Characteristics of incoming runoff and sediment load in the Three Gorges Reservoir during high flood period after the operation of the cascade reservoirs in the lower Jinsha River

Abstract

泥沙淤积问题直接影响着三峡水库的使用寿命及综合效益的发挥,研究其入库水沙特性对于解决水库泥沙淤积问题具有重要意义。根据水文站实测数据,分析了三峡水库入库水沙输移特性及来源组成变化,重点研究了金沙江下游梯级水库运行后的三峡水库高洪水期入库水沙特性。结果表明:2003-2021年,三峡水库入库泥沙集中于汛期的高洪水期,2013年以后该现象更为显著,泥沙来源也由金沙江为主转变为嘉陵江为主。寸滩站洪峰流量高于50000 m³/s的高洪水期三峡入库沙量显著大于30000~50000 m³/s区间的高洪水期,三峡水库泥沙调度关键在于上游发生编号洪水期间。三峡水库上游沱江或嘉陵江等支流发生流域性大洪水时,易引起高洪水期入库水沙出现“小水大沙”的特点。金沙江下游梯级水库运行后,三峡水库高洪水期入库泥沙大幅减少,中小洪水调度期间泥沙淤积量也大幅减小。研究结果可为三峡水库的泥沙精细化调度和长期高效使用提供基础数据支撑。;The problem of sediment deposition directly affects the lifespan and comprehensive benefits of the Three Gorges Reservoir (TGR). It is of great importance to explore the characteristics of incoming runoff and sediment load in the TGR, which is conducive to solving the problem of sediment deposition in the reservoir. Based on the measured hydrological data, this paper analyzes the flow and sediment transport characteristics and source composition in the TGR, with special emphasis on such characteristics during the high flood period after the operation of the cascade reservoirs in the Lower Jinsha River. The results show that: The incoming sediment load in the TGR was mainly concentrated in the high flood period from 2003 to 2021, and this phenomenon was more significant after 2013. The main source of the sediment load has also changed from the Jinsha River to the Jialing River after 2013. Besides, for the high flood period in which the peak discharge at Cuntan Station was higher than 50000 m³/s, the sediment load in the TGR was significantly greater than those in the peak discharge intervals of 30000-50000 m³/s. The key periods for the sediment regulation of the TGR was during the numbered flood periods in the Upper Yangtze River. Additionally, the basin floods occurred in the tributaries upstream of the TGR, such as the Tuo River or the Jialing River, may cause the phenomenon of “little water carries massive sediment” happened in the TGR during the high flood period. After the operation of the cascade reservoirs in the Lower Jinsha River, the sediment load in the TGR during the high flood period has been significantly decreased, which has greatly reduced the amount of sediment deposition during the middle and small flood operation. This study can provide technical support for the refined sediment regulation of the TGR, and provide a solid guarantee for the long-term use of the TGR.