13 –80 –0.26 –50 –0.16

10/26/2003–2/27/2005 490 –60 –0.20 –40 –0.13 –40 –0.13 –60 –0.20 –70 –0.23 –60 –0.20

10/26/2003–6/12/2005 595 –90 –0.30 –70 –0.23 –60 –0.20 –90 –0.30 –110 –0.36 –90 –0.30

11/30/2003–5/23/2004 175 –35 –0.11 –20 –0.07 –20 –0.07 –30 –0.10 –30 –0.10 –30 –0.10

11/30/2003–7/17/2005 595 –90 –0.30 –40 –0.13 –40 –0.13 –70 –0.23 100 0.33 –60 –0.20

5/23/2004–1/23/2005 245 –60 –0.20 –30 –0.10 –25 –0.08 –70 –0.23 –50 –0.16 –60 –0.20

5/23/2004–7/17/2005 420 –90 –0.30 –50 –0.16 –40 –0.13 –70 –0.23 –90 –0.30 –60 –0.20

6/27/2004–11/14/2004 140 –40 –0.13 –20 –0.07 –15 –0.05 –40 –0.13 –40 –0.13 –50 –0.16

8/1/2004–9/5/2004 35 –15 –0.05 0 0 0 0 –15 –0.05 –10 –0.03 –10 –0.03

8/1/2004–4/3/2005 245 –50 –0.16 –30 –0.10 –20 –0.07 –40 –0.13 –40 –0.13 –50 –0.16

9/5/2004–4/3/2005 210 –50 –0.16 –25 –0.08 –15 –0.05 –40 –0.13 –30 –0.10 –30 –0.10

11/14/2004–12/19/2004 35 –10 –0.03 0 0 0 0 –5 –0.02 0 0 5 0.02

11/14/2004–2/27/2005 105 –25 –0.08 –15 –0.05 –10 –0.03 –20 –0.07 0 0 10 0.03

12/19/2004–2/27/2005 70 –15 –0.05 –10 –0.03 –5 –0.02 –15 –0.05 –10 –0.03 –10 –0.03

1/23/2005–7/17/2005 175 –30 –0.10 –20 –0.07 –10 –0.03 –30 –0.10 –40 –0.13 –30 –0.10

2/27/2005–6/12/2005 105 –20 –0.07 –15 –0.05 –5 –0.02 –10 –0.03 –20 –0.07 –25 –0.08

5/8/2005–9/25/2005 140 –40 –0.13 –20 –0.07 –10 –0.03 –30 –0.10 –25 –0.08 –30 –0.10

7/17/2005–9/25/2005 70 –15 –0.05 –15 –0.05 –5 –0.02 –20 –0.07 –15 –0.05 –15 –0.05

Table 2. Vertical change measured using interferometric synthetic aperture radar (InSAR) for 3 areas in the Coachella Valley, California, 2003–2005.[Negative values for magnitude indicate subsidence. Bold type indicates conservative value owing to increased incoherency associated with longer timelines. Shading: Green shade indicates that the interferogram is shown in figure 6A; brown shade indicates that the interferogram is shown in figure 7A; and pink shade indicates that the interferogram is shown in figure 8A. ft, foot; i, incoherent; mm, 

millimeter]

InSAR Methodology 23
2002) reported that about 150 mm (0.49 ft) of subsidence 

occurred in this area during 1,541 days between 1996 and 

2000, which is equivalent to a rate of about 3 mm/month 

(0.1 ft/month). These data indicate that subsidence rates have 

doubled since 2000.

Land Subsidence in the Indian Wells Area 

(Area 2)

In the Indian Wells area, two distinct subsidence signals 

were detected, termed the western bowl and the eastern bowl 

(Area 2 in figs. 5, 6, 7, 8). Sneed and others (2002) discussed 

a possible additional subsidence signal as suspect about 1 km 

(0.6 mi) southeast of the eastern subsidence bowl because of 

the proximity of this area to steep topographic terrain. The 

shorter timelines and multiple interferograms analyzed during 

this current study show that it is an extension of the eastern 

subsidence bowl (for example, fig. 6). Twenty of the 22 

interferograms analyzed for this study show the western bowl 

and 19 show the eastern bowl (for example, figs 6, 8; table 2). 

