Ganga sustained in summer by groundwater discharge, not glacial melt: IIT study
The pioneering study published in the journal Hydrological Processes based on a full-scale isotopic analysis of the Ganga from its Himalayan origins to its deltaic end, including its major tributaries, offers a paradigm shift in understanding how the mighty river is sustained during the hot and dry summer months.
The study challenges long-held assumptions by establishing that up to Patna in Bihar, the Ganga is primarily sustained by groundwater discharge and not glacial melt.
This natural underground contribution boosts the river's volume by nearly 120 per cent along the middle stretch.
Meanwhile, more than 58 per cent of the river's water is lost to evaporation during summer—an alarming yet overlooked component of the river's water budget.
'Our analysis shows that the Ganga is not drying because groundwater is depleting, but due to over-extraction, excessive diversion, and neglect of tributaries. Groundwater is still the hidden lifeline of the Ganga," said Prof Abhayanand Singh Maurya, lead author and faculty at the Department of Earth Sciences, IIT Roorkee.
'This research redefines how we can understand the Ganga's summer flow. It should prove a sustainable future river rejuvenation strategy, not just for the Ganga but for all major Indian rivers," he said.
The study concludes with the message: 'If India wants a sustainable Ganga, it must protect and recharge its aquifers, release adequate water into the main river channel, and revive the lost tributary networks." Contrary to prior satellite-based studies warning of severe groundwater depletion across north India, the new findings based on two decades of in-situ data indicate largely stable groundwater levels across the central Ganga Plain, Maurya said.
Consistent flows from shallow hand pumps across decades reinforce the evidence of a resilient aquifer system that continues to feed the Ganga during non-monsoon periods, he said.
Another revelation made by the study is the negligible role of glacial melt in maintaining the Ganga's flow in the Indo-Gangetic plains during summer.
The study quantifies that beyond the Himalayan foothills, the glacier-fed input is virtually absent and does not influence the summer discharge up to Patna.
Post-Patna, tributaries like Ghaghara and Gandak become the dominant contributors.
The research adds valuable scientific weight to several ongoing national missions such as Namami Gange, Atal Bhujal Yojana, and Jal Shakti Abhiyan, which aim to rejuvenate rivers and improve groundwater management. PTI ALM VN VN
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