Abstract: Relief features (e.g.elevation and slope) and hydrological characteristics (e.g.reach length and reach slope) are basic parameters for distributed models of hydrology and water quality.These parameters provide quantified profiles for the natural watershed that is studied with the model.How well the model simulates the processes of water quantity and quality depends directly on the accuracies of those parameters.Currently,Digital Elevation Model (DEM) has been widely used to derive relief and hydrology characteristics in watershed models for hydrology and water quality.Impacts of 10 different resolution DEMs on mean elevation,subbasin area,subbasin slope,reach slope,and longest reach length were evaluated in 4 subbasins with different reliefs.The DEMs,with grid sizes of 1 m,2.5 m,5 m,10 m,20 m,30 m,40 m,80 m,90 m,and 160 m respectively,were resampled with TIN (Triangular Irregular Network) method from digital line graphic data at 1:10 000 scale.Results showed that watershed slope decreased with coarser DEM,and the terrain was smoothed.When DEM was resampled to a coarser one,the rainfall accumulation area and reach length changed along with the boundaries of subbasins and reach network,especially,in hilly areas where the terrains substantially changed within small ranges.No systemic trend was found in reach slope change with DEM resolution.This study reveals the uncertainty in distributed watershed model caused by DEM resolution in parameter level,and provides references for both model developers and users.