Abstract: An united calculation on the scour-sedimentation variation of the middle-lower reaches of Yangtze River and the Dongting Lake region after Three Gorges Project (TGP) being completed is performed by a 1-D suspended sediment mathematic model. Based on these study results, the effects of different regulation schemes, in which the sluices of the river entrances at Songzi and Ouchi located in the Jingjiang River reach will be or not be built, on the scour-sedimentation of Yangtze River and Dongting Lake and on the partition of runoff and sediment at the Three Entrances were analysed. The research results show that, after the sluices being built, the amount of diverted water and sediments through Three Outlets will be decreased, among them the decrement at the entrance of Songzi is the greatest; it has a little effect on the scour-sedimentation of the Yangtze River main stem; the diverting channel of Songzi-entrance will be deposited; and the deposited amount of Dongting Lake will be visibly reduced.

Key words: TGP , building sluices of Jingjiang Four-outlets , united calculation for river-lake , scoursedimentation of river bed , diverted amount of water and sediment through Three Outlets