Sikkim Teesta Disaster: Preventive Strategies?
POWER & RENEWABLE ENERGY

Sikkim Teesta Disaster: Preventive Strategies?

Teesta Urja, the second biggest run-of-the-river hydropower project in India, suffered massive damage owing to the flash flood caused by the breach in Lhonak Lake in northwest Sikkim, which submerged the hydropower project and washed away the 60-m-high Chungthang Dam. Even the 200-m bridge connectin...
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Teesta Urja, the second biggest run-of-the-river hydropower project in India, suffered massive damage owing to the flash flood caused by the breach in Lhonak Lake in northwest Sikkim, which submerged the hydropower project and washed away the 60-m-high Chungthang Dam. Even the 200-m bridge connecting the dam with the power station was washed away within 10 minutes. A large section of the dam's wall is also missing. At least three hydropower projects totalling 2,210 MW have been damaged in the Sikkim flash floods. The worst affected of the three is the 1,200-MW Teesta Stage-III hydropower plant, which was the biggest operational hydropower station in Sikkim. NHPC, India's largest hydropower public-sector undertaking (PSU), shut its 510 MW Teesta-V hydel plant due to the flash floods. Officials said that the extent of damage to the hydel station was substantial. The engineering feat, touted to be among the strongest in the world, affected human lives and property on a massive scale. WHAT CAUSED IT? Analysts say that it may have been a glacier lake outburst flood (GLOF) as Sikkim has about 80 glaciers. The Himalayan region has had a history of GLOF-related disasters including the 1926 Jammu and Kashmir deluge, the 1981 Kinnaur Valley floods in Himachal Pradesh and the 2013 Kedarnath outburst in Uttarakhand. Another reason cited is the earthquakes in Nepal with aftershocks felt in the National Capital Region since Lhonak lake is about 700 km from the earthquake epicentre, theoretically making it possible that seismic activity may have triggered the GLOF. Thus, the exact trigger for the incident is uncertain because of the remote and inaccessible terrain. PROJECTS PLANNED In 2004, the Central Electricity Authority (CEA) prepared a preliminary feasibility report of 162 hydel projects in the country with an installed capacity of 50,000 MW of power generation, of which 10 were to be built in Sikkim with an installed capacity of 1,469 MW. More projects were added later; according to the National Hydropower Development Corporation (NHDC), 47 hydropower projects are in different development stages on Teesta River in Sikkim and West Bengal. Of them, nine have been commissioned, work on 15 dams is going on and another 28 are in the pipeline to tap its hydel capacity of about 4,200 MW. Teesta Stage-III was the biggest of nine working hydro projects on the river. The power project was commissioned in February 2017 and started making profit only in 2022, generating more power than the capacity because of the heavy flow of water. This instance has brought the focus back on the series of hydel projects being built and proposed across the country. Red flags had been raised by activists since 2005 that Teesta may not survive a lake outburst. Experts pointed out that the region is prone to landslides triggered by extreme rain events, whose frequency has increased in the recent past across the Himalayan belt. Also, historical records show that Teesta River shows its fury every 50 years – the latest event was the biggest after the 1968 catastrophe. Some analysts attributed the dam collapse to devastation downstream and said that Sikkim and the Central Government should learn a lesson from the tragedy. So, the questions raised are: How safe are such projects? How safe are such projects for other states with similar topographies? What could have gone wrong? And what can be done to prevent such disasters in future? EXPERTSPEAK Commenting on the general working of a hydropower plant, a power-sector analyst said, “First, environmental surveys and inputs regarding landslide-prone areas and different environmental aspects are thoroughly examined before setting up a project. So, if an area is prone to landslides or natural calamities, a project will not be set up there. Second, the minimum drawdown level (MDDL) is the level below which the reservoir will not be drawn down to maintain a minimum head required in power projects, and that is a fair enough level to generate electricity.” Commenting on inbuilt mechanisms at most hydropower plants, he said, “Many projects have early warning mechanisms that alert operators to keep the gates open if there is an inflow of excess water. Right now, and in this particular project, it is unclear if it had an early warning system or the system did not work well or failed. The Government has set up a committee to examine these and other related elements.” With regard to measures to prevent such instances in future, he said, “There is a lot of supervision by all concerned departments and authorities at all times. At all times, the concerned authorities should ensure that