Effects and consideration of storm movement in rainfall-runoff modelling at the basin scale

A number of studies have emphasized the effects of rainfall movement on runoff simulation; nevertheless, due to the lack of rain gauges inside sub-basins, a method using a hyetograph of the nearest gauges to a sub-basin is usually employed. This study investigated the effects of neglecting rainfall movement on overland simulation results in even a middle-sized basin. Simulations were carried out under two conditions: (1) stationary conditions where the nearest gauge hyetograph was used and rainfall movement was ignored, which is quite common in the case of a lack of data, and (2) moving conditions where a shifted hyetograph based on hyetograph timing recorded in the basin was used. The simulation results were compared with the measured discharge at the outlets. The results revealed that using the shifted hyetograph, which could consider the rainfall movement over sub-basins, decreased the mismatches between the simulated and observed hydrograph. In some of the cases, the shifted hyetograph reduced the relative difference more than 20 %. The study provided a useful method to cope with rainfall movement in runoff modelling of sparsely gauged large watersheds.