GLOBAL CHANGE AND THE SEDIMENT LOADS OF THE WORLD’S RIVERS
River sediment loads exert an important influence on both the natural functioning of river systems and on their exploitation.Since they are sensitive to climate and land cover change and to a wide range of human impacts，they represent an important measure of the functioning of the Earth system and of the effects of global change.Long-term reconstructions of land-ocean sediment transfers covering both geological timescales and the more recent past extending back over several millennia，emphasise the sensitivity of sediment loads to global change.However，in this contribution emphasis is placed on more recent changes covering the past ca.50 years，as evidenced by records provided by monitoring programmes.Although records of sediment load are unavailable for many world rivers and existing records are of relatively short duration，the available data indicate that the sediment loads of many of the world’s rivers have been characterised by significant changes in recent years.Examples are presented to show that the sediment loads of some rivers have declined markedly in recent years，whereas others have shown significant increases.The key drivers of these changes include dam construction and the associated trapping of sediment by reservoirs causing decreased loads，land clearance and other forms of catchment disturbance causing increased loads，and sand mining，and soil conservation and sediment control programmes again causing decreased loads.The impact of climate change is，however,less evident,when viewed in terms of the recent past.Any attempt to provide a global assessment of the impact of recent global change on the sediment loads of the world’s rivers and of the relative importance of increasing and decreasing trends in influencing the land-ocean sediment flux must take account of the natural buffering of changing river loads evidenced by some river systems，and the different timing of human impact and associated changes in sediment load in different areas of the globe.Where sediment loads are changing，the available evidence suggests that declining sediment loads，caused by sediment trapping by reservoirs，are likely to represent the dominant trend for rivers in developed areas of the globe and in many areas of the developing world.
Global change sediment loads human impact
D.E.Walling
Department of Geography,University of Exeter,Amory Buulding,Rennes Drive,Exeter,EX4 4RJ,UK
国际会议
High-level International Forum on Water Resources and Hydropower(第一届国际水利水电高层论坛)
北京
英文
10-23
2008-10-17（万方平台首次上网日期，不代表论文的发表时间）