Ganga drying at fastest pace in 1,300 years - study warns of unthinkable consequences

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The Ganga, lifeline of over 600 million people, is experiencing its most severe drying spell in 1,300 years and could face significant hydrological shifts with rising global temperatures, according to a new research.

As per a report by The Time sof India, the findings raised grave concerns for water security, agriculture and power generation across India, Nepal and Bangladesh.

The study was led by researchers from IIT Gandhinagar who reconstructed the streamflow history from 700 to 2012 CE using the Monsoon Asia Drought Atlas, as well as ancient climate records and computer models. The analysis published in peer-reviewed journal PNAS revealed that one of the country’s largest river basin faced frequent and prolonged droughts in recent decades, especially from 1991 to 2020, when it was the most extreme.

“Streamflow has fallen significantly since the 1990s because of more frequent and longer drought. The decline in flow during this period was 76 per cent worse than the 16th century drought, the most similar event in the past. This drying is also unusually severe to be caused by natural variability alone, and seems to be driven largely by multiple factors, including monsoon and human activities, which require further study," co-author Professor Vimal Mishra from IIT Gandhinagar was quoted by News18 as saying.

The changing dynamics in the largest river basin has implications for water and food security in the region, as well as Nepal and Bangladesh where the river flows. For instance, during 2015-17, historically-low water levels across the middle and lower reaches of the Ganga river severely disrupted drinking water supply, power generation, irrigation, and navigation affecting over 120 million people.

Erratic monsoon: Recurring floods and droughts

Interestingly, the study challenges recent climate models that predict higher streamflow with warming. As global temperatures climb, scientists remain divided on whether the southwest monsoon is weakening or strengthening over the Ganga basin. What they agree on, however, is that shifting rainfall patterns will sharply affect the region’s water availability.

“Future projections are far more complex, and this only highlights the challenges of predicting future water supply in the region. Overall rainfall over the entire basin is influenced by many factors – irrigation, aerosols, that most climate models often overlook or underrepresented," Professor Mishra added.

A 2024 study by IISER Bhopal revealed that while short bursts of extreme rainfall have risen across much of the Ganga basin since 1960 — heightening flash flood risks — the overall rainfall volume has declined, particularly in the eastern Indo-Gangetic plains and southern sub-basins such as the Chambal, Betwa, Tons, and Sone, pointing to more frequent droughts. In contrast, the Himalayan stretches — including the upper Ganga, Yamuna, and Ghagra — have witnessed an increase in rainfall intensity, volume, and duration over the same period.

Another important study by IITM Pune in 2015 threw light on the decreasing land-sea thermal contrast, with rapid warming in the Indian Ocean and slower warming over the subcontinent. This could lead to significant weakening trend in summer rainfall over central-east and northern India (1901–2012), with weakened monsoon circulation, which reduced rainfall in key agricultural areas.

85% of annual rain during monsoon

The data revealed there have been more wet years than dry years during the last 1,300 years, but 1990 onwards, there were no extreme wet years in the Ganga river basin between 1991 and 2010, and only two extreme wet years between 2011 and 2020.

Overall, the basin has undergone unusual drying, likely driven by a weakening summer monsoon and more frequent, prolonged droughts in recent decades. With uncertainties still surrounding the southwest monsoon — which supplies over 75% of rainfall to the Indo-Gangetic basin — experts stress the need to identify the drivers behind the Ganga’s decline to safeguard this critical water source in a warming climate.

“Our study highlights the need to better understand how different factors like large climate patterns, and human activities, aerosol emissions, irrigation affect the summer monsoon. Improving climate models with this knowledge is crucial to making accurate forecasts and managing water resources to protect the Ganga basin’s water in a changing climate," the team was quoted by News18 as saying.