Research Of Runoff Simulation In Huanjiang Basin Based On SWAT Model

SWAT model is a distributed hydrological model which is based on good physical processes. Lots of studies suggest that SWAT can be better used in runoff simulation. Due to the fragile ecological environment, the serious loss of soil and water, and outstanding problems on the water resources in the Loess Plateau, the SWAT model is selected as the technical means to simulate the runoff of Huanjiang basin in the upstream of the Malian river. Based on the existing datum of DEM, land use and soil types, the study area is divided into63sub basins and183hydrological response units. On the basis of the attribute database which has been constructed, the SWAT model is built in Huanjiang basin. Through the calibration and the validation by the observational runoff data, the simulated results indicate that SWAT model could be successfully in the study area, follow conclusions can be reached:(1) The impacts resulted from the resolution of DEM are studied:The more precise channel, the longer channel and the steeper average slope can be obtained for the30m DEM data compared with the90m DEM data, and the simulation error is smaller for the high-resolution DEM data.(2) The runoff simulation is certain sensitive to the sub-watershed division levels. When the numbers of sub-watershed division have achieved a certain level, the impact of the division level on the model is ignored. In the study area, such division level is about63.(3) In the sensitivity analysis, the more sensitive parameters include ALPHA_BF、 CN2、 SOL_AWC、 ESCO、 SOL_K. In order to obtain better results, these parameters have been adjusted. The results show that in the calibration period during1980-1895and the validation period during1986-1990, the relative simulated error is less than10%, both relative coefficient and Nash-Suttcliffe coefficient are all higher than0.80, thus the model can simulate the runoff in the study area with satisfaction.(4) There are two scene settings:farmland is converted to woodland and farmland is converted to grassland. The results show both the two scenes can lead to the decrease of runoff and the increase of water storage of soil profile, espically the latter.