Runoff sensitivity variation should be incorporated in hydrological analysis

With great changes, such as climate and land use/cover, occurring in hydrological processes over the last decades, runoff sensitivity, here defined as proportional changes in runoff caused by a given proportional change in its driving factors, has also been changing over time. However, few studies have focused on this sensitivity change, and runoff sensitivity is always considered to be constant in runoff attribution analysis with an elasticity-based method. In this study, we attempt to examine the temporal variation of runoff sensitivity in the middle reaches of the Yellow River basin, China, and quantify its effects on the changes in runoff so that the existing attribution method can be improved. We found that runoff sensitivity showed statistically significant trend, and runoff became more sensitive to changes in climate and catchment characteristics (CC). CC, largely affected by land use/cover change resulting from large scale ecological projects, was the major contributor to change in runoff sensitivity, followed by precipitation, and lastly potential evapotranspiration. Runoff sensitivity variation contributed approximately 20% to the proportional runoff change, and by allowing runoff sensitivity to change over time, relative contributions of climate and CC to runoff would range from − 5.05% to 9.94%. Our study supplements research focusing on hydrological changes and interactions, and we suggest that temporal variation in runoff sensitivity should be considered when quantifying the impacts of driving factors on changes in hydrological processes.