Simulating Hydrological Process Of Nested Watersheds On The Loess Plateau By SWAT Model

Because of serious soil erosion in Loess Plateau, many of massive ecological constructions aimed at soil and water conservation have been executed. Research on nested watershed eco-hydrological process and its synergistic changes based on land cover/ land change (LUCC) has an important theoretical significance of land use planning and management and environmental constructions in Loess Plateau.Study area of this thesis is in Caijiachuan nested watershed of west Shanxi province in Loess gullied-hilly region of China. Based on GIS and fractal theory, calculated the fractal information dimension (FID) of landform features of study watersheds. Selected the watershed FID. watershed area, shape factor, watershed length, watershed width, channel density and river slope, these 7 important landform features factors were taken as cluster indicators and sorted to similar watersheds based on cluster analysis function of SPSS. Then, the response of LUCC change to hydrological dynamics in watersheds according to cluster analysis was analyzed.Based on the information data of land use, soil classification, hydrology and meteorology, SWAT model (Soil and Water Assessment Tool) is applied to simulate the eco-hydrological process in Caijiachuan nested watershed. LH-OAT sensitivity analysis and SCE-UA automatic model calibration were implemented in SWAT 2005 version. This thesis is the first employed these two new functions to calibrate and validate the parameters quickly and accurately in Loess Plateau. According to the model evaluation results, it shows that SWAT model could be successfully used to simulate the hydrological process in Loess Plateau.Based on the simulated values of runoff and sediment discharge generated from SWAT, the features and synergism for runoff and sediment discharge from the nested watersheds were deeply analyzed, and the response of eco-hydrological process of the watersheds with similar landform features to the changes of LUCC and precipitation were studied. Besides, Scenery models were established according to different precipitation and different forest vegetation cover and predictive analysis were carried out to discuss the influence of hydrological dynamics. The results show that the contribution of runoff and sediment yield from farmland is the biggest one among other landuse types and the contribution of that from barren land is just lower than that from farmland; the precipitation influences to sediment yield is more significant than that to runoff amount; forest vegetation cover have dramatically eco-hydrological function of reducing runoff and sediment yield, and if increase the area of forest land and shrub land, the watershed will increase the ability of resistance rainfall erosion and have better function to adjust runoff yield and reduce soil loss; the forest vegetation cover influences to sediment yield is more significant than that to runoff amount either.