U.S. Department of the Interior

U.S. Geological Survey

98 07’ o 98 07’30" o 98 08’ o

29 43’ o

29 42’30" o

29 42’ o

RIVER

GUADA L UPE

GUAD ALUPE

RIVER

RIVER

COM AL

Dry Comal Cree k

Old Ch a nnel

New Cha nnel

Blieders Creek

LANDA LAKE

Panther

 Creek NEW BRAUNFELS

NEW BRAUNFELS

Landa

Seguin

Street

San

Hinman Island D rive

Torrey Street

 N. Union Ave.

Street

Antonio St.

Landa

 Park

Landa Park Drive

Elizabeth

Ave.

Clemens

 Dam

B

A

C D

E

08169000

Other springs in

 Landa Lake

Main

 spring

0 0.1 0.2 0.3 0.4 0.5 MILE

Base from U. S. Geological Survey

TEXAS

San

Water-quality monitoring and 

U.S. Geological Survey

EXPLANATION

New Braunfels and

08169000

Austin

A

Antonio

New Braunfels East;

New Braunfels West

Comal Springs of Central Texas are the largest springs in the 

southwestern United States. The long-term average flow of the 

Comal River, which essentially is the flow from Comal Springs, 

is 284 cubic feet per second (ft3/s). The artesian springs emerge 

at the base of an escarpment formed by the Comal Springs fault. 

The Comal River (fig. 1) is approximately 2 miles (mi) long and 

is a tributary of the Guadalupe River. Most of the Comal River 

follows the path of an old mill race, here referred to as New 

Channel, then flows through a channel carved by a tributary 

stream (Dry Comal Creek), eventually rejoining its original 

watercourse. The original watercourse, here referred to as Old 

Channel, has been reduced to a small stream, the source of 

which is water diverted from Landa Lake and several springs in 

the channel. In addition to being an important economic 

resource of the region, the springs and associated river system 

are home to unique aquatic species such as the endangered 

fountain darter (Etheostoma fonticola). The Comal Springs riffle 

beetle (Heterelmis comalensis), which exists in the springflow 

channel upstream of Landa Lake, has been proposed for listing 

as endangered. The Comal Springs dryopid beetle (Stygoparmus 

comalensis) and the Peck’s cave amphipod (Stygobromus pecki) 

are two subterranean species associated with Comal Springs also 

proposed for endangered listing.

The population in the region has increased 20 to 30 percent 

per decade for the last 3 decades. This increase in population has 

correspondingly increased the use of both surface- and groundWater-Quality Assessment of the 

Comal Springs Riverine System, 

New Braunfels, Texas, 1993–94

water resources in the region, which 

in turn has prompted concern for 

habitats of endangered species that 

depend on the spring water. To better understand the environmental 

needs of threatened or endangered 

species, the U.S. Fish and Wildlife 

Service (USFWS) undertook an 

intensive ecological assessment of 

the Comal Springs riverine system. 

One component of the study 

involved the effects of varied 

springflows on water chemistry and 

aquatic-species habitat in the riverine system. For that study component, the U.S. Geological Survey 

(USGS) provided continuous monitoring of selected water-quality 

properties and collected discrete 

water samples for analysis at 

selected sites along the Comal 

Springs riverine system. The purpose of this fact sheet is to summarize the principal results of the 

USGS water-quality monitoring, 

sampling, and analyses for selected 

properties, major ions, nutrients, 

trace elements, and pesticides during selected periods in the summer 

and winter of 1993–94. Only high 

flow (greater than 300 ft3

/s) 

occurred during the monitoring periods; therefore, effects of lesser 

flows on water quality were not 

measured. Data collected from this 

Figure 1. Comal Springs riverine system, New Braunfels, Texas. study and subsequent monitoring 

Comal Springs

streamflow-gaging station

and number

sampling site and site ID

Spring
2

can be used to evaluate instream flow habitat requirements of the 

fountain darter and other aquatic species.

