金沙江梯级水库群下游河道河床冲刷分析

Analysis of River Bed Scour Downstream from Dams of Cascade Reservoirs in the Lower Jinsha River

摘要: 金沙江下游是长江流域的重点产沙区，自2012年开始，下游的乌东德、白鹤滩、溪洛渡和向家坝四个梯级水库陆续蓄水运行，截断了金沙江下游的泥沙，水库群下游向家坝坝址至江津河段发生冲刷，河床下切导致同流量中低水位下降，可能对下游河道的水生态环境及通航造成影响。基于金沙江下游的水沙和河道地形、断面等观测资料，围绕金沙江下游梯级水库蓄水对水沙条件的影响和向家坝下游河道河床冲刷两个主要内容进行分析，结果表明，自2012年向家坝水库开始蓄水，金沙江下游出口沙量骤减幅度超过90%，向家坝坝下游至江津河段河床发生冲刷，累计冲刷量为1.516亿m³，河床冲刷导致枯水位下降0.41 m。

Abstract: The lower Jinsha River is a key sediment producing area in the Yangtze River basin. Four cascade reservoirs at the lower reaches, Wudongde, Baihetan, Xiluodu, and Xiangjiaba, have been successively impounded and operated since 2012, thus cut off the sediment at the lower Jinsha River. The reach from the reservoir group downstream Xiangjiaba damsite to the Jiangjin River has been scoured, and the cutting down of the riverbed has led to the lowering of the middle and low water levels at the same flow, which may have an impact on the aquatic ecological environment and navigation of the downstream river channels. Based on the observation data of water and sediment, river channel topography and cross section in the lower Jinsha River, the impact of water storage in cascade reservoirs in the lower Jinsha River on water and sediment conditions and river bed scouring downstream from the Xiangjiaba Dam to Jiangjin are analyzed. The results show that since Xiangjiaba Reservoir began to store water in 2012, the sediment amount at the outlet of the lower Jinsha River has decreased by more than 90%, and the river bed in the lower reaches of Xiangjiaba River to Jiangjin River has been scoured, with a total scouring amount of 151.6 million m³, the low water level drops by 0.41 m due to river bed scouring at Xiangjiaba hydrometric station.