Kolkata: Over 40 years, as climate change accelerated and the glacier that supplied it began to melt, the South Lhonak lake at 5,200 m in the eastern Himalayas, 4 km from India’s border with China, grew nearly 10 times in size, from the size of 33 football fields to nearly 300.

This change in size of the lake—from 17.54 hectares in 1977 to 160 hectares by 2017—drew the attention of many scientists because it was unusual in geological terms. A decade ago, a report in the journal Current Science warned of its “hazardous nature” and its potential for downstream devastation.

Then, on the night of 3 October—just as the planet had recorded its hottest-ever month of heat, wildfire and flood, since data was available—the swollen lake burst through its embankment of glacial debris, reducing overnight in size by nearly a third to about 60 hectares.  

Torrents of water from South Lhonak barrelled through the valley of the Teesta river, which it feeds, devastating downstream areas, washing away people, villages, buildings and the sheer concrete spillways of the river's biggest dam,  the 1,200 megawatt (MW), six-year-old Teesta Stage III hydroelectric project, just 62 km downstream of the lake. 

The breach of the dam caused one of the worst disasters that the northeast Indian state of Sikkim has faced: more than 100 feared dead and a dozen missing after more than half a month. 

About 50 km downstream, the wall of water overwhelmed the 510 MW, 15-year-old Teesta Stage V dam, flowing over its crest to devastate bridges, roads and homes. Another dam, the 500 MW Teesta VI, 70 xx km further downstream from Stage V, suffered major damage.

Over 23 years, in 14  reports, research papers and disaster-related government publications, a slew of experts, from independent scientists to State auditors, have repeatedly warned of the risks posed by glacial melting and large dams in the Eastern Himalayas;  that India’s laws were being ignored in clearing such dams; and that the Teesta was at risk of being hit by catastrophic floods, such as the one that came along on 3 October. 

One warning was delivered 16 years before the Stage III dam was completed, and the latest came in 2022. Apart from the three ravaged, there is one more dam, Stage VI, under construction on the Teesta, a major north bank tributary of the Brahmaputra river, and another one on Teesta’s tributary, Rangeet (Rangeet Stage IV). Besides, are stalled projects waiting for resumption of work. 

These dams, violating norms, local opposition and ignoring warnings, were built because the Sikkim government hoped they would be revenue sources to compensate for falling union government funding, but the opposite appears to have happened.

The Rs 13,965 crore Teesta Stage III is the Sikkim government’s biggest public sector project, with the government owning a 61% share. It was marked by cost and time overruns: it was inaugurated in 2017, late by six years and more than double its budgeted Rs 5,706 crore. 

On 31 August 2022, the project had a debt of Rs 8,008 crore.

Early Indications, Acknowledged & Ignored

Sikkim embarked on its hydropower push in the late 1990s, fully aware of the impacts that climatic changes were likely to cause: to the melting of Himalayan glaciers and creation of swollen glacial lakes. 

“The water in the Teesta is flowing at an all time low,” said then chief minister (CM) Pawan Kumar Chamling in September 1999, who noted that the Zemu glacier, the largest in the eastern Himalayas, had receded by up to 4 km. “We have had the warmest winter in living memory. These are all indications of things going wrong.” 

Chamling—who as India’s longest-serving CM ran the state for a quarter century—ignored his own warning. That year, the union government approved one of Chamling’s priority projects, the National Hydropower Corporation’s (NHPC) Teesta Stage V dam, one of six planned on the Teesta.   

About two decades later, warnings of the risk posed by climatic changes for large projects in the Himalayan region had increased, worries reflected in the Fifteenth Finance Commission (FC)’s suggestions to Sikkim in 2019. 

The government of Sikkim, among other things, informed the FC that the state was “susceptible to earthquakes and it is prone to flash floods and landslides during the monsoon,” and that “climate change is posing risk from potentially dangerous glacial lakes in Sikkim Himalaya”. 

