澜沧江-湄公河输沙量变化及其影响因素

为了更准确评估澜沧江-湄公河输沙量的变化情况及上游水电开发对下游输沙量变化的影响,从最近几年文献中选择可信的下湄公河各站的年输沙量数据,并根据相关文献整理得出漫湾水电工程坝下第一个水文站点———嘎旧站1965—2003年的年径流和年输沙量系列数据,分析比较澜沧江-湄公河沿程各站的年输沙量变化趋势。结果表明:澜沧江上漫湾水电工程运行后,嘎旧站年输沙量大幅降低,降幅大于60%,但清盛站及其下游各站输沙量未出现与其一致的变化趋势。认为清盛站输沙量的降低量远低于嘎旧站的原因主要是两站间含沙量大的支流汇入、人工经济林取代原始森林等因素造成的流域水土流失和河流含沙量恢复。湄公河入海沙量约为1.45亿t/a,预计未来湄公河入海沙量可能会降低。

Change in sediment loads in the Lancang-Mekong River and its influencing factors

To accurately evaluate variations of sediment loads in the Lancang-Mekong River and influences of its upstream hydropower development on sediment loads in its downstream reaches,the credible data of annual sediment loads at various monitoring stations along the Lower Mekong River are chosen from the existing literatures,and the annual runoffs and sediment loads at Gajiu hydrological station(the first station downstream Manwan Hydropower Station dam on Lancang River) from 1965 to 2003 are yielded.The change trend of annual sediment loads of the Lancang-Mekong River at various stations is analyzed and compared.The results show that the annual sediment loads at Gajiu hydrological station has a dramatical decrease of over 60% after the operation of Manwan Hydropower Project However,the sediment loads at Chiang Saen hydrological station and its downstream stations do not have the consistent change trend.The main causes for the less decrease of sediment loads at Chiang Saen hydrological station than that at Gajiu hydrological station are as follows:confluence of tributaries with high sediment concentration,soil and water losses caused by replacement of natural forest by artificial economic forest,and recovery of sediment content in the rivers.The amount of sediment loads of the Mekong River entering the sea is about 145 million t/a,and it is predicted to be reduced in the future.