Melting glaciers have significant impact on water resources of Himalayan rivers due to a change in glacier basin hydrology, reduced water downstream, and impact hydropower plants due to variation in discharge besides causing flash floods and sedimentation.
Monitoring, collection of data and scientific studies of the Himalayan glaciers by various Indian institutes, universities and organisations working on glacial changes have reported an accelerated heterogeneous mass loss in Himalayan glaciers, the minister of state of the ministry of earth sciences and science and technology, Dr. Jitendra Singh informed the Lok Sabha on Wednesday.
He said that the government is aware of the melting of the Himalayan glaciers and is maintaining data on the subject. The data and the studies come from the Geological Survey of India, the Wadia Institute of Himalayan Geology, the National Centre for Polar and Ocean Research (NCPOR), National Institute of Hydrology, Space Application Centre and the Indian Institute of Science, besides others.
The mean retreat rate of Hindu Kush Himalayan glaciers is 14.9 ± 15.1 meters per annum, which varies 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 the in Brahmaputra river basins. However, glaciers in the Karakoram region have shown comparatively minor length change (-1.37 ± 22.8 metres per annum), indicating their stable condition.
The minister said that the government is aware of the study conducted by the University of Leeds, regarding the rapid melting of Himalayan glaciers, published in Journal Nature Scientific Reports in 2021. Researchers carrying out the study reconstructed the size and ice surfaces of 14,798 Himalayan glaciers during the Little Ice Age, 400 to 700 years ago.
The Leeds researchers concluded that the Himalayan glaciers have lost ice ten times more quickly over the last few decades than on average since the last major glacier expansion. In the last 400 to 700 years, the glaciers have lost around 40 per cent area – shrinking from 28,000 square kilometres to around 19,600 square kilometres.
Through its autonomous institute NCPOR, the ministry of earth sciences has been monitoring six glaciers in the Chandra basin since 2013. The Chandra basin covers an area of 2437 square kilometres in the western Himalayas. It has been observed that the rate of annual mass balance (or simply, melting) ranged from -0.3±0.06 metres water equivalent per year to -1.13±0.22 meters water equivalent per year between 2013-2020. Similarly, a mean thinning of approximately 50±11 metres with a mean annual mass loss of –1.09± 0.32 meters water equivalent per year was observed for the Baspa basin during 2000-2011.
Impact on Himalayan rivers
Similarly, GSI has taken up a project on monitoring and studying melting of glaciers in Beas Basin, South Chenab basin and Chandra Basin in Himachal Pradesh, Shyok and Nubra basin in Ladakh during Field Season 2021-22.
The Department of Science and Technology has supported various research projects for studying Himalayan glaciers under the national mission for sustaining Himalayan ecosystem and national mission on strategic knowledge for climate change. The mass balance studies conducted for some Himalayan glaciers by Universities of Kashmir, Sikkim University and the Indian Institute of Science and the Wadia Institute of Himalayan Geology revealed that majority of Himalayan glaciers are melting or retreating at varying rates.
The Wadia Institute of Himalayan Geology (WIHG) is monitoring a few glaciers in Uttarakhand as well. This has revealed that the Dokriani glacier in the Bhagirathi basin is retreating at 15-20 metres every year since 1995, whereas the Chorabari glacier in the Mandakini basin region is retreating anywhere between 9 and 11 metres yearly between 2003 and 2017. The WIHG is also monitoring Durung-Drung and Pensilungpa glaciers in Ladakh’s Suru basin. The findings from these monitoring say that the glaciers are retreating at the rate of 12 metres every year and at approximately 5.6 metres yearly, respectively.
NIH has been conducting several studies for the assessment of runoff from melting of glaciers at catchment and basin scales across Himalaya.
Melting glaciers have significant impact on water resources of Himalayan rivers due to change in glacier basin hydrology, downstream water budget, impact on hydropower plants due to variation in discharge, flash flood and sedimentation. The melting of glaciers also increases the risks related to glacier hazards due to enhanced number and volume of glacier lakes, accelerated flash flood and glacial lake outburst floods (GLOFs). It also impacted on agronomic practices in high Himalayan region.
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