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Water-Quality Assessment of the Comal Springs Riverine System

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Water-Quality Assessment of the Comal Springs Riverine System Water-Quality Assessment of the U.S. Department of the Interior Comal Springs Riverine System, U.S. Geological Survey New Braunfels, Texas, 1993–94 Comal Springs of Central Texas are the largest springs in the the channel. In addition to being an important economic southwestern United States. The long-term average flow of the resource of the region, the springs and associated river system Comal River, which essentially is the flow from Comal Springs, are home to unique aquatic species such as the endangered is 284 cubic feet per second (ft3/s). The artesian springs emerge fountain darter (Etheostoma fonticola). The Comal Springs riffle at the base of an escarpment formed by the Comal Springs fault. beetle (Heterelmis comalensis), which exists in the springflow The Comal River (fig. 1) is approximately 2 miles (mi) long and channel upstream of Landa Lake, has been proposed for listing is a tributary of the Guadalupe River. Most of the Comal River as endangered. The Comal Springs dryopid beetle (Stygoparmus follows the path of an old mill race, here referred to as New comalensis) and the Peck’s cave amphipod (Stygobromus pecki) Channel, then flows through a channel carved by a tributary are two subterranean species associated with Comal Springs also stream (Dry Comal Creek), eventually rejoining its original proposed for endangered listing. watercourse. The original watercourse, here referred to as Old The population in the region has increased 20 to 30 percent Channel, has been reduced to a small stream, the source of per decade for the last 3 decades. This increase in population has which is water diverted from Landa Lake and several springs in correspondingly increased the use of both surface- and ground- water resources in the region, which o 98 08’ 98o 07’30" 98o 07’ in turn has prompted concern for k B e l e ie r habitats of endangered species that de C r s G U depend on the spring water. To bet- A R D I Other springs in V A ter understand the environmental Landa Lake E E L K R U LA PE o A Torrey Street 29 43’ D needs of threatened or endangered N LA Panther species, the U.S. Fish and Wildlife Main Elizabeth NEW BRAUNFELS spring Creek Service (USFWS) undertook an intensive ecological assessment of L el a Ol nn the Comal Springs riverine system. n d Ch a d Ave. a P Landa N. Union Ave. One component of the study ar k Drive Park C D involved the effects of varied A springflows on water chemistry and o Hin ive 29 42’30" man Island D r Clemens aquatic-species habitat in the river- New Dam Cha nnel ine system. For that study compo- B E nent, the U.S. Geological Survey 08169000 Street (USGS) provided continuous moni- Landa Seguin R toring of selected water-quality Antonio St. VE I G R C U properties and collected discrete NEW BRAUNFELS O A M D k ee Street A R A water samples for analysis at r L C L I mal San V U y Co E P Dr R E selected sites along the Comal 29o 42’ Springs riverine system. The pur- 0 0.1 0.2 0.3 0.4 0.5 MILE pose of this fact sheet is to summa- rize the principal results of the Base from U. S. Geological Survey New Braunfels East; USGS water-quality monitoring, New Braunfels West sampling, and analyses for selected properties, major ions, nutrients, EXPLANATION trace elements, and pesticides dur- A Water-quality monitoring and sampling site and site ID ing selected periods in the summer TEXAS 08169000 U.S. Geological Survey and winter of 1993–94. Only high San Austin streamflow-gaging station flow (greater than 300 ft3/s) Antonio and number occurred during the monitoring peri- Spring ods; therefore, effects of lesser New Braunfels and Comal Springs flows on water quality were not measured. Data collected from this Figure 1. Comal Springs riverine system, New Braunfels, Texas. study and subsequent monitoring can be used to evaluate instream flow habitat requirements of the represents the start of the riverine system and a composite of the fountain darter and other aquatic species. spring-fed lake waters. Site B is immediately upstream of the confluence of Old and New Channels. This site was selected to During the monitoring periods, the New Channel received monitor changes to water chemistry that might have occurred as approximately 92 percent of the total volume of springflow by water passed through New Channel. Within Old Channel, two way of Landa Lake. New Channel has a uniform stream channel sites also were selected. Site C is immediately upstream of and higher velocities than Old Channel. In the