In the essay “Who is responsible for Sikkim’s glacial lake outburst flood?” that appeared in Frontline on October 25, 2023, the author and researcher Mona Chettri wrote: “On the night of October 3, 2023, the South Lhonak Lake in North Sikkim breached, causing a Glacial Lake Outburst Flood (GLOF).
“Located approximately 60 kilometres downstream of the lake, in Chungthang town of Mangan district, was the 1,200 MW Teesta III dam, the biggest hydropower project in Sikkim. The dam was decimated by the GLOF, which also unleashed devastation on downstream areas and communities.”
A disaster of this magnitude in the fragile ecosystem of the Himalaya had long been predicted. But the interest in hydropower—classified as green energy despite its extraordinarily poor record in that respect—continues unabated. R.K. Singh, the then Union Minister for Power, and New & Renewable Energy, stated in a written reply in the Rajya Sabha on December 12, 2023, that eight large hydropower projects (above 25 megawatt), with a combined capacity of 6,037 MW, were under construction in the north-eastern region; one of these projects is the 2,000 MW Lower Subansiri dam, one of the largest hydropower projects planned in the Himalayan region, which is likely to become operational soon, after years of delay, numerous accidents on site, and cost escalations. Delays, disasters, and devolvement are the norm rather than the exception in most such projects planned across India. Yet more are on the anvil as clearances get issued.
The Himalayan plate boundary showing the major earthquakes in recent history (1897 to 1950). The Central Seismic Gap is the segment that has not been affected by any great earthquakes during the last several centuries. According to research scientists at the University of Colorado, Boulder, this suggests that the region is overdue for an earthquake with a magnitude of 8. | Photo Credit: From The Rumbling Earth: The Story of Indian Earthquakes by C.P. Rajendran and Kusala Rajendran
For instance, in Arunachal Pradesh, on August 12, 2023, the State government handed over to three Central public sector undertakings 12 long-pending hydropower projects that the private sector had taken on and then rejected as unviable. All the projects come at extraordinarily high cost—financially, socially, and ecologically. For instance, the projected cost overrun of the Lower Subansiri dam is expected to be over Rs.13,200 crore, while ecological costs involve the destruction of swathes of evergreen forests, and social costs include the displacement of people without adequate compensation or resettlement provisions. Resentment against these projects has been brewing for a long time in Arunachal Pradesh, with human rights groups and organisations pleading to let affected people have a greater say in the decision-making process. Their objections have gone largely unheeded.
Risks of big projects
The big question then is, are projects of this magnitude worth it? The answer involves not just cost-benefit analyses and understanding of the recent dismal history of the hydropower sector but another essential element: risk. Hydropower projects in the Himalaya face two real, ever-present, risks: the possibility of a devastating earthquake and ruinous floods caused by glacial lake overflows.
In April 2015, an earthquake in Nepal with a moment magnitude (Mw) of 7.8 killed over 9,000 people and injured at least 22,000; it was the worst natural disaster in Nepal since the 1934 Nepal-Bihar earthquake. It triggered an avalanche on Mount Everest, killing 22 climbers and flattening villages, decimating a third of Nepal’s hydropower capacity and destroying UNESCO World Heritage Sites in the Kathmandu valley. This came close on the heels of the Uttarakhand floods of 2013, possibly caused by a glacial lake outburst, which killed hundreds and damaged properties worth crores in India, including at least 10 hydropower projects under construction.
A man stands on the rubble of houses damaged in the 2015 earthquake in Bhaktapur, Nepal. April 6, 2016. | Photo Credit: NIRANJAN SHRESTHA/ AP
Earthquakes are likely to recur in the Himalaya: scientific studies have warned of a devastating, intense earthquake with a Mw of above 8 in the region. Across the world, one great earthquake—defined as an event that measures 8 or more on the Mw scale—happens every year or two. Data help us understand the destructive potential of such an earthquake: an earthquake with a magnitude of 8 has 10 times the level of ground shaking as an earthquake with a magnitude 7 and releases energy equal to that resulting from the detonation of 6 million tonnes of TNT.
