The Material Flux Spatiotemporal Variation And Mechanism Of Different Rivers Originated From The Tibetan Plateau

Many large rivers in Asia originate from the Tibetan Plateau.The changes of rivers not only reflect the changes on the Tibetan Plateau,but relate to the water resources utilization in the basin countries closely.The flux changes of terrestrial materials entering the sea could reveal the basins ecological environment pressure and its demand for water,energy and other resources,also impacted the sedimentary evolution of the topography and the sustainable development of the basin's ecological environment.Because of the differences of basin natural conditions,the impact of human activites is also different.Combing the basin social development,we discuss the temporal changes and mechanism of material fluxes of the main rivers which originated from the Tibetan Plateau,which of great guiding significance for regional and even global scale watershed research.Meanwhile,masterring the material flux foundation data of each basin is significant for management departments to build a basin of common destiny and use water resources reasonably and effectively.In this resarch,material flux was tried to compare quantitatively by analysis of the water discharge,sediment load,nutrient elements volumes such as nitrogen,phosphorus and silicon in the Yangtze,Yellow,Mekong,Indus,Ganges,Brahmaputra,Red river and Amu Darya.In addition,the mechanism of variation was discussed by the compassion of two phases of land use and land cover in 1995 and 2015,which were extracted from the remote sensed image mapping in corres.Relied on geographic information systems and computer technology,a data management system for material flux was built.The main conclusions are as follows:(1)The water discharge of the main rivers from the Tibeten Plateau have large differences,and in these rivers,sediment load decreased but nitrogen and phosphorus increased significantly.The runoff and sediment load have similar patterns of high and low cycles,but the change of the sediment yields is higher than that of the runoff.Interannual coefficient of variation indicates that the Yellow,the Indus river and the Amu Darya have a high degree.The runoff depth is relatively small in the middle and high latitudes,the highest runoff depth delivered by the Brahmaputra(1122.9 mm),while the lowest is delivered by the Amu Darya(26.5 mm).There is a significant positive correlation between the topographic relief of the basin and the sediment yields of the basin.The sediment yields of the Yellow River is the largest(850 t/km~2)and the Amu Darya is the smallest(40 t/km~2).(2)Human activities have become the major cause of river flux changes,correlation between precipitation and water and sediment discharge shows poor consistency.Dams construction and land use changes in the basin have a significant impact on river fluxes.According to the population density,per capita GDP,the proportion of cultivated land and construction area,and the watershed infrastructure of the river basin,the Analytic Hierarchy Process(AHP)was used to evaluate the social development stage of the basin.Five phases were divided according to the evaluation level,which are the acceleration phase,the takeoff phase,the start phase,and the initial phase.Among them,the Yangtze river and the Yellow river are the mature stage and the acceleration stage respectively.The Mekong river and the Indus river are the takeoff stages,while The Ganges River,the Brahmaputra River and the Red River are the starting stages.The Amu Darya is the primary stage with the lowest score.The start-up and primary stage watersheds are mainly dominated by agriculture.The water facilities mainly serve agricultural irrigation.The flow of water in the basin and the flow of the inner diameter of the river basin are correspondingly reduced.The total amount of nitrogen and phosphorus in the Yangtze River Basin at the mature stage is significantly higher.(3)Using the GIS method and computer technology to build a spatial information management system for rivers into the sea.Efficient and scientific integrated management of spatial and non-spatial geographic data,realizing the input and output of river-to-sea material fluxes and river basin socio-economic data,additions,deletions and changes,and generating thematic map products according to demand,realizing river hydrology and Effective management and comparative analysis of natural and human economic data in river basins.