Abstract: As a key link in the water cycle process, land evaporative water vapor profoundly affects the water resources and ecological environment of inland river basins. The study of water vapor recirculation ratio is of great significance to the deployment and management of regional water resources. In the objective of providing basic data and theoretical references for the water cycle study in the basin, we looked into the contribution of recirculated water vapor to precipitation by using the water vapor recirculation model based on the stable isotope method. We selected the monthly precipitation isotope data of 13 sampling points in the Shaliu river basin of Qinghai Lake from May to September 2019 for the model. From May to September 2019, the monthly average water vapor recirculation ratio in the Shaliu river basin of Qinghai Lake was 11.01%, 12.64%, 8.13%, 9.48% and 14.97%, respectively, averaging 11.25%. The recirculation ratio presents obvious seasonal changes: in May, the ratio begins to increase, and then reduces, and increase again, reaching the maximum in September. In spatial scale, the monthly water vapor recirculation ratio differs: from June to August, the recirculation ratio in the river source area is greater than that in the estuary area, displaying a clear increasing trend from the estuary area to the river source area. The northwest mountainous area of the basin sees the maximum recirculation ratio. The ratio from May to September is mainly affected by altitude and the eastward water vapor source at a height of 500 m. Water vapor recirculation is an important source of precipitation in the Shaliu river basin. Attentions to the water vapor recirculation will be conducive to the management and effective use of water resources in the basin.

Key words: water vapor recirculation, stable isotope, precipitation, water resources allocation, Qinghai Lake, Shaliu river basin