Abstract: Located in China's south-north transitional climatic zone, the Huaihe River Basin is prone to flood and drought disasters because of complex and changing precipitation processes and atmospheric moisture sources.Based on the stable hydrogen and oxygen isotopic data from Global Network of Isotopes in Precipitation (GNIP), we investigated into the driving factors of temporal and spatial variations and their climatic implications.By analyzing the isotopic compositions (δ¹⁸O,δ²H, and deuterium surplus) and Local Meteoric Water Line (LMWL) in response to local temperature and precipitation, we expounded the atmospheric moisture sources in different seasons and air-mass moving processes in the basin.Results demonstrated that the isotopic composition of precipitation can be used to indicate south-north transitional climatic features.The spatio-temporal changes of isotopes and abnormally low slope and intercept of LMWL were mainly caused by different moisture sources and isotopic fractionations in the air-mass moving process rather than local precipitation environment.Deuterium tracing and HYSPLIT simulation results further proved that the sources and variations of atmospheric moisture over the Huaihe River Basin were controlled by monsoon activities, and the alternations between winter and summer monsoons led to V-shaped characteristics of deuterium surplus.

Key words: precipitation, stable hydrogen and oxygen isotopes, atmospheric moisture source, climatic implications, Huaihe River Basin