In recent news, the South Lhonak Lake located in Sikkim witnessed a Glacial Lake Outburst Flood (GLOF). Positioned at an altitude of approximately 17,000 feet in India’s northwest Himalayan Region, this lake experienced a rupture due to persistent rainfall. Water overflowed into downstream areas, leading to flooding in the Teesta River and impacting four districts of Sikkim: Mangan, Gangtok, Pakyong, and Namchi.
This incident was reported by the Sikkim State Disaster Management Authority (SSDMA). The situation became dire when the Chungthang Hydro-Dam on the Teesta River also breached, exacerbating the overall condition in the region.
Understanding Glacial Lake Outburst Floods
A Glacial Lake Outburst Flood (GLOF) is a sudden, potentially catastrophic flood that typically occurs when water stored behind a glacier or moraine (natural accumulations of ice, sand, pebbles, and debris) is released abruptly. Conditions for such outbursts occur when glacial lakes, formed from melting ice, collect water behind feeble moraine dams.
Unlike robust earthen dams, these moraine dams can fail suddenly, releasing large volumes of water in minutes or days, causing devastating downstream flooding. The steep mountains of the Himalayan terrain make this area particularly susceptible to GLOFs.
The Impact of Climate Change on Glacial Lake Eruptions
Climate change, accompanied by increased global temperatures, has fast-tracked the process of glacier melting in the Sikkim Himalayas. This region is home to over 300 glacial lakes, ten of which are considered vulnerable to outburst floods. Factors such as earthquakes, heavy rainfall, and ice avalanches can trigger a GLOF. These floods can release millions of cubic meters of water in a very short period, causing catastrophic downstream effects.
Sikkim’s South Lhonak Lake And Its Susceptibility to GLOFs
The South Lhonak Lake in northern Sikkim sits approx 5,200 meters above sea level. Previous warnings by scientists revealed the lake has been expanding over the years due to ice melting. Seismic activities, including a significant earthquake in 2011, heightened the GLOF risk in this area.
A plan was initiated in 2016 by the SSDMA to drain excess water from South Lhonak Lake to mitigate these risks. Visionary Sonam Wangchuk led this initiative using High-Density Polyethylene pipes to remove water from the lake, successfully reducing its volume by almost 50%.
Recent GLOF Incidents in India
In recent years, other regions in India have experienced similar GLOF incidents. In 2013, Uttrakhand received unusual amounts of rainfall, leading to the Chorabari glacier melting and the Mandakini river erupting. A glacial lake outburst flood also hit the village of Gya in Ladakh in August 2014. More recently, in February 2021, it is suspected that a GLOF caused flash floods in the Chamoli district in Uttarakhand.
Measures to Mitigate the Risk of Glacial Lake Outburst Floods
To reduce the risk of future GLOF incidents, several actions are recommended. It is crucial to establish a monitoring system for glacial lakes, using satellite imagery, remote sensing technology, and drone field surveys. Early warning systems should be installed to provide timely alerts to downstream communities at risk of flooding.
Public awareness campaigns about the risks and safety measures related to GLOFs are needed, and local communities should be educated about evacuation procedures. Drills and training programs would ensure that residents are prepared in case of a GLOF.
Moreover, international cooperation is vital, as GLOFs can have impacts across borders. Sharing information and best practices for GLOF risk reduction and management with neighboring countries can help to mitigate the risk on a larger scale.