U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2013–3024

May 2013

Prepared in cooperation with the Middle Pecos Groundwater Conservation District, Pecos County, City of Fort Stockton, 

Brewster County, and Pecos County Water Control and Improvement District No. 1

A Conceptual Hydrogeologic Model 

for the Hydrogeologic Framework, Geochemistry, and Groundwater-Flow System of the 

Edwards-Trinity and Related Aquifers in the Pecos County Region, Texas

Printed on recycled paper

Three-dimensional representation of the 

conceptual model output.

Davis

Mountains

Barilla

Mountains

Glass

Mountains

Grandfalls

Pecos River Pecos River

PECOS

COUNTY 

BREWSTER

COUNTY 

PRESIDIO

COUNTY 

REEVES

COUNTY 

TERRELL COUNTY 

CROCKETT

 COUNTY 

JEFF DAVIS

COUNTY 

UPTON COUNTY 

WARD

COUNTY CRANE

COUNTY 

285

10

20

10

285

Balmorhea

Toyahvale

Alpine

Fort

Davis

Belding Fort Stockton

Pecos

Base modified from U.S. Geological Survey digital data, 1:2,000,000 

Albers Equal Area projection, Texas State Mapping System

North American Datum of 1983 

Aquifer modified from Ashworth and Hopkins, 1995

Physiographic provinces from N.M. Fenneman and D.W. Johnson, 1946;

 E.G. Wermund, 1996; Lithologic and geophysical data from

 Daniel B. Stephens and Associates, 2010; Meyer and others, 2011;

 Texas Water Development Board, 2011; Railroad Commission of

Texas, 2010; University Lands, 2011; and U.S. Geological Survey, 2011

San

Solomon

Spring

Santa Rosa

Spring

Leon Springs

Comanche

Springs

Diamond Y

 Spring

7

7 7

7

7

0

100

10 20 MILES

20 KILOMETERS

104°00’ 103°30’ 102°30’

31°00’

30°30’

103°00’

HIGH PLAINS

MEXICAN

HIGHLAND

PECOS VALLEY EDWARDS (STOCKTON) PLATEAU

BASIN AND RANGE PROVINCE

GREAT PLAINS PROVINCE

BALMORHEA

STATE PARK

EXPLANATION

Method of hydrostratigraphic picks

 Pick reviewed from lithological descriptions in well reports

 Pick made from interpreted borehole geophysical log

 Pick made from interpreted geophysical audio-magnetotelluric

 sounding

Spring

Edwards-Trinity aquifer outcrop

Edwards-Trinity aquifer subcrop

Study area boundary

Leon-Belding area boundary

Section boundary within physiographic

 province 7

TEXAS

TRANSPECOS

REGION Study area

Pecos County

region

Pecos

River

Location of study area and hydrostratigraphic data used to identify tops and bases (picks) 

of the hydrostratigraphic contacts in the Pecos County region, Texas.

The Edwards-Trinity aquifer is a vital groundwater resource for agricultural, industrial, and municipal uses in the Trans-Pecos region of 

west Texas. A conceptual model of the hydrogeologic framework, geochemistry, and groundwater-flow system in the 4,700 square-mile (mi2

) 

study area was developed by the U.S. Geological Survey (USGS) in cooperation with the Middle Pecos Groundwater Conservation District, 

Pecos County, City of Fort Stockton, 

Brewster County, and Pecos County Water 

Control and Improvement District No. 1. 

The model was developed to gain a better 

understanding of the groundwater system 

and to establish a scientific foundation for 

resource-management decisions. Data and 

information were collected or obtained 

from various sources to develop the model. 

Lithologic information obtained from 

well reports and geophysical data were 

used to describe the hydrostratigraphy 

and structural features of the groundwater 

system, and aquifer-test data were used 

to estimate aquifer hydraulic properties. 

Groundwater-quality data were used to 

evaluate groundwater-flow paths, water and 

rock interaction, aquifer interaction, and 

the mixing of water from different sources. 

