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三峡水库对坝下游河道调整的影响已初步显现,利用1987 ～2014年长江中游原型观测资料,以河段作为研究单元,探讨了三峡水库蓄水后坝下游河床形态调整时空差异性及成因,研究表明:(1)坝下游河床整体为冲刷趋势,且主冲刷带下移约80km,175m蓄水以来宜昌—枝城及下荆江河段冲刷强度减弱,上荆江、城陵矶—湖口河段增强;(2)宜昌—城陵矶河段冲刷集中在枯水河槽,且集中程度增加,低滩和高滩冲刷所占比例减小;(3)城陵矶—汉口河段由试验性蓄水前的“冲槽淤滩”转为试验性蓄水后的“滩槽均冲”,汉口—湖口河段蓄水前为“冲槽淤滩”,蓄水初期深槽和低滩冲刷,高滩淤积,试验性蓄水期后为深槽冲刷,高、低滩均略有淤积;(4)试验性蓄水后坝下游中枯水历时增长,冲刷集中在枯水河槽,滩地因高水历时减少和航道整治工程等作用,冲刷速率减小或略有淤积;(5)砂卵石河段断面调整以深蚀为主,砂卵石—沙质过渡段深蚀过程中伴随横向展宽,沙质河段整体为深蚀趋势,伴随边心滩冲淤调整,其展宽、束窄均有发生.“,”Since the impoundment in June 2003,the TGR has experienced the cofferdam impoundment stage,initial impoundment stage and experimental impoundment stage and its effects on the changes of downstream flow and sediment and channel landforms gradually show.The original measured data of 1987 ～ 2014 and downstream human activities were used in this study to analyze the spatial and temporal changes of downstream flow and sediment fluxes and channel landforms.The results showed that:(1) After the impoundment of the TGR,the downstream channel showed an overall erosion trend;after the experimental impoundment stage,erosion intensity over unit channel length decreased in the Yichang-Zhicheng and the lower Jingjiang River sections but tended to increase in the upper Jingjiang River and the Chenglingji-Hukou sections;and the maximum erosion zone of unit channel length in the experimental impoundment period moved downstream for about 50km;(2) After the impoundment of the TGR,erosion in the Yichang-Zhicheng,upper Jingjiang River and lower Jingjiang River sections occurred mainly in channel sections of low water levels,and this was especially so after the experimental impoundment with erosion in low and high shoals taking up a less proportion;(3)In the Chenglingji-Hankou section,“ erosion at channels and deposition at shoals” before the experimental impoundment changed to “erosion at both channels and shoals” after the experimental impoundment with slight deposition at high shoals due to channel training works;in the Hankou-Hukou section,“erosion at channels and deposition at shoals” before the impoundment changed to erosion at deep channels and low shoals and deposition at high shoals at the initial stage of the impoundment and then to erosion at deep channels and deposition tendency at both low and high shoals due to channel training works after the experimental impoundment period;(4) Due to water shortage in duration increased,experimental water after washing concentrated in the low flow channel,flat part due to decrease the lasting period of high water and waterway regulation engineering,scour slow or slightly deposition;(5)Riverbed cross-section changes were influenced by water level lowing and riverbed composition;the sandy gravel section saw mainly deep erosion,the sandy gravelsandiness transition section saw deep erosion accompanied by crosswise expansion while the sandiness section saw an overall deep erosion trend accompanied by erosion and deposition changes in point and channel bars with alternate occurrence of crosswise expansion and narrowing.