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Publication Date

August 1998


Abstract The presence of nonpoint source pollution in stormwater flowing in Onion Creek can have a direct impact on water quality in the Barton Springs segment of the Edwards Aquifer in Hays County, Texas. To address this concern, the Barton Springs/Edwards Aquifer Conservation District constructed a concrete vault over the entrance to Antioch Cave in the bed of Onion Creek in 1997. This structure was designed to prevent entry into the cave of contaminated stormwater by closure of a valve on the vault during storm events. The goals of the current project were to improve the efficiency of the system at Antioch by automating the operation of the valve and to install two water-quality monitoring systems on Onion Creek, one at Antioch and the other near the upstream end of the recharge zone. Results of water-quality sampling at Antioch indicate that the system is capable of significant reduction of nonpoint source pollution entering the aquifer through Antioch Cave. During the course of this project, approximately 2,436 lbs of nitrogen from nitrate/nitrite, 295 lbs of total phosphorus, and 190,480 lbs of sediment were prevented from entering Antioch Cave. To monitor the potential movement of nonpoint source pollution in the aquifer, a multiport monitor well was installed near Antioch Cave. With this well, groundwater samples can be collected from multiple vertical zones within the Edwards and Trinity Aquifers. Initial results from this well indicate that there is little, if any, hydraulic connection between the Edwards and Trinity Aquifers. Future studies will determine the degree of hydraulic connection between Antioch Cave and the Edwards zones in the multiport monitor well. Open Access - Permission by Publisher See Extended description for more information.


Barton Springs (Austin, Texas, United States), United States, Regional Speleology


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Subject: topical

Regional Speleology

Subject: geographic

United States






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