Chungthang village, three months after Sikkim Urja’s dam collapsed. Photo: @sunitarora/X

Teesta disaster: How not to build a dam

This is a two-part series on Sikkim’s failed dam ambitions and its implications on India’s new hydel push. In Part 1, CarbonCopy retraces the events of October 3, 2023, when the Teesta river washed away the Urja dam in Sikkim. Ignoring environmental risks in the planning stage, however, had already sealed the dam’s fate years before it was built

Late last year, chickens came home to roost in Sikkim.

On the night of October 3, 2023, the Teesta river punched through Sikkim Urja’s dam at Chungthang. At 1,200 MW, Teesta III was the biggest hydel power project in the state—and one of the few privately-owned dams to come up in India since the private sector was allowed into the sector in the 2000s.

Blame for the incident was quickly pinned on a Glacial Lake Outburst Flood (GLOF)—the South Lhonak Glacial Lake, 60km upstream from Chungthang, had burst its banks. In the days that followed, however, a clutch of other contributory failures came to light. The government of Sikkim, the Union environment ministry, and National Environment Appellate Authority had dismissed locals’ concerns (including fears about GLOFs) and okayed the project.

Both dam-builders and regulators continue to dismiss risks from environmental factors. In tandem, the country’s emphasis on early warning systems continues to be weak.

This was seen in the Chamoli disaster of February 2021. Only after that did NTPC speak about setting up an early warning system. Similarly, in the days following the Chungthang collapse, the National Disaster Management Authority (NDMA) belatedly said it would expedite work on early warning systems. The CEA, too, belatedly released guidelines for slope stability

Risks like GLOFs and policy responses like early warning systems, however, are just the tip of the proverbial iceberg. Instances like Teesta III and NTPC’s Rishiganga, which was washed away in Chamoli, show that India’s dam approval process is failing to plan around environmental risks. The costs run deeper than what early warning systems alone can handle. 

For this reason, it’s useful to take a closer look at the events surrounding the collapse of Teesta III. Hardwired into its demise are larger lessons on how to not build a dam.

How the Teesta III broke

Neither the state government nor the dam builder had prepared for what happened on the night of October 3. Sikkim hadn’t installed an early warning system at the lake. It learnt about the breach only when an outpost of the Indo Tibetan Border Police (ITBP), about 8 km from the lake, issued an alert saying water levels in the Teesta were rising fast.

As for Teesta III, even after being alerted, it was slow to respond. ITBP’s alert reached Gangtok by 10:30 PM, as The Print reported. By 10:50 PM, Chungthang had been informed. Even by 11:30 PM, however, its floodgates hadn’t opened more than 20-25%. Ten minutes later, waters were flowing over the dam. Another ten minutes later, it had been washed away.

Its failure to open gates fully—despite having forty minutes to do so—flagged deeper problems. “A dam of this size does not involve mechanical spillways,” an engineer with the Central Water Commission had told Indian Express. “This (inability to open floodgates) has raised questions about dam maintenance since spillways are electronically controlled and are not supposed to require manual intervention,” wrote the newspaper.

The dam’s design itself came in for criticism. Despite Sikkim getting torrential rainfall—and despite the paucity of rainfall data—its spillways were too small. That was not all. “The Teesta III project is a rock-filled concrete dam, which is structurally more vulnerable to flooding compared to a concrete dam,” Himanshu Thakkar, convener of the South Asia Network on Dams, Rivers and People (SANDRP), told Sunday Guardian. “Teesta V, which is further downstream, was also seriously damaged, but not washed away, partly because it’s a concrete dam.”


But the GLOF wasn’t the only reason Teesta III broke. In the mid-2000s, Sikkim saw a hydel power boom where the state government, aided by the Union government, handed out hydel power concessions to untested companies. Athena Projects, which built Teesta III, was one such firm.

Even as untested companies flooded the sector, India didn’t boost its capacity to monitor dam construction, dam safety protocols or disaster management systems. In the case of Teesta III, not only did locals’ warnings about GLOFs go unheard, the Sikkim government, the CWC and the CEA didn’t ensure either early warning system or adequate spillway capacity. Thereafter, as Thakkar said, “National and State Dam Safety Organisations do not seem to have checked if the gates of Teesta III were properly operating.” 

