黄土高原丘陵沟壑区单元流域次暴雨输沙模型

黄土高原尤其是黄土丘陵沟壑区土壤侵蚀异常严重,在该区开展单元流域产沙模拟对于流域侵蚀产沙及沟道系统泥沙输移比研究有着重要的意义。本文选取陕北岔巴沟单元流域团山沟为研究对象,利用1961-1969年间水文泥沙资料,构建了流域产沙模型:以流域输沙关系表达式Ms=CsH为理论框架,经分析发现洪峰流量、最大含沙量、平均流量与次洪含沙量相关性显著,近而以洪峰流量、平均流量、最大含沙量及径流深为模型变量,通过模拟误差分析,构建并选取了以径流深和洪峰流量、径流深和最大含沙量为变量的经验模型:Ms=H(109.2ln(Qz)+546.1);Ms=H(Cz-141.2)。与目前已有模型相比,以上模型具有很好的模拟效果,尤其是在模拟小产沙事件时模拟效果较好,模型在临近流域水旺沟上的应用效果也较好。另据研究发现,高含沙水流的存在,使得在不同产沙模数水平下产沙模拟响应机制不同,对产沙模数小于300 t/km2次暴雨事件,流量的对数函数拟合效果明显优于幂函数拟合;对产沙模数大于1000 t/km2次暴雨事件,流量的幂函数拟合效果好于对数函数拟合,但差异不大。

Study on the Sediment Transport Models on Unit Watershed for Single Rainstorm in Hilly Loess Area of the Loess Plateau

The soil loss on the Loess Plateau, especially in hilly loess areas, is among the severest in the world, and it would be of great meaning to study soil erosion and sediment transport as well as sediment delivery ratio in the gully/channel system in the highly erodible region. Though many models have been constructed in the hilly loess region on the Loess Plateau, the models predicted well only for the large runoff-sediment events. On the other hand, although the physical models usually perform better for small events, the data required for the models are so rigorous that it is not easy to apply them for most of the catchments. In our present study, Tuanshangou catchment,a unit-catchment in the hilly loess region on the Loess Plateau, was selected. Using 95 runoffsediment events during the period 1961-1969 and by analyzing peak discharge (Q_z), the maximum sediment concentraion (C_z), mean discharge of single storm (Q_p) and runoff depth (H), five models were constructed given the fact that suspended sediment yield is the function of suspended sediment concentration (C_s) and runoff depth (M_s=C_sH). Then, through analyzing the predicted errors of the models, two models of M_s=H (109.2ln (Q_z)+546.1) and M_s=H (C_z-141.2) had better modeling precision with mean errors less than 19% and 12%, respectively. Both models presented good modeling precision for the events larger than 30 t/km~2, and presented good modeling application for the Shuiwanggou catchment (a neighbored catchment by Tuanshangou catchment).Compared to the previous models, the two models had better modeling results, especially for the small events in the study area. Deep analysis found that, influenced by different flow mechanisms,for the events less than 300 t/km~2, the results modeled by logarithmic function was better than that by exponential model. However, the results modeled by exponential modeling was better than that by logarithmic modeling for the events larger than 1000 t/km~2. The structures of the two models built in this paper are simple, only composing of two variables H and Q_z and H and C_z,respectively. In addition, the model can be applied according to the data acquirement when studying sediment yield in the hilly loess region on the Loess Plateau. The simplicity and easy application of the constructed models would be of assistance in predicting sediment yield (especially for small events) and in constructing soil and water conservation measures in Yellow River basin in the future.