| Soil erison prediction model was an effective tool to assess soil erosion, design soil and water conservation scheme and resource survey. WEPP was concerned in soil and water conservation field since it was issued. WEPP application to China were mainly concentrated in the purple soil region of the middle and upper reaches of Yangzhe River basin and the Loess Plateau, but there is no WEPP application and assessment in the black soil region of Northeast China. This thesis used field observed data of runoff and soil loss from small watershed in Binxian and Hailun city, to predict runoff and soil loss under rain events at different slope gradients, different plants and different tillage measures, and then assessed the applicability of WEPP in northeast black soil region. The main research results were as follows:1)The sensitive analysis of WEPP soil parameters and climatic parematers showed that four soil parameters of albedo, interrill erodibility, rill erodibility, and critical shear in six parameters had no effect on predicted runoff result, but initial saturation and effective hydraulic conductivity affected the predicted runoff results. There was no effect of albedo on the hillslope soil loss; other five soil parameters affected simulated results. Among the four parameters related to climate under event prediction, hillslope runoff and soil loss increased with rainfall and decreased with duration time. They increased as maximum rainfall intensity, but after the peak occurrence, they gradually decreased. The impats of the peak occurrence on hilslope runoff and soil loss were relative complex.2)Hillslope runoff and soil loss at different slope degrees under single rain event were simulated by WEPP. The results showed that predicted hillslope runoff increased as slope degree increased, and its increasing scope tended to increase, which indicated WEPP simulated values were sensitive to the gradient change. Measured soil loss had the same trend. Compared with runoff change with slope degree, soil loss change was much more obvious. Model efficiency of soil loss prediction under different gradient slopes (3°, 5°and 8°) was larger than 0.5, which meaned that WEPP simulated results were accepted. WEPP simulated soil loss was better than simulated runoff. Compared model efficency at different gradient slopes, it was found that the simulated value for low slope was better than for steep slope. 3)Hillslope runoff and soil loss at different vegetation under single rain event were simulated by WEPP. The result showed that model efficency of runoff and soil loss was larger than 0.5, which meaned that the WEPP simulated results were accepted. Compared with grass and elm at seedling stage, the simulated results of soybean and alfalfa were better. The predicted runoff values were larger than measured values and the simulated values of soil loss were smaller than measured values.4)Hillslope runoff and soil loss at different tilliage measures under single rain event were simulated by WEPP. Predicted runoff by WEPP was accepted, but predicted soil loss was a little far from the measured values. Model efficiency of runoff prediction for mini- tillage, conventional tillage, and bare land were respectively 0.65, 0.53, and 0.75, which meaned that the prediction result was accepted. Model efficiency of soil loss prediction for non-tillage, mini-tillage, conventional tillage, bare land, and Contour farming were -31.26, 0.10, 0.40, 0.34 and -1.02, respectively, which meaned that the prediction result was not good. WEPP simulated results for mini tillage, conventional tillage, and bare land were better than the other tillages.5)Compared the predicted results of runoff and soil loss using CLIGEN and BPCDGN, the result showed that WEPP simulated results using BPCDG were better than that using CLIGEN。...
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