Controls of Climate and Catchment Behaviour on Runoff Response Across Large‐Scale Sample

ABSTRACT Recent research has extensively examined the response of runoff to climate change. However, the physical mechanisms underlying runoff responses in changing climate conditions remain poorly understood. To address this gap, this study uses measured streamflow and meteorological data from the public GAGES‐II database to investigate the physical controls influencing runoff responses to climate and catchment behaviour across more than 1000 catchments in the contiguous United States. Eighteen flow signatures and 56 indicators related to catchment attributes were analysed and grouped using a hierarchical clustering method, resulting in the classification of the 1000+ catchments into ten clusters, each with distinct characteristics. Within each cluster, we explored the patterns of runoff response, focusing on runoff changes and sensitivity for each flow signature and catchment attribute. Our findings indicate that flow signatures such as runoff ratio, annual runoff, and the 95th percentile runoff significantly affect total runoff changes. Evapotranspiration displays a trade‐off relationship with overall runoff changes but shows a synergistic relationship with Richard Baker's rapid runoff. Furthermore, the runoff changes driven by catchment attributes align with the total changes, suggesting that catchment behaviour predominantly influences runoff generation processes. Climate factors tend to exert greater influence in arid and semi‐arid catchments.