Attribution analysis of the natural runoff evolution in the Yellow River basin

Natural runoff in the Yellow River basin has suffered a sustained decline under the influence of climate change and human activities. Earlier studies mainly investigated the attribution of climate change and human activities, while focusing on the observed runoff decline and rarely on natural runoff, which is not conducive to the efficient utilization and scientific management of water resources in the Yellow River basin. In this study, natural runoff during different periods in the Yellow River basin were evaluated by means of a dualistic water-cycle model, while the contribution of the main factors on the declining natural runoff was elucidated by a multi-factor attribution method. Results revealed that the 1956-2016 annual natural runoff at the Huayuankou station was reduced by 11.46 billion m³ compared to 1956-1979. The contributions of climate change, land-use change, and social water use were estimated to be 24.4%, 25.0%, and 50.6%, respectively. Analysis of the contributions in each Yellow River zone indicated that climate change and human activities were the dominant factors upstream and downstream of Lanzhou, respectively. In order to mitigate the declining trend of natural runoff and promote the ecological protection and high-quality development in the Yellow River basin, stronger measures, such as deep water saving, rigid water control, moderate water increase, efficient water management, and water protection legislation, should be implemented.