Cryosphere crisis: glaciers, water scarcity, and a race to adapt in the Himalaya

Spanning 12 States, one Union Territory, and stretching for more than 2,500 km from Jammu and Kashmir in the north to Arunachal Pradesh in the east, the Indian Himalayan Region is home to numerous peaks, over 22,000 glaciers, and more than 77 million people. This environmentally fragile region is not only highly diverse and rich in biodiversity, supporting millions of livelihoods: it is also one of the regions most vulnerable to climate change.

Often called the ‘Third Pole’ for holding the largest ice and snow reserves in the world after the polar regions and as the ‘Water Towers’ of Asia for being the source of 10 of the continent’s largest rivers, the Himalayas are a crucial lifeline for the 1.3 billion people residing in Asia, primarily as a freshwater source and for their influence on the region’s climate.

However, the Himalayas have been at the forefront of experiencing the consequences of rapid climate change and undergoing drastic, and largely irreversible, transformation thanks to global warming. The mountain communities residing in the Himalayan region are exposed to a variety of climate-induced changes and disasters that are poised to significantly alter the social, economic, and traditional aspects of their society if they are left unaddressed.

Greenhouse gases and aerosols

One of the most discernible ways in which climate change is reshaping the Third Pole is in the elevated levels of warming being observed in high-altitude regions and the associated changes in the cryosphere.

According to a 2023 report titled ‘Water, ice, society, and ecosystems in the Hindu Kush Himalaya: An outlook’ by the International Centre for Integrated Mountain Development (ICIMOD) in Kathmandu, the Hindu Kush Himalayan region has warmed faster than the global average to nearly 2° C since 1950, with higher elevations (> 4,000 m) experiencing even greater warming of up to 0.34° C per decade and a total warming of at least 2.38° C so far.

In addition to greenhouse gases, black carbon — which is an absorbing aerosol — has emerged as a significant driver of short-term warming, contributing to temperature elevation and accelerating glacier retreat in the Himalayan region by 50%.

“Snow and ice are naturally highly reflective, but when covered with dark particles like black carbon, they absorb more solar radiation, leading to increased melting and further warming,” Parth Mahapatra, air pollution mitigation specialist at ICIMOD, said. “This absorption of heat causes local warming and an increase in surface temperatures, particularly in the high-altitude regions of the Hindu Kush Himalaya. Black carbon has a warming effect up to 1,500-times stronger than carbon dioxide per unit of mass.”

Due to this rise in temperature, Himalayan glaciers, like most other glaciers in the world, are retreating at an unprecedented rate. Studies have shown the world has been losing over 270 billion tonnes of glacier mass every year in the last two decades and that the planet is on track to lose two-thirds of all glaciers by the end of the century.

While glacial meltwater does contribute to global sea level rise, the bigger threat in the Himalayan region remains acute water shortage for the millions that directly depend on glaciers for freshwater supply and cryospheric hazards such as glacial lake outburst floods (GLOFs), landslides, and avalanches.

The Himalayan cryosphere

“Himalayan ‘water towers’ — primarily glaciers and seasonal snow — are a lifeline for Trans-Himalayan regions like Ladakh, which receive extremely low rainfall. Glacial and snowmelt serve as the main sources of freshwater,” Mohd Soheb, a cryosphere researcher at the Department of Geography, Heidelberg University in Germany, whose work focuses on cryospheric change and its impact on hydrology and downstream communities in the mountain catchments of Ladakh and other high-altitude regions, explained.

“These cryospheric sources feed streams and rivers, ensuring water availability for drinking, irrigation, and commercial use, especially in the tourism sector during peak summer demand. They provide crucial water security in this arid landscape. However, with climate change accelerating glacial retreat and altering melt and precipitation patterns, the reliability of this natural water storage is increasingly under threat.”

“As someone from Ladakh and a researcher on glaciers and water resources, I’ve seen firsthand how climate change and growing water scarcity deeply affect local livelihoods in high-altitude Himalayan regions,” he continued. “Glaciers are shrinking, precipitation is becoming erratic, and traditional water management systems are slowly disappearing.”

There has been a noticeable drop in winter snowfall, and the snow that does fall tends to melt quickly or only survives at very high altitudes. As a result, meltwater from both snow and glaciers arrives later in the season, which is too late for the crucial early sowing period. This delay leaves many villages struggling to irrigate their fields in time, threatening crop productivity and food security, according to him.

A snow update report released by ICIMOD in April highlighted an alarming decline in snow persistence across the Himalayan region, recording a new low of 23.3% below average — the lowest since 2003 and signifying potential lower river flows, increased groundwater reliance, and heightened drought risk.

“Snow persistence is the fraction of time snow remains on the ground after snowfall. In the Hindu Kush Himalaya, longer snow persistence is crucial as it plays a key role in feeding major rivers in the region,” Sher Muhammad, a cryosphere specialist at ICIMOD said.

Snowmelt contributes nearly 23% of the total water flow of 12 major river basins that originate in the Hindu Kush Himalaya but varies for individual rivers. For example, it contributes nearly 40% of the Indus’s river flow but only 15% of the Ganga and the Brahmaputra. Similarly, different river basins register different snow persistence levels.

