Abstract:

The analysis on rainfall along the ZuliRiver valley in the past 50 years shows that rainfall decreased with latitude but increased with altitude in the northeastand southern areaswhere the altitude varies suddenly. The rainfallwas90-140mm less in an areawhich shape likes a tougue extending from northwest to southeast till the east edge in themiddle and lower area ofZuliRiver compared with otherareas. In the past50 years, the regional rainfall in ZuliRiverbasin decreased 106. 4mm on average. Waveletanalysis shows thatmore than 25 years and about10 years periods in rainfall change are remarkable.The regionalmean rainfall decreased from the late 1960s, and in 1986 it increased but after that itdecreasedmuch quickly. On the otherhand, the seasonal rainfalldistribution there was different, and itwas themost in summer, less in spring and autumn and the least inwinterwith 55%, 21% and 3% of annual rainfal,l respectively. The rainfall in autumn decreasedmuchmore in the past50 years, but it tends to increase in the beginning of this century. Influenced by human activities, rainfall there presented accelerating decrease trend because of excessive cultivation in themiddle and lower region andmany smallwater conservancies in the upper of the river. The rainfalldecreased slowlywhere vegetation cover increased and human activities influenced less on land surface.

Key words: ZuliRivers basin, rainfall variation, human activities, influence

摘要：

对祖厉河流域近50 a降水资料的分析结果表明:祖厉河主流域区等降水量线纬向分布特征明显,降水量随纬度增高而减少;在流域南部和东北部高度差大的地方,降水量随高度增高而增加;受地形影响,祖厉河中下游有一条干舌自西北向东南伸到流域东部边缘,与周边区域相比,干舌区降水偏少90~140 mm。近50 a祖厉河流域降水显著减少,区域平均减少106. 4 mm。小波分析表明, 25 a以上和10 a左右的降水变化周期很明显,目前处于偏少期;区域平均降水量从20世纪60年代后期开始减少, 1986年发生了突变,之后迅速减少。流域内降水季节分配很不均匀,夏季降水最多,占年降水的55%,春、秋季均占年降水的21%,冬季占年降水的3%;春、夏季降水减少不显著,秋季降水减少显著,但进入本世纪,秋雨开始增多,冬季降水有不显著的增多趋势。中下游过度垦殖及河流源头过多的小水利工程等人类活动造成地表状况变化,降水有加剧减少的迹象;流域外大量调水虽然对降水不足有相当的补偿作用,但地表调水显然没有使流域内的天然降水量增加;地表植被增加和人类活动对地表影响较小的区域降水减少比较缓慢。

关键词: 祖厉河流域, 降水变化, 人类活动事件, 响应