Impacts From Human Activities On Soil Erosion, Sediment Yield And Transport In Poyang Lake Basin

Climate change and human activities is the main reason affect basin sediment load, for which the construction of reservoir is one of the vital factors that impact on the hydrological and sediment effect. In this paper, soil erosion intensity in Poyang Lake Basin in 1990, 2000, 2010 were estimated which based on the USLE model. Combined with the hydrological and sediment change characteristics of Poyang lake Basin from 1955 to 2010, we evaluated the impact of reservoir construction on the hydrological and sediment effect. The main contents include as follow:(1) Intensity assessment of soil erosion based on USLESoil erosion modulus were estimated separately in 1990?2000?2010 in Poyang Lake Watershed based on USLE. The results show that: from 1990 to 2010 the soil erosion increase in the Poyang Lake Basin from 2000 to 2010; it specific displays that both the average Soil erosion modulus and total erosion areas increased from 1990 to 2010. And the total areas which above intensity erosion are also increase. In 1990, total area which above intensity erosion is about 273.99 km2, accounted for about0.25% of the total erosion area of the Poyang Lake Watershed, while in 2000, it is about 416.29 km2, accounted for about0.31% and it is about 477.48 km2, accounted for about0.33% in 2010.(2) Analysis on the hydrological and sediment effect from 1955 to 2010 in Poyang Lake WatershedThe total sediments loaded into Poyang lake from the main five tributaries was about 811.687 Mt during 1955 to 2010, in which Gan River(accounted for 59.7%) > Xin River(accounted for 13.7%) > Xiu River(accounted for 10.2%) > Fu River(accounted for 9.7%) > Rao River(accounted for 6.7%); And the inputted sediments were synchronized to the water discharge seasonally. The total sediments loaded into Yangtze River from Poyang Lake was about 560.103 Mt during 1955~2010. And it showed a decreasing trend during 1955~2000, but the trend was interrupted by the practice of sand mining in the new century.(3) Analysis on influence factors of inputted sediments change in Poyang Lake Watershed by five tributariesClimate change and human activities is the main reason affect basin sediment load.The annual sediments loaded into Poyang Lake was mainly decided by water discharged into Poyang Lake. Sediments loaded into Poyang Lake decreased sharply caused by reservoir interception, though forest coverage changes also contribute to the decrease of sediments.(4) Analysis on influence factors of outputted sediments change in Poyang Lake BasinAffected by the backflow from Yangtze River in flood period, sediments loaded into Yangtze River were asynchronous with water discharge seasonally. And the sediments loaded by the backflow from Yangtze River was reduced dramatically because of the emplacement of Three Gorges Dam; The sediments budget in Poyang Lake was changed by sand mining. Sediments deposit was estimated about 1.408mm/a during 1955~2000, but outputted sediments showed greater than the inputted sediments during 2001~2010 because of the practice of sand mining.