The two interferograms with the shortest timelines (35 days) 

do not show either the western or eastern subsidence bowl 

(for example, fig. 7) and one interferogram of relatively low 

quality (not shown) with a 105-day timeline does not show 

the eastern bowl (table 2). The western subsidence bowl is 

approximately bounded by Fred Waring Drive on the north, 

the Santa Rosa Mountains on the south, Rancho Palmeras 

Drive on the west, and Indian Wells Lane on the east (fig. 5). 

The eastern subsidence bowl is approximately bounded by 

Highway 111 on the north, the Santa Rosa Mountains on the 

south, Club Drive on the west, and Mountain Cove Drive 

on the east (fig. 5). Distinct northwest-southeast linearities 

shown near the northern margins of the pair of subsiding 

bowls suggest the presence of barriers to ground-water flow 

or abrupt changes in lithology that control the northern 

extent of subsidence (fig. 6). The western bowl, which is 

elongated northwest–southeast, is as large as about 2.3 km 

(1.4 mi) long and about 1.8 km (1.1 mi) wide (northeast–

southwest) and has an area of about 4.1 km2 (1.6 mi2) in 

longer-term interferograms. The eastern bowl, which also is 

elongated northwest–southeast, is as large as about 2.3 km 

(1.4 mi) long and ranges from about 0.3 to 0.8 km (0.2 

to 0.5 mi) wide (northeast–southwest) and has an area of 

1.2 km2 (0.5 mi2) (Area 2 in figures 6 and 8). The maximum 

subsidence for the western bowl was about 105 mm (0.34 ft) 

and for the eastern bowl was about 75 mm (0.25 ft) from 

May 7, 2003 to September 25, 2005 (fig. 9A); the equivalent 

rates are nearly 4 mm/month (0.013 ft/month) and nearly 

3 mm/month (0.01 ft/month) for the western and eastern 

bowls, respectively. Sneed (2001; 2002) reported that about 

80 mm (0.26 ft) of subsidence occurred in each bowl between 

1996 and 2000; the equivalent rate is about 1.6 mm/month 

(0.005 ft/month). These data indicate that subsidence rates 

have doubled since 2000. 

Land Subsidence in the La Quinta Area 

(Area 3)

A third area of subsidence was detected in the La 

Quinta area (Area 3 in figs. 5, 6, 7, 8). All 22 interferograms 

analyzed for this study show subsidence in this area (for 

example, figs. 6, 7, 8; table 2). Sneed and others (2002) 

analyzed 2 interferograms with timelines of 315 and 

350 days and suggested Area 3 consisted of two separate 

areas of subsidence—termed the La Quinta and the Lake 

Cahuilla areas of subsidence—because the interferograms 

were not coherent throughout the area. Similarly for the 

interferograms analyzed for this current study, the longerterm interferograms were incoherent near the central part of 

the subsiding area (for example, figs. 6 and 8); however, the 

shorter-term interferograms show that this subsidence area 

likely is continuous, and is termed the La Quinta subsidence 

area for this report (for example, fig. 7A). The La Quinta 

subsidence area is about 10 km (6 mi) in length (northwestsoutheast) and is as much as 3 km (1.9 mi) in width. The 

area is approximately bounded by 48th Street (if extended 

westward) on the north, 60th Street (if extended westward) on 

the south, the Santa Rosa Mountains on the west, and streets 

varying from Jefferson Street to Monroe Street on the east 

(because the subsidence area trends northwest-southeast) 

(fig. 5). Different portions of this elongate subsidence bowl 

are subsiding at different rates; for May 7, 2003 to September 

25, 2005, subsidence was 160 mm (0.52 ft) in the northern 

part, 175 mm (0.57 ft) in the central part, and 120 mm (0.39 ft) 

in the southern part (fig. 9A); equivalent subsidence rates 

are about 6 mm/month (0.02 ft/month) for the northern and 

central parts and more than 4 mm/month (0.013 ft/month) for 

the southern part. Sneed (2002) reported that about 80 mm 

(0.26 ft) of subsidence occurred in the northern part between 

1998 and 2000 and is equivalent to a subsidence rate of 

more than 3 mm/month (0.01 ft/month). Sneed (2001; 2002) 

reported that about 35 mm (0.11 ft) of subsidence occurred 

in the southern part between 1996 and 2000 and is equivalent 

to a subsidence rate of nearly 1 mm/month (0.003 ft/month). 

