LHONAK LAKE

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Context

• Recent flash floods in north Sikkim resulted from the bursting of the South Lhonak Lake.
• Ten casualties reported, and many are missing due to incessant rains and rising water levels in the Teesta River.
• The South Lhonak Lake had been under scrutiny for its rapid expansion and susceptibility to Glacial Lake Outburst Floods (GLOF).

Details

What is GLOF?

• Glacial lakes, like South Lhonak Lake, form in front of, on, or beneath melting glaciers.
• As they grow, they become more dangerous, often dammed by unstable ice or sediment.
• If the dam breaks, massive volumes of water rush downstream, causing floods known as GLOF.
• GLOF can be triggered by earthquakes, heavy rains, ice avalanches, or landslides.

Factors Contributing to GLOF

• Glacial lakes are common in steep, mountainous regions, making them vulnerable to landslides or ice avalanches that displace water.
• The impact of climate change leads to rapid glacier melting, resulting in the formation and expansion of glacial lakes.
• In Sikkim Himalayan, rising temperatures have caused glacier melt, leading to the proliferation of glacial lakes, including the South Lhonak Lake.
• There are over 300 glacial lakes in Sikkim Himalayan, with 10 identified as vulnerable to GLOF.

South Lhonak Lake's Susceptibility to GLOF

• South Lhonak Lake had shown significant growth over the past five decades.
• An earthquake in 1991 and another in 2011, along with future seismic events, were identified as potential triggers for GLOF.
• Government authorities had been monitoring the lake's expansion and susceptibility to GLOF.

Government Action to Tackle South Lhonak Lake's Expansion

• In 2016, authorities, including the Sikkim State Disaster Management Authority and Sikkim's Department of Science and Technology and Climate Change, initiated measures to address the expanding South Lhonak Lake.
• Innovator Sonam Wangchuk supervised the implementation of a technique involving the syphoning off of lake water.
• Three eight-inch wide and 130-140 meters long High-Density Polyethylene (HDPE) pipes were installed in the lake to remove water at a rate of 150 liters per second.

Lhonak Lake and the Chungthang Dam in Sikkim

Lhonak Lake

• Lhonak Lake is a glacial lake situated in the pristine landscapes of North Sikkim, at a staggering altitude of approximately 17,000 feet above sea level. Its formation is attributed to the melting glaciers of the region, a process accelerated by rising global temperatures.
• South Lhonak Lake is a glacial-moraine-dammed lake, located in Sikkim's far northwestern region.
• It is one of the fastest expanding lakes in the Sikkim Himalaya region, and one of the 14 potentially dangerous lakes susceptible to Glacial lake outburst flood (GLOFs).
• It plays a role in the hydrological cycle, releasing water downstream, ultimately benefiting the Teesta River basin.

Chungthang Dam

• Hydroelectric Power Generation: The dam serves as a hydroelectric power generation facility, contributing to Sikkim's renewable energy portfolio.
• Water Resource Management: By regulating the flow of the Teesta River, the Chungthang Dam plays a crucial role in irrigation, drinking water supply, and flood control.
• Environmental Impact: While the dam offers valuable benefits, its construction and operation also raise environmental concerns, including alterations in river ecosystems.

Conclusion

• GLOF events, like the one at South Lhonak Lake, pose significant risks to downstream areas.
• Climate change-induced glacier melt leads to the formation and growth of glacial lakes.
• Monitoring and proactive measures by government authorities are crucial in mitigating the impact of GLOF events and safeguarding vulnerable regions.