Field survey in Bhutan's most at-risk glacial lakes

   TwitCount

In September 2015, Department of Hydro-Met Services (DHMS) engineer Tshering Wangchuk led an eight-member team of geologists, foresters, GIS technicians and hydrologists to the glacial lakes and villages of Lunana Gewog. Accompanied by ten helpers and 40 horses, the group surveyed lakes, profile rivers and conducted a vulnerability assessment on the local people living in the area highly vulnerable to natural disaster.

Braving cold weather and challenging terrain, the team spend more than a month in the field. While in the field, the team split into their respective area of expertise and conducted assessments on lake volume, and characteristics of moraine dam composition in Lunana’s Baychung, Raphstreng, Thorthormi, and Luggye lakes.

The socioeconomic survey team met with the communities in Thanza, Tenchi, Lhedi, Shangsa and Tshojo villages, within the Lunana watershed, located at a very close proximity to the glacial lake outlets.

A river profile through water depth and sediment measurements of the Raphstreng Lake. 
Photo: Tshering Penjore/Department of Geology and Mines

Over one hundred households in close proximity to the glacial lake outlets within the Lunana watershed were surveyed on vulnerability through focus group discussions and questionnaires. Glacier lake outburst floods (GLOFs) are the primary risks to the settlements along the rivers. Researchers aimed to learn more on how the community perceived GLOFs and climate change, their capacity to adapt to future disasters, and their plans reduce their risks and losses in the future. 

Deo Raj Gurung, Remote Sensing Specialist at the International Centre for Integrated Mountain Development and coordinator of Cryosphere Monitoring Programme in Bhutan (CMP-B) stressed the importance of the research.

“Having long term glacier mass balance, snow area, glacial lakes, and downstream socio-economic database compiled using both field and remote sensing based approaches are key to understanding the impact of climate change on cryosphere environment, and impact on communities and environment”, Gurung said.  

The CMP-B is implemented by DHMS under the Ministry of Economic Affairs (MoEA) with the objective to initiate a long-term cryosphere monitoring programme in Bhutan and strengthen the capacity of DHMS to sustain the activities beyond programme period.


Before and after Lemthang Tsho GLOF (a) May 2015, by Sebastian Kammer (b) July 2015, by Sharad Joshi/ICIMOD.

GLOFs gush down the Himalayan valleys with disastrous results causing loss of life and major damage in downstream villages. A GLOF in Bhutan occurred on 28 June 2015 and emptied the entirety of Lemthang Tsho in Mochu basin. The GLOF caused by the partial breach of Luggye Tsho on 7 October 1994 is recorded as the most catastrophic event in recent history of Bhutan, both in terms of its magnitude and the loss of life, property, and infrastructure downstream. Records show that the GLOF killed 20 people, livestock, and damaged several houses, watermills, and pasture lands along its path. The event prompted the Royal Government of Bhutan to commission several research activities on glaciers and glacial lakes. 

Recent studies on Bhutan Himalaya have all showed evidence of glacier retreat. There are 25 glacial lakes identified as potentially dangerous, Thorthormi Lake being considered the most dangerous one.

'Climate warming is the driving force behind glacier retreat and the formation of glacial lakes or expansion of those lakes, thereby accelerating potential extensive downstream damage and loss of life due to GLOFs. It has become imperative to locate and map these lakes, to identify critical ones among them, and to understand hazards associated with them and mitigate or minimize the risks.” said Pradeep Mool, Programme Coordinator of the ICIMOD’s Cryosphere Initiative, highlighting that the Cryosphere Monitoring Programme in Bhutan will also address this issue as a part of comprehensive monitoring programme.

Besides being an important source for water, glaciers are indicator of climate change. ICIMOD through its cryosphere programme works with its regional partners to promote long-term monitoring of snow, glaciers and glacial lakes. Glacier research and monitoring is a resource intensive task, requiring proper planning months ahead of the expedition. Teams must have mountaineering skills, high altitude experience, and skills to undertake highly technical task like glacier mass balance measurement and glacier melt measurement. Mass balance is the change in the mass of a glacier, and represent health of the glacier body”. Such measurement works are confined to a narrow span of time as work cannot be carried out in winter months. 

Regular monitoring of high altitude climate and glaciers is key to understanding glacial lakes and their associated risks. DHMS is installing automated weather station and automatic water level stations in Thana glaciers in the head waters of Chamkar Chu. Thana glacier is selected as a benchmark glacier of Bhutan for long-term mass balance monitoring and research. DHMS will also continue to organise annual expeditions for data collection on mass balance, snow samples, and ground surface temperature.  

Karma Tsering, Director, DHMS said the project will improve understanding of the climate-cryosphere-water nexus in Bhutan and will support policies on sustainable adaptation interventions.

DHMS faces many challenges without experienced hydrologists and glaciologists within the department. To further support Wangchuk and his colleagues, CMP-B conducts timely trainings on to GIS/RS based mapping tool, and socio-economic survey techniques, measurement of glacier mass balance, ensuring long-term sustainability of cryosphere monitoring activities in Bhutan.

Wangchuk remains optimistic on the future use of his team’s research. ‘Data that we collected will help the project in preparing model input for GLOF scenario and risk assessment, and to plan mitigation measure in case of future GLOFs’ and plan future development activities, Wangchuk said.