These data indicate that subsidence rates have doubled in 

the northern part and increased by about a factor of 4 in the 

southern part since 2000.

Deformation in the Indio-Coachella Area

Indio-Coachella has not been previously discussed 

as an area of deformation. The shorter timelines of InSAR 

data presented in this report as opposed to those presented 

in Sneed and others, 2001 and Sneed and others 2002, show 

land-surface-elevation changes in the Indio-Coachella area 

which appear to mostly be uplift or stable; however, the 

apparent deformation is suspect. As was mentioned in the 

InSAR Methodology section, interferograms show relative 

deformation, not absolute deformation. Because much of the 

24 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005
basin is subsiding as is shown by the GPS results, it is likely 

that the Indio-Coachella area only appears to be uplifting 

as proximal areas in the basin are subsiding around it. The 

Indio-Coachella area could actually be subsiding at slower 

rates than proximal areas of the basin, which would appear as 

relative uplift in an interferogram. Because the deformation 

interpretations are suspect, this area is not discussed further in 

this report.

Ground-Water Levels

All the areas where significant subsidence was detected 

using InSAR—Palm Desert, Indian Wells, and La Quinta—

coincide with or are near areas where ground-water pumping 

generally caused ground-water levels to decline. Available 

water-level data indicate that water levels measured in 2005 in 

many wells in the Palm Desert, Indian Wells, and La Quinta 

areas were at the lowest levels in their recorded histories 

(fig. 9B). The coincident areas of the subsidence signals and 

the declining water levels, and the localized character of the 

subsidence signals typical of subsidence caused by localized 

pumping, strongly suggest a relation between subsidence and 

ground-water-level declines. The stresses imposed by the 

declining water levels and the significant subsidence at the 

three areas revealed by InSAR indicate that the water levels 

may have exceeded the preconsolidation stress, and if so, the 

subsidence may be permanent.

While ground-water-level data are too sparse to evaluate 

the short-term effect on vertical land-surface changes shown 

by the InSAR results, the available ground-water-level and 

InSAR data can be used to draw some inferences about 

the affected aquifer system. In Palm Desert (Area 1 in 

figs. 6, 7, 8), the area of maximum subsidence is concentric. 

Although water-level data are measured infrequently and 

are not available within the area of the concentric InSAR 

signal, data for the surrounding region indicate that waterlevel declines have been fairly uniform. The concentric 

subsidence shape suggests that the stress primarily causing the 

subsidence is near the center of the concentric shape and that 

sediments constituting the aquifer system in the area are fairly 

homogenous as the sediments responded uniformly to similar 

water-level declines in areas surrounding the center of the 

subsidence bowl. 

In Indian Wells, the areas of subsidence form two 

separate elongated shapes—one parallel to and one 

perpendicular to the mountain front. The available water-level 

data indicate fairly uniform water-level declines in the area, 

suggesting that the aquifer system is heterogeneous in this 

part of the valley because sediments responded dissimilarly 

to similar water-level declines, as exhibited by the irregular 

shapes of the subsidence areas. Additional evidence of aquifer 

heterogeneity in the area is given by the distinct northwestsoutheast linearity shown on the northern margins of the pair 

of subsiding bowls, suggesting the presence of barriers to 

ground-water flow or abrupt changes in lithology that control 

the northern extent of subsidence (Area 2 in fig. 6). 

In La Quinta, water-level data are too sparse to relate to 

the aquifer-system response, but the northwestern part of the 

subsiding area has an irregular shape that appears to be related 

to the contact between the alluvial aquifer and the bedrock 

basement complex that defines the extent of the aquifer system 

(Area 3 in figs. 6, 7, 8). 

