A recent study conducted by the Indian Institute of Technology, Indore, ICIMOD and US universities 'Hydrological contributions of snow and glacier melt from the Gangotri glacier system and their climatic controls since 1980', revealed that the Gangotri Glacier, the Himalayan Glacier that feeds the Ganga River, has lost 10 per cent of its snow melt flow due to climate change.
Gangotri's annual discharge was estimated at 28 metre cube/ second (TOS: 28 ± 1.9 m3/s) with snowmelt being the major contributor at 64 per cent, followed by glacier melt at 21 per cent, rainfall runoff at 11 per cent and Base flow at 4 per cent over the decades 1980-2020.
However, the snowmelt’s relative share has reduced from 73 per cent in 1980-90 to 63 per cent during 2010-20. Interestingly, the snow melt flow proportion that reduced to 52 per cent during the 2000-2010 decade, increased to 63 per cent in the following decade.
Researchers explained that the reason for the increase in the snow melt flow proportion is caused by reduced winter temperature (-2 degrees Celsius) 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 temperatures. This is clearly a signature impact of climate change,’ experts told Down To Earth.
The report further said that ‘since the 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.’
The report concludes that the mean annual temperature is rising while the area covered by snow is decreasing. This means that the amount of snow that melts on the Gangotri glacial system (GGS) has been decreasing between 1980 and 2020.
On the other hand, there have been growing trends in base flow and rainfall-runoff, which suggest that warming has caused hydrological changes. This clearly links climate change with the Gangotri Glacial Melt.