A study by IIT Indore and international collaborators reveals that the Gangotri Glacier has lost 10% of its snowmelt flow over four decades due to climate change.
The research highlights a shift in the glacier's flow composition, with snowmelt decreasing and rainfall-runoff increasing, posing significant implications for water resources in the region.
A recently published study report by the Indian Institute of Technology (IIT) Indore scientists in collaboration with others has found a tell-tale effect of climate change on the Gangotri Glacier System (GGS), the central Himalaya glacier that feeds the Ganga river.
The study used both satellite and actual data from the last four decades (1980-2020). It found through a modelling exercise that the snow melted water has reduced overall over the decades as the surge in temperature, catered by climate change, is allowing less formation of snow in one of the most iconic glaciers of the world.
The paper, Hydrological contributions of snow and glacier melt from the Gangotri glacier system and their climatic controls since 1980, has been published recently in the Journal of the Indian Society of Remote Sensing. It is authored by hydrology experts from IIT Indore alongside scientists from four United States based universities and International Centre for Integrated Mountain Development (ICIMOD), Nepal.
“Over the last four decades, the composition of flow from the GGS is changing due to climate change, and this study offers the most detailed picture yet of how those changes have unfolded over the past four decades,” pointed out the lead author Parul Vinze, a doctoral scholar at Glaci-Hydro-Climate Lab, IIT Indore to this correspondent on August 26.
The report shows that snowmelt still dominates the flow pattern, supplying 64 per cent of annual flow over the last four decades. It is followed by glacier melt (21 per cent), rainfall-runoff (11 per cent), and base flow (4 per cent). However, snowmelt’s relative share is sliding, from 73 per cent in 1980-90 to 63 per cent during 2010-20.
Interestingly, an apparent turnout could be seen in the statistics during 2010-20, as the snow melt proportion, which was reduced to 52 per cent during 2000-10, increased to 63 per cent during the next decade. Consequently, the rainfall contribution, which was consistently increasing from 1991 to 2000, got reduced.
The researchers explained that the “…The sudden increase in QS (snowmelt flow proportion) … in 2011-2020 is mainly caused by reduced winter temperature (−2°C) and increased winter precipitation (262 mm), leading to high snow accumulation in winter which subsequently melts in summer as temperature increases …”.
“The data analysis shows that while snowmelt continues to dominate the overall Gangotri glacier flow, its share has reduced over the decades as less snow falls in the region due to gradually increasing temperature. This is clearly a signature impact of climate change,” explained Mohammed Farooq Aza, attached to both IIT Indore and ICIMOD, supervisor of the study, to this correspondent recently.
The study also explained that there has been an “increase of 0.5°C in the mean temperature over 2001-2020 as compared to 1980-2000 in GGS”, triggering earlier summer melting and, hence, peak discharge.
“… Since 1990s, peak discharge has shifted from August to July, driven by reduced winter precipitation and earlier summer melting; a trend that can have severe implications for hydropower generation, irrigation, and water security at higher elevations,” reads the report, a copy of which is with this correspondent.
The report, in conclusion, further explains that “…Long-term trend analysis indicates an increasing trend in mean annual temperature with a decreasing trend in snow cover area, resulting in a decreasing trend of snowmelt on GGS (Gangotri glacial system) over 1980-2020. Conversely, rainfall-runoff and base flow have exhibited increasing trends … suggesting warming induced hydrological changes”, directly linking climate change with Gangotri trend.
“The decadal analysis showed that the maximum decadal discharge (28.9 m3/s) was observed in 2001-2010 corresponds to the highest decadal temperature (3.4°C) over four decades (1980-2020) in GGS. The decadal mean discharge showed the highest volumetric increase of 7.8 per cent from 1991-2000 to 2001-2010 on GGS,” states the report, highlighting the enhanced role of climate change.
“The finding vindicates other assessments. The studies show that Himalayan glaciers, on an average, are losing their thickness at a rate of 46 cm annually. I have been tracking Gangotri for about three decades and observed that the snout of the glacier system has been steadily receding,” said Kalyan Rudra, a river expert and chairman of the West Bengal Pollution Control Board.
“The Gangotri glacier, a significant water resource for northern India, is experiencing significant changes due to climate change. Through this study, we … observed the volumetric change is a declining pattern of the study period 2017 to 2023 gradually. The climatic parameters observed an increasing trend over the last two decades,” pointed another scientific paper, Understanding the Gangotri glacier dynamics: Implications from a fully distributed inversion of equivalent water-volume change, published in journal The Cryosphere for discussion in May 2025 by a set of scientists from several IITs and Indian Institute of Science, Bhopal.
“The trend is being found in many places. I have observed a similar melting trend even in Ladakh,” shared Abhijit Mukherjee, a groundwater scientist from IIT Kharagpur.