A comparative study on grid-based storm runoff prediction using Thiessen and spatially distributed rainfall

The simulated streamflow from Thiessen average rainfall (T) and spatially distributed rainfall (R) may be significantly different from each other. To identify the hydrologic effects quantitatively, the grid-based kinematic wave storm runoff model was adopted. The model predicts temporal and spatial variations of surface and subsurface flow at each cell by calculating the water balance, and routes the streamflow to the outlet. The model was tested at the Yeoncheondam watershed (1,875 km²), one third of which belongs to North Korea. The watershed is elongated to north and south directions crossing the border. Four rain gauges cover the watershed within the territory of South Korea, while no records from North Korea are given. The simulated results showed the large differences in runoff volume and peak flow rates between T and R when rain moves in a north to south direction. The simulated results of east-to-west-direction storms showed little difference in the hydrographs. The hydrograph was strongly affected by the spatial variations of the rainfall moving along the stream of the watershed.