A groundbreaking study has revealed that the Ganga River, long believed to be sustained by Himalayan glaciers, actually draws most of its flow from groundwater across the Gangetic Plains. The discovery reshapes scientific understanding of India holiest river and carries major implications for its conservation and long-term survival.
Published in Hydrological Processes the study led by Professor Abhayanand Singh Maurya from IIT Roorkee is the first detailed isotope-based research proving that groundwater is the dominant contributor to the Ganga’s flow. As the river travels from the Himalayas to the Bay of Bengal, groundwater boosts its volume by nearly 120%, far surpassing the contribution from glacier and snowmelt.
Maurya explained that while glaciers and snowmelt sustain the upper stretches, “the river beyond the Himalayan foothills is mostly groundwater-fed.” His team collected samples from 32 sites between Devprayag where the Bhagirathi and Alaknanda merge and Howrah, analyzing oxygen and hydrogen isotopes to track groundwater’s influence.
The findings show that for nearly 1,200 kilometres through the Gangetic Plains home to over 400 million people groundwater sustains the Ganga’s summer flow.
While the Gangotri Glacier has lost around 10% of its snowmelt contribution in four decades due to climate change, researchers note that this loss, though concerning, does not pose the greatest threat to the river’s survival. Professor Abhijit Mukherjee of IIT Kharagpur said, “Glaciers are visible, so people assume they are the Ganga’s lifeline. But the invisible groundwater is what truly keeps the river alive.”
Environmental expert Ravi Chopra agrees, observing that glaciers ensure the Ganga perennial nature but cannot sustain its entire 2,525-kilometre journey. Much of the river’s year-round flow, he said, comes from groundwater and rainfall.
However the study warns that excessive groundwater extraction, shrinking glacial inflows, and overuse for agriculture and urban supply are destabilizing the river’s natural system. Maurya also noted that more than half of the Ganga’s water evaporates in the middle plains and that pollution and encroachment have reduced flows from smaller tributaries.
Ruchi Badola, dean at the Wildlife Institute of India, pointed out that groundwater conservation is now part of the Namami Gange mission but stressed that tributary and catchment area protection is equally vital. “Rivers live through groundwater. If tributaries and aquifers are not protected, the Ganga cannot survive,” she said.
Experts recommend urgent measures such as increasing water release from barrages, enhancing groundwater recharge, harvesting rainwater, and curbing sewage and industrial waste discharge into the river.
As Professor Maurya concluded, “Big rivers depend mostly on groundwater. To keep the Ganga alive, we must first save the water beneath our feet.”
The study serves as a crucial reminder that the Ganga’s real lifeline lies not in the melting ice of the Himalayas, but in the hidden veins of groundwater sustaining it silently below the plains.