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

Status of Groundwater-Level Altitudes and Long-Term 

Groundwater-Level Changes in the Chicot, Evangeline, and 

Jasper Aquifers, Houston-Galveston Region, Texas, 2020

Scientific Investigations Report 2020–5089

U.S. Department of the Interior

U.S. Geological Survey
Cover. Front, left to right: Photographs showing U.S. Geological Survey (USGS) hydrologic technician measuring depth to groundwater 

at a production well at USGS site 302409095414201 (station TS-60-35-814) in Montgomery County, Texas, February 25, 2020.

Back: Photograph showing USGS hydrologist measuring depth to groundwater at a production well at USGS site 295228095262901 

(station LJ-65-13-220) in Harris County, Texas, December 19, 2019.
Status of Groundwater-Level Altitudes and 

Long-Term Groundwater-Level Changes 

in the Chicot, Evangeline, and Jasper 

Aquifers, Houston-Galveston Region, 

Texas, 2020

By Christopher L. Braun 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 2020–5089

U.S. Department of the Interior

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

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2020

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:

Braun, C.L., and Ramage, J.K., 2020, Status of groundwater-level altitudes and long-term groundwater-level 

changes in the Chicot, Evangeline, and Jasper aquifers, Houston-Galveston region, Texas, 2020: U.S. Geological 

Survey Scientific Investigations Report 2020–5089, 18 p., https://doi.org/10.3133/sir20205089.

Associated data for this publication:

Ramage, J.K., 2020, Depth to groundwater measured from wells completed in the Chicot, Evangeline, and Jasper 

aquifers, Houston-Galveston region, Texas, 2020: U.S. Geological Survey data release, https://doi.org/10.5066/

P90EJL2E.

Ramage, J.K., and Braun, C.L., 2020, Groundwater-level altitudes and long-term groundwater-level changes in 

the Chicot, Evangeline, and Jasper aquifers, Houston-Galveston region, Texas, 2020: U.S. Geological Survey data 

release, https://doi.org/10.5066/P98IX48O.

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 following U.S. Geological Survey 

colleagues for assisting in collecting groundwater-level data outside of normal duty hours 

as necessary and for assisting with processing and analyzing the large amount of resulting data within an abbreviated period: Dexter W. Brown, Robert H. Ellis, Eric M. Boeding, 

Keith E. Mecum, Matthew L. Barnes, Charles P. Coker, Samuel H. Rendon, Jason D. Payne, 

Kyle Rennell, and Stephen Bradford.
iv

Contents

Acknowledgments........................................................................................................................................iii

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

Introduction.....................................................................................................................................................1

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

Hydrogeology of the Study Area ........................................................................................................3

Previous Studies ...................................................................................................................................6

Methods...........................................................................................................................................................6

Groundwater-Level Measurements...................................................................................................6

Determination of Groundwater-Level Altitudes...............................................................................7

Depicting Long-Term Groundwater-Level Changes........................................................................7

Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes.......................................8

Chicot Aquifer........................................................................................................................................8

Evangeline Aquifer................................................................................................................................8

Jasper Aquifer.......................................................................................................................................8

Data Limitations............................................................................................................................................15

Summary........................................................................................................................................................15

References Cited..........................................................................................................................................15

Figures

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

of hydrogeologic cross section A–A ́; and outcrops and updip limits of the 

hydrogeologic units in the Gulf Coast aquifer system in the Houston-Galveston 

region study area, Texas..............................................................................................................2

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

Montgomery, Harris, and Galveston Counties, Texas.............................................................4

 3. Stratigraphic column showing geologic and hydrogeologic units of the Gulf Coast 

aquifer system in the Houston-Galveston region study area, Texas ...................................5

 4. Map showing approximate 2020 groundwater-level altitudes and updip limit of the 

Chicot aquifer, Houston-Galveston region, Texas...................................................................9

 5. Map showing approximate 1977–2020 groundwater-level changes in the Chicot 

aquifer, Houston-Galveston region, Texas..............................................................................10

 6. Map showing approximate 2020 groundwater-level altitudes and updip limit of the 

Evangeline aquifer, Houston-Galveston region, Texas.........................................................11

 7. Map showing approximate 1977–2020 groundwater-level changes in the Evangeline 

aquifer, Houston-Galveston region, Texas..............................................................................12

 8. Map showing approximate 2020 groundwater-level altitudes and updip limit of the 

Jasper aquifer, Houston-Galveston region, Texas................................................................13

 9. Map showing approximate 2000–20 groundwater-level changes in the Jasper 

aquifer, Houston-Galveston region, Texas..............................................................................14
v

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

Length

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

Length

meter (m) 3.281 foot (ft) 

meter (m) 1.094 yard (yd) 

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).

Abbreviations

BCGCD Brazoria County Groundwater Conservation District

DEM digital elevation model

FBSD Fort Bend Subsidence District

GIS geographic information system

HGSD Harris-Galveston Subsidence District

LSGCD Lone Star Groundwater Conservation District

NWIS National Water Information System

USGS U.S. Geological Survey

Status of Groundwater-Level Altitudes and Long-Term 

Groundwater-Level Changes in the Chicot, Evangeline, and 

Jasper Aquifers, Houston-Galveston Region, Texas, 2020

By Christopher L. Braun and Jason K. Ramage

Abstract

Since the early 1900s, most of the groundwater 

withdrawals in the Houston-Galveston region, Texas, have 

been from the three primary aquifers that compose the 

Gulf Coast aquifer system—the Chicot, Evangeline, and 

Jasper aquifers. Withdrawals from these aquifers are used 

for municipal supply, commercial and industrial use, and 

irrigation. 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 the status of groundwater-level altitudes 

and long-term groundwater-level changes in the Chicot, 

Evangeline, and Jasper aquifers in the Houston-Galveston 

region. This report contains regional-scale maps depicting 

approximate 2020 groundwater-level altitudes (represented by 

measurements made during December 2019 through March 

2020) and long-term groundwater-level changes in the Chicot, 

Evangeline, and Jasper aquifers.

