जुलाई 02, 2020
ICMIOD scientist Arun Shrestha presented his findings on the concluding day of the India Word Water Forum this week
Himalayan glaciers contribute only a small part of the water carried down by rivers from the world’s tallest mountain range. But this small part can be crucial in the months when it does not rain, especially during the spring snow melt and especially for people living just a little below the headwaters.
It is now well established that glaciers around the world – and especially in the Hindu Kush Himalayas – are retreating due to global warming. However, there are huge data gaps on the extent of the retreat and the effect this will have on the rivers coming down from these mountains known as the water tower of Asia.
Arun Shrestha, a scientist at the Kathmandu-based International Centre for Integrated Mountain Development (ICIMOD), has been studying the effect of glacier retreat in five major river basins in the Himalayas – Indus, Ganga, Brahmaputra, Salween and Mekong. Presenting his findings on the concluding day of the Second India Water Forum in New Delhi on Wednesday, Shrestha said the models showed significant reduction in water flow in the upper reaches of the Sutlej and Kabul rivers throughout this century as a result of glacier retreat. Both rivers are in the Indus basin.
On the other hand, the models showed an increase in water flow in the upper reaches of two important rivers of the Ganga basin – Dudh Kosi and Tama Kosi.
Overall, the ICIMOD study predicted that Himalayan water flow from the glaciers to the basins would reduce by 25-50% by the end of this century, with the reduction getting worse as one travelled from west to east. But at the same time, the western rivers were the ones more dependent on water from glacier melt, while the eastern rivers got more rain. Shrestha said the effects would even out by the time these rivers reached their deltas, but there would be a significant effect on the upper reaches, and therefore on the people who live in the Himalayas and are dependent on this water.
Countries refuse to share data
The scientist rued the fact that ICIMOD – a research organisation of the United Nations which has Afghanistan, Pakistan, India, China, Nepal, Bhutan, Bangladesh and Myanmar as its members – had received water flow data for the study from only Nepal and Pakistan. An obvious consequence was that the results were less accurate than they could have been. “The data is existing but not accessible,” Shrestha said. “We want better data sharing.”
He also said there was “very urgent need to improve precipitation measurements in high altitudes.” The lack of high altitude weather stations in the Hindu Kush Himalayas has long frustrated scientists and policymakers.
Speaking at the same session – which was on water vulnerability due to climate change – Eddy Moors from the Wageningen Institute in The Netherlands predicted that as a result of global warming, there would be “more extreme precipitation (rainfall and snowfall) events” in the Ganga basin, and this would become notable between 2081 and 2100.
Snow and ice melt contributes only between one and five per cent of the water in the Ganga and its tributaries, Moors said. But the hydrologist, who has been studying the Ganga basin, pointed out that this was an annual average, and the percentage became higher in the months of March, April and May, before the monsoon reached the Himalayas.
Some scientists have predicted by the end of the century, rice production in the Ganga basin would be down 20-40% as a result of climate change and consequent water shortage. “Water demand management is essential,” Moors told the policymakers gathered at the forum.
The 2013 forum was held around the theme of water use efficiency and was inaugurated by the President of India Pranab Mukherjee. It was organised by The Energy and Resources Institute with support from the Ministry of Urban Development, Ministry of Drinking Water and Sanitation and the Water and Sanitation Program of the World Bank.