黄河源区径流变化及原因分析

采用斯波曼秩次相关法分析了黄河源区20世纪60年代以来径流变化情况,并从降水、气温、下垫面等影响因素探讨了黄河源区径流变化原因。结果表明:①黄河源区的径流年际变化从60年代以来有明显的阶段性变化,从年内变化来看,唐乃亥站的汛期和非汛期径流量占年径流量的比例也具有阶段性变化,从80年代中期到90年代末,汛期径流量占年径流量的比例一直减少,非汛期径流量所占比例一直增大。②过去40多a来,玛多站年降水量呈现出缓慢上升的趋势,玛曲站则呈现出下降的趋势;从降水年内变化来看,雨季降水量占年降水量的比例呈减少趋势,旱季降水量占年降水量的比例呈增加趋势。因此,黄河源区降水量的变化是影响径流变化的主要原因,90年代小雨多、降雨历时长是导致径流减少的另一个原因。③黄河源区径流的变化,特别是90年代径流量的偏小和气温的直接关系不大。④植被覆盖面积的变化并不是引起径流减少的原因。

Analysis on Variations of Runoff and Reasons of Headwater Region of the Yellow River

The paper analyzes the runoff variation of the headwater region of the Yellow River since 1960's by using Spearman's rank correlation method and approaches the reasons of variation based on the affecting factors of precipitation,temperature and underlying surface.The outcomes show that a) the interannual variation of runoff in the headwater region of the Yellow River has notable changes in phases since 1960's.Viewing the variation within a year,the proportion of runoff in flood season and non-flood season of Tangnaihai Station making up the annual flow also changes by phases.The proportion of flood season runoff in annual flow is reduced continuously and the proportion of that in non-flood season increased continuously from the middle of 1980's to the end of 1990's;b) during the past 40 years,the annual precipitation of Maduo Station is in a trend of slow increase while Maqu Station is in a tendency of decrease.Viewing from the point of variation within a year,the proportion of precipitation of rainy season in annual precipitation is in a trend of reduction and that of dry season is in a tendency of increase.Thus,the variation of precipitation of the headwater region of the Yellow River is the main reason of affecting runoff variation and more light rain and long duration occurred in 1990's are another reason for runoff reduction;c) the runoff variation of the headwater region of the Yellow River,especially the smaller runoff occurred in 1990's is not closely related with the temperature and;d) the variation of coverage area of vegetation is not the reason for runoff reduction.