Nepal’s effort in mitigating GLOFs

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.