Quantcast
Back to news
28 Sep 2015 | News

Investigating Lemthang Tsho (Lake) outburst in Bhutan

2 mins Read

70% Complete

Early in the evening on 28 June 2015, a yak herder in Bhutan witnessed an alarming spectacle, water from Lemthang Tsho (Memari) Lake, which had filled beyond capacity, burst over its embankment.  He witnessed a glacial lake outburst flood, or GLOF.

An early warning system installed in the Puna-Tsang Chu valley was sounded, to alert the communities of the impending danger.  But many in Bhutan were still remain concerned about residual hazards and risks from other glacial lakes.

The Department of Hydro-Met Services in Bhutan asked for assistance from the International Centre for Integrated Mountain Development (ICIMOD) in scientifically documenting the cause, process, evolution, and effects of the lake outburst; and assessing potential GLOF hazards from glacial lakes in the adjoining valley.

In response, experts from ICIMOD joined the Bhutanese team in investigating the lake, which is situated in the Mo Chu catchment 4230 meters above sea level.

GLOFs often gush down the Himalayas’ mountain valleys with disastrous results causing damage and loss of life in downstream villages. GLOFs could occur more frequently as climate change speeds glacier melt. It is important to learn as much as possible about these events and the dynamics behind them.

“The Lemthang Tsho Lake Outburst was triggered by a sudden drainage of two interconnected supra-glacial ponds [ponds of water that formed on the glacier] at the headwater of the lake”, said Samjwal Bajracharya, ICIMOD’s remote sensing specialist. He noted that the lake outburst emptied Lemthang Tsho, leaving behind a glacier-fed stream in its place.

The GLOF investigation team said that overflow of the supra-glacial ponds increased the discharge from Lemthang Tsho starting at 3 pm on June 28. The increased water discharge caused channel erosion, widening the lake’s outlet to 30 meters and displacing big boulders in the moraine, resulting in the GLOF. The outburst washed away four cantilever bridges and some horse trails, and it also activated a landslide downstream.

The river swelled to 250 centimetres during the flood. For reference, this was over two meters higher than the previous reference river discharge of 38.76 centimetres at the end of July.

The assessment team also found that the other three lakes located in the vicinity did not pose any risk of glacial lake outburst flood. Two lakes in particular, Latshokarp and Langdo Latshokarp, which were previously listed as potentially dangerous glacial lakes in an ICIMOD report (2011), have now been removed from the list.

The findings were presented to the Minister of Economic Affairs and stakeholders from different government agencies during a workshop held on 14 August 2015 in Thimphu, Bhutan.

ICIMOD’s support for this activity came through the SERVIR-Himalaya Initiative and Cryosphere monitoring programme. SERVIR is a joint development initiative of USAID and NASA, working in partnership with leading regional organisations around the globe. SERVIR-Himalaya is implemented by ICIMOD.

 

Stay current

Stay up to date on what’s happening around the HKH with our most recent publications and find out how you can help by subscribing to our mailing list.

Related Contents

Continue exploring this topic

21 Jan 2020 Cryosphere
Balancing hydropower development and freshwater ecosystem conservation in Nepal

Freshwater ecosystems such as lakes, rivers, streams, springs, and wetlands provide various direct and indirect services. They are a critical ...

Anchoring Transboundary Cooperation: Vegetation and Land Use Type Map of Kailash Sacred Landscape

Kailash sacred landscape covers more than 31,000 km2 geographical area and is spread across China, India, and Nepal. It exhibits ...

10 Jun 2016 KSL
Mapping Kailash Kora for Conservation and Promotion of Responsible Heritage Tourism

Researchers from Sichuan University, China visited the International Centre for Integrated Mountain Development (ICIMOD) in Nepal 18-22 April 2016 to ...

27 Feb 2016 News
Enhancing the Large Cardamom Production

Large cardamom (Amomum sabulatum Roxb) is the high value cash crop and main source of cash income for farmers in ...