摘要
近年来,澜沧江干流水电开发的跨境水文效应一直是关注的焦点,但过去的相关研究多数都是分离的,国外集中在下湄公河流域,国内的集中在澜沧江流域,上下游关联的研究极少,且研究结果差异极大,相互之间结论矛盾。本文利用上湄公河三个主要干流水文站1960～2003年多时间尺度的水位记录/实测值,定量分析上湄公河干流沿程水位过程的多尺度关联及其对梯级水电开发的响应。主要结论如下:①旧州站和允景洪站的年平均、汛期平均、以及3～4月平均水位受到了大尺度环境变化(如气候变化、太阳黑子活动等)的影响,40余年来表现出了较为显著的上升趋势;②电站建设期间,三站年平均、年最高以及汛期平均水位的年代际变化和年际变化趋势相似;③电站建设运行期间,电站下游的戛旧站和允景洪站3～4月平均水位表现出了逐步上升的趋势,而上游的旧州站则表现出了相反的下降趋势;④现存电站建设运行对下游年/月尺度上的平均值水位变化影响不明显,对日变化和瞬时水位变化影响相对明显。
Environmental changes and their transboundary influences on the Mekong watercourse system have been an international research focus in recent years, but the opinions and results related to the impacts of upper Mekong River dams are quite different.In this paper,based on the records of water levels from 1960 to 2003 at three mainstream sites in the upper Mekong River,a quantitative examination has been undertaken into characteristics of the mainstream waterlevel process at multiple timescales and its response to cascade development. The major results are:i) Annual mean,wet period mean,and the mean water levels during the period between March and April (PBMA period) exhibit a significant increasing trend at Jiuzhou and Yunjinghong sites,which are influenced by large-scale factors such as limate change and solar activity,ii) The interdecadal and nterannual variations of annual mean,annual maximum, nd wet period mean water levels at three sites show imilar features during the dam construction period,iii) The interdecadal variations of PBMA period water level show a gradual increase at Gajiu and Yunjinghong sites but a falling trend at Jiuzhou;these trends confirm that there is some regulation on the flow in the dry season caused by the two existing dams,iv) The downstreameffects of the present dams on water levels are very limited at the annual mean and wet season mean levels,not apparent at the monthly and yearly timescales,and relative significant at daily and hourly timescales.
