Unprecedented drying of the Ganga River over the past 1,300 years

The Ganga River basin is home to over 600 million people and holds significant economic and cultural importance. However, the Ganga River is experiencing a recent drying trend, threatening both water and food security. Using streamflow reconstructions spanning 1,300 y (700–2012 C.E.) from instrumental data, paleohydrological records, and hydrological modelling, we show that recent drying from 1991 to 2020 is unprecedented in the past millennium. Streamflow decline since the 1990s, driven by frequent and prolonged droughts, is 76% more intense than its closest historical analogue of the 16th-century drought. This drying exceeds natural variability, highlighting the dominant role of anthropogenic factors. Despite CMIP6 models projecting increased streamflow under warming scenarios, the recent decline indicates complexities associated with future water availability projections. Our findings underscore the urgent need to examine the interactions among the factors that control summer monsoon precipitation, including large−scale climate variability and anthropogenic forcings. Better constraints on these processes in climate models will be essential for improving future monsoon projections and implementing adaptive water management strategies to secure the Ganga basin’s freshwater availability under a changing climate.