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Glacial Lake Outburst Floods (GLOFs) in Nepal are becoming a significant hazard in the Himalayas, driven by climate change and an increasing number of glacial lakes. Nepal's GLOF history is marked by several catastrophic events that have caused widespread devastation. The earliest recorded GLOF occurred about 450 years ago in Seti Khola but its details are not available.  A recent article by Byers, Chand, and their team also reconstructed the GLOF history in the Kanchenjunga region, where they found the occurrence of GLOF since 1921. They found at least seven GLOF events in that region with the help of remote sensing and field observation, which were not recorded before. Besides, ICIMOD has compiled 24 events out of which 14 occurred in Nepal and 10 in Tibet (China), causing extensive damage in Nepal. A notable GLOF event occurred in 1985 when Dig Tsho burst, leading to a destructive flood that destroyed infrastructure, including a hydropower plant under construction. Another study by Shrestha and her team recorded 54 events in Nepal. These datasets also indicated that several events occurred and are occurring in remote mountains that were not noticed due to their impact being insignificant and remote in nature. The Thame GLOF that occurred in Aug 16 this year is another noticeable event that caused damage to Thame village and the downstream ecosystem despite the small size of the breached glacial lake.

The underlying causes of GLOFs are tied to the unique geographical and climatic conditions of Nepal. The Himalayas are home to thousands of glaciers, which have formed numerous glacial lakes, particularly in the high-altitude regions. These lakes are formed when glaciers retreat, leaving behind large volumes of water contained by unstable moraines. As global temperatures rise, the rate of glacial melting increases, leading to the expansion of these lakes. The moraines that contain them are often weak and prone to collapse, especially under the pressure of additional water, seismic activity or other triggering factors like avalanches or landslides.

GLOFs have severe impacts on both the natural environment and human settlements. The floods can destroy agricultural land and hydropower, disrupt transportation networks and lead to loss of life and property. In addition to physical destruction, GLOFs also contribute to long-term environmental changes, such as the alteration of river courses and the degradation of ecosystems. The socio-economic impacts are profound, particularly in rural and remote areas where communities rely heavily on agriculture and where infrastructure is limited.

Over the decades, Nepal has tried to monitor and mitigate the risks associated with GLOFs. The establishment of early warning systems, such as the one implemented at Tsho Rolpa back in the 1990s, one of Nepal's largest glacial lakes located in Dolakha district in the Tamakoshi river basin, is a critical step in disaster risk reduction. Initially, an experimental siphon system was installed in 1995 to release the water and lower the lake volume, but it stopped working after 15 months. In 1997, the then government installed additional siphones and an early warning system. An automatic early warning system was installed in 1998 with a GLOF sensing system and a GLOF warning system along the Rolwaling and Tamakoshi river valleys. Engineering interventions, such as the lowering of lake levels by three meters through controlled drainage, have also been employed to reduce the risk of outbursts through the GLOF risk reduction project, with funding from the World Bank, the Netherlands International Development Agency and the government of Nepal. However, a lack of continuous funding, research and proper coordination among agencies, along with the period of Maoist insurgency, hindered the progress of mitigation work. Again, in 2015, the Early Warning System was revitalized with the installation of hydrological, precipitation and automatic weather stations at different locations in the downstream region.

