Water-Level Altitudes 2017 and Water-Level Changes in the 

Chicot, Evangeline, and Jasper Aquifers and Compaction 

1973–2016 in the Chicot and Evangeline Aquifers, HoustonGalveston Region, Texas

Prepared in cooperation with the Harris-Galveston Subsidence District,

City of Houston, Fort Bend Subsidence District, Lone Star Groundwater

Conservation District, and Brazoria County Groundwater Conservation District

Water-Level Altitudes 2017 and Water-Level Changes in the 

Chicot, Evangeline, and Jasper Aquifers and Compaction 

1973–2016 in the Chicot and Evangeline Aquifers, HoustonGalveston Region, Texas

Scientific Investigations Report 2017–5080

U.S. Department of the Interior

U.S. Geological Survey
Front cover: 

Top left, Abandoned well, Grimes County, Tex., 1987 (photograph by Dexter W. Brown, U.S. Geological 

Survey).

Top middle, Piezometer and steel tape near Texas City, Tex., July 22, 2005 (photograph by Dexter W. 

Brown, U.S. Geological Survey).

Top right, U.S. Geological Survey hydrologist Jason Ramage taking a water-level measurement with a 

steel tape near Freeport, Tex., January 3, 2016 (photograph by Sachin D. Shah, U.S. Geological Survey).

Bottom right, Abandoned well showing the effects of subsidence near Houston, Texas (photograph by 

the U.S. Geological Survey).

Bottom left, San Jacinto River Authority piezometer near Conroe, Tex., June 2014 (photograph by 

Dexter W. Brown, U.S. Geological Survey).
Water-Level Altitudes 2017 and WaterLevel Changes in the Chicot, Evangeline, 

and Jasper Aquifers and Compaction 1973–

2016 in the Chicot and Evangeline Aquifers, 

Houston-Galveston Region, Texas

By Mark C. Kasmarek and Jason K. Ramage

Prepared in cooperation with the Harris-Galveston Subsidence District,

City of Houston, Fort Bend Subsidence District, Lone Star Groundwater

Conservation District, and Brazoria County Groundwater Conservation District

Scientific Investigations Report 2017–5080

U.S. Department of the Interior

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

RYAN K. ZINKE, Secretary

U.S. Geological Survey

William H. Werkheiser, Acting Director

U.S. Geological Survey, Reston, Virginia: 2017

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

resources, natural hazards, and the environment—visit https://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit https://store.usgs.gov.

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

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Kasmarek, M.C., and Ramage, J.K., 2017, Water-level altitudes 2017 and water-level changes in the Chicot, 

Evangeline, and Jasper aquifers and compaction 1973–2016 in the Chicot and Evangeline aquifers, HoustonGalveston region, Texas: U.S. Geological Survey Scientific Investigations Report 2017–5080, 32 p., https://doi.

org/10.3133/sir20175080. 

ISSN 2328-031X (print)

ISSN 2328-0328 (online)
iii

Acknowledgments

The authors thank the owners and operators of wells throughout the study area for granting 

access and providing pertinent information that expedited data-collection activities.

Additionally, the authors gratefully acknowledge the assistance of the following U.S. Geological 

Survey colleagues for collecting water-level data outside of normal duty hours as necessary 

and for assisting in processing and analyzing the large amount of resulting data within an 

abbreviated period: Dexter W. Brown, Robert H. Ellis, Keith E. Mecum, Kurt A. Kraske, Lisa L. 

Ashmore, Mike K. Burnich, Jody L. Avant, Leena Vinova, Mackenzie K. Mullins, Eric M. Boeding, 

and Jason D. Payne.

v

Contents

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

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

Purpose and Scope .............................................................................................................................5

Hydrogeology of the Study Area .......................................................................................................5

Subsidence and Compaction Processes .......................................................................................10

Data-Collection and Analysis Methods ..................................................................................................11

Determination of Water-Level Altitudes .........................................................................................12

Quality Assurance ..............................................................................................................................12

Depicting Changes in Water-Level Altitudes ................................................................................12

Borehole Extensometers ..................................................................................................................12

Water-Level Altitudes and Changes ........................................................................................................14

Chicot Aquifer .....................................................................................................................................16

Evangeline Aquifer .............................................................................................................................16

Jasper Aquifer ....................................................................................................................................16

Compaction of Subsurface Sediments in the Chicot and Evangeline Aquifers ...............................23

Data Limitations ...........................................................................................................................................26

Summary .......................................................................................................................................................27

References Cited .........................................................................................................................................29

Figures

1. Map showing locations of groundwater regulatory districts; approximate traces 

of hydrogeologic sections A–A ́, B–B ́, and C–C ́; and outcrops and updip limits 

of the aquifers in the Gulf Coast aquifer system in the Houston-Galveston region 

study area, Texas, 2017 ...............................................................................................................3

2. Hydrogeologic section A–A ́ of the Gulf Coast aquifer system in Grimes, 

Montgomery, Harris, and Galveston Counties, Texas ............................................................6

3. Hydrogeologic section B–B ́ of the Gulf Coast aquifer system in Fort Bend 

County, Texas ................................................................................................................................7

4. Hydrogeologic section C–C ́ of the Gulf Coast aquifer system in Montgomery 

and Harris Counties, Texas .........................................................................................................8

5. Stratigraphic column showing geologic and hydrogeologic units of the Gulf 

Coast aquifer system in the Houston-Galveston region study area, Texas .......................9

6. Diagram showing mechanism of subsidence caused by potentiometric surface 

declines induced by groundwater withdrawals in an aquifer composed of gravel, 

sand, silt, and clay .....................................................................................................................11

7. Diagram showing cross-sectional perspective of the borehole extensometer/

piezometer (LJ–65–23–322) located at Pasadena, Texas ...................................................13

8. Map showing locations of borehole-extensometer sites and respective areas 

of jurisdiction for each groundwater regulatory district, Houston-Galveston 

region, Texas, 2016 .....................................................................................................................15

9. Map showing approximate 2017 water-level altitudes and updip limit of the 

Chicot aquifer, Houston-Galveston region, Texas ................................................................17
vi

10. Map showing approximate 1977–2017 water-level changes in the Chicot aquifer, 

Houston-Galveston region, Texas ...........................................................................................18

11. Map showing approximate 2017 water-level altitudes and updip limit of the 

Evangeline aquifer, Houston-Galveston region, Texas ........................................................19

12. Map showing approximate 1977–2017 water-level changes in the Evangeline 

aquifer, Houston-Galveston region, Texas .............................................................................20

13. Map showing approximate 2017 water-level altitudes and updip limit of the 

Jasper aquifer, Houston-Galveston region, Texas ...............................................................21

14. Map showing approximate 2000–17 water-level changes in the Jasper aquifer, 

Houston-Galveston region, Texas ...........................................................................................22

15. Graph showing measured cumulative compaction of subsurface sediments at 

the Lake Houston, Northeast, East End, Southwest, Johnson Space Center, and 

Addicks borehole-extensometer sites, 1973–2016 ...............................................................24

16. Graphs showing measured cumulative compaction of subsurface sediments 

at the A, Texas City-Moses Lake, Baytown C–1 (shallow), Baytown C–2 (deep), 

and Seabrook borehole-extensometer sites; B, Clear Lake (shallow) and Clear 

Lake (deep) borehole-extensometer sites; and C, Pasadena boreholeextensometer site, 1973–2016 ..................................................................................................25
vii

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 2.590 square kilometer (km2) 

Transmissivity

foot squared per day (ft2

/d) 0.09290 meter squared per day (m2/d) 

International System of Units to U.S. customary units

Multiply By To obtain

Volume

liter (L) 33.81 ounce, fluid (fl. oz)

liter (L) 2.113 pint (pt)

liter (L) 1.057 quart (qt)

liter (L) 0.2642 gallon (gal)

liter (L) 61.02 cubic inch (in3

) 

Mass

milligram (mg) 0. 00003527 ounce, avoirdupois (oz)

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

°C = (°F - 32) / 1.8.

Datum

Vertical coordinate information is referenced to either the National Geodetic Vertical Datum of 

1929 (NGVD 29) or the North American Vertical Datum of 1988 (NAVD 88).

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

Water-Level Altitudes 2017 and Water-Level Changes 

in the Chicot, Evangeline, and Jasper Aquifers and 

Compaction 1973–2016 in the Chicot and Evangeline 

Aquifers, Houston-Galveston Region, Texas

By Mark C. Kasmarek and Jason K. Ramage

Abstract

Most of the land-surface subsidence in the HoustonGalveston region, Texas, has occurred as a direct result of 

groundwater withdrawals for municipal supply, commercial 

and industrial use, and irrigation that depressured and 

dewatered the Chicot and Evangeline aquifers, thereby causing 

compaction of the aquifer sediments, mostly in the finegrained silt and clay layers. This report, prepared by the U.S. 

Geological Survey in cooperation with the Harris-Galveston 

Subsidence District, City of Houston, Fort Bend Subsidence 

District, Lone Star Groundwater Conservation District, and 

Brazoria County Groundwater Conservation District, is one 

in an annual series of reports depicting water-level altitudes 

and water-level changes in the Chicot, Evangeline, and Jasper 

aquifers and measured cumulative compaction of subsurface 

sediments in the Chicot and Evangeline aquifers in the 

Houston-Galveston region. This report contains regionalscale maps depicting approximate 2017 water-level altitudes 

(represented by measurements made during December 2016 

through March 2017) and long-term water-level changes for 

the Chicot, Evangeline, and Jasper aquifers; a map depicting 

locations of borehole-extensometer (hereinafter referred to as 

“extensometer”) sites; and graphs depicting measured longterm cumulative compaction of subsurface sediments at the 

extensometers during 1973–2016. 

In 2017, water-level-altitude contours for the Chicot 

aquifer ranged from 200 feet (ft) below the North American 

Vertical Datum of 1988 (hereinafter referred to as “datum”) in 

two localized areas in southwestern and northwestern Harris 

County to 200 ft above datum in west-central Montgomery 

County. The largest water-level-altitude decline (120 ft) 

depicted by the 1977–2017 water-level-change contours for 

the Chicot aquifer was in northwestern Harris County. A broad 

area where water-level altitudes declined in the Chicot aquifer 

extends from northwestern, north-central, and southwestern 

Harris County across parts of north-central, eastern, and 

south-central Fort Bend County into southeastern Waller 

County. Adjacent to the areas where water levels declined was 

a broad area where water levels rose in central, eastern, and 

southeastern Harris County, most of Galveston County, eastern 

and northernmost Brazoria County, and northeastern Fort 

Bend County. The largest rise (200 ft) in water-level altitudes 

in the Chicot aquifer from 1977 to 2017 was in southeastern 

Harris County. 

The water-level-altitude contours for the Evangeline 

aquifer in 2017 indicated two areas where the water-level 

altitudes were 250 ft below datum—one area extending from 

south-central Montgomery County into north-central Harris 

County and another area in western Harris County. Water-level 

altitudes in the Evangeline aquifer ranged from 50 to 200 ft 

below datum throughout most of Harris County in 2017. In 

Montgomery County, water-level altitudes in the Evangeline 

aquifer in 2017 ranged from the aforementioned area where 

they were 250 ft below datum to an area where they were 

200 ft above datum in the northwestern part of the county. The 

1977–2017 water-level-change contours for the Evangeline 

aquifer depict a broad area where water-level altitudes 

declined in north-central Harris and south-central Montgomery 

Counties, extending through north-central, northwestern, and 

southwestern Harris County into western Liberty, southeastern 

and northeastern Waller, and northeastern and east-central 

Fort Bend Counties. The largest water-level-altitude decline 

(280 ft) was in north-central Harris and south-central 

Montgomery Counties. Water-level altitudes rose in a broad 

area from central, east-central, and southern Harris County 

extending into the northernmost part of Brazoria County, the 

northernmost part of Galveston County, and the southwestern 

area of Liberty County. The largest rise in water-level altitudes 

in the Evangeline aquifer from 1977 to 2017 (240 ft) was in 

southeastern Harris County.

Water-level-altitude contours for the Jasper aquifer in 

2017 ranged from 200 ft below datum in three isolated areas 

of south-central Montgomery County (the westernmost of 

these areas extended slightly into north-central Harris County) 

to 250 ft above datum in extreme northwestern Montgomery 

County, northeastern Grimes County, and southwestern 

Walker County. The 2000–17 water-level-change contours 
2 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

for the Jasper aquifer depict water-level declines in a broad 

area throughout most of Montgomery County and in parts of 

Waller, Grimes, and Harris Counties, with the largest decline 

(220 ft) in an isolated area in south-central Montgomery 

County.

Compaction of subsurface sediments (mostly in the 

fine-grained silt and clay layers) in the Chicot and Evangeline 

aquifers was recorded continuously by using 13 extensometers 

at 11 sites that were either activated or installed between 1973 

and 1980. During the period of record beginning in 1973 (or 

later depending on activation or installation date) and ending 

in late November or December 2016, measured cumulative 

compaction at the 13 extensometers ranged from 0.096 ft at 

the Texas City-Moses Lake extensometer to 3.700 ft at the 

Addicks extensometer. From January through late November 

or December 2016, the Addicks, Lake Houston, Southwest, 

and Northeast extensometers recorded net decreases in landsurface elevation, but the Baytown C–1 (shallow), Baytown 

C–2 (deep), Clear Lake (shallow), Clear Lake (deep), East 

End, Johnson Space Center, Pasadena, Seabrook, and Texas 

City-Moses Lake extensometers recorded net increases in 

land-surface elevation.

The rate of compaction varies from site to site because 

of differences in rates of groundwater withdrawal in the areas 

adjacent to each extensometer site; differences among sites 

in the ratios of sand, silt, and clay and their corresponding 

compressibilities; and previously established preconsolidation 

heads. It is not appropriate, therefore, to extrapolate or infer a 

rate of compaction for an adjacent area on the basis of the rate 

of compaction recorded by proximal extensometers.

Introduction

Allen (1969) described ground-surface displacement 

as the last step of a variety of subsurface displacement 

mechanisms that included (among others) compaction 

of aquifer sediments by loading, drainage, vibration, and 

hydrocompaction. The Houston-Galveston region, Texas—

consisting of Harris, Galveston, Fort Bend, Montgomery, 

Brazoria, Chambers, Grimes, Liberty, San Jacinto, Walker, 

and Waller Counties (fig. 1)—represents one of the largest 

areas of ground-surface displacement (also called land-surface 

subsidence and hereinafter referred to as “subsidence”) in 

the United States (Coplin and Galloway, 1999). According 

to Coplin and Galloway (1999, p. 40), by 1979, as much 

as 10 feet (ft) of subsidence had occurred in the HoustonGalveston region, and approximately 3,200 square miles (mi2

) 

of the 11,000-mi2 geographic area had subsided more than 

1 ft. Comparing land-surface elevations for 1915–17 to those 

for 2001, Kasmarek, Gabrysch, and Johnson (2010, sheet 2) 

determined that as much as 13 ft of subsidence in a small, 

localized area had occurred in southeastern Harris County 

during the historical period. 

Subsidence has been linked to hydrocarbon extraction 

and groundwater withdrawals in the Houston-Galveston region 

and was first documented in the region in 1926, at the Goose 

Creek Oil Field in southeastern Harris County (fig. 1) (Pratt 

and Johnson, 1926). Although subsidence was first identified 

in the Houston-Galveston region as a result of hydrocarbon 

extraction at this particular oil field, most of the subsidence in 

the Houston-Galveston region is a direct result of groundwater 

withdrawals that have depressured and dewatered the Chicot 

and Evangeline aquifers, thereby causing compaction of the 

aquifer sediments (Winslow and Doyel, 1954; Winslow and 

Wood, 1959; Gabrysch and Bonnet, 1975; Gabrysch, 1984; 

Holzer and Bluntzer, 1984; Kasmarek, Gabrysch, and Johnson, 

2010).