During the monitoring periods, the New Channel received 

approximately 92 percent of the total volume of springflow by 

way of Landa Lake. New Channel has a uniform stream channel 

and higher velocities than Old Channel. In the upper reach of 

New Channel, west of Landa Park Drive, stream velocities are 

lowest and the bottom is predominantly large gravel and cobbles. In the lower reach, from Landa Park Drive to Clemens 

Dam, the velocities are highest and the streambed predominantly 

is bedrock and large gravel. In contrast, Old Channel received 

about 8 percent of the total volume of springflow. Old Channel 

has the meandering characteristics of a natural stream. In the 

upper reach of Old Channel, from Landa Lake to Elizabeth 

Avenue, are intermittent riffles and pools and a streambed of silt 

and assorted gravels. Downstream of Elizabeth Avenue, the 

stream mostly comprises slow runs and pools with very little riffle habitat; water velocities are minimal and the water appears 

turbid. The streambed is mostly coarse sediment and mud.

Collection of Water-Quality Data

Site selection and data collection were designed to evaluate 

physical and chemical properties of the riverine system. Five 

sites were selected for monitoring the upper and lower reaches 

of the two stream channels. These sites were evaluated to ensure 

uniform mixing of water and that monitoring points were representative of the sites. Two sites were selected on New Channel. 

Site A is at the Landa Lake outfall into New Channel. This site 

represents the start of the riverine system and a composite of the 

spring-fed lake waters. Site B is immediately upstream of the 

confluence of Old and New Channels. This site was selected to 

monitor changes to water chemistry that might have occurred as 

water passed through New Channel. Within Old Channel, two 

sites also were selected. Site C is immediately upstream of 

Elizabeth Avenue and represents a composite of spring-fed lake 

water as it enters Old Channel. Site D is on Old Channel 

upstream of Hinman Island Drive and the confluence of Old and 

New Channels. Data from site E, downstream of the confluence 

of the two channels and on the Comal River immediately 

upstream of Clemens Dam, represent the cumulative effects of 

Old and New Channels.

The properties of pH, temperature, specific conductance, and 

dissolved oxygen were monitored continuously during selected 

periods in the summer and winter of 1993–94. Continuous 

monitoring of water properties required use of a four-parameter 

monitoring probe, which was connected to a data storage device 

and powered by a solar battery. The sites are inaccessible and 

required use of portable, self-contained floating shelters. To 

ensure data quality, the instruments were calibrated before and 

periodically during operation. Monitors measured and logged 

parameters at 30-minute intervals for periods of 3 to 8 weeks, 

depending on the site. Property data at the New Channel sites 

were monitored in the summer from August 20 to September 20, 

1993, and in the winter from January 4 to February 3, 1994. 

Property data at the Old Channel sites were monitored in the 

summer from June 30 to August 18, 1993, and in the winter from 

Figure 2. Daily mean streamflow, Comal River at New Braunfels, Texas, during water-quality monitoring periods, 

1993–94.

30 5 10 15 20 25 31 5 10 15 20 25 31 5 10 15 20

July August September

1993

320

440

340

360

380

400

420

5 10 15 20 25 31 5 10 15 20 25 28

January February

1994

300

440

320

340

360

380

400

420

STREAMFLOW, IN CUBIC FEET PER SECOND

4

March

Summer

Winter

June
3

Table 1. Water properties and major ion concentrations, Comal Springs riverine system, New 

Braunfels, Texas, 1993–94

[μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium 

carbonate; <, less than; NA, not available; ft3

/s, cubic feet per second] 

1 Daily mean flow, 08169000 Comal River at New Braunfels: 350 ft3/s - 8/20/93, 339 ft3

/s - 9/20/93, 

351 ft3/s - 2/3/94, 337 ft3/s - 3/3/94.

Constituent

New Channel Comal River1

Site A Site B Site E

Summer

(9/20/93)

Winter

(2/3/94)

Summer

(9/20/93)

Winter

(2/3/94)

Summer

(9/20/93)

Winter

(2/3/94)