In 2020, groundwater-level-altitude contours for the 

Chicot aquifer ranged from 150 feet (ft) below the North 

American Vertical Datum of 1988 (hereinafter referred to as 

“datum”) to 200 ft above datum. The 1977–2020 groundwaterlevel-change contours for the Chicot aquifer depict a large 

area of decline in groundwater-level altitudes (120 ft) in 

northwestern Harris County. The largest rise in groundwaterlevel altitudes in the Chicot aquifer from 1977 to 2020 (200 ft) 

was in southeastern Harris County.

In 2020, groundwater-level-altitude contours for the 

Evangeline aquifer ranged from 250 ft below datum to 200 

ft above datum. The 1977–2020 groundwater-level-change 

contours for the Evangeline aquifer depict broad areas where 

groundwater-level altitudes either declined or rose. The largest 

decline in groundwater-level altitudes (280 ft) was in southern 

Montgomery and northern Harris Counties. The largest rise 

in groundwater-level altitudes in the Evangeline aquifer from 

1977 to 2020 (240 ft) was in southeastern Harris County.

In 2020, groundwater-level-altitude contours for the Jasper 

aquifer ranged from 200 ft below datum to 250 ft above datum. 

The 2000–20 groundwater-level-change contours for the Jasper 

aquifer depict groundwater-level declines throughout most of 

the study area where groundwater-level-altitude data from the 

Jasper aquifer were collected, with the largest decline (220 ft) 

in southern Montgomery County.

Introduction

The Houston-Galveston region, Texas, includes portions of 

11 counties (Harris, Galveston, Fort Bend, Montgomery, 

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

and Waller) and is approximately 11,000 square miles (fig. 1). 

Groundwater withdrawn from the three primary aquifers 

that compose the Gulf Coast aquifer system—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 annually, resulting in land-surface subsidence in 

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

By 1977, the withdrawals had resulted in groundwater-level 

declines in southeastern Harris County of 300 and 350 feet (ft) 

below the North American Vertical Datum of 1988 (NAVD 

88; hereinafter referred to as “datum”) in the Chicot and 

Evangeline aquifers, respectively (Gabrysch, 1979).

To regulate and reduce groundwater withdrawals 

in Harris and Galveston Counties, the 64th Texas State 

Legislature authorized the establishment of the HarrisGalveston Subsidence District (HGSD) in 1975 (HarrisGalveston Subsidence District, 2020). After establishing the 

HGSD, the Texas State Legislature established an additional 

subsidence district (Fort Bend Subsidence District [FBSD]) 

and four groundwater conservation districts (Lone Star 

Groundwater Conservation District [LSGCD], Brazoria 
2 Status of Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes, Houston-Galveston Region, Texas, 2020

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

Friendswood Rosenberg

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 

cross 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

 HarrisGalveston 

Subsidence 

District

Fort Bend 

Subsidence

District

Lone Star Groundwater 

Conservation 

District

Brazoria 

 County 

 Groundwater 

 Conservation 

 District

Bluebonnet Groundwater 

Conservation District

Lower Trinity

Groundwater 

Conservation

District

Area A

Area B

Area 3

Area 2

Area 1

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

Study area

LOCATION MAP

TEXAS

Approximate trace of hydrogeologic cross 

 section on figure 2

6 Approximate location of well on figure 2

Chicot aquifer

Outcrops and updip limits of the geologic

 unit(s) that compose the

Evangeline aquifer

Burkeville confining unit

Jasper aquifer

Outcrop of the geologic units that compose

 the Catahoula confining system

Note: Aquifer data from Strom and others, 2003a, b, c;

Kasmarek and Robinson, 2004

laf20-1001_fig 01

Groundwater

not regulated

Figure 1. Locations of groundwater regulatory districts; approximate trace of hydrogeologic cross section A–A ́; and outcrops 

and updip limits of the hydrogeologic units in the Gulf Coast aquifer system in the Houston-Galveston region study area, Texas 

(modified from Strom and others, 2003a, b, c; Kasmarek and Robinson, 2004).
Introduction 3

County Groundwater Conservation District [BCGCD], 

Bluebonnet Groundwater Conservation District, and 

Lower Trinity Groundwater Conservation District) in the 

Houston-Galveston region (fig. 1) to enable the regulation of 

groundwater withdrawals within their respective jurisdictions. 

The FBSD was established by the 71st Texas State Legislature 

in 1989 (Fort Bend Subsidence District, 2020), the LSGCD 

and Bluebonnet Groundwater Conservation District were 

established by the 77th Texas State Legislature in 2001 (Lone 

Star Groundwater Conservation District, 2020; Bluebonnet 

Groundwater Conservation District, 2020), the BCGCD 

was established by the 78th Texas State Legislature in 2003 

(Brazoria County Groundwater Conservation District, 

2020), and the Lower Trinity Groundwater Conservation 

District was established by the 79th Texas State Legislature 

in 2005 (Lower Trinity Groundwater Conservation District, 

2020). Regulatory plans to gradually decrease groundwater 

withdrawals (in conjunction with increased usage of 

alternative surface-water supplies) are currently (2020) 

being phased in throughout most of the study area (fig. 

1). The current groundwater management plans of each 

district are available on their respective websites (Fort Bend 

Subsidence District, 2013; Harris-Galveston Subsidence 

District, 2013; Lone Star Groundwater Conservation District, 

2013; Brazoria County Groundwater Conservation District, 

2017; Bluebonnet Groundwater Conservation District, 2018; 

Lower Trinity Groundwater Conservation District, 2019). 

Groundwater withdrawals are currently (2020) not regulated 

by a groundwater conservation district in two counties in the 

Houston-Galveston region (Liberty and Chambers Counties; 

fig. 1).

Since the 1970s, the U.S. Geological Survey (USGS), in 

cooperation with the HGSD, has monitored groundwater-level 

altitudes and published reports on the status of groundwaterlevel altitudes and long-term groundwater-level changes in the 

Houston-Galveston region; following their establishment by 

the Texas State Legislature, the FBSD, LSGCD, and BCGCD 

became cooperative participants in the project as well. An 

extensive well-monitoring network was first established by 

the USGS in 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 Houston-Galveston 

region (Gabrysch, 1979). A comprehensive water-levelaltitude report for the Chicot and Evangeline aquifers was first 

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

USGS also first published a water-level-altitude map in 2001 

of the Jasper aquifer in the Houston-Galveston region (Coplin, 

2001). Additional information on the history of groundwaterlevel-altitude monitoring and of the USGS reports published 

to document groundwater-level altitudes and changes in 

groundwater-level altitudes in the Houston-Galveston region is 

provided in Kasmarek and Ramage (2017).