Groundwater withdrawn from the Chicot, Evangeline, 

and Jasper aquifers has been the primary source of water 

for municipal supply, commercial and industrial use, and 

irrigation in the Houston-Galveston region since the early 

1900s (Kasmarek and Robinson, 2004). Prior to 1975, the 

withdrawal of groundwater from the Chicot and Evangeline 

aquifers was unregulated, and water levels in the aquifers 

were declining with associated depressuring, dewatering, and 

compaction resulting in subsidence (Coplin and Galloway, 

1999). By 1977, groundwater withdrawals had caused waterlevel altitudes in southeastern Harris County to decline by as 

much as 300 ft in the Chicot aquifer and by as much as 350 ft 

in the Evangeline aquifer (as indicated by long-term changes 

in water-level-altitude contours referenced to the North 

American Vertical Datum of 1988 [NAVD 88]) (Gabrysch, 

1979). Attendant with these declines in water-level altitudes, 

by 1979, as much as 10 ft of subsidence had occurred in the 

Houston-Galveston region (Coplin and Galloway, 1999).

Subsidence is of particular concern in low-lying coastal 

areas such as the Houston-Galveston region. Subsidence 

in the region has increased the frequency and severity of 

flooding (Coplin and Galloway, 1999). Low-pressure weather 

systems such as tropical storms and hurricanes result in high 

rates of precipitation and cause high tides to reach farther 

inland. Storm surge is an abnormal rise of water generated 

by a storm, over and above the normal astronomical tides 

(National Oceanic and Atmospheric Administration, 2001, 

2015). Subsidence exacerbates the effects of storm surge and 

impedes stormwater runoff by creating areas of decreased 

land-surface elevations where water accumulates. Subsidence 

has shifted the shoreline along Galveston Bay, as evidenced 

by the inundation of the Brownwood Subdivision associated 

with Hurricane Alicia in August 1983 near Baytown, Tex., 

and adjacent areas in the Houston-Galveston region (fig. 1), 

thereby changing the distribution of wetlands and aquatic 

vegetation (Coplin and Galloway, 1999).

To address the issues associated with subsidence 

and subsequent increased flooding, the 64th Texas State 

Legislature in 1975 authorized the establishment of the 

Harris-Galveston Subsidence District (HGSD) (fig. 1) to 

regulate and reduce groundwater withdrawals in Harris and 

Galveston Counties (Harris-Galveston Subsidence District, 

2013). In cooperation with the HGSD, the U.S. Geological 

Survey (USGS) has monitored water levels in wells screened 
Introduction 3

GALVESTON

COUNTY

BRAZORIA

COUNTY

FORT BEND

COUNTY

CHAMBERS COUNTY

WALLER COUNTY

LIBERTY COUNTY

MONTGOMERY COUNTY

GRIMES COUNTY

SAN JACINTO COUNTY

WALKER

COUNTY

HARRIS

COUNTY

FM 521

FM 787

FM 2004

90

105

45

249

59

10

99

90

548

321

FM 1960

FM 1764

FM 35

150 FM 1375

225

87

168

90

19

156

6

State Loop 336

36

105

90 59

290

59

45

10

610

45

Galveston Rd

Grand Pky

36

N Sam Houston Pky W

S Sam Houston Pky E

E North Belt

Addicks Satsuma Rd

S Belt

146

288

45

190

75

30

90

10

610

35

35

332

6

59

3

146

105

146

61

65

1488

1774

RIVER

BRAZOS

RIVER

SAN

BERNARD

RIVER

BRAZOS

RIVER

TRINITY

RIVER

WEST

FORK

SAN

JACINTO

RIVER

WEST FORK SAN

JACINTO

RIVER

Cedar

Bayou

Buffalo

Bayou

Clear

Creek

Lake

Creek

Lake Creek

Caney

Creek

Spring

Creek

Oyster

Creek

BRAZOS

FREEPORT

CLUTE

LAKE JACKSON

ANGLETON

GALVESTON

TEXAS CITY

ALVIN

LEAGUE CITY

ROSENBERG FRIENDSWOOD

PEARLAND

RICHMOND

MISSOURI

CITY

SUGAR

LAND

WEST UNIVERSITY PLACE

BELLAIRE DEER PARK

PASADENA

GALENA

PARK BAYTOWN

CHANNELVIEW

KATY

ALDINE

HUMBLE

HOUSTON

SPRING

CONROE

HUNTSVILLE

TOMBALL

THE 

WOODLANDS

MANVEL

HITCHCOCK

SANTA FE

LA MARQUE

LIBERTY

DAYTON

MONT 

BELVIEU

JERSEY 

VILLAGE

PRAIRIE 

VIEW WALLER

HEMPSTEAD

MAGNOLIA

FULSHEAR

PATTISON

SHEPHERD

CLEVELAND

PLUM 

GROVE

MONTGOMERY

WILLIS

NAVASOTA

SHELDON

RESERVOIR

TRINITY BAY

LAKE

HOUSTON

LAKE

CONROE

LAKE

LIVINGSTON

GALVESTON BAY

EAST BAY

WEST BAY

GULF OF MEXICO

30

A

A'

10

1

2

3

4

5

6

7

8

9

11

Hydrogeologic 

section on figure 2

0 8 16 24 MILES

0 8 16 24 KILOMETERS

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

Universal Transverse Mercator projection, Zone 15

North American Datum of 1983 Note: Aquifer data from Strom and others, 2003a, b, c;

Kasmarek and Robinson, 2004

 HarrisGalveston 

Subsidence 

District

Fort Bend 

Subsidence

District

Lone Star Groundwater 

Conservation 

District

Brazoria 

 County 

 Groundwater 

 Conservation 

 District

Area A

Area B

Area 3

Area 2

Area 1

Goose Creek Oil Field

Brownwood Subdivision

95°45'

95°45'

95°30'

95°30' 95°15'

95°

95°

30°30'

30°

30°

30°15'

30°15'

29°30'

29°45'

29°45'

29°15'

96°

96°

94°45'

94°45'

94°30'

94°30'

30°30'

29°15'

30°45'

29° 29°

30°45'

29°30'

95°15'

EXPLANATION

Approximate traces of hydrogeologic sections

 on figures 2–4

6 Approximate locations of wells on figures 2–4

Outcrop and updip limit of the Chicot aquifer

Outcrop and updip limit of the Evangeline aquifer

Outcrop and updip limit of the Burkeville 

 confining unit

Outcrop and updip limit of the Jasper aquifer

Study area

LOCATION MAP

TEXAS

Outcrop of the Catahoula confining system

1

2

3

4

6

B

B'

5 Hydrogeologic 

section on figure 3

1

2

3

4

5

6

7

8

9

10

C

C'

Hydrogeologic 

section on figure 4

Figure 1. Locations of groundwater regulatory districts; approximate traces of hydrogeologic sections A–A ́, B–B ́, and C–C ́; and 

outcrops and updip limits of the aquifers in the Gulf Coast aquifer system in the Houston-Galveston region study area, Texas, 2017

(modified from Strom and others, 2003a, b, c; Kasmarek and Robinson, 2004).
4 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

in the Chicot and Evangeline aquifers and compaction of 

subsurface sediments in Harris and Galveston Counties since 

1976. The USGS has published annual reports depicting 

water-level altitudes and water-level changes for the Chicot 

and Evangeline aquifers in the Houston-Galveston region 

beginning with the 1977 water-level-altitude maps (Gabrysch, 

1979). Subsequently, the monitoring of groundwater levels 

was expanded into the Fort Bend subregion (encompassing 

Fort Bend County and adjacent areas), and the first waterlevel-altitude maps for this area were created and presented 

in the 1991 water-level report (Barbie and others, 1991) and 

subsequently revised in 1997 (Kasmarek, 1997). The USGS 

published its first report on water-level altitudes and waterlevel changes for the Jasper aquifer in the Houston-Galveston 

region (primarily Montgomery County) in 2001 (Coplin, 

2001). Water-level altitudes and water-level changes for the 

Jasper aquifer were subsequently the subject of a detailed 

assessment on water-level altitudes in 2007 and water-level 

changes in the Chicot, Evangeline, and Jasper aquifers; this 

assessment was part of report that also depicted compaction 

during 1973–2006 in the Chicot and Evangeline aquifers 

(Kasmarek and Houston, 2007).

The cumulative compaction data from a network 

of 13 borehole extensometers (hereinafter referred to as 

“extensometers”) in the Houston-Galveston region have been 

presented in USGS reports of annual water-level altitudes 

and water-level changes since 1981 (cumulative compaction 

during 1973–81; Gabrysch and Ranzau, 1981). Earlier USGS 

reports documented the occurrence of subsidence in the 

study area determined by the reoccupation and releveling of 

a network of benchmarks by using spirit-leveling techniques 

during the periods 1906–51 (Winslow and Doyel, 1954), 

1906–78, 1943–78, and 1973–78 (Gabrysch, 1984). Most 

recently, Kasmarek and others (2016) depicted 2016 waterlevel altitudes and changes for various periods in the Chicot, 

Evangeline, and Jasper aquifers and cumulative compaction 

recorded by the 13 extensometers during 1973–2015 in the 

Chicot and Evangeline aquifers.

Subsequent to establishing the HGSD, the Texas State 

Legislature established an additional subsidence district (Fort 

Bend Subsidence District [FBSD]) and two groundwater 

conservation districts (Lone Star Groundwater Conservation 

District [LSGCD] and, most recently, Brazoria County 

Groundwater Conservation District [BCGCD]) in the 

Houston-Galveston region to provide for the regulation of 

groundwater withdrawals in areas within their jurisdiction. 

The FBSD was established by the 71st Texas State Legislature 

in 1989 and has jurisdiction throughout Fort Bend County 

(fig. 1). The FBSD is divided into area A, which includes 

the Richmond-Rosenberg subarea, and area B. The primary 

purpose of the FBSD is to regulate groundwater withdrawals 

to prevent subsidence that contributes to flooding (Fort Bend 

Subsidence District, 2013). The LSGCD was established by 

the 77th Texas State Legislature in 2001 and has jurisdiction 

throughout Montgomery County (fig. 1). The purpose of the 

LSGCD is to conserve, protect, and enhance the groundwater 

resources of Montgomery County (Lone Star Groundwater 

Conservation District, 2013). The BCGCD was established 

by the 78th Texas State Legislature in 2003 with the purpose 

to maintain the quality and availability of Brazoria County’s 

(fig. 1) groundwater resources for current users and future 

generations (Brazoria County Groundwater Conservation 

District, 2012). Regulatory plans to gradually decrease 

groundwater withdrawals by increased usage of alternative 

surface-water supplies are being phased in; the current (2017) 

groundwater management plans of each district are available 

on their respective websites (Brazoria County Groundwater 

Conservation District, 2012; Fort Bend Subsidence District, 

2013; Harris-Galveston Subsidence District, 2013; Lone 

Star Groundwater Conservation District, 2013). Currently 

(2017), groundwater withdrawals are not being regulated by 

a groundwater conservation district in Liberty and Chambers 

Counties.

In 1976, the HGSD began implementing its first 

groundwater regulatory plan (Harris-Galveston Subsidence 

District, 2013). An extensive well-monitoring network was 

established by 1977, and water-level data were collected 

and used to create the first published water-level-altitude 

maps of the Chicot and Evangeline aquifers in the HoustonGalveston region (Gabrysch, 1979). The FBSD adopted 

its groundwater management plan in 1990 (Fort Bend 

Subsidence District, 2013), and in cooperation with the 

FBSD, an increased number of wells were inventoried by the 

USGS in Fort Bend, Harris, Brazoria, and Waller Counties 

in 1989 and 1990. A more comprehensive water-levelaltitude report for the Chicot and Evangeline aquifers was 

published by the USGS in 1991 (Barbie and others, 1991), 

and when updated well data became available, that waterlevel-altitude report was revised in 1997 (Kasmarek, 1997). 

Similarly, after the establishment of the LSGCD in 2001, 

the USGS first published a water-level-altitude map of the 

Jasper aquifer in the Houston-Galveston region (primarily 

Montgomery County) (Coplin, 2001). In 2004, 2006, and 

2007, as additional wells with reliable water-level data 

were inventoried, revised water-level-altitude maps for the 

Jasper aquifer were prepared (Kasmarek and Lanning-Rush, 

2004; Kasmarek and others, 2006; Kasmarek and Houston, 

2007). In comparison to the 2001 (Coplin, 2001) and 2004 

(Kasmarek and Lanning-Rush, 2004) reports, the 2007 waterlevel-altitude map (Kasmarek and Houston, 2007) was the 

most comprehensive for the Jasper aquifer in the study area 

prepared at that time. Since 2007, similarly comprehensive 

maps for the Jasper aquifer have been included in an annual 

series of reports that depict water-level altitudes and waterlevel changes in the Chicot, Evangeline, and Jasper aquifers 

and cumulative compaction in the Chicot and Evangeline 

aquifers in the Houston-Galveston region (Kasmarek and 

Houston, 2008; Kasmarek, Johnson, and Ramage, 2010; 

Johnson and others, 2011; Kasmarek and others, 2011, 2012, 

2013, 2014, 2015, 2016). 
Introduction 5

Purpose and Scope

This report, prepared by the USGS in cooperation 

with the HGSD, City of Houston, FBSD, LSGCD, and 

BCGCD, is one in an annual series of reports depicting 

water-level altitudes and water-level changes (the differences 

between water-level altitudes at specific points [wells]) in 

the Chicot, Evangeline, and Jasper aquifers and measured 

cumulative compaction (hereinafter referred to as “cumulative 

compaction”) of fine-grained subsurface sediments in the 

Chicot and Evangeline aquifers in the Houston-Galveston 

region. A summary of the hydrogeology of the study area is 

provided, and the mechanism of compaction and subsidence 

is described. Regional-scale maps depicting approximate 

contoured 2017 water-level altitudes in the Chicot, 

Evangeline, and Jasper aquifers are featured, along with maps 

depicting approximate contoured long-term (1977–2017) 

water-level changes for the Chicot and Evangeline aquifers 

and a map depicting approximate contoured long-term (2000–

17) water-level changes for the Jasper aquifer. 

In addition to maps depicting water-level altitudes and 

long-term water-level changes in the Chicot, Evangeline, 

and Jasper aquifers, this report contains a map depicting 

the locations of the 13 extensometers at 11 sites in Harris 

and Galveston Counties that were activated or installed 

between 1973 and 1980. At these sites, the 13 extensometers 

continuously record cumulative compaction of subsurface 

sediments of the Chicot and Evangeline aquifers. Graphs 

are presented of the long-term cumulative compaction 

data recorded by the 13 extensometers from 1973 (or later 

depending on activation or installation date) through 2016. 

For all three aquifers (Chicot, Evangeline, and Jasper), the 

point data (individual water-level altitudes measured at each 

well), contour data, and associated metadata are available 

for download in a companion data release (Kasmarek and 

Ramage, 2017). The metadata are compliant with geospatial 

metadata standards (Federal Geographic Data Committee, 

2015). Compaction data for the 13 extensometers are available 

in a second companion data release (Ramage, 2017).

