A discussion on natural sediment yield in the upper and middle Yangtze River

Abstract

In this study,soil erosion is divided into natural soil erosion and anthropogenic soil erosion.The natural soil erosion is ubiquitous on the earth since the earth came into being.Erosive and accumulative topographic features,such as peneplain,river terrace,sedimentary basin,etc.,have disclosed the existence of natural soil erosion in the upper and middle Yangtze River since the early Quaternary.Using the thickness,dating and area of sediment deposited in the Dongting Lake,Poyang Lake and the ancient Yunmeng Lake,the specific sediment yield of the watersheds draining into these lakes is found to be 264.2t/km~(2)·a,312.5t/km~(2)·a and 297.0t/km~(2)·a,respectively.Moreover,the natural sediment yield from some experimental plots located in west Sichuan and the Three Gorge areas is estimated to be about 342.0t/km~(2)·a and 75~270t/km~(2)·a,respectively.Thus,the natural sediment yield ranges from 264.0t/km~(2)·a to 342.0t/km~(2)·a in the upper and middle Yangtze River,which is about 50%-60% of the modern sediment yield in the area.The results of this study will help us to understand the characteristics and tendency of the modern soil erosion in the upper and middle Yangtze River,and will be a sound background for realizing the goal of conserving eco-systems and building an environmental management in the area.