Ganga's worst dry spell in 1,300 years: A crisis for 600 million people, warns IIT study

The Ganga, a lifeline for over 600 million people across India, Nepal, and Bangladesh, is undergoing its most severe drying phase in 1,300 years and faces major hydrological changes under future warming, according to a study published in the Proceedings of the National Academy of Sciences (PNAS).

As reported by The Times of India, the findings raise serious concerns for water security, agriculture, and power generation in one of the world’s most densely populated regions.

Researchers from IIT Gandhinagar and the University of Arizona reconstructed the Ganga’s streamflow over the past 13 centuries using instrumental data, paleoclimate records and advanced hydrological models. Their analysis showed that the river’s decline since the early 1990s has been more severe than even the mega-droughts of the 16th and 18th centuries. “The Ganga has faced frequent and prolonged droughts in the last three decades, with the 2004-2010 drought ranking as the most severe in over a millennium,” said lead author Dipesh Singh Chuphal of IIT Gandhinagar, as quoted by ToI.

Between 1991 and 2020, the basin experienced two unprecedented seven-year droughts, 1991-97 and 2004-10, both ranking among the “ten longest droughts in the basin’s 1,300-year history,” the study noted. While droughts were primarily tied to natural monsoon variability, the research stressed the growing influence of human-driven factors. Weakening summer monsoons, partly due to Indian Ocean warming and aerosol pollution, have reduced basin rainfall by nearly 10% since the 1950s, with western regions seeing declines of over 30%.

The study warned that rising temperatures could exacerbate these changes. "Reduced summer monsoon rainfall is the primary driver of declining river flow, while warming has a smaller impact. However, under extreme climate scenarios, if rainfall deficits combine with higher temperatures, streamflow could fall sharply, by 5% to 35%," it stated.

Excessive groundwater extraction to offset unreliable rainfall has further depleted the river, cutting baseflow and worsening summer drying. The combined effects of falling rainfall and unsustainable groundwater use, the researchers cautioned, are “pushing the Ganga beyond its natural limits.”

The consequences are already visible. Between 2015 and 2017, historically low water levels hit drinking water supplies, irrigation, power generation and navigation, affecting more than 120 million people. Declining freshwater discharge is also reducing nutrient flow into the Bay of Bengal, threatening one of the world’s most productive marine ecosystems.

Adding to the concern, most global climate models fail to capture this drying trend, with many projecting increased streamflow under warming scenarios due to anticipated rises in precipitation. Only a few models mirror the observed decline, raising questions about the reliability of future forecasts.

"Future water security in the Ganga basin will depend on how effectively we integrate climate science with policy and local water management," said co-author Vimal Mishra, professor at IIT Gandhinagar, as quoted by ToI.

Some projections suggest increasing rainfall under climate change could reverse the drying by 2040, but the researchers warned that without curbing unsustainable groundwater use, such a recovery may not occur.

The Ganga basin contributes about 40% of India’s GDP and sustains the country’s agricultural heartland. With prolonged droughts becoming more frequent, the study urged urgent reforms in water governance, better monsoon forecasting, and sustainable groundwater management, ToI reported.

With inputs from ToI