The effect of the seasonality of moisture sources on moisture flux and precipitation stable isotopes in the Shiyang River Basin

As one of the inland rivers in arid areas of Northwest China, precipitation is an important supply for the Shiyang River. Daily-scale stable isotopes of precipitation can provide record evidence for the moisture sources, so we collected daily δ 2 H and δ 18 O data of precipitation obtained from 11 sampling points and reanalysis meteorological data in the Shiyang River Basin from 2016 to 2020, to explore the moisture sources and the impact on moisture fluxes and precipitation isotope. The results showed the δ 2 H and δ 18 O values increase from upstream area to midstream and downstream areas, but the spatial variation of d-excess values is reversed. Dominated by westerly moisture, the moisture flux is higher when the westerly wind strengthens in winter. And the strength of the monsoon determines the water vapor content in summer. The δ 18 O is depleted in precipitation related to maritime sources than continental sources. Significant depletion of δ 18 O in precipitation is associated with the Atlantic Ocean (− 13.9‰) and Indian Ocean (− 13.5‰) sources, attributed to enhanced Rayleigh distillation caused by longer transport distances. The enrichment of δ 18 O in precipitation is associated with continental sources affected by evapotranspiration and secondary evaporation, such as inland China (− 8.0‰), Europe (− 8.6‰), and Mongolia-Siberia (− 9.0‰). This study indicates the moisture sources and transport processes in inland river basins of arid area, contributing to the understanding of the water cycle.