Fog interception maintains a major waterfall landscape in southwest China revealed by isotopic signatures

Fog water intercepted by the forest canopy can be an important extra water input for the near-surface ecosystems in some tropical montane or coastal Mediterranean zones. However, the significance of fog interception on groundwater systems needs to be further studied. An inland subtropical cloud forest in the southwest of China is covered by frequent fog/mist and has thousands of waterfalls with significant flow. To verify the role of fog interception to the local hydrological budget, field investigations and sampling campaigns were carried out over different temporal and spatial scales. Compared with local rainwater, surface water and spring water in the forest were more enriched in H and O isotopes and had much higher d-excess, indicating that fog water produced by inland evapotranspiration is a key water supplier. During the dry period, waterfalls are sustained by baseflow, of which a considerable fraction comes from fog interception recharge. The waterfall landscape maintained by fog drip water in this study area represents an example of the important contribution of fog water to some subtropical montane groundwater systems