Scouring and silting variation in middle and lower channel of the Yangtze river after TGP

After the completion of the Three Gorges Project,conditions for incoming water and sediment of the Yangtze river channel downstream from the Three Gorges reservoir will change,the sediment transport capacity of the river channel will be in an unsaturated state,and river bed scouring will take place along the river channel,which may bring about adjustment of the river regime and have some influence on the flood control.Through computation by mathematic models and analysis of observed data,preliminary researches were conducted on the variation of water and sediment in the middle and lower Yangtze river and related lakes,on the evolution of the river channel degradation and aggradation,and on their influence on the flood control after the completion of the Three Gorges project,research results show that after the impoundment and operation of the Three Gorges project,large amount of scouring will occur in the middle and lower Yangtze river,resulting in lower water levels for same discharges;when the scouring amount for all river reaches is maximum,the average scour depth of the river bed of the Jingjiang river reach will be 2.0～5.3 m,with its channel storage increment of 1.3 billion m~3;and for Chenglingji reach,the average scour depth of the river bed will be 2.5 m,with its channel storage increment of about 0.85 billion m~3;due to the river bed scouring of the stem stream,water and sediment diverted from the Yangtze river into the Dongting lake through the three outlets in the Jingjiang river reach will reduce,resulting in mitigating the sedimentation of the Dongting lake area and increasing the lake's adjustable water storage by 2.38 billion m~3;variation of water and sediment travel process,river bed scouring and local adjustment of the river regime will bring about some influence on the stability of the river channel,and on the safety of the river dikes and revetment works,and corresponding countermeasures should be taken.