Stability of Water Yield in Watersheds

The hydrological system of a watershed is intricately influenced by both underlying characteristics and climate conditions. Understanding the variability in water yield is essential for effective water resources management and water security in the context of changing environments. In this study, we adopted the Budyko framework and leveraged simulations from the CMIP6 model to investigate the compensation effects of climate and underlying characteristics on watershed water yield. Based on Taylor expansion and Budyko framework, we estimated the sensitivity of watershed water yield to climate and underlying characteristics (the first-and second-order partial derivatives). By combining external watershed characteristics (e.g., water yield ratios and underlying characteristics) with internal sensitivity coefficients, this study further used vine copula and principal component analysis to quantify the stability of watershed water yield. Our findings show: (1) Water-yield changes related to underlying characteristics could be offset by climate-related water-yield changes across all climate zones, maintaining the water yield ratio steady (i.e., the compensation effects). (2) However, global watersheds will turn more sensitive to underlying characteristics and less sensitive to climate variation in the future. Both climate- and underlying-related sensitivities increase in watersheds with arid climates. (3) The stability of watershed water yield will gradually diminish in the future. From 1901~~1950 to 2051~~2100, the global stability of 280 watersheds drops from 0.054 to 0.021 (i.e., stability index identified by the joint probability). Particularly, the largest change in stability of water yield reaches −0.347±0.18 in arid regions. In semi-arid, semi-humid, and humid regions, the changes are −0.039±0.010, −0.028±0.005, and −0.005±0.002, respectively. The findings provide a reference for the future sustainable water resources development under climate change, highlighting the vulnerability of the water resources in arid and semi-arid watersheds.