金沙江下游水库拦沙效应研究

Study on the sediment interception by reservoirs in the lower Jinsha River Basin

随着众多水库建成运用,水库拦沙成为了金沙江下游减沙的主要原因。1956—2021年金沙江干流及下游支流共修建10万m^(3)以上的水库504座,总库容为687.63亿m^(3)。水库运用后,金沙江下游年径流量不存在明显变化,而年输沙量显著减小。金沙江下游出口含沙量在1998年、2013年以后大幅减小,1956—1997年平均含沙量为1.75 kg/m^(3),1998—2012年平均含沙量减小为1.22 kg/m^(3),2013—2021年平均含沙量减小为0.01 kg/m^(3)。采用双累积曲线法及水库拦沙率公式,分析水库拦沙与水土保持工程对金沙江下游减沙贡献度,结果表明:金沙江下游减沙主要由水库拦沙造成,其中1998—2012年金沙江下游年均减沙0.97亿t,水库拦沙的减沙贡献度为0.67,水土保持工程等措施的减沙贡献度为0.33;2013—2021年下游年均减沙2.43亿t,水库拦沙贡献度为0.97,水土保持工程等措施减沙贡献度为0.03。

With the construction and operation of numerous reservoirs in the lower Jinsha River Basin,sediment retention by reservoirs has become the main reason for sediment reduction.From 1956 to 2021,a total of 504 reservoirs with a capacity of over 1 billion m^(3) were built in the mainstream of the middle Jinsha River and the Yalong River,and in the tributaries of the lower Jinsha River,with a total reservoir capacity of 68.76 billion m^(3).After the operation of the reservoirs,there is no significant change in the annual runoff of the lower Jinsha River,while the annual sediment transport significantly decreases.Sediment concentration in the LJRB has decreased significantly since 1998 and 2013,the average sediment concentration was reduced to 1.22 kg/m^(3) during 1998 to 2012 and 0.01 kg/m^(3) during 2013 to 2021 from the average value of 1.75 kg/m^(3) during 1956 to 1997.The contribution of reservoir sediment retention and soil and water conservation engineering to sediment reduction in the lower Jinsha River was analyzed using the double mass curve method and reservoir trap efficiency equation.The results show that the reduction of sediment in the lower Jinsha River is mainly caused by the retention of sediment by reservoirs.The average annual sediment reduction in the lower Jinsha River from 1998 to 2012 are 97 million tons,with the contribution of sediment reduction by reservoir retention of 0.67 and by soil and water conservation of 0.33.From 2013 to 2021,the average annual sediment reduction are 243 million tons,with the contribution of sediment reduction by reservoir retention of 0.97 and by soil and water conservation of 0.03.