The aim of this study was to determine the unit load of NPS (non-point source) pollutants including organic variables such as
BOD (biochemical oxygen demand), COD (chemical oxygen demand) and DOC (dissolved organic carbon), nitrogen and phosphorus
constituents, and suspended solids (SS) and their event mean concentration (EMC) of runo flows from a water-shed of mixed forest
land use by intensive field experiments. Field monitoring for continuous measurements of rainfall, flow, and water quality was conducted
over 12 storm events during 2008–2009 using automated and manual sampling methods. The EMCs of individual runo event were
estimated for each water quality constituent based on the flow rate and concentration data of runo discharge. The average EMCs of
BOD, COD, DOC, SS, TN (total nitrogen), NH4
+-N, NO3??-N, TP (total phosphorus), PO4
3??-P from the mixed forest land were 1.794,
3.498, 1.462, 10.269, 0.862, 0.044, 0.634, 0.034, and 0.005 mg/L, respectively. The annual unit loads of BOD, COD, DOC, SS, TN,
NH4
+-N, NO3??-N, TP and PO4
3??-P were estimated as 66.9, 133.2, 55.5, 429.8, 36.5, 1.6, 26.9, 1.3 and 0.1 kg/(ha yr), respectively. In
addition, a ecting parameters on the EMCs were investigated by statistic analysis of the field data. As a result, significant correlations
with precipitation, rainfall intensity, and total runo flows were found in most constituents.