IT operations and early warning systems are in place and, most important, are functioning effectively and efficiently. Site inspections should ensure all mechanisms are in place before the monsoon season begins. We can never stop emphasising on this element as it is so vital and adherence to these norms or principles are vital in view of the lives that may otherwise be lost in such disasters.” In summation he said, “All said and done, we need hydropower so we should not give up on hydropower plants as they are extremely important as a natural resource with massive potential like solar and wind.” Another power-sector analyst, on condition of anonymity, said, “This is a general statement and not about any particular case. The design aspect of the hydropower dam is intricate and the end result is an engineering marvel. There are so many elements in hydropower projects right from 24 chapters in the detailed project report (DPR), detailed surveys (including geological) conducted at various stages, electrical equipment, hydrology, the intricate spillway design, etc. Also, so many clearances are required. Most dams have early warning systems and everything is set in place in such a beautiful manner. But the operational maintenance team is just as important, if not more important, because if the dam is not being operated properly, even the most perfect design cannot help. So, regarding dams and the spillway that are solidly built, we can safely say that the dam may last a maximum of at least 100 years, if not 1,000 years.” Regarding the water level, he added, “We need to keep the level of water at MDDL during times of flood, which means the reservoir is free to absorb a huge volume of water if it comes suddenly. Also, as a safety feature most dams have remote early warning systems.” As for preventing such incidents in future, he remarked, “Dam safety has some protocols and standard operating procedures (SOPs): How silt flushing is to be done, how the dam is to be maintained, what the level of water should be in the monsoon while operating all the things that need to be implemented 100 per cent, and so on. Any company officer found not following these norms should be severely punished. Early warning systems need to be further enhanced and all working elements should be monitored regularly as set out in the SOP. If all these measures are strictly implemented, we can avoid most of the problems in the hydropower sector in future.” Insurance claim filed Meanwhile, the 1,200 MW Teesta Stage-III Hydro Power Project in Sikkim, built at a cost of Rs 139.65 billion, has stopped generating electricity. The project, however, is fully insured and Sikkim Urja, the state enterprise that runs the project, has already filed for an insurance claim. The total sum assured in the policy is to the tune of Rs 114 billion. While the process of claiming damages has begun, Sikkim Urja and the state government will also get an immediate breather from repaying the massive dues of over Rs 100 billion that they owe lenders for the loan taken to develop the project. The project cost back then was Rs 57.05 billion and its completion deadline was 2012. Teesta-III was finally commissioned in February 2017. In a related development, after hydel unit Sikkim Urja lodged an insurance claim for Rs 5 billion, Indian insurers are now raising the premiums for industrial sites, railroads, roads, tunnels, bridges and other public infrastructure assets – from December 15, the cost of insuring public infrastructure assets will go up. Need of the hour: Call for action The Union Government enacted the Dam Safety Act (DSA) 2021, which provides a comprehensive framework for proper surveillance, inspection, operation and maintenance of all large dams in the country to ensure their safe functioning and avoid disasters related to dam failure. During extreme weather events, especially during the monsoon season, dams are to be operated as per the rule curve and the operation and maintenance manual. Dam safety begins from design and construction and goes into the zone where it needs to be maintained and operated as per certain guidelines. A majority of India’s 6,000-odd dams are over 25 years old. Hazard profiling and regular assessment (of spillway capacity, etc) are mandated by the Act and it requires dam builders to conduct comprehensive dam safety evaluations. But how many of these measures are implemented is anybody’s guess. Let us take a look at two news reports. One report about the Teesta III dam said that there were no early warning systems, no risk assessment or preventive measures in place as required under the Act. Another said that the Himachal Pradesh government recently served notices to 21 hydroelectric projects, finding them guilty of non-compliance with the DSA during the July-August floods. Such instances that involve the loss of life and property cannot be ignored or wished away. The need of the hour is not a blame-game or fault-finding exercise, but a proactive call for action to prevent any such instances in future.-R Srinivasan

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