Gangotri Glacier study by IIT Indore reveals climate-driven shift in River Ganga’s water flow

Lucknow: A new scientific study has revealed that climate change is altering the water composition flowing from the Gangotri Glacier System (GGS), the source of the River Ganga in the central Himalaya.

Over the last four decades, researchers say, snowmelt contribution has declined, while rainfall-runoff and baseflow are gradually increasing — a trend that could reshape the river’s seasonal flows and impact millions dependent on its waters.

The study was carried out by the Glaci-Hydro-Climate Lab at IIT Indore and modelled streamflow from 1980 to 2020. Using the high-resolution Spatial Processes in Hydrology (SPHY) model, calibrated with field discharge records, geodetic satellite-based glacier mass balance data and snow cover maps, the researchers offered the most detailed breakdown yet of the glacier-fed river system.

According to the findings, snowmelt continues to dominate the Gangotri catchment, contributing 64 per cent of annual discharge, followed by glacier melt at 21 per cent, rainfall-runoff at 11 per cent, and baseflow at 4 per cent. But the balance has shifted over time. Snowmelt has been steadily declining, while rainfall-runoff and baseflow have inched upward.

Lead author Parul Vinze, a PhD scholar at IIT Indore, said the discharge peak shifted from August to July after 1990. “This shift is linked to reduced winter precipitation and earlier summer melting,” she explained. The change in peak timing, scientists warn, could upset irrigation cycles and energy production schedules that depend on a predictable water flow. Earlier research on Himalayan glaciers often relied on shorter time series, coarse climate data or limited calibration. This 41-year study, scientists argue, provides the clearest picture yet of how climate change is reshaping the Gangotri system.

Dr Mohd. Farooq Azam, who supervised the research, said accurate modelling backed by long-term field data is critical. “Predicting future water availability in the Himalaya depends on sustained monitoring. We also need to integrate high-resolution climate projections to refine forecasts,” said Dr Azam, senior intervention manager at the International Centre for Integrated Mountain Development (ICIMOD) and associate professor at IIT Indore.

The Ganga is not only a lifeline for over 400 million people but also revered as a sacred river in India.

At the basin-wide scale, the Ganga is relatively less dependent on glacier melt than rivers such as the Indus. Yet in its upper reaches, especially the Gangotri catchment, meltwater dominates. A disruption in its seasonal rhythm could have cascading effects. Irrigation systems in the plains rely on the timing of glacier-fed flows, while hydropower projects at higher altitudes require steady discharge to operate efficiently.

The cultural significance of the Ganga deepens the concern. For millions of Hindus, the river is sacred and central to religious practices. Any alteration in its flow is not only an environmental challenge but also a cultural disruption.

Warning for water management

Scientists warn that the observed changes in runoff seasonality and water volume could severely affect hydropower generation, irrigation and long-term water security. With rising temperatures expected to accelerate glacial retreat in the Himalaya, the changes at Gangotri are seen as a warning signal for broader water management strategies.

“Planning for the future will require acknowledging that climate change is already reshaping our rivers. We cannot rely on past flow patterns to design irrigation or energy projects anymore,” said a senior hydrologist familiar with the study.