Study On The Sediment Yield Model Of Watershed In Purple Soil Hilly Area At The Northland Of Sichuan

Hemingguan watershed and Lizikou watershed, lying in the Xihe basin which belongs to the Jialing River, were selected as the research area in this paper. An experiential watershed model was built, which based on the sufficient data of Hemingguan watershed. This model was then extended to the adjacent watershed-Lizikou. Main research conclusions are listed:1 Various factors influencing the sediment yield of Hemingguan watershedSeveral main factors, affecting the sediment yield of watershed, including soil, geology, topography, precipitation, runoff, land utilization, changing of field's cover and little irrigation works, were analyzed. The analysis results show that the relativity between rainfall factors, including the combination of precipitation (P) and Intensity of rainfall (I) or Energy of rainfall (E) and Intensity of rainfall (I), and modulus of sediment yield was better than others. The combination of the maximal rainfall intensity during 60 minutes among different rainfall factors is the best one. The relativity between peak runoff and sediment yield is better than other runoff factors. It is various with the content of coarse particles when the relativity reflects the depth of runoff and sediment yield. Different land utilizations led to various relativities of the precipitation and the sediment yield. Contracting with other land utilizations, that of the farm land and barren land is among the best ones, and that of the forests and terraces is the worst ones. The sediment yield on the farm land is various, especially distinct during the flood season.2 Experimental sediment yield model using in purple soil hilly area of the north of Sichuan provinceThe experimental sediment yield model of the second drainage area of Hemingguan watershed is built firstly, and the model includes those factors: coverage of farm land (Fc), precipitation (P) and land utilization (Lu). After eliminating the affection of rainfall, the date of second drainage area and the first drainage area of Hemingguan watershed were analyzed together to get the experimental model which was used in the drainage area of purple soil hilly area of the north of Sichuan. This model includes five factors: coverage of farm land (Fc), precipitation (P), land utilization (Lu), little irritation works (He) and density of ditch (G). The contribution of those factors is various, and that of the precipitation and the land utilization were the greatest ones which reached 0.39 and 0.37.3 Extensional application of the experimental model in Lizikou watershedEight rainfall events of Lizikou watershed is simulated using the experiment model. Because of the affection of the irritation works of the Lizikou watershed, the effect of the early days of the flood season is unreasonable , but the simulation results of other stages of the flood season is acceptable.