A LONG-TERM, WATERSHED-SCALE, EVALUATION OF THE IMPACTS OF ANIMAL WASTE BMPs ON INDICATOR BACTERIA CONCENTRATIONS

Within the Owl Run watershed, VA, the impacts of best-management practice (BMP) implementation on bacterial pollution was studied over the long term. Five animal-waste-storage structures were designed as BMPs as part of the study, and a pre-BMP versus post-BMP monitoring design was implemented. The major structural BMPs also included fencing, stream crossings, and watering troughs, while major managerial BMPs included conservation tillage, grassed waterways, and manure management. Four streamflow monitoring stations were established. Results showed that, while annual precipitation totals did not differ significantly between the two monitoring periods, post-BMP increases in annual streamflow totals were much greater. At the main watershed outlet, fecal coliform concentrations were reduced post-BMP, but concentrations increased in all monitored subwatersheds, especially during the summer. Post-BMP reductions in fecal streptococci concentrations were observed across all of the subwatersheds, which was attributed to significant die-off during waste storage. Overall, definitive and consistent evidence of water-quality improvement due to the implementation of BMPs was not found.