In an article in The Hindu titled “A hydro onslaught the Himalayas cannot take” (September 3, 2021), Mallika Bhanot, a member of Ganga Ahvaan, and C.P. Rajendran, Adjunct Professor, National Institute of Advanced Studies, note that about 15 per cent of the great earthquakes of the 20th century took place in the Himalaya.
Possibility of a great earthquake
The likelihood of such an earthquake recurring in the Himalaya has been endorsed by a number of experts, including Roger Bilham, Professor of Geology, University of Colorado at Boulder, and Luca Dal Zilio, Assistant Professor of Geophysics, Earth Observatory of Singapore. In August 2020, Steven G. Wesnousky, Professor of Geology and Seismology, University of Nevada, US, published a paper in the research journal Seismological Research Letters titled “Great Pending Himalayan Earthquakes”. The principal conclusion of his paper was that geological, historical, and geophysical observations show that the entire Himalayan arc is poised to produce a sequence of great earthquakes. Supriyo Mitra, Professor at the Department of Earth Sciences in the Indian Institute of Science Education and Research, Kolkata, noted that this research matched previous studies.
Highlights
- Despite repeated natural disasters in the Himalaya, the interest in hydropower—classified as green energy despite its extraordinarily poor record in that respect—continues unabated
- Scientific studies have warned of a devastating, intense earthquake with a Mw of above 8 in the region
- It will have horrific consequences for communities living alongside these structures and downstream from them, with economic losses running into billions of dollars and environmental damage that will take decades to repair
The eminence of these scientists and their observations need to be taken seriously. Arunachal Pradesh is categorised as Zone V (at maximum risk) in the mapping of seismic zones in India and it has a recent history of numerous quakes measuring above 5 on the Richter scale, including the Assam-Tibet earthquake of 1950 with its epicentre in the Mishmi Hills that killed at least 4,800 people.
The flash flood-ravaged town of Rangpo in Sikkim, on October 5, 2023. The flooding was worsened when parts of a dam on the Teesta were washed away. | Photo Credit: Prakash Adhikari/ AP
The critical difference between the great earthquakes of half a century ago and those of today is that the damaging impact of such an earthquake on a mega-structure like a dam will be without precedence. It will have horrific consequences for communities living alongside these structures and downstream from them, with economic losses running into billions of dollars and environmental damage that will take decades to repair (if at all). The damage to the mountain ecosystem will be immeasurable, making it even more vulnerable to future hazards. Compounding the risk is the increasing threat from glacial lake outbursts as a result of climate change.
A man stands on the banks of the swollen Satluj after heavy monsoon rains in Rampur, Himachal Pradesh, on July 9, 2023. | Photo Credit: AFP
Satellite imagery and ground-level observations indicate that glaciers in the Himalaya are melting at an unprecedented rate, increasing the chances of glacial lake breaches or “outbursts”. GLOFs have already caused large-scale destruction: the Uttarakhand floods of 2013, for instance, which caused immense damage, were triggered by very heavy rainfall along with climate change-induced melting of the Chorabari glacier. As climate change gathers higher-than-expected momentum, the number of glacial lakes being created (they are formed in large depressions that were earlier eroded by glacial activity) and the concomitant risks posed by GLOFs are compounding.
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In the Chenab basin, for instance, where Lahaul is situated, the threat of such outbursts looms large: from just 55 such lakes in 2001, the basin recorded 254 in 2018, an increase of 462 per cent in just 18 years. A research paper titled “Hazard from Himalayan glacier lake outburst floods” (2019) by Georg Veh, Oliver Korup, and Ariane Walz noted with concern: “Sustained glacier melt in the Himalayas has gradually spawned more than 5,000 glacier lakes that are dammed by potentially unstable moraines. When such dams break, glacier lake outburst floods can cause catastrophic societal and geomorphic impacts.”
