Hydrogen (H) and oxygen (O) stable isotopes are often used to quantitatively calculate the evaporation of water, but traditional isotopic analysis restricts the quantitative estimation of water balance because of its slow measurement. Given the recent availability of data obtained using new technologies for measuring H and O isotopes in water, this paper analyzes H and O stable isotopes of water from the urban watercourse in Shanghai from samples taken in October 2012 and January 2013. The data suggest that water evaporation is about 8.6%in October and only 2.8%in January. Because of evaporation, the mean value of δ18O in October (-6.60‰) is higher than in January (-6.95‰). As a result of the stronger isotopic fractionation in January, the mean value ofδD (-48.04‰) is higher than in October (-49.13‰). The water evaporation line can be expressed asδD=4.4δ18O-16.5, a relationship that can be used to estimate the degree of water evaporation in the dry season (November to April) in Shanghai. The research wil contribute to the quantitative estimation of evaporation and of the water cycle in large reservoirs and lakes, which exchange over a weekly timescale with surface runoff.%氢氧稳定同位素常用于水体蒸发研究，但传统同位素分析手段会明显制约水量平衡的定量估算。基于国际上新发展的液态水氢氧同位素分析技术，分析了2012年10月和2013年1月上海市区河水的氢氧同位素组成。研究发现，10月份河水蒸发量可达8.6%，1月份蒸发量仅为2.8%；受蒸发量的影响，10月河水δ18O平均值（-6.60‰）高于1月（-6.95‰）；而因1月河水的同位素分馏程度高于10月，使δD的平均值（-48.04‰）高于10月（-49.13‰）。河水蒸发线为δD=4.4δ18O-16.5，在一定程度上反映了上海地区少雨季节（11月至翌年4月）流通性相对不畅的水面受蒸发影响的程度。该研究可为定量估算大型水库以及与地表径流交换较弱的湖泊等水体蒸发量和水循环机制研究提供借鉴。
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