Study On The Application Of The SWAT Model In The Watershed On Loess Plateau

Soil erosion is very serious on the Loess Plateau, and these issues are directly in connection with water. Therefore, it is great significant to opt for the suitable hydrological model for understanding the regional hydrology mechanism, predictiing and reasonable using of water resources. It is also meaningful for resolving the relevant ecological and economic problems. Under the support of National Basic Research Program (973), this paper applied the distributed hydrological model SWAT on the Caijiachuan watershed of Jixian County, Shanxi Province, simulated the rainfall and runoff, and anylase the relationship between watershed landuse change and hydrological process.Distributed hydrological model SWAT embedded in Arcview software is used for simulating daily runoff from March to November in Caijiachuan watershed. Through a lot of data processing and literature review, the initial parameters were determined. With the GIS software, the spatial and attribute datasets for running SWAT were built, the relationship between watershed landuse change and hydrological process were anylased. By model parameter sensitivity analysis, the main parameters influencing runoff are SCS Runoff Curve Number, available water capacity of the soil layer SOL_AWC, soil evaporation compensation factor ESCO. The model was calibrated by adjusting hydrological parameters. In calibration period, relative coefficient is 0.843, Nash-Suttcliffe coefficient is 0.795, in validation period relative coefficient is 0.802, Nash-Suttcliffe coefficient is 0.765.According to the analysis results, the hydrological process was well simulated in the rain seasons, compared to the dry seasons, especially above 15mm precipitation, with the relative coefficient above 0.8. The simulation values will be zero while daily runoff is smaller than 0.01mm. In conclusion, the SWAT model is applicable on the Loess Plateau. It shows the spatial distribution of precipitation in three years by subbasins division. Through the creation of simulation scenarios for different precipitation, the response different forest vegetation cover and landuse type changes in the hydrological scenario were analysed. It concludes that the runoff increase with vegetation cover reducing. Water yield increased to 149.4% from 374,900 m~3 when the forest cover changes from entire valley to non-forested watershed. In the rainy season, the forest vegetation can significantly influence runoff. It concludes water production in farmland is 1.56 times as much as that in pasture. The results can be reference to landuse management and establishment of the Loess Distributed hydrological model.