New Delhi: The National Disaster Management Authority has sent two teams to study the risk of glacial lake outburst floods, or GLOFs, in six glacial lakes identified as ‘high risk’ in Arunachal Pradesh by the agency, per a report by the Press Trust of India (PTI).
The move, per the report, is part of initiatives undertaken by the Authority after the GLOF in South Lhonak Lake in Sikkim in October last year. The GLOF in the lake completely swept away the 1200 megawatt Teesta III hydropower project downstream, and killed more than 40 people along the banks of the river Teesta. More than 60 people are still unaccounted for.
Experts to study six high-risk lakes in Arunachal
Glacial lake outburst floods or GLOFs occur when glaciers melt at a fast rate, causing the water to be discharged downstream in a sudden burst. Among the reasons that cause such fast melting that lead to GLOFs includes climate change, in the form of increased temperatures or heavy and intense downpours.
Per the report by the PTI, the NDMA has sent two teams to study the risk of glacial lake outburst floods in six glacial lakes in Arunachal Pradesh. The teams will cover three lakes each in Tawang and Dibang Valley. The six lakes are among the 27 identified as “high-risk” by the NDMA across five districts in the state.
The team in Tawang left on August 19 to study the lake in the Mago area in Thingbu circle and the team would also cover two lakes in the Jang and Zemithang sub-divisions during the expedition, the PTI quoted sources as saying. The second team will study two glacial lakes in the Mipi circle and another in the Etalin circle, per the report.
Experts partaking in these expeditions comprise members of the National Institute of Mountaineering and Adventure, and will also conduct studies on accessibility. The Centre for Development of Advanced Computing is the lead technical agency appointed by the NDMA for the surveys, per the PTI report.
Taking a cue from the South Lhonak lake GLOF
Per the latest PTI report, the move to conduct ground surveys in Arunachal Pradesh stemmed from this GLOF that occurred in South Lhonak Lake in Sikkim in October last year. Officials with the NDMA had told the PTI in July that post-monsoon, they would conduct ground surveys in four states and a union territory – Himachal Pradesh, Uttarakhand, Sikkim, Arunachal Pradesh and Jammu and Kashmir – to analyze the vulnerability of glacial lakes in these areas. The teams will also include officials and experts from agencies, such as the National Remote Sensing Centre, the Indian Army and the Geological Survey of India, they told the PTI, adding that the GLOF in South Lhonak lake had prompted this decision.
However, there is disturbing evidence to show that authorities already knew that South Lhonak lake in north Sikkim – which is part of the eastern Himalaya – was vulnerable to GLOFs even before the October 2023 GLOF occurred. On May 13, 2022 – a full year and five months before the South Lhonak GLOF occurred – Sikkim’s Information and Public Relations Department issued a press release about the risks posed by GLOFS at the South Lhonak and Shako Cho glacial lakes, per a story in The Wire.
The press release quoted DG Shrestha, Director, Sikkim Department of Science and Technology, as saying that the South Lhonak lake was increasing in size. He also said there was an urgent need for an Early Warning System for these glacial lakes in Sikkim. Per The Wire’s story, Ada Lawrence of the Sikkim State Disaster Management Authority had proposed at a National Disaster Management Authority conference that the NDMA constitute an expert committee to study and evaluate 10 vulnerable glacial lakes in Sikkim, including the South Lhonak lake, and to work out appropriate mitigation strategies against GLOFs.
Thus, both the state and national agencies knew that South Lhonak Lake was highly vulnerable to GLOFs. However, the NDMA took no action then, per the report. Before the flash floods that occurred on the night of October 3-4, authorities did not issue an early warning in time to communities living downstream.
The need for such surveys
In April this year, the ISRO analysed satellite images of catchments of Indian Himalayan river basins from 1984 to 2023. What they found was alarming: glacial lakes in the mountain range have been expanding.
Of the 2,431 lakes larger than 10 hectares identified during 2016-17, 676 glacial lakes had “notably expanded” since 1984, the ISRO found: 601 lakes have expanded more than twice.
Of the 676 lakes that had expanded significantly, 130 are located in India. And of the 130, 65 lakes are located in the Indus, seven in the Ganga and 58 lakes in the Brahmaputra River basins. For instance, the Ghepang Ghat glacial lake which is in the Indus river basin in Himachal Pradesh showed a 178% increase in size, from 36.49 to 101.30 hectares between 1989 and 2022. The rate of increase was staggering: about 1.96 hectares per year.
“Satellite-derived long-term change analyses provide valuable insights for understanding glacial lake dynamics, which are essential for assessing environmental impacts and developing strategies for GLOF risk management and climate change adaptation in glacial environments,” the ISRO said.
A study published in the journal Nature last year found that potential GLOFs threaten 15 million people globally. People living in the high mountains of Asia – such as the Himalaya – “are the most exposed” to the impacts of GLOFs, per the study, because approximately one million people live within 10 kilometers of a glacial lake in this region (older studies have shown that the impacts of GLOFs can even occur 120 km downstream of the site). The Nature study last year also found that more than half of the globally exposed population are found in just four countries: India, Pakistan, Peru, and China.
Even more damning is that a study as far back as 2021 had specifically assessed the future GLOF hazard of South Lhonak Lake and suggested that as per one of their scenarios, the town of Chungthang – located near the Teesta III hydroelectric power project – would be most affected. And true enough, the South Lhonak Lake GLOF caused the greatest damage here in October two years later: the floodwaters swept away the dam and aggravated the death and destruction downstream.
