As part of the ongoing Eco Everest expedition, an ICIMOD research team led by Basanta Shrestha revisited the Dig Tsho GLOF site in the Langmoche and Bhote Koshi valleys to study the conditions of the Dig Tsho glacial lake and downstream river banks 23 years after the lake burst out on 4 August 1985. The first results have just been communicated from the remote valley when the team reached a contact point on 15 April.
Glacial lake outburst floods (GLOF) continue to be a real threat in the Himalayan region as a result of continued glacier retreat accompanied by development of lakes, aggravated by climate change. ICIMOD, together with national institutions, is continuing its work on identifying and monitoring lakes with a potential to cause GLOFs. Lakes will be mapped and monitored in a stepwise approach using satellite imagery and remote sensing, field investigations of lake sites to determine the GLOF risk, and downstream vulnerability assessments of communities and infrastructure that could be damaged.
Satellite images indicate that the Dig Tsho has reached a stable state. The expedition could see on the ground that even if the steep Langmoche glacier retreats further, the lake won’t grow as only bed rock will be exposed. The present outlet of the lake is at the same level as the Langmoche river bed, and there is no longer any likelihood of a mass failure at the breach area blocking the outlet. Thus it is very unlikely that there will be a second outburst from this particular lake, but the effects of the first outburst are not over.
The memories of the 1985 GLOF are still alive. Two eyewitnesses of the 1985 GLOF, Lhakpa Chhamji Sherpa of Thameteng and Ang Maya Sherpa of Thamo, told the team how they saved their lives by running uphill when the sudden flood of black water washed away the micro hydropower house, fields, and dwellings. The debris and undercutting of river banks turned many fields into wasteland and still threatens the settlements.
Several landslides triggered by the Dig Tsho outburst in the Langboche and Bhote Koshi valleys are still active as the erosion due to the flood has left the slopes extremely steep. Continuing degradation of the river banks is threatening the settlements along the river valleys.
Even though the chance of a second GLOF from Dig Tsho is slim, the threat of GLOFs in the valley remains a serious threat as there are several glacial lakes close by which are growing rapidly and could burst at some stage. Such events pose a severe threat to the livelihoods of local people and the valley economy. These lakes need to be monitored on a regular basis with in-situ measurements so that preventive measures can be taken to safeguard the mountain communities and the fragile environment. As part of the Eco-Everest Expedition, the ICIMOD scientific team will be conducting a detailed field investigation and establish a pilot early warning system for Imja lake in collaboration with the Department of National Parks and Wildlife Conservation, Govt. of Nepal, and Keio University of Japan.
An Eco-Everest Trust Fund has been set up to raise funds to finance further research, and monitoring and early warning systems for glacial lake outburst floods, and to help the local community to adapt to climate change and to increase their resilience. The Eco Everest Expedition calls for contributions from all.
For more information and near real time dispatches of the Eco Everest Expedition in the Google earth environment, visit the Eco Everest website at www.ecoverest.net.np