Modeling Study On Runoff In Yarlung Tsangpo River Basin

The Yarlung Tsangpo River is located in the Tibet Plateau and is a high-altitude cold basin.The runoff of the Yarlung Tsangpo River,which is composed of glacier melting,snow melting and rainfall,has a complicated response to climate change.Its future trend has a strong uncertainty,and will affect the development and utilization of water resources and hydropower resources.Therefore,it is of a great significance to explore the analytical methods of runoff components and reveal the evolution of runoff under climate change in the Yarlung Tsangpo River Basin to understand the future water resources and make scientific decisions.The key scientific issue that this study addresses is the formation and evolution of the Yarlung Tsangpo River's runoff.The satellite precipitation products are evaluated and integrated on the basis of high-quality ground rainfall gauges to obtain the high-precision satellite precipitation fusion dataset in the study basin and its surrounding areas.Then we divide the composition of runoff based on the hydrograph partitioning curves.Based on the analysis of distributed hydrological model,the understanding of the water source composition of the Yarlung Tsangpo River's runoff is deepened.We provide a comprehensive and updated assessment of the impacts of climate change on Yarlung Tsangpo-Brahmaputra River(YBR)runoff by integrating a physically based hydrological model,regional climate integrations,different bias correction methods,and Bayesian model averaging method.First,we collect the meteorological data,hydrological data and underlying surface data,and analyze the interannul changes of glaciers on different hydrological control sections.We also conduct an analysis of the multi-year water balance in different outlets of Yarlung Tsangpo River to evaluate different precipitation and evaporation datasets.We get water components under the condition of optimal water balance above the control hydrological stations of basins during 1980-2004.Precipitation is the key to simulation and prediction of runoff changes.We collect high-quality rainfall gauges data and 5 widely used satellite precipitation products in the southeastern part of the Yarlung Tsangpo River Basin in Tibet Plateau.We use the dynamic Bayesian model averaging method to integrate satellite precipitation products to form a fusion dataset and verify its performance in various aspects.This dataset fills the gap in high-quality rainfall data in the plateau region.To reveal the composition of the Yarlung Tsangpo River's runoff,we divide the composition of runoff based on the hydrograph partitioning curves(HPC),and establish distributed hydrological model as well as parameter datasets.Based on the analysis of distributed hydrological model,the understanding of the water source composition of the Yarlung Tsangpo River's runoff is deepened.It shows that the rainfall runoff accounts for 66.0% of total runoff above Nuxia hydrological station,snowmelt runoff accounts for 20.0%,and glacier melting runoff accounts for 14.0%.We provide a comprehensive and updated assessment of the impacts of climate change on YBR runoff by integrating a physically based hydrological model,regional climate integrations,different bias correction methods,and Bayesian model averaging method.It is estimated that by the year of 2035,the annual mean runoff is projected to change respectively by 6.8%,-0.4%,and-4.1% under RCP4.5 relative to the historical period(1980-2001)at the Bahadurabad in Bangladesh,the upper Brahmaputra outlet,and Nuxia in China.Under RCP8.5,these percentage changes will substantially increase to 12.9%,13.1%,and 19.9%.The change rate of runoff shows strong spatial variability along the YBR from downstream to upstream.