The Research Of Runoff And Sediment Yield In Watershed Based On SWAT Model

With abundant of water power resources, the Three Gorges where locates in the upriver of Yangtse River is one of energe centers of China. Recently because of the unreasonable sloping field using and geography condition, the problems of seasonal drought, soil and water losses exist in region of the Three Gorges. The research of the water budget and the the runoff and sediment yield seem to be count for much. In order to simulate the runoff and sediment yield and the water budget in five different land uses (sloping field, paddy field, woodland , stone dike terrace, earth dike terrace) in the watershed of Zhangjiachong with SWAT (Soil and Water Assessment Tool) model, the research adopted the runoff and sediment yield observation, the plot experimentation, the soil physical properties experiment and the weather data analysis. The conclusion is below:According to the measure datas in watershed of Zhangjiachong: From July to August, the rates of rainfall were 56% of the April to October, at the same time, 62% of the whole discharge of runoff and 99% of the whole yield of sediment found in the watershed. The runoff and sediment yield had obvious relativity with the rainfall in the Zhangjiachong watershed and the maximum runoff and sediment production concentrated on July and August which with the greatest rainfall in the whole year.The discharge of runoff and yield of sediment in watershed of Zhangjiachong were simulated by SWAT model. The outputs of SWAT model were calibrated and valided against observed data. A good result indicated that the E_ns of monthly runoff and monthly yield of sediment that between measured and simulated are 0.73 and 0.75, respectively; while the R² are 0.90 and 0.97, respectively.The results of the plot experimentation of five land uses confirmed that:(l)The surface runoff: sloping field> paddy field> earth dike terrace> stone dike terrace> woodland. The greatest surface runoff happened, the greatest soil and water run off were found in the sloping fields, but woodland can more effectively reduce the discharge of surface runoff; (2) The percolation: paddy field> earth dike terrace> stone dike terrace> sloping field> woodland. The variety of the percolation in five different land uses were not remarkable, while the percolation in woodland was the smallest; (3) Continuous daily field observation of water content in the soil surface layer in the five different land uses showed that: the variety of the soil water storage can be considered as no effect in the long period simulation of the water budget with SWAT; (4)The...