Kolkata: Questions of whether a lack of forecasting infrastructure proved costly at a crucial time in the Sikkim glacial lake outburst flood continue to reign supreme. Reports that pre-date the disaster spoke of the government mulling cautioning systems, while environmentalists are highlighting how tell-tale signs could have been used as warning.

The disaster has led to a death toll of at least 40, and hundreds remain missing, including 23 Army jawans.

Military equipment, including firearms and explosives, was washed away by the Teesta river which overflowed as a result of the glacial lake outburst flood (GLOF). In neighbouring West Bengal, a mortar shell washed by the waters and found by locals exploded, killing one child and injuring six others.

Also read: Sikkim Flood Was a Disaster Forecast – But Warnings Were Ignored

On September 23, the Bengali newspaper Uttarbanga Sangbad had noted that fears of an "Uttarakhand-like situation" in Sikkim had prompted the decision to implement an early warning system at the lake. The report had quoted Prabhakar Rai, the director of the Sikkim State Disaster Management. The report also said that cameras had been installed at the lake's site. 

The South Lhonak Lake, situated in Sikkim's far northwestern region, is categorised as a glacial-moraine-dammed lake and is known for its rapid expansion, making it one of the fastest-growing lakes in the Sikkim Himalaya region, one of the world's most seismically active areas. In 1977, the lake covered an area of 17.54 hectares. Subsequent assessments of its areal extent were conducted using temporal satellite data from 1989, 2002, and 2008. 

In 2015, the Central Water Commission identified South Lhonak Lake as Lake 1 and estimated the area of the lake as 136 hectares and the volume as 40.8 million cubic metre. 

Civil engineer James Wilson wrote on X that between September 17, 2023, and September 28, 2023, the surface area of the lake had increased by 5 hectares.  

This is a significant leap.

Himanshu Thakkar, coordinator at the South Asia Network on Dams, Rivers and People, says that this was something that the monitoring stations should have caught.

“Even after the Chamoli disaster of 2021, the government talked about an early warning system. The recommendation for the system has been there since 2013. This is typical of our government. This is major safety lapse. The CWC’s monitoring station at Lachen, 20 km upstream from Chungthang dam shows no reading after 10 pm on October 3, 2023. When it was required, there was no reading. This is the status of our forecasting,” said Thakkar.

The Wire has reached out to CWC executive engineers Shashank Bhushan and Shailesh Kumar for confirmation of this.

A day after this report was published, officials at the Central Water Commission (CWC) said that it is possible that the CWC stations in Lachen and Sangkan may have been affected by the GLOF too. A reconnaissance mission was conducted by the team on October 9, but they have not yet managed to reestablish communication in those areas, they said.

In 2021, too, a study had highlighted the increasing length of Lhonak glacial lake.

“It was already predicted in 2021 that this lake would breach and impact the dam...When glaciers are eroding, they put pressure on the bedrock, producing more silt. Whenever there is flash flooding, you would witness more silt and debris flowing downhill, aggravating the destruction caused by floods and landslides,” Dr Farooq Azam, glaciologist at the Indian Institute of Technology, Indore, was quoted as having said.

In a 2020 publication by the American Geophysical Union, it was reported that out of the 23 critical glacial lakes in India, a significant majority, specifically 17 of them, were located in the state of Sikkim. These lakes are classified as critical due to their potential to overflow as a result of melting glaciers, posing a risk of catastrophic bursting.

In 2019, the Kolkata-based Prameya Foundation’s Right to Information inquiry with the Central Water Commission, revealed that out of a total of 16 lakes identified as vulnerable based on a vulnerability index, the top five lakes most susceptible to GLOFs were all located in the Teesta basin of Sikkim. 

Reuters has reported also that Indian scientists at the National Remote Sensing Centre had said in a 2013 report that there was a 42% chance of Lhonak Lake bursting its banks.

Construction

The Teesta River originates in the northeastern region of Sikkim, India, at an elevation of 5,280 metres, primarily from the Chombo. The Jongsong peak and Chho Lhamo also contribute as sources of water. The Chungthang dam (Teesta 3 HEP), that was breached, is at the confluence where the Lachen Chu and Lachung Chu rivers merge and Teesta is formed.

The Teesta river system has the most active floodplain of North Bengal.

“Now is the time to pause. There is a profound connection between rocks, trees, and water; this is science. With the increase in global temperatures, there will be extensive rainfall in the Himalayan region, and after the Kedarnath disaster, the government finally received a report on this matter. Glacier melting is a global phenomenon, but the government should know what to do next,” said environmentalist professor Moloy Mukhopadhyay, who also cautioned against wanton construction.

According to the National Hydropower Development Corporation (NHDC), there are at present 47 hydropower projects at various stages of development along the Teesta river in Sikkim and West Bengal. Among these, nine have already been commissioned, construction is underway on 15 dams, and an additional 28 are in the planning and development phases. 

The construction of the extensive Sivok-Rangpo rail project, connecting Rangpo in Sikkim to the Indian railway network, has raised environmental concerns. Geologists caution the possibility of compromising the stability of the mountains, elevating the potential for landslides and natural disasters. The region also witnesses a constant influx of thousands of tourist vehicles daily. 

 “As many as 14 tunnels are being excavated for the Sevoke-Rangpo railway line on this delicate mountain terrain. Regardless of the stability of the project, continuous tunnelling is causing seismic activity, raising the risk of landslides and glacier ruptures,” said Animesh Basu, an environmentalist from the Himalayan Nature and Adventure Foundation.

Basu called the situation dire, “On one side stands Sikkim's vital lifeline, the Teesta, while on the other side are Siliguri and Jalpaiguri; if a catastrophe occurs, and the Teesta and Mahananda rivers converge, the very existence of settlements in this area would be in jeopardy."

Gautam Sarkar, a senior editor at Uttarbanga Sangbad, concludes, "The Himalayas are still evolving mountains, characterised by their composition of alluvial soil, rendering them naturally fragile. The disaster cannot be attributed to the Sevoke-Rangpo railway line. Nevertheless, this railway line does play a role in the potential for future disasters."

Translated from the Bengali original by Aparna Bhattacharya.

Note: This article has been updated with CWC official's versions of why the two stations did not give readings.

The Wire is now on WhatsApp. Follow our channel for sharp analysis and opinions on the latest developments.