The Impact Of Climate Change And Human Activities On Water Discharge And Sediment Load Entering Poyang Lake Basin

The sediment flux of drainage basin is mainly dominated by climate changes and human activities.Especially in the past 50 years,with the human activities intensifying,vegetation change and the reservoir construction has become the key factors of affecting sediment flux.The model of HydroTrend is applied to simulate the variations of water discharge and sediment fluxes into Poyang Lake based on the data from the five substreams of Poyang Lake Basin,namely Gan,Fu,Xin,Rao and Xiu rivers.Thus,the water and sediment discharge of the five rivers of Poyang Lake catchment during the period of 1000-2000(AD)are simulated suing HydroTrend model,and then the impact of climate change and human activities on water discharge and sediment load are identified.The simulating results indicated,the average water discharge of the five rivers flowing into Poyang Lake reached 103.65 km3/y,and climate change(especially precipitation)is the leading factor determining water discharge variations.Influenced by "Little Ice Age"(1451-1850 AD),the total water discharge of the catchment was reduced by no more than 10%.However,the sediment load reached to 10.30 Mt/y during the past 1000 years,and was mainly controlled by human activities.Suffered from the weaker intensity of anthropogenic impact,sediment load discharging into Poyang Lake of the five rivers was 9.21 Mt/y(1000-1700 AD).However,with increasing intensity of human activities during the past 300 years,the sediment load entering Poyang Lake underwent complicated variations.From 1701-1950(AD),resulted from intensified water and soil loss the total sediment load entering Poyang Lake,with mean value of 12.77 Mt/y,increased by 38.65%,comparing with that during 1000-1700(AD).During the period of 1951-2000(AD),the sediment load variation mainly reflected by the interactive impact of dam and water and soil erosion.From 1951-2000(AD),due to the influence of water and soil erosion greater than that of dam,the total sediment load entering the lake slightly increased to 13.42 Mt/y;however,as a consequence of sediment intercepted by dams continuous increasing,the total sediment load entering Poyang Lake during 1990-2000(AD)reduced to 8.97 M/y,which only accounted for 61.56%of the most high level of 1951-1980(AD),and approximately equaled to that of the low level(1000-1700 AD).In summary,due to influence of human activities,the total increased sediment load entering Poyang Lake amounted to 1128.43Mt.On the whole,water discharge of drainage basins are mainly controlled by climate variation under natural conditions.however,the human activities is the dominant factor in dominating the sediment load during the last century.