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Artificial lowering of a glacial lake

Impacts addressed:

A glacial lake outburst flood (GLOF) is a type of outburst flood due to the increased volume of water in the lakes as a result of increasing temperatures. For e.g. GLOFs have led to devastating loss of life and infrastructure in the Himalayas. Artificial lowering of water levels of lakes is a technique to reduce the risk of glacial outburst.


* Prevent casualties and asset loss from glacial lake outburst flood.
* Enhanced capacity of local organisations in handling DRR and CCA


* Reduces need for resettlement of populations near flood areas, and therefore reduces livelihood disruption Increased storage capacity for water supply
* High costs mean government cooperation is crucial and overseas financial assistance is often required.


Less desirable. The main barrier to the use of the technology is the extreme level of logistical complexity presented by the difficult access to some glacial lakes. Lake-lowering projects often take place in remote areas with steep inclines, nearly impassable to large machinery. Concerns about the possibility of heavy equipment toppling over on the steep slopes surrounding the Thorthormi and Raphstreng lakes in Bhutan led to the use of manual labor and low-tech tools in these projects (NASA 2009). The remote mountain areas also make for harsh working conditions in high elevations (Bhutan NEC 2006).

Succes factors and requirements:

Lowering of lakes levels is most effective when combined with early-warning systems, preparedness training and planning.

Investments required:

* Costs for equipment, human resources, and maintenance
* High costs (e.g. Thorthormi Lake project in Bhutan and Tsho Rolpa Lake project in Nepal range from $1 million to $3.2 million per lake (ADB, 2014)

Countries where implemented:
Case story of implementation:

Two of the biggest glacial lake outburst flood (GLOF) risk management projects in Asia have been the Thorthormi Lake project in Bhutan and the Tsho Rolpa Lake project in Nepal. The goal of the Thorthormi Lake project is to reduce the lake level by 5 meters, or “enough to eliminate hydrostatic pressure on its unstable moraine dam” (Sovacool et al. 2012b, 117). In Nepal, the Tsho Rolpa Lake was lowered by 3 meters in 2000 through a 70-meter-long canal guiding flow into the Rolwaling River (Shrestha et al. 2013).

Other GLOF risk management measures have been implemented in mountain areas worldwide. Much of the world’s expertise in draining glacial lakes was originally developed in Peru during an extensive, decades long GLOF prevention program run by the glaciology and hydrological resources unit of the National Water Authority (Carey et al. 2012).

Content organisation:
Technology owners:

* Government
* Donors