Changes in sediment load in a typical watershed in the tableland and gully region of the Loess Plateau, China

Changes in sediment load of the Yellow River, and the contributing factors, have been widely studied and many valuable results have been reported. However, these studies were mainly conducted in the hill and gully region of the Loess Plateau, while studies on other regions, such as the tableland and gully region, which is more important for food production, and social and economic development, have rarely been reported. In this study, a typical watershed in this region was selected to analyze the changes in the sediment load between 1981 and 2016, and the contributions of its influencing factors. The Mann-Kendall (MK) test was applied to annual runoff and sediment load, and the year 1994 was identified as the year of mutation; thus, a baseline period (1981-1994) and a response period (1995-2016) were distinguished. By combined use of the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Delivery Distributed Model (SEDD), sediment yields for the two periods were estimated, and compared with the corresponding measured data. The contributions of influencing factors, including natural factors (changes in rainfall and rainfall erosivisty) and anthropogenic activities (human induced vegetation change, slope terraced farmlands, and check dams in the stream networks), were analyzed. The results demonstrate that; 1) Sediment load in Yanwachuan watershed decreased substantially between the two periods; 2) Sediment load change was mainly influenced by human induced vegetation cover changes across the watershed, and check dams in the stream networks, which accounted for approximately 80% and 20% of the sediment load reduction, respectively; 3) The sediment trapped by the check dams are likely to increase in the future, thus effective measures should be implemented to protect check dams, and to ensure the effects of check dams on sediment reduction can be maximized. The results of this study help to understand the changes in sediment load in the tableland and gully region, and can provide valuable guidance on best practices in terms of local soil conservation management.