Hydrogeology of the Study Area

The three primary aquifers in the Gulf Coast aquifer 

system in the Houston-Galveston region study area are 

the Chicot, Evangeline, and Jasper (figs. 2–5), which are 

composed of laterally discontinuous deposits of gravel, sand, 

silt, and clay. The youngest and uppermost aquifer, the Chicot 

aquifer, consists of Holocene- and Pleistocene-age sediments; 

the underlying Evangeline aquifer consists of Pliocene- and 

Miocene-age sediments; and the oldest and most deeply buried 

of the three aquifers, the Jasper aquifer, consists of Mioceneage sediments (fig. 2) (Baker, 1979, 1986). The lowermost unit 

of the Gulf Coast aquifer system is the Miocene-age Catahoula 

confining system, which includes the Catahoula Sandstone. 

The Catahoula confining system consists of sands in the upper 

section and clay and tuff interbedded with sand in the lower 

section (figs. 2 and 4).

The percentage of clay and other fine-grained clastic 

material generally increases with depth downdip (Baker, 

1979). Through time, geologic and hydrologic processes 

created accretionary sediment wedges (stacked sequences 

of sediments) more than 7,600 ft thick at the coast (fig. 2) 

(Chowdhury and Turco, 2006). The sediments composing 

the Gulf Coast aquifer system were deposited by fluvialdeltaic processes and subsequently were eroded and 

redeposited (reworked) by worldwide episodic changes in 

sea level (eustasy) that occurred as a result of oscillations 

between glacial and interglacial climate conditions (Lambeck 

and others, 2002). The Gulf Coast aquifer system consists 

of hydrogeologic units that dip and thicken from northwest 

to southeast (fig. 2); the aquifers thus crop out in bands 

inland from and approximately parallel to the coast and 

become progressively more deeply buried and confined 

toward the coast (Kasmarek, 2013, figs. 4–7). The Burkeville 

confining unit is stratigraphically positioned between 

the Evangeline and Jasper aquifers (figs. 2–5), thereby 

restricting groundwater flow between the Evangeline and 

Jasper aquifers. There is no confining unit between the 

Chicot and Evangeline aquifers; therefore, the aquifers are 

hydraulically connected, which allows groundwater flow 

between the aquifers (figs. 2–4). Because of this hydraulic 

connection, water-level changes that occur in one aquifer 

can affect water levels in the adjoining aquifer (Kasmarek 

and Robinson, 2004). Supporting evidence of the interaction 

of groundwater flow between the Chicot and Evangeline 

aquifers is demonstrated by comparing the two long-term 

(1977–2016) water-level-change maps (Kasmarek and others, 

2016, sheets 5 and 10), which indicate that the areas where 

water levels have risen or declined are approximately spatially 

coincident. Hydraulic properties of the Chicot aquifer do 

not differ appreciably from the hydrogeologically similar 

Evangeline aquifer but can be differentiated on the basis of 

hydraulic conductivity (Carr and others, 1985, p. 10). From 

aquifer-test data, Meyer and Carr (1979) estimated that the 

transmissivity of the Chicot aquifer ranges from 3,000 to 

25,000 feet squared per day (ft2/d) and that the transmissivity 

of the Evangeline aquifer ranges from 3,000 to 15,000 ft2

/d. 

The Chicot aquifer outcrops and extends inland from the 

Gulf of Mexico coast and terminates at the northernmost 

updip limit of the aquifer. Proceeding updip and inland of 

the Chicot aquifer, the older hydrogeologic units of the 

Evangeline aquifer, the Burkeville confining unit, the Jasper 

aquifer, and the Catahoula confining system sequentially 

outcrop (fig. 1). In the outcrop and updip areas of the 

Jasper aquifer, the aquifer can be differentiated from the 

Evangeline aquifer on the basis of the depths to water below 

land-surface datum (blsd), which are shallower (closer to 

land surface) in the Jasper aquifer compared to those in the 

Evangeline aquifer. Additionally, in the downdip parts of the 

aquifer system, the Jasper aquifer can be differentiated from 

the Evangeline aquifer on the basis of stratigraphic position 

relative to the elevation of the Burkeville confining unit 

(figs. 2–4).
Jasper outcrop Catahoula confining system outcrop Tertiary outcrop Quaternary outcrop

Evangeline

 outcrop

Burkevilleconfining unit outcrop

Chicot aquifer outcrop

A

A'

10

1

2

3 4 5

6

7

8 9

11

WALLER COUNTY

GRIMES COUNTY

GALVESTON COUNTY

HARRIS COUNTY

MONTGOMERY COUNTY

HUMBLE

No. 1 Sealy

EXETER

No. 1 Bradley

KURDICK

No. 1 Stoneham

LONE STAR

No. 1 Goforth

SUPERIOR

No. B-1 McWhorter

NEWMAN & GEOTEK

No. 1 Ziegenhain

SPARTA

No. 1 Suttles et al.

TENNESSEE GAS

No. 1 Martin Unit

HUGHES

No. 1 Goar Est.

PHILLIPS

No. 5 Guaranty

WELL NUMBERS ON LOCATION MAP

A 

NORTHWEST 

MONTGOMERY

COUNTY +400 GRIMES COUNTY HARRIS COUNTY GALVESTON COUNTY

-400

-800

-1,200

-1,600

-2,000

-4,400

-4,800

-4,000

-3,600

-3,200

-2,800

-2,400

-5,200

-7,600

-7,200

-6,800

-6,400

-6,000

-5,600

NAVD 88

FEET 

1 2 3 4 5 6 7 8 9 10 

NAVD 88, North American Vertical Datum of 1988VERTICAL SCALE GREATLY EXAGGERATED

0 4 8 12 16 MILES

0 4 8 12 16 KILOMETERS

Anahuac

Formation

Formation

Frio

Catahoula

Sandstone

Base of 

Catahoula 

Sandstone 

Catahoula 

confining 

system

Jasper

aquifer

Base of 

Fleming 

Formation

Chicot aquifer

Evangeline aquifer

Burkeville

confining

unit

Approximate land surface

(upper part of Catahoula confining system)

(Holocene- and Pleistocene-age sediment

(Pliocene- and Miocene-age sediments)

(Miocene-age sedim

(Miocene-age sedim

(Miocene-age sediments)

Undifferentiated pre-Miocene-age deposits

Figure 2. Hydrogeologic section A–A ́ of the Gulf Coast aquifer system in Grimes, Montgomery, Harris, and Galveston Counties, Texas (modified from 
Introduction 7

+200

-200

-400

-600

-800

-1,000

-1,200

-1,400

-1,600

-1,800

-2,000

-2,200

-2,400

-2,600

-2,800

-3,000

JY–65–10–711 

JY–65–18–402

JY–65–27–211

JY–65–35–305

JY–65–36–401

JY–65–44–103

Approximate land surface

WELL NUMBERS ON LOCATION MAP

2 3 4 5

B B′ 

NGVD 29

+200

-200

-400

-600

-800

-1,000

-1,200

-1,400

-1,600

-1,800

-2,000

-2,200

-2,400

-2,600

-2,800

-3,000

NGVD 29

Evangeline aquifer

 Chicot aquifer

Burkeville confining unit

Jasper aquifer

NORTHWEST SOUTHEAST

FEET FEET

Chicot aquifer outcrop

1 6

FORT BEND

COUNTY

1

2

3

4 5

6

B

B′

(Holocene- and Pleistocene-age sediments)

(Pliocene- and Miocene-age sediments)

(Miocene-age

sediments)

(Miocene-age sediments)

NGVD 29, National Geodetic Vertical Datum of 1929

VERTICAL SCALE GREATLY EXAGGERATED

0 4 8 10 MILES

2 4 6 8 10 KILOMETERS

2 6

0

Figure 3. Hydrogeologic section B–B ́ of the Gulf Coast aquifer system in Fort Bend County, Texas (modified from Wesselman, 1972, 

fig. 30).
8 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

0 4 8 10 MILES

84 62 10 KILOMETERS

2 6

0

TS–60–26–801

TS–60–35–203

TS–60–36–403

TS–60–44–101

TS–60–44–507

TS–60–44–902

TS–60–53–105

TS–60–53–810

TS–60–53–803

LJ–60–61–602 

Jackson

Group

Burkeville confining unit 

Chicot

Approximate

land surface MONTGOMERY COUNTY HARRIS

NORTHWEST WELL NUMBERS ON LOCATION MAP SOUTHEAST

1 2 3 4 5 6 7 8 9 10

C C′

+400

NGVD 29

 -400

 -800

 -1,200

 -1,600

 -2,000

 -2,400

 -2,800

 -3,200

 -3,600

 -4,000

 -4,400

FEET

+400

NGVD 29

 -400

 -800

 -1,200

 -1,600

 -2,000

 -2,400

 -2,800

 -3,200

 -3,600

 -4,000

 -4,400

FEET

Undifferentiated pre-Miocene-age deposits

Evangeline aquifer

Jasper aquifer

MONTGOMERY

COUNTY

HARRIS

COUNTY

1

2

3

4

5

6

7

8

9

10

C

C′

NGVD 29, National Geodetic Vertical Datum of 1929

VERTICAL SCALE GREATLY EXAGGERATED

aquifer

Chicot aquifer outcrop

COUNTY

Evangeline aquifer outcrop

Jasper aquifer outcrop

Burkeville confining

unit outcrop

Catahoula Sandstone (upper part of Catahoula confining system)

(Miocene-age sediments)

(Pliocene- and Miocene-age sediments)

(Holocene- and Pleistocene-age sediments)

(Miocene-age sediments)

(Miocene-age sediments)

Figure 4. Hydrogeologic section C–C ́ of the Gulf Coast aquifer system in Montgomery and Harris Counties, Texas (modified from 

Popkin, 1971, fig. 29).
Introduction 9

 2Frio Formation

2

Upper part of Catahoula

Sandstone

2

Anahuac 

Formation

1

Catahoula

Sandstone

 Burkeville 

confining unit

1

Located in the outcrop.

2

Located in the subcrop.

Erathem System

Geologic units

Hydrogeologic 

units

Houston

Citronelle

Fleming

Vicks-

 burg

Group

Alluvium

Beaumont

 Clay

Montgomery

Formation

Bentley

Formation

Willis Sand

Goliad Sand

Fleming Formation

 Lagarto Clay

 Lissie

Formation

Oakville Sandstone

Stratigraphic units

Aquifers and 

confining 

units

 Years

 before

present

(Baker, 1979)

Chicot

aquifer

Evangeline

aquifer

Quaternary

Tertiary

Cenozoic

Jasper 

aquifer

Catahoula 

confining 

system

11,000

1.8 million

5.0 million

23 million

Holocene

Pliocene

Miocene

Pleistocene

Series

Pre-Miocene-age sediments

Figure 5. Geologic and hydrogeologic units of the Gulf Coast aquifer system in the Houston-Galveston region study area, Texas

(modified from Sellards and others, 1932; Baker, 1979; Meyer and Carr, 1979).
10 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

The hydrogeologic cross section A–A ́ (fig. 2) extends 

through the Houston-Galveston region from northwestern 

Grimes County southeastward through Montgomery and 

Harris Counties before terminating at the coast in Galveston 

County; the Chicot, Evangeline, and Jasper aquifers thicken 

and dip toward the coast from their updip (outcrop) limits. 

Comparisons of cross sections A–A ́ (fig. 2) and C–C ́ (fig. 4) 

indicate that the thicknesses of the three aquifers similarly 

increase downdip towards the coast. In Montgomery and 

Grimes Counties, the saturated thickness of the sediments 

composing the Chicot aquifer (figs. 2 and 4) is effectively 

insufficient for most groundwater withdrawals except for 

low-volume domestic withdrawals. The hydrogeologic 

cross section C–C ́ (fig. 4) extends through Montgomery 

County into extreme northern Harris County and similarly 

indicates that sediment thickness of the aquifers progressively 

decreases towards the northwest updip limit. Compared to 

the appreciable downdip changes in saturated thicknesses of 

the Chicot and Evangeline aquifers depicted in hydrogeologic 

cross sections A–A ́ and C–C ́, the saturated thicknesses of 

the Chicot and Evangeline aquifers moving downdip along 

hydrogeologic cross section B–B ́ are relatively constant (only 

a small part of the Jasper aquifer is present in hydrogeologic 

cross section B–B ́) (fig. 3). 

The water quality of the Chicot, Evangeline, and 

Jasper aquifers in the Houston-Galveston region varies 

spatially and with depth. For the most part, the groundwater 

is classified as fresh (less than 1,000 milligrams per liter 

[mg/L] dissolved-solids concentration [Freeze and Cherry, 

1979]). Concentrations of dissolved solids range from less 

than 500 mg/L in the updip parts of the aquifers to more 

than 10,000 mg/L in the downdip and more deeply buried, 

confined parts of the aquifers near the coast (Baker, 1979; 

Peter and others, 2011). Precipitation falling on the land 

surface overlying these aquifers returns to the atmosphere 

as evapotranspiration, discharges to streams, or infiltrates 

as groundwater recharge to the unconfined updip sediments 

composing the aquifers. The infiltrating water moves 

downgradient, reaching the intermediate and deep zones of 

the aquifers southeastward of the outcrop areas; regionally, the 

recharged water also moves downgradient toward the coast 

into the intermediate and deep zones of the aquifers, where 

it can be withdrawn and discharged by wells or is naturally 

discharged by diffuse upward leakage in topographically low 

areas near the coast (Kasmarek and Robinson, 2004). Water 

in the coastal, deep zones of the aquifers is denser, and this 

higher density water causes the fresher, lower density water 

that has not been captured and withdrawn by wells to be 

redirected as diffuse upward leakage to shallow zones of the 

confined downdip areas of the aquifer system. Remaining 

water not withdrawn by wells ultimately discharges along 

the coast, providing inflows to the brackish (dissolved-solids 

concentrations of 1,000–10,000 mg/L [Freeze and Cherry, 

1979]) waters of the coastal bays and estuaries (Kasmarek and 

Robinson, 2004).

Subsidence and Compaction Processes

Subsidence can occur as a result of potentiometric surface 

declines in unconsolidated confined aquifers (Galloway 

and others, 1999). Potentiometric surface declines cause a 

decrease in hydraulic pressure (depressuring) that creates a 

load on the skeletal matrix of the sediments in the aquifer and 

adjacent confining units (fig. 6). Because sand layers are more 

transmissive and less compressible than are fine-grained silt 

and clay layers, sand layers depressure more rapidly compared 

to silt and clay layers. In addition, when groundwater 

withdrawals are decreased, pressure equilibrium is 

reestablished more rapidly in the sand layers compared to the 

silt and clay layers, and the amount of compaction of the sand 

layers is usually minor compared to the amount of compaction 

of the silt and clay layers (Trahan, 1982; Galloway and others, 

1999). The silt and clay layers are often interbedded within 

the sand layers, and when depressuring occurs, the silt and 

clay layers dewater more slowly compared to the sand layers. 

The compressibility of the silt and clay layers is dependent on 

the thickness and hydraulic characteristics of the silt and clay 

layers and the vertical stress of the saturated and unsaturated 

sediment overburden. Slow drainage of the silt and clay layers 

continues to occur until the residual excess pore pressure in 

the silt and clay layers equilibrates with the pore pressure of 

the adjacent sand layers (Kasmarek, 2013). As dewatering 

progresses, compaction of the silt and clay layers continues 

until hydraulic pressure equilibrium is attained. A similar 

loading process occurs in the sand layers; however, the major 

difference is that the individual silt and clay grains spatially 

rearrange as depressuring and dewatering progress, finally 

becoming perpendicular to the applied vertical overburden 

load (Galloway and others, 1999). Essentially, the water 

stored in the silt and clay layers prior to depressuring provides 

interstitial pore-space support to the skeletal matrix of the silt 

and clay grains. As water levels continue to decline, the silt 

and clay layers continue to dewater, depressure, and compact. 

