This paper presents a physically based distributed hydrological model for catchmet flood forecasting—the Liuxihe Model. This model constitutes five components including catchment dividing

evaporation

runoff production

runoff routing and parameter deriving. The catchment dividing component divides the whole catchment into grids horizontally and layers vertically. The evaporation component calculates grid evaporation based on precipitation and soil wetness. The runoff production component determines the runoff produced from each grid and divides it into surface runoff

interflow and underground water. Surface runoff is determined with the saturation excess mechanism and the interflow is determined by Campbell equation. The runoff routing component routes the runoff grid by grid over the whole catchment and divides the surface runoff routing into overland flow routing

river channel routing and reservoir routing; The parameter deriving component derives model parameters for every grid in which the parameters are divided into unadjustable parameters that are determined by the DEM and adjustable parameters adjusted with a successive procedure. A method for estimating channel cell crosssection size based on the DEM and the remote sensing imagines of the basin is also proposed

which solves the inapplicability of physically based distributed hydrological model in many basins.