The FC’s response was to encourage Sikkim to “speed up the execution of the ongoing Hydel Projects so as to exploit the potential and to increase the revenue earnings”.

Same Policies Before & After The Great Flood

There has been no fundamental change to the build-despite-the-risk approach before or after the great flood of 3 October.

Three days later, on 6 October, while informing the media that the dam was “fully damaged… washed out”, chief minister Prem Singh Tamang blamed “sub-standard construction” by Chamling’s government. He gave no indication the state’s hydropower policy would be altered in the wake of the catastrophe of which he was repeatedly warned.  

Chamling denied Tamang’s accusation and asked why Tamang’s government took no punitive action if construction was substandard. 

Indigenous people have opposed Sikkim’s hydropower development since 2008, particularly resisting the Stage IV dam, said Gyatso Lepcha, general secretary of Affected Citizens of Teesta, an advocacy group. Tamang, he added, had not said about reviewing the hydropower policy because it wanted to build the Stage VI and Stage IV dams. 

Two years after popular resistance began, Sikkim University’s founding-vice-chancellor, Mahendra P Lama, warned of potential devastation to the “fragile ecology” of Sikkim, where “scores of hydel projects” had been “imposed on a calm and serene Teesta river”.

“The people of Sikkim and around face unprecedented vulnerability from both the large-scale, intensive and widespread destruction likely to be unfurled by these rampant projects, and also the deep livelihood and socio-cultural damages and dislocations triggered by any changes in the glacial geomorphology,” said Lama in his book, Climate Change and Sustainability in Mountain Areas: Scope and Challenges for Regional Cooperation and Integration.

These concerns unfolded among local communities, whose opposition to dams on the Teesta the state and union government ignored by violating Indian laws. Today, Lama said he was “upset” that all warnings issued over the years were ignored.

“People are not against hydel power projects as much as they are against the way these projects are done,” Lama told Article 14, “the casualness with which the environmental impact assessment is conducted and clearances are given and the way project developers are selected.” 

Lepcha said large hydro projects should be “totally prohibited” in Sikkim. “Even though the gram panchayats on the right bank of Teesta have twice rejected the proposal for Stage IV, the government is continuing with its efforts,” said Lepcha, referring to the Scheduled Tribes and Other Traditional Forest Dwellers (Recognition of Forest Rights) Act, 2006, popularly called the Forest Rights Act or FRA,, which says no project can be built with the consent of local communities.

“As per latest information with us, the administration initiated the process of land acquisition just a few days before the Teesta III mishap happened,” said Lepcha. “We will continue to resist Stage IV and demand decommissioning of existing large dams.” 

The Sikkim-based Citizen Action Party has demanded that the Teesta Stage IV dam be cancelled.

On 18 October, the Sikkim cabinet constituted a technical committee. to “look into the causes of the recent disaster” and “suggest further course of action to the government,” including “a comprehensive plan of action” for the glacial lakes. There was no word on reviewing the policy of building dams in the Himalayan region. 

There was no reply to Article 14 emails to chief secretary Vijay Bhushan Pathak, asking if the government had begun land acquisition for the Teesta Stage IV dam and if the government was considering a review of its large-dam policy in the wake of the 3 October disaster.  We will update this story if there is a response.

Sikkim’s New Oil

“I personally feel that the water resources in Sikkim can be compared to the petroleum resources of the Arab countries,” Chamling had said in January 1997. 

It was a time when the world was reconsidering large dams due to a range of adverse socio-economic and environmental impacts and resistance movements that had begun to dominate the dam discourse since the 1980s. 

In 1997, the International Commission on Large Dams (ICOLD), a global nonprofit, released a ‘position paper’ pointing out that large-scale development demanded  “integrated planning” for an entire river basin, not piecemeal construction. 

“The larger the project, the greater the effects on the natural and social environment to be expected, and the wider the scope of the multidisciplinary, holistic studies which they require,” said the paper. 

