Reducing in large amounts of incoming sediment to Three Gorge Reservoir——Response on "Discussion on the sediment load for the Three Gorges Reservoir"

According to ref.(1),the series of incoming sediment to TGR is unsufficiently estimated,and thus the safety factor of reservoir is of underdesign.A quite different viewpoint has been provided in this paper.Actually the real value is much less than that estimated in feasibility study.The reason is that the hydrometric series adopted in feasibility study of TGR is larger than the average value.Besides,the sediment discharge outpout from the Jialingjiang river decreases in large amounts in the recent years,and the sediment retained by the Xiangjiaba and Xiluodu reservoirs will reduce the incoming sediment by 230×10~8 t(54.0% of incoming sediment at Cuntan gauge station)and 49.28×10~8t coarse sediment(80.7% of Cuntan) in one hundred years.It is a common sense and can not be contradicted that a series of high dams constructed along Jinshajiang river will trap the sediment in a long term.The reason for that the sediment of Jialingjiang river being on the decrease is revealed in the paper.The author also demonstrates that the accuracy of measured data of coarse particles near the bed layer will not change the total decrease of incoming sediment to TGR.Finally,the evident effect on the sedimentation of large decrease of incoming sediment,especially in the flucturating backwater region has also presented in this paper.