Purpose and Scope

The purpose of this report, prepared by the USGS 

in cooperation with the HGSD, City of Houston, FBSD, 

LSGCD, and BCGCD, is to depict groundwater-level altitudes 

and long-term groundwater-level changes in the Chicot, 

Evangeline, and Jasper aquifers in the Houston-Galveston 

region, Texas. An overview of the hydrogeology of the 

study area is provided, and regional-scale maps depicting 

approximate groundwater-level altitudes for 2020 (represented 

by measurements made during December 2019 through March 

2020) and long-term groundwater-level changes in the Chicot 

and Evangeline aquifers (1977–2020) and the Jasper aquifer 

(2000–20) are featured. Individual groundwater-level altitudes 

measured at each well for all three aquifers that were assessed 

(Chicot, Evangeline, and Jasper aquifers) and associated 

metadata are available for download in companion data 

releases (Ramage, 2020; Ramage and Braun, 2020).

Hydrogeology of the Study Area

The following overview of the hydrogeology of the study 

area is summarized from Kasmarek and Ramage (2017). The 

three primary aquifers in the Gulf Coast aquifer system in the 

Houston-Galveston region study area (the Chicot, Evangeline, 

and Jasper aquifers) are composed of laterally discontinuous 

deposits of gravel, sand, silt, and clay (Baker, 1979). The 

percentage of clay and other fine-grained, clastic material 

generally increases downdip (Baker, 1979). The uppermost 

aquifer, the Chicot aquifer, is contained in Holocene- and 

Pleistocene-age (Quaternary-age) sediments; the underlying 

Evangeline aquifer is contained in Pliocene- and Miocene-age 

sediments; and the most deeply buried of the three aquifers, 

the Jasper aquifer, is contained in Miocene-age sediments 

(fig. 2) (Baker, 1979, 1986). Hydrogeologic units in the 

study area include the Chicot aquifer, Evangeline aquifer, 

Burkeville confining unit, Jasper aquifer, and Catahoula 

confining system (fig. 3). The stratigraphic relations between 

these hydrogeologic units are shown on hydrogeologic 

cross section A–A ́ (figs. 1 and 2) of the Gulf Coast aquifer 

system, which extends through the Houston-Galveston region 

from northwestern Grimes County southeastward through 

Montgomery and Harris Counties before terminating at the 

coast in Galveston County. 

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); these sediments, which 

compose the Gulf Coast aquifer system, were deposited 

by fluvial-deltaic processes and subsequently were eroded 

and redeposited by worldwide episodic changes in sea level 

that occurred as a result of oscillations between glacial and 
4 Status of Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes, Houston-Galveston Region, Texas, 2020 Quaternary outcrop Tertiary outcrop

A

A'

10

1

2

3 4 5

6

7

8 9

11

WALLER COUNTY

GRIMES COUNTY

GALVESTON COUNTY

HARRIS COUNTY

MONTGOMERY COUNTY

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

SOHIO

No. 1 Kopperl

No. 1 Bradley

No. 1 Sealy

HUMBLE

EXETER

WELL NUMBERS ON LOCATION MAP

A A'

NORTHWEST SOUTHEAST

MONTGOMERY

COUNTY HARRIS COUNTY GALVESTON COUNTY GRIMES COUNTY

+400

−400

−800

−1,200

−1,600

−2,000

−2,400

−2,800

−3,200

−3,600

−4,000

−4,400

−4,800−5,200

−

−6,000

−6,400

−6,800

−7,200

−7,600

5,600

NAVD 88

FEET FEET

+400NAVD 88

−400

−800

−1,200

−1,600

−2,000

−2,400

−2,800

−3,200

−3,600

−4,000

−4,400

−4,800

−5,200

−5,600

−6,000

−6,400

−6,800−7,200

−7,600

3 4 5 6 7 8 9 10 11 1 2

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

16 MILES 12 8 4 0

16 KILOMETERS 12 8 4 0

Anahuac

Formation

Formation

Frio

Catahoula

Sandstone

Base of 

Catahoula 

Sandstone 

Catahoula 

confining 

system

Jasper

aquifer

Base of 

Fleming 

Formation

Burkeville

confining

unit

land surface Approximate

(upper part of Catahoula confining system)

(Holocene- and Pleistocene-age sediments)

(Pliocene- and Miocene-age sediments)

(Miocene-age sediments)

(Miocene-age sediments)

Undifferentiated early Oligocene- and pre-Oligocene-age deposits

(Oligocene- and Miocene-age sediments)

Chicot aquifer

Evangeline aquifer

Figure 2. Hydrogeologic cross section A–A ́ of the Gulf Coast aquifer system in Grimes, Montgomery, Harris, and Galveston Counties, Texas (modified from Baker, 1979, fig. 4).
Introduction 5

Erathem System

Geologic units

Hydrogeologic

units

(Baker, 1979)

Vicksburg

Formation

Alluvium

Beaumont

 Formation

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

Chicot

aquifer

Evangeline

 aquifer

Quaternary

Tertiary

Cenozoic

 Burkeville 

confining unit

Jasper 

aquifer

Catahoula 

confining 

 system

11,000

1.8 million

5.0 million

23 million

Holocene

Pliocene

Miocene

Pleistocene

Series

Early Oligocene- and pre-Oligocene-age sediments

Oligocene

2

Upper part

of Catahoula 

Sandstone

2

Anahuac 

Formation

1

Catahoula

 Sandstone

1

Located in the outcrop.

2

Located in the subcrop. 

 2

Frio Formation

Figure 3. 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).