Comparison of InSAR and GPS Results

GPS and InSAR measurements can be compared at 

monuments MAGF, MANI, and OSDO, and at the CGPS 

station COTD in Palm Desert (figs. 3, 5, 6, 7, 8). InSAR 

data are uninterpretable at the other monuments in the landsubsidence monitoring network and at CGPS station TMAP 

(near S753) because they are in and near agriculturally 

active areas (which degrades the InSAR data). Because SAR 

data and GPS data for MAGF, MANI, and OSDO were not 

collected simultaneously, magnitudes of land subsidence 

measured by the two methods could not be compared; instead, 

rates of subsidence were compared at these monuments. 

Rates of land subsidence that were derived from GPS data 

measured at GPS monuments were calculated by differencing 

the ellipsoid heights computed from the GPS surveys in 2000 

and 2005 and dividing by 1,813 days—the number of days 

between August 30, 2000 and August 17, 2005. Rates of land 

subsidence derived from InSAR data for the locations of GPS 

monuments were computed by determining the magnitude of 

land subsidence for each interferogram near each monument, 

then dividing that magnitude by the number of days that the 

interferogram spans; 22 subsidence rates (between February 

26, 2003 and September 25, 2005) were calculated from the 

22 interferograms analyzed. At COTD, absolute magnitudes 

of subsidence derived from GPS data and InSAR data were 

compared because continuously collected GPS data permits 

computation of a position for any day of interest.

At MAGF, 138 mm (0.45 ft) of subsidence was 

calculated from the GPS data, resulting in a calculated 

subsidence rate of 0.08 mm/d (2.6 x 10-4 ft/d). The subsidence 

rates calculated from InSAR data ranged from 0.06 mm/d 

to 0.14 mm/d (2.0 x 10-4 ft/d to 4.6 x 10-4 ft/d); the average 

calculated subsidence rate was 0.08 mm/d (2.6 x 10-4 ft/d) 

and the standard deviation was 0.03 mm/d (9.8 x 10-5 ft/d). 

At MANI, 46 mm (0.15 ft) of subsidence was calculated 

from the GPS data, resulting in a calculated subsidence rate 

of 0.03 mm/d (9.8 x 10-5 ft/d); the calculated subsidence rates 

derived from InSAR data ranged from 0 mm/d (0 ft/d) to 

0.07 mm/d (2.3 x 10-4 ft/d); the average and standard deviation 

were 0.02 mm/d (6.6 x 10-5 ft/d). At OSDO, 192 mm (0.63 ft) 

of subsidence was calculated from the GPS data, resulting in 

a calculated subsidence rate of 0.11 mm/d (3.6 x 10-4 ft/d); 

the calculated subsidence rates derived from InSAR data 

InSAR Methodology 25
Figure 9. Hydrographs showing (A) water-surface elevations for selected production wells, and InSAR timeseries showing land 

subsidence for 5/7/2003–9/25/2005, and (B) water-surface elevations for the same production wells for 1970–2005 in the three InSARdetected land subsidence areas in the Coachella Valley, California. 

(See figure 5 for well locations.)

La Quinta (Area 3)

Indian Wells (Area 2)

WATER-SURFACE ELEVATION (FEET RELATIVE TO SEA LEVEL)

YEAR

Palm Desert (Area 1)

LAND SUBSIDENCE, IN FEET

WATER-SURFACE ELEVATION (METERS RELATIVE TO SEA LEVEL)

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60 0

0.1

0.2

0.3

0.4

0.5

0.6

0

0.1

0.2

0.3

0.4

0.5

-50 0.6

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

100

0

10

20

30

5

15

25

-5

-10

-15

0

10

5

15

-5

-10

-15

-20

-25

-180

-170

-160

-150

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30 0

0.1

0.2

0.3

0.4

0.5

0.6

2003 2004 2005

5S/6E-16M1

5S/6E-5Q1

5S/6E-17M2

5S/6E-7M1

5S/6E-8N3

Land subsidence (InSAR timeseries)

5S/6E-23K2

5S/6E-23N1

5S/6E-25A1

5S/6E-24F1

5S/6E-22B1

Western bowl land subsidence 

(InSAR timeseries)

Eastern bowl land subsidence 

 (InSAR timeseries)

6S/7E-6B1

5S/7E-31Q2

6S/7E-16A2

6S/7E-16R2

6S/7E-21D1

North land 

 subsidence 

 (InSAR timeseries)