But Sikkim, encouraged by the government of India’s Mega Power Projects Policy of 1995, had already planned a cascade of six large dams on the Teesta, Sikkim’s main source of surface water.  

In 1997, the International Union for Conservation of Nature (IUCN), a global nonprofit, and the World Bank released a report, Large Dams: Learning From the Past, Looking at the Future, which pointed out that large projects, such as dams, may have lesser relative risks than small projects because they were subject to more study. 

But if such projects went wrong, they could exert a potentially disastrous effect on even a national economy. 

“In many instances, it would be less risky to build a number of smaller schemes with equivalent total capacity, even if this would be achieved at a higher overall present value of cost, as this would spread the risk,” said the IUCN report. It added that a series of smaller projects had a lesser chance of ending up as an overall economic failure, which developing nations in particular could ill afford. 

“The higher overall cost (of multiple smaller projects) can be seen as an insurance premium against disastrous economic performance,” said the report. 

These suggestions were mirrored 13 years later in India.

In 2010, a task force constituted by the Planning Commission mentioned “congestion of hydropower projects & associated threats of mega projects” and “reduced (water) flow due to hydropower projects” as concerns in the Indian Himalayan Region and recommended setting up of “decentralised hydropower generation through network of small hydro-power units”. 

All hydel projects, big or small, had environmental and social impacts, noted a 2014 report by experts constituted by the Supreme Court of India. But small projects had “less intense” impacts while “large projects often lead to massive impacts…and may result in permanent scarring of nature and society”.

“A combination of solar panels and micro hydel can be made, where during monsoons micro-hydel can be used to generate electricity and during winters when the flow of water is less, sunlight can be harnessed to generate electricity,” said the Supreme Court experts, referring to the Himalayas.  

“There is every reason to suggest that the standard pattern for hydro power generation, distribution and consumption within the IHR should be decentralized and networked through small projects only,” said the Planning Commission report. “It also seems logical and essential to demarcate zones in the higher Himalayan region that are naturally unstable. In these areas, no hydropower projects should be allowed to be developed.” 

To back its reasoning, the Planning Commission Task Force reported that 14 glacial lakes in Sikkim had been rated as “potentially unstable”, referring to a 2003 study that mentioned South Lhonak. 

Clearances Without Surveys

In the 1990s, risks associated with melting glaciers were not yet part of global hydropower discussion, but they certainly were an issue of concern to the Himalayas. 

But Sikkim was thinking of large dams. 

In 1998, Chamling requested Prime Minister Atal Bihari Vajpayee for an “expeditious investment clearance” for the 510 MW Teesta stage V and clearances for Teesta stage III. 

The Stage V project got forest and environment clearance—permissions to submerge forests and assurances that environmental impacts were acceptable—in May 1999, without a survey to determine the carrying capacity of Teesta river basin, as the ministry of environment and forests itself had said in its 11 January meeting earlier that year. In May, while approving the project without such study, it said that no other project should be allowed without such a study. 

Carrying capacity refers to the maximum amount of water available naturally including stream flow and soil moisture, to meet ecological and social demands, such as domestic use and irrigation, in a river basin.

Two years later, in a 1 September 2001 speech at a meeting of the North East Development Council, Chamling explained how the share of central grants in the state’s revenue had fallen from 77% in 1983-84 to 58% in 1997-98 and how this increasing pressure on Sikkim to increase it own revenue earnings. 

Chamling identified three sources of income: a service tax on tourism; a tax on infrastructure projects; and commercial exploitation of water resources. “The commercial exploitation of water resources mainly for export to neighbouring states can also be a crucial emerging source,” he said.

In 2001, the Sikkim government published its Human Development Report, launched by PM Vajpayee. It noted that Sikkim’s major glaciers, Zemu, Onglokthang and Rathong Chu were “receding rapidly” and cautioned that a surge of water and debris caused by sudden glacial lake outburst floods (GLOF) in the high mountains could change the course of rivers. 