Specific conductance (μS/cm) 548 509 547 509 544 514

pH (standard units) 7.6 7.4 7.8 7.3 7.8 7.1

Temperature (°C) 24.0 23.0 24.0 22.5 24.5 22.0

Dissolved oxygen (mg/L) 7.2 8.2 9.0 9.5 9.0 9.4

Calcium, dissolved (mg/L) 83 82 81 82 80 82

Magnesium, dissolved (mg/L) 16 16 16 16 16 16

Sodium, dissolved (mg/L) 9.9 9.7 11 10 10 10

Potassium, dissolved (mg/L) .70 1.3 .70 1.3 .70 1.3

Alkalinity (mg/L as CaCO3) 230 230 230 230 240 230

Sulfate, dissolved (mg/L) 23 24 24 24 23 24

Chloride, dissolved (mg/L) 15 16 15 16 15 16

Fluoride, dissolved (mg/L) .20 .20 .20 .20 .20 .20

Silica, dissolved (mg/L) 12 11 12 11 12 11

Dissolved solids, sum of constituents (mg/L) 307 309 308 309 307 310

Constituent

Old Channel Comal River1

Site C Site D Site E

Summer

(8/20/93)

Winter

(3/3/94)

Summer

(8/20/93)

Winter

(3/3/94)

Summer

(8/20/93)

Winter

(3/3/94)

Specific conductance (μS/cm) 552 529 565 523 547 541

pH (standard units) 7.7 6.9 7.5 7.3 7.6 7.3

Temperature (°C) 24.0 21.5 25.5 20.5 26.0 23.0

Dissolved oxygen (mg/L) 8.1 11.4 4.4 11.8 9.2 12.0

Calcium, dissolved (mg/L) 83 82 85 81 84 81

Magnesium, dissolved (mg/L) 16 16 16 16 16 16

Sodium, dissolved (mg/L) 9.6 10 10 11 9.5 11

Potassium, dissolved (mg/L) 1.9 1.3 1.6 1.3 <.10 1.3

Alkalinity (mg/L as CaCO3) 230 240 240 240 230 240

Sulfate, dissolved (mg/L) 25 24 26 24 25 24

Chloride, dissolved (mg/L) 16 15 16 16 16 15

Fluoride, dissolved (mg/L) .30 .20 .20 .20 .20 .20

Silica, dissolved (mg/L) 12 12 11 10 12 11

Dissolved solids, sum of constituents (mg/L) 309 310 314 310 NA 309

February 7 to March 4, 

1994. Property data at the 

Comal River site were 

monitored during all four 

periods. Periodic waterquality samples were collected at each of the five 

sites. Samples from New 

Channel and the Comal 

River were collected near 

the end of the monitoring 

periods on September 20, 

1993, and February 3, 

1994. Samples from Old 

Channel and the Comal 

River were collected on 

August 20, 1993, and 

March 3, 1994. Samples 

for major ions, nutrients, 

and trace elements were 

collected using a depthintegrated method at multiple intervals along the 

cross section, then composited. Samples for pesticides were collected using 

a depth-integrated method 

at a single interval at the 

midpoint of the stream.

Streamflow

Continuous streamflow data (fig. 2) were collected from USGS 

streamflow-gaging station 

08169000 Comal River at 

New Braunfels during the 

water-quality monitoring 

periods. Initial daily mean 

streamflow of the Comal 

River for the summer 

monitoring period was 

417 ft3/s on June 30, 1993, 

and ending streamflow 

was 339 ft3

/s on Sept. 20, 

1993. A peak flow of 419 ft3

/s occurred on July 5, 1993, and a 

minimum flow of 338 ft3/s occurred on Sept. 7 and 8, 1993. Initial daily mean streamflow for the winter monitoring period was 

353 ft3/s on January 4, 1994, and ending streamflow was 338 

ft3/s on March 4, 1994. A peak flow of 357 ft3/s occurred on 

January 22 and 24, 1994, and a minimum flow of 337 ft3/s 

occurred on March 3, 1994.

Water Quality

Water Properties

Boxplots summarize the distributions of continuously monitored water-property data at the five sites (fig. 3). In some 

instances, the median is the same as the 25th or 75th percentile. 

Data were edited to correct for instrument drift and to exclude 

instrument malfunction. The number of data values per property 

per site ranged from 1,054 to 2,644. 

