1. What is the main source of the Ganga River’s summer flow?

The main source of the Ganga River’s summer flow, especially in the central Gangetic plains, is groundwater—specifically baseflow from aquifers—rather than Himalayan glacial melt, according to a peer-reviewed study by IIT Roorkee.

2. Is the Ganga River glacier-fed or groundwater-fed?

While the upper reaches of the Ganga originate from glacial sources like the Gangotri glacier, most of its downstream flow, particularly in summer, is sustained by groundwater discharge across the plains.

3. What is baseflow, and why is it important for the Ganga?

Baseflow is the portion of river water that comes from groundwater seepage into the riverbed. It's a vital component that keeps the Ganga flowing during dry months when rainfall and snowmelt are minimal.

4. What did the IIT Roorkee study on the Ganga River find?

The IIT Roorkee study used stable isotopes (δ¹⁸O and δ²H) to trace the water's origin and found that groundwater is the dominant contributor to the Ganga’s flow up to Patna, especially in summer.

5. How does groundwater affect the Ganga River's future?

Over-extraction of groundwater can reduce baseflow, threatening the long-term sustainability of the Ganga. If aquifers continue to deplete, parts of the river could eventually dry up during non-monsoon seasons.

6. Why is this discovery important for water policy in India?

This finding shifts focus from protecting glaciers to urgently managing and conserving groundwater resources. It calls for integrated river-aquifer management in national water policy and urban planning.

7. Are glaciers still important for the Ganga River?

Yes, glaciers play a crucial role in the headwaters of the Ganga, but their contribution significantly declines downstream. In the plains, groundwater dominates the river’s flow pattern.

8. What are δ¹⁸O and δ²H isotopes in hydrology?

δ¹⁸O (Oxygen-18) and δ²H (Deuterium) are stable isotopes used to trace the source of water. Different sources—glacier, rain, groundwater—have unique isotopic signatures, helping scientists determine the origin of river water.

9. How can we protect the Ganga’s baseflow?

Protecting the Ganga’s baseflow requires sustainable groundwater use, restoring aquifer recharge zones, preventing urban over-extraction, and integrating hydrology into river basin development plans.

10. Does climate change impact the Ganga River's flow?

Yes. Rising temperatures affect both glacier melt patterns and groundwater recharge rates. With groundwater now confirmed as the main contributor to summer flow, climate change poses a dual threat to the river’s long-term health.

Daylight photo of the Ganga River flowing through the central Gangetic plains with green landscapes — Ganga River in its middle reach, illustrating the area where groundwater dominates summer flows according to IIT Roorkee.

It’s Not Glaciers—Groundwater Is What Keeps the Ganga Flowing, Says IIT Roorkee

Contrary to the long-held perception that Himalayan glacier melt is the primary driver behind the Ganga River’s year-round flow, new research from IIT Roorkee presents a compelling alternative. Using isotopic hydrology techniques, scientists have confirmed that during the lean summer months, baseflow from regional aquifers—not ice melt—is what keeps the Ganga alive, especially through the...

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