Variations of runoff and sediment and their response to human activities in the source region of the Yellow River, China

The Yellow River is the mother river of the Chinese nation. The source region of the Yellow River is an important region for water conservation in China. The hydro-ecological environment of the Yellow River source region is very fragile. Therefore, the variation processes of runoff and sediment discharge in the Yellow River source region have become the subject of considerable concern in recent years. However, the source region of the Yellow River has been studied relatively little, and the influence of these two process in the source region of the Yellow River remains unclear. In this paper, precipitation, runoff, sediment discharge, and their interactions in the source region of the Yellow River from 1956 to 2018 were analyzed using several different time-series evaluation methods, such as Spearman’s rank correlation coefficient method, the ordered clustering analysis method, and the double-mass curve method. Furthermore, the impact of Huangheyuan hydropower station on these hydrological elements was analyzed in relation to the few other human activities in Sanjiangyuan National Nature Reserve. The results indicated that the precipitation in the source region of the Yellow River increased significantly, the sediment discharge decreased non-significantly, and there was no significant change in runoff over this time period. The years 1995 and 2011 were probable mutation points of the sediment discharge series, and the mutation point of the precipitation series was likely 2001. The Huangheyuan hydropower station is the main reason for the decrease in annual sediment discharge in the source region of the Yellow River.