The revered Ganga River, a cultural and economic cornerstone for more than 600 million people across South Asia, is facing an alarming crisis: it is drying faster than it has in over a millennium. This dire warning comes from a groundbreaking study conducted by researchers at IIT Gandhinagar and the University of Arizona. Their findings indicate that the river’s flow has declined at an unprecedented rate since the 1990s, a trend primarily attributed to a combination of weakening summer monsoons, human-induced alterations in land and water use, and broader global climate shifts.
Should these critical findings be further corroborated, it would mean the Ganga has entered a period of more severe and prolonged droughts than even the significant arid spells recorded in the 14th and 16th centuries. This has profound implications, considering the Ganga basin alone contributes a staggering 40% to India’s Gross Domestic Product.
To arrive at these conclusions, the research team meticulously combined historical tree-ring data from the Monsoon Asia Drought Atlas with advanced hydrological models. This innovative approach allowed them to reconstruct the river’s streamflow dating all the way back to 700 AD, effectively bridging a crucial gap in long-term hydrological records. The accuracy of their reconstruction was then rigorously verified against documented historical droughts and famines, including the devastating Bengal famine of the 18th century, as well as modern-day data. Finally, these reconstructions were compared with various climate model projections to ascertain whether the observed drying could simply be explained by natural climate variability.
The study specifically highlighted the period between 1991 and 2020, revealing that the Ganga basin endured multiple droughts lasting four to seven years – events that were considerably rarer throughout the preceding millennium. The drought that occurred from 2004 to 2010 emerged as the most severe in 1,300 years. Collectively, the post-1990s drying trend was estimated to be 76% more intense than the worst drought recorded in the 16th century. Rigorous statistical analyses confidently confirmed that this significant decline cannot be solely explained by natural climate variability. Instead, the evidence points to a combination of factors: weaker monsoons linked to rapid warming of the Indian Ocean, increased aerosol pollution, reduced baseflow due to excessive groundwater pumping, and widespread changes in land use.
The research paper, published on September 23, also raises serious questions about the reliability of current global climate models, many of which fail to accurately predict this observed drying trend. This suggests that even as some climate models forecast wetter conditions in the future, relying solely on optimistic predictions for water planning would be imprudent. Instead, future water management strategies must be adaptive and account for both natural climatic cycles and significant human-driven factors. The study starkly highlights the severe vulnerability of the basin’s vast population, with declining streamflow threatening agricultural stability and impacting the delicate marine ecosystem of the Bay of Bengal, which relies heavily on the river’s discharge.