Abstract:

Surface water evaporation plays a crucial role in regulating regional microclimates and facilitating water exchange. As the primary inflow rivers to Lake Ebinur, the Bortala River and the Jinghe River warrant investigation into the spatiotemporal heterogeneity of their water evaporation. This research holds significant implications for enhancing water resource management and optimizing water use strategies in the region. To elucidate the spatiotemporal heterogeneity of hydrogen and oxygen stable isotope compositions in inflow river water and evaporation ratios, samples of inflow river water, groundwater, and lake water were collected from July to August 2022. Stable isotope techniques were employed to analyze the spatiotemporal distribution patterns of δ ²H and δ ¹⁸O. The Rayleigh fractionation model and isotope tracer method were used to quantitatively assess water evaporation fractionation ratios, while the HYSPLIT backward trajectory model was coupled to trace water vapor transport pathways in the study area. The results indicate: 1) Overall, the variation ranges for δ ²H and δ ¹⁸O in inflowing rivers were −81.8‰ to −58.8‰ and −12.06‰ to −9.27‰, respectively. Hydrogen and oxygen stable isotope compositions along the Bortala River exhibited an enrichment trend downstream, while those in the Jinghe River remained stable overall. 2) Groundwater δ ²H and δ ¹⁸O values ranged from −85.0‰ to −58.9‰ and −12.44‰ to −9.31‰, respectively. Hydrogen and oxygen stable isotope compositions in groundwater from the middle and upper reaches of the Bortala River were more enriched than those in the lower reaches, while Jinghe groundwater exhibited an increasing trend along the flow path. 3) The mean LC-excess values for the Bortala River and Jinghe River gradually decreased along the flow path in July and August, while the evaporation fraction showed an increasing trend along the flow path. The average evaporation fraction for the Bortala River during these two months was 41.1%, while that for the Jinghe River was 45.4%, and the average evaporation fraction for Lake Ebinur water was 15.4%. Overall, based on river water evaporation fractions calculated using δ ¹⁸O, Jinghe exhibited the highest evaporation fraction, followed by the Bortala River, with lake water showing the lowest. 4) The HYSPLIT model revealed that during the sampling period in July, water vapor in the study area primarily originated from westerly winds and Arctic Ocean air masses. In August, water vapor mainly came from mid-to-high-latitude Siberian air masses. Precipitation in the study area was predominantly transported by water vapor carried by westerly winds.

Key words: Ebinur Lake, Hydrogen and oxygen stable isotopes, River water evaporation, LC-excess, HYSPLIT model

摘要：

地表水体蒸发在区域小气候调节和水分交换等方面发挥着重要作用。博尔塔拉河与精河是艾比湖主要入湖河流，研究其水体蒸发的时空异质性对于加强该区域水资源管理、优化用水策略具有重要意义。为阐明入湖河水氢氧稳定同位素组成与蒸发比例时空异质性，于2022年7－8月采集主要入湖河水、地下水及湖水样品；基于稳定同位素技术解析氢氧稳定同位素组成的时空分布格局，采用瑞利分馏模型和同位素示踪法定量评估水体蒸发比例，并耦合HYSPLIT后向轨迹模型追踪研究区水汽传输路径。研究结果表明，1）整体上入湖河水δ ²H和δ ¹⁸O值的变化范围分别为−81.8‰－ −58.8‰和−12.06‰－ −9.27‰，博尔塔拉河氢氧稳定同位素组成沿流程呈现出富集的趋势，而精河氢氧稳定同位素组成整体较稳定。2）地下水δ ²H和δ ¹⁸O值的变化范围分别为−85.0‰－ −58.9‰、−12.44‰－ −9.31‰，博尔塔拉河中上游地下水氢氧稳定同位素组成较下游地区更加富集，而精河地下水氢氧稳定同位素组成沿流程而递增。3）博尔塔拉河与精河在7、8月上中下游的LC偏离程度（LC-excess）均值沿流程逐渐减小，蒸发比例沿流程均呈现增大的趋势，其中，博尔塔拉河两月蒸发比例均值为41.1%，精河蒸发比例均值为45.4%，艾比湖蒸发比例均值为15.4%，整体而言，基于¹⁸O所计算的河水蒸发比例，精河蒸发比例最大、博尔塔拉河次之、湖水最小。4）利用HYSPLIT模型揭示了研究区采样期间7月水汽主要来自于西风带气流与北冰洋气流，8月水汽主要来自于中高纬度的西伯利亚气流，研究区降水主要以西风所携带的水汽输送为主。

关键词: 艾比湖, 氢氧稳定同位素, 河水蒸发, LC偏离程度（LC-excess）, HYSPLIT模型