If the Ganga really should disappear, it will be not because Lord Shiva kept it from flowing down his matted locks, but because it cannot exist in a climate-changed world, in a world alien to it and alienated from it.
The Ganga is not disappearing, not yet. It has had, however, severe drought years due to failed monsoons. The years between 1344 and 1355, the Bengal famine of 1770, the famine of 1802 that affected Bombay Presidency—all of them were very dry, interspersed with rainy years.
Topping all of these, the drying from 1991 to 2020 is the worst in more than a thousand years, according a new study published in the journal The Proceedings of the National Academy of Sciences (PNAS) by researchers at the Indian Institute of Technology (IIT) Gandhinagar and the University of Arizona.
“The Ganga River basin is drying faster than ever before, putting the water and food security of over 600 million people at serious risk,” Dipesh Singh Chuphal tells Hot Rock. He is a PhD research scholar at IIT Gandhinagar and lead author of the paper.
With the help of 1,300 years of data from paleo-hydrological records, historical evidence, and hydrological models, the researchers reconstructed long-term (700-2020 C.E.) streamflow for the Ganga and found that this decline extends beyond natural variability, indicating a significant human influence.
Lack of rainfall over the region for long led to “the frequent occurrence of severe streamflow droughts that caused the drying.” The term “drying” in this study specifically refers to hydrological drying—that is, a decline in streamflow (river discharge) over time.
In addition to significant reduction in precipitation over the region, excessive ground water pumping in the Ganga basin dented baseflows. Chuphal says that although global climate models (CMIP6) predict increased river flow with global warming, the current drying trend suggests a more complex situation.
The main takeaways from the study are:
1. Recent drying from 1991 to 2020 is unmatched in the last 1,300 years.
2. Severe and prolonged streamflow droughts caused the drying trend.
3. Current climate models fail to capture the drying trend in streamflow.
Talking about the method they used to put it together, Chuphal says they reconstructed long-term streamflow for the Ganga basin by combining observed streamflow, paleoclimate data, and hydrological modelling. To extend the record back to 700 CE, they incorporated paleo-hydrological proxies—mainly tree-ring-based drought indices from the Monsoon Asia Drought Atlas (MADA)—that reflect past monsoon rainfall and drought conditions.
To get a continuous 1,300-year streamflow reconstruction, they set up a log-linear model between annual streamflow and MADA predictors. They then compared it with observed data and known historical drought-induced famines. Then they analysed multi-year low-flow periods using run-length and magnitude statistics to compare recent drying (1991–2020) with past variability.
Chuphal says “this integrated, multi-source approach is considered robust because it cross-checks different data types and aligns with historical drought evidence, though uncertainties remain due to proxy limitations and long-term changes in basin conditions.”
What drying does to the river itself is far-reaching. Chuphal says it transforms the river from a dynamic, flowing system into a fragmented and stressed waterway, disrupting its natural physical processes, loss of connectivity, altered sediment and nutrient dynamics, reducing water quality, and undermining its ability to support life.
The impact the recent drying of the Ganga cascades across and down into multiple realms. Though Ganga is among the top rivers globally in terms of total volume of water, recent drying has caused severe socio-economic implications.
Chuphal catalogues how devastating the drying has been. Between 2015 and 2017, historically low water levels in the middle and lower reaches severely disrupted drinking water supply, power generation, irrigation, and navigation, impacting over 120 million people. This trend has worsened the already stressed groundwater resources in the region, creating a negative feedback loop that threatens streamflow, as a substantial portion of the Ganga’s flow depends on baseflow from groundwater. Additionally, reduced river discharge has diminished freshwater inflow into the Bay of Bengal, potentially endangering one of the world’s most productive marine ecosystems.
For ecosystems, reduced flow shrinks aquatic habitats, disrupts fish migration and breeding, degrades wetlands, and concentrates pollutants, threatening biodiversity. For people, it causes water shortages, lowers agricultural productivity, reduces fishery and livelihood opportunities, worsens water quality and health risks, and disrupts cultural and religious practices dependent on the river.
“Drying undermines the river’s role as a life-support system, stressing both nature and the communities that depend on it,” Chuphal says.
The researchers caution that if the drying persists for a longer period, it will impact the food, water, and energy security of the region.
Groundwater depletion will worsen as communities pump more water due to river drying, creating a long-term scarcity cycle. The Ganga holds deep spiritual and cultural importance. Low water levels in sacred stretches (like Varanasi) affect rituals, festivals, and pilgrimage activities that rely on flowing water. Reduced flows cannot wash off pollution and help in concentrating pollutants as real-life experience at pilgrim centres such as Varanasi and tanning centres such as Kanpur show.
The drying also affects GDP as the region contributes approximately 40 per cent of India’s GDP. The study calls for urgent research into how climate patterns and human actions affect the summer monsoon.
“Improving how these factors are represented in climate models is crucial for more accurate monsoon forecasts and informed water management to protect the Ganga basin’s water resources in a changing climate,” Chuphal tells Hot Rock.
