Rivers in the Eastern Himalayas get less water from glacial melt; Still, the perennial nature of several rivers could be lost, say experts
Rivers in eastern and northeastern India including the Brahmaputra, Ganga and Teesta will, like their counterparts in the rest of the Hindu Kush Himalayas (HKH), see a rapid increase in stream flow followed by water scarcity, a new report released by the International Centre for Integrated Mountain Development (ICIMOD) on June 20, 2023, warned.
The report — Water, ice, society, and ecosystems in the Hindu Kush Himalaya — pointed out that glaciers in the HKH region “can lose up to 80 per cent of their current volume by the end of the century (with) Himalayan glaciers disappeared 65 percent faster in the 2010s than in previous decade”.
As a consequence, major rivers in the Himalayas including those in eastern and northeastern India are set to suffer.
The report also observes that “floods and landslides are projected to increase over the coming decades” and warns that the effects on fragile mountain habitats may turn out to be “particularly acute”.
“The Eastern Himalayas will be affected as well (like the western part of the range), with rivers like Brahmaputra and Teesta getting their base flow from glacial melt reduced in the long-run,” observed Anjal Prakash, a climate expert and professor in Indian School of Business (ISB), Hyderabad.
United Nations Secretary-General Antonio Guterres earlier pointed out that the flow in major Himalayan rivers including the Indus, Ganges, and Brahmaputra, all critical for India, may get significantly reduced as glaciers and ice sheets are expected to recede in the future due to global warming.
“As glaciers and ice sheets continue to recede over the coming decades, major Himalayan rivers like the Indus, the Ganges, and Brahmaputra will feel the impact … seeing their flows reduced,” said Guterres.
Last year, the Union Ministry of Earth Sciences also informed the Lok Sabha that glaciers feeding the Ganga and the Brahmaputra river basins were melting at a fast rate.
According to the ministry report, the mean retreat rate of the Hindu Kush Himalayan glaciers was 14.9-15.1 metres per annum, which varied from 12.7-13.2 metres per annum in the Indus, 15.5-14.4 metres per annum in the Ganga and 20.2-19.7 metres per annum in the Brahmaputra river basins.
“The Eastern Ganga Region (ERG) with its development deficit context and low capacity is already becoming a crucible of hazards: Erratic and extreme rainfall, extreme floods and landslides, droughts, low flows, and scorching wet bulb heat. ICIMOD’s 2019 HKH assessment presented a concerning scenario of snow and ice decline. Its new report presents an even more concerning scenario ... The institutions are just not prepared to address the emerging risks and existing water treaties with arrangements for sharing the waters of the snow-fed rivers, for example, do not recognise climate change threats,” observed Ajay Dixit, a senior water expert from Nepal.
Kalyan Rudra, water expert and West Bengal Pollution Control Board chairman, said the Eastern Himalayas, also called lesser Himalayas, have less glaciers compared to their western counterparts.
Hence, rivers in the region get less contribution from such glaciers; and are less likely to be affected overall.
“Still, climate change can impact rivers if the snow and glacial meltwater get reduced in the region during March, which is the dominant contribution during that time ... the perennial nature of several rivers may be lost,” added Rudra,
Nilanjan Ghosh, river expert and director of think tank ORF Kolkata also opined that tributaries play a major role in augmenting the flow of rivers in the region; and hence glacial melting impacts would be less compared to the western part of Himalayas.
“We expect an immediate increase in water flow in major rivers due to melting; followed by long term water scarcity,” added Ghosh.
The HKH region, harbours the highest mountain ranges in the world. It also contains the largest volume of ice on earth outside of the polar areas and is called “Asia’s water tower”.
The region is undergoing “unprecedented and largely irreversible” changes triggered by global warming, the ICIMOD report said.
It added that “ice and snow in the Hindu Kush Himalaya are an important source of water for 12 rivers that flow through 16 countries in Asia, providing freshwater and other vital ecosystem services to 240 million people in the mountains and a further 1.65 billion downstream”.
“This report is important but the time has come to go beyond generalised reports and become specific. For example, it would have been great if the report could have told which areas of Himalayas are expected to be affected how much, so that specific combative strategies can be formulated,” expressed a senior water expert of South Asia.
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