Barton Springs

Figure 6. The Barton Springs aquifer and contributing zone and location of sampling sites.

The water quality of Barton Springs is important for several reasons. It provides a part of Austin s municipal water supply it is the sole home of the Barton Springs salamander (Eurycea sosorum), listed as an endangered species by the U.S. Fish and Wildlife Service and it is considered a significant addition to Austin s quality of life and an important tourist attraction. 

Figure 7. Barton Springs discharge (Q) after storms 1 and 2. Note the increase in Q.

Visual evidence and timing of sediment peaks indicate that some portion of discharging sediments is allogenic. The colored fibers and organic matter are both clearly allogenic. Sediment samples collected from Barton Springs have an organic... 

Finally, there are five different creek basins contributing flow to Barton Springs, each with discrete recharge points and different flowpaths and travel times. Thus, it cannot be expected that the mineralogic composition of the discharging sediment would be homogeneous. 

Table 2. Concentrations of trace elements and hydrophobic organic compounds found on suspended sediments at Barton Springs and Barton Creek, in mg/kg. Sediment quality guidelines (PEL and TEL) are from Environment Canada (1998), except those for T-PAH, which are from MacDonald et al. (2000). 

City of Austin, 2000, Update on Barton Springs water quality analysis Water Quality Report Series COA-ERM-200C, 20 p. 

Hauwert, N.M, Johns, D. A., and Aley, T. J., 1998, Preliminary Report on Groundwater Tracing Studies Within the Barton Creek and Williamson Creek Watersheds, Barton Springs/Edwards Aquifer, prepared by the Barton Springs/Edwards Aquifer Conservation District and the City of Austin Watershed Protection Department, May 1998. 

Hauwert, N. and Vickers, S., 1994, Barton Springs/Edwards Aquifer Hydrogeology and Groundwater Quality, submitted by the Barton Springs/Edwards Aquifer Conservation District to the Texas Water Development Board. 

Slade, R. M., Jr., Dorsey, M., and Stewart, S., 1986, Hydrology and Water Quality of the Edwards Aquifer associated with Barton Springs in the Austin Area, Texas, U.S. Geological Survey Water-Resources Investigations 86-4036. 

U.S. Fish and Wildlife Service, 1997, Final rule to list the Barton Springs Salamander as endangered. Federal Reg, 62 23377-23392. 

Although in general water quality at Barton Springs is good, there have been occurrences of contamination across the aquifer. Petroleum hydrocarbons, arsenic, lead, pesticides, and other compounds have been identified from aquifer wells (Hauwert and Vickers, 1994). Many of these compounds sorb onto solid surfaces in much higher concentrations than their concentration in water. 

Figure 4 is the XRD pattern of the <2 pm fraction (oriented and glycol-solvated) of the suspended sediment discharged at Barton Springs. Though some quartz, calcite, and... 

Figure 3. Scanning electron microscope images of suspended sediment discharged at Barton Springs.

Most caves in the Edwards Limestone do contain a clay suite very similar to the clays found in the suspended sediment discharged from Barton Springs. The I/S in the cave clays is identical to the BS I/S (Fig. 5). The presence of laminations in some cave clay deposits indicates that, like the terra rossa, the clastic material was washed into caves and was not derived from dissolution of the Edwards Limestone (Kastning, 1986 Ellis, 1986 Flavorka et ak, 1996). Similarity of clay suites in the caves and in the discharged sediment implies that the source area for the clays, and the processes leading to its deposition in caves or transport through the aquifer, have been the same for an extended period of time. 

Figure 6 shows XRD patterns of the <2 pm fraction (oriented and glycol-solvated) of samples of soils found in the recharge zone. The 17 A, 8.4 A and 5.64 A peaks in the pattern of Edwards soil A show that smectite, not BS I/S, is present in that sample. Furthermore, Edwards soil A does not contain illite, which is present in the Barton Springs suspended sediment. Therefore, Edwards soil A is not the source of the clastic material discharged from Barton Springs. Neither is Edwards soil B, which is also found... 

The I/S peak at 11.8 A in the pattern of soil developed on the Del Rio Clay indicates ordered interstratification as opposed to the random interstratification in the BS I/S (16.9 A peak). Soils developed on the Buda Limestone contain smectite and yield XRD patterns similar to Edwards soil A. Therefore, neither the Del Rio Clay nor the Buda Limestone is the source of the Barton Springs suspended sediment. 

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