Research of grid size issue on applying TOPMODEL in Chaohe catchment

摘要

Estimation of the topography index is a key problem for TOPMODEL modeling performance. Besides the calculation method, the distribution of topographic index is closely linked to the DEM scale. The paper analyzed the change of the topographic index with different grid scale (ranging from 50 m to 600 m at 50 m intervals) and applied the methodology on a medium-size watershed-Chaohe catchment of 5340 square kilometers. The TOPMODEL was used to simulate daily hydrological process and to study the impact of DEM scale on topographic index and rainfall-runoff simulation. The results show that the distribution of the topographic index is very sensitive to the DEM scale. The area percentage of high topographic index increases with the DEM scale, which result in more accurate simulation of runoff during drought period with DEM scale larger than 300 m. On the other hand, more accurate simulation of the flood peak coincides with poorer simulation of daily discharge with the same grid scale.