老挝南乌河径流变化规律及对降水的滞后效应

Runoff variation trend of Nam Ou River in Laos and its hysteresis to precipitation

为分析南乌河径流变化规律,以湄公河支流南乌河流域孟威水文站和风沙里等4个气象站的实测降水、径流数据为基础,采用集中度、集中期等指标分析了径流量对降水的滞后效应及其原因,利用Mann-Kendall非参数检验法对南乌河年径流变化趋势进行了分析。结果表明:南乌河径流主要集中在6~11月,集中期相对降雨的滞后时间为1月有余;流域内岩溶和基岩裂隙地下水富水区的广泛分布和植被的发育,加大了汛前径流对降水的滞后效应; 1987~2015年径流丰枯交替,上升趋势较小,降水比径流变化更为稳定。

To analyze the runoff variation trend and hysteresis to precipitation of the Nam Ou River,a tributary of the Mekong River in Laos,based on the observed precipitation and runoff data from Meuang Ngoy hydrological station and4meteorological stations in the basin,the indexes of concentration degree and concentration period were used to analyze the runoff hysteresis to precipitation and the cause.Mann-Kendall test was used to analyze the annual runoff variation trend.The results showed that the annual runoff of the Nam Ou River mainly concentrates during June to November and the hysteresis period is more than a month;the hysteresis effect before flood season is enlarged because the extensive distribution of rich karst and fissure ground water areas;wet year and dry year emerges alternatively from1987to2015with a slight rising trend,the precipitation variation is more stable than runoff.