近45年来长江上游通天河径流量演变特征及其气候概率预报

利用长江上游通天河流域直门达水文站1957～2001年各月平均径流量资料,对长江水系通天河的径流量变化规律及与气候要素的关系进行了分析.结果表明,通天河月平均流量具有很好的持续性,尤其是7～12月,其显著落后自相关可达4～6个月以上;近45年来,通天河流量经历了小-大-小的演变过程,期间出现过径流量的多次转折,其中1967年由大变小,径流量持续减小直到1979年,长达11年;1979年径流量由小变大,直到1989年达到历史(有记录以来)最大值,持续时间长达10年;1990年代径流量持续减小;从1998年开始,径流量又开始表现出增大趋势;年径流量表现出较明显的准2年短周期和7.5及12.3年的长周期变化;年平均径流量与同期6～9月降水存在显著的正相关关系,与气温关系不显著.对径流量丰枯划分的标准不同,进行径流量转移概率的预报结果也不同.

Features of Runoff in the Upper Reaches of the Tongtian River and Its Climatic Probobility Forecast in Recent 45 Years

A diagnostic analysis has been performed to investigate the features of runoff in the upper reaches of the Tongtian River and its relationship with climate changes in recent 50 years by using the data of monthly mean runoff of Zhimenda hydrometric station from 1957 to 2001. It is shown that there is a good persistence for months from August to December respectively, their significant lag correlations can last more than half a year. In recent 50 years, the runoff in the Tongtian River underwent a low-high-low process, during which there were several obvious abrupt transformations of runoff. There are two continuous decrease phases of annual runoff in the periods of 1967 to 1979 and the 1900s respectively. It is an increasing phase of annual runoff from 1979 to 1989. From 1998 on wards, it appears to be an increase trend. The annual runoff in the Tongtian River has obvious periodicities of quasi-2, 7.5 and 12.3 years. Precipitation over the Tibetan Plateau in summer and autumn have obviously contribution to runoff at the same season and lag half year, while air temperature has less impact on runoff. The result of probability forecast is different if the criterions of the high-low flow year of the river are different.