Water-sediment synergistic relationship in the flood season in the coarse sand source regions of the loess plateau, China

Abstract

A number of studies have been conducted to determine the relationships between runoff and sediment under different conditions. However, the water-sediment synergistic relationship, which refers to the degree of intervention between the runoff and suspended sediment transport processes in the flood season, must be further analyzed. This study proposed the concept of the synergy degree between water and sediment based on the discipline of synergetics created by Haken (Haken, 1983). The flood and suspended sediment transport processes in the flood season and the measured water-sediment coordination levels were adopted in this study to obtain their synergy degree by taking as an example the largest and most continuous region from the Huangfu River to the Jialu River in the coarse sand source regions of the Loess Plateau. The results of this investigation are as follows. The degree of synergy between runoff and suspended sediment transport was below 0.722 from 1958 to 2016. Approximately 70% of the flood events in the five river basins had poor degrees of synergy between the flow and sediment processes in the flood season. Moreover, the synergy degrees of the water-sediment relationship were relatively low in the runoff and suspended sediment transport processes in the flood season due to the low order degrees of these two process subsystems. The low synergistic relationship between these two subsystems shows that the coordination and buffering abilities between the flood and suspended sediment transport processes were weak. These findings demonstrate the successful adoption of synergetics to ascertain the water-sediment synergistic relationship and also provided critical information for designing water conveyance systems with high sediment concentrations for irrigation in the coarse sand source regions of the Loess Plateau, China.