For New Channel and Comal River, summer median specific 

conductance shows little variability along the reach, ranging 

from 547 to 551 microsiemens per centimeter at 

25 °C (μS/cm). Winter median specific conductance shows 

more variability than summer, ranging from 525 μS/cm at 

site A to 551 μS/cm at site E. Summer median pH increases 

downstream from 7.3 at site A to 7.6 at sites B and E. Similarly 

during winter, median pH increases from 7.2 to 7.5. Summer 

median water temperature increases downstream from 23.5 

degrees Celsius (°C) at sites A and B to 23.7 °C at site E. 
4

(1.163)

(1,193)

(1,222)

(1,056) (2,344)

(2,644)

(1,362) (1,299) (1,456)

14

28

16

18

20

22

24

26 (1,480) (1,478) (1,499)

SUMMER 1993 WINTER 1994 WINTER 1994 SUMMER 1993

NEW CHANNEL AND COMAL RIVER OLD CHANNEL AND COMAL RIVER

7.0

8.4

7.2

7.4

7.6

7.8

8.0

8.2

(1,480)

(1,478) (1,499)

pH, IN

(1,362) (1,313)

(1,456) (1,056)

(2,344)

(2,644)

(1,193)

(1,215)

(1,163)

SPECIFIC CONDUCTANCE, IN

AT 25 DEGREES CELSIUS

 MICROSIEMENS PER CENTIMETER

(1,160)

(1,214) (1,193)

C D E

(1,056)

(1,910)

(2,637)

C D E

(1,362) (1,302) (1,455)

A B E

SITE

0

15

5

10 (1,480) (1,478) (1,499)

DISSOLVED OXYGEN, IN

A B E

EXPLANATION

25th percentile

Median (50th percentile)

75th percentile

Number of measurements

Minimum value

Maximum value

(1,193)

Aug. 20–Sept. 20 Jan. 4–Feb. 3 June 30–Aug. 18 Feb. 7–Mar. 4

Conversely, winter median water temperature decreases from 

22.8 to 22.4 °C. Summer median dissolved oxygen increases 

downstream from 5.8 milligrams per liter (mg/L) at site A to 8.5 

mg/L at site B and subsequently decreases to 7.7 mg/L at site E. 

Figure 3. Distributions of specific conductance, pH, temperature, and dissolved oxygen, Comal Springs riverine 

system, New Braunfels, Texas, 1993–94. STANDARD UNITS TEMPERATURE, IN DEGREES CELSIUS MILLIGRAMS PER LITER

(1,204)

(1,193)

(1,162)

(2,640)

(2,345)

(1,054)

200

700

250

300

350

400

450

500

550

600 (1,496) (1,478) (1,483) (1,428) (1,298) (1,324)
5

Table 2. Nutrient concentrations, Comal Springs riverine system, New Braunfels, Texas, 

1993–94

[mg/L, milligrams per liter; NA, not available; <, less than; ft3

/s, cubic feet per second] 

1 Daily mean flow, 08169000 Comal River at New Braunfels: 350 ft3/s - 8/20/93, 339 ft3/s - 9/20/93, 

351 ft3

/s - 2/3/94, 337 ft3/s - 3/3/94.

Constituent

(mg/L)

New Channel Comal River1

Site A Site B Site E

Summer

(9/20/93)

Winter

(2/3/94)

Summer

(9/20/93)

Winter

(2/3/94)

Summer

(9/20/93)

Winter

(2/3/94)

Nitrogen, nitrate, dissolved NA 1.87 NA 1.87 NA 2.38

Nitrogen, nitrite, dissolved <0.010 .030 <0.010 .030 <0.010 .020

Nitrogen, ammonia, dissolved .030 .020 .030 .030 .030 .050

Nitrogen, organic, dissolved NA NA NA NA NA NA

Phosphorus, dissolved <.010 <.010 <.010 <.010 <.010 <.010

Phosphorus, ortho, dissolved NA NA NA NA .03 NA

Phosphate, ortho, dissolved (as P) <.010 <.010 <.010 <.010 .010 <.010

Constituent

(mg/L)

Old Channel Comal River1

Site C Site D Site E

Summer

(8/20/93)

Winter

(3/3/94)

Summer

(8/20/93)

Winter

(3/3/94)

Summer

(8/20/93)

Winter

(3/3/94)

Nitrogen, nitrate, dissolved NA NA 1.39 NA NA NA

Nitrogen, nitrite, dissolved <0.010 <0.010 .010 <0.010 <0.010 <0.010

Nitrogen, ammonia, dissolved .030 .020 .060 .030 .030 .010

Nitrogen, organic, dissolved NA NA NA 0.27 NA NA

Phosphorus, dissolved <.010 .010 <.010 .050 <.010 .010

Phosphorus, ortho, dissolved .03 NA .06 NA .03 NA

Phosphate, ortho, dissolved (as P) .010 <.010 .020 <.010 .010 <.010

Similarly, winter median dissolved oxygen increases from 6.2 

mg/L at site A to 9.1 mg/L at site B, then decreases to 8.3 mg/L 

at site E.

