Characteristics of runoff and sediment load during flood events in the Upper Yangtze River, China

Abstract

Understanding the change in sediment load at a flood-event scale helps to enhance channel regulation and optimize reservoir operation. This is particularly true in the Upper Yangtze River basin where a few flood events contribute most of the annual sediment load. This paper collected field data from representative hydrological stations and applied statistical analysis to investigate the change in runoff and sediment load during flood events in the Upper Yangtze River, including both the mainstream (Jinsha River) and its major tributaries (Min, Tuo, Jialing, and Wu Rivers). The results show that flood events contribute more sediment load than runoff volume to the annual statistics. A general decreasing trend occurs in sediment load in all river basins, which is closely related to soil conservation efforts and dam construction. The series of sediment load modulus of each stations present abrupt change. The variations in sediment load modulus in low flow are more significantly than those in high flow at different abrupt-change period, indicating high flows during flood event have been found to still carry the same amount of sediment as their predecessors in the Upper Yangtze River. An “abnormal” increase in sediment load in recent years (2013–2020) has been observed at the Fushun station in Tuo River, and three factors, i.e., earthquake, high-intensity rainstorm and local scouring, were identified to be responsible for such increase. The findings of our study are helpful for better management of basin-scale sediment resources and regulation of reservoirs in the Upper Yangtze River.