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Data on sediment flux at three hydrologic stations from the 1950s to 2006 are utilized to study the decadal,annual,and monthly variations in suspended sediment load delivered from the Pearl River to the ocean.Results show that variations in sediment flux from three main tributaries,including the West River,the North River and the East River,are spatially non-uniform.Since nearly 90%of the suspended sediment load comes from the West River,its variation has dominated the overall tendency of sediment flux in the entire Pearl River.Although a significant decreasing trend exists in the annual variation of the total sediment flux,the decadal change can be divided into an increasing phase and a decreasing phase,with the turning point between the two phases in the late 1980s.From the 1950s to the 1980s,the average annual river sediment flux increased by 30.43%.However,sediment flux has decreased significantly since the 1990s,with the average sediment flux being 38.60%less in the 2000s than that in the 1950s.The current sediment flux is also 52.93%less than its peak in the 1980s. The monthly variation pattern of the suspended sediment load transport to the sea is more interesting. For the West River,all months show a decreasing trend,and for most months the reduction values are significant.However,for the East River the sediment load shows a decrease trend in the dry season and an increase trend in the wet season.The method of regression analysis was used to study the influence of precipitation in the variation on the sediment flux.It was found that the climate change is not the main driving force behind the variation in suspended sediment load.Before the 1990s, intensive land use destroyed the vulnerable ecosystem of the upper Pearl River,and speeded up the process of rocky desertification.Consequently,aggravated soil erosion caused an increase in suspended sediment load.However,sediment retention within reservoirs had begun to play a dominant role after the massive construction of large dams after 1990,and resulted in a decrease in the suspended sediment load delivered to the ocean.
Data on sediment flux at three hydrologic stations from the 1950s to 2006 are utilized to study the decadal, annual, and monthly variations in suspended sediment load delivered from the Pearl River to the ocean. Results show that variations in sediment flux from three main tributaries, including the West River, the North River and the East River, are spatially non-uniform. Nearly 90% of the suspended sediment load comes from the West River, whose variation has dominated the overall tendency of sediment flux in the entire Pearl River. Although a significant decreasing trend exists in the annual variation of the total sediment flux, the decadal change can be divided into an increasing phase, with decreasing point between the two phases in the late 1980s.From the 1950s to the 1980s , the average annual river sediment flux increased by 30.43% .However, sediment flux has decreased significantly the 1990s, with the average sediment flux being 38.60% less in the 2000s than tha t in the 1950s. The current sediment flux is also 52.93% less than its peak in the 1980s. The monthly variation pattern of the suspended sediment load transport to the sea is more interesting. For the West River, all months show a decreasing trend, and for most months the reduction values are significant. However for the East River the sediment load shows a decrease trend in the dry season and an increase trend in the wet season. the method of regression analysis was used to study the influence of precipitation in the variation on the sediment flux. It was found that the climate change is not the main driving force behind the variation in suspended sediment load. Before the 1990s, intensive land use destroyed the vulnerable ecosystem of the upper Pearl River, and speeded up the process of rocky desertification. Reconstructed aggravated soil erosion caused an increase in suspended sediment load. Host, sediment retention within reservoirs had begun to play a dominant role after the massive constructionsction of large dams after 1990, and resulted in a decrease in the suspended sediment load delivered to the ocean.