The hydro-environmental response on the lower Yellow River to the water-sediment regulation scheme

Heavy sedimentation has led to the phenomenon of a secondary perched river in the lower Yellow River. The water-sediment regulation scheme (WSRS) using the Xiaolangdi Reservoir was implemented in 2002 to solve this problem. In this study, we analyzed the impact of the WSRS on the lower Yellow River and investigated the mechanism by which the WSRS affects channel erosion. We found that the runoff and sediment load, the sediment grain size, and the river channel of the lower Yellow River have all altered dramatically since the implementation of the WSRS. The variations in runoff and sediment load are no longer synchronized: runoff shows a rising trend, whereas sediment load remains relatively stable. The proportions of runoff and sediment load during the rainy season have decreased, whereas the proportions of runoff and sediment load during the dry season have increased. The median sediment grain size displays a gradually increasing trend top-down along the lower Yellow River. The main river channels in the lower Yellow River have been fully scoured, leading to an increase in channel depth and bankfull discharge. In addition, the sediment load flowing into the estuary reach is relatively stable, with an average value of 158.6 x 10(6) t, which is sufficient to maintain the dynamic balance of the Yellow River Delta. We found that the degree of channel erosion in the lower Yellow River depends mainly on the incoming sediment concentration. (C) 2015 Elsevier B.V. All rights reserved.