Introduction :- 

Glacial Lakes Outburst Floods (GLOFs), are a subject of concern in the Sikkim Himalayan region as several lakes have been formed due to melting of scores of glaciers in the region. In order to prevent any disasters due to outbursts from such lake, a project was started in the South Lhonak Lake where in high density polyethylene (HDPE) pipes have been installed to siphon off water from the glacial lake.

Disaster managers and scientists in Sikkim are siphoning out excess water from lake to prevent it from Glacial Lakes Outburst Floods.Transporting the pipes to high altitudes poses serious challenges. Yaks are used to carry the pipes and other materials to the lake situated at 17,000 ft. The way to the lake is full of steep and narrow passages. Sikkim has installed a Lake monitoring and information System (water level Sensor) at South Lhonak lake. The sensor gives the water level of the lake and also monitored the lake level when there is sudden fluctuation in water level

Glacial Lakes Outburst Floods :-

Floods caused due to outburst of glacial lakes is known as Glacial Lakes Outburst Floods. The moraine wall act as a natural dam, trapping the melt water from the glacier and leading to the formation of a glacial lake. Retreat of glaciers in the wake of global warming is expected to increase the number of glacier lakes and also expand the size of the existing ones. The formation of moraine-dammed glacial lakes and glacial lake outburst flood (GLOF) is major concern in countries such as Bhutan, Tibet (China), India, Nepal and Pakistan.

The Himalayan states, Uttarakhand, Himachal Pradesh and Jammu and Kashmir, are surrounded by about 200 potentially dangerous glacial lakes formed by glacial melt but till date no early warning system is in place to evacuate people in case these lakes breach their thin walls of debris and loose soil.In addition, this process can be further influenced if more glacial lakes are formed due to increase in debris cover and if black carbon (soot) is transported in accumulation areas of the glaciers.

Factors triggering GLOFS :- 

• Rapid slope movement into the lake and melting of ice incorporated in dam are both directly and indirectly linked to glacier retreat which have increased due to anthropogenic factors. Retreat of glaciers in the wake of global warming increases the number of glacier lakes and also expand the size of the existing ones.
• The radiative balance- the balance between the amount of energy received by the earth from the sun and the energy it emits back has changed in the Himalayas in recent years due to human activities,. This imbalance “directly or indirectly results in the common incidents of fast glacier melting, glacial lake outbursts floods.
• In recent years, increasingly erratic and unpredictable monsoon rainfall patterns and increased climate variability have led to severe and frequent flood disasters. • The contributing human activities include mass tourism; developmental interventions such as roads and hydropower projects; and the practice of slash and burn type of farming in certain pockets of the Indian Himalayan region.
• Black carbon also plays important factor which melts the ice on the mountain due to albedo effect. • Other Factors like Cascading processes (flood from a lake situated upstream), Earthquake, Melting of ice incorporated in dam/forming the dam, Blocking of subsurface outflow tunnels, Long-term dam degradation also trigger GLOFS.

Impact :- 

• Catastrophic Societal Impacts: The sudden and intense flooding that results can be catastrophic for nearby communities. Fatal GLOFs have been documented in the Andes and in the Hindu Kush-Himalaya region.
• Impact on Ocean Circulation: Major Glacial lake outburst floods from ice dammed lakes into oceans are considered to change circulation patterns by reducing the salinity of the surface layer of the ocean and influence the global climate.
• Impact on Geomorphology: GLOFs, have significant potential to influence erosion-accumulation interactions and sediment dynamics like bank and depth erosion of the stream/river channel, meander shift, and, in some cases, replacement of existing channels and formation of new ones or formation of erosional terraces.

Measures :- 

• Access to early warning systems and timely information is key to minimizing the adverse impacts of floods and improve the efficiency of the response.
• Continuous monitoring is needed to understand changing dynamics of Himalayan glaciers.