Additionally, compaction of the silt and clay layers reduces 

the porosity and groundwater-storage capacity of the silt and 

clay layers (fig. 6). Because most compaction of subsurface 

sediments is inelastic, with about 90 percent of the compaction 

considered permanent, only a small amount of rebound of 

the land-surface elevation can occur (Gabrysch and Bonnet, 

1975). Although the compaction of one thin silt and clay layer 

generally will not cause a measureable decrease in the landsurface elevation, when numerous stratigraphic sequences of 

sand layers and silt and clay layers (characteristic of the Gulf 

Coast aquifer system) depressure and compact, a measureable 

amount of subsidence often occurs (Gabrysch and Bonnet, 

1975).
Data-Collection and Analysis Methods 11

Granular silt and clay skeletal

matrix defining fluid-filled

interstitial pore spaces that

store groundwater

Rearranged and compacted

granular silt and clay skeletal

matrix with reduced porosity and

groundwater storage capacity 

Permanent decrease in land-surface

elevation caused by irreversible 

inelastic deformation accompanied

by an increase in the effective stress

on the aquifer 

After long-term and sustained

groundwater withdrawals, the resulting 

compaction of aquifer sediments is 

concentrated in the fine-grained silt 

and clay layers

When long-term withdrawals

lower groundwater levels and 

raise pressure on the clay and 

silt layers beyond a threshold 

amount, the silt and clay layers 

compact, and the land-surface 

elevation decreases permanently

Depth to

water

below 

land

surface

Hydrograph of long-term waterlevel decline modulated by seasonal 

cycles of increased and decreased 

groundwater withdrawals

Silt and clay

Gravel and sand

 Original landsurface elevation Resultant landsurface elevation

Years

Gravel and sand

Silt and clay

Original

predevelopment 

aquifer sediment 

thickness prior 

to groundwater 

withdrawals 

Recoverable land-surface elevation caused by 

reversible elastic deformation (cyclic shrinking 

and swelling of fine-grained surficial sediments) 

Magnified view

Land surface

Resultant potentiometric surface

Original predevelopment 

potentiometric surface

Figure 6. Mechanism of subsidence caused by potentiometric surface declines induced by groundwater withdrawals in an aquifer 

composed of gravel, sand, silt, and clay (modified from Galloway and others, 1999, p. 9).

Data-Collection and Analysis Methods

Water-level data were obtained from observation wells by 

measuring the depth to water blsd at each well. Measurements 

were made by USGS personnel by using a calibrated steel 

tape, airline, or electric water-level tape in accordance with 

methods described in Cunningham and Schalk (2011). 

Water-level data also were provided by industrial entities 

and powerplants within the study area that use water for 

hydrocarbon processing and electrical power generation, 

respectively. Most of the measured wells were being pumped 

at least once daily and some more frequently during the period 

of this study. Well pumps were inoperative for at least 1 hour 

before the water-level measurements were made in order 

to obtain a water-level measurement that approximates the 

static conditions within the aquifer. Antecedent withdrawal 

rates and pumping status of nearby wells were not always 

known, however, and in such instances could have affected the 

representativeness of the water-level data that were collected. 

To ensure that the water-level measurement recorded was 

accurate, at least two water-level-altitude measurements were 

made at each well while the well was not being pumped. 

To represent the annual water-level altitudes of the Chicot, 

Evangeline, and Jasper aquifers, water-level altitudes are 

usually measured from December through March; the 2017 

water-level altitudes discussed in this report were measured 

from December 2016 through March 2017. Water-level 

altitudes in the Houston-Galveston region are usually higher 

during December through March compared to the rest of 

the year because groundwater withdrawals during these 

months generally are at an annual minimum; during these 

winter months, the temperatures are cooler, and less water 

is used for agricultural and residential (lawn) irrigation 

purposes compared to the rest of the year. Conversely, 

water-level altitudes in the aquifers decline during the warm 

summer and early fall months because there is usually less 

precipitation and groundwater withdrawals are much larger 

compared to other months of the year. After the water-levelmeasurement data were collected during December 2016 

through March 2017, they were thoroughly evaluated and 

incorporated into a geographic information system (GIS) as 

point-data layers and subsequently used for the construction 

of water-level-altitude and water-level-change maps 

(Kasmarek and Ramage, 2017). 
12 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

Determination of Water-Level Altitudes

The annual (2017) regional-scale depictions of waterlevel altitudes presented in this report were derived from 

water-level-measurement data collected during December 

2016 through March 2017 throughout the 11-county study 

area. The water levels in the aquifers are constantly changing 

in response to changes in hydrologic conditions, groundwater 

withdrawal rates, and precipitation. Therefore, the depictions 

of water-level altitude represent aquifer conditions at the 

time the water-level data were collected. These water-levelaltitude data were calculated by subtracting the water-level 

measurement from the land-surface elevation value at 

each well referenced to NAVD 88 (National Oceanic and 

Atmospheric Administration, 2008). To determine land-surface 

elevations, a corresponding land-surface-datum value for 

each well was obtained by using USGS National Geospatial 

Program 3D Elevation Program (3DEP) values referenced to 

NAVD 88 (U.S. Geological Survey, 2017b). The height above 

land-surface elevation of the water-level measuring point of 

each well was measured by using an engineering ruler. The 

accuracy of the land-surface-elevation data has gradually 

improved over time, and the most accurate land-surface data 

available were used by the USGS for each historical annual 

depiction of water-level altitudes in the study area. Prior to 

2016, water-level altitudes published in this annual series of 

USGS reports were referenced to either the National Geodetic 

Vertical Datum of 1929 or NAVD 88.

The 2017 water-level altitudes measured in wells 

completed in the Chicot, Evangeline, and Jasper aquifers 

are depicted on contour maps with 50-ft contour intervals. 

The approximate water-level-altitude contours are regionalscale depictions of the water levels in wells in the Chicot, 

Evangeline, and Jasper aquifers, and the areal extents and 

locations of these contours represent the combined effects of 

total groundwater withdrawals from all groundwater wells 

screened in the Gulf Coast aquifer system.

Quality Assurance

Protocols for the collection and review of waterlevel data were in accordance with the USGS Texas Water 

Science Center internal document “Quality Assurance and 

Data Management Plan for Groundwater Activities” dated 

January 2017 (section 5.0, “Data collection,” and section 6.0, 

“Data review and processing” [Christopher L. Braun, U.S. 

Geological Survey, written commun., 2017]). All collected 

data were archived in the USGS National Water Information 

System (NWIS) (U.S. Geological Survey, 2017a).

Depicting Changes in Water-Level Altitudes

Maps depicting changes in water-level altitudes in the 

Chicot, Evangeline, and Jasper aquifers were constructed for 

the long-term (1977–2017 [Chicot and Evangeline aquifers] 

and 2000–17 [Jasper aquifer]) periods. Water-level changes 

were computed as the difference between water-level altitudes 

at each point (well) for which a water-level measurement was 

made in 1977 or 2000 and in 2017. For wells measured in 

2017 that had no corresponding measurement in 1977 or 2000, 

a GIS raster (gridded surface) (Worboys, 1995) was created 

from published 1977 (Gabrysch, 1979) or 2000 (Kasmarek 

and Houston, 2007) water-level-altitude contours. The maps 

were constructed by contouring the set of mapped point 

values computed either as the difference in water-level altitude 

at each point (well) for which a water-level measurement 

was made in 2017 and in 1977 or 2000 or as the difference 

in water-level altitude at that point in 2017 and the waterlevel altitude on a gridded surface of the 1977 (Gabrysch, 

1979) or 2000 (Kasmarek and Houston, 2007) water-levelaltitude maps. Gridded-surface values (rather than actual 

measured values) for the historical year were used to compute 

differences (mapped point values) because many of the wells 

measured in 1977 or 2000 have been destroyed or were not 

measured in 2017. For the subset of wells measured both in 

2017 and in 1977 or 2000, the mapped point values used were 

the differences in water-level-altitude values between 2017 

and 1977 or 2000 rather than the differences between the 2017 

water-level-altitude values and the gridded-surface values 

from 1977 or 2000. The datasets of water-level-change values 

(difference between 2017 and 1977 or 2000 water-levelaltitude values) are available in Kasmarek and Ramage (2017).

Borehole Extensometers

To construct an extensometer (example shown in fig. 7), 

a borehole is first drilled to a predetermined depth, generally 

below the depth of expected water-level decline. A steel outer 

casing with one or more slip joints and a screened interval is 

installed in the previously drilled borehole. The slip joint(s) 

helps to prevent crumpling and collapse of the well casing as 

compaction of subsurface sediments occurs, and the screened 

interval allows groundwater to enter the outer casing and 

inner casing of the piezometer, a type of small-diameter well 

with a screened interval that is used to measure the depth 

to water blsd. A substantial cement plug is installed and set 

at the base of the extensometer, and after the cement plug 

hardens, the smaller diameter inner pipe (often referred to 

as the “extensometer pipe”) is inserted down hole inside the 

outer casing and positioned to rest on the upper surface of the 

cement plug at depth. This rigid inner pipe, therefore, extends 

vertically from the top of the cement plug to slightly above 

land surface, thus providing a fixed reference elevation above 

land surface for measuring changes in land-surface elevation. 

At land surface, a concrete slab is poured and connected to an 

array of vertical concrete piers extending down into the water 

table. The concrete piers connect the slab to the underlying 

unconsolidated sediments penetrated by the borehole; this 

construction design helps to eliminate the continuous shrink 

and swell of the surficial clayey sediments associated with 

soil-moisture changes. A metal gage house (not depicted 
Data-Collection and Analysis Methods 13

0

 200

 400

 600

 800

 1,000

 1,200

 2,400

 2,600

 2,800

 3,000

Depth below land surface, in feet

Note: All depths are referenced to land-surface elevation

 2,825 ft

 2,869 ft

 2,831 ft

Cement plug

Inner-pipe (extensometer pipe)

diameter: 2.375 in., extending 

from 1.5 ft above land surface 

into plug at 2,831 ft

Outer-casing diameter: 4.5 in., 

extending from 1 ft above land

surface to 2,825 ft below land

surface

Neat cement grout

Land surface

Concrete-slab size:

6 ft × 6 ft 10 in. × 10 in.

Steel table

Shaft encoder and

analog recorder

Note: Recorder, table, 

slab, piers, casing, 

screened interval, slipjoint lengths, and cement

plug are not drawn to 

scale

Unconsolidated and confined 

aquifer sediments

Piers composed of concrete

and steel reinforcing bars 

Screened interval: 2,707–2,717 ft

Slip-joint interval: 252–260 ft

Slip-joint interval: 511–519 ft

Slip-joint interval: 1,000–1,008 ft

Counter weight

. Calibrated steel tape

Boreholeextensometer slab

Figure 7. Cross-sectional perspective of the borehole extensometer/piezometer (LJ–65–23–322) located at Pasadena, Texas (ft, foot; 

in., inch).
14 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

in fig. 7) is constructed on the concrete slab, and a shaft 

encoder and analog recorder are mounted to a steel table 

that is attached to the concrete slab. A calibrated steel tape 

connects the recorder to the top of the inner pipe; because 

the steel table is anchored to the concrete slab, changes 

in land-surface elevation can be accurately measured and 

recorded. These recorded values through time represent the 

cumulative compaction that has occurred at the extensometer 

site. Because the extensometer functions as a piezometer and 

an extensometer, the cause-and-effect relation between the 

changes in water level in the aquifer and the changes in landsurface elevation can be established. Detailed information 

on the scientific theory, construction, and operation of 

extensometers is presented in Gabrysch (1984).

For this report, extensometer data of the cumulative 

compaction in the Chicot and Evangeline aquifers were 

collected from and evaluated for 13 extensometers at 11 sites 

in Harris and Galveston Counties (fig. 8) and are available 

in Ramage (2017). The extensometer data recorded at these 

11 sites are used to quantify the rate of compaction in the 

Chicot and Evangeline aquifers on an ongoing basis, thereby 

providing water-resource managers a tool for evaluating the 

effects on subsidence rates caused by changes in the volume 

of groundwater withdrawn from the Chicot and Evangeline 

aquifers. 

To quantify the rates of compaction in the aquifers, a 

network of extensometers was installed beginning in 1973 

at selected sites throughout Harris and Galveston Counties. 

Five extensometers were installed (four in Harris County and 

one in Galveston County) and began recording cumulative 

compaction data in July 1973: LJ–65–22–622 (East End), 

LJ–65–16–930 (Baytown C–1 [shallow]), LJ–65–16–931 

(Baytown C–2 [deep]), and LJ–65–32–625 (Seabrook) in 

Harris County and KH–64–33–920 (Texas City-Moses Lake) 

in Galveston County. An extensometer initially installed 

in 1962 in Harris County (LJ–65–32–401 [Johnson Space 

Center]) was also included in the network. Since July 1973, 

routine measurements of compaction at the Johnson Space 

Center extensometer have been recorded and collected and are 

included in this report. Additional extensometers were added 

to the network during 1974–76 in Harris County: LJ–65–12–

726 (Addicks) in 1974, LJ–65–23–322 (Pasadena) in 1975, 

and LJ–65–32–424 (Clear Lake [shallow]) and LJ–65–32–428 

(Clear Lake [deep]) in 1976. The most recent extensometers 

added to the network were installed in Harris County in 

1980: LJ–65–07–909 (Lake Houston), LJ–65–14–746 

(Northeast), and LJ–65–21–226 (Southwest). Since activation 

or installation between 1973 and 1980, cumulative compaction 

data have been continuously recorded and periodically 

collected about every 28 days at the 13 extensometers, thereby 

providing site-specific rates of compaction accurate to within 

0.001 ft. From late 1973 to late 1982, a noticeable amount 

of seasonal variation occurred at the two extensometers at 

the Baytown site (fig. 8). This variation was determined to 

be caused by surficial clayey sediments that expand (swell) 

during periods of precipitation and contract (shrink) during hot 

and dry periods, which is characteristic of the montmorillonitic 

clay within the aquifer sediments. Consequently, in 1982, to 

reduce the excessive recorded fluctuation of the land surface, 

both extensometers were modified by installing a system 

of more deeply penetrating vertical piers into the sediments 

at the depth of the water table. Compaction data collected 

at the Baytown site after 1982 indicate that these design 

modifications reduced these fluctuations and improved the 

accuracy of the data (Ramage, 2017).

Each extensometer has a 10- to 20-ft screened interval 

that is located above the cement plug, which allows water to 

flow into the center pipe and thus functions as a piezometer 

(fig. 7). A water-level measurement is made during each 

extensometer site visit. If the depth of the screened interval 

is positioned entirely within the Chicot aquifer or Evangeline 

aquifer, these water-level measurements are evaluated to 

determine if they are representative of water levels in the 

adjacent area and, when verified, are used in the creation of 

the water-level-altitude maps.

