An integrated study of "source to sink" process for runoff and sediment discharge of the Yalu River drainage and influence factors

Taking the drainage basin of the Yalu river as a whole, this paper makes an integrated study of water and sediment discharges for the upstream, midstream and downstream of the river respectively. Results show that the annual runoff of the midstream is about two times higher than that of the upstream, and the annual runoff of the downstream is in an order of magnitude higher than that of the upstream. In most of the years, the amount of sediment in the downstream is less than that in the upstream. With the effects of the human activities such as the construction of water conservation projects in the middle and lower reaches, the downstream runoff and sediment transport of the Yalu river are stepwisely reducing. The difference between annual runoff and inter-annual sediment yield increases gradually, and the decrease and annual difference of sediment transport volume is greater than that of runoff. Especially since the mid-1960s, human activities have become stronger and rendered significant impacts on sediment transport. According to the characteristics of ENSO event, the decrease in rainfall influenced by climate change is the main cause of the decrease in runoff, and to some extent, effecting the decrease in sediment transport.