Central land subsidence 

(InSAR timeseries)

South land subsidence 

 (InSAR timeseries)

-20

-10

-15

-25

-30

-35

-40

-45

-50

-55

LAND SUBSIDENCE, IN MILLIMETERS

0

30

60

90

120

150

180

0

30

60

90

120

150

180

0

30

60

90

120

150

180

A

26 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005
La Quinta (Area 3)

Indian Wells (Area 2)

Palm Desert (Area 1)

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

100

-180

-170

-160

-150

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

WATER-SURFACE ELEVATION (FEET RELATIVE TO SEA LEVEL)

YEAR

1970 1972 197819761974 19821980 1984 1986 1988 1990 1992 199819961994 20022000 2004

5S/6E-16M1

5S/6E-5Q1

5S/6E-17M2

5S/6E-7M1

5S/6E-8N3

5S/6E-23K2

5S/6E-23N1

5S/6E-25A1

5S/6E-24F1

5S/6E-22B1

6S/7E-6B1 5S/7E-31Q2

6S/7E-16A2

6S/7E-16R2

6S/7E-21D1

WATER-SURFACE ELEVATION (METERS RELATIVE TO SEA LEVEL)

0

10

20

30

5

15

25

-5

-10

-15

0

10

5

15

-5

-10

-15

-20

-25

-20

-10

-15

-25

-30

-35

-40

-45

-50

-55

B

Figure 9. Continued.

InSAR Methodology 27
ranged from 0.05 mm/d to 0.21 mm/d (1.6 x 10-4 ft/d to 6.9 x 

10-4 ft/d); the average was 0.11 mm/d (3.6 x 10-4 ft/d) and the 

standard deviation was 0.05 mm/d (1.6 x 10-4 ft/d). 

The coordinates for CGPS station COTD were computed 

by SOPAC for the dates May 7, 2003, and September 25, 

2005, and were compared to the InSAR time series that spans 

those same dates. GPS observations indicated 24 mm (0.08 ft) 

of subsidence, while InSAR measurements indicated 25 mm 

(0.08 ft). 

The calculated subsidence rates for monuments MAGF, 

MANI, OSDO, and the subsidence magnitude at COTD 

calculated using both GPS data and InSAR data compare 

favorably, thereby improving confidence in results derived 

from both methods. The favorable comparison of data for 

these monuments lends credibility to the GPS data collected 

at the other monuments in the network where InSAR data is 

unusable because of incoherence caused by agricultural land 

use.

Future Monitoring

Continued monitoring in the southern Coachella 

Valley is warranted because ground-water levels continue 

to decline to record-low levels in some areas of the valley 

and, therefore, the significant amounts and rising rates of 

land subsidence documented by this study are expected to 

increase. Most of the changes in the vertical positions of the 

GPS network monuments measured in 1996, 1998, and 2000 

were within the measurement errors, indicating that a longer 

period of time would have been needed to see significant 

changes. Comparing the land-surface-elevation changes of 

the monuments in the GPS network in 2005 with those of 

the previous three surveys did show changes greater than 

the anticipated GPS measurement errors. As a result, GPS 

surveys completed every 3-5 years would be sufficient to 

monitor subsidence rates. Spatially detailed InSAR-derived 

maps of ground displacements, however, could continue to 

be processed annually or more frequently depending on data 

availability, because InSAR can detect relative changes in 

vertical position as small as 5 mm (0.02 ft) (Hoffmann and 

others, 2001). Because InSAR-detected areas of subsidence 

spatially overlap the GPS network, future monitoring of the 

GPS network could provide ground truth for the more spatially 

detailed and higher resolution InSAR measurements, as was 

done during this study. Furthermore, as InSAR technology 

matures, it is likely that some InSAR measurements made 

in agriculturally active areas, such as those in the southern 

Coachella Valley, could result in improved spatial detail of 

displacement in these areas.