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 

hydrogeologic units representing the aquifers and confining 

units thus crop out in bands inland from and approximately 

parallel to the coast and become progressively more deeply 

buried and confined toward the coast (fig. 2) (Kasmarek, 

2013). The aquifers receive recharge where the hydrogeologic 

units composing the aquifers crop out (Kasmarek and 

Robinson, 2004) (fig. 2). The Burkeville confining unit is 

stratigraphically positioned between the Evangeline and 

Jasper aquifers (fig. 2), thereby restricting groundwater 

flow between these two aquifers. There is no confining unit 

between the Chicot and Evangeline aquifers (fig. 2); therefore, 

these two aquifers are hydraulically connected, which allows 

groundwater flow between them. Because of this hydraulic 

connection, groundwater-level changes that occur in one 

aquifer can affect groundwater levels in the adjoining aquifer 

(Kasmarek and Robinson, 2004). Supporting evidence of 

the interaction of groundwater flow between the Chicot 

and Evangeline aquifers includes the differences between 

long-term groundwater-level-change maps, which indicate 

that the areas where water levels have risen or declined are 

approximately spatially coincident. Additional evidence of 

the hydraulic connection between the Chicot and Evangeline 

aquifers is provided by Borrok and Broussard (2016, p. 330); 

their geochemical evaluation of the Chicot aquifer system 

from 1993 to 2015 in Louisiana indicated that in some years 

(1998, 2008, and 2011) certain wells screened in the Chicot 

aquifer “appeared to be tapping water with a geochemistry 

(temperature, salinity, alkalinity, [and so forth]) matching the 

underlying Evangeline aquifer.” 
6 Status of Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes, Houston-Galveston Region, Texas, 2020

Hydraulic properties of the Chicot aquifer do not differ 

appreciably from those of 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 outcrop and updip limits of the geologic 

units that compose the Chicot aquifer are depicted in figure 1. 

Proceeding updip and inland of the Quaternary-age sediments 

containing the Chicot aquifer (fig. 2), the older geologic units 

(containing the Evangeline aquifer, the Burkeville confining 

unit, the Jasper aquifer, and the Catahoula confining system) 

sequentially outcrop (figs. 1 and 2). In the 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, 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 and 3).

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 toward the coast, 

reaching the intermediate and deep zones of the aquifers 

southeastward of the outcrop areas, 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 from the confined downdip 

areas of the aquifer system (Kasmarek and Robinson, 2004).

Previous Studies

An extensive well-monitoring network was established 

by 1977, and groundwater-level data were collected and 

used to create the first published groundwater-level-altitude 

maps of the Chicot and Evangeline aquifers in the HoustonGalveston region in 1979 (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 groundwater-levelaltitude report for the Chicot and Evangeline aquifers was 

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

and was revised in 1997 when updated well data became 

available (Kasmarek, 1997). Similarly, after the establishment 

of the LSGCD in 2001, the USGS began publishing 

groundwater-level-altitude maps of the Jasper aquifer in the 

Houston-Galveston region (primarily Montgomery County) 

(Coplin, 2001). In 2004, 2006, and 2007, as additional wells 

with reliable groundwater-level data were inventoried, revised 

groundwater-level-altitude maps for the Jasper aquifer were 

prepared (Kasmarek and Lanning-Rush, 2004; Kasmarek and 

others, 2006; Kasmarek and Houston, 2007). Since 2007, 

comprehensive maps for the Jasper aquifer have been included 

in the annual series of reports that depict groundwater-level 

altitudes and groundwater-level changes in the HoustonGalveston region (Kasmarek and Houston, 2008; Kasmarek 

and others, 2010, 2011, 2012, 2013, 2014, 2015, 2016; 

Johnson and others, 2011; Kasmarek and Ramage, 2017; Shah 

and others, 2018; Braun and others, 2019).

Methods

This section describes the methods used to (1) collect 

and process groundwater-level data used in this report, (2) 

determine groundwater-level altitudes, and (3) depict longterm groundwater-level changes in the study area. These 

methods are similar to those described in previous reports 

by Gabrysch (1979), Kasmarek and Houston (2007), and 

Kasmarek and Ramage (2017).

Groundwater-Level Measurements

Groundwater-level measurements were obtained from 

590 observation wells in the study area by USGS personnel 

during December 2019 through March 2020. The depth to 

water below land-surface datum was measured at each well to 

represent the 2020 groundwater-level altitudes of the Chicot, 

Evangeline, and Jasper aquifers (Ramage, 2020). These 

590 measurements were made by using a calibrated steel 

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

methods described in Cunningham and Schalk (2011). Each 

well was measured during the December 2019 through March 

2020 time period to provide a “snapshot” of groundwater-level 

altitudes in the aquifers associated with individual wells.

In 2020, 20 additional measurements representing 

about 3 percent of the total number of groundwater-level 

measurements were furnished by industrial entities and 

powerplants operating within the study area that use water 

for hydrocarbon processing and electrical power generation, 

respectively. The furnished water levels were typically 

measured by using air pressure to determine the saturated 

thickness above the pump intake, and multiple pressure 

measurements were usually collected as a quality-control 

measure. Air pressure measurements tend to provide less 

precision than do measurements made with either a steel 

tape or electric tape; therefore, all furnished measurements 

were rounded to the nearest foot. Water levels that were 

furnished by industrial entities or powerplants are identified 

as such in the “source” field in Ramage (2020); additional 

information about these wells can be obtained from the USGS 

National Water Information System (NWIS) (U.S. Geological 

Survey, 2020a).
Methods 7

One additional well located in a part of Galveston Bay 

that is critical for the delineation of Chicot aquifer contours 

in Galveston and Trinity Bays could not be measured 

because of new safety concerns outlined by staff members 

who had measured the well in previous years. Engineering 

controls were identified that could reduce the risk associated 

with measuring groundwater levels at this location but 

implementing these controls could not be accomplished 

within the designated project timeline for 2020. As a result, 

a median value from the prior 11 years of groundwater-level 

measurements was used to represent the 2020 groundwaterlevel measurement at this well (U.S. Geological Survey, 

2020a [station name DH-64-26-701; USGS site number 

293156094515501]) because this well is located in an area 

otherwise devoid of network wells (along the southeastern 

boundary of the contoured areas represented in figs. 4 and 5) 

that are measured in conjunction with this report. Therefore, 

the exclusion of this well could have had substantial effects 

on contours associated with both the 2020 groundwaterlevel altitudes (fig. 4) and the 1977–2020 groundwater-level 

changes (fig. 5) in the Chicot aquifer. The standard deviation 

for the 11 years of water-level measurement data used to 

calculate the median water-level measurement that was used 

for this well was 2.3 ft, so the relative stability of water-level 

measurements over this span seemed to justify the course of 

action that led to the inclusion of this well.

