Sources of fecal pollution in Virginia's Blackwater River

Sources of fecal pollution in the Blackwater River in south-central Virginia were identified. The study area encompassed intensive dairy and beef farming. abundant wildlife populations, homes with on-site septic systems, and four stream segments listed as impaired due to high-fecal coliform concentrations. A library of antibiotic resistance profiles was developed for 1,451 Enterococcus isolates from human. wildlife. and livestock. A discriminant analysis model was used to classify the isolates by source and calculate rates Of Correct classification (RCC) for each source. RCCs for the known source library were 82.3% for human, 86.2% for livestock, and 87.4% for wildlife. Profiles were determined for Enterococcus isolates from stream samples collected periodically from August 1999 to August 2001 (a total of 8,542 isolates) and compared against the known source library. Livestock contributed the highest percentage of isolates (47.6%) in the four segments studied, followed by wildlife (29.1%), and human (24.9%). The results indicate that reducing fecal pollution will require consideration of all three source categories. The results from this research are being used to develop total maximum daily load project allocations for fecal coliforms in the Blackwater River.