Groundwater-level data also were used 

to evaluate aquifer interaction as well as 

to develop a potentiometric-surface map, 

delineate regional groundwater divides, and 

describe regional groundwater-flow paths. 

Several previous studies have been 

done to compile or collect physical and 

chemical data, describe the hydrogeologic 

processes, and develop conceptual and 

numerical groundwater-flow models of 

the Edwards-Trinity aquifer in the TransPecos region. Documented methods were 

used to compile and collect groundwater, 

surface-water, geochemical, geophysical, 

and geologic information that subsequently 

were used to develop this conceptual 

model. 
100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

1,400

1,500

1,600

1,700

Cretaceous P ermian

Comamche Ochoa Guadalupe

Fredericksburg Trinity Whitehorse

Salado Yates Seven Rivers Queen Grayburg

Triassic

Tansill Edwards Trinity Sands

Limestone

Shale

Sandstone

Dolomitic 

anhydrite

 Salt and 

anhydrite

Sandstone 

 Anhydritic

 dolomite

Sandstone

 and shale

Anhydrite

Dolomitic

 shale

Dolomite

Sandstone 

 and shale Dockum

Rustler

Dewey Lake

Dolomitic

 shale

Glass

Mountains

Davis

Mountains

Barilla

Mountains

Pecos River

FB01

FB02

FB03 FB04 FB05

FB06

FB09 FB08

FB10

FB07

285

10

20

10

285

A

A'

B'

B

31°00'

30°30'

102°00'

103°00'

104°00'

102°30' 103°30'

Base modified from U.S. Geological Survey digital data, 1:2,000,000

Albers Equal Area projection, Texas State Mapping System

North American Datum of 1983

0 20 MILES 10

0 20 KILOMETERS 10

EXPLANATION

Edwards-Trinity aquifer 

 subcrop

Edwards-Trinity aquifer 

 outcrop

Study area boundary

Fault zones

Line of section

Fault block identifier 

A'A

FB01

Fault Interpretation

Faults in the study area likely formed as growth and 

collapse features as sediments were deposited along the margins

of more resistant rocks and structures, such as the Glass 

Mountains, and as sediments collapsed into the voids created 

by the dissolution of Permian-age evaporite deposits. Fault zones 

were delineated based on the interpretation of cross sections of 

the interpolated top and base surfaces of the Edwards-Trinity 

aquifer units and are similar to faults delineated previously 

for the underlying Rustler aquifer (INTERRA Incorporated, 2011). 

Each fault zone represents a series of parallel and transverse faults 

that result in an overall displacement between two adjacent fault 

blocks.

Hydrogeologic Framework

Hydrostratigraphy

Well reports, borehole geophysical logs, and surface geophysical soundings were evaluated to determine the lithologies, 

hydrostratigraphic units, and the tops and bases of the hydrostratigraphic units (commonly referred to as the “hydrostratigraphic picks”). The 

resulting datasets were used to characterize vertical and lateral hydrostratigraphic extents. More than 2,000 data records for wells in or near 

the study area were obtained from various sources and evaluated for applicability to the study. A total of 662 records were found to contain 

pertinent data of applicable vertical extent within the study area. Stratigraphic and lithologic descriptions and borehole geophysical logs were 

obtained from existing reports and were assessed and interpreted to identify the vertical extents of hydrostratigraphic units. After the existing 

data were compiled, a geospatial analysis was done to identify data gaps and areas of concern. To enhance compiled data and fill in data gaps, 

where possible, 44 additional borehole geophysical logs, 4 time-domain electromagnetic (TDEM) soundings, and 13 audio-magnetotelluric 

(AMT) soundings were collected at the site. Three-dimensional surfaces were interpolated to represent the tops and bases of applicable 

hydrostratigraphic units. These three-dimensional surfaces were then used to assess all hydrostratigraphic contacts and refine contacts as 

needed.

