IMPROVEMENTS OF A DISTRIBUTED HYDROLOGY MODEL DHSVM AND ITS CLIMATOLOGICAL-HYDROLOGICAL OFF-LINE SIMULATION EXPERIMENTS

The advanced distributed hydrology-soil-vegetat ion model(DHSVM), developed by Wigmosta et al. (1994), is introduced from US Pacific Northwest National Laboratory. To apply DHSVM in China for the first time, some improvements have been implemented in terms of the basin characteristics: (1) To change evapotranspiration model, using the improved Penman-Monteith approach in replace of the original one; (2) To change the model structure, inserting datasets from 4 stations to grid cells for each river basin, instead of datasets from one or two stations; (3) To develop new hydrology, vegetation and soil parameterization schemes for improving the simulated results, with focus on calculation and adjustment of 11 parameters, such as soil porosity φ, field capacity θfc, leaf area index (ILA), stochastic resistance γs, among the total 33 parameters. Then the improved DHSVM is driven by observed datasets for Luanhe River Basin and Sanggan River Basin, respectively. The simulated evapotranspiration (ET), runoff, snow water equivalent, water table, soil moisture and percolation are then gained as DHSVM outputs. The simulated ET shows that the highest peak appears in May or June instead of July or August. This is consistent with the real situations, owing to the improvement of ET model. The simulated runoff process and flood peak are quite consistent with the observed ones. The model efficiency values for Luanhe River and Sanggan River basins are 0.89 and 0.82, respectively, which shows high modeling ability of the model system for both relatively humid and dry basins.