| 摘要: |
| 研究三峡库区流域内降水来源，对于揭示三峡库区生态系统水分循环过程对流域极端干旱的响应机制具有重要意义。根据三峡库区2022年8月的实测大气水汽和8～10月的降水稳定氢氧同位素组成以及相关气象资料，明确了三峡库区的水汽输送特征，运用三组分同位素混合模型估算了再循环水分（即表面蒸发和蒸腾水汽）和平流水汽对三峡库区上、中、下各段区域降水的贡献比例。结果显示：2022年8～10月，水汽通道方向由西南至东北，平流水汽团沿着库区山脉从上游至下游输送。9-10月期间，三峡库区中段的植被蒸腾(Ptr)、地表蒸发(Pev)和来自库区上段的平流水汽(Padv)对中段降水的平均贡献分别为35.4%±4.8%、0.2%±4.9%和64.4%±9.6%；三峡库区下段的Ptr、Pev和来自库区中段的Padv对下段降水的平均贡献分别为27.9%±4.8%、0.8%±3.9%和71.3%±8.6%。在高温干旱最为突出的8月份，三峡库区中段的Ptr、Pev和来自库区上段的Padv对中段降水的平均贡献分别为60.9%±3.3%、2.2%±3.7%和36.9%±6.6%；三峡库区下段的Ptr、Pev和来自库区中段的Padv对下段降水的平均贡献分别为16.5%±1.8%、2.6%±2.0%和80.9%±3.8%。西南风输送的平流水汽是库区降水的主要来源，库区各段再循环水分主要由植被蒸腾组成，地表蒸发贡献微弱。2022年8月降雨比历年同时期减少，导致降水水汽团同位素在库区下段产生轻微富集。此外，极端的高温干旱加速了库区中上段的水分循环，增强了再循环水分在库区中段降水中的主导作用，削弱了库区下段植被蒸腾对局地降水的贡献。 |
| 关键词: 三峡库区 氢氧同位素 同位素三元混合模型 水分循环 降水来源 |
| DOI： |
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| 基金项目:国家自然科学基金重点项目（U2240218）,中央高校基本科研业务费（B240205020）,国家自然科学基金项目（42307117）,中央高校基本科研业务费（B230201039） |
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| Using the three-component isotopic mixing model to decipher moisture sources of precipitation in the Three Gorges Reservoir basin during the droughty 2022 |
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Pan Xiaolong, Wang Weiguang, Xing Wanqiu, Wei Jia, Ye Zongchao, Cao Mingzhu, Li Hongbin, Sun Bokai, Zhu Shifeng, Yu Jiahe, Hou Yichen
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College of Hydrology and Water Resources, Hohai University
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| Abstract: |
| Studying the source of precipitation in the Three Gorges Reservoir (TGR) region is of great significance in understanding the ecosystem"s water cycling response to extreme drought. This study analyzes the stable hydrogen and oxygen isotope composition of atmospheric water vapor measured in August 2022 and precipitation from August to October in the TGR region, along with relevant meteorological data, to elucidate moisture transport characteristics. A three-component isotope mixing model was applied to estimate the contributions of recycled moisture (i.e., surface evaporation and transpiration vapor) and advective vapor to precipitation in the upper, middle, and lower sections of the TGR region. The results indicate that from August to October 2022, moisture pathways were oriented from southwest to northeast, with advective moisture transported from upstream to downstream along the reservoir mountain range. During September-October 2022, the average contributions of vegetation transpiration (Ptr), surface evaporation (Pev) and advected vapor (Padv), to precipitation in the middle section of the TGR region were 35.4%±4.8%, 0.2%±4.9%, and 64.4%±9.6%, respectively. In the lower section, contributions were 27.9%±4.8%, 0.8%±3.9%, and 71.3%±8.6%, respectively. In August, when the high temperature and drought were most severe, the contributions in the middle section were 60.9%±3.3% for Ptr, 2.2%±3.7% for Pev, and 36.9%±6.6% for Padv, while in the lower section, they were 16.5%±1.8%, 2.6%±2.0%, and 80.9%±3.8%, respectively. The advective water vapor transported by southwesterly winds was the primary source of precipitation in the reservoir region, with recycled moisture mainly comprising vegetation transpiration and minimal surface evaporation. Rainfall in August 2022 was lower than in previous years, resulting in a slight enrichment of precipitation vapor isotopes in the lower section. In addition, the extreme heat and drought in August 2022 accelerated moisture cycling in the upper and middle sections of the TGR region, enhancing the dominant role of recycled moisture in the middle section while reducing the contribution of vegetation transpiration to local precipitation in the lower section. |
| Key words: Three Gorges Reservoir region hydrogen and oxygen isotopes three-component isotopic mixing model moisture recycle precipitation sources |