Borehole Geophysics

Borehole geophysical data such as natural gamma, formation 

resistivity, and caliper are commonly used to identify and 

characterize stratigraphic units; these data exist for many wells 

in the study area and were collected during previous scientific 

investigations and petroleum explorations. A total of 230 borehole 

geophysical logs—28 from University Lands (2011), 23 from 

USGS, 51 from the Railroad Commission of Texas, and 128 from 

Texas Water Development Board (Meyer and others, 2011)—were 

identified to contain relevant data for the project and were used to 

generate hydrostratigraphic contacts. U.S. Geological Survey borehole geophysical logging truck.

Time-domain electromagnetic surface geophysical sounding 

collection.

Surface Geophysics

Of the TDEM and AMT soundings collected in the study area, 

all of the TDEM soundings and four of the AMT soundings were 

near wells from which borehole geophysical logs were collected 

by the USGS. These locations were used to verify results between 

well data and surface geophysical soundings. Hydrostratigraphic 

contacts (picks) from surface soundings were used to supplement 

and enhance the compiled data set. Surface geophysical inverse 

modeling results were interpreted with layered-earth electrical 

scenarios in which each layer represents a separate electrical layer. 

These electrical layers then were associated with geologic layers. 

The layered-earth electrical scenarios for the AMT soundings were 

interpreted based on electrical changes in the modeling results.

Stratigraphic Surface Construction

After the geophysical logs and soundings were compiled and interpreted and the tops and bases of hydrostratigraphic units (picks) were 

determined, grids were created for each surface using kriging interpolation techniques. Modeling software was used to create the threedimensional hydrostratigraphic surfaces. Preliminary grids were then used to identify outliers and areas requiring review. Throughout the 

process, the identified tops and bases of hydrostratigraphic units were reviewed and revised as needed to better conform to the available data.

Location of fault zones and fault blocks within the study area 

delineated based on the interpretation of multiple cross 

sections of interpolated hydrostratigraphic contacts.
Hydrostratigraphic Layers

Cross Sections

Base of the Edwards-Trinity Aquifer

The spatial trends observed for the base surface of the 

Edwards-Trinity aquifer were similar to those observed for the top 

of the Edwards-Trinity aquifer. The highest altitude of the base 

of the Edwards-Trinity aquifer was in the southern part of the 

study area near the Glass Mountains (about 4,110 feet). Similar to 

the top of the Edwards-Trinity aquifer, the altitude of the base of 

the Edwards-Trinity aquifer decreased to the northeast, which is 

consistent with findings by Barker and Ardis (1992). The lowest 

altitude for the base of the Edwards-Trinity aquifer was in the 

north-central part of the study area in the Monument Draw trough 

(about 1,550 feet).

Top of the Edwards-Trinity Aquifer

The altitude of the top of the Edwards-Trinity aquifer, 

which is, in general, the top of the Edwards part of the aquifer 

(upper Cretaceous), closely matched those of the land-surface 

altitudes throughout most of the study area. The altitude of the 

top surface of the Edwards-Trinity aquifer was highest in the 

southern part of the study area near the Glass Mountains (about 

4,310 feet). The altitude decreased to the northeast, and the 

lowest altitude near the northeastern edge of the study area at the 

Pecos River was about 2,250 feet. The Edwards-Trinity aquifer 

dipped more sharply than the slope of the land surface in two 

locations, Monument Draw trough and the Pecos trough. All 

altitudes were measured in feet above North American Vertical 

Datum of 1988.

 MONUMENT 

DRAW TROUGH

PECOS

TROUGH

Glass

Mountains

Davis

Mountains

Barilla

Mountains

Pecos River

285

10

20

10

285

31°00'

30°30'

102°00'

104°00' 103°00' 102°30' 103°30'

Base modified from U.S. Geological Survey digital data, 1:2,000,000

Albers Equal Area projection, Texas State Mapping System

North American Datum of 1983

0 20 MILES 10

0 20 KILOMETERS 10

Base surface altitude of the Edwards-Trinity aquifer, in feet

 above North American Vertical Datum of 1988

High : 4,315 Low : 1,555

Edwards-Trinity aquifer 

 subcrop

Edwards-Trinity aquifer 

 boundary

Study area boundary

Fault zones

Geologic structure

 boundary

EXPLANATION

?

