The majestic Ganga River, a lifeline for over 600 million people and a cornerstone of South Asia’s economy and culture, is facing an unprecedented crisis. A new study by researchers from IIT Gandhinagar and the University of Arizona reveals that this vital waterway is drying at a rate not witnessed in more than a millennium. The drastic decline in streamflow observed since the 1990s is alarming, linked to a complex interplay of weakening summer monsoons, human alterations in land and water use, and wider climate shifts.
If these findings are further corroborated, the Ganga is entering an era of droughts far more prolonged and severe than those recorded in the 14th and 16th centuries. Given that the Ganga basin contributes a staggering 40% to India’s GDP, the implications are profound for the nation’s economic stability and the well-being of its vast population.
To understand this critical trend, the researchers meticulously reconstructed the river’s streamflow dating back to 700 AD. They achieved this by integrating tree-ring records from the Monsoon Asia Drought Atlas with sophisticated hydrological models, effectively bridging a significant gap in historical flow data. This reconstruction was then rigorously validated against documented historical droughts and famines, including the devastating Bengal famine of the 18th century, as well as against contemporary data. Finally, these historical insights were compared with climate model projections to determine if natural climate variability alone could explain the current drying.
The study unearthed a disturbing pattern: between 1991 and 2020, the Ganga basin endured multiple droughts lasting four to seven years – a frequency significantly higher than observed throughout the preceding millennium. The period from 2004 to 2010 stands out, marking the most severe drought in 1,300 years. Overall, the intensity of drying experienced post-1990s was estimated to be 76% greater than even the worst drought of the 16th century. Statistical analyses strongly indicate that this decline cannot be attributed solely to natural climate fluctuations. Instead, the evidence points to a combination of factors: weaker monsoons influenced by rapid Indian Ocean warming and increased aerosol pollution, reduced baseflow due to extensive groundwater pumping, and widespread land-use changes.
Crucially, the team’s findings also raise questions about the accuracy of current global climate models, many of which fail to reflect this observed drying trend. While some climate models optimistically predict wetter conditions in the future, their inability to accurately simulate recent drying means that future planning cannot solely rely on such hopeful forecasts. Instead, water management strategies must be adaptive, thoroughly considering both natural environmental shifts and human-induced pressures.
This comprehensive research powerfully underscores the vulnerability of the Ganga basin’s inhabitants. From threatening agricultural livelihoods to impacting the delicate marine ecosystem of the Bay of Bengal, which relies heavily on the river’s discharge, the consequences of a shrinking Ganga are far-reaching and urgent.