Water-Level Altitudes and Changes

During years when rainfall and temperature are near 

normal, total groundwater withdrawals in the study area 

typically do not change appreciably from the previous year; 

therefore, water-level altitudes in the aquifer system typically 

do not fluctuate appreciably from the previous year (Kasmarek 

and Houston, 2007; Kasmarek and others, 2011, 2016). During 

years of drought or abundant rainfall, however, water-level 

altitudes in the aquifer system can be appreciably different 

compared to the previous year because of changes in recharge 

and groundwater withdrawals (Kasmarek and Houston, 

2008; Johnson and others, 2011; Kasmarek and others, 2012, 

2013). The water-level altitudes in the Chicot, Evangeline, 

and Jasper aquifers depicted in this report for 2017 were 

measured following a year of abundant rainfall. The National 

Oceanic and Atmospheric Administration (2017) reported 

that 60.96 inches (in.) of precipitation fell in Houston during 

2016 compared to the average annual precipitation amount of 

49.77 in. for 1981–2010. The wetter-than-normal conditions 

were accompanied by warmer-than-normal temperatures; 

the average annual temperature in 2016 for Houston was 

1.6 degrees Fahrenheit above normal (1981–2010; National 

Oceanic and Atmospheric Administration, 2017). Because 

more groundwater might be withdrawn for irrigation purposes 

if the weather is warmer than normal during the irrigation 

season, the warmer-than-normal temperatures in 2016 might 

somewhat counteract the wetter-than-normal conditions in 

terms of groundwater withdrawals. Compared to 2016, water 

levels in 2017 increased in about 54, 48, and 80 percent of the 

wells screened in the Chicot, Evangeline, and Jasper aquifers, 

respectively. Water levels in 2017 decreased compared to 

2016 in about 27, 43, and 18 percent of the wells screened 

in the Chicot, Evangeline, and Jasper aquifers, respectively 

(Kasmarek and others, 2016; Kasmarek and Ramage, 2017). 
Water-Level Altitudes and Changes 15

FM 521

FM 787

FM 2004

90

105

45

249

59

10

99

90

548

321

FM 1960

FM 1764

FM 35

150 FM 1375

225

87

168

30

90

19

156

6

State Loop 336

36

105

90 59

290

59

45

10

610

45

Galveston Rd

Grand Pky

36

N Sam Houston Pky W

S Sam Houston Pky E

E North Belt

Addicks Satsuma Rd

S Belt

146

288

45

190

75

30

90

10

610

35

35

332

6

59

3

146

105

146

61

65

1488

1774

EXPLANATION

Location of borehole-extensometer site

Harris-Galveston Subsidence District

(HGSD) regulatory area 1

HGSD regulatory area 2

HGSD regulatory area 3 

Fort Bend Subsidence District

(FBSD) regulatory area A

Lone Star Groundwater Conservation

District (LSGCD) regulatory area

Brazoria County Groundwater Conservation

District (BCGCD) regulatory area 

FBSD regulatory area B 

0 8 16 24 MILES

0 8 16 24 KILOMETERS

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

Universal Transverse Mercator projection, Zone 15

North American Datum of 1983

Tomball

The Woodlands

Manvel

Hitchcock

La Marque

Liberty

Jersey 

Village

Prairie 

View

Hempstead

Magnolia

Fulshear

Shepherd

Cleveland

Plum 

Grove

Montgomery Willis

Huntsville

Navasota

Waller

Pattison

Conroe

Spring

Houston

Humble

Aldine

Katy

Channelview

Baytown Galena 

Park

Mont 

Belvieu

Pasadena

Deerpark

Dayton

Santa Fe

Bellaire

West University

Place

Sugar

Land

Missouri

City

Richmond

Pearland

Rosenberg Friendswood

League City Texas City Alvin

Galveston

Angleton

Clute Lake

Jackson

Freeport

River

Brazos

River

San

Bernard

River

Brazos River

Trinity

River

West Fork

San

River

West Fork

San

Jacinto

River

Cedar

Bayou

Buffalo

Bayou

Clear

Lake

Creek

Lake Creek

Caney

Creek

Spring

Oyster

Creek

Brazos

Sheldon

Reservoir

Trinity Bay

Lake

Houston

Lake Conroe

Lake

Livingston

Galveston

Bay

East Bay

West Bay

GULF OF MEXICO

Jacinto

Creek

Creek

AUSTIN COUNTY

FORT BEND

COUNTY

WALKER

COUNTY

MONTGOMERY

COUNTY

SAN JACINTO COUNTY

COUNTY

WALLER 

BRAZORIA 

COUNTY

GALVESTON 

COUNTY

CHAMBERS COUNTY

LIBERTY COUNTY

GRIMES COUNTY

AZOS

COUNTY

WHARTON COUNTY

HARRIS

COUNTY

95°45'

95°45'

95°30'

95°30' 95°15'

95°

95°

30°30'

30°

30°

30°15'

30°15'

29°30'

29°45'

29°45'

29°15'

96°

96°

94°45'

94°45'

94°30'

94°30'

30°30'

29°15'

30°45'

29° 29°

30°45'

29°30'

95°15'

ADDICKS

LJ–65–12–726 NORTHEAST

LJ–65–14–746

SOUTHWEST

LJ–65–21–226

EAST END

LJ–65–22–622

PASADENA

LJ–65–23–322

LAKE HOUSTON

LJ–65–07–909

BAYTOWN

LJ–65–16–930 (C–1 [shallow])

LJ–65–16–931 (C–2 [deep])

SEABROOK

LJ–65–32–625

JOHNSON SPACE

CENTER

LJ–65–32–401

CLEAR LAKE

LJ–65–32–424 (shallow)

LJ–65–32–428 (deep)

TEXAS CITYMOSES LAKE

KH–64–33–920

Study area

TEXAS

LSGCD

FBSD

BCGCD

HGSD

HGSD 

HGSD 

FBSD

Figure 8. Locations of borehole-extensometer sites and respective areas of jurisdiction for each groundwater regulatory district, 

Houston-Galveston region, Texas, 2016.
16 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

Locations of wells used to construct the 2017 waterlevel-altitude maps for the Chicot, Evangeline, and Jasper 

aquifers are presented in Kasmarek and Ramage (2017). The 

water-level altitudes in 2017 and 2016 (Kasmarek and others, 

2016) were generally similar. The Chicot, Evangeline, and 

Jasper aquifer maps in this report depict approximate waterlevel altitudes for 2017 and water-level-altitude changes for 

1977–2017 in the Chicot and Evangeline aquifers and for 

2000–17 in the Jasper aquifer.

Chicot Aquifer

Water-level-measurement data from 164 wells were used 

to depict the approximate 2017 water-level-altitude contours 

for the Chicot aquifer (fig. 9) (all of the water-level contours 

in this report are considered approximate). In 2017, waterlevel-altitude contours for the Chicot aquifer ranged from 

200 ft below NAVD 88 (hereinafter referred to as “datum”) in 

two localized areas in southwestern and northwestern Harris 

County to 200 ft above datum in west-central Montgomery 

County.

The largest water-level-altitude decline (120 ft) depicted 

by the 1977–2017 water-level-change contours for the Chicot 

aquifer was in northwestern Harris County (fig. 10). A broad 

area where water-level altitudes declined in the Chicot aquifer 

extends from northwestern, north-central, and southwestern 

Harris County across parts of north-central, eastern, and southcentral Fort Bend County into southeastern Waller County. 

In addition to the broad area of decline, water-level altitudes 

also declined from Fort Bend County into northwestern 

Brazoria County (fig. 10). Adjacent to the areas where water 

levels declined was a broad area where water levels rose in 

central, eastern, and southeastern Harris County, most of 

Galveston County, eastern and northernmost Brazoria County, 

and northeastern Fort Bend County. There were also small 

isolated areas in northwestern and southwestern Fort Bend 

County where water-level altitudes rose 20 ft (fig. 10). The 

largest rise (200 ft) in water-level altitudes in the Chicot 

aquifer from 1977 to 2017 was in southeastern Harris County 

(fig. 10).

Evangeline Aquifer

Water-level-measurement data from 305 wells were used 

to depict the approximate 2017 water-level-altitude contours 

for the Evangeline aquifer (fig. 11). In 2017, the waterlevel-altitude contours for the Evangeline aquifer indicated 

two areas where the water-level altitudes were 250 ft below 

datum—one of these areas extended from south-central 

Montgomery County into north-central Harris County, and the 

other was in western Harris County. Water-level altitudes in 

the Evangeline aquifer ranged from 50 to 200 ft below datum 

throughout most of Harris County in 2017. In Montgomery 

County, water-level altitudes in the Evangeline aquifer in 2017 

ranged from the aforementioned area where they were 250 ft 

below datum to an area where they were 200 ft above datum 

in the northwestern part of the county. The water-level-altitude 

contour of 200 ft above datum extended from southern Grimes 

County, through a small part of northern Waller County, into 

northwestern Montgomery County (fig. 11).

The 1977–2017 water-level-change contours for the 

Evangeline aquifer (fig. 12) depict a broad area where waterlevel altitudes declined in north-central Harris and southcentral Montgomery Counties, extending through northcentral, northwestern, and southwestern Harris County into 

western Liberty, southeastern and northeastern Waller, and 

northeastern and east-central Fort Bend Counties (fig. 12). 

The largest water-level-altitude decline (280 ft) was in northcentral Harris and south-central Montgomery Counties. Waterlevel altitudes rose in a broad area from central, east-central, 

and southern Harris County extending into the northernmost 

part of Brazoria County, the northernmost part of Galveston 

County, and the southwestern area of Liberty County. The 

largest rise in water-level altitudes in the Evangeline aquifer 

from 1977 to 2017 (240 ft) was in southeastern Harris County 

(fig. 12).

Jasper Aquifer

Water-level-measurement data from 102 wells were used 

to depict the approximate 2017 water-level-altitude contours 

for the Jasper aquifer (fig. 13). In 2017, water-level-altitude 

contours for the Jasper aquifer ranged from 200 ft below 

datum in three isolated areas of south-central Montgomery 

County (the westernmost of these areas extended slightly into 

north-central Harris County) to 250 ft above datum in extreme 

northwestern Montgomery County, northeastern Grimes 

County, and southwestern Walker County (fig. 13).

Whereas annual water-level-altitude data have been 

collected since 1977 from wells completed in the Chicot and 

Evangeline aquifers, annual water-level-altitude data have 

been collected since only 2000 from wells completed in the 

Jasper aquifer. The 2000–17 water-level-change contours 

for the Jasper aquifer (fig. 14) depict water-level declines in 

a broad area throughout most of Montgomery County and 

in parts of Waller, Grimes, and Harris Counties, with the 

largest decline (220 ft) in an isolated area in south-central 

Montgomery County.
Water-Level Altitudes and Changes 17

FM 521

FM 787

FM 2004

90

105

45

249

59

10

99

90

548

321

FM 1960

FM 1764

FM 35

150 FM 1375

225

87

168

30

90

19

156

6

State Loop 336

36

105

90 59

290

59

45

10

610

45

Galveston Rd

Grand Pky

36

N Sam Houston Pky W

S Sam Houston Pky E

E North Belt

Addicks Satsuma Rd

S Belt

146

288

45

190

75

30

90

10

610

35

35

332

6

59

3

146

105

146

61

65

1488

1774

EXPLANATION

Water-level contour—Shows altitude at which water

level would have stood in tightly cased well. Contour

interval 50 feet. Datum is North American Vertical Datum

of 1988

200

Updip limit of Chicot aquifer (University of Texas, 

Bureau of Economic Geology, 1968; Baker, 1979)

Note:

The annual regional depictions of water-level altitudes presented in 

this report are substantiated by water-level-measurement data 

collected from December 2016 through March 2017 throughout an 

11-county area encompassing about 11,000 square miles. 

Contour locations and orientations should be viewed in a 

regional context because the water-level surface of the 

aquifers is a dynamic surface, constantly changing 

because of the dense network of wells operating in the 

study area. Users should be aware that water-level 

changes may have occurred since the water levels 

were determined for this report. Inherent 

uncertainties exist in these data such as 

antecedent withdrawal rates and the pumping 

status of nearby wells. When evaluating these 

contoured depictions, users should exercise 

discretion and know the limitations of these 

data when drawing conclusions or making 

policy decisions. These data should not 

be used for engineering applications.

Boundary of study area

0 8 16 24 MILES

0 8 16 24 KILOMETERS

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

Universal Transverse Mercator projection, Zone 15

North American Datum of 1983

Tomball

The Woodlands

Manvel

Hitchcock

La Marque

Liberty

Jersey 

Village

Prairie 

View

Hempstead

Magnolia

Fulshear

Shepherd

Cleveland

Plum 

Grove

Montgomery Willis

Huntsville

Navasota

Waller

Pattison

Conroe

Spring

Houston

Humble

Aldine

Katy

Channelview

Baytown Galena 

Park

Mont 

Belvieu

Pasadena

Deerpark

Dayton

Santa Fe

Bellaire

West University

Place

Sugar

Land

Missouri

City

Richmond

Pearland

Rosenberg Friendswood

League City Texas City Alvin

Galveston

Angleton

Clute Lake

Jackson

Freeport

River

Brazos

River

San

Bernard

River

Brazos River

Trinity

River

West Fork

San

River

West Fork

San

Jacinto

River

Cedar

Bayou

Buffalo

Bayou

Clear

Lake

Creek

Lake Creek

Caney

Creek

Spring

Oyster

Creek

Brazos

Sheldon

Reservoir

Trinity Bay

Lake

Houston

Lake Conroe

Lake

Livingston

Galveston

Bay

East Bay

West Bay

GULF OF MEXICO

Jacinto

Creek

Creek

AUSTIN COUNTY

FORT BEND

COUNTY

WALKER

COUNTY

MONTGOMERY

COUNTY

SAN JACINTO COUNTY

COUNTY

WALLER 

BRAZORIA 

COUNTY

GALVESTON 

COUNTY

CHAMBERS COUNTY

LIBERTY COUNTY

GRIMES COUNTY

AZOS

COUNTY

WHARTON COUNTY

HARRIS

COUNTY

95°45'

95°45'

95°30'

95°30' 95°15'

95°

95°

30°30'

30°

30°

30°15'

30°15'

29°30'

29°45'

29°45'

29°15'

96°

96°

94°45'

94°45'

94°30'

94°30'

30°30'

29°15'

30°45'

29° 29°

30°45'

29°30'

95°15'

200

-150

-200

-150

150

100

-100

50

0

-50

-200

Study area

TEXAS

Figure 9. Approximate 2017 water-level altitudes and updip limit of the Chicot aquifer, Houston-Galveston region, Texas (water-levelmeasurement data collected during December 2016 through March 2017).
18 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

FM 521

FM 787

FM 2004

90

105

45

249

59

10

99

90

548

321

FM 1960

FM 1764

FM 35

150 FM 1375

225

87

168

30

90

19

156

6

State Loop 336

36

105

90 59

290

59

45

10

610

45

Galveston Rd

Grand Pky

36

N Sam Houston Pky W

S Sam Houston Pky E

E North Belt

Addicks Satsuma Rd

S Belt

146

288

45

190

75

30

90

10

610

35

35

332

6

59

3

146

105

146

61

65

1488

1774

EXPLANATION

20 Line of equal water-level rise—Interval 20 feet

-20 Line of equal water-level decline—Interval 20 feet

0 Line of zero water-level change

Note:

This change map was created by contouring the set of mapped 

point values computed as the difference in water-level altitude 

at each point (well) for which a water-level measurement was 

made in 2017 and the water-level altitude at that point on a 

gridded surface of the 1977 water-level-altitude map 

(Gabrysch, 1979, sheet 1). 

Gridded-surface values for 1977 (rather than actual 

measured values) were used to compute differences 

(mapped point values) because many of the wells 

measured in 1977 have been destroyed or were not 

measured in 2017. Conversely, some of the wells 

measured in 2017 either were not measured or 

were not in existence in 1977. Thus, using the 

gridded surface yielded more point values 

than would have been available by using 

only the subset of wells measured in both 

2017 and 1977. 

For the subset of wells measured in both 

2017 and 1977, the mapped point values 

used were the differences in 

water-level-altitude values between 

2017 and 1977 rather than the 

differences between 2017 

water-level-altitude values and 

1977 gridded-surface values. 

The area of water-level 

change shown is based on 

availability of water-level 

data from 1977.

