Numerical simulation of sediment-laden flow on the Yarlung Zangbo River incorporating the climate change

The Yarlung Zangbo River originates from the Qinghai-Tibet Plateau, and runoff consists of the rainfall, melting of snow and glaciers in the upper high-altitude areas. The flow and sediment transport induced by flow in the Yarlung Zangbo River is highly sensitive to changes in climatic conditions. Changes in flow and sediment transport will also have an impact on the downstream wetland ecosystem. In order to study the changes of flow and sediment transport in the Yarlung Zangbo River, Niyang River wetlands under the changes of climatic conditions is used as the considered case. The two-dimensional shallow water equation and the non-equilibrium bedload sediment transport model are proposed in the Yarlung Zangbo-Niyang River. The model is discretized using the unstructured grid finite volume method (FVM). The model includes approximately 355 km length and covers an area of approximately 673 km(2). According to the measured time series of flow data at Nuxia hydrology station and the simulated data under the climate change conditions by the climate change model, the water level, flow velocity, erosion and siltation, and sediment gradation change in the river channel are calculated. The calculation results show that by the year 2025, the water level of Niyang River wetlands will increase by 2m under RCP8.5 (Representative Concentration Pathway), and accordingly the total area of the wetlands will decrease by 5%. The results show that climate change has a significant impact on the flow and sediment transport and downstream ecological environment of the Yarlung Zangbo River.