Threat of flash floods
In April 2024, the Indian Space Research Organisation (ISRO) released satellite-data-based analysis covering about 40 years on expansion of glacial lakes in the catchment areas of Indian Himalayan rivers. A catchment is a vast area of land usually surrounded by hills or mountains that collects water, which, in turn, is funnelled into the river through streams and underground channels. The ISRO study was meant to understand the modifications that have occurred, principally as a consequence of climate change. The results were worrying: a quarter of these lakes have expanded to about twice their size from four decades ago as glaciers retreat in the face of warming.
Another study from July 2016 led by Wolfgang Schwanghart, a geomorphologist at the Institute of Earth and Environmental Sciences, University of Potsdam, Germany, estimated that of the 177 hydropower projects located close to Himalayan glaciers, over a fifth—including many in India—could be under threat from floods caused by glacial lake outbursts. Worryingly, a large number of these hydro projects are located in the eastern Himalaya, where the GLOF risks are the highest (the ISRO study estimated that 58 lakes in the catchment of the Brahmaputra have expanded significantly).
Scientific and visual evidence
If earthquakes and GLOFs were not enough, there is another risk: of random raining of debris from the relatively young Himalayan land-mass, which is now being modified at an unprecedented rate. The European Space Agency reported on June 14, 2021, “On 7 February 2021, the Chamoli district in the Uttarakhand region of India experienced a humanitarian tragedy when a large mass of rock and ice, around 27 million cubic metres, was released from the steep mountain flank of the Ronti peak.
Muck deposited on the banks of the Alaknanda river during the repair and restoration of Vishnuprayag hydropower project’s barrage on December 6, 2013. | Photo Credit: KAVITA UPADHYAY
This collapse caused a flow of debris to barrel down the Ronti Gad, Rishiganga, and Dhauliganga river valleys, causing significant destruction along the route, killing more than 200 people and destroying two major hydropower facilities that were under construction…. The study provides satellite evidence that the disaster was caused by a large mass of ice and rock dislodged from the slopes of Ronti Peak, starting as a giant landslide that transformed into a mud and debris flow causing destruction along its path.” The BBC reported: “To put this volume [of debris] in context, it is about 10 times that of the Great Pyramid of Giza in Egypt. When the mass hit the Ronti Gad valley floor, it released the energy equivalent to 15 Hiroshima atomic bombs” (“Chamoli disaster: ‘It hit the valley floor like 15 atomic bombs’”, June 13, 2021).
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The egregious and reckless construction activity in these fragile ecosystems—both public constructions such as for roads and hydropower dams and private housing—is making the problem worse. Landslides are far more common today than they used to be, more so along slopes that have witnessed construction.
The 2023 monsoon season was disastrous for Himachal Pradesh. The Environics Trust reported: “Unprecedented rains during the current monsoon season in several pockets have wreaked havoc across the State. Extreme events such as flash floods and cloudbursts and associated landslides, subsidence and sinking of land and complete failure of populated hill slopes devastated lives across the State. Current estimates indicate 404 people lost their lives, 38 people are still missing, and 377 have been injured in the various events across the State.… Three extreme spells [emphasis added] (8 to 11 July, 14 to 15 August, and 22 to 23 August) and 163 identified landslides and 72 flash floods have been responsible for most of the impact. Kullu, Mandi, Shimla, Sirmaur, Solan and Chamba districts were some of the worst affected” (“Preliminary analysis of 2023 disaster across Himachal Pradesh”, September 2023).
There is enough scientific and visual evidence today to rethink the aggressive plan for Himalayan development and adopt the precautionary principle, one that acts before there is complete scientific proof of a risk. There is far too much at stake to continue down the current course, and in our humility lies redemption.
Gopakumar Menon is a conservationist and author with a deep interest in the Himalaya.
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