Key drivers of changes in the sediment loads of Chinese rivers discharging to the oceans

摘要

The magnitude and variation of the sediment loads transported by rivers have important implications for the functioning of river systems and changes in the sediment loads of rivers are driven by numerous factors.In this paper,the key drivers of changes in the sediment loads of the major rivers of China are identified by reviewing recent studies of changes in their sediment loads.Except for the Songhua River,which presents no clear tendency of change in runoff or sediment load,nearly all the major rivers of China are characterized by an apparent decline in annual sediment load.The total annual sediment load of major Chinese rivers transported to the coast decreased from 2.03 billion t/yr during the period 1955 e1968 to 0.50 billion t/yr during the period 1997e2010.The primary drivers of changes in the sediment loads of the rivers are dam construction,implementation of soil and water conservation measures,catchment disturbance,agricultural practices,sand mining and climate change.Examples drawn from Chinese rivers are used to demonstrate the importance of these drivers.Construction of a large number of reservoirs in the Yangtze River basin represents the primary driver for the reduced sediment load of the Yangtze River.The implementation of soil and water conservation programmes is one of the key drivers for the sharp decline in the sediment load of the Yellow River.Catchment disturbance explains why the reduction of the sediment load of the Lancang-Mekong River at the Chiang Saen gauging station was much less than that at the Gajiu gauging station upstream.A reduction in sediment load resulting from the expansion of agricultural production may be the main driver for the reduced sediment load of the Huaihe River.The decrease in the sediment load of the Pearl River has been influenced by sand mining activities.Climate change is one of the key drivers responsible for the greatly reduced sediment load of the rivers in the Haihe River Basin.