Spatial patterns of sediment load in the Yarlung Tsangpo River: Transport‐deposition in the middle reach and a ‘sediment factory’ in the lower

Abstract

The spatial distribution of suspended sediment load is a key indicator for watershed management by identifying primary sediment source areas and elucidating transport‐deposition patterns. However, clarifying such spatial patterns in alpine regions is challenging due to strong sediment heterogeneity and sparse hydrological monitoring data. Here, we focus on the Yarlung Tsangpo River and apply a global sediment simulator model to estimate mean annual suspended sediment loads at 17 cross‐sections along the mainstream and its tributaries. The model demonstrates good applicability in this region, with a high coefficient of determination ( R ²  = 0.97) between predicted and observed values. The sediment load exhibits significant spatial heterogeneity with a coefficient of variation (CV) of 1.31. A generally downstream increasing trend is observed, whereas the lower reach functions as a ‘sediment factory’ of the basin, contributing 92.9% of the sediment load (SL) at the basin outlet, with an average specific sediment yield (SSY) of 4495 t/km ² and a local maximum of 18 629 t/km ² . In contrast, the middle reach contributes only 5.9% of the sediment load and exhibits a high modern deposition rate of 81 Mt/a, far exceeding the sediment export of 14.36 Mt/a. Transport and deposition zones alternate spatially, with deposition predominantly occurring at tributary confluences and upstream of riverbed knickpoints. These insights advance the understanding of sediment production and transport mechanisms in complex alpine river systems and support informed water resource development.