Groundwater Is Ganga's Lifeline In Summer, Not Glacial Melt: IIT Study Finds
IIT Roorkee's isotopic and hydrological study claims that Ganga's summer flow is primarily sustained by groundwater, which boosts river volume by almost 120 per cent.
Published : August 2, 2025 at 11:32 AM IST
New Delhi: The river Ganga, originating from the Gangotri Glacier in Uttarakhand as the Bhagirathi and joining the Alaknanda at Devprayag, flows 2,525 kilometres through northern India and Bangladesh, forming a vast 1-million-square-kilometre basin that supports over 400 million people and diverse ecosystems. A new study led by researchers at the Indian Institute of Technology (IIT) Roorkee sheds new light on the river, suggesting that it is primarily sustained by groundwater discharge and not glacial melt, as widely believed.
Published in the journal Hydrological Processes, the paper discusses the summer water dynamics of the Ganga throughout its course, giving an estimation of evaporative loss from river channels, groundwater interaction, and the role of aquifer water levels in sustaining river flow.
According to the study, the natural underground contribution boosts the river’s volume by nearly 120 per cent of its initial volume along the middle stretch, which is around 1,200 km long and is a crucial region for agriculture and industry.
The study also claims that around 58 per cent of the river's initial water volume at the segment's start is lost to evaporation during summer, an alarming component of the river's water budget. However, the middle plain exhibits the most significant river–groundwater interaction as aquifer discharge increases the river's volume more than its origin, glacial melt.
Two decades of in situ data—including meteorological data, calibration metrics, and stable isotope analysis, as well as data related to groundwater level changes around the river—show stable groundwater levels across most of the central Ganga Plain, suggesting that reduced summer flow is driven by other factors such as increased human activities rather than groundwater depletion.
The study highlights that glacial melt plays a negligible role in sustaining the Ganga’s summer flow across the Indo-Gangetic plains, especially beyond the Himalayan foothills, with major tributaries like the Ghaghara and Gandak becoming primary contributors after Patna. Contrary to earlier satellite-based reports suggesting widespread groundwater depletion, a full-scale isotopic analysis revealed largely stable groundwater levels in the central Ganga Plain.
The consistent output from shallow hand pumps over decades further supports the presence of resilient aquifers that continue to nourish the river outside of monsoon seasons. Researchers from IIT Roorkee emphasise that the Ganga’s diminished flow stems not from groundwater loss but from over-extraction, excessive diversion, and the neglect of tributaries. Therefore, rejuvenating the river demands restoring tributaries, enhancing environmental flow from barrages, and safeguarding local water bodies to recharge aquifers.
This case study, through its mathematical modelling and river water-groundwater interactions, also provides a framework that can be applied to other tropical rivers to understand water dynamics and guide sustainable management practices.