Most of the measured wells were being pumped at 

least once daily and some more frequently during the study 

period. Therefore, well pumps were turned off for at least 

1 hour before the groundwater-level measurements were 

made in order to obtain a groundwater-level measurement 

that approximated the static conditions within the aquifer. 

Antecedent withdrawal rates and pumping status of nearby 

wells were not always known and, in such instances, could 

have affected the representativeness of the groundwaterlevel data that were collected. To ensure that the recorded 

groundwater-level measurement was accurate, at least two 

groundwater-level measurements were made at each well 

while the well was not being pumped. After the groundwaterlevel-measurement data were collected, they were thoroughly 

evaluated and incorporated into a geographic information 

system (GIS) as point-data layers and subsequently used 

for the construction of groundwater-level-altitude and 

groundwater-level-change maps. The groundwater-level 

measurements collected or provided for this study were 

carefully reviewed by USGS personnel and were compiled 

in Ramage (2020). All collected and compiled water-level 

measurements were also loaded into NWIS (U.S. Geological 

Survey, 2020a). 

Determination of Groundwater-Level Altitudes

The 2020 regional-scale depictions of groundwaterlevel altitudes presented in this report were derived from 

groundwater-level-measurement data collected throughout 

the 11-county study area from December 2019 through 

March 2020 (water levels usually are higher because 

groundwater use is at its lowest during these months compared 

to the rest of the year). Groundwater-level altitudes were 

calculated by subtracting the groundwater-level measurement 

from the land-surface elevation at each well referenced 

to datum (National Ocean Service, 2020). Prior to 2016, 

groundwater-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 accuracy of land-surface-elevation data at wells 

used in the annual series of reports has gradually improved 

over time as digital elevation models (DEMs) progressively 

replaced traditional methods of determining land-surface 

elevations from topographic maps. The most accurate landsurface data available were used by the USGS for each 

historical annual depiction of groundwater-level altitudes in 

the study area. To determine land-surface elevations in 2020, a 

corresponding land-surface datum was obtained for each well 

by using a USGS National Geospatial Program 1-meter DEM 

that provides three-dimensional elevation values referenced 

to datum (Arundel and others, 2015; U.S. Geological Survey, 

2020b). The height above land surface of the measuring point 

at each well was measured with an engineering ruler. In 1977, 

land-surface-elevation data were calculated from USGS 

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

the Gulf of Mexico coastal area, which have a 5-ft contour as 

described in Gabrysch (1979), thereby providing an accuracy 

of 2.5 ft. The DEM used to determine land-surface elevation in 

2020 provides an accuracy of 0.5 ft. 

The 2020 groundwater-level altitudes measured in wells 

completed in the Chicot, Evangeline, and Jasper aquifers 

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

The groundwater-level-altitude contours are approximate, 

regional-scale 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.

Depicting Long-Term Groundwater-Level 

Changes

Maps depicting changes in groundwater-level altitudes 

in the Chicot, Evangeline, and Jasper aquifers were 

constructed for the period of record available for each of 

the aquifers; data are from 1977 to 2020 for the Chicot and 

Evangeline aquifers and from 2000 to 2020 for the Jasper 

aquifer. Groundwater-level-change maps were constructed by 

contouring the set of mapped point values, computed either 

as the difference in groundwater-level altitude at each well for 

which a groundwater-level measurement was made in 2020 

and in the historical year (1977 or 2000) or as the difference 

in the groundwater-level altitude at that point in 2020 and 

the groundwater-level altitude on a gridded surface of the 

historical year groundwater-level-altitude map (Gabrysch, 

1979; Kasmarek and Houston, 2007). Gridded-surface values 
8 Status of Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes, Houston-Galveston Region, Texas, 2020

(rather than actual measured values) for the historical year 

were only used to compute differences (mapped point values) 

if the wells measured in 2020 did not exist in 1977 (for the 

Chicot and Evangeline aquifers) or 2000 (for the Jasper 

aquifer). The datasets of groundwater-level-change values 

(difference between 2020 and historical year groundwaterlevel-altitude values) are available in Ramage (2020) and 

Ramage and Braun (2020).

Groundwater-Level Altitudes and LongTerm Groundwater-Level Changes

Groundwater-level-altitude and long-term groundwaterlevel-change maps were constructed for the Chicot, 

Evangeline, and Jasper aquifers in the study area (figs. 4–9). 

Whereas the aquifer maps in this report depict approximate 

groundwater-level altitudes for 2020 by using 50-ft contour 

intervals (figs. 4, 6, and 8), 20-ft contour intervals were 

used to depict groundwater-level changes for 1977–2020 

in the Chicot aquifer (fig. 5), 40-ft contour intervals were 

used for 1977–2020 in the Evangeline aquifer (fig. 7), and 

20-ft contour intervals were used for 2000–20 in the Jasper 

aquifer (fig. 9). All long-term groundwater-level changes in 

this report are considered approximate. Locations of wells 

used to construct the 2020 groundwater-level-altitude maps 

for the Chicot, Evangeline, and Jasper aquifers are presented 

in Ramage (2020) and Ramage and Braun (2020). Certain 

groundwater-level-altitude measurements collected during 

December 2019 through March 2020 were not used to 

construct the contour maps presented in this report for the 

Chicot, Evangeline, and Jasper aquifers because they were 

not consistent with water-level altitudes obtained from other 

wells screened in the same aquifer and located nearby for one 

or more of the following reasons: (1) the well in question was 

screened in a shallower part of the aquifer or with a smaller 

depth interval that provided poor communication between 

the well and surrounding aquifer; (2) the well in question had 

been pumped recently and the water-level altitude at this well 

was still rising; and (3) the well in question is near one or 

more other wells with water-level altitudes that more closely 

match those of the regional water table, such that retaining the 

water-level altitude from the well in question would result in a 

localized “bullseye” contour or otherwise unrealistic-looking 

contour pattern. The companion data release by Ramage and 

Braun (2020) identifies the water-level-altitude measurements 

that were used to construct the contour maps for each aquifer.