The community-based Flood and Glacial Lake Outburst Risk Reduction Project, also known as the Imja Glacier Lowering Project in the Dudhkoshi basin, was implemented between 2013 and 2017 to mitigate the risks of glacial lake outburst floods (GLOFs) and to reduce human and material losses in Solukhumbu district and catastrophic flooding events in the Tarai and Churia range. The project was implemented by the Department of Hydrology and Meteorology (DHM) in partnership with different stakeholders and funded by Global Environment Facility-Least Developed Countries Fund (GEF-LDCF), UNDP. Imja was considered one of the most potentially dangerous glacial lakes for GLOF, which is rapidly increasing in size and volume due to glacial melt and the action of lake water that continuously triggers the calving of the glacier. Key activities of the project included the establishment of early warning systems, community training for disaster preparedness and the construction of protective infrastructure. The project also emphasized community participation, ensuring that local knowledge and needs shaped the initiatives. Through these efforts, the project successfully improved local capacities to respond to flood risks, ultimately contributing to enhanced safety and security for affected populations. By excavating a channel through the moraine that holds back the lake, the project successfully lowered the water level by 3.6 m, thereby enhancing drainage capacity and reducing the risk of catastrophic flooding downstream. This intervention significantly improved safety for local communities, alleviating fears and allowing residents to pursue their livelihoods with greater security. Additionally, the project facilitated environmental monitoring of glacial dynamics, contributing to a better understanding of the ongoing changes in the region due to climate change. It also promoted awareness of GLOF risks and enhanced community capacity for disaster preparedness through training programs focused on emergency response. Furthermore, the project emphasized the importance of sustainable practices, reinforcing the need for ongoing research and actions to manage the impacts of climate change on Nepal’s glaciers. Overall, the Imja Glacier Lowering Project stands as a proactive model for disaster risk reduction, highlighting the critical integration of scientific research, community engagement, and sustainable environmental management in safeguarding vulnerable populations in the Himalayas.

Additionally, the government, in collaboration with different organizations, has undertaken research and mapping projects to identify high-risk lakes and develop preparedness strategies. The government has identified four additional glacial lakes—Thulagi in Gandaki basin and Lower Barun, Lumding and Hongu in the Koshi basin—to implement the structural intervention along with the early warning system and capacity-building. The government has proposed about $36.1m to the Green Climate Fund and the initiative is expected to start in 1-2 years.

Despite these efforts, challenges remain in effectively managing the risks associated with GLOFs. The remote and inaccessible nature of many glacial lakes makes monitoring difficult, and the unpredictable nature of GLOFs complicates forecasting efforts. Furthermore, the rapid pace of climate change poses a growing threat, as the continued retreat of glaciers is likely to create new glacial lakes and increase the volume of existing ones. As temperatures continue to rise, the frequency and intensity of GLOFs are expected to increase. Not only large-sized glacial lakes but small lakes may also have significant impacts. Thousands of such lakes in the high mountains have significant implications not only for Nepal but also for the downstream countries in the Himalayan region that share river basins with Nepal. Collaborative regional efforts are essential to address these transboundary risks. Updating current inventory, categorization of potentially dangerous glacial lakes, and regular monitoring mechanisms should be established under the government in collaboration with research institutions. 

Cryosphere Call to Action is an open letter for the 28th Conference of Parties (COP28), which is meeting under the UN Framework Convention on Climate Change (UNFCCC) in Dubai. It is a movement to move forward with both urgency and ambition in mitigation of climate change due to the response of various components of the cryosphere, including glaciers, snow, permafrost, ice sheets and sea ice. The message of the cryosphere to global leaders is 2oC too high as global impacts and damage for each tenth of a degree higher, especially for longer periods, will grow well beyond the limits of adaptation.

The Paris Agreement is a legally binding international treaty on climate change with the goal to hold the increase in the global average temperature to well below 2°C above pre-industrial levels and pursue efforts “to limit the temperature increase to 1.5°C above pre-industrial levels. It was adopted by 196 Parties at the UN Climate Change Conference (COP21) in Paris in 2015. However, temperature target of 1.5°C is not just a preference compared to 2°C. Instead, it implies that there is a significant difference between the two, suggesting that aiming for a rise in global temperatures of 1.5°C has distinct advantages and avoiding severe environmental impacts and is more imperative than settling for a limit of 2°C. UN’s Intergovernmental Panel on Climate Change (IPCC) also indicates that crossing the 1.5°C threshold risks unleashing far more severe climate change impacts.

Climate-induced disasters are becoming more frequent and severe, with devastating impacts on people and ecosystems around the world. These disasters include heat waves, droughts, floods, wildfires, storms, glacial lake outburst floods (GLOFs) and sea level rise. Such events are killing thousands of people each year; causing widespread famine and displacement; destroying homes, businesses, and infrastructure. The 2022 flood submerged one-third of Pakistan, killed 1,739 people, affected 33m people, damaged most of the water systems and economic losses to the tune of $15.2bn (approx). Forty-two people died in the recent GLOF in Sikkim—77 people remain unaccounted for—and damaged hydropower projects, disrupting the generation of 1,200 MW. A flash flood in Mustang in 2023 damaged several houses, bridges and affected farmlands. Besides, the number of cryosphere-related hazards is increasing in the Himalayan region with increased warming in the high mountain region.