Boundary of study area

Updip limit of Chicot aquifer (University of Texas, 

Bureau of Economic Geology, 1968; Baker, 1979)

0 8 16 24 MILES

0 8 16 24 KILOMETERS

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

Universal Transverse Mercator projection, Zone 15

North American Datum of 1983

Tomball

The Woodlands

Manvel

Hitchcock

La Marque

Liberty

Jersey 

Village

Prairie 

View

Hempstead

Magnolia

Fulshear

Shepherd

Cleveland

Plum 

Grove

Montgomery Willis

Huntsville

Navasota

Waller

Pattison

Conroe

Spring

Houston

Humble

Aldine

Katy

Channelview

Baytown Galena 

Park

Mont 

Belvieu

Pasadena

Deerpark

Dayton

Santa Fe

Bellaire

West University

Place

Sugar

Land

Missouri

City

Richmond

Pearland

Rosenberg Friendswood

League City Texas City Alvin

Galveston

Angleton

Clute Lake

Jackson

Freeport

River

Brazos

River

San

Bernard

River

Brazos River

Trinity

River

West Fork

San

River

West Fork

San

Jacinto

River

Cedar

Bayou

Buffalo

Bayou

Clear

Lake

Creek

Lake Creek

Caney

Creek

Spring

Oyster

Creek

Brazos

Sheldon

Reservoir

Trinity Bay

Lake

Houston

Lake Conroe

Lake

Livingston

Galveston

Bay

East Bay

West Bay

GULF OF MEXICO

Jacinto

Creek

Creek

AUSTIN COUNTY

FORT BEND

COUNTY

WALKER

COUNTY

MONTGOMERY

COUNTY

SAN JACINTO COUNTY

COUNTY

WALLER 

BRAZORIA 

COUNTY

GALVESTON 

COUNTY

CHAMBERS COUNTY

LIBERTY COUNTY

GRIMES COUNTY

AZOS

COUNTY

WHARTON COUNTY

HARRIS

COUNTY

95°45'

95°45'

95°30'

95°30' 95°15'

95°

95°

30°30'

30°

30°

30°15'

30°15'

29°30'

29°45'

29°45'

29°15'

96°

96°

94°45'

94°45'

94°30'

94°30'

30°30'

29°15'

30°45'

29° 29°

30°45'

29°30'

95°15'

0

0

0

100

20

60

200

20

180

160

140

120

20

40

100

60

80

-100

-120

-40

-80

-100

-60

-80

-60

-40 -20

Study area

TEXAS

Figure 10. Approximate 1977–2017 water-level changes in the Chicot aquifer, Houston-Galveston region, Texas.
Water-Level Altitudes and Changes 19

FM 521

FM 787

FM 2004

90

105

45

249

59

10

99

90

548

321

FM 1960

FM 1764

FM 35

150 FM 1375

225

87

168

30

90

19

156

6

State Loop 336

36

105

90 59

290

59

45

10

610

45

Galveston Rd

Grand Pky

36

N Sam Houston Pky W

S Sam Houston Pky E

E North Belt

Addicks Satsuma Rd

S Belt

146

288

45

190

75

30

90

10

610

35

35

332

6

59

3

146

105

146

61

65

1488

1774

Updip limit of Evangeline aquifer (Baker, 1979) 

Water-level contour—Shows altitude at which water

level would have stood in tightly cased well. Contour

interval 50 feet. Datum is North American Vertical Datum

of 1988

Boundary of study area

200

EXPLANATION

Note:

The annual regional depictions of water-level altitudes presented in 

this report are substantiated by water-level-measurement data 

collected from December 2016 through March 2017 throughout 

an 11-county area encompassing about 11,000 square miles. 

Contour locations and orientations should be viewed in a 

regional context because the water-level surface of the 

aquifers is a dynamic surface, constantly changing 

because of the dense network of wells operating in the 

study area. Users should be aware that water-level 

changes may have occurred since the water levels 

were determined for this report. Inherent 

uncertainties exist in these data such as 

antecedent withdrawal rates and the pumping 

status of nearby wells. When evaluating these 

contoured depictions, users should exercise 

discretion and know the limitations of these 

data when drawing conclusions or making 

policy decisions. These data should not 

be used for engineering applications.

0 8 16 24 MILES

0 8 16 24 KILOMETERS

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

Universal Transverse Mercator projection, Zone 15

North American Datum of 1983

Tomball

The Woodlands

Manvel

Hitchcock

La Marque

Liberty

Jersey 

Village

Prairie 

View

Hempstead

Magnolia

Fulshear

Shepherd

Cleveland

Plum 

Grove

Montgomery Willis

Huntsville

Navasota

Waller

Pattison

Conroe

Spring

Houston

Humble

Aldine

Katy

Channelview

Baytown Galena 

Park

Mont 

Belvieu

Pasadena

Deerpark

Dayton

Santa Fe

Bellaire

West University

Place

Sugar

Land

Missouri

City

Richmond

Pearland

Rosenberg Friendswood

League City Texas City Alvin

Galveston

Angleton

Clute Lake

Jackson

Freeport

River

Brazos

River

San

Bernard

River

Brazos River

Trinity

River

West Fork

San

River

West Fork

San

Jacinto

River

Cedar

Bayou

Buffalo

Bayou

Clear

Lake

Creek

Lake Creek

Caney

Creek

Spring

Oyster

Creek

Brazos

Sheldon

Reservoir

Trinity Bay

Lake

Houston

Lake Conroe

Lake

Livingston

Galveston

Bay

East Bay

West Bay

GULF OF MEXICO

Jacinto

Creek

Creek

AUSTIN COUNTY

FORT BEND

COUNTY

WALKER

COUNTY

MONTGOMERY

COUNTY

SAN JACINTO COUNTY

COUNTY

WALLER 

BRAZORIA 

COUNTY

GALVESTON 

COUNTY

CHAMBERS COUNTY

LIBERTY COUNTY

GRIMES COUNTY

AZOS

COUNTY

WHARTON COUNTY

HARRIS

COUNTY

95°45'

95°45'

95°30'

95°30' 95°15'

95°

95°

30°30'

30°

30°

30°15'

30°15'

29°30'

29°45'

29°45'

29°15'

96°

96°

94°45'

94°45'

94°30'

94°30'

30°30'

29°15'

30°45'

29° 29°

30°45'

29°30'

95°15'

-250

-200

-200

-150

-200

0

-150

0

-100

50

-150

-200

100

-100

-250

-50

-200

200

-150

-200

150

100

50

0

-50

Study area

TEXAS

Figure 11. Approximate 2017 water-level altitudes and updip limit of the Evangeline aquifer, Houston-Galveston region, Texas (waterlevel-measurement data collected during December 2016 through March 2017).
20 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

FM 521

FM 787

FM 2004

90

105

45

249

59

10

99

90

548

321

FM 1960

FM 1764

FM 35

150 FM 1375

225

87

168

30

90

19

156

6

State Loop 336

36

105

90 59

290

59

45

10

610

45

Galveston Rd

Grand Pky

36

N Sam Houston Pky W

S Sam Houston Pky E

E North Belt

Addicks Satsuma Rd

S Belt

146

288

45

190

75

30

90

10

610

35

35

332

6

59

3

146

105

146

61

65

1488

1774

Boundary of study area

Updip limit of Evangeline aquifer (Baker, 1979)

Note:

This change map was created by contouring the set of mapped 

point values computed as the difference in water-level altitude at 

each point (well) for which a water-level measurement was 

made in 2017 and the water-level altitude at that point on a 

gridded surface of the 1977 water-level-altitude map 

(Gabrysch, 1979, sheet 2). 

Gridded-surface values for 1977 (rather than actual 

measured values) were used to compute differences 

(mapped point values) because many of the wells 

measured in 1977 have been destroyed or were not 

measured in 2017. Conversely, some of the wells 

measured in 2017 either were not measured or 

were not in existence in 1977. Thus, using the 

gridded surface yielded more point values than 

would have been available by using only the 

subset of wells measured in both 2017 

and 1977. 

For the subset of wells measured in both 

2017 and 1977, the mapped point values 

used were the differences in 

water-level-altitude values between 

2017 and 1977 rather than the 

differences between 2017 

water-level-altitude values and 

1977 gridded-surface values. 

The area of water-level 

change shown is based on 

availability of water-level 

data from 1977.

EXPLANATION

40 Line of equal water-level rise—Interval 40 feet

-40 Line of equal water-level decline—Interval 40 feet

0 Line of zero water-level change

0 8 16 24 MILES

0 8 16 24 KILOMETERS

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

Universal Transverse Mercator projection, Zone 15

North American Datum of 1983

Tomball

The Woodlands

Manvel

Hitchcock

La Marque

Liberty

Jersey 

Village

Prairie 

View

Hempstead

Magnolia

Fulshear

Shepherd

Cleveland

Plum 

Grove

Montgomery Willis

Huntsville

Navasota

Waller

Pattison

Conroe

Spring

Houston

Humble

Aldine

Katy

Channelview

Baytown Galena 

Park

Mont 

Belvieu

Pasadena

Deerpark

Dayton

Santa Fe

Bellaire

West University

Place

Sugar

Land

Missouri

City

Richmond

Pearland

Rosenberg Friendswood

League City Texas City Alvin

Galveston

Angleton

Clute Lake

Jackson

Freeport

River

Brazos

River

San

Bernard

River

Brazos River

Trinity

River

West Fork

San

River

West Fork

San

Jacinto

River

Cedar

Bayou

Buffalo

Bayou

Clear

Lake

Creek

Lake Creek

Caney

Creek

Spring

Oyster

Creek

Brazos

Sheldon

Reservoir

Trinity Bay

Lake

Houston

Lake Conroe

Lake

Livingston

Galveston

Bay

East Bay

West Bay

GULF OF MEXICO

Jacinto

Creek

Creek

AUSTIN COUNTY

FORT BEND

COUNTY

WALKER

COUNTY

MONTGOMERY

COUNTY

SAN JACINTO COUNTY

COUNTY

WALLER 

BRAZORIA 

COUNTY

GALVESTON 

COUNTY

CHAMBERS COUNTY

LIBERTY COUNTY

GRIMES COUNTY

AZOS

COUNTY

WHARTON COUNTY

HARRIS

COUNTY

95°45'

95°45'

95°30'

95°30' 95°15'

95°

95°

30°30'

30°

30°

30°15'

30°15'

29°30'

29°45'

29°45'

29°15'

96°

96°

94°45'

94°45'

94°30'

94°30'

30°30'

29°15'

30°45'

29° 29°

30°45'

29°30'

95°15'

0

0

0

0

40

240

160

200

160

40

120

80

-160

-120

-80

-160 -120

-80

-280

-240

-80

-200

-160

-120

-40

-120

-40

-80

-40

Study area

TEXAS

Figure 12. Approximate 1977–2017 water-level changes in the Evangeline aquifer, Houston-Galveston region, Texas.
Water-Level Altitudes and Changes 21

FM 521

FM 787

FM 2004

90

105

45

249

59

10

99

90

548

321

FM 1960

FM 1764

FM 35

150 FM 1375

225

87

168

30

90

19

156

6

State Loop 336

36

105

90 59

290

59

45

10

610

45

Galveston Rd

Grand Pky

36

N Sam Houston Pky W

S Sam Houston Pky E

E North Belt

Addicks Satsuma Rd

S Belt

146

288

45

190

75

30

90

10

610

35

35

332

6

59

3

146

105

146

61

65

1488

1774

Updip limit of Jasper aquifer (University of Texas,

Bureau of Economic Geology, 1968, 1974; Baker, 1986)

Water-level contour—Shows altitude at which water

level would have stood in tightly cased well. Contour

interval 50 feet. Datum is North American Vertical Datum

of 1988

Boundary of study area

50

EXPLANATION

Note:

The annual regional depictions of water-level altitudes presented in 

this report are substantiated by water-level-measurement data 

collected from December 2016 through March 2017 throughout 

an 11-county area encompassing about 11,000 square miles. 

Contour locations and orientations should be viewed in a 

regional context because the water-level surface of the 

aquifers is a dynamic surface, constantly changing 

because of the dense network of wells operating in the 

study area. Users should be aware that water-level 

changes may have occurred since the water levels 

were determined for this report. Inherent 

uncertainties exist in these data such as 

antecedent withdrawal rates and the pumping 

status of nearby wells. When evaluating these 

contoured depictions, users should exercise 

discretion and know the limitations of these 

data when drawing conclusions or making 

policy decisions. These data should not 

be used for engineering applications.

0 8 16 24 MILES

0 8 16 24 KILOMETERS

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

Universal Transverse Mercator projection, Zone 15

North American Datum of 1983

Tomball

The Woodlands

Manvel

Hitchcock

La Marque

Liberty

Jersey 

Village

Prairie 

View

Hempstead

Magnolia

Fulshear

Shepherd

Cleveland

Plum 

Grove

Montgomery Willis

Huntsville

Navasota

Waller

Pattison

Conroe

Spring

Houston

Humble

Aldine

Katy

Channelview

Baytown Galena 

Park

Mont 

Belvieu

Pasadena

Deerpark

Dayton

Santa Fe

Bellaire

West University

Place

Sugar

Land

Missouri

City

Richmond

Pearland

Rosenberg Friendswood

League City Texas City Alvin

Galveston

Angleton

Clute Lake

Jackson

Freeport

River

Brazos

River

San

Bernard

River

Brazos River

Trinity

River

West Fork

San

River

West Fork

San

Jacinto

River

Cedar

Bayou

Buffalo

Bayou

Clear

Lake

Creek

Lake Creek

Caney

Creek

Spring

Oyster

Creek

Brazos

Sheldon

Reservoir

Trinity Bay

Lake

Houston

Lake Conroe

Lake

Livingston

Galveston

Bay

East Bay

West Bay

GULF OF MEXICO

Jacinto

Creek

Creek

AUSTIN COUNTY

FORT BEND

COUNTY

WALKER

COUNTY

MONTGOMERY

COUNTY

SAN JACINTO COUNTY

COUNTY

WALLER 

BRAZORIA 

COUNTY

GALVESTON 

COUNTY

CHAMBERS COUNTY

LIBERTY COUNTY

GRIMES COUNTY

AZOS

COUNTY

WHARTON COUNTY

HARRIS

COUNTY

95°45'

95°45'

95°30'

95°30' 95°15'

95°

95°

30°30'

30°

30°

30°15'

30°15'

29°30'

29°45'

29°45'

29°15'

96°

96°

94°45'

94°45'

94°30'

94°30'

30°30'

29°15'

30°45'

29° 29°

30°45'

29°30'

95°15'

200

50

0

-50

-150

150

100

-100

250

100

-200

-200 -200

100

Study area

TEXAS

Figure 13. Approximate 2017 water-level altitudes and updip limit of the Jasper aquifer, Houston-Galveston region, Texas (water-levelmeasurement data collected during December 2016 through March 2017).
22 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

FM 521

FM 787

FM 2004

90

105

45

249

59

10

99

90

548

321

FM 1960

FM 1764

FM 35

150 FM 1375

225

87

168

30

90

19

156

6

State Loop 336

36

105

90 59

290

59

45

10

610

45

Galveston Rd

Grand Pky

36

N Sam Houston Pky W

S Sam Houston Pky E

E North Belt

Addicks Satsuma Rd

S Belt

146

288

45

190

75

30

90

10

610

35

35

332

6

59

3

146

105

146

61

65

1488

1774

Updip limit of Jasper aquifer (University of Texas,

Bureau of Economic Geology, 1968, 1974; Baker, 1986) 

Boundary of study area

EXPLANATION

Note: 

This change map was created by contouring the set of 

mapped point values computed as the difference in 

water-level altitude at each point (well) for which a 

water-level measurement was made in 2017 and the 

water-level altitude at that point on a gridded surface of 

the 2000 water-level-altitude map (Kasmarek and 

Houston, 2007, sheet 15). 

