Vegetation greening concurs with increases in dry season water yield over the Upper Brahmaputra River basin

Water yield (WY) in the Upper Brahmaputra River (UBR) basin is important for sustaining the ecological environment in the headstream region and supplying valuable freshwater resources downstream. While recent studies indicated the presence of warming and greening trends in the region, the effects of these changes on WY are not yet understood. Here, on the basis of the Budyko framework and a random forest model, we assess the relative importance of climate and vegetation on WY changes in the UBR basin. We find that precipitation contributes to over 90% of the increase in annual WY, and is also the most important factor for WY during the wet season. During the dry season, however, vegetation, rather than precipitation, predicts the variability in WY. We suggest that vegetation may have changed the seasonality of water by storing water in the wet periods and releasing it in dry periods, which explains why WY increases significantly during the dry season. Our findings imply that vegetation greening in the UBR basin has the potential to increase drought resilience downstream, and protect food security from drought, highlighting the value of ecological restoration for water resource management.