Seasonal characteristics of stable hydrogen and oxygen isotopes in precipitation and water vapor sources in Hubei section of the Three Gorges Reservoir Region

To investigate the spatiotemporal evolution patterns of precipitation in the Hubei section of the Three Gorges Reservoir Region under climate change, 187 precipitation samples collected from October 2022 to September 2023 were utilized to analyze the stable hydrogen and oxygen isotope characteristics of precipitation. The influence of meteorological factors such as temperature, precipitation amount, and relative humidity was examined. Additionally, the HYSPLIT model was used to trace water vapor transport trajectories and identify water vapor sources. The results indicate that there are obvious seasonal variations of stable hydrogen and oxygen isotopes in precipitation in the Hubei section of the Three Gorges Reservoir Region, with relative depletion in summer and autumn and relative enrichment in winter and spring. The relationship between δD and δ¹⁸O in the study area is δD=8.21 δ¹⁸O+11.23 (R²=0.94, p＜0.01). It reflects the regional wet and rainy climatic characteristics. Precipitation amount and relative humidity are the main factors affecting the stable hydrogen and oxygen isotopes in precipitation. Temperature is the dominant factor influencing d-excess. Seasonal variations are observed in the sources of precipitation for the study area. In summer, precipitation mainly comes from the water vapor of the Pacific Ocean, South China Sea, and Indian Ocean carried by the southeast monsoon and the southwest monsoon. In winter, precipitation primarily derives from the west and northwest directions of the Eurasian continent. Spring and autumn serve as transitional periods, witnessing shifts in the predominant source of precipitation between the ocean and land.