The frequency of water-level measurements in wells 

in the Coachella Valley is too low to permit meaningful 

interpretations of the aquifer-system response to water-level 

changes, particularly when paired with the more frequent 

InSAR measurements. Furthermore, the wells generally 

have long or multiple screens such that the water-level 

measurement is a composite measurement representing a large 

thickness of the aquifer system. Increasing the measurement 

frequency of ground-water levels in just a few piezometers 

(wells constructed with short screens and small diameters for 

monitoring purposes)—both in areas of known subsidence 

and in areas of relative stability—would significantly improve 

analysis of the relationship between changes in water levels 

and in land-surface elevations. In concert with more frequent 

water-level measurements, more frequent and high-resolution 

measurements of aquifer-system compaction, such as those 

derived from a borehole extensometer, would improve the 

analysis of aquifer-system response. The information derived 

from such a monitoring site(s) would be useful in estimating 

aquifer-system hydraulic parameters that govern ground-water 

flow and land subsidence. This information could be used 

to construct a numerical model of ground-water flow and 

aquifer-system compaction to refine estimates of governing 

parameters and to predict potential aquifer-system compaction 

which could be used by CVWD to manage water resources 

while considering land subsidence.

Summary

Ground water has been a major source of agricultural, 

municipal, and domestic water supply in the Coachella 

Valley since the early 1920s. Ground-water levels declined 

throughout the Coachella Valley from the 1920s until 1949. 

In 1949, the importation of surface water from the Colorado 

River to the southern Coachella Valley began, resulting in 

decreased pumping and a recovery of water levels in some 

areas. Since the 1970s, the demand for water in the southern 

Coachella Valley has exceeded the deliveries of the imported 

surface water, and water levels have again declined. The 

declining water levels have the potential to induce or renew 

land subsidence in the Coachella Valley. Results of previous 

studies by the U.S. Geological Survey indicate that land 

subsidence may have been as much as about 150 mm (0.5 ft) 

in the southern parts of the valley between about 1930 and 

1996 (Ikehara and others, 1997).

The location and magnitude of vertical land-surface 

changes during 1996–2005 were determined using GPS and 

InSAR techniques. The GPS measurements and the images 

processed for the InSAR measurements described in this 

report span the area from Palm Desert on the north to the 

Salton Sea on the south. GPS measurements were more 

useful than InSAR measurements for determining vertical 

land-surface changes in agricultural areas, and InSAR 

measurements were more useful for determining spatially 

detailed changes in nonagricultural areas. GPS measurements 

made at 13 geodetic monuments in 1996 and 2005 in the 

southern Coachella Valley indicate that the elevation of 

the land surface had a net decline of 124 to 9 mm ±54 mm 

(0.41 to 0.03 ft ±0.18 ft) during the 9-year period. Changes 

at 9 of the 13 monuments exceeded the maximum expected 

uncertainty of ±54 mm (±0.18 ft) at the 95-percent confidence 

28 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005
Summary 29

level, indicating that subsidence occurred at these monuments 

between June 1996 and August 2005. GPS measurements 

made at 20 geodetic monuments in 2000 and in 2005 indicate 

that the land-surface elevation changed –192 to +51 mm 

±36 mm (–0.63 to +0.17 ft ±0.12 ft) during the 5-year period. 

Changes at 6 of the 20 monuments exceeded the maximum 

expected uncertainty of ±36 mm (±0.12 ft) at the 95-percent 

confidence level—subsidence occurred at five monuments and 

uplift occurred at one monument between August 2000 and 

August 2005. Data from two of the five subsiding monuments 

for which subsidence rates could be compared indicate that 

subsidence rates decreased during this period compared with 

subsidence rates before 2000. 

Results of the InSAR measurements made between May 

7, 2003, and September 25, 2005, indicate that land subsided 

about 75 to 180 mm (0.25 to 0.59 ft) in three areas of the 

Coachella Valley: near Palm Desert, Indian Wells, and La 

Quinta; the equivalent subsidence rates range from about 3 to 

more than 6 mm/month (0.01 to 0.02 ft/month). The subsiding 

areas near these locations were previously identified using 

InSAR measurements for 1996–2000, which indicated that 

land subsided about 35 to 150 mm (0.11 to 0.49 ft) during the 

four-year period; the equivalent subsidence rates range from 

about 1 to 3 mm/month (0.003 to 0.01 ft/month). Comparison 

of the InSAR results indicates that subsidence rates have 

increased by 2 to 4 times since 2000 in these three areas. 

