基于δ^(18)O的青藏高原中部错那湖湖水蒸发研究

Estimation of Evaporation from Cona Lake in the Central Tibetan Plateau Using an Isotope-based Method

稳定同位素方法经常被用来估算湖水水量平衡,这种方法主要依赖于水样的采集和同位素分析,并结合研究区域相关的气候和水文信息对湖水进行研究。基于对1999—2001年期间获得的18个湖水样的稳定同位素分析,发现错那湖水δD和1δ8O的平均值分别为-83.3‰和-9.6‰,显著高于流域内同期降水中δD和1δ8O的加权平均值-124.5‰和-16.6‰;流域内湖水稳定同位素的变化幅度远小于降水,但展示了明显的季节变化,夏季值较低而冬春季值较高,这种变化表现出一定的降水量效应,表明降水是湖水主要补给来源之一。结合所获得的流域内降水和河水稳定同位素数据,利用稳定同位素质量平衡方法对非结冰期间错那湖水的蒸发与流入比率(E/I)进行了估算,结果表明,受太阳辐射与气温升高的影响,湖水受到强烈的蒸发,流入错那湖的水大约24%消耗于蒸发。

The isotope-based methods are often used for estimating water balance of a lake. Such isotope-based methods, which primarily rely on water sampling and isotopic analysis, require regional background information about meteorology and hydrology. Based on the isotopic analysis of 18 surface water samples from Cona Lake for the years 1999-2001, the mean values of δ^18O and δD are -9. 6‰ and -83. 3‰ respectively, which are significantly higher than the amountweighted averages （ - 16. 6‰ for δ^18O and - 124. 5‰ for δD）. Despite of lower fluctuation range than precipitation, lake water isotopes show comparatively clear seasonal variation, with the lower values in summer and higher values in spring and winter. Such seasonal variations display some amount-effects, which reveal that precipitation is one the of main recharge sources of lake water. Coupled the isotopic composition of precipitation and river water in the basin investigated, the water balance （E/I） of Cona Lake during the ice-free period was estimated using an isotope mass balance model. The result shows approximately 24% of the water flowing into Cona Lake disappeared due to evaporation.