Message from the community

International Cryosphere Climate Initiative (ICCI), a network of senior policy experts and researchers working with governments and organizations, has released the call for action for Cryosphere for COP28. The summary of the call for action is as follows:

“The irreversible global damage caused by Cryosphere loss is already inevitable to some extent. The message is that this insanity cannot and must not continue. COP28, and December 2023 must be when we correct the course. The Cryosphere, encompassing Earth's ice sheets, sea ice, permafrost, polar oceans, glaciers, and snow, is ground zero for climate change. This is primarily due to the straightforward physical phenomenon of ice melting. The warming effect of CO2, predominantly stemming from fossil fuel usage, has already resulted in significant declines in glaciers and ice sheets, contributing to a rise in global sea levels. This phenomenon has also led to diminished water resources due to reduced snowpack, increased emissions of CO2 and methane resulting from thawing permafrost. It is time to carve a line in the snow: Because of what we have learned about the Cryosphere since the Paris Agreement was signed in 2015, 1.5°C is not merely preferable to 2°C. It is the only option.

The plea at COP28 is for global leaders to acknowledge the stark reality presented by the Cryosphere’s response, asserting that even a 2°C limit is too high. The call is to commit to the Paris Agreement’s “well below 2°C” target, which, in essence, translates to aiming solely for the 1.5°C threshold. If we don’t take decisive action against climate change, the consequences will be severe. Millions of people may be forced to leave their homes due to coastal flooding. We’ll face a shortage of clean water, and the delicate ecosystems in oceans and mountains will be disrupted. This will create long-lasting challenges for future generations. The main issue here is the increasing levels of CO2, reaching unacceptable heights. The scientific community advocates for a comprehensive stocktake with clear guidelines, a pathway to phase out fossil fuels and financial mechanisms to support climate action and adaptation. It’s crucial that we go beyond mere discussion and implement substantial measures to address the far-reaching effects of melting ice. It’s not enough to talk the talk; we must walk the walk.”

Meaning for Nepal

Nepal’s glaciers and snowpack are lifelines for the nation, supplying essential water for drinking, irrigation and hydropower generation. They are acting as a climate regulator and supporting unique ecosystems, including high-altitude forests, alpine meadows and glaciers, contributing to the country’s rich biodiversity. Being rich in cryosphere resources, it is urgent for Nepal to advocate for ambitious and achievable targets of reducing greenhouse gas emissions and limiting global warming to 1.5 degrees Celsius, including negotiating for increased financial support in research and development related to cryosphere science and adaptation measures. The funding is crucial for Nepal to understand the impacts of climate change on the cryosphere and develop effective adaptation measures in the high mountain areas. It also necessitates cooperation with other nations on cryosphere protection to learn from shared experiences and adopt best practices. This collaborative approach enhances the effectiveness of cryosphere conservation efforts. Such an effort will enable Nepal to implement the Cryosphere Call to Action effectively.

In this context, the Cryosphere Call to Action at COP28 UAE is a landmark opportunity for Nepal to raise its voice on this issue and address the imminent challenges posed by climate change.

Nepal’s Himalayas, often referred to as the "Third Pole," play a pivotal role in the world's climate system. These towering mountains are adorned with glaciers, snow, permafrost and an intricate network of rivers, forming a fragile and interconnected cryosphere. The impact of climate change on the Himalayas is profound, with far-reaching consequences affecting the region's water resources, hydropower potential and the livelihoods of its people.

