黄河兰州以上地区近期天然径流量变化分析

Analysis on Change Characteristics of Recent Runoff in Area above Lanzhou of the Yellow River

根据黄河上游兰州以上地区1955～2003年天然径流量资料,统计分析了近期径流量的变化特点,结果表明:①近期各区年和汛期径流量均较前期减少,尤以洮河、玛曲～唐乃亥区间最甚;②近期年内各月径流量均较前期减小,7～12月减少达20%～38%;③全区年径流总量中,吉迈～玛曲来水量所占比重前期、后期都最大达到30%以上;④全区近期最大月径流量都较前期明显减少,洮河、湟水和玛曲～唐乃亥区间减幅达40%以上,7、8月出现最大月径流量的频率增大,较常年偏大15%以上;⑤出现最小月径流量的频率增大,7、8月份增大28%～38%;⑥全区年内最大与最小月径流量的差值减小趋势比较明显。

The change characteristics of recent runoff were statistical analyzed according to natural runoff data above Lanzhou station of the Yellow River upper reach between the year of 1955 to 2003. The results showed： ①Recent runoff in year and flood season from each area reduced, especially in Taohe and Maqu-Tangnaihe area; ②Recent monthly runoff reduced, runoff of July to December decreased 20% to 38%; ③Speaking of the yearly total runoff of the entire area, the proportion of Jimai and Maqu is 30% and the first in past period and recently. ④Reeent the monthly maximum runoff decreased obviously , Taohe.Huangshui and Maqu-Tangnaihe area were the decrease reached above 40%, in July and August the frequency of the monthly maximum runoff was increased, which was above 15% more than normal; ⑤the frequency of the monthly minimum runoff was increased too, which reached 28% to 38% in July and August; ⑥The annual runoff range in the entire area decreased the reduced trend is obvious.