四川紫色土地区鹤鸣观小流域分布式侵蚀产沙模型

A distributed model of soil erosion and sediment yield for Hemingguan watershed in the purple soil area of Sichuan

从四川省南部县鹤鸣观小流域Ⅱ号支沟为研究区,构建了适合紫色土地区小流域分布式侵蚀产沙模型。该模型以20m×20m栅格为空间步长,以10min为时间步长,定量分析鹤鸣观小流域Ⅱ号支沟水土流失程度,模拟了各时段每个栅格次降雨侵蚀产沙过程,计算了每个栅格次降雨径流量、侵蚀量与沉积量,并且运用递归算法计算出整个流域次降雨侵蚀产沙量,模型能够评价流域下垫面各因子空间分布不均匀性和人类活动的影响。在鹤鸣观小流域Ⅱ号支沟进行了模型的检验,模拟过程与实测结果符合较好。

The area of the Sichuan Basin is 1.58 × 10^5km^2 and purple soil is the dominant soil type in the hilly areas of the basin, but the area of soil and water loss is 7.71 × 10^4km^2, and the lost surface soils are up to 3.77 ×10^6 tons annually. Because the erosion models in China are almost empirical and the research regions mainly focused on the Loess Plateau, it is difficult to popularize such models. This paper took Hemingguan watershed of Nanbu County in Sichuan Province as a case and constructed a distributed model for soil erosion and sediment yield according to the aggravation status of soil and water loss in the purple soil region. This model takes grid as calculated unit with a resolution of 20 re×20 m. It takes 10 minutes as a time-step, simulates runoff and erosion process of rainfall in each cell, calculates the amount of runoff, erosion and sedimentation in each cell, and finally, calculates runoff and erosion of the whole watershed by recursion algorithm for single rain event. Moreover, the model can quantitatively analyze the degree of soil and water loss and evaluate the effect of variation of land use, water conservation measures and support practice on runoff. The model was finally validated in Hemingguan watershed, and the results showed that the proposed model could reasonably simulate rainfall-runoff and erosion in the watershed. This model considered the effect of soil and runoff by other ceils and used stream power to simulate the modulus of erosion. By the way, the model considered slope factor and the effect of vegetation coverage on erosion and roughly calculated the gully erosion. So, the mechanism of the model is impersonal. Furthermore, the parameters of the model can be easily obtained and the computer manipulation is simple. The model can be applied to similar watersheds （i. e., with similar climate and conditions of underlying surface） and the structure or principle of the model can be used as a reference to other regions.