Temporal variation of the relationship between water discharge and sediment concentration in the Pearl River Delta

Haochuan Feng, Wei Zhang

Friday 3 july 2015

12:30 - 12:33h at South America (level 0)

Themes: (T) Sediment management and morphodynamics, (ST) Basin-wide sediment management, Poster pitches

Parallel session: Poster pitches: 15J. Sediment - Basin & Environment - Wetland

The relationship between water discharge and sediment concentration in rivers are significant for understanding morphodynamics and environmental characteristics of the river deltas. As the sediment is stored at low flow and transported under high discharge conditions, the flux of suspended sediment in rivers is often a function of water discharge. In the case of the Pearl River Basin, complexity of the relationship is affected by the fragile geological environment and the intensive human activities. In this study, relationship between water discharge and sediment concentration are illustrated based on the recent 50 years of monthly date set in the three major rivers of the Pearl River Delta. On the basis of analysis, the decadal and annual variations of suspended sediment load are been described. Specifically, the annual suspended sediment load from the Pearl River running into the sea exerts a significant decreasing trend in the past two decades, with the average sediment flux being 38.60% less in the 2000s than that in the 1950s. On the contrary, the sediment flux had an obvious increasing trend before the 1990s, the average annual sediment flux increased by 30.43%. Meanwhile, water discharge reached its peak in this decade at the same level as sediment transport, The method of regression analysis was used to explore the influence of precipitation in the variation on the sediment flux. It was found that the climate change is not the main driving force which regulate the variation in suspended sediment load. Furthermore, the sediment rating curve in 1957 to1970 is applied to estimate potential sediment load (1971 to 2012) in the absence of human influences. The result show that the intensive land use caused an increase in suspended sediment load before the 1980s, while the massive construction of large dams after 1990s result in a decrease in the suspended sediment load delivered to the ocean.