Source of soil water in cold regions based on stable isotope tracers

Soil water plays a key role in vegetation growth and ecological stability in cold regions. The soil water sources in the Qilian Mountains of the northeastern Tibetan Plateau have been quantified based on stable isotope data (δ2H and δ18O) of 1913 samples. The results indicated that δ18O of soil water ranged from ˗14.13–11.21‰, with an average of ˗6.78‰, and on a spatial scale, it increased gradually from the southeast to the northwest, where it became more positive. The stable isotopes of soil water are affected by evaporation, leading to a lower slope and interception of the evaporation line: δ2H = 3.23 δ18O–32.51 (R2 = 0.71, p