Characteristics of Stream Water Quality on Draining of Planted Coniferous and Natural Deciduous Forest Catchments in South Korea

The quality characteristics of runoff water during selected precipitation events in planted coniferous (CP) and natural deciduous (DN) forest stands in Pocheon-si, 27.0 km north of Seoul, were assessed via the mean event concentrations and discharge loads. The relationship between stream water quality and the runoff time differential (dQ/dt) indicated that the characteristics of the latter differed during the rising and falling stages of the two catchments. Pearson’s product moment correlation analysis revealed that chemical oxygen demand was significantly correlated with total organic carbon in the rising and falling limbs of the two catchments. When discharge loads were transported with actual precipitation events, the event load at the two sites increased with increasing discharge load. In particular, the total organic carbon and total nitrogen were higher in the CP catchment than in the DN catchment, whereas biological oxygen demand, total suspended solids, total nitrogen, and total phosphorus were higher in the DN catchment than in the CP catchment. Sequences of high and intense precipitation elevated discharge loads, with differences in loads related to the vegetation conditions in headwater areas (≤100 ha) with steep slopes (>20°) and narrow valleys.