Impacts of GIS data quality on determination of runoff and suspended sediments in the Imha watershed in Korea

Excessive soil loss during heavy rainfall results in serious turbid water problem in the reservoir. For the purpose of efficient turbid water management in the upland area of the Imha watershed in Korea, this study applied SWAT (Soil and Water Assessment Tools) for assessment of the soil erosion and attempted to evaluate the impact of GIS data on model response to test the model efficiency. First, the outputs of runoff and suspended sediment were investigated corresponding to the various DEM grid sizes (i.e., 30, 60, 90, 120, and 150 m). Further analysis was based on the 8 different scenarios combining with different scales of land use (i.e., 1:25,000 and 1:50,000) and soil type maps (i.e., 1:50,000 and 1:250,000) associated with two different DEM grid sizes. Statistical analysis of the simulated results revealed that model efficiency improved with 30 m resolution DEMs for estimation of runoff and suspended sediment. However, no significant improvement was expected associated with detailed scales of land cover and soil maps. The findings of this study will contribute to select the quality of GIS data, with no expense of the accuracy of model prediction to simulate runoff and suspended sediments.