Water-level measurements made at wells near the 

subsiding GPS monuments and near the areas of subsidence 

shown by InSAR generally indicate that water levels declined 

during 1996-2005. The relation between declining water 

levels and significant subsidence may indicate that the water 

levels have exceeded the preconsolidation stress and that the 

resulting subsidence may be permanent (inelastic). Continued 

monitoring in the southern Coachella Valley is warranted 

because ground-water levels continue to decline to recordlow levels in some areas of the valley and, therefore, the 

significant amounts and increasing rates of land subsidence 

documented by this study are expected to continue.

Acknowledgments 

This study was done in cooperation with the CVWD; 

the authors gratefully acknowledge the CVWD for their 

support and assistance during this study. We acknowledge 

the SCIGN and its sponsors, the W.M. Keck Foundation, the 

National Aeronautics and Space Administration, the National 

Science Foundation, the USGS, and the Southern California 

Earthquake Center for providing data used in this study. We 

thank the University NAVSTAR Consortium (UNAVCO) 

for providing GPS equipment and exceptional technical 

support for the 2005 GPS Survey. Radar data used to produce 

the interferograms shown in this report were obtained from 

the European Space Agency for purposes of research and 

development.

References

Amelung, Falk, Galloway, D.L., Bell, J.W., Zebker, H.A., and 

Laczniak, R.J., 1999, Sensing the ups and downs of Las 

Vegas: InSAR reveals structural control of land subsidence 

and aquifer-system deformation: Geology, v. 27, no. 6, 

p. 483–486.

California Department of Water Resources, 1964, Coachella 

Valley Investigation: California Department of Water 

Resources, Bulletin 108, 145 p.

California Department of Water Resources, 1979, Coachella 

Valley area well standards investigation: Los Angeles, 

California Department of Water Resources, Southern 

District, 40 p.

Craymer, M.R., and Beck, N., 1992, Session versus baseline 

GPS processing, in the Proceedings of the 5th International 

Technical Meeting of the Institute of Navigation: 

Albuquerque, New Mexico, Institute of Navigation GPS-92, 

September 16–18, 1992.

Fielding, E.J., Blom, R.G., and Goldstein, R.M., 1998, Rapid 

subsidence over oil fields measured by SAR interferometry: 

Geophysical Research Letters, v. 25, p. 3215.

Galloway, D.L., Hudnut, K.W., Ingebritsen, S.E., Phillips, 

S.P., Peltzer, G., Rogez, F., and Rosen, P.A., 1998, 

InSAR detection of aquifer system compaction and land 

subsidence, Antelope Valley, Mojave Desert, California: 

Water Resources Research, v. 34, p. 2573–2585.

Galloway, D.L., Jones, D.R., and Ingebritsen, S.E., 1999, Land 

subsidence in the United States: U.S. Geological Survey 

Circular 1182, 175 p.

Galloway, D.L., Jones, D.R., and Ingebritsen, S.E., 2000, 

Measuring land subsidence from space: U.S. Geological 

Survey Fact Sheet 051-00, 4 p.

Hoffmann, J., Zebker H.A., Galloway, D.L., and Amelung, 

F., 2001, Seasonal subsidence and rebound in Las Vegas 

Valley, Nevada, observed by synthetic aperture radar 

interferometry: Water Resources Research, v. 37, no. 6, 

p. 1551–1566.

Holzer, T.L., 1984, Ground failure induced by ground-water 

withdrawal from unconsolidated sediment: Reviews in 

Engineering Geology, v. 6, p. 67–105.

Ikehara, M.E., Predmore, S.K., and Swope, D.J., 1997, 

Geodetic network to evaluate historical elevation changes 

and to monitor land subsidence in Lower Coachella Valley, 

California, 1996: U.S. Geological Survey Water-Resources 

Investigations Report 97-4237, scale 1:63,000, 1 sheet 

[folded in envelope].
30 Detection and Measurement of Land Subsidence Using GPS and InSAR, Coachella Valley, California, 1996–2005

Leake, S.A., and Prudic, D.E., 1991, Documentation of a 

computer program to simulate aquifer-system compaction 

using the modular finite-difference ground-water flow 

model: U.S. Geological Survey Techniques of WaterResources Investigations, book 6, chap A2, 68 p.

