Understanding the hierarchical controls of geographical features on hydrological responses in humid mountainous areas through a stepwise clustering scheme.

In mountainous basins with low anthropogenic influences, runoff generation varies geographically, and it is essential to investigate the hierarchical controls of geographical features on hydrological responses. In this study, a stepwise clustering scheme was proposed to classify 64 mountainous basins located in eastern China into 11 basin groups and 3 hierarchies according to the geographical features of rainfall, topography and geomorphology, and soil and geology. Then, the leave-one cross validation assessing the transferability of hydrological model parameters was used to measure the hydrological similarity among basins and within each group, and to examine the quality of classification. The results showed that 92% of all basins had other basins with high similarity. The overall similarity of the hydrological responses in the 11 basin groups was quite different. The basin groups driven by heavy rainfall events tended to form highly similar runoff processes. Basins in the groups with steeper terrain, more convergent slopes, rounder shapes, and better vegetation cover also exhibited a higher overall hydrological similarity. Then, according to the discharge characteristics, the controlling role and intensity of different hierarchical geographical features on hydrological responses were quantitatively represented. In 6 of the 11 basin groups, rainfall features (e.g. average monthly rainfall and rainstorm characteristics) were collectively the primary controlling factor of runoff, while topographic and geomorphic features were the second most important factor. Rainfall features were the second most important controlling factor in the other four basin groups. However, the controlling role of soil and geological features on hydrological responses appeared to be unstable. In summary, these findings could provide guidance for hydrological predictions in ungauged basins in diverse geographical environments. [ABSTRACT FROM AUTHOR]