Karst waters serve as important water sources in rural Appalachia and are well-connected to surface waters, making them susceptible to anthropogenic contamination, including by fecal indicator bacteria which represent a public health risk. This work designed and implemented a watershed-scale monitoring program for a 26 km2 sinking stream system in southwest Virginia to determine the fate and transport of E. coli in the system. This hydrologically complex watershed is predominantly agricultural and includes multiple key surface water sinks that enter Smokehole Cave and emerge at Smokehole Spring. Field campaigns at surface sites and within Smokehole Cave included bacteriological sampling, hydrologic measurement, and dye tracing. Field data was synthesized to: 1) examine variations in E. coli concentrations in the watershed during varying flows/seasonal conditions; and 2) calculate E. coli growth/decay coefficients for the karst system during different flow/antecedent conditions. E. coli concentrations at Smokehole Spring consistently peaked days after peak hydrologic stage. Flow conditions and storm event response were the largest drivers of E. coli transport through the system. Dye trace results revealed that water from sinks can be stored or move slowly through the karst system, resurging during storm events. E. coli was calculated to decay within the karst system, with a half-life of about 5-120 days which is longer than the travel time of water through the cave of approximately 0.5-2 days. Findings indicate that E. coli transport in Appalachian karst systems is hydrologically driven, roadside spring water collection is not recommended, and bacterial treatment is encouraged if performed. Targeted land-management practices should be explored to decrease E. coli loadings in karst waters. / Master of Science / Karst (cave) waters serve as important water sources in rural Appalachia and are well-connected to surface waters, making them susceptible to contamination from human or animal waste – a public health risk. A field monitoring program was conducted in an agriculturally impacted stream and cave system in southwest Virginia to determine how E. coli, a bacteria found in the waste of humans and other animals, moves through the system. There are several places where surface water sinks into the cave system, eventually entering Smokehole Cave and emerging at Smokehole Spring. Field data collection was performed at surface sites and within Smokehole Cave including sampling for E. coli, water flow measurements, and dye tracing. Field data was combined to 1) examine variations in E. coli concentrations during varying flows/seasonal conditions and 2) calculate E. coli growth/decay coefficients for the cave system during different flow and soil moisture conditions. It was found that E. coli concentrations at Smokehole Spring consistently peaked days after the water depth. Flow conditions and storm events were the largest drivers in E. coli movement through the system. Dye trace results revealed that water from sinks can be stored or moves slowly through the cave system and resurges during storm events. E. coli was found to decay within the cave system. Findings indicate that E. coli movement in Appalachian cave systems is driven by storm events, roadside spring water collection is not recommended, and bacteria treatment is recommended if performed. Cave-specific land-management practices are recommended to keep E. coli from entering cave waters.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/115791 |
| Date | 17 July 2023 |
| Creators | Schmidt, Diana Felice |
| Contributors | Biological Systems Engineering, Czuba, Jonathan A., Krometis, Leigh Anne Henry, Schreiber, Madeline E. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf |
| Rights | Creative Commons Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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