?

?

?

?

?

?

?

?

? ?

SECTION

B–B'

A Leon–Belding area A'

FB01 FB02 FB03 FB04 FB06 FB09

EXPLANATION

Edwards part of the Edwards-Trinity aquifer

Trinity part of the Edwards-Trinity aquifer

Upper Triassic (actual thickness not determined)

Land surface

Stratigraphic pick of the top of the Edwards part

 of the Edwards-Trinity aquifer

Stratigraphic pick of the top of the Trinity part

 of the Edwards-Trinity aquifer

Stratigraphic pick of the base of the Trinity part

 of the Edwards-Trinity aquifer

Well

Fault zone and relative movement

Fault block identifier (bounded by fault zones)

?

1,500 FB01

2,000

2,500

3,000

3,500

Altitude, in feet above North American

Vertical Datum of 1988

Distance, in feet

0 50,000 100,000 150,000 200,000 250,000 300,000 350,000 400,000 450,000

 MONUMENT 

DRAW TROUGH

PECOS

TROUGH

Glass Mountains

Davis

Mountains

Barilla

Mountains

Pecos River

285

10

20

10

285

31°00'

30°30'

102°00'

104°00' 103°00' 102°30' 103°30'

Base modified from U.S. Geological Survey digital data, 1:2,000,000

Albers Equal Area projection, Texas State Mapping System

North American Datum of 1983

0 20 MILES 10

0 20 KILOMETERS 10

Edwards-Trinity aquifer thickness, in feet

Edwards-Trinity aquifer 

 subcrop

Edwards-Trinity aquifer 

 boundary

Study area boundary

Fault zones

Geologic structure

 boundary

EXPLANATION

5 to less than 86

86 to less than 234

234 to less than 362

362 to less than 510

510 to less 

than 797

 MONUMENT 

DRAW TROUGH

PECOS

TROUGH

Glass

Mountains

Davis

Mountains

Barilla

Mountains

Pecos River

285

10

20

10

285

31°00'

30°30'

102°00'

104°00' 103°00' 102°30' 103°30'

Base modified from U.S. Geological Survey digital data, 1:2,000,000

Albers Equal Area projection, Texas State Mapping System

North American Datum of 1983

0 20 MILES 10

0 20 KILOMETERS 10

Top surface altitude of the Edwards-Trinity aquifer, in feet

 above North American Vertical Datum of 1988

High : 4,315 Low : 1,555

Edwards-Trinity aquifer 

 subcrop

Edwards-Trinity aquifer 

 boundary

Study area boundary

Fault zones

Geologic structure

 boundary

EXPLANATION

Thickness of the Edwards-Trinity Aquifer

Thickness of the Edwards-Trinity aquifer in the study area 

was calculated as the difference in altitudes between its top and 

base. About 50 percent of the aquifer was between 234 and 362 feet 

thick, about 25 percent was less than 234 feet thick, and about 25 

percent was more than 362 feet thick. The minimum thickness was 

5 feet and the maximum thickness was about 797 feet. Some of the 

thinnest sections of the Edwards-Trinity aquifer were in the eastern 

part of the study area, near the northwestern slope of the Glass 

Mountains, and near the northeastern slope of the Davis Mountains. 

