中文摘要：

定量研究上游水库拦沙效应是揭示三峡入库水沙条件变化的关键之一。本文分析了长江上游12000多座水库拦沙对三峡水库来沙量减少的影响,并预测在建、拟建水库运行后三峡入库沙量变化趋势。结果表明,1991-2005年三峡上游水库群年均拦沙约18000万t,其中嘉陵江和金沙江流域水库群的年均拦沙量分别为6010万t和5000万t,占总拦沙量的33.8%和27.7%;1991-2005年三峡上游水库群拦沙年均减少三峡入库沙量为11000万t,与1990年前相比,年均新增减沙量为9510万t,占三峡入库总减沙量的59.9%。长江上游近期拟建大型水库运行后,三峡入库沙量将减至9030万t/a,仅为1956-1990年沙量的18.3%。

英文摘要：

Construction of reservoirs in the upper Yangtze River（Changjiang） has great impact on the incoming flow and sediment conditions of the Three Gorges reservoir（TGR）.This paper analyzes the impact of 12000 reservoirs in the upper Yangtze on the sediment inflow to TGR,and predicts the trend of incoming sediment for the case of all the cascade reservoirs at their operation stage.Results show that about 180 millions ton（Mt） of sediment was trapped annually by these reservoirs in 1991-2005 and that about 60.1 Mt /yr and 50 Mt /yr or 33.8% and 27.7% of the total trapped was retained in the Jialing River basin and the Jinsha River basin,respectively.The sediment detention had reduced the TGR incoming sediment by 110 Mt /yr in 1991-2005.Relative to that before 1990,the reduction was increasing by 95.1 Mt /yr on average,or the total reduction in the TGR incoming sediment in this period was increased by 59.9%.With the planned large reservoirs at their operation stage in the near future,the sediment discharge to TGR would most likely be decreased to 90 Mt /yr,which is only 18.3% of the amount observed during 1956-1990.