Tracking seasonal evaporation of arid Ebinur Lake, NW China: isotopic evidence

Evaporation is a major water flux in the global terrestrial water balance, a key process in the course of water cycle. In this study, river-lake water samples in the Ebinur Lake Basin of the arid climate zone of NW-China were taken on May, August, and October 2021, to analyze the seasonal evaporation process and mechanism using δ²H and δ¹⁸O as proxies. The results showed that the mean δ²H and δ¹⁸O values of river water were − 83.1‰ and − 11.84‰ in May, -76.0‰ and − 10.85‰ in August, and − 89.4‰ and − 12.78‰ in October; and that of the lake water were − 24.7‰ and − 1.54‰ in May, -18.5‰ and − 0.08‰ in August, -27.8‰ and − 2.21‰ in October. This showed enrichment of δ²H and δ¹⁸O in summer, depletion in winter, and intermediate during spring and autumn. The water evaporation ratios of May, August, and October were 53.0%, 56.6%, 51.2% for Ebinur Lake; 13.5%, 20.3%, 6.7% for the Kuitun River; 8.8%, 14.5%, 6.2% for the Bortala River; 6.2%, 10.0%, 3.3% for the Jinghe River. And the water evaporation ratios were, in descending order, the Ebinur Lake, Kuitun River, Bortala River, and Jinghe River. Spatial analysis showed that the water evaporation ratio from the Bortala River increased from 4.4% upstream to 12.7% downstream and that of the Jinghe River increased from 6.0% upstream to 9.2% downstream. The evaporation ratio of the basin showed a strong positive correlation with temperature (R = 0.94), a weak positive correlation with precipitation (R = 0.56), a strong negative correlation with humidity (R=-0.94), a strong negative correlation with altitude (R=-0.61), and a strong sensitivity to the composition of δ²H and δ¹⁸O in the water body. The study using δ²H and δ¹⁸O as proxies can effectively reveal a seasonal model of water evaporation in the arid Ebinur Lake Basin, shedding lights on analogues in the world.