Abstract: The lower Jinsha River Basin is situated in a region impacted by dry and hot valley climate. Atmospheric precipitation plays a pivotal role in the hydrological dynamics of the basin. We scrutinized the seasonal fluctuation patterns of stable isotopic composition in precipitation within the basin, and identified its influencing factors. Furthermore, employing isotope tracing techniques alongside the HYSPLIT (Hybrid-Single Particle Lagrangian Integrated Trajectory) model, we elucidated the sources of atmospheric precipitation in the area. Findings reveal distinctive seasonal trends in isotopic values, with negative values of δ²H and δ¹⁸O observed during rainy season and positive values in dry season. Temperature and rainfall emerge as primary influencers on the isotopic composition of local precipitation, while elevation exerts minimal impact. Notably, the local meteoric water line exhibits lower slope and intercept values compared to global and Chinese atmospheric precipitation lines, primarily due to non-equilibrium evaporation effects. Moisture sourcing analysis indicates a similarity between the precipitation origins in lower Jinsha River Basin and those in Kunming. Rainfall during the rainy season predominantly stems from the southwest and south Asian monsoons, while dry season precipitation potentially results from the westerly belt or polar continental air masses. These research outcomes are of substantial significance for understanding regional hydrological cycle within the lower Jinsha River Basin.

Key words: atmospheric precipitation, composition of hydrogen and oxygen stable isotopes, influence factors, atmospheric moisture source, the Lower Jinsha River Basin