Increased glacier melt enhances future extreme floods in the southern Tibetan Plateau

Abstract

Mountainous areas on the Tibetan Plateau (TP) are of particular hydrological concern as topography and atmospheric conditions can result in large and sudden floods, and pose critical threats to water-related safety and sustainability in neighboring countries. The Yarlung Zangbo (YZ) river basin is the largest river basin on the southern TP, but the ways in which flood discharges in this basin will evolve under 21st-century climate change and the effect of precipitation extremes and glacier melt remain unclear. Here, we comprehensively quantify the future evolution of extreme flood frequency and intensity under 21st-century climate change, and determine the predominant drivers of flood changes in the YZ basin. We show that total runoff is projected to increase owing to continued wetting throughout the 21st century under two different shared socioeconomic pathways (SSPs) in the YZ basin. Both the frequency and intensity of flood extremes are projected to increase under both SSPs, primarily driven by enhanced total days and magnitude when daily precipitation estimates > 95th percentile. Glacier melt is projected to enhance the intensity and frequency of extreme floods by 12%–23% under both SSPs. This study aims to close the knowledge gap regarding future flood risks in the TP’s rainfall- or meltwater-impacted basins.