Tragedy at Tapovan Vishnugad hydel project: Understanding hydrology, geology of Himalayas is need of the hour
Despite the high-risk and its capital-intensive nature, India's attraction for hydroelectric power has never ceased to exist
When a picture of the wiped out Tapovan Vishnugad Hydroelectric Project clicked by the Indian Air Force appeared on social media, the raw power of nature and the vulnerability of large hydroelectric projects could not have been starker.
Over 150 people have been missing and 28 bodies have been recovered so far after a flash flood ravaged the project to the ground on the morning of 7 February this year. Most of the dead and the missing were workers working in the project site who were caught unaware by the flash flood and swept away. The ferocity of the flood water can be gauged from the water level which was recorded at 1,388 metres at Joshimath at 11 am on the fateful day while in the 2013 flash flood, the highest flood level in the same area was at 1,385.54 metres.
Trigger Warning: This video contains visuals of damage to life and property in the wake of a natural calamity. Viewer discretion advised
The construction of the Tapovan–Vishnugad HEP began in November 2006 and was scheduled to be commissioned in 2012–2013 with the first unit supposedly going online in September 2012 which however did not happen as planned.
As scientists begin searching for causes behind the tragedy, snow in the region appears to be somewhat of a catalyst from the initial assessment. According to the Environmental Assessment Report of the project prepared by NTPC for the Asian Development Bank, the project has a 3,100 square kilometres mountainous catchment area that includes the Nanda Devi Basin (20 percent of the total catchment), which drains into the Rishiganga, a major tributary of the Dhauliganga. Around 1,483 square kilometres (46 percent) of the catchment is covered in snow that extends up to Nanda Devi, the second-highest mountain in India at 7,817 metres.
Located on river Dhauliganga river in the Alaknanda basin in Uttarakhand, the NTPC-owned Tapovan Vishnugad Hydroelectric Project has four units of 130 MW each. The project which was initially scheduled for completion in 2012-13 first saw an extension up to 2016-17, followed by another one till 2019-20. Yet to be completed the project has also been affected by the inevitable cost overrun because of the delays.
On 5 April 2018, the then Minister of State (Independent Charge) for Power and New and Renewable Energy RK Singh had informed the Lok Sabha that the Tapovan Vishnugad Hydroelectric Project was already facing a time overrun of 84 months and a cost overrun of Rs 867.82 crore. The original cost was estimated to be Rs 2,978.48 crore in November 2006 which was again revised to Rs 3,846.30 crore in January 2014.
Authors Sanchit Saran Agarwal and ML Kansal, both from IIT Roorkee in their article Issues of Hydropower Development in Uttarakhand region of Indian Himalaya published in Water and Energy International in February 2017 had pointed out to a plethora of problems hitting the project ranging from financial ones caused by the powerhouse contractor to those on the technical front like delays in head race tunnel work due to late deployment of tunnel boring machine and by heavy water ingress.
Then there were many administrative issues and the flash floods in June 2013 which damaged the project infrastructure only compounded the problem. The coffer dam was also damaged in a flash flood in August 2012.
With the latest incident, the economic viability of the project itself has come under question. Earlier in the EAC, it was said, "The main quantifiable economic benefit of the project will be the value of the 2,418 GWh of incremental electricity generation added to the Northern region grid. The levelized cost of generation from the plant will be about Rs 2 ($0.0455) per kWh. The financial indicators of the project are satisfactory and the project appears to be economically viable under normal operating conditions." What the project misses now is a 'normal operating condition'.
India's appetite for hydroelectric power
Despite the high-risk and its capital-intensive nature, India's attraction for hydroelectric power has never ceased to exist. The 43rd report by the Standing Committee on Energy (2018-19) in the 16th Lok Sabha said that "the fact that against the total potential of 2,41,844 MW hydro power including pumped storage scheme, only 45,399.22 MW is actually been utilized, speaks volumes."
Terming hydropower as clean, green, sustainable, cheap and as the most preferred among the renewable sources of energy, the panel sought "optimum utilisation of our hydro potential... on a mission mode with a timeline as it has already been done in case of development of solar and other renewable sources."
At present, 2,700 TWH (Terawatt-hour) of hydropower is generated every year and hydropower forms a minimum of 50 percent of electricity production in 66 countries and at least 90 percent in 24 countries.
Collectively taken, the percentage of accidents, if the global number of dams is taken into account, is not high although it can wreak havoc in the affected areas.
As per the data from International Commission on Large Dams, "the overall failure rate of dams is around 1 percent, a time-related analysis shows that this has been reduced by a factor of four or more over the last forty years."
This has been calculated taking into account approximately 36,000 large dams listed in the World Register of Dams which have around 300 reported accidents.
Giving its rationale behind preferring hydroelectric power over thermal, the panel emphasised on the fact that the fossil fuel reserves are limited and may not last long unlike hydel which is renewable in nature. Calling it significantly cheaper in the long run, the parliamentary committee supported the investment of huge capital cost upfront while acknowledging its long gestation period. Taking a cue from a project like the Bhakra-Nangal Dam, the panel felt that hydro projects have a long useful life and don't pollute like their thermal counterparts.
At present, India is the fifth-largest producer of hydroelectric energy in the world with 197 plants capable of producing more than 25 MW.
Downstream drowns in constant fear
Whether NTPC, the public sector power firm which owns the 520 MW-Tapovan Vishnugad Hydroelectric Project, conducted studies into all possible scenarios of a dam break is not known, but the catastrophe anyway rendered all surveys meaningless. The manner in which the dam vanished in Uttarakhand has sent shivers down the spine of people particularly those living in downstream areas of functioning projects or of those under construction. There cannot be a better example than those living in the Brahmaputra Valley in Assam as they will bear the full brunt of catastrophic failures if they occur in the litany of small and massive hydropower projects planned in Arunachal Pradesh.
Although the parliamentary panel admitted serious technical and geological issues while implementing a hydropower project, there seems to be little indication of slowing down and considered them only as hindrances affecting the deadline of a project. "Geological surprises resulting from weak geology in the Young Himalayan region, lack of technology to deal with weak geology, lack of major contractors with expertise in hydropower sector, natural calamities like landslides, hill slope collapses, road blocks, flood, and cloud bursts etc. are a cause of severe setbacks in construction schedules," it said.
Fear of large-scale destruction in case of a dam failure is near permanent in the minds of people who reside downstream but the panel did little to allay apprehensions other than merely accepting that such a panic exists. "There have also been concerns of flooding in downstream areas in case of failure of large hydro dams. Various anti-dam movements, local agitation and R&R related issues indicate that wide scale apprehensions are present in the minds of local people due to construction of big dams," the report said.
Even as news reports are emerging that the Uttarakhand tragedy might be because of Landslide Lake Outburst Flood (LLOF) and not Glacial Lake Outburst Floods (GLOF), this does not negate the dangers for the hydropower projects in North East India.
There are five major river basins in Arunachal Pradesh — Kameng River Basin, Subansiri River Basin, Siang River Basin, Dibang River Basin and Lohit River Basin — and all the major rivers of the state flow into the Brahmaputra river. According to the Central Electricity Authority, Arunachal Pradesh has the potential to produce over 57,000 MW hydropower apart from the estimated potential for the development of micro/mini/small hydel projects around 1,600 MW. Under the Prime Minister’s 50,000 MW hydropower initiatives, the Union Ministry of Power has identified 89 hydroelectric projects in Arunachal Pradesh