“This leads to a sudden rise in river flow by more than 10 feet and causes untold misery to all life forms in the Himalayan region,” the report said. 

Scientific Warnings, Local Resentment

South Lhonak Lake had not yet come to public attention when the new century began, but it did in 2005, when it featured in a list of 14 “potentially dangerous glacial lakes” identified in a study by the International Centre for Integrated Mountain Development (ICIMOD), a think tank based in Kathmandu, Nepal. 

“The area of Tista (sic) River basin is comparatively very small but the number of lakes and potential GLOF is very high compared to other study regions (Himachal Pradesh and Uttarakhand),” said the ICIMOD report. 

Another warning came in October 2007, when the union government’s own carrying capacity report of the Teesta river basin was published. Commissioned by the ministry of environment, the report said that South Lhonak lake’s embankment, made of moraine or unconsolidated glacial debris, had evidently breached once in the past and could breach again. 

“The study of recent aerial photographs and satellite images shows a very quick regaining of lake water volume,” said the environment ministry report. “At present it is refilled again with water and poses danger.” Apart from cloudbursts, “there are always chances of avalanches from mountain glaciers, which may break the damming material and cause GLOFs”, it added. 

The report also said a meeting with the head of the local gram panchayat revealed that the people of the Chungthang area, where the Stage III dam was to be built, were “somewhat skeptical” about the project. 

“Since the villages in the area already have electricity, they do not see any reason to have a mega hydel project in their area,” the report said.  

The environment ministry report divided the state into four zones from the perspective of biological diversity and found that a “higher diversity of mammals, birds and reptiles were found in Zone-III”, where Chungthang is located. The scientists reported in the area the presence of endangered species, such as the red panda, the near-threatened marbled cat, the vulnerable serow and the Himalayan marmot. 

“Zone-III is very sensitive, and if the development project (Stage-III) is executed in this zone (1,800m-2,800m, temperate broadleaved forest, near Chungthang), an irreversible ecological damage is expected with respect to biological environments,” said the environment ministry report.   

Neither the Sikkim government nor the union government waited for this carrying capacity report before approving Stage III, as they should have according to the environment ministry’s May 1999 orders.

The Government’s Auditor Flags Irregularities

In 2017, the government’s auditor, the Comptroller and Auditor General (CAG) took note of union government’s clearances to the Stage III dam in 2006 without waiting for the carrying capacity report.

The report pointed out that the environment ministry, while issuing environmental clearance (EC) to Teesta V, had stipulated that no other project in Sikkim would be considered for the EC till carrying capacity study of Teesta river basin in Sikkim was complete.  

Yet, Teesta Stage III got environmental clearance in August 2006, more than a year before the carrying capacity report was published. Sikkim was evidently in a hurry. 

As a 2016 CAG report pointed out, the Sikkim government in June 2004 set a target of producing 3,000 MW of additional power by the end of 2012 and, in February 2005, “allotted the project to a consortium of private developers without verifying the experience of the consortium leader”. 

The consortium leader, Athena India Ltd, was incorporated only in August 2004, said the CAG report, and “had no previous experiences in implementation of hydel projects”. The company cited in its bid document the experience of its three partners, but they existed the consortium by 2006 without mandatory permission from the state government.

Construction of the Stage III dam started in 2008, with intermittent halts for months when money ran short and the private firms involved were embroiled in disputes. 

As the dam was being built, warnings that it was on shaky ground increased.

As The Dam Rose, So Did Warnings

The Draft Sikkim Action Plan On Climate Change, published in March 2011, said that downstream in GLOF prone areas, “There should be monitoring systems prior to, during, and after construction of infrastructures and settlements in the downstream area.” 

The Plan said it was essential to install early warning systems and associated hardware and undertake remote real time monitoring with automatic data transmission.