Overall, however, the trend has been worrying: 13 of the past 22 years registered lower than normal seasonal snow persistence across the region. Between November 2023 and April 2024, all three major river basins in the Indian Himalaya — Indus (-23.3%), Ganga (-17%), and Brahmaputra (-14.6%) — recorded below normal snow persistence compared to the mean over the preceding two decades.

“Such decreases threaten water availability, especially during early summer when demand peaks, particularly in mountainous regions,” Muhammad said.

A countrywide assessment

While broader regional perspectives and analyses are prevalent, catchment-level analysis allows for a deeper understanding of the intricate interactions between the cryosphere, hydrology, and human activities, according to Soheb.

“Understanding these dynamics enhances scientific understanding and informs policymaking to create more locally relevant adaptation strategies. I believe one of the most promising solutions is the revival and modernisation of traditional water management systems, which are both low-cost and locally adapted,” he added.

Experts have suggested that integrated, climate-resilient water management strategies, which are also flexible and responsive to seasonal changes in water availability, are required to deal with the changing patterns of reduced snowfall and water availability in high-altitude regions. This includes climate-smart agriculture and enhancing local water storage capacity by reviving and adapting traditional water systems that have served the region for centuries. Improvements in irrigation efficiency and investments in groundwater recharge systems are also essential.

In addition to the reduction or alteration of freshwater availability in various parts of the Himalayan region, fast-moving, sudden-onset events like GLOFs and cascading hazards are becoming more common. While studies have not found a noticeable increase in the frequency of GLOFs in relation to temperature rise yet, the probability of GLOF occurrences is projected to increase as more glacial lakes form and expand rapidly in response to rising temperatures and retreating glaciers.

According to one of the first countrywide assessments of GLOF danger in the Indian Himalaya, in 2021, researchers identified and analysed 4,418 glacial lakes in all the Himalayan states and 636 transboundary lakes to understand the potential consequences for human populations and infrastructure. The study revealed that Jammu and Kashmir had the highest overall GLOF danger level, with 13 highest priority lakes needing urgent monitoring and local site investigations.

However, some of the most catastrophic lake outburst floods in recent times have happened in Uttarakhand (Kedarnath in 2013) and Sikkim (South Lhonak in 2023), highlighting the difficulty of accurately predicting GLOF events and assigning risk.

“Like earthquakes, where we do not know when it is going to happen, we can hardly predict which lake is going to burst when. Similarly, in the case of a GLOF, the warning times are also very low because there is a lot of energy, and water is crashing down at tremendous speed,” said Ashim Sattar, assistant professor at the School of Earth, Ocean and Climate Science at IIT Bhubaneswar, whose research focuses on glacial modelling and GLOFs in the Himalaya. “They can have an impact within seconds, minutes, and hours in the downstream valley. So we have very little evacuation and response time before the GLOF hits a particular exposed location.”

The right time

According to Sattar, it is quite possible to assess the potential hazard of any particular lake “by bringing together climate models, ice thickness models, and hydrodynamic models. But when it comes to risk, it becomes tricky. Hazard is just a danger that can be quantified. When we talk about risks, we have to look into the vulnerability and the exposure.”

Risk depends on multiple factors, including the demography of the particular region, how the population is going to evolve, physical and social vulnerabilities, infrastructure, settlement and construction patterns, resilience, and the facilities that are available for recovery. Bringing together all of these various datasets to come up with simplified risk maps would be useful in preparing for future GLOF events, according to him.

“This data is available right now and can be used to quantify risk, but such risk calculations are not being done very widely in the Himalayas [at present].”

Indeed, GLOFs are one of the most unpredictable yet catastrophic disasters and they can exact a very high toll in terms of human casualties and damage to physical infrastructure in the Himalayan region.

In similar vein, cascading hazard events like the Chamoli disaster in 2021 also pose a high risk in the region as the fragile landscape is very susceptible to permafrost degradation, frequent landslides, avalanches, and extreme rainfall events that can compound existing vulnerabilities and significantly amplify the scale of a disaster.

According to Sattar, it is essential to build the resilience of mountain communities to cryospheric hazards in the high mountains by spreading awareness among communities about extant glacier-related hazards and their potential impact, and implementing early warning systems in the mountain valleys exposed to these hazards, particularly towards GLOF risk reduction.

To drive more attention to the rapidly deteriorating state of the cryosphere and glaciers worldwide and their critical function in supporting ecosystems and livelihoods, the United Nations declared 2025 to be the International Year of Glaciers’ Preservation and the period from 2025 to 2034 the Decade of Action for Cryospheric Sciences. The declaration comes at a critical juncture: fast-rising global temperatures are projected to top the pre-industrial average by as much as 3° C by the end of this century, in a place where the world’s frozen reserves are already being rapidly destabilised, affecting billions of people worldwide.

With nearly 77 million living in the Himalayan region in the country, it is the right time for India to take cognisance of this growing threat and develop a comprehensive action plan to adapt to rapid changes in the cryosphere and glaciers in the coming decade.

Neelima Vallangi is an independent journalist and filmmaker covering climate change in the Himalayan region and South Asia.