长江上游降水变化及其对径流的影响

利用长江上游地区60个国家基本、基准站1960年-2009年的月降水量资料和干流区屏山、寸滩和宜昌3个水文控制站同期径流资料,分区域对长江上游地区的降水量、径流量变化趋势以及降水量和径流量的相关性进行了分析.主要结论如下:①年降水量呈上升和下降趋势的气象站点空间分布相对集中,分别分布在屏山站以上流域和屏山站以下流域；屏山站以下流域和整个长江上游地区年降水量近50年呈现下降趋势,屏山站以下流域秋季降水量的显著减少是长江上游年降水量减少的主要原因；②整个长江上游月降水量趋势从1月-7月以上升趋势为主逐渐转变到8月-12月以下降趋势为主,且月降水量变化趋势空间分布有从3月份至9份月由屏山站以下流域开始逐渐向长江源头过渡的趋势,到9月份整个长江上游基本呈减少趋势；③与降水量变化趋势基本一致,屏山站以下流域寸滩和宜昌站年径流下降趋势显著的主要原因是5月-11月径流的减少,且秋季下降显著,而屏山站春、夏、冬和年径流呈上升趋势,且春季和冬季上升趋势很显著；④整个上游地区面雨量与径流量具有很好的相关性,同期面雨量与径流量在月、季和年尺度上相关性都较显著.屏山以上流域隔月相关比同期相关性强.

Rainfall and Runoff Trends in the Upper Yangtze River

Spatiotemporal monthly rainfall-runoff analysis is the foundation of water regulation, water resource protection and management,and drought and flood hazard prediction. Previous studies of the Yangtze River have mainly focused on the whole river basin and seasonal or yearly rainfall and runoff analysis. Here,rainfall records from 60 national basic and reference stations, and hydrological data from three control stations of the upper Yangtze River were used to analyze rainfall and runoff characteristics across the upper Yangtze River. First,the spatial distribution of weather stations with upward and downward trends for precipitation were comparatively concentrated. Weather stations with an upward trend were located in the Sichuan Basin above the Pingshan Hydro station(PA region),while weather stations with a downward trend were mainly located in the rest of the upper Yangtze River(PR region). Annual precipitation in the upper Yangtze River has declined in the last 50 years. Second,monthly precipitation trends show that more than half of weather stations experienced upward trends in eight months(Jan-Aug). The spatial distribution of monthly rainfall shows a transition from the PA region to PR region between Mar-Sep. Runoff shows a similar trend to rainfall and an indistinctively upward trend in Pingshan station,and a downward trend in Cuntan and Yichang stations. The decrease in runoff in the PR region from May-Nov is the main reason for the runoff drop seen at the Cuntan and Yichang stations. Runoff in the PA region shows an upward trend in all seasons except autumn,especially in spring and winter. A good correlation was found between area rainfall and runoff in the upper Yangtze River.