Since 1993, the United Nations has observe World Water Day (WWD) on 22 March annually for raising awareness of 2.2 billion people living without access to safe water, and taking action to tackle global water crises, having a core focus to support achievement of SDG 6, the goal on water and sanitation for all by 2030. Preserving glaciers is the 2025 theme of WWD which coincides with the International Glacial Year (2025) for raising awareness about the critical role of glaciers, snow and ice in the climate systems, the hydrological cycle, and in the Earth’s cryosphere (e.g. the state of the Earth’s ice and snow affecting every living being). Glaciers are critical for human life; the melt water is used for drinking, and is essential for agriculture, industry, clean energy production and ecosystems.
If glaciers melt rapidly, it causes uncertainty in water flows impacting people and our planet. Global reductions of carbon emissions and local strategies are required to adapt to shrinking glaciers. The melting of glaciers affects every area: people having in coastal areas are affected by sea level rise; people living in high mountainous areas are more prone to the risk of flooding, landslides and avalanches, and people living in downstream areas are dependent on water supply from glaciers. Glacier loss also contributes to loss of biodiversity, particularly the endemic species as well as loss of traditional ways of life. Glaciers act as long-term reservoirs of pollutants like heavy metals, black carbon, and persistent organic pollutants (POPs) into the atmosphere.
These pollutants settle on to glacier surfaces through precipitation or dust and the meltwater carries contaminants to freshwater systems adversely impacting drinking water sources and aquatic life. Various studies show that in 2023, glaciers over the world lost more than 600 gigatons of water, the largest mass loss registered in 50 years. The rate of melting varies across regions, influenced by local climatic conditions and topographical factors. About 70 per cent of the Earth’s fresh water exists as snow or ice; nearly 2 billion people rely on water from glaciers, snowmelt and mountain runoff for drinking, agriculture and energy production; increased glacier melting is responsible significantly for global sea-level rise with today’s sea level about 20 cm higher than in 1900; and limiting global warming to 1.5°C could save glaciers in World Heritage Sites (IPCC, WMO, UNESCO).
The Hindu Kush Himalaya (HKH) region has the largest concentration of snow and glaciers outside the polar region, commonly referred to as the ‘Third Pole” of the world. The HKH has the western boundary of Afghanistan and the eastern boundary of Myanmar, and is a source of 10 major rivers including the Indus, Ganga and Brahmaputra. The Indian Himalayan Region, part of the larger HKH system, spans across 13 Indian states and UTs with approximately 50 million people residing in the region. There are about 9,575 glaciers in the Indian Himalayas over three river basins: Indus, Ganga and Brahmaputra. However, about 90 per cent of glaciers are small in size; being smaller than 5 sq km in area and many even smaller than 1 sq km in area.
A few glaciers such as Siachin, Gangotri and Zemu are bigger than 10 sq km in area (TERI 2019). Himalayan glaciers, located very close to tropics at low altitude, are naturally vulnerable due to their geographical setting. These glaciers are located in highly inhabited districts of the Himalayas and thus the local pollution has an impact on the overall melt response of glaciers. Glaciers in Himalayas (India) have been exhibiting continuous retreat: East Ranthong glacier (15.1 meter/year), Gangotri glacier (19.9±0.3 meter/year), Samudratapu glacier (15.1 meter/year), Gangotri glacier (18.45 meter/year) and Dokriani glacier (16.6 me – ter/year).
The retreat in the Hindu Kush Himalayan Glaciers is (14.9 ± 15.1 meter / annum) overall, which varies from 12.7±13.2 meter/annum in Indus, 15.5±14.4 meter/ annum in Ganga, and 20.2 ±19.7 meter/ annum in Brahmaputra river basins, respectively. In fact, both the number of retreating glaciers and extent of retreat are reported to be the highest for western Himalayan glaciers, while it is less in the eastern Himalayan basin (TERI 2019 and MoES 2023). The continuous retreat of glaciers could lead to the formation and expansion of glacial lakes, posing serious risks to downstream communities and infrastructure through glacial lake outburst floods (GLOFs).
Glacier melting is influenced by climatic factors (temperature, rainfall, snowfall) and non-climatic factors such as the location. About 800 million people living in the Indus, Ganga and Brahmaputra river basins are dependent on Himalayan glaciers. These provide water during the lean summer season when precipitation is less and demand is high. The Indus, the Ganga and the Brahma putra together provide close to 50 per cent of India’s utilizable surface water resources. Contribution from snow and ice melt to the total annual river discharge is about 60, 9 and 21 per cent for Indus, Ganga and Brahmaputra basins respectively.
For Brah m aputra and Ganga River basins, the contribution from rainfall is significant but rainfall is limited to 30-40 days during monsoon seasons, and contribution from snow and glacier melt is likely to be high in these rivers. The melting of glaciers is a natural process. The recession or melting of glaciers is mainly caused by global warming and climate change. This rate of melting of glaciers cannot be prevented unless all factors responsible for global warming and climate change are controlled. There is high interdependence between glaciers located in the Himalayas and the energy security of India; 33 per cent of India’s thermal capacity and 52 per cent of hydropower are dependent on water from rivers originating from the Himalayas.
Flash floods in Parichu river and rivers in Uttarakhand provide conclusive evidence of increasing vulnerability of dam projects in Himalayas. There is a need to integrate glacier preservation considerations in the national and regional climate strategies, water management policies, and disaster risk-reduction plans and forge partnerships with international organisations, the private sector, academics and NGOs for leveraging expertise, resources and funding for glacier preservation initiatives. Second, there is a need to establish an integrated national cryosphere information system as a long term mechanism, and also for integrating the same with global information systems in the cryosphere for developing standard approaches to monitor cryospheric changes. Advance research in cryosphere monitoring is a must.
Third, regular reporting on changes of glaciers and snow, at scales relevant to needs, should be formalized and included in local, national, regional and global reporting systems. Fourth, there is a need to assess short, medium and long term water availability for all mountain basins and under current and future deglaciated conditions and climate. Fifth, there is a need to raise awareness at all levels about the importance of glacier change on downstream communities, and ecosystems. Urgent action is needed to adopt adaptation strategies. Sixth, hydropower projects should make a comprehensive assessment of impacts due to climate and vulnerability to water sources. Integrated river basin management to rejuvenate water potential is a must.
A comprehensive assessment of glacier lakes occurring up-stream of a hydropower project, and taking mitigatory measures to reduce their GLOF potential should be made. Seventh, a national GLOF risk management framework should be established, integrating scientific research, disaster management policies, and climate adaptation strategies. Collaboration with neighboring countries like Nepal and Bhutan, which share Himalayan watersheds, can enhance cross-border early warning mechanisms and resource-sharing for disaster management. Preventing GLOF events in India requires a combination of advanced technology, engineering solutions, community resilience, and climate action. By integrating these strategies, India can mitigate the impacts of GLOFs and protect both its people and the fragile Himalayan ecosystem.
(The writers are, respectively, Distinguished Fellow, TERI, New Delhi and a former Secretary, Ministry of Water Resources, Govt. of India., and Managing Director of Mu Gamma Consultants, Gurgaon S)