Variation Characteristics of flow and Sediment Fluxes and Channel Evolution in the Middle Yangtze River
The regime of flow and sediment changed significantly after the operation of the Three Gorges Project(TGP)and its upstream res-ervoirs,which led to intensive channel degradation in the Middle Yangtze River(MYR).Therefore,it is necessary to investigate the tempo-ral and spatial variation characteristics of the flow and sediment fluxes from the main stream and tributaries and channel evolution processes of the MYR.Based on the flow and sediment measurements at the hydrometric stations and the measured channel evolution volume corre-sponding to bankfull level,this study analyzed the temporal and spatial variations of the flow and sediment fluxes and channel evolution pro-cesses in the MYR.The results indicate that:① In terms of temporal variation,the annual runoff of the MYR has not changed much,while the sediment load decreased by 68%～92%after the TGP operation.The water runoff decreased during the flood seasons and increased during the dry seasons.Except for the increase of annual runoff at Xiantao station and sediment load at Hukou station,the annul fluxes of flow and sediment of other tributaries and lakes decreased;② In terms of spatial variation,the longitudinal change of runoff along the MYR did not show any significant adjustments.However,the longitudinal change of sediment load adjusted from a decrease to an increase along the MYR following the TGP operation,and the primary source of sediment changed from the upstream input prior to the TGP operation(accounting for about 120%)to the channel evolution after the TGP operation(accounting for 53%);③ The cummulative erosion volume corresponding to bankfull level in the MYR was 2.63 billion m3 during the period 2002-2020,accounting for about 54%of the cummulative erosion volume in the middle and lower Yangtze River.Especiall,y the Jingjiang Reach suffered the most dramatic channel erosion(accounting for 47%),and the channel erosion center moved from the Yizhi Reach to the Hanhu Reach along the MYR.④ Empirical functions were developed between the sub-reach's cumulative channel evolution volume and the previous five-year average fluvial erosion intensity during flood seasons at the corresponding hydrometric station,with the determination coefficients(R2)higher than 0.8.These relations quantitatively reflect the re-sponse relationship between the longitudinal channel evolution downstream of the TGP to the changes in incoming flow and sediment condi-tions and can be used to quantitatively predict the channel evolution volume of each sub-reach in the MYR under various flow and sediment conditions.
Three Gorges Projectflow and sediment fluxeschannel evolutiontemporal and spatial variationsMiddle Yangtze River
万方数据
维普