upper reach of Elizabeth Avenue and represents a composite of spring-fed lake New Channel, west of Landa Park Drive, stream velocities are water as it enters Old Channel. Site D is on Old Channel lowest and the bottom is predominantly large gravel and cob- upstream of Hinman Island Drive and the confluence of Old and bles. In the lower reach, from Landa Park Drive to Clemens New Channels. Data from site E, downstream of the confluence Dam, the velocities are highest and the streambed predominantly of the two channels and on the Comal River immediately is bedrock and large gravel. In contrast, Old Channel received upstream of Clemens Dam, represent the cumulative effects of about 8 percent of the total volume of springflow. Old Channel Old and New Channels. has the meandering characteristics of a natural stream. In the upper reach of Old Channel, from Landa Lake to Elizabeth The properties of pH, temperature, specific conductance, and Avenue, are intermittent riffles and pools and a streambed of silt dissolved oxygen were monitored continuously during selected and assorted gravels. Downstream of Elizabeth Avenue, the periods in the summer and winter of 1993–94. Continuous stream mostly comprises slow runs and pools with very little rif- monitoring of water properties required use of a four-parameter fle habitat; water velocities are minimal and the water appears monitoring probe, which was connected to a data storage device turbid. The streambed is mostly coarse sediment and mud. and powered by a solar battery. The sites are inaccessible and required use of portable, self-contained floating shelters. To Collection of Water-Quality Data ensure data quality, the instruments were calibrated before and Site selection and data collection were designed to evaluate periodically during operation. Monitors measured and logged physical and chemical properties of the riverine system. Five parameters at 30-minute intervals for periods of 3 to 8 weeks, sites were selected for monitoring the upper and lower reaches depending on the site. Property data at the New Channel sites of the two stream channels. These sites were evaluated to ensure were monitored in the summer from August 20 to September 20, uniform mixing of water and that monitoring points were repre- 1993, and in the winter from January 4 to February 3, 1994. sentative of the sites. Two sites were selected on New Channel. Property data at the Old Channel sites were monitored in the Site A is at the Landa Lake outfall into New Channel. This site summer from June 30 to August 18, 1993, and in the winter from 440 420 400 380 360 340 Summer 320 30 5 10 15 20 25 31 5 10 15 20 25 31 5 10 15 20 June July August September 1993 440 420 400 Winter STREAMFLOW, IN CUBIC PER FEET SECOND 380 360 340 320 300 5 10 15 20 25 31 5 10 15 20 25 28 4 January February March 1994 Figure 2. Daily mean streamflow, Comal River at New Braunfels, Texas, during water-quality monitoring periods, 1993–94. 2 February 7 to March 4, Table 1. Water properties and major ion concentrations, Comal Springs riverine system, New 1994. Property data at the Braunfels, Texas, 1993–94 Comal River site were [µS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; CaCO , calcium monitored during all four 3 carbonate; <, less than; NA, not available; ft3/s, cubic feet per second] periods. Periodic water- quality samples were col- New Channel Comal River1 lected at each of the five Site A Site B Site E Constituent sites. Samples from New Summer Winter Summer Winter Summer Winter Channel and the Comal (9/20/93) (2/3/94) (9/20/93) (2/3/94) (9/20/93) (2/3/94) River were collected near Specific conductance (µS/cm) 548 509 547 509 544 514 the end of the monitoring pH (standard units) 7.6 7.4 7.8 7.3 7.8 7.1 periods on September 20, Temperature (°C) 24.0 23.0 24.0 22.5 24.5 22.0 1993, and February 3, Dissolved oxygen (mg/L) 7.2 8.2 9.0 9.5 9.0 9.4 1994. Samples from Old Calcium, dissolved (mg/L) 83 82 81 82 80 82 Channel and the Comal Magnesium, dissolved (mg/L) 16 16 16 16 16 16 River were collected on Sodium, dissolved (mg/L) 9.9 9.7 11 10 10 10 August 20, 1993, and Potassium, dissolved (mg/L) .70 1.3 .70 1.3 .70 1.3 March 3, 1994. Samples Alkalinity (mg/L as CaCO3) 230 230 230 230 240 230 for major ions, nutrients, Sulfate, dissolved (mg/L) 23 24 24 24 23 24 and trace elements were Chloride, dissolved (mg/L) 15 16 15 16 15 16 collected using a depth- Fluoride, dissolved (mg/L) .20 .20 .20 .20 .20 .20 integrated method at mul- Silica, dissolved (mg/L) 12 11 12 11 12 11 tiple intervals along the Dissolved solids, sum of constituents (mg/L) 307 309 308 309 307 310 cross section, then com- posited.
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