Journal of Korean Society of Agricultural Engineers ISSN:1738-3692(Print) 2093-7709(Online) 한국농공학회논문집

Natural environment of the Wolgokri stream watershed, located in Chuncheon, Gangwon province, Korea, has been well preserved as a traditional agricultural watershed. To analyze characteristics of NPS pollution generated from an mountainous agricultural watershed, the flow and water qualities of the study watershed were monitored and were analyzed to estimate pollution loads. Annual runoff volume ratio was 70.4%. Concentrations of T-N, T-p, COD, and TOC were higher when monthly rainfall was between 0~30mm than those when monthly rainfall was between 30~70mm. However, the concentrations varied considerably when monthly rainfall was higher than 100mm. The flow weighted mean concentrations(mg/L) of BOD, COD, TOC, NO₃-N, T-N, T-P and SS were 1.96, 2.72, 3.32, 1.41, 4.70, 0.187 and 13.36, respectively. The BOD, SS, T-N and T-P loads of July, 2004 were 48%, 17%, 51% and 32% of annual load, respectively. The BOD, COD, TOC, NO₃-N, T-N, T-p, and SS loads (kg/ha) from Mar. 2004 to Apr. 2005 were 19.09, 26.55, 32.39, 13.85, 45.92, 1.887 and 130.18, respectively. The highest concentrations of BOD, NO₃-N, T-N, T-p, SS, COD and TOC were found before the flow reached the peak runoff, possibly due to the first flushing effect. Generally, pollution loads of the Wolgokri watershed were not that significant. Phosphorus load, however, was higher enough to cause eutrophication in the receiving water body. It was recommended that best management practices need to be implemented to reduce phosphorus sources.