Climate Change Is Reshaping Gangotri’s Meltwater

In the central Himalaya, the Gangotri Glacier System (GGS) — the source of the River Ganga — is undergoing profound changes as climate change alters its meltwater dynamics. A new study has modelled four decades of Gangotri’s streamflow, providing the most detailed picture yet of how snow, ice, rainfall, and groundwater contributions are shifting.

The Hindu Kush Himalaya (HKH) region holds vast snow and ice reserves that feed major rivers like the Indus, Ganga, and Brahmaputra, sustaining millions downstream. But rising temperatures are accelerating glacier retreat and shifting the timing and composition of meltwater flows, with serious implications for water security, agriculture, and hydropower.

Using the high-resolution Spatial Processes in Hydrology (SPHY) model — calibrated with discharge records, satellite-derived glacier mass balance data, and snow cover maps — researchers from IIT Indore analysed Gangotri’s streamflow between 1980 and 2020.

The results show snowmelt contributes 64% of annual flow, followed by glacier melt (21%), rainfall-runoff (11%), and baseflow (4%). Lead author Parul Vinze, a PhD scholar at the Glaci-Hydro-Climate Lab, IIT Indore, notes that the seasonal discharge peak has shifted from August to July since the 1990s, driven by reduced winter precipitation and earlier summer melting.

“Though Gangotri’s flow is snowmelt-dominated, snowmelt has gradually declined over time, while rainfall-runoff and baseflow have increased,” she said. “This subtle reshaping of the hydrological balance highlights the long-term influence of climate change.”

Earlier studies of Gangotri’s meltwater were constrained by shorter datasets and lower-resolution climate models. By contrast, this 41-year analysis provides clearer estimates of the relative contributions of different water sources, improving confidence in forecasts of future availability.

“Accurate modelling, backed by field data, is critical for predicting water supply in the Himalaya,” said Dr. Mohd. Farooq Azam, supervisor of the study, Senior Intervention Manager – Cryosphere at ICIMOD, and Associate Professor at IIT Indore. He stressed the need for sustained field monitoring and the integration of high-resolution climate projections to refine forecasts.

At a basin-wide scale, the Ganga relies less on meltwater than the Indus. But at higher elevations like the Gangotri Catchment, runoff is dominated by snow and glacier melt. The observed shifts in seasonality and runoff volume could severely affect irrigation and hydropower generation in mountain regions, Dr. Azam warned.

The writer of this article is Dr. Seema Javed, an environmentalist & a communications professional in the field of climate and energy