Global Assessment of Compound Risk of High Temperature and Low Streamflow

In river flowing areas, the co-occurrence of high temperature and low streamflow may cause compound hydrologic hot-dry events (CHHDEs). When thermal and hydrological extremes interact, the impact can be worse than when they occur individually. Evidence shows that CHHDEs have severe socio-economic effects, such as increasing pollutant concentration, endangering aquatic species, and reducing power generation. Despite the importance, large-scale risk quantification of CHHDEs remains rarely studied due to the lack of enough simulated data at the global scale.

Therefore, the objectives of this study are threefold: (1) developing the first global hydrologic hot-dry event dataset from 1901 to 2014 (containing four attributes: duration, intensity, severity, and magnitude) based on a state-of-the-art physically-based Tightly Coupled framework for Hydrology of Open water Interactions in River–lake network (TCHOIR) model, which dynamically simulates thermal and hydrological regimes; (2) developing a robust statistical framework to conduct attribution analysis to identify drivers of compound risk (distinguishing high temperature-driven, low streamflow-driven, and dependence-driven); (3) quantifying the impact of river order and hydrologic belt on compound risk to pinpoint CHHDEs hotspots.

CHHDEs have multi-sectoral impacts, including water availability, food security, and energy production. The compound risk analysis provides crucial insights to maintain regional resilience and guide adaptation strategies.