It was determined that the aquifer was often thickest in the central 

part of the study area in the Monument Draw trough and at the 

western edge of the study area in the Pecos trough.
Geochemistry

Geochemical Results

Analyses of geochemical and 

isotopic samples provided insights into 

the chemical characteristics of water 

from different sources and different 

aquifers. Chemical characteristics of 

water from different sources were 

used to qualitatively asses the aquifer 

interaction, groundwater-flow paths, 

water-rock interaction, mixing of water 

from different sources, and to identify 

likely source waters and geochemical 

endmembers. Geochemical properties 

that were evaluated included specific 

conductance, hydrochemical facies, 

sulfate and chloride concentrations, 

silica concentrations, stable isotopes 

of oxygen and hydrogen, strontium 

isotopes, environmental tracers, and 

concentrations of organic compounds 

and nutrients. 

Geochemical Endmembers

Four endmembers were identified to use as part of the qualitative groundwater-flow and mixing analysis. The endmembers represented: 

(1) mineralized groundwater that likely recharged northwest of the study area during the Pleistocene and is flowing through the EdwardsTrinity aquifer along regional groundwater-flow paths; (2) dilute, recent recharge from the Barilla and Davis Mountains with a composition 

indicative of interaction with igneous rocks; (3) dilute, recent recharge from the Glass Mountains with a composition indicative of interaction 

with carbonate rocks; and (4) mineralized water that is likely a mixture of recharge under recent and Pleistocene climatic conditions and is 

flowing through the Edwards-Trinity aquifer along regional groundwater-flow paths east of the Monument Draw trough.

Geochemical and isotopic results indicate groundwater in the system likely is dominated by mineralized, regional groundwater flow that 

probably recharged during the cooler, wetter climates of the Pleistocene with variable contributions of recent, local recharge. The mixing of 

water from multiple sources combined with water-rock interaction with various rock types, including siliciclastic, carbonate, evaporite, and 

igneous rocks, contributed to a groundwater chemistry that was complex between and within aquifer units.

1

10

100

1,000

10,000

Sulfate, in milligrams per liter

1 10 100 1,000 10,000

Chloride, in milligrams per liter

EXPLANATION

Site, by contributing aquifer

 Pecos Valley aquifer

 Igneous aquifer

 Edwards-Trinity aquifer

 Dockum aquifer

 Rustler aquifer

 Capitan Reef aquifer

 Spring

Water-quality sampling by the U.S. Geological Survey, San 

Solomon Springs, Texas.

Relation between sulfate concentrations to chloride 

concentrations for samples collected from groundwater and 

spring sites.

Glass

Mountains

Davis

Mountains

Barilla

Mountains

Pecos River

285

10

20

10

285

7

7 7

7

31°00'

30°30'

102°00'

103°00'

104°00'

102°30' 103°30'

Base modified from U.S. Geological Survey digital data, 1:2,000,000

Albers Equal Area projection, Texas State Mapping System

North American Datum of 1983 0 20 MILES 10

0 20 KILOMETERS 10

EXPLANATION

Edwards-Trinity aquifer 

 subcrop

Edwards-Trinity aquifer 

 outcrop

Study area boundary

Fault zones

Geochemistry site

 Spring

 Well, by aquifer

 Pecos Valley aquifer

 Igneous aquifer

 Edwards-Trinity aquifer

 Dockum aquifer

 Rustler aquifer

 Capitan Reef aquifer

7

Location of groundwater-well and spring sites for geochemical data collection.
Groundwater-Flow System

Groundwater Recharge

Four principal sources of recharge to the Edwards-Trinity aquifer were identified: (1) regional groundwater flow in the Edwards-Trinity 

aquifer that originated as recharge northwest of the study area and enters the study area near the western corner; (2) runoff from the Barilla, 

Davis, and Glass Mountains that percolates through underlying rocks and into the gravels along the slopes of the mountains; (3) return flow 

from irrigation; and (4) upwelling from deeper aquifers. Although some of the groundwater appears to have recharged under conditions 

similar to the current climate, the only samples collected from the Edwards-Trinity aquifer that likely recharged during the last 60 years were 

collected from wells in mountain recharge areas and in areas receiving agricultural return flow.

