Abstract:

TOPMODEL，a semidistributed hydrological model,was applied in the Qingjiang headwater catchment in order to evaluate its performance for rainfall runoff simulation in large catchments.SRTM digital elevation model (DEM) and DEM derived from topographic contours were used for topographic index computation and rainfall runoff simulation.The result shows that although the topographic indexes and calibrated parameters were much different,the simulation efficiencies were almost the same with both DEMs.As a free nearglobal DEM dataset,SRTM can greatly improve the convenience of TOPMODEL.The limitation of TOPMODEL for rainfall runoff simulation in large catchments was analyzed and a subcatchment based distributed TOPMODEL was then proposed.In the proposed distributed hydrological model,model parameters were calibrated with the land cover and soil datasets to decrease the number of parameters and the model uncertainty.The impact of subcatchment partitioning on the simulation efficiency was also discussed to assess the ability of the proposed model for rainfall runoff simulation.The result shows that the proposed model yielded a higher efficiency than the traditional model as it reduced the effect of the spatial heterogeneity of rainfall and underlying surface properties on rainfall runoff modeling.Moreover,the simulation efficiency increased with more subcatchments until reached the maximum efficiency,which can not be improved by adding the number of subcatchments as the uncertainty of model inputs and the model structure.

Key words: TOPMODEL/ digital elevation model/distributed hydrological model/Qingjiang catchment