South Lhonak Lake was growing faster than any other in Sikkim, said a 2012 report, Impacts Of Climate Change: Glacial Lake Outburst Floods, published by the Pune-based Centre for Development of Advanced Computing (C-DAC). 

The risk of a glacial flood came from not just melting but from possible earthquakes, said the C-DAC report, noting two earthquakes in the vicinity: one of 4.9 magnitude in 1991 near the glacier feeding the lake; and the other of 6.9 magnitude in 2011, just about 70 km west of the lake. 

All of Sikkim falls within seismic zone V and IV, India’s two most-active seismic zones. A 2013 warning from scientists at the National Remote Sensing Centre (NRSC) was more elaborate. It said that the South Lhonak glacier receded 1.9 km between 1962 and 2008 and the lake’s outburst probability “shows a very high value of 42%”. Anything above 24% is categorised as “very high”. 

“The very high outburst probability shows that, if the lake increases its extent (it was then 136 hectare) in due course of time, it may cause a dangerous outburst flood,” said the NRSC report, which recommended more field studies. 

Yet another warning came in 2015, from the Central Water Commission (CWC). A GLOF at South Lhonak lake would send flood waters to Chungthang within two hours, with a 4.45 m increase in water level, said the CWD report. At Teesta V and Teesta VI sites, the water level was expected to increase by 7 m and 5.4 m, respectively.  

For a comparison, the heights of waves in the 2004 tsunami that killed 10,000 in India  varied on the east coast from 2.5 to 5.2 m. 

On 4 October, CWC’s monitoring station recorded that “the first surge of water was 19 m above the maximum water level at Sangkalang,” a town 35 km downstream of Teesta Stage III. 

Warnings kept coming even after the dam had been commissioned in February 2017. 

Sikkim’s State of Environment Report, published in 2017, noted that the situation developing in Sikkim was similar to a GLOF at Dig Tsho, a moraine-dammed glacial lake in the Khumbu area of eastern Nepal. 

“The GLOF at Dig Tsho is an example that even small lakes may cause serious damage, especially if there are populated areas and infrastructure located near the hazard source,” said the Sikkim environment report. 

A 2018 research paper pointed out that the lake’s length had increased by 1.6 km between 1976 and 2016 and that “it increased drastically since 2000.” Another 2019 research paper warned that in case of a GLOF at South Lhonak, the flood would hit Chungthang town in about four hours. 

In 2020, India’s National Disaster Management Authority (NDMA) noted that the “threat to hydropower is the highest in Sikkim”.

A 2021 research paper pointed out that the “enormous volume of water in a highly dynamic high-mountain environment” made South Lhonak lake “a priority for GLOF risk management.” The presence of the Teesta Stage III dam at Chungthang had turned the “GLOF risk mitigation in relation to South Lhonak and other critical lakes in the basin” into a matter of “utmost importance,” said the paper. 

“Many settlements and assets located along the river channel at Chungthang are potentially exposed to future GLOFs, indicating the need to conduct a full environmental impact assessment and potentially undertake GLOF risk mitigation measures,” said the 2021 paper. 

A 2022 research paper identified South Lohnak as “one of the fastest-growing glacial lakes in Sikkim” and pointed out that “many settlements at Chungthang are potentially exposed to the future GLOF”.

If the only justification, then, for the Teesta’s dams is that they bring in revenue, there is no indication that is happening.

What Revenue is Sikkim Earning? 

The Sikkim government took over the Teesta Stage III in August 2015 after the private consortium building it could not finish the project. 

In 2020-21, Sikkim’s revenue earned from hydropower projects was Rs 341.19 crore. The projects include Teesta Stage III, Stage V, the NHPC’s 60 MW Rangeet dam on the Rangeet, and four private projects, of a combined 399 MW on the Teesta and the Rangeet. 

The same year, the power department spent Rs 207 crore to buy power from other states during the winter, when water flowing into dams reduces as it freezes in the high reaches of the Himalayas. The government also repaid Rs 198.33 crore in Teesta Stage III loans. 