The beginning of the end

It’s easy to understand why hydel planners were attracted to the Teesta. “(The river gathers) strength and megawatts of energy as it cascades from a high of around 5,200 mtrs where it is born to 300 mtrs, the height at which it exits Sikkim, a mere 175 km downstream,” writes Summit Times’ Pema Wangchuk in The Birds Have Lost Their Way, an anthology of the Gangtok-based daily’s reportage on hydelpower and climate change.

The first flush of official interest came in 1974, when the centre pegged Sikkim’s hydroelectric potential at 3,735 MW. The ball, however, started rolling only in 2001 when the Central Electricity Authority identified 21 large projects in Sikkim, all adding up to 3,193 MW. Thereafter, when the Prime Minister’s 50,000 MW hydropower initiative was launched, “Pre-feasibility reports for 10 projects were prepared.”

That was in 2003. In May 2004, those plans were annexed by the state government. The Sikkim Democratic Front, led by Pawan Chamling, had returned to power. Shortly thereafter, as Current News reported in 2012, a committee set up by the state power department, headed by secretary DD Pradhan, suggested all hydel projects above 25 MW be developed as PPPs. The state government would take 26% equity in these projects; and pay for that equity from the revenue it garnered from its sale of free power from each project. 

By the end of 2006, Sikkim had signed no less than 24 letters of intent—mostly with private firms—for hydel projects adding up to a combined installed capacity of 4,694 MW, all slated for completion by 2012. 

These developments mirrored those underway elsewhere in India. Arunachal Pradesh, too, signed more MoUs than the Centre’s projections. In both states, the talk was about “hydro dollars” transforming the state. Arunachal said dams would contribute as much as ₹8,000 crore to its annual income. In Sikkim, Chamling pegged annual income from dams, from 2015 onwards, at ₹900 crore.

These promises of transformation would, however, be undone by its own actions.

Mind the gaps

Dams come with well-known costs and risks. On the first, we have costs like submergence, forest loss, displacement, and changes in river flows. On the second, we have risks like GLOFs, cloudbursts, and vulnerability to construction delays which results in expensive, unviable power.

For this reason, even as Sikkim embarked on its 4,000 MW hydropower push, it needed to build administrative capacity—to oversee dam construction, operations, and disaster management. The fact that almost all private dam-builders were relatively inexperienced and were ergo subcontracting dam-building out further underscored the need for such state capacity.

That didn’t happen. “There is no competent body in the state that can deal with such gigantic projects,” Mahendra P Lama, JNU professor and chief economic advisor to the current government of Sikkim, told this writer. “And yet, the then-chief minister (Chamling) wanted an abrupt increase in hydel power capacity from hardly 60 MW to hundreds and hundreds of MW in such a fragile river system.”

These projects consequently enjoyed wide latitude on critical decisions—in their choice of contractors, the size of spillways, the quantum of environmental flows and maintenance schedules. They enjoyed this leeway at a time climate change was accelerating glacial melting and making cloudbursts more frequent.

On the night of October 3, Sikkim paid the price. Gaps in both Teesta III’s safety protocols and the state’s disaster management systems showed up. Not only did Teesta III fail to open floodgates, NHPC’s Teesta V project further downstream was taken by surprise as well. In 2014, NHPC, too, had dismissed any risk from GLOFs for projects in the Teesta basin.

Around 1:30 AM, almost two hours after hitting Teesta III, floodwaters reached this dam. Astonishingly, despite Gangtok knowing about the GLOF by 10:30 PM, Teesta V couldn’t open two gates because of “lack of time,” an engineer at the dam told The Print. Once the flood hit, five of its spillways were washed away.

A week after the GLOF, the death toll stood at 30. Over a hundred had been injured. Another hundred were missing. More than 1,000 houses had been damaged. So were dams downstream. About 14 bridges—and parts of the national highway connecting Sikkim to the rest of India—had been washed away. The damage extended beyond Sikkim, reaching into cities and villages in West Bengal. 

The questions write themselves. Why was a neophyte firm, new to the task of dam-building, given the tender to build Sikkim’s biggest dam? Why did the state disregard locals’ warnings about GLOFs—and the need to oversee dam-building (and operations) by the private sector?

The answer extends beyond Teesta III, or the Teesta basin, or Sikkim itself. Over the past 20 years, the thinking behind dam-building in India has mutated from developmentalist to something far more speculative. This political economy, as the second part of our series will describe, is creating new arrangements of winners and losers from India’s hydel pushes. 

Read the second part here.