Fig. 4: Water isotope plot comparing drip water and local rainfall.

Rainfall data are from ref. ²⁶, and drip water are from the five sampling campaigns described in the text. The regression, or local meteoric water line (LMWL), was calculated using the precipitation-weighted method (WLS-LMWL) in ref. ²⁶. Confidence interval is 95%. Large crosses are the distribution modes for preferential flow (blue; δ¹⁸O = −4.67 ± 0.06‰, δD = −19.32 ± 1.21‰) and diffuse flow (orange; δ¹⁸O = −4.12 ± 0.12‰, δD = −15.09 ± 0.79‰). Inset compares slope values and error bars represent ± 2 standard error. The similarity of the slope values of the drip waters and local rainfall suggests that evaporation under low humidity (soil zone) has not substantially modified the drip waters.