1、J.Geogr.Sci.2023,33(3):576-598 DOI:https:/doi.org/10.1007/s11442-023-2097-7 2023 Science Press Springer-Verlag Impact of cascade reservoirs on the delayed response behaviour of sedimentation in the Three Gorges Reservoir LI Xin1,REN Jinqiu2,3,XU Quanxi4,YUAN Jing4,*ZHANG Wei1 1.State Key Laboratory
2、of Water Resources and Hydropower Engineering Science,Wuhan University,Wuhan 430072,China;2.Changjiang Survey,Planning,Design and Research Co.,Ltd.,Wuhan 430010,China;3.Hubei Key Laboratory of Basin Water Security,Wuhan 430010,China;4.Bureau of Hydrology,Changjiang Water Resources Commission,Wuhan 4
3、30010,China Abstract:Delayed response behaviour commonly occurs in conjunction with changes in riv-erbed scouring and sediment deposition and is a key component in understanding the intrin-sic behaviour of reservoir siltation.Due to the complexity of the riverbed siltation process,the variability in
4、 the factors that influence siltation and the limitations of available research methods,the understanding of the delayed response behaviour of the sedimentation process in the Three Gorges Reservoir(TGR)is currently merely qualitative,and there is a lack of quantitative in-depth understanding.In add
5、ition,the effects of changes in water and sediment conditions on sedimentation in the TGR before and after cascade reservoir impoundment have not been quantified,so further studies are needed to provide a reference for better un-derstanding the intrinsic behaviour of sedimentation in the TGR and the
6、 implications for the long-term use of the reservoir.Based on measured water and sediment data from 2003 to 2020 and topographic data from 2003 to 2018,a delayed response model for sedimentation in the TGR is constructed and combined with theoretical derivation to analyse the changes in the delayed
7、response behaviour of the TGR before and after the impoundment of the cascade reservoirs and the associated causes.Then,the influence of changes in water and sediment conditions in previous years on sedimentation in the reservoir area is determined.The results show that(1)the improved delayed respon
8、se model of sedimentation,which considers vari-ations in external water and sediment conditions,reservoir scheduling,and riverbed adjust-ment rates,can effectively reflect the sedimentation process in the TGR,especially after the impoundment of the cascade reservoirs.Additionally,the typical section
9、 elevation delayed response model can simulate the section elevation adjustment process.(2)After the im-poundment of the cascade reservoirs,the decreased variation in incoming water and sedi-ment and more concentrated incoming sediment in the flood season increased the adjust-ment rate of the riverb
10、ed,and the delayed response time of TGR sedimentation was short-Received:2021-11-22 Accepted:2022-06-09 Foundation:National Key R&D Program of China,No.2017YFC0405202;National Natural Science Foundation of China,No.U2040218 Author:Li Xin(1994),PhD Candidate,E-mail:*Corresponding author:Zhang Wei(197
11、9),Professor,E-mail: LI Xin et al.:Impact of cascade reservoirs on the delayed response behaviour of sedimentation in the TGR 577 ened from the previous 5 years to the previous 3 years.The impact of the previous water and sediment conditions is not negligible for the sedimentation process in the TGR
12、,and the cu-mulative proportion of the previous influence reaches more than 60%.(3)The influence of incoming sediment on the sedimentation process and typical section adjustment process in the reservoir area increased after the impoundment of the cascade reservoirs,and the influ-ence of the water le
13、vel in front of the dam on sedimentation remained the largest.Keywords:delayed response model;sediment deposition;Three Gorges Dam;cascade reservoirs 1 Introduction After an external disturbance,a river system starts to respond to the disturbance over a cer-tain period of time(the so-called reaction
14、 time);then,a certain amount of time(the so-called relaxation or recovery time)is required to reach a new equilibrium state through sediment erosion,transfer and sediment flushing(Graf,1977;Simon,1992;Simon and Rinaldi,2006).Consequently,riverbed evolution lags behind changes in water and sediment c
15、onditions.This delayed response phenomenon exists widely in the processes of riverbed evolution and adjustment.Through studies of delayed response behaviour,we can better understand the process of riverbed evolution and the connections between water and sediment changes and riverbed adjustment(Zheng
16、 et al.,2014a).To study the delayed response phenomenon in the evolution of riverbeds,many research-ers have developed various methods.Some researchers have conducted empirical analyses by establishing functional relationships based on measured data(Feng et al.,2005;Wu et al.,2008;Shen et al.,2013).Others have used various rates to simulate the riverbed adjustment process based on observations(Hooke,1995;Simon and Thorne,1996;Kasai et al.,2004;Simon and Rinaldi,2006;Choi et al.,2017)or applied a
