Simulation of Monthly Runoff and Sediment in the Namdae River Basin, DPR Korea, via the SWAT Model

Hydrological modelling of watersheds is an important phase in watershed management. This paper presents surface runoff and sediment yield modelling using the Soil and Water Assessment Tool (SWAT) model in the Namdae River basin, Democratic People’s Republic of Korea, whose drainage area is approximately 850 km2. The SWAT model was calibrated and validated by using observed data from 1981–2008 for the streamflow and by using observed data from 1981–1993 for the sediment yield due to limited data. The model parameters were calibrated manually by adjusting sensitive parameters. These findings indicate that even a slight downwards trend in annual rainfall can cause a substantial reduction in streamflow. The results indicate that the higher the agricultural land rate and surface runoff and the lower the forest cover rate are, the higher the sediment yield. The results can be used by water resource managers of the Namdae River basin at a small scale; thus, further studies applying the SWAT model to large-scale watersheds should be performed.