Massonnet, D., Briole, P., and Arnaud, A., 1995, Deflation of 

Mount Etna monitored by spaceborne radar interferometry: 

Nature, v. 375, p. 567–570.

Massonnet, D., Holzer, T., and Vadon, H., 1997, Land 

subsidence caused by the East Mesa geothermal 

field, California, observed using SAR interferometry: 

Geophysical Research Letters, v. 24, p. 901–904.

Massonnet, D., Rossi, M., Carmona, C., Adragna, F., Peltzer, 

G., Feigl, K., and Rabaute, T., 1993, The displacement field 

of the Landers earthquake mapped by radar interferometry: 

Nature, v. 364, p. 138–142.

McKibben, M.A., 1993, The Salton Trough rift, in Reynolds, 

R.E., and Reynolds, Jennifer, eds., Ashes, faults and basins: 

San Bernardino County Museum Association Special 

Publication, v. 93-1, p. 76–80.

Meinzer, O.E., 1928, Compressibility and elasticity of artesian 

aquifers: Economic Geology, v. 23, no. 3, p. 263–291.

Poland, J.F., ed., 1984, Guidebook to studies of land 

subsidence due to ground-water withdrawal, v. 40 of 

UNESCO Studies and Reports in Hydrology: Paris, France, 

United Nations Educational, Scientific and Cultural 

Organization, 305 p., 5 appendixes.

Riley, F.S., 1998, Mechanics of aquifer systems—The 

scientific legacy of Joseph F. Poland, in Borchers, J., ed., 

Land subsidence—Case Studies and Current Research: 

Proceedings of the Dr. Joseph F. Poland Symposium on 

Land subsidence, Association of Engineering Geologists 

Special Publication 8, p. 13–227.

Rosen, P.A., Hensley, Scott, Joughin, I.R., Li, F.L., Madsen, 

S.N., Rodriguez, Ernesto, and Goldstein, R.M., 2000, 

Synthetic aperture radar interferometry: Proceedings of the 

of Civil Engineers, v. 88, no. 3, p. 333–382.

Shen, Z.-K., Agnew, D.C., King, R.W., Dong, D., Herring, 

T.A., Wang, M., Johnson, H., Anderson, G., Nikolaidis, 

R., van Domselaar, M., Hudnut, K.W., and Jackson, D.D., 

2003, The SCEC crustal motion map, Version 3.0, http://

epicenter.usc.edu/cmm3, accessed April 19, 2007.

Sneed, Michelle, Ikehara, M.E., Galloway, D.L., and 

Amelung, Falk, 2001, Detection and measurement of 

land subsidence using global positioning system and 

interferometric synthetic aperture radar, Coachella Valley, 

California, 1996–98: U.S. Geological Survey WaterResources Investigations Report 01-4193, 26 p.

Sneed, Michelle, Stork, S.V., and Ikehara, M.E. 2002, 

Detection and measurement of land subsidence using global 

positioning system and interferometric synthetic aperture 

radar, Coachella Valley, California, 1998–2000: U.S. 

Geological Survey Water-Resources Investigations Report 

02–4239, 29 p.

Terzaghi, Karl, 1925, Principles of soil mechanics, IV—

Settlement and consolidation of clay: Engineering NewsRecord, 95 (3), p. 874–878.

Tyley, S.J., 1971, Analog model study of the ground-water 

basin of the upper Coachella Valley, California: U.S. 

Geological Survey Open-File Report, 89 p.

Zebker, H.A., Rosen, P.A., and Hensley, S., 1997, Atmospheric 

effects in interferometric synthetic aperture radar surface 

deformation and topographic maps: Journal of Geophysical 

Research, v. 102, p. 7547–7563.

Zilkoski, D.B., D’Onofrio, J.D., and Frakes, S.J., 1997, 

Guidelines for establishing GPS-derived ellipsoid heights, 

(Standards: 2 cm and 5 cm) version 4.3: Silver Spring, Md., 

National Geodetic Survey, 10 p, 3 appendices.