Gridded-surface values for 2000 (rather than actual 

measured values) were used to compute 

differences (mapped point values) because many 

of the wells measured in 2000 have been 

destroyed or were not measured in 2017. 

Conversely, some of the wells measured in 

2017 either were not measured or were not 

in existence in 2000. Thus, using the 

gridded surface yielded more point values 

than would have been available by using 

the subset of wells measured in both 

2017 and 2000. For the subset of wells 

measured in both 2017 and 2000, the 

mapped point values used were the 

differences in water-level-altitude 

values between 2017 and 2000 

rather than the differences 

between 2017 water-levelaltitude values and 2000 

gridded-surface values.

The area of water-level 

change shown is based 

on availability of 

water-level data 

from 2000.

-20 Line of equal water-level decline—Interval 20 feet

0 Line of zero water-level change

0 8 16 24 MILES

0 8 16 24 KILOMETERS

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

Universal Transverse Mercator projection, Zone 15

North American Datum of 1983

Tomball

The Woodlands

Manvel

Hitchcock

La Marque

Liberty

Jersey 

Village

Prairie 

View

Hempstead

Magnolia

Fulshear

Shepherd

Cleveland

Plum 

Grove

Montgomery Willis

Huntsville

Navasota

Waller

Pattison

Conroe

Spring

Houston

Humble

Aldine

Katy

Channelview

Baytown Galena 

Park

Mont 

Belvieu

Pasadena

Deerpark

Dayton

Santa Fe

Bellaire

West University

Place

Sugar

Land

Missouri

City

Richmond

Pearland

Rosenberg Friendswood

League City Texas City Alvin

Galveston

Angleton

Clute Lake

Jackson

Freeport

River

Brazos

River

San

Bernard

River

Brazos River

Trinity

River

West Fork

San

River

West Fork

San

Jacinto

River

Cedar

Bayou

Buffalo

Bayou

Clear

Lake

Creek

Lake Creek

Caney

Creek

Spring

Oyster

Creek

Brazos

Sheldon

Reservoir

Trinity Bay

Lake

Houston

Lake Conroe

Lake

Livingston

Galveston

Bay

East Bay

West Bay

GULF OF MEXICO

Jacinto

Creek

Creek

AUSTIN COUNTY

FORT BEND

COUNTY

WALKER

COUNTY

MONTGOMERY

COUNTY

SAN JACINTO COUNTY

COUNTY

WALLER 

BRAZORIA 

COUNTY

GALVESTON 

COUNTY

CHAMBERS COUNTY

LIBERTY COUNTY

GRIMES COUNTY

AZOS

COUNTY

WHARTON COUNTY

HARRIS

COUNTY

95°45'

95°45'

95°30'

95°30' 95°15'

95°

95°

30°30'

30°

30°

30°15'

30°15'

29°30'

29°45'

29°45'

29°15'

96°

96°

94°45'

94°45'

94°30'

94°30'

30°30'

29°15'

30°45'

29° 29°

30°45'

29°30'

95°15'

-20

-40

-60

-80

-100

-120

-180

-140

-160

-200

-80

-60

-60

-80

-180

0

-220

-100

Study area

TEXAS

Figure 14. Approximate 2000–17 water-level changes in the Jasper aquifer, Houston-Galveston region, Texas.
Compaction of Subsurface Sediments in the Chicot and Evangeline Aquifers 23

Compaction of Subsurface Sediments 

in the Chicot and Evangeline Aquifers

Compaction of subsurface sediments (mostly in the 

fine-grained silt and clay layers because relatively limited 

compaction occurs in sand layers) in the Chicot and 

Evangeline aquifers was recorded continuously by using 

analog technology at the 13 extensometers at 11 sites (fig. 8) 

that were either activated or installed between 1973 and 1980. 

The cumulative compaction data for each extensometer are 

collected about 13 times per year during site visits. During 

each site visit, the amount of cumulative compaction at a 

site is determined by subtracting the previously recorded 

compaction value from the ending compaction value. 

Cumulative compaction over the course of a year is the 

difference between the value recorded during the first site visit 

in January and the value recorded during the last site visit in 

late November or December.

Graphs of cumulative compaction are presented for 

1973 (or later depending on when each extensometer was 

activated or installed) through late November or December 

2016 (figs. 15 and 16). The supporting cumulative compaction 

data used for the creation of the graphs are available in 

Ramage (2017). The selected depth of the extensometer 

(figs. 15–16) determines the total thickness of sediment over 

which compaction is measured by the extensometer. Six of the 

extensometers measure compaction that occurs in solely the 

Chicot aquifer (East End, Johnson Space Center, Texas CityMoses Lake, Baytown C–1 [shallow], Clear Lake [shallow], 

and Seabrook), and seven of the extensometers measure 

compaction that occurs in both the Chicot and Evangeline 

aquifers (Lake Houston, Northeast, Southwest, Addicks, 

Baytown C–2 [deep], Clear Lake [deep], and Pasadena) 

(figs. 15–16).

Prior to the establishment of the HGSD in 1975, the 

withdrawal of groundwater from the Chicot and Evangeline 

aquifers was unregulated, and water levels in the aquifers 

were declining with associated depressuring, dewatering, 

and compaction (Coplin and Galloway, 1999). By 1977, the 

withdrawals had resulted in water-level-altitude declines of 

as much as 300 and 350 ft below datum in the Chicot and 

Evangeline aquifers, respectively, in southeastern Harris 

County (Gabrysch, 1979), and correspondingly, by 1979, as 

much as 10 ft of subsidence had occurred in the HoustonGalveston region (Coplin and Galloway, 1999). A more 

recent USGS study determined that from the early 1900s until 

2001 as much as 12–13 ft of subsidence had occurred in the 

Pasadena and Baytown areas in Harris County and that most 

(77–97 percent) of the subsidence in the Houston-Galveston 

region had occurred prior to the extensometer construction 

that began in 1973 (Kasmarek, Gabrysch, and Johnson, 

2010). When reductions in groundwater withdrawals were 

first mandated following the establishment of the HGSD in 

1975 (Harris-Galveston Subsidence District, 2015), the rate 

of groundwater withdrawal began to gradually decrease in 

Harris and Galveston Counties, and incrementally, a reduction 

in the rate of compaction was recorded by the extensometers 

(figs. 15–16). Coincident with the curtailment of groundwater 

withdrawals, water levels in the aquifers began to rise and 

recover (Kasmarek and others, 2016, sheets 5 and 10). As 

discussed in the “Water-Level Altitudes and Changes” section 

of this report, from 1977 to 2017 the decreases in groundwater 

withdrawals have caused water levels in the Chicot and 

Evangeline aquifers to rise as much as 200 and 240 ft, 

respectively.

For each extensometer, the cumulative compaction data 

discussed in this report begin on the extensometer installation 

date of the year it was installed, but for subsequent years, 

the data begin on the first site visit in January and end on 

the last site visit of the year (typically in late November or 

December) (Ramage, 2017) (figs. 15 and 16). From January 

through late November or December 2016, the Addicks, Lake 

Houston, Southwest, and Northeast extensometers recorded 

net decreases in land-surface elevation, but the Baytown C–1 

(shallow), Baytown C–2 (deep), Clear Lake (shallow), Clear 

Lake (deep), East End, Johnson Space Center, Pasadena, 

Seabrook, and Texas City-Moses Lake extensometers recorded 

net increases in land-surface elevation (Ramage, 2017). For 

2016, cumulative compaction data ranged from 0.096 ft 

(fig. 16) (Ramage, 2017) at the Texas City-Moses Lake 

extensometer, which measures compaction of solely the Chicot 

aquifer, to 3.700 ft (fig. 15) (Ramage, 2017) at the Addicks 

extensometer, which measures compaction of both the Chicot 

and Evangeline aquifers. 

The graphs of cumulative compaction data indicate 

that the slopes of the graphs and rates of compaction were 

substantially higher when the extensometers were initially 

installed as early as 1973 compared to the slopes of the graphs 

and rates of compaction in the subsequent years (figs. 15 

and 16). These asymptotic compaction-rate patterns are 

directly caused by the rise in water levels in the aquifers as 

groundwater withdrawals decreased in response to regulatory 

mandates of the HGSD (Harris-Galveston Subsidence 

District, 2015). As water levels in the aquifers began to 

rise and recover, the hydrostatic pressure increased, and 

residual excess pore pressure equilibrated; hence, the rates of 

compaction progressively decreased. Comparing the locations 

of the extensometers (fig. 8) to the geographic areas of the 

1977–2017 long-term water-level changes in the Chicot and 

Evangeline aquifers (figs. 10 and 12), the relatively large 

areas of water-level rises coincide with the compaction-rate 

decreases, with the exception of the Addicks extensometer 

site. The rate of compaction varies from site to site because of 

the differences in groundwater-withdrawal rates in the adjacent 

areas of each site; differences in the ratios of sand, silt, and 

clay and corresponding compressibilities of the subsurface 

sediments at each site; and the previously established 

preconsolidation heads as discussed in Kasmarek (2013). The 

Pasadena and Baytown extensometer sites are proximal to the 

area of maximum historical subsidence rates, near Galveston 

Bay. The patterns of cumulative compaction at the Pasadena 
24 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

Year

Measured cumulative compaction, in feet

1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3.0

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

LJ–65–32–401 (Johnson Space Center)

Extensometer depth: 770 feet below 

land surface; compaction in the Chicot

aquifer

LJ–65–12–726 (Addicks)

Extensometer depth: 1,802 feet

below land surface; compaction in

the Chicot and Evangeline aquifers

LJ–65–22–622 (East End)

Extensometer depth: 995 feet

below land surface; compaction 

in the Chicot aquifer

LJ–65–21–226 (Southwest)

Extensometer depth: 2,358 feet

below land surface; compaction in 

the Chicot and Evangeline aquifers

LJ–65–07–909 (Lake Houston)

Extensometer depth: 1,940 feet

below land surface; compaction in 

the Chicot and Evangeline aquifers

LJ–65–14–746 (Northeast)

Extensometer depth: 2,170 feet

below land surface; compaction in

the Chicot and Evangeline aquifers

Figure 15. Measured cumulative compaction of subsurface sediments at the Lake Houston, Northeast, East End, Southwest, Johnson 

Space Center, and Addicks borehole-extensometer sites (sites are depicted on fig. 8), 1973–2016.
Compaction of Subsurface Sediments in the Chicot and Evangeline Aquifers 25

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Measured cumulative compaction, in feet

Year

KH–64–33–920 (Texas City-Moses Lake)

Extensometer depth: 800 feet

below land surface; compaction

in the Chicot aquifer

LJ–65–16–930 (Baytown C–1 [shallow])

Extensometer depth: 431 feet below

land surface; compaction in the

Chicot aquifer

LJ–65–16–931 (Baytown C–2 [deep])

Extensometer depth: 1,475 feet below

land surface; compaction in the Chicot

and Evangeline aquifers

LJ–65–32–625 (Seabrook)

Extensometer depth: 1,381 feet below

land surface; compaction in the

Chicot aquifer

LJ–65–32–424 (Clear Lake [shallow])

Extensometer depth: 1,740 feet below

land surface; compaction in the

Chicot aquifer

LJ–65–32–428 (Clear Lake [deep])

Extensometer depth: 3,072 feet below

land surface; compaction in the Chicot

and Evangeline aquifers

LJ–65–23–322 (Pasadena)

Extensometer depth: 2,831 feet

below land surface; compaction in

the Chicot and Evangeline aquifers

A

B

C

Figure 16. Measured cumulative compaction of subsurface sediments at the A, Texas City-Moses Lake, Baytown C–1 (shallow), 

Baytown C–2 (deep), and Seabrook borehole-extensometer sites; B, Clear Lake (shallow) and Clear Lake (deep) borehole-extensometer 

sites; and C, Pasadena borehole-extensometer site (sites are depicted on fig. 8), 1973–2016.
26 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

extensometer and both Baytown extensometers were different 

compared to the patterns of cumulative compaction at the 

other extensometer sites (fig. 16). The graphs of cumulative 

compaction data from installation in 1975 through 2016 for 

the Pasadena extensometer and from installation in 1973 

through 2016 for the Baytown C–1 (shallow) and Baytown 

C–2 (deep) extensometers depict cumulative compaction 

values of 0.487 (Pasadena extensometer), 0.973 (Baytown C–1 

[shallow] extensometer), and 1.105 ft (Baytown C–2 [deep] 

extensometer) (fig. 16) (Ramage, 2017).

The Addicks extensometer site is in regulatory area 3 

(fig. 8) of the HGSD and, as such, was not scheduled for a 

30-percent groundwater withdrawal reduction until 2011 

(Harris-Galveston Subsidence District, 2013); therefore, 

the Addicks extensometer site is in a part of the study area 

where groundwater withdrawals remained relatively large for 

many years. Cumulative compaction data from the Addicks 

extensometer (fig. 15) indicate a consistent rate of compaction 

beginning from when the extensometer was installed in mid1974 through about mid-2003. During the period from mid1974 through mid-2003, the rate of compaction was consistent 

at about 0.1 ft per year, caused by continuing groundwater 

withdrawals in the area adjacent to the Addicks extensometer 

site. Additionally, the rate of compaction during August 2003 

through December 2003 (Ramage, 2017) decreased to about 

0.004 ft; this decrease in the rate of compaction likely was 

caused by changes in withdrawals, as the adjacent publicsupply well field was observed by USGS personnel to be 

inoperative during this 5-month period. From December 

2003 to about April 2005, data indicate a slight increase in 

land-surface elevation (rebound), followed by a decrease in 

land-surface elevation until February 2006. Again in March 

2006, a gradual increase in land-surface elevation occurred 

until March 2008. Compaction resumed (albeit at a lower rate 

than in 2008) in May 2009, and net decrease in land-surface 

elevation continued to occur through October 2013. The rate 

of compaction recorded by the Addicks extensometer averaged 

about 0.025 ft per year during 2009–16 on the basis of a 

beginning value of 3.502 ft in January 2009 and an ending 

value of 3.700 ft in December 2016 (fig. 15).

The graph of cumulative compaction data obtained from 

the Seabrook extensometer (fig. 16) indicates a seasonal 

sinusoidal pattern in land-surface elevation caused by a 

decrease in land-surface elevation during the hot and dry 

months of June through September, when rates of groundwater 

withdrawal are higher. This decrease in land-surface elevation 

is followed by an increase in land-surface elevation during 

the cooler and wetter months of December through March, 

when rates of groundwater withdrawal are lower compared to 

the rest of year. Additionally, during the hot and dry months 

of June through September, the surficial clayey sediments 

desiccate and shrink, but as the heat of the summer dissipates 

and the cooler and wetter months arrive with a decrease in 

groundwater withdrawals, the sediments rehydrate and swell, 

thereby causing an increase in land-surface elevation, or 

rebound (U.S. Geological Survey, 2015).

The Baytown C–1 (shallow) and Baytown C–2 (deep) 

extensometers began recording cumulative compaction 

data in July 1973 (fig. 16) (Ramage, 2017). From July 1973 

through about early May 2009, the cumulative compaction 

data recorded at the Baytown C–1 (shallow) extensometer 

were consistently lower than the cumulative compaction 

data recorded at the Baytown C–2 (deep) extensometer, 

with a difference as much as 0.465 ft recorded in July and 

August 2001. In late May 2009, however, an increase in the 

rate of compaction recorded at the Baytown C–1 (shallow) 

extensometer began, and by December 2016, the difference 

in cumulative compaction data for the two sites was within 

0.132 ft (fig. 16). The cumulative compaction amounts 

recorded by the Baytown C–1 (shallow) and the Baytown C–2 

(deep) extensometers have been similar since 2011 because 

of the increase in the rate of compaction at the Baytown C–1 

(shallow) extensometer during 2009–11. The cause of the 

recent increase in the rate of compaction at the Baytown C–1 

(shallow) extensometer is not known. Unlike the cumulative 

compaction amounts that were historically appreciably 

different at the Baytown shallow and deep extensometers, the 

cumulative compaction amounts recorded by the Clear Lake 

(shallow) and Clear Lake (deep) extensometers have been 

similar throughout their periods of record (fig. 16).

