Decreasing trend of sediment transfer function of the Upper Yellow River, China, in response to human activity and climate change

An index (F ₛ) for sediment transfer function is introduced, based on the sediment budget at the channel scale. The purpose of this study is two-fold: to gain a deeper insight into how F ₛ is influenced by natural and human factors, and to provide some new knowledge for decision making in the management of the Upper Yellow River, China. Since 1960, the F ₛ of the Lanzhou to Toudaoguai reach of the Upper Yellow River shows a decreasing trend. At the drainage basin level, the decreased F ₛ can be explained by changes in precipitation and air temperature, as well as by a number of variables describing human activity, such as reservoir regulation, water diversion, and soil and water conservation. The higher temperature reduces the transfer function, while the larger runoff coefficient increases it. At the channel level, the decreased F ₛ can be explained by a number of variables of flow and sediment input. Three countermeasures for restoration of the F ₛ are suggested. Editor Z.W. Kundzewicz