基于水蚀预报模型的黄土高原水平阶减流阻蚀效应模拟

黄土高原是我国土壤侵蚀最严重的地区,如何合理开展坡改梯工程对防治水土流失具有重要意义。本研究应用WEPP模型模拟坡面尺度降雨—侵蚀过程,模拟分析径流小区(10 m坡长)在不同坡度的水土流失特征和二阶、三阶水平阶在不同台面宽度(1,1.5,2 m)的减流阻蚀效应。结果表明:1)坡面尺度上,径流量和侵蚀量随坡度增加而增加。坡度达到20°时,径流量随坡度增加保持稳定,产沙量增加趋势渐缓;2)与坡面小区对比,二阶和三阶水平阶随台宽增加对地表径流调控率分别从6.5%增加到61.2%,从10.1%增加到69.7%;二阶水平阶在中(1.0 mm/min)、大(1.5 mm/min)雨强下,台面宽度大于1.5 m时产沙量小于坡面,泥沙调控率从1.1%增加到68.8%,三阶水平阶泥沙调控率从1.4%增加到82.3%;3)依据单位台宽减沙量,合理设计水平阶,使其减沙效益最大化。小雨强(0.5 mm/min)时,二阶、三阶水平阶的台面宽度达到1.5 m和1 m时可发挥优良的水土保持效果;中雨强(1.0 mm/min)时,台宽1.5 m的三阶水平阶效果最佳;大雨强(1.5 mm/min)时,则以2 m台宽的三阶水平阶效果更好。应用WEPP模型为定量评价工程措施的水土保持效益提供技术支撑。

Simulation of the effects of level bench terraces on water erosion reduction in the Loess Plateau based on the WEPP model

The Loess Plateau is the most heavily eroded area in China. It is thus significant to conduct reasonable micro-landform re-establishment measures that can prevent and control soil and water loss. In this study, the WEPP model was used to simulate the rainfall-erosion process at a hillslope scale. The major purpose was to analyze the characteristics of soil erosion on different slopes and the effect of water loss reduction on two and three stages of level terraces (field widths of 1 m, 1.5 m, and 2 m). The following results were captured. First, runoff and sediment yield increased with increasing gradients and precipitation intensities, whereas runoff remained stable and sediment yield increased slowly with increasing gradients before reaching a critical slope gradient (20°). Second, when the field widths increased, the regulation rates of runoff increased from 6.5% to 61.2% and from 10.1% to 69.7%, under medium (1.0 mm/min) and strong (1.5 mm/min) rainfall intensity, respectively. Level terraces with two stages and field width greater than 1.5 m captured less sediment than the slopes. The regulation rates of sediment yield of the two- and three-stage level terraces increased from 1.1% to 68.8% and from 1.4% to 82.3%, respectively. Third, in order to maximize the efficiency of sediment reduction, the table width of level benches should be appropriately designed. When suffering from small (0.5 mm/min), medium (1.0 mm/min), and strong (1.5 mm/min) rainfall, three-stage level terraces with field widths of 1.0 m (1.5 m two-stage level terrace), 1.5 m, and 2.0 m can play prominent roles in water erosion control. By using the WEPP model, the results of this study can provide technical support for quantifying the efficiencies of engineering measures on soil conservation.