U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2013–3044

July 2013

Prepared in cooperation with Trinity Glen Rose Groundwater Conservation District,

Edwards Aquifer Authority, and San Antonio River Authority

Development of a Geodatabase for Springs Within and 

Surrounding Outcrops of the Trinity Aquifer in Northern 

Bexar County, Texas, 2010–11

Printed on recycled paper

Introduction

The Trinity aquifer is an important source of groundwater 

in central Texas, including Bexar County, where population 

growth has resulted in an increased demand for water 

(Ashworth, 1983; Mace and others, 2000). Numerous springs 

issue from rock outcrops within and surrounding the Trinity 

aquifer in northern Bexar County (fig. 1). The effects of 

increased groundwater withdrawals from the Trinity aquifer on 

springflow in the area are not well documented, but because the 

total amount of water entering, leaving, and being stored in a 

groundwater system must be conserved, increased groundwater 

withdrawals will result in decreases in springflow (Alley and 

others, 1999). Documenting the location, discharge, and basic 

water-quality information of the springs in northern Bexar 

County can provide a baseline assessment for comparison 

to future conditions. Accordingly, the U.S. Geological 

Survey (USGS), in cooperation with the Trinity Glen Rose 

Groundwater Conservation District, the Edwards Aquifer 

Authority, and the San Antonio River Authority, developed a 

geodatabase populated with data associated with springs within 

and surrounding outcrops of the Trinity aquifer in northern 

Bexar County during 2010–11. A geodatabase provides a 

framework for organizing spatial and tabular data (such as 

the geographic location and water-quality characteristics, 

respectively) in a relational database environment, making it 

easier and more intuitive to evaluate changes over time.

Data for 141 springs within and surrounding the Trinity 

aquifer outcrops in northern Bexar County were compiled from 

existing reports and databases. These data were augmented 

with selected data collected onsite, including the location, 

discharge, and water-quality characteristics of selected springs, 

and were entered into the geodatabase. The Trinity aquifer 

in central Texas is commonly divided into the upper, middle, 

and lower Trinity aquifers; all of the information that was 

compiled pertaining to the aquifer is for the upper and middle 

Trinity aquifers. 

Spring Locations and Characteristics 

Spring locations and characteristics were obtained from 

published reports, USGS 1:24,000-scale topographic maps, 

and available digital databases containing information on 

springs in the study area. Data from existing USGS reports 

(Heitmuller and Reece, 2003; Heitmuller and Williams, 2006; 

Clark and others, 2009), Joint Base San Antonio Camp Bullis 

(also referred to as “Camp Bullis”), Camp Stanley Storage 

Activity, and private property owners were included, as were 

discharge and specific conductance data collected during 

field reconnaissance.

The field reconnaissance of springs in the study area was 

done between October 2010 and September 2011 to verify the 

existing location data and collect additional data (discharge 

measurements, water-quality data, and property owner and 

photographic documentation) pertaining to the springs. A 

total of 46 of the 141 springs were visited during the field 

reconnaissance. Location data were collected by using a handheld Global Positioning System (GPS) unit or a digital camera 

with an integrated GPS unit, both with horizontal accuracy 

of tens of feet. Eight springs that discharge near the base of 

the Edwards aquifer outcrop were identified. The gradational 

nature of the contact between the Edwards and Trinity Groups 

made the exact location of the lithologic change difficult to 

determine. Furthermore, because of the steep terrain where 

these springs were located, the contact between the Edwards 

and Trinity Groups was sometimes indistinct.

Discharge at springs with flow ranged from 0.003 to 

1.46 cubic feet per second. Most of the springs with flow were 

found in the outcrop of the upper and middle parts of the 

Trinity aquifer. Basic water-quality data were obtained from 

samples collected at selected springs. Specific conductance 

was measured in 21 springs and ranged from 167 to 1,130 

microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25°C). There were nine springs that measured between 600 

and 1,130 μS/cm at 25°C for specific conductance. Of these, 

one was tentatively identified as issuing from hydrogeologic 

subdivision VIII of the Edwards aquifer, three from the 

cavernous hydrostratigraphic unit of the upper Trinity aquifer, 

one from the Camp Bullis hydrostratigraphic unit of the upper 

Trinity aquifer, two from the fossiliferous hydrostratigraphic 

unit of the upper Trinity aquifer, and two from the middle 

Trinity aquifer (fig. 2). Of the springs with a specific 

conductance less than 600 μS/cm at 25°C, one was tentatively 

identified as issuing from hydrogeologic subdivision VIII of the 

Edwards aquifer, three from the cavernous hydrostratigraphic 
San Antonio

29°45'

29°40'

29°35'

98°24'

98°32'

98°40'

98°48'

BEXAR COUNTY

MEDINA COUNTY

COMAL COUNTY

BANDERA 

COUNTY

KENDALL 

COUNTY

Ch

mi enea Creek

Elm Cree k

West Elm C

E

reek

ast Elm Cree k

Cibolo

Creek

Cibolo

Creek

Ba cl ones Creek

Rundale Creek

Meusebach Creek

Elm

Waterhole Creek

West Fork 

Cibolo Creek

Mud Creek

Helotes Creek

French Creek

Panther Springs Creek

O

ml os Creek

Los Reyes Creek

Leon

Creek

Pecan Creek

Helotes Creek

Cibolo Creek

Creek

Creek

Mud

Mustang

Creek

Creek

Creek

Lewis 

Fork

Huesta Lee Creek

Clear 

Creek

Culebra 

Leon

Leon

Salado 

Salado 

Creek

Creek

Creek

59

66

6

69 68

70 71 73

7

78

77

79

80

82 85

83 84

8

86

88

87

9

89

0

92

93 94 9

9695

98

99

100

97

101

91

102

103

105 104 106

107

109

110

111

112

113

114

11

115

116

118

119

120

121

12

125

126

127

128

129

130

132

13

133

134 135

14

139 138

141

16 17 15

137 18

2

20

19

75 74 76

21 22 67,23

24

26

47

27

28

3

29

122

30

31

33

32

35 34

36

37

4

40

38

39

41

42

45

49 48 50

51

140 52

54

53 25 43

44

5

117136

1

108

123

124

81

160 ¬«4

160 ¬«4

10 § ̈¦

10 § ̈¦

28 £¤1

28 £¤1

EXPLANATION

Edwards aquifer outcropUpper Trinity aquifer outcropMiddle Trinity aquifer outcropEphemeral streamPerennial streamStudy boundarySpring with map identifier—Tail  points in direction of flow; Clark and others, 2013, appendix 1, p. 13–20

105

BEXAR COUNTY

Study area

BALCONES FAULT ZONE

COASTAL

PLAIN

GULF OF 

MEXICO

EDWARDS 

GREAT

PLATEAU

PLAINS

BALCONES FAULT

ZONE

TEXAS

Physiographic provinces from

Fenneman and Johnson, 1946

BEXAR

COUNTY

Study area

Lewis 

Creek

58 56, 57

55 65

64 46 60

61

62

63

Base modified from U.S. Geological Survey 1:100,000-scale digital data Universal Transverse Mercator Projection, zone 14North American Datum of 1983

Aquifer divisions modified from Clark and others, 2009,

and Stein and Ozuna, 1995

0 5 MILES 2.50 5 KILOMETERS 2.5

Figure 1. Springs, streams, and outcrops of the Edwards and Trinity aquifers in the study area in northern Bexar County, Texas.

Figure 1. Springs, streams, and outcrops of the Edwards and Trinity aquifers in the study area in northern Bexar County, Texas.
Helotes Creek

59

66

6

69 68

70 71 73

7

78

77

79

80

82 85

83 84

8

86

88

87

9

89

0

92

93 94 9

9695

98

99

100

97

101

91

102

103

105 104 106

107

109

110

111

112

113

114

11

115

116

118

119

120

121

12

125

126

127

128

129

130

132

13

133

134 135

14

139 138

141

16 17 15

137 18

2

20

19

75 74 76

21 22 67,23

24

26

47

27

28

3

29 122

30

31

33

32

35 34

36

37

4

4038

39

41

42

45

49 48

50

51

140 52

54

53 25 43

44

5

117136

1

108

123

124

81

Ch

mi enea Creek

BEXAR COUNTY

MEDINA COUNTY

COMAL COUNTY

BANDERA 

COUNTY

KENDALL 

COUNTY

Creek

Creek

Mud

Mustang

Creek

Creek

Cibolo Creek

Creek

Lewis 

Fork

Huesta Lee Creek

Clear 

Creek

Culebra 

Leon

Leon

Salado 

Salado 

Creek

Creek

Creek

Kgrcb

Kgrcb

Kgrue

Kgrf

Kgrf

Kgrf

Kgrue

Kgrcb

Kgrcb

Kgrl

Kgrl

Kgrl

Kgrc

Kgrc

Kgrc

Kkbn

Kkbn

Elm Cree k

West Elm C

E

reek

ast Elm Cree k

Cibolo

Creek

Cibolo Creek

Ba cl ones Creek

Rundale Creek

Meusebach Creek

Elm

Waterhole Creek

West Fork 

Cibolo Creek

Mud Creek

Helotes Creek

French Creek

Panther Springs Creek

O

ml os Creek

Los Reyes Creek

Leon Creek

Pecan Creek

29°45'

29°40'

29°35'

98°24'

98°32'

98°40'

98°48'

Figure 2. Hydrogeology and faulting of the study area, northern Bexar County, Texas.

Edwards

Edwards 

aquifer

Trinity

Member

Basal 

nodular

Upper 

Lower 

Formation Group Aquifer

Upper Trinity aquifer

Middle 

Trinity

aquifer

Kainer Glen Rose Limestone

EXPLANATION

Fault certain—Dashed  where inferredEphemeral streamPerennial streamStudy boundarySpring with map identifier—Tail  points in direction of flow; Clark and others, 2013, appendix 1, p. 13–20

105

Kkbn

Kgrc

Kgrcb

Kgrue

Kgrf

Kgrle

Kgrl

Hydrogeologic subdivision Member younger than hydrogeologic subdivision VIII VIIIInformal hydrostratigraphic unit Cavernous Camp Bullis Upper evaporite Fossiliferous Lower evaporite Not subdivided

Lewis 

Creek

60

61

62

63

64 65

45

46

55

56, 57 58

Kgrcb

Kgrue

Kgrf

Base modified from U.S. Geological Survey 1:100,000-scale digital data Universal Transverse Mercator Projection, zone 14North American Datum of 1983

Hydrogeology modified from Clark and others, 2009,

and Stein and Ozuna, 1995

0 5 MILES 2.50 5 KILOMETERS 2.5

Figure 2. Hydrogeology and faulting of the study area, northern Bexar County, Texas.
This fact sheet is based on the following USGS report:

Clark, A.K., Pedraza, D.E., Morris, R.R., and Garcia, T.J., 

2013, Geodatabase and characteristics of springs within and 

surrounding the Trinity aquifer outcrops in northern Bexar 

County, Texas, 2010–11: U.S. Geological Survey Data Series 

750, 20 p.

References Cited

Alley, W.M., Reilly, T.E., and Franke, O.L., 1999, Sustainability of 

ground-water resources: U.S. Geological Survey Circular 1186, 

79 p. (Available at http://pubs.usgs.gov/circ/circ1186/.) 

Ashworth, J.B., 1983, Ground-water availability of the Lower 

Cretaceous formations of the Hill Country of south-central 

Texas: Texas Department of Water Resources Report 273, 172 

p., accessed March 22, 2011, at http://www.twdb.state.tx.us/

publications/reports/numbered_reports/doc/R273/Report273.asp.

Clark, A.K., Pedraza, D.E., Morris, R.R., and Garcia, T.J., 

2013, Geodatabase and characteristics of springs within and 

surrounding the Trinity aquifer outcrops in northern Bexar 

County, Texas, 2010–11: U.S. Geological Survey Data Series 

750, 20 p.

Clark, A.R., Blome, C.D., and Faith, J.R., 2009, Map showing 

geology and hydrostratigraphy of the Edwards aquifer catchment 

area, northern Bexar County, south-central Texas: U.S. 

Geological Survey Open-File Report 2009–1008, 24 p., 1 pl.

Fenneman, N.M., and Johnson, D.W., 1946, Physical divisions 

of the United States: U.S. Geological Survey, 1 sheet, scale 

1:7,000,000.

Heitmuller, F.T., and Reece, B.D., 2003, Database of historically 

documented springs and springflow measurements in Texas: 

U.S. Geological Survey Open File Report 03–315, 4 p.

Heitmuller, F.T., and Williams, I.P., 2006, Compilation of historical 

water-quality data for selected springs in Texas, by ecoregion: 

U.S. Geological Survey Data Series 230, 32 p.

 Mace, R.E., Chowdhury, A.H., Anaya, Roberto, and Way, S.C., 

2000, Groundwater availability of the Trinity aquifer, Hill 

Country area, Texas—Numerical simulation: Austin, Texas 

Water Development Board Report 353, 117 p.

Stein, W.G., and Ozuna, G.B., 1995, Geologic framework and 

hydrogeologic characteristics of the Edwards aquifer recharge 

zone, Bexar County, Texas: U.S. Geological Survey WaterResources Investigations Report 95–4030, 8 p.

By A.K. Clark and D.E. Pedraza

For additional information contact:

Director, Texas Water Science Center

U.S. Geological Survey

1505 Ferguson Lane

Austin, Texas 78754–4501

http://tx.usgs.gov/

Publishing support provided by

Lafayette Publishing Service Center

unit of the upper Trinity aquifer, two from the Camp Bullis 

hydrostratigraphic unit of the upper Trinity aquifer, one from the 

fossiliferous hydrostratigraphic unit of the upper Trinity aquifer, 

and four from the middle Trinity aquifer (fig. 2). Geochemical 

investigations including detailed water-quality analyses would help 

to confirm the aquifer or combination of aquifers that supply flow 

to each spring.

Increasing water demands are likely to continue to affect 

springflows throughout Texas. By completing reconnaissancelevel field investigations and compiling existing data, similar 

geodatabases could be developed for other aquifer systems 

in Texas. 

Spring near the headwaters of Leon Creek in the Trinity aquifer outcrop, 

northern Bexar County, Texas (photograph taken October 5, 2010).

U.S. Geological Survey employee preparing to measure springflow 

discharging from a spring in northern Bexar County, Texas (photograph 

taken December 8, 2010).

Spring near Leon Creek in the Trinity aquifer outcrop, northern Bexar 

County, Texas (photograph taken October 5, 2010).