黑河上游河水中δ^(18)O季节变化特征及其影响因素研究

Seasonal Variation of δ^(18)O in River Water in the Upper Reaches of Heihe River Basin and Its Influence Factors

根据2006年5月至2007年5月间在黑河上游莺落峡、祁连和扎麻什3个水文站等地点所采集的河水与降水样品,重点分析了其中的δ18O变化,揭示出黑河干流上游山区河水中δ18O具有夏季高冬季低的季节变化特征,这种变化特征主要受控于降水中δ18O的变化.祁连水文站河水中δ18O月平均值与月平均流量乘积和该站降水中δ18O加权月平均值与月降水量乘积之间存在着高度相关性,从同位素示踪的角度说明降水是黑河干流上游山区径流的主要补给来源.进一步的研究表明,黑河上游祁连山区降水中δ18O变化存在明显的"海拔效应",并且3个水文站点河水中δ18O值均低于其降水中δ18O值,这表明上游径流主要形成于高海拔山区.根据黑河出山口莺落峡水文站河水中δ18O值以及上游山区降水中δ18O的"海拔效应",估计黑河干流出山径流主要形成于海拔3 350~4 600 m之间的高山地区,该高度区域对应的植被带主要为亚高山灌丛草甸和高山寒漠草甸.

During the period May 2007, precipitation and of May 2006 through river water samples were collected at Yingluoxia, Qilian and Zhamashi Hydrological Stations and other sites in the upper reaches of the Heihe River. By analysis of δ18O in these samples, it was found that the variation of δ18O in river water displayed seasonal characteristics with high values in summer and low values in winter. These characteristics were mostly related with the variation of δ18O in precipitation in the Qinlian Mountains. A high correlation exists between the values of monthly mean δ18O in river water multiplied by monthly mean discharge and that of monthly precipitation-weighted mean δ18O in precipitation multiplied by monthly precipitation amount at Qilian Hydrological Station. This indicates that precipitation is the basic basic for the mountainous runoff. Moreover, the ＂ altitude effect＂ in δ18O in precipitation was found in the middle of Qinlian Mountains, where the upper reaches of the Heihe River is situated. At the three hydrological stations, the mean δ18O in river water was lower than δ18O in precipitation over the study period. This implied that the mountainous runoff was formed in high elevations. Based on the mean δ18O in river water at Yingluoxia Hydrological Station, which is just located at the foot of the Qilian Mountains, and the ＂altitude effect＂ in δ18O in precipitation, it is estimated that the mountainous area ranging from 3 350 m a.s. l. to 4600 m a.s.l., which corresponds to the sub-alpine shrub-grass- land vegetation zone and cold-desert alpine meadow vegetation zone, is the major area for the formation of the mountainous runoff.