Article 14’s analysis of the dam’s finances indicated it was more liability than asset. 

In 2020-21, Sikkim Urja Ltd needed Rs 198.33 crore to repay loans, but the royalty it earned from operations was Rs 173 crore. The government used royalty earned from another hydel project and borrowed Rs 20 crore from the State Bank of Sikkim to repay loans.

On 31 March 2021, the Teesta III project had accumulated losses of Rs 1,498 crore. The next year, losses fell, as the project posted a profit for the first time: Rs 230 crore. 

Before the dam broke, Sikkim’s power minister acknowledged that the state was “not earning anything from the project as our share of free power is directly sold to companies to repay the loans and interest”. 

“This is manageable during the monsoon period when the project runs to its full capability,” power minister Mingma Norbu Sherpa told journalists in Gangtok in July. “During the lean months, the power generated is not enough to repay the loans and interest.”  

Himanshu Thakkar, coordinator of the South Asia Network on Dams, Rivers and People (SANDRP), an advocacy group, said that large hydro projects were “unfit” for the fragile Himalayan region and were financially unviable, as reporting has borne out (here, here and here).

“That large hydro projects are becoming economically unviable can be seen from the trend that private players are pulling out of large hydro projects and public sector units are taking them over,” said Thakkar. “In Sikkim, both Teesta Stage III and Stage VI were to be developed by private players but public sector units subsequently took them over to rescue the projects.”  

Three other hydel projects being in Sikkim by private companies, the 51-MW Bhamsey, the 66-MW Rangeet Stage II and 300-MW Panam, have stalled for more than six years, for reasons that include a lack of financing and natural disasters. 

This situation is evident in Arunachal Pradesh as well. In June, Arunachal Pradesh deputy chief minister Chowna Mein said the state had cancelled memoranda of understanding with 44 private companies and would handover hydel projects to public-sector enterprises. 

Delays and cost overruns typically plague all Himalayan hydel projects. The result is higher tariffs. 

“The viability of the scheme depends largely on the execution period since the cost and benefits vary considerably with period of completion and even good projects can be rendered unprofitable due to large time overruns and cost overruns,” says the Central Electricity Authority on its website.

Meanwhile, the dam bandwagon rolled on, said experts.

“Government agencies did not learn from the 2021 Chamoli disaster in Uttarakhand,” said Thakkar. “The NDMA is speaking of installing an early warning system only after the disaster has happened. Teesta Stage III should not have been allowed without adequate spillway capacity, proper dam safety mechanism and an early warning system put in place.” 

If the dam was unviable, it should never have been built in the first place, he said.

The NDMA’s 4 October press release said that to mitigate the impact of a GLOF, an NDMA-led expedition in the first week of September 2023 had surveyed two at-risk lakes in Sikkim “in order to eventually deploy early warning systems for real-time alerts”. 

“At the next stage, NDMA has planned to install early warning systems for real-time alerts at most of 56 at-risk glacial lakes in India,” said the NDMA release.

Article 14 emailed questions to NHPC and the Teesta Stage III project developer, Sikkim Urja Ltd, asking if any early warning system was in place, what benefits Sikkim received from their project and if they had learnt any lessons from the 4 October disaster. There was no response when this story was published. We will update it if there is.

If global warming were to exacerbate extreme weather events, dams would further disturb the fragility of the Himalayan ecosystem, said Anjal Prakash, professor and research director at the Bharti Institute of Public Policy at the Indian School of Business.

“Both the frequency and severity of such events are going to increase exponentially in the future,” said Prakash, an author of Intergovernmental Panel on Climate Change reports. “The Himalayan ecosystem is the most fragile in the world and any disruption will have a problematic outcome for the people of the region.”

(Snigdhendu Bhattacharya is a Kolkata-based independent journalist writing on politics, history, human rights, environment and climate change.)

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