Sikkim government reveals insights on Lhonak lake flooding to NGT
The state government has drawn its conclusion from a report provided by the North East Space Application Centre (NESAC), which aids the Northeastern region with space science and technology.
- Gangtok - UPDATED: April 18, 2024, 01:16 PM - 2 min read
Temporal satellite images of Lhonak Lake in North Sikkim.
In a pivotal disclosure to the National Green Tribunal (NGT), the Sikkim government has provided initial insights into the events preceding last year's catastrophic flooding, which wreaked havoc across four districts and claimed the lives of over 40 individuals.
According to the state's submission, the incident was preceded by an unusual deluge of heavy rainfall, potentially indicative of a cloudburst, leading to the outburst of the South Lhonak glacial lake.
The government's assertions draw from a comprehensive report by the North East Space Application Centre (NESAC), a stalwart in leveraging space science and technology for the Northeastern region.
Although the NESAC report highlighted a temporary data gap in satellite observations during the critical hours of the incident, it underscored the substantial rainfall preceding the glacial lake outburst.
This narrative corroborates initial speculations by the National Disaster Management Authority (NDMA), suggesting that the inundation might have been instigated by heavy precipitation triggering a chain of catastrophic events.
The flooding, which unfolded on October 3 last year, resulted in significant loss of life and widespread devastation across Mangan, Gangtok, Pakyong, and Namchi districts, affecting around 100 villages.
Vehicles covered in debris following flash floods, in North Sikkim district on October 6
Sikkim is home to 694 glacial lakes, with South Lhonak being among them. Positioned at an altitude of 5,200 meters above sea level, South Lhonak is one of the 21 lakes flagged in a 2021 scientific assessment as "potentially hazardous" due to its high likelihood of outburst.
CA satellite image of Lhonak Lake in North Sikkim
The NDMA, in a statement shortly after the calamity, pointed towards a combination of excessive rainfall and the glacial lake outburst as the primary catalysts for the calamitous surge in water levels.
Subsequent investigations also unveiled the involvement of an ice avalanche in South Lhonak, further complicating the sequence of events leading to the flash flood downstream in the Teesta River.
According to the NESAC report, satellite data indicated a substantial rainfall over northwestern Sikkim before the event, with conditions conducive for further precipitation leading up to the catastrophic burst.
Despite the absence of satellite imagery during the critical period, analysis of water vapour data suggested a high probability of rapid moisture condensation and intense convection, culminating in torrential rains.
Critics, however, have raised pertinent questions regarding the state's response to the impending disaster.
Himanshu Thakkar of the South Asia Network on Dams, Rivers, and People highlighted the necessity for immediate action upon receiving information about the glacial lake outburst, questioning the delay in emptying the Teesta 3 dam.
In its defence, the Sikkim government outlined pre-disaster preparedness measures, including mock exercises conducted in May 2023 to assess the readiness of state and district authorities.
Moreover, a mock drill specifically targeting glacial lake outburst floods was conducted in September, mere weeks before the calamity struck.
A temporary bamboo bridge being set up at Chungthang, where the Teesta III dam was swept away.
Despite these efforts, the absence of an Early Warning System (EWS) remains a glaring gap, with the state government conceding that implementation was still underway at the time of the incident.
In lieu of an EWS, communication relied heavily on mobile and landline networks, police warning systems, and informal channels such as WhatsApp groups.
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