In June 2019, a study that used declassified military satellite data showed that a staggering 8 billion tonnes of ice were melting each year in the Himalaya. Along with a rise in uncertainties related to hazards and water flows in river systems, this level of ice loss has also resulted in the increase and expansion of glacial lakes. Some studies show, for example, that climate change has played a significant role in receding glaciers and increasing glacial lakes in the eastern Himalaya. The rise in the number and expansion of glacial lakes is worrisome, particularly in regards to their structural integrity. With increasing water volume, glacial lakes become unstable because of the weaker moraine walls that hold the lake in place. This results in glacial lake outburst floods (GLOFs).

The suddenness of these flood events along with the devastating impacts on downstream communities make them highly challenging. The Koshi basin, which has a documented 2,168 glacial lakes, is no stranger to the impacts – the most devastating of these being the 1981 lake burst event, in which 19 million cubic metres of water were released in an hour. That is the combined water capacity of 7,600 Olympic-sized swimming pools. The flood damage was estimated at close to USD 4 million. The basin continues to face such devastating impacts – of 24 GLOF events recorded in Nepal, 16 have occurred within the Koshi basin. Given the transboundary nature of the basin, GLOF events have staggered impacts through the basin countries, from upstream regions in China to the mid- and downstream areas of Nepal and India.

In order to manage issues stemming from the disaster-prone nature of the basin, the Koshi Disaster Risk Reduction Knowledge Hub (KDKH) at the International Centre for Integrated Mountain Development (ICIMOD) has been conceptualized as a platform for collaboration and sharing of practices on disaster management in the basin. One of its transboundary working groups is primarily concerned with addressing data availability and standardizing a methodology for GLOF risk assessment within the basin.

This transboundary working group, recently formalized at a workshop in Chengdu, China, revisited some of its working principles on data sharing and standardization. Academics from the Institute of Mountain Hazards and Environment (IMHE); Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS); and Sichuan University from China, along with those from Tribhuvan University and Kathmandu University from Nepal, discussed ongoing research in the basin and priorities going forward. On the basis of methodology developed at ICIMOD, a total of 42 glacial lakes within the basin have been identified as potentially dangerous. After further deliberations, key areas have been identified to take the GLOF transboundary working group’s objectives further. What the members do know is that the glacial lakes are expanding in area, and there are ongoing discussions on glacial lake flood risks being the highest between the months of April and October. However, beyond data availability, the resilience aspect of GLOF management requires more focus. The group has further agreed that aside from regular monitoring of glacial lakes, improving understanding on the impacts of lake breaches must be emphasized. This would require more focus on risk management and community awareness on GLOF impact mitigation.
The work of the transboundary working group will contribute to advancing knowledge on GLOFs and provide information to stakeholders and decision makers to minimize associated risks. This sets an important precedent in collaboration on disaster risk reduction in the basin. The release of seminal papers and reports on glacial lakes and GLOFs by ICIMOD(1,2,3) and IMHE(1,2,3) provide a way forward for more collaborative research. Similarly, the GLOF transboundary working group, will also fulfil key gaps in the standardization of GLOF research.

Debabrat Sukla

Finu Shrestha

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