For Old Channel and Comal River, summer median specific 

conductance increases from 550 μS/cm at site C to 562 μS/cm at 

site D, then decreases to 549 μS/cm at site E. Similarly, winter 

median specific conductance increases from 523 μS/cm at site C 

to 540 μS/cm at site D, then decreases to 517 μS/cm at site E. 

Summer median pH increases downstream from 7.6 at site C to 

7.8 at site D, then decreases to 7.4 at site E. Winter median pH 

is 7.7 at sites C and D and 7.5 at site E. Summer median temperature increases from 24.6 °C at site C to 25.8 °C at site D 

and subsequently decreases to 23.8 °C at site E. Conversely, 

winter median temperature decreases from 21.4 °C at site C to 

19.7 °C at site D, then increases to 22.7 °C at site E. Summer 

median dissolved oxygen decreases from 6.6. mg/L at site C to 

6.4 mg/L at site D and increases to 8.0 mg/L at site E. Winter 

median dissolved oxygen increases from 8.0 mg/L at 

site C to 10.2 mg/L at site E.

In general, specific conductance, pH, temperature, and dissolved oxygen measured at the time of collection of discrete 

samples (table 1) fall within the range of measurements made by 

the continuous monitors. 

Major Ions

Only slight variability in 

concentrations of major ions 

either along reaches or between 

seasons (along a reach) is 

observed for the periodic waterquality samples collected during high-flow conditions (table 

1). For example, dissolved solids range from 307 to 309 mg/L 

for New Channel and from 309 

to 314 mg/L for Old Channel.

Nutrients

Where measured, concentrations of nutrients and variations 

in concentrations (table 2) are 

small. For all sites, nitrate nitrogen concentrations range from 

1.39 to 2.38 mg/L, nitrite nitrogen concentrations range from 

less than 0.010 to 0.030 mg/L, 

and ammonia concentrations 

range from 0.010 to 0.060 

mg/L. Phosphorus concentrations range from less than 0.010 

to 0.050 mg/L, orthophosphorus 

concentrations range from 0.03 

to 0.06 mg/L, and orthophosphate concentrations range from 

less than 0.010 to 0.020 mg/L.

Trace Elements

Trace elements (table 3) show little variability in concentration either along the reaches or between seasons. Differences in 

concentrations between sites in the same reach and seasons are 

small, less than 5 micrograms per liter (μg/L), except for strontium in Old Channel, which decreases by 50 μg/L from site D to 

site E in both seasons and increases by 50 μg/L from summer to 

winter at site C. Concentrations of strontium (610 to 690 μg/L) 

are 1 to 2 orders of magnitude larger than that of other trace elements. Trace elements for which analyses were below detection 

limits are beryllium (less than 0.5 μg/L), cadmium (less than 1.0 

μg/L), chromium (less than 5 μg/L), cobalt (less than 3 μg/L), 

copper (less than 10 μg/L), mercury (less than 0.1 μg/L), molybdenum (less than 10 μg/L), nickel (less than 10 μg/L), silver 

(less than 10 μg/L), and vanadium (less than 6 μg/L).

Pesticides

Of 29 pesticides for which samples were analyzed (table 4) 

only diazinon was detected during the summer at sites D and E, 

in concentrations of 0.01 and 0.02 μg/L, respectively.

Selected References

Brown, D.S., Petri, B.L., and Nalley, G.M., 1992, Compilation 

of hydrologic data for the Edwards aquifer, San Antonio area, 

Texas, 1991, with 1934–91 summary: San Antonio, Edwards 

Underground Water District Bulletin 51, 169 p.
6

Table 3. Trace element concentrations, Comal Springs riverine system, New 

Braunfels, Texas, 1993–94

[Constituents not detected include beryllium, cadmium, chromium, cobalt, copper, mercury, 

molybdenum, nickel, silver, and vanadium. μg/L, micrograms per liter; <, less than; ft3/s, cubic 

feet per second] 

1 Daily mean flow, 08169000 Comal River at New Braunfels: 350 ft3

/s - 8/20/93, 

339 ft3

/s - 9/20/93, 351 ft3/s - 2/3/94, 337 ft3/s - 3/3/94.