Cumulative compaction data for the Texas City-Moses 

Lake extensometer indicate not only that a halt in the rate 

of compaction occurred but also that, from January 1981 

until December 2016, a slight rise in land-surface elevation 

of approximately 0.097 ft has occurred (fig. 16) (Ramage, 

2017). The cumulative compaction data for the Pasadena, 

Clear Lake (shallow), Clear Lake (deep), Seabrook, Baytown 

C–1 (shallow), Baytown C–2 (deep), and Johnson Space 

Center extensometers indicate a slight increase in land-surface 

elevation from late 1978 to early 1980 (figs. 15 and 16) 

because a ruptured natural gas well pressurized the confined 

aquifer system and caused water levels to rise in the area 

adjacent to the ruptured well (Gabrysch, 1984). Gradually, 

the pressure in the aquifer dissipated, and the process of 

compaction subsequently returned to rates similar to those 

prior to the pressuring event.

Data Limitations

Before 2016, most of the land-surface elevations at wells 

used in the annual series of reports were derived from USGS 

1:24,000-scale 7.5-minute topographic quadrangle maps, 

which have a 5-ft contour, or from a digital elevation model 

(DEM). Land-surface elevations at wells installed in Harris 

County were derived from a DEM obtained from the 2001 

Tropical Storm Allison Recovery Project land-surface dataset 

that used light detection and ranging (lidar) technology (Peggy 

Cobb, Terrapoint USA, Inc., written commun., 2009). The 

land-surface elevations were referenced to NAVD 88 by using 

Corpscon version 6 (U.S. Army Corps of Engineers, 2006). 
Summary 27

The lidar data were contoured at a 1-ft interval, thereby 

providing an accuracy of 0.5 ft. The topographic quadrangle 

maps for the Gulf of Mexico coastal area were typically 

contoured at a 5-ft interval, thereby providing 2.5-ft accuracy; 

thus, the lidar data provide about five times better accuracy 

when compared to 7.5-minute topographic quadrangle maps 

(Kasmarek, Gabrysch, and Johnson, 2010). Additionally, all 

of the topographic quadrangle maps were variously dated, 

and not all of the maps were updated with changes in landsurface elevations that might have occurred since their initial 

publication. 

In 2016, the authors updated the land-surface-elevation 

data for the study area. To determine land-surface elevations, 

a corresponding land-surface-datum value for each well was 

obtained by using USGS National Geospatial Program 3DEP 

values referenced to NAVD 88 (U.S. Geological Survey, 

2017b). Updated land-surface-datum values from 3DEP were 

applied to the site information stored in the NWIS database 

for all sites in the study area and were used to enhance the 

accuracy of the maps depicting water-level altitudes and the 

accuracy of subsequent calculations of point values that are 

used as control data during the creation of the water-levelaltitude maps (figs. 9, 11, and 13) and long-term water-levelchange maps (figs. 10, 12, and 14). Additionally for all sites, 

the values of horizontal coordinate information (latitude 

and longitude) were updated to the North American Datum 

of 1983, and these data were also used to update the NWIS 

database.

Land-surface elevations were not updated to adjust 

previously published water-level altitudes and used in the 

analysis of differences between current year and historical 

year maps of water-level altitude. Because of sediments with a 

prevalence of montmorillonitic clays and a large dependence 

on groundwater withdrawals to meet water-use demand, the 

land-surface elevation is not constant. Any changes in landsurface elevation could affect the accuracy of water-levelchange maps depicting the differences between the current 

year (2017) and the historical year (1977) altitudes.

The depictions of water-level altitudes and changes at 

any specific location are considered to represent a regionalscale approximation and, as such, are not intended for use 

in engineering or other design applications. The water-level 

altitudes and changes presented in this report were rounded to 

the nearest foot; the values depicted on the maps represent a 

mathematical approximation that could vary as much as plus 

or minus 0.5 ft in addition to accuracies associated with the 

DEM source data. Use of these data for critical or local-scale 

applications is not advised without full awareness of the data 

limitations. Users need to exercise discretion when drawing 

conclusions or making policy decisions on the basis of these 

contoured depictions.

The graphs of long-term cumulative compaction 

data (figs. 15 and 16) represent compaction of subsurface 

sediments above the depth of the cement plug (fig. 7); by 

design, any compaction or vertical movement that occurs 

below these depths in stratigraphically lower units or resulting 

from tectonic processes is not recorded by the extensometers. 

Depending on the total depth of the extensometer, the 

cumulative compaction at a given extensometer could 

represent compaction of the sediments of solely the 

Chicot aquifer (for example, the Baytown C–1 [shallow] 

extensometer) or could represent compaction of the sediments 

in both the Chicot and Evangeline aquifers (for example, the 

Addicks extensometer).

The rate of compaction varies from site to site because 

of differences in groundwater withdrawals in the areas 

adjacent to each extensometer site; differences among sites 

in the ratios of sand, silt, and clay and their corresponding 

compressibilities; and previously established preconsolidation 

heads. It is not appropriate, therefore, to extrapolate or infer a 

rate of compaction for an adjacent area on the basis of the rate 

of compaction recorded by proximal extensometers.

Summary

The Houston-Galveston region, Texas—consisting 

of Harris, Galveston, Fort Bend, Montgomery, Brazoria, 

Chambers, Grimes, Liberty, San Jacinto, Walker, and Waller 

Counties—represents one of the largest areas of landsurface subsidence (hereinafter referred to as “subsidence”) 

in the United States. By 1979, as much as 10 feet (ft) of 

subsidence had occurred in the Houston-Galveston region, 

and approximately 3,200 square miles (mi2) of the 11,000-

mi2 geographic area had subsided more than 1 ft. Most of the 

subsidence in the Houston-Galveston region has occurred as 

a direct result of groundwater withdrawals that depressured 

and dewatered the Chicot and Evangeline aquifers, thereby 

causing compaction of the aquifer sediments. Groundwater 

withdrawn from the Chicot, Evangeline, and Jasper aquifers 

has been the primary source of water for municipal supply, 

commercial and industrial use, and irrigation in the HoustonGalveston region since the early 1900s. To address the 

issues associated with subsidence and subsequent increased 

flooding, the 64th Texas State Legislature in 1975 authorized 

the establishment of the Harris-Galveston Subsidence District 

to regulate and reduce groundwater withdrawals in Harris 

and Galveston Counties. Subsequently, the Texas State 

Legislature established the Fort Bend Subsidence District in 

1989 and the Lone Star Groundwater Conservation District in 

2001 to regulate groundwater withdrawals in Fort Bend and 

Montgomery Counties, respectively. The Brazoria County 

Groundwater Conservation District was established by the 

Texas State Legislature in 2003 to maintain the quality and 

availability of the county’s groundwater resources for current 

users and future generations. This report, prepared by the U.S. 

Geological Survey in cooperation with the Harris-Galveston 

Subsidence District, City of Houston, Fort Bend Subsidence 

District, Lone Star Groundwater Conservation District, and 

Brazoria County Groundwater Conservation District, is one 

in an annual series of reports depicting water-level altitudes 
28 Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas 

and water-level changes in the Chicot, Evangeline, and Jasper 

aquifers and measured cumulative compaction of subsurface 

sediments in the Chicot and Evangeline aquifers in the 

Houston-Galveston region. Water levels in wells screened in 

the Chicot, Evangeline, and Jasper aquifers were measured 

during December 2016 through March 2017 (water levels 

usually are higher during these months compared to the rest of 

the year).

This report contains regional-scale maps depicting 

approximate 2017 water-level altitudes and long-term 

water-level changes for the Chicot, Evangeline, and Jasper 

aquifers; a map depicting locations of borehole-extensometer 

(hereinafter referred to as “extensometer”) sites; and graphs 

depicting cumulative compaction of subsurface sediments 

measured by the extensometers beginning in 1973 (or later 

depending on when the extensometer was activated or 

installed) through late November or December 2016.

The water-level altitudes in the Chicot, Evangeline, and 

Jasper aquifers depicted in this report for 2017 were measured 

following a year of abundant rainfall. The wetter-thannormal conditions were accompanied by warmer-than-normal 

temperatures; the average annual temperature in 2016 for 

Houston was 1.6 degrees Fahrenheit above normal. Because 

more groundwater might be withdrawn for irrigation purposes 

if the weather is warmer than normal during the irrigation 

season, the warmer-than-normal temperatures in 2016 might 

somewhat counteract the wetter-than-normal conditions in 

terms of groundwater withdrawals. Compared to 2016, water 

levels in 2017 increased in about 54, 48, and 80 percent of the 

wells screened in the Chicot, Evangeline, and Jasper aquifers, 

respectively. Water levels in 2017 decreased compared to 2016 

in about 27, 43, and 18 percent of the wells screened in the 

Chicot, Evangeline, and Jasper aquifers, respectively. 

Water-level-measurement data from 164 wells were 

used to depict the approximate 2017 water-level-altitude 

contours for the Chicot aquifer. In 2017, water-level-altitude 

contours for the Chicot aquifer ranged from 200 ft below the 

North American Vertical Datum of 1988 (hereinafter referred 

to as “datum”) in two localized areas in southwestern and 

northwestern Harris County to 200 ft above datum in westcentral Montgomery County. The largest water-level-altitude 

decline (120 ft) depicted by the 1977–2017 water-level-change 

contours for the Chicot aquifer was in northwestern Harris 

County. A broad area where water-level altitudes declined in 

the Chicot aquifer extends from northwestern, north-central, 

and southwestern Harris County across parts of north-central, 

eastern, and south-central Fort Bend County into southeastern 

Waller County. In addition to the broad area of decline, waterlevel altitudes also declined from Fort Bend County into 

northwestern Brazoria County. Adjacent to the areas where 

water levels declined was a broad area where water levels rose 

in central, eastern, and southeastern Harris County, most of 

Galveston County, eastern and northernmost Brazoria County, 

and northeastern Fort Bend County. There were also small 

isolated areas in northwestern and southwestern Fort Bend 

County where water-level altitudes rose 20 ft. The largest rise 

(200 ft) in water-level altitudes in the Chicot aquifer from 

1977 to 2017 was in southeastern Harris County.

Water-level-measurement data from 305 wells were 

used to depict the approximate 2017 water-level-altitude 

contours for the Evangeline aquifer. In 2017, the waterlevel-altitude contours for the Evangeline aquifer indicated 

two areas where the water-level altitudes were 250 ft below 

datum—one of these areas extended from south-central 

Montgomery County into north-central Harris County, and the 

other was in western Harris County. Water-level altitudes in 

the Evangeline aquifer ranged from 50 to 200 ft below datum 

throughout most of Harris County in 2017. In Montgomery 

County, water-level altitudes in the Evangeline aquifer in 

2017 ranged from the aforementioned area where they were 

250 ft below datum to an area where they were 200 ft above 

datum in the northwestern part of the county. The waterlevel-altitude contour of 200 ft above datum extended from 

southern Grimes County, through a small part of northern 

Waller County, into northwestern Montgomery County. The 

1977–2017 water-level-change contours for the Evangeline 

aquifer depict a broad area where water-level altitudes 

declined in north-central Harris and south-central Montgomery 

Counties, extending through north-central, northwestern, and 

southwestern Harris County into western Liberty, southeastern 

and northeastern Waller, and northeastern and east-central 

Fort Bend Counties. The largest water-level-altitude decline 

(280 ft) was in north-central Harris and south-central 

Montgomery Counties. Water-level altitudes rose in a broad 

area from central, east-central, and southern Harris County 

extending into the northernmost part of Brazoria County, the 

northernmost part of Galveston County, and the southwestern 

area of Liberty County. The largest rise in water level-altitudes 

in the Evangeline aquifer from 1977 to 2017 (240 ft) was in 

southeastern Harris County.

Water-level-measurement data from 102 wells were used 

to depict the approximate 2017 water-level-altitude contours 

for the Jasper aquifer. In 2017, water-level-altitude contours 

for the Jasper aquifer ranged from 200 ft below datum in 

three isolated areas of south-central Montgomery County (the 

westernmost of these areas extended slightly into north-central 

Harris County) to 250 ft above datum in extreme northwestern 

Montgomery County, northeastern Grimes County, and 

southwestern Walker County. The 2000–17 water-level-change 

contours for the Jasper aquifer depict water-level declines in 

a broad area throughout most of Montgomery County and 

in parts of Waller, Grimes, and Harris Counties, with the 

largest decline (220 ft) in an isolated area in south-central 

Montgomery County.

Compaction of subsurface sediments (mostly in the 

fine-grained silt and clay layers) in the Chicot and Evangeline 

aquifers was recorded continuously by using analog 

technology at the 13 extensometers at 11 sites that were either 

activated or installed between 1973 and 1980. The compaction 

rates measured by each extensometer were substantially higher 

when the extensometers were initially installed compared 

to compaction rates in subsequent years. When reductions 
References Cited 29

in groundwater withdrawals were mandated following the 

establishment of the Harris-Galveston Subsidence District 

in 1975, the rates of groundwater withdrawal began to 

decrease gradually in Harris and Galveston Counties, as did 

the rate of compaction. Coincident with the curtailment of 

groundwater withdrawals, the water levels in the aquifers 

began to rise and recover. From 1977 to 2017 the decreases 

in groundwater withdrawals have caused water levels in 

the Chicot and Evangeline aquifers to rise as much as 200 

and 240 ft, respectively. From January through December 

2016, the Addicks, Lake Houston, Southwest, and Northeast 

extensometers recorded net decreases in land-surface 

elevation, but the Baytown C–1 (shallow), Baytown C–2 

(deep), Clear Lake (shallow), Clear Lake (deep), East End, 

Johnson Space Center, Pasadena, Seabrook, and Texas CityMoses Lake extensometers recorded net increases in landsurface elevation. During the period of record beginning in 

1973 (or later depending on activation or installation date) 

and ending in late November or December 2016, measured 

cumulative compaction at the 13 extensometers ranged from 

0.096 ft at the Texas City-Moses Lake extensometer, which 

measures compaction in solely the Chicot aquifer, to 3.700 ft 

at the Addicks extensometer, which measures compaction in 

both the Chicot and Evangeline aquifers. 

The rate of compaction varies from site to site because 

of differences in rates of groundwater withdrawal in the areas 

adjacent to each extensometer site; differences among sites 

in the ratios of sand, silt, and clay and their corresponding 

compressibilities; and previously established preconsolidation 

heads. It is not appropriate, therefore, to extrapolate or infer a 

rate of compaction for an adjacent area on the basis of the rate 

of compaction recorded by proximal extensometers.

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For more information about this publication, contact

Director, Texas Water Science Center

U.S. Geological Survey

1505 Ferguson Lane

Austin, TX 78754–4501 

For additional information visit http://tx.usgs.gov/.

Publishing support provided by

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Kasmarek and Ramage—Water-Level Altitudes 2017 and Water-Level Changes and Compaction 1973–2016, Houston-Galveston Region, Texas—SIR 2017–5080

ISSN 2328-031X (print)

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20175080

I SBN 978- 1- 4113- 4156-2

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