An integrated assessment of water scarcity and glacier runoff changes in Asian and South American glacierized basins

Abstract Non-technical summary This study looks at future water deficit in glacier-fed river basins in Asia and the Andes under three possible global development pathways. The results show that a world with high population growth and low technological progress faces the greatest water stress. Scenarios with better technology or lower climate impacts reduce water deficits. Glacier meltwater increases temporarily under stronger warming but declines later in the century. Overall, the study highlights the need for climate mitigation and better water management to reduce future water scarcity. Technical summary This study assesses water scarcity in selected glacierized basins across Asia and the Andes under three Shared Socioeconomic Pathway (SSP) scenarios (SSP1-2.6, SSP3-7.0, and SSP5-8.5). Using a novel integration of the Open Global Glacier Model (OGGM), the Xanthos hydrological framework, and the Global Change Assessment Model (GCAM), we estimate water availability and demand while accounting for glacier runoff and its temporal dynamics. Results reveal SSP3-7.0 as the most water-scarce scenario due to high water demand , higher population and low technological development. Instead, SSP5-8.5 results in slightly lower water scarcity risks than SSP3-7.0 due to its higher technological efficiency and lower population. Finally, SSP1-2.6 results in lower cumulative surface water deficits due to lower climate change impacts, better water and energy technology, and lower population. Glacier runoff has a peak in its contribution under severe climate scenarios (SSP3-7.0 and SSP5-8.5) and experiences a decline in the second half of the 21st century. The findings underscore the importance of effective mitigation to avoid peak-water occurrence under high emissions scenarios and adaptation measures, such as improving irrigation efficiency and reducing withdrawals, to address anthropogenic-induced water scarcity. Social media summary Increase water scarcity and glacier runoff decline under severe climate change scenarios in Asian and Andean basins.