A study of rainfall-runoff response in a catchment using TOPMODEL

The simplicity of Topography-based hydrological model (TOPMODEL),as a way of reflecting the topographic controls on soil water storage and runoff generation,has become more attractive and morepopular for land surface process study since digital elevation models (DEMs) have become widely available.In this paper,the effect of the topography index on soil water storage distribution,which is the key to TOPMODEL,is explained.Then a simple water cycle model for estimating other components of the surface water cycle is developed,which is implemented into the TOPMODEL to integrate the water cycle of the catchment.Using the output of a DEM from 100 m × 100 m resolution data and a single flow direction algorithm,the index distribution function is calculated for a catchment (around 2500 km2 )in the upper reaches of the Yangtze River under different channel initiation thresholds.Finally,the daily and monthly rainfall-runoff response from 1960 to 1987 for the catchment is simulated with the TOPMODEL coupled with the simple water cycle model.