Effect of NPS Loadings from Livestock on Small Watersheds

Abstract The objective of this paper was to quantit atively analyze the effect of concentrated animal feeding operations (CAFO) NPS pollu tion on a small watershe dwater quality. Monitoring was conducted from March to October, 2013. Monthly flow rate and selected water quality at each monitoring site were measured during dry days. Rainy day monitori ng also was conducted. Modeli ng was conducted to evaluate the effect of CAFO NPS po llution on the wate rquality at the watershed outlet. The highest and mean concentration of se lected water quality indices during rainy days were hi gher than those in dry daysin general. The highest TN concentration measured at the CAFP pollution discharge point was 237.831 mg/L. The results revealed that the CAFO NPSpollution sources could be equally blamed for the water quality degradation of the stream. However, the effect of the NPS pollut ion from CAFOs seeme dnot to be very influential to the watershed water quality at the outlet. SWAT modeling revealed that the TN load was reduced by 18.95 %, 23.39 % and30.53 % at the watershed outlet if the TN load at the CAFO NPS pollution discharge point reduced by 20 %, 40 % and 60 %, respec tively. It was though tthat the natural attenuation processes play ed an important role. The modeling was based only on the assumption of the load redu ction and not verified bythe monitored data. Therefore, it was suggested that a long term monitoring studies for the evaluation of the impact of CAFO NPS pollution on the watershed water quality be conducted.Keywords:Livestock; NPS Pollution; Pollution Load; SWAT*