Stable Isotopes in Precipitation in Irrigation Areas in the Proximity of Yellow River in Ordos and the Origin of Its Water Vapor

Abstract

【Objective】 Global warming has resulted in change in precipitation across many regions around the world. In this paper, we analyze the stable isotopes in precipitation in Ordos of Inner Mongolia, and then used them to track the origin of the water vapor in the irrigation areas proximal to the Yellow River in the region. 【Method】 Rainfalls were sampled from June to September in 2020, and stable hydrogen and oxygen isotopes in them were measured. Their correlation with factors including air temperature and daily precipitation was analyzed, from which we established the downline equations. The origin of the water vapor was tracked based on the variation of deuterium surplus value; reliability of the results was determined by the HYSPLIT air mass trajectory model 【Result】 ①The isotopes in the sampled precipitation during the experimental period was significantly lower than that in other months, showing their significant correlation with rainfall with p=0.01. ②The downline equation was δD=7.13δ18O-1.67, affected by evaporation greatly. ③Water vapor in June was affected by both the westerly belt and the polar air mass, accompanied by water vapor coming from the southeast coastal region. The water vapor in July and August was similar, coming from northwestern China. Water vapor in September was affected by the water vapor in the westerly belt, the polar air mass and local evapotranspiration. 【Conclusion】 Precipitation is the main factor determining its isotope content and origin. The HYSPLIT simulation and dynamic-change analysis of the deuterium surplus value showed that the water vapor in the westerly zone is the origin of the water vapor seen in the studied area.

Keywords

• ordo’s irrigated area along the yellow-river
• atmospheric precipitation
• stable isotopes
• water vapor source