Equilibrium relations for water and sediment transport in the Yellow River

Abstract

The equilibrium relations for water and sediment transport refer to the relative balance of sediment transport and the relative stability of river courses formed by the automatic adjustment of riverbeds. This is the theoretical basis for the comprehensive management of sediment in the Yellow River. Based on the theories of sediment carrying capacity and the delayed response of riverbed evolution, in this study, the equilibrium relations for water and sediment transport in the Yellow River are established. These relations include the equilibrium relationships between water and sediment transport and bankfull discharge in the upper and lower Yellow River and between water and sediment transport and the Tongguan elevation in the middle Yellow River. The results reveal that for the Ningmeng reach, the Tongguan reach, and the lower Yellow River, erosion and deposition in the riverbeds are adjusted automatically, and water and sediment transport can form highly constrained equilibrium relationships. These newly established equilibrium relationships can be applied to calculate the optimal spatial allocation scheme for sediment in the Yellow River.

Introduction

The equilibrium relations for water and sediment transport refer to the relative balance of sediment transport and the relative stability of river courses formed by the automatic adjustment of riverbeds (Chen, 2017). Strictly speaking, owing to the unsteady water and sediment conditions, the river flow is usually non-equilibrium sediment transport, which occurs through automatic riverbed adjustment to erosion and deposition (Fang et al., 2008, 2012; Fang & Rodi, 2003; Fang & Wang, 2000; He et al., 2019). The water and sediment transport in river channels tend to develop a relative balance in sediment transport and form a relatively stable channel shape. Therefore, the study of the equilibrium relationship between water and sediment transport is the theoretical basis for river management, which is of great significance for the comprehensive management of sediment in the Yellow River. In the past, many scholars have performed a considerable amount of research on the relationship between water and sediment in the Yellow River. For example, Zhao et al. (2012) studied the relationship between water and sediment transport in the main stream of the Yellow River. In addition, Xu et al. (2016) studied the response of bankfull discharge in the Inner Mongolia reach of the upper Yellow River to human activities and climate change. Dong et al. (2014) studied changes in the process of bankfull discharge in the Ningmeng reach of the upper Yellow River, and Wu et al. (2004) studied the influence of incoming water and sediment on the Tongguan elevation. Furthermore, Lin et al. (2018) studied the influence of deposition in different parts of the upper and lower Tongguan reaches on the Tongguan elevation. Wu et al. (2007) studied the response of bankfull discharge to the change in incoming water and sediment in the lower Yellow River. On the basis of that study, Chen et al. (2018) further studied the relationship between bankfull discharge and the processes involving water and sediment in the lower Yellow River. There are other related research results (Draut et al., 2011; Grams et al., 2007; Guo et al., 2020; Hu et al., 2012; Kondolf et al., 2014; Zhang et al., 2013). These studies play an important role in understanding the changes of water and sediment and river course of the Yellow River, but these studies only reveal the relationship between water and sediment transport and river bed evolution of the Yellow River in a certain aspect or part of the reach, and their theoretical basis is still insufficient. Therefore, more comprehensive studies using both theory and empirical methods are needed. Based on the theories of sediment carrying capacity and the delayed response of riverbed evolution, new equilibrium relations for water and sediment transport in the Yellow River are systematically developed in this study. This work includes the equilibrium relationships between water and sediment transport and bankfull discharge in the upper and lower Yellow River and between water and sediment transport and the Tongguan elevation in the middle Yellow River. This comprehensive framework provides the theoretical and technical support necessary for the effective treatment of the Yellow River.