At grave risk

Nepal's glaciers are retreating at an alarming rate, consistent with the global trend. The rapid melting of glaciers poses a significant threat to the country's freshwater supply. As the glaciers diminish, water resources become less predictable and water scarcity issues intensify. A study conducted in the Sagarmatha region showed that the glaciers in the region will decrease 39-52 percent by 2050 relative to present day. A recent assessment report published by the International Centre for Integrated Mountain Development (ICIMOD) and UNDP states that the rate of glacier mass loss in the Hindu Kush Himalayan region has increased by 65 percent from 2000-2009 to 2010-2019. Also, snow cover extent is in negative trend with indication of seasonal shift. Furthermore, the permafrost, which holds together mountainsides and acts as a natural dam for glacial lakes, is thawing due to rising temperatures. The melting of glaciers and thawing permafrost can lead to formation and development of potentially dangerous glacial lakes. Glacial lakes have increased from 1,466 with an area of 64.78 km2 in 2010 to 2,070 with area of 85.08 km2 per the report. About 47 glacial lakes are considered as potentially dangerous glacial lakes in the three transboundary river basins of Nepal. An increasing melting of glaciers and thawing permafrost can lead to catastrophic glacial lake outburst floods (GLOFs), endangering downstream communities and infrastructure.

Water crisis

The availability of freshwater from the melting of glaciers, snow and permafrost is the lifeblood for Nepal, and its precarious balance is threatened by climate change. The Himalayan region provides water to over a billion people across South Asia. The erratic and shifting patterns of precipitation, combined with the retreat of glaciers, are disturbing this balance. Nepal's agriculture, a primary source of livelihood for a majority of the population, is vulnerable to these changes. Prolonged droughts and erratic rainfall patterns are impacting crop yields and food security. As a result, the local economy and the livelihoods of many Nepalis are under immense strain.

Energy generation

Nepal possesses substantial hydropower potential, which has been considered a cornerstone for the country's economic development and energy security. There is a high potential for the export of the renewable energy (hydroelectricity) to energy-deficit countries from Nepal, which can contribute significantly to the country’s GDP and economy. However, climate change has brought forth new challenges to the sector. Changing hydrological patterns, caused by melting glaciers and altered precipitation, can lead to fluctuations in river flows, potentially disrupting hydropower generation. In addition, increasing frequency of cryospheric hazards such as GLOFs and associated cascading hazards in this region will have direct impacts on the sustainability of these projects. Hydropower projects might need to adapt to these variations, which can result in additional costs. Nepal government's ambitious plans to harness hydropower resources to export electricity to neighboring countries face increasing uncertainties due to climate-induced variations in river flows and the overall sustainability of these projects.

The way forward

On the adaptation front, the government, in collaboration with international organizations, including Green Climate Fund, is focusing on building resilient infrastructure. Such assistance is crucial in enhancing Nepal's adaptive capacity in the face of climate uncertainties. Adaptation measures can help reduce vulnerabilities, loss and damage are inevitable in a changing climate. Nepal has experienced several disasters like recurring GLOFs from rapidly retreating glaciers. These events have resulted in significant economic losses and the displacement of communities. Nepal is actively participating in global climate negotiations, including the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement. Such participation helps the country to advocate for equitable solutions and assistance.

However, the need for climate finance far exceeds the available resources. While international pledges have been made, the disbursement of funds has been slow, hindering Nepal's ability to address immediate climate-related challenges effectively. The nation seeks increased transparency and faster access to climate finance to bolster its climate resilience and mitigate the ongoing impacts of climate change. The adaptation actions also need to be expanded in the high mountain region in the form of minimizing risks from potentially dangerous glacial lakes and other cryospheric hazards.

A turning point

The recent visit of the UN Secretary-General, Antonio Guterres, to Nepal's mountain region is an acknowledgment of the country's pivotal role in the global climate system. The UN chief has sent a clear message of the worst climate change impacts on the Nepal Himalayas by pointing out that “glaciers are retreating but we cannot retreat and we must move forward for climate action”. The subsequent participation of Nepal in COP28 signifies its commitment to addressing climate change at the highest levels of international diplomacy. It will provide a platform for Nepal to voice its concerns and solutions for our Himalayas to the global community. The impact of climate change on the cryosphere, water resources, hydropower and livelihoods in the Himalayas need to be at the forefront of these discussions. The visit of the UN chief and Nepal's active participation in COP28 collectively signal a turning point in addressing climate change impacts on the Nepal Himalayas.

Efforts to promote sustainable practices, build climate-resilient communities and diversify the economy are steps in the right direction. By tackling climate change head-on and fostering international collaboration, Nepal can pave the way for a sustainable and secure future in the breathtaking but fragile world of the Himalayas.