Temporal changes and spatial distributions in suspended sediment runoff in the Yarlung Zangbo River, China

Abstract:

Significant researches have recently been conducted regarding the spatiotemporal change in suspended sediment concentration (SSC) in a river system throughout the world. It is of great important for quantification regional erosion severity and their dependencies with impact factors. SSC in rivers is highly variable in time and space, reflecting both variations in river discharge and in the suspended sediment supply. The Yarlung Zangbo River is the longest river in Tibetan Plateau and the highest river in the world. The high water drop and topography variability in the river basin inevitably leads to significant different river morphology and hydrological and sediment processes from upstream to downstream. The study of suspended sediment in Yarlung Zangbo River has been a highlighting problem in Tibetan Plateau wide study of sediment yields. In this study, we analyze temporal changes and spatial distributions in suspended sediment runoff using daily observation data from different sections in the river. The temporal processes show that as increasing of annual precipitation and temperature along the downstream direction, as well as main tributaries feeding in along the reaches, the discharge and SSC generally show more peaks, more fluctuated, and larger span for both rising and falling processes. Spatially, the river discharge as well runoff depth significantly increases along the downstream direction. The highest runoff depth in the downstream is 6 times than that in the upstream area; which is dominated by greatly increasing runoff amount from precipitation and melting water. The high erosion intensity occurred in middle reaches, as a center of intensive human activities and then after middle reach there is a deposition area. The erosion severity in the Yarlung Zangbo River, on the whole, is at a relative low level. Keywords: Yarlung Zangbo River, suspended sediment transport, soil erosion, Tibetan Plateau