Spatial and Temporal Variation of Suspended Sediment Concentration Hysteresis in Upper Yangtze River

Reservoir sedimentation is a widespread concern in the world, and it has a major impact on the function of the reservoir. Three Gorges Reservoir is one of the largest reservoirs in the world, and its sedimentation has always been a research hotspot. The sediment transport in Three Gorges Reservoir is mainly in the flood season. However, after the construction of the upstream cascade reservoirs, there is still no clear understanding of the sediment transport during the flood season. Based on the daily series data , this paper analyzes the changes of water and sediment conditions in Three Gorges Reservoir in recent years. The flood process is selected by the change of water discharge, and the hysteresis pattern is used to classify the SSC-Q relationship in the flood process. According to the change of water and sediment load, the spatial and temporal variation of hysteresis pattern is analyzed. The results show that in the years around 2003 and 2013, the sediment load in Three Gorges area decreased significantly. In the flood season, the most important SSC-Q relationship is clockwise and anti-clockwise. The hysteresis pattern shows obvious spatial and temporal differences. Spatially , there are more anti-clockwise pattern in downstream. Temporally, anti-clockwise pattern is also increasing at mainstream in recent years.