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中文摘要：
根据雅鲁藏布江流域2005年干流的拉孜、奴各沙、羊村和奴下4个站点河水中δ18O实测数据以及相关的气象和水文资料，分析了河水中δ18O的变化特征．通过与同期该流域降水中δ18O的比较，初步研究了流域内河水中δ18O的时空分布特征．结果表明：河水中δ18O的变化大致以7月中旬为界划分为两个明显的阶段，前一阶段河水中δ18O呈上升趋势，以相对高值为特征；而后一阶段则呈下降趋势，以相对低值为特征；河水中δ18O的这种季节变化可以很好地被正弦波变化所揭示．从空间上来看，由于受到支流、地下水和蒸发等的影响，河水中δ18O变化比较复杂，在青藏高原夏季季风降水期间，由下游的奴下站至中游的奴各沙站，河水中的δ18O逐渐递减，其由高程效应和水平距离所造成的递减率分别为0．21‰·（100m）^-1和0．45‰·（100km）^-1河水中δ18O变化受到降水中δ18O强烈影响，但其波动远小于降水，在青藏高原夏季季风降水期间，河水中δ18O的平均波动幅度为4．8‰，比流域降水中δ18O的平均波动幅度低了19．7‰．整个流域均到受蒸发的影响，在青藏高原夏季季风降水期间，降水中δ18O的加权平均值为-17．4‰，河水中δ18O的平均值为-16．6‰，造成这种差异的主要原因在于降水和河水中的稳定同位素又通过蒸发发生分馏。
英文摘要：
The variation characteristics of δ18O in river water of the Yarlung Zangbo River basin was studied based on the observations of δ18O in river water at 4 stations （Lhazfe, Nugesha, Yangcun and Nuxia） and related meteorological and hydrological data in 2005. Comparing 9180 in contemporaneous precipitation, the paper presents a primary research result on the temporal and spatial variations of 9180 in river water of the basin. The results show that the variations of δ18O in river water can be divided into two distinct stages by the boundary of mid-July.δ18O in river water exhibits higher value with an uptrend in the former stage and lower value with a downtrend in the latter stage. Seasonal variations of δ18O in the river water can be expressed by fitting with sine-wave regression models. In the view of spatial variations, δ18O in river water is very complex owing to the impact of tributaries, groundwater, evaporation, et al. During the Tibetan Plateau summer monsoon period,δ18O in river water reduces gradually from Nuxia Station to Nugesha Station, and the lapse rate of δ18O in river water is approximately 0.21‰- （100m）^-1 due to the ＂altitude effect＂ and 0.45‰/100km due to the rainout process during the period of moisture transport along the Yarlung Zangbo River valley, respectively. δ18O in river water is strongly influenced by δ18O in precipitation, but the fluctuation amplitude of δ18Ois much smaller in river water than in precipitation. During the Tibetan Plateau summer monsoon period, with average fluctuation amplitude of 4.8‰, δ18O in river water is 19.7‰lower than that in precipitation. The whole basin is affected by evaporation. During the Tibetan Plateau summer monsoon period, weighted average δ18O in precipitation is -17.4‰, but that in river water is -16.6‰, which results from isotope fractionation duo to evaporation of raindrop and river water.
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