How do natural climate variability, anthropogenic climate and basin underlying surface change affect streamflows? A three-source attribution framework and application

Abstract

The streamflows in many rivers have been detected to be declining recently due to environmental changes, which are dominating water management strategies and affecting water security. The decline was usually ended up with attribution to climate change and underlying surface changes, without further exploring the effects of natural and anthropogenic components in climate. It might lead to overestimation for human-induced climate change impacts and inappropriate adaptation. The identification of the anthropogenic elements in streamflow change is very crucial and increasingly required by water management planning, climate mitigation and adaptation actions. A novel framework is proposed for streamflow change attribution in terms of three sources of natural climate variability (NCV), anthropogenic climate change (ACC) and the underlying surface changes in basins. The results suggest that the role of the underlying surface changes in basins overwhelms that of climate change in the recent historical period. However, the natural climate variability could not be neglected since it may play the dominant role in streamflow change, compared with that of the anthropogenic climate change. The results also highlight that we need to clarify the effects of human-induced climate change and the underlying surface changes, which are the goals of climate change adaptation and mitigation. The uncertainties of the attribution are analyzed in contrast with other attribution work in the same study case, and the sources are presented explicitly. The conclusion could facilitate a better understanding of the hydrological processes as a result of environmental changes and provide an efficient reference for administrators and decision makers.