| One of the issues associated with the use of ambient water quality standards for surface water regulatory compliance is the difficulty of identifying nonpoint source pollution at the local level. To this end, practitioners in the real world need credible information to make informed decisions on improving local surface water quality. This dissertation attempts to address the practitioner's needs by using alternative (less expensive) nutrient and bacteria measurement and a targeted sampling strategy to locate nutrient and bacterial sources in a complex watershed. All field work was conducted in the rural Bush River watershed (297 km2, 186 stream-km) located in the South Carolina Piedmont. First, we compared nitrate and phosphate readings from a standard laboratory spectrophotometer (ST) to those measured by a pocket colorimeter kit (KT). We observed good linearity between instruments; however, KT variability was many times higher than ST variability; in addition, the KT instrument consistently provided higher phosphate readings than the ST instrument in the field exercise. Second, we compared fecal coliforms, enumerated by membrane filtration (MF), to E. coli, measured by a commercialized enzyme substrate method (QT). While we observed good linearity between MF and QT, we found that MF under-recovered fecal coliforms, particularly at higher bacterial densities. Based on findings in the study, we considered E. coli to be an adequate, if not conservative, substitute for fecal coliforms in this watershed. Third, we divided the watershed into 24 manageable reaches and sampled each reach repeatedly, analyzing for total nitrogen (TN) total phosphorus (TP) and Escherichia coli bacteria. The most polluted stream reaches were located in riparian grazing operations, and one was located in a downtown area. It is remarkable that these traditional nonpoint sources behaved like point sources in the sense that we were able to detect significant pollution, even under baseflow conditions. We found that this sampling strategy gave practitioners the real-world information they needed to communicate with their respective stakeholders and that the information provided them with reasonable justification to take concrete management actions in the watershed. |