Transmissivity

Transmissivity values calculated and estimated from 

historical aquifer-test data ranged from 1,500 to 1,216,000 

gallons per day per foot. The highest transmissivity values were 

measured in the Monument Draw trough area, which is also one 

of the thickest parts of the Edwards-Trinity aquifer and is in a 

faulted area. The lowest values were measured in the eastern part 

of the study area, near some of the thinnest parts of the aquifer. 

Hydraulic conductivity values generally showed the same trends 

as the transmissivity values. U.S. Geological Survey pump hoist truck and water-quality trailer.

Groundwater Flow

Groundwater-level altitudes (which were used to generate a potentiometric-surface map of the Edwards-Trinity aquifer) ranged from 

about 2,300 to about 3,300 feet and generally decreased from southwest to northeast. Regional groundwater flow is from areas of recharge 

in the south and southwest to the north and northeast. Groundwater generally flows north into the down-dip extent of the Edwards-Trinity 

aquifer or east out of the study area. Regional groundwater flow entering the study area from the northwest naturally discharges from springs 

or turns northward to flow into the Pecos trough where it discharges into the Pecos Valley or Dockum aquifers at the down-dip extent of 

the Edwards-Trinity aquifer. Recharge from the Barilla and Davis Mountains also predominantly flows toward the Pecos trough and most 

likely naturally discharges to other aquifers in the groundwater system. Groundwater flow in the Edwards-Trinity aquifer in the Monument 

Draw trough originated as recharge in the Glass Mountains, agricultural return flow, or upwelling groundwater from lower units. EdwardsTrinity aquifer water generally flows north and northeast in the Monument Draw trough and naturally discharges from springs or to other 

aquifers in the groundwater system at the down-dip extent. Groundwater in the eastern part of the study area likely originated in the Glass 

Mountains, generally flows northeast, and flows out of the study area to the east or naturally discharges from springs or to other aquifers in 

the groundwater system at the down-dip extent or to the Pecos River.

PECOS

COUNTY 

BREWSTER

COUNTY 

PRESIDIO

COUNTY 

REEVES

COUNTY 

TERRELL COUNTY 

CROCKETT

 COUNTY 

JEFF DAVIS

COUNTY 

UPTON COUNTY 

WARD

COUNTY CRANE

COUNTY 

Pecos River Pecos River

Davis

Mountains

Glass

Mountains

285

10

20

10

285

Base modified from U.S. Geological Survey digital data, 1:2,000,000

Albers Equal Area projection, Texas State Mapping System

North American Datum of 1983

Aquifer modified from Ashworth and Hopkins, 1995

Cultivated cropland boundary based on National Land Cover Database, 2006

3100

3000

2900

3100

3000

2800

3500

3400

3300

3200

2700

2600

3600

2700

2600

2500

2400

2600

2500

2600

2300

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

104°00' 103°30' 103°00' 102°30'

31°00'

30°30'

EXPLANATION

Edwards-Trinity aquifer outcrop

Edwards-Trinity aquifer subcrop

Study area boundary

Cultivated cropland area boundary

Fault zone

Groundwater divide

Potentiometric contour, 1980 to 2010—

 Shows altitude at which water would

 have stood in tightly cased well. 

 Dashed where approximately located.

 Interval 25 feet. Datum is North

 American Vertical Datum of 1988

 Major contour

 Minor contour

Approximate regional

 flow direction

Regional inflow

Geochemistry site

Groundwater-level site

Texas Water Development

 Board well used for

 vertical gradient analysis

2500

Groundwater flow and potentiometric-surface map of the Edwards-Trinity aquifer developed using geochemical data and 

the average winter (November through April) groundwater-level data for 1980–2010. 
For additional information, contact 

Director, USGS Texas Water Science Center

http://tx.usgs.gov/

gs-w-txpublic-info@usgs.gov

Publishing support provided by

Lafayette Publishing Service Center

Authors 

Jonathan V. Thomas

Gregory P. Stanton

Johnathan R. Bumgarner

Daniel K. Pearson

Andrew P. Teeple

Natalie A. Houston

Jason D. Payne

MaryLynn Musgrove

This fact sheet is based on the 

following USGS reports:

Pearson, D.K., Bumgarner, J.R., Houston, 

N.A., Stanton, G.P., Teeple, A.P., and 

Thomas, J.V., 2012, Data collection 

and compilation for a geodatabase of 

groundwater, surface-water, waterquality, geophysical, and geologic data, 

Pecos County region, Texas, 1930–

2011; U.S. Geological Survey Data 

Series 678, 67 p. 

http://pubs.er.usgs.gov/publication/ds678

Bumgarner, J.R., Stanton, G.P., Teeple, 

A.P., Thomas, J.V., Houston, 

N.A., Payne, J.D., and Musgrove, 

MaryLynn, 2012, A conceptual model 

of the hydrogeologic framework, 

geochemistry, and groundwater-flow 

system of the Edwards-Trinity and 

related aquifers in the Pecos County 

region, Texas: U.S. Geological Survey 

Scientific Investigations Report 

2012–5124, 74 p. 

http://pubs.er.usgs.gov/publication/

sir20125124

U.S. Department of the Interior

U.S. Geological Survey

Data Series 678

Prepared in cooperation with the Middle Pecos Groundwater Conservation District, 

Pecos County, City of Fort Stockton, Brewster County, and Pecos County Water Control 

and Improvement District No. 1

Data Collection and Compilation for a Geodatabase of 

Groundwater, Surface-Water, Water-Quality, Geophysical, 

and Geologic Data, Pecos County Region, Texas, 1930–2011

?

?

?

?

?

?

?

?

?

? ?

WEST EAST SECTION B–B'

A A'

1,500

2,000

2,500

3,000

3,500

Altitude, in feet

above North American Vertical Datum of 1988

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2012–5124 

(Revised July 10, 2012)

Prepared in cooperation with the Middle Pecos Groundwater Conservation District, 

Pecos County, City of Fort Stockton, Brewster County, and Pecos County Water Control 

and Improvement District No. 1

A Conceptual Model of the Hydrogeologic Framework, Geochemistry, 

and Groundwater-Flow System of the Edwards-Trinity and Related 

Aquifers in the Pecos County Region, Texas

References Cited

Ashworth, J.B., and Hopkins, Janie, 1995, Aquifers of Texas: Texas 

Water Development Board Report 345, 69 p.

Barker, R.A., and Ardis, A.F., 1992, Configuration of the base 

of the Edwards-Trinity aquifer and hydrogeology of the 

underlying pre-Cretaceous rocks, west-central Texas: U.S. 

Geological Survey Water-Resources Investigations Report 

91–4071, 25 p., 1 pl.

Daniel B. Stephens and Associates, 2010, City of Fort Stockton 

groundwater availability analysis—Evaluation of pumping on city 

wells: Prepared for the City of Fort Stockton, 79 p.

INTERRA Incorporated, 2011, Draft conceptual model report for 

the Rustler aquifer: Prepared for the Texas Water Development 

Board, 252 p. 

Meyer, J.E., Wise, M.R., and Kalaswad, Sanjeev, 2011, Pecos 

Valley aquifer, west Texas: Structure and brackish groundwater: 

Texas Water Development Board Brackish Resources Aquifer 

Characterization System (BRACS), 92 p.

Railroad Commission of Texas, 2010, Geophysical log database: 

accessed September 30, 2011, at http://rrcsearch.neubus.com/

esd-rrc/#results.

Texas Water Development Board, 2011, Groundwater database 

reports: accessed December 19, 2011, at http://www.twdb.

state.tx.us/publications/reports/GroundWater Reports/

GWDatabaseReports/GWdatabaserpt.asp.

University Lands, 2011, Well and production data collection: The 

University of Texas System, Well Library, accessed July 1, 

2011, at http://www.utlands.utsystem.edu/techdata.aspx.

Contacts