Chicot Aquifer

Groundwater-level-measurement data from 173 wells 

(Ramage and Braun, 2020) were used to depict the 2020 

groundwater-level-altitude contours for the Chicot aquifer 

(fig. 4). In 2020, groundwater-level-altitude contours for the 

Chicot aquifer ranged from 150 ft below datum in a relatively 

small area (less than 8 square miles) in northwestern Harris 

County near Jersey Village to 200 ft above datum west of 

Conroe in southern Montgomery County. 

The largest decline in groundwater-level altitudes (120 ft) 

indicated by the 1977–2020 groundwater-level-change 

contours for the Chicot aquifer was also in northwestern 

Harris County near Jersey Village (fig. 5). The largest rise in 

groundwater-level altitudes in the Chicot aquifer from 1977 to 

2020 (200 ft) was in southeastern Harris County between Deer 

Park and Baytown (fig. 5).

Evangeline Aquifer

Groundwater-level-measurement data from 326 

wells (Ramage and Braun, 2020) were used to depict the 

approximate 2020 groundwater-level-altitude contours for 

the Evangeline aquifer (fig. 6). In 2020, groundwater-levelaltitude contours for the Evangeline aquifer ranged from 

250 ft below datum at two locations south of Jersey Village in 

western Harris County and two locations near The Woodlands 

and Spring in northern Harris and southern Montgomery 

Counties, respectively, to 200 ft above datum along a contour 

line that extends northeast from near Todd Mission (in the 

southeastern part of Grimes County) through Montgomery and 

Willis (both in Montgomery County). 

The 1977–2020 groundwater-level-change contours 

for the Evangeline aquifer (fig. 7) depict broad areas 

where groundwater-level altitudes either declined or rose. 

The largest decline in groundwater-level altitudes in the 

Evangeline aquifer from 1977 to 2020 (280 ft) was in 

southern Montgomery and northern Harris Counties, near 

The Woodlands (fig. 7). The largest rise in groundwater-level 

altitudes in the Evangeline aquifer from 1977 to 2020 (240 ft) 

was in southeastern Harris County along Buffalo Bayou near 

Galena Park (fig. 7).

Jasper Aquifer

Groundwater-level-measurement data from 112 wells 

(Ramage and Braun, 2020) were used to depict the 

approximate 2020 groundwater-level-altitude contours for the 

Jasper aquifer (fig. 8). In 2020, groundwater-level-altitude 

contours for the Jasper aquifer ranged from 200 ft below 

datum at two locations near The Woodlands in northern Harris 

and southern Montgomery Counties to 250 ft above datum in 

eastern Grimes County, northwestern Montgomery County, 

and southwestern Walker County (fig. 8). 

Whereas annual groundwater-level-altitude data have 

been collected since 1977 from wells completed in the 

Chicot and Evangeline aquifers, annual groundwater-levelaltitude data have been collected from wells completed in the 

Jasper aquifer since only 2000. The 2000–20 groundwaterlevel-change contours for the Jasper aquifer (fig. 9) depict 

groundwater-level declines throughout most of the study area 

where groundwater-level-altitude data from the Jasper aquifer 

were collected, with the largest decline (220 ft) in southern 

Montgomery County between Spring and The Woodlands.
Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes 9

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

50

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 2019 through March 2020 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

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

Universal Transverse Mercator projection, Zone 15

North American Datum of 1983

FM 521

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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

Deer Park

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

BRAZOS

COUNTY

WHARTON COUNTY

HARRIS

COUNTY

95°45'

95°45'

95°30'

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95°

30°30'

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30°

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94°30'

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Study area

TEXAS

50

-50

150

100

-50

0

200

-100

0

-50

-100

-150

Todd Mission

laf20-1001_fig 04

Figure 4. Approximate 2020 groundwater-level altitudes and updip limit of the Chicot aquifer, Houston-Galveston region, Texas 

(water-level-measurement data collected during December 2019 through March 2020).
10 Status of Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes, Houston-Galveston Region, Texas, 2020

FM 521

FM 787

FM 2004

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FM 1960

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FM 35

150 FM 1375

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36

105

90 59

290

59

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610

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Grand Pky

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N Sam Houston Pky W

S Sam Houston Pky E

E North Belt

Addicks Satsuma Rd

S Belt

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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

Boundary of study area

Updip limit of Chicot aquifer (University of Texas, 

 Bureau of Economic Geology, 1968; 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 2020 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 2020. 

Conversely, some of the wells measured in 2020 

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 2020 and 

1977. For the subset of wells measured in 

both 2020 and 1977, the mapped point 

values used were the differences in 

water-level-altitude values between 

2020 and 1977 rather than the 

differences between 2020 

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.

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

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

Deer Park

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

WHARTON COUNTY

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Study area

TEXAS

laf20-1001_fig 05

Todd Mission

Figure 5. Approximate 1977–2020 groundwater-level changes in the Chicot aquifer, Houston-Galveston region, Texas.
Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes 11

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

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168

30

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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

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

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

Deer Park

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

WHARTON COUNTY

HARRIS

COUNTY

BRAZOS

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'

Study area

TEXAS

50

150

100

200

-150

0

-150

50

150

100

0

-150

-50

-100

-150

-100

0

-150

-50

-200

-250

-150

-200

-200

-200

-150

-150

-100

-250 -200 -200

-200

-150

50

-50-100

-150

-200

-250

100

0

-50

-100

-200

-250

0

50

-50 -100

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

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 2019 through March 2020 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.

laf20-1001_fig 06

Todd Mission

Figure 6. Approximate 2020 groundwater-level altitudes and updip limit of the Evangeline aquifer, Houston-Galveston region, Texas 

(groundwater-level-measurement data collected during December 2019 through March 2020).
12 Status of Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes, Houston-Galveston Region, Texas, 2020

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

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

Deer Park

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

WHARTON COUNTY

HARRIS

COUNTY

BRAZOS

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'

Study area

TEXAS

0

-120

-160

0

0

120

40

120

-40

80

200

240

160

120

120

80

-80

-120

-160

-40

-200

-80 -240

-280

-80

40

-120

-160

0

0

-40

-120

-160

-80

-200

-160

0 0

40

-80

-40

-80

-120

EXPLANATION

Boundary of study area

Updip limit of Evangeline aquifer (Baker, 1979)

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

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 2020 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 2020. 

Conversely, some of the wells measured in 

2020 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 

2020 and 1977. For the subset of wells 

measured in both 2020 and 1977, the 

mapped point values used were the 

differences in water-level-altitude 

values between 2020 and 1977 

rather than the differences 

between 2020 water-levelaltitude values and 1977 

gridded-surface values. The 

area of water-level change 

shown is based on 

availability of water-level 

data from 1977.

Todd Mission

laf20-1001_fig 07

Figure 7. Approximate 1977–2020 groundwater-level changes in the Evangeline aquifer, Houston-Galveston region, Texas.
Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes 13

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

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

Deer Park

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

WHARTON COUNTY

HARRIS

COUNTY

BRAZOS

COUNTY

Todd Mission

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'

Study area

TEXAS

50

-50

100

200

-100

0

100

-200

250

100

-200

-200

150

-150

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 

2019 through March 2020 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.

laf20-1001_fig 08

Figure 8. Approximate 2020 groundwater-level altitudes and updip limit of the Jasper aquifer, Houston-Galveston region, Texas 

(groundwater-level-measurement data collected during December 2019 through March 2020).
14 Status of Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes, Houston-Galveston Region, Texas, 2020

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

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

Deer Park

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

WHARTON COUNTY

HARRIS

COUNTY

BRAZOS

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'

Study area

TEXAS

Todd Mission

-20

0

-60

-40

-80

-40

-100

-140

-80

-120 -180

-200

-140

-120

-100

-160

-80

-40

-40

-60

-220 -160

-160

-120

-100

20

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 2020 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 2020. Conversely, some of the 

wells measured in 2020 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 2020 and 2000. For the 

subset of wells measured in both 2020 

and 2000, the mapped point values 

used were the differences in 

water-level-altitude values 

between 2020 and 2000

rather than the differences 

between 2020 water-level 

altitude values and 2000

gridded-surface values. The 

area of water-level change 

shown is based on 

availability of water-level 

data from 2000.

Updip limit of Jasper aquifer (University of Texas,

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

Boundary of study area

0

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

20

EXPLANATION

Line of zero water-level change

Line of equal water-level rise—Interval 20 feet

laf20-1001_fig 09

Figure 9. Approximate 2000–20 groundwater-level changes in the Jasper aquifer, Houston-Galveston region, Texas.
References Cited 15

Data Limitations

As described in the “Methods” section, the accuracy of 

the land-surface-elevation data has gradually improved over 

time. Any changes in land-surface elevation could affect the 

accuracy of groundwater-level-change maps depicting the 

differences between the current year (2020) and the historical 

year (1977 or 2000) altitudes (Kasmarek and Ramage, 2017). 

The depictions of groundwater-level altitudes and 

changes at any specific location are considered to represent a 

regional-scale approximation and, as such, are not intended 

for use in engineering or other design applications. The 

groundwater-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. Users should exercise 

discretion when drawing conclusions or making policy 

decisions based on these contoured depictions.

Summary

The Houston-Galveston region, Texas, consists of Harris, 

Galveston, Fort Bend, Montgomery, Brazoria, Chambers, 

Grimes, Liberty, San Jacinto, Walker, and Waller Counties. 

Groundwater withdrawn from the three primary aquifers 

that compose the Gulf Coast aquifer system—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. 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 the status of groundwater-level altitudes 

and long-term groundwater-level changes in the Chicot, 

Evangeline, and Jasper aquifers in the Houston-Galveston 

region. Water levels in wells screened in these aquifers were 

measured during December 2019 through March 2020 (water 

levels usually are higher during these months compared to the 

rest of the year).

This report contains regional-scale maps depicting 

approximate 2020 groundwater-level altitudes and longterm groundwater-level changes in the Chicot, Evangeline, 

and Jasper aquifers. Groundwater-level measurements from 

173, 326, and 112 wells were used to depict the approximate 

2020 groundwater-level-altitude contours for the Chicot, 

Evangeline, and Jasper aquifers, respectively. 

In 2020, groundwater-level-altitude contours for the 

Chicot aquifer ranged from 150 feet (ft) below the North 

American Vertical Datum of 1988 (hereinafter referred 

to as “datum”) to 200 ft above datum. The 1977–2020 

groundwater-level-change contours for the Chicot aquifer 

depict a large area of decline in groundwater-level altitudes 

(120 ft) in northwestern Harris County north of Jersey Village. 

The largest rise in groundwater-level altitudes in the Chicot 

aquifer from 1977 to 2020 (200 ft) was in southeastern Harris 

County between Deer Park and Baytown. 

In 2020, groundwater-level-altitude contours for the 

Evangeline aquifer ranged from 250 ft below datum to 

200 ft above datum. The 1977–2020 groundwater-levelchange contours for the Evangeline aquifer depict broad 

areas where groundwater-level altitudes either declined or 

rose. The largest decline in groundwater-level altitudes in 

the Evangeline aquifer from 1977 to 2020 (280 ft) was in 

southern Montgomery and northern Harris Counties, near The 

Woodlands. The largest rise in groundwater-level altitudes 

in the Evangeline aquifer from 1977 to 2020 (240 ft) was 

in southeastern Harris County along Buffalo Bayou near 

Galena Park.

In 2020, groundwater-level-altitude contours for the 

Jasper aquifer ranged from 200 ft below datum to 250 ft above 

datum. Whereas annual groundwater-level-altitude data have 

been collected since 1977 from wells completed in the Chicot 

and Evangeline aquifers, annual groundwater-level-altitude 

data have been collected from wells completed in the Jasper 

aquifer since only 2000. The 2000–20 groundwater-levelchange contours for the Jasper aquifer depict groundwaterlevel declines throughout most of the study area where 

groundwater-level-altitude data from the Jasper aquifer 

were collected, with the largest decline (220 ft) in southern 

Montgomery County.

References Cited

Arundel, S.T., Archuleta, C.M., Phillips, L.A., Roche, B.L., 

and Constance, E.W., 2015, 1-meter digital elevation 

model specification: U.S. Geological Survey Techniques 

and Methods, book 11, chap. B7, 25 p. with appendixes, 

accessed July 16, 2018, at https://doi.org/10.3133/tm11B7.

Baker, E.T., Jr., 1979, Stratigraphic and hydrogeologic 

framework of part of the Coastal Plain of Texas: Texas 

Department of Water Resources Report 236, 43 p.

Baker, E.T., Jr., 1986, Hydrology of the Jasper aquifer in the 

southeast Texas Coastal Plain: Texas Water Development 

Board Report 295, 64 p.

Barbie, D.L., Coplin, L.S., and Locke, G.L., 1991, 

Approximate altitude of water levels in wells in the Chicot 

and Evangeline aquifers in the Houston area, Texas, 

January–February 1990: U.S. Geological Survey Open-File 

Report 91–240, 2 sheets, accessed April 28, 2020, at https://

doi.org/10.3133/ofr91240.
16 Status of Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes, Houston-Galveston Region, Texas, 2020

Bluebonnet Groundwater Conservation District, 2018, 

Bluebonnet Groundwater Conservation District 

groundwater management plan: Bluebonnet Groundwater 

Conservation District, 178 p., accessed on April 13, 2020, 

at http://www.bluebonnetgroundwater.org/wp-content/

uploads/2019/10/ADOPTED-MGMT-Plan-10-108-v2.pdf.

Bluebonnet Groundwater Conservation District, 2020, History: 

Bluebonnet Groundwater Conservation District, accessed 

April 13, 2020, at http://www.bluebonnetgroundwater.org/

district/history/.

Borrok, D.M., and Broussard, W.P., III, 2016, Long-term 

geochemical evaluation of the coastal Chicot aquifer 

system, Louisiana, USA: Journal of Hydrology, v. 

533, p. 320–331, accessed August 23, 2019, at https://

doi.org/10.1016/j.jhydrol.2015.12.022.

Braun, C.L., Ramage, J.K., and Shah, S.D., 2019, Status of 

groundwater-level altitudes and long-term groundwaterlevel changes in the Chicot, Evangeline, and Jasper aquifers, 

Houston-Galveston region, Texas, 2019: U.S. Geological 

Survey Scientific Investigations Report 2019–5089, 18 

p., accessed April 28, 2020, at https://doi.org/10.3133/

sir20195089.

Brazoria County Groundwater Conservation District, 

2017, Brazoria County Groundwater Conservation 

District groundwater management plan: Brazoria County 

Groundwater Conservation District, 130 p., accessed April 

13, 2020, at https://www.bcgroundwater.org/images/bcg/

documents/2017/Groundwater-Management-Plan-2017.pdf.

Brazoria County Groundwater Conservation District, 

2020, About the district: Brazoria County Groundwater 

Conservation District, accessed April 13, 2020, at https://

www.bcgroundwater.org/bcg/About_the_District.asp.

Carr, J.E., Meyer, W.R., Sandeen, W.M., and McLane, I.R., 

1985, Digital models for simulation of ground-water 

hydrology of the Chicot and Evangeline aquifers along the 

Gulf Coast of Texas: Texas Department of Water Resources 

Report 289, 101 p.

Chowdhury, A.H., and Turco, M.J., 2006, Geology of the Gulf 

Coast aquifer, Texas, chap. 2 of Mace, R.E., Davidson, 

S.C., Angle, E.S., and Mullican, W.F., eds., Aquifers of 

the Gulf Coast of Texas: Texas Water Development Board 

Report 365, p. 23–50.

Coplin, L.S., 2001, Water-level altitudes in wells completed 

in the Jasper aquifer, greater Houston area, Texas, spring 

2000: U.S. Geological Survey Open-File Report 01–147, 

2 p., accessed April 28, 2020, at https://doi.org/10.3133/

ofr01147.

Coplin, L.S., and Galloway, D., 1999, Houston-Galveston, 

Texas—Managing coastal subsidence, in Galloway, D., 

Jones, D.R., and Ingebritsen, S.E., eds., Land subsidence in 

the United States: U.S. Geological Survey Circular 1182, p. 

35–48, accessed April 28, 2020, at https://doi.org/10.3133/

cir1182.

Cunningham, W.L., and Schalk, C.W., comps., 2011, 

Groundwater technical procedures of the U.S. Geological 

Survey: U.S. Geological Survey Techniques and 

Methods 1– A1, 151 p., accessed April 28, 2020, at https://

doi.org/10.3133/tm1A1.

Fort Bend Subsidence District, 2013, Fort Bend Subsidence 

District 2013 regulatory plan [amended 2007, 2009, and 

2013]: Fort Bend Subsidence District, 14 p., accessed April 

13, 2020, at http://fortbendsubsidence.org/wp-content/

uploads/2016/09/FBSD-Regulatory-Plan-20130828.pdf.

Fort Bend Subsidence District, 2020, About the district: Fort 

Bend Subsidence District, accessed April 13, 2020, at 

https://fortbendsubsidence.org/about-the-district/.

Gabrysch, R.K., 1979, Approximate altitude of water levels in 

wells in the Chicot and Evangeline aquifers in the Houston 

area, Texas, spring 1977 and spring 1978: U.S. Geological 

Survey Open-File Report 79–334, 4 sheets, accessed 

April 28, 2020, at https://doi.org/10.3133/ofr79334.

Harris-Galveston Subsidence District, 2013, Regulatory plan 

2013: Harris-Galveston Subsidence District, 14 p., accessed 

April 13, 2020, at http://hgsubsidence.org/wp-content/

uploads/2013/07/HGSD-2013-Regulatory-Plan-withAmendment.pdf.

Harris-Galveston Subsidence District, 2020, Legislative 

authority: Harris-Galveston Subsidence District, accessed 

April 13, 2020, at https://hgsubsidence.org/about/

legislative-authority/.

Johnson, M.R., Ramage, J.K., and Kasmarek, M.C., 2011, 

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For more information about this publication, contact

Director, Oklahoma-Texas Water Science Center

U.S. Geological Survey

1505 Ferguson Lane

Austin, TX 78754–4501

For additional information visit https://www.usgs.gov/centers/tx-water.

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Braun and Ramage—Status of Groundwater-Level Altitudes and Long-Term Groundwater-Level Changes, Houston-Galveston Region, Texas, 2020—SIR 2020–5089

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20205089