Constituent

(μg/L)

New Channel Comal River1

Site A Site B Site E

Summer

(9/20/93)

Winter

(2/3/94)

Summer

(9/20/93)

Winter

(2/3/94)

Summer

(9/20/93)

Winter

(2/3/94)

Arsenic, dissolved <1 <1 <1 <1 <1 <1

Barium, dissolved 51 51 52 51 52 51

Iron, dissolved <3 <3 <3 <3 3 <3

Lead, dissolved <10 <10 10 <10 <10 <10

Lithium, dissolved 7 6 8 6 7 7

Manganese, dissolved <1 <1 <1 <1 <1 <1

Selenium, dissolved 1 <1 1 <1 1 <1

Strontium, dissolved 610 610 620 620 610 620

Zinc, dissolved 3 <3 <3 5 <3 <3

Constituent

(μg/L)

Old Channel Comal River1

Site C Site D Site E

Summer

(8/20/93)

Winter

(3/3/94)

Summer

(8/20/93)

Winter

(3/3/94)

Summer

(8/20/93)

Winter

(3/3/94)

Arsenic, dissolved <1 2 <1 1 <1 1

Barium, dissolved 51 55 53 55 49 51

Iron, dissolved 3 <3 4 <3 <3 <3

Lead, dissolved <10 10 <10 10 <10 <10

Lithium, dissolved 12 8 13 8 12 8

Manganese, dissolved 2 2 5 4 <1 2

Selenium, dissolved <1 <1 <1 <1 <1 1

Strontium, dissolved 620 670 650 690 600 640

Zinc, dissolved 6 <3 4 <3 <3 5

Table 4. Pesticide concentrations, Comal 

Springs riverine system, New Braunfels, 

Texas, 1993–94

[μg/L, micrograms per liter; compound in bold 

was detected] 

Pesticide

Detection

limit

(μg/L)

PCB 0.1

Polychlorinated naphthalenes .10

Aldrin .010

Chlordane .1

DDD .010

DDE .010

DDT .010

Diazinon .01

Dieldrin .010

Disyston .01

Endosulfan .010

Endrin .010

Ethion .01

Heptachlor .010

Heptachlor epoxide .010

Lindane .010

Malathion .01

Methoxychlor .01

Methylparathion .01

Mirex .01

Parathion .01

Perthane .1

Phorate .01

Silvex .01

Toxaphene 1

Trithion .01

2,4-D .01

2,4-DP .01

2,4,5-T .01

Rothermal, S.R., and Ogden, A.E., 1987a, Hydrochemical 

investigation of the Comal and Hueco Springs systems, 

Comal County, Texas: Edwards Aquifer Research and Data 

Center Report R1–87, 182 p.

______1987b, Hydrochemical investigation of the Comal and 

Hueco Springs systems, Comal County, Texas: Edwards 

Aquifer Research and Data Center Report R2–86, 151 p.

Wells, F.C., 1985, Statistical summary of water-quality data 

collected from selected wells and springs in the Edwards 

aquifer near San Antonio, Texas: U.S. Geological Survey 

Open-File Report 85–182, 162 p.

William F. Guyton and Associates, 1979, Geohydrology of 

Comal, San Marcos, and Hueco Springs: Texas Department 

of Water Resources Report 234, 85 p.

—Lynne Fahlquist and R.N. Slattery

Any use of trade, product, or firm names is for descriptive 

purposes only and does not imply endorsement by the U.S. 

Government.

October 1997 Fact Sheet FS–099–97

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Information on technical reports and hydrologic data related to 

this and other studies can be obtained from:

San Antonio Subdistrict Chief

U.S. Geological Survey

435 Isom Road, Suite 234

San Antonio, Texas 78216

Phone: 210–321–5200

FAX: 210–530–6008

E-mail: gbozuna@usgs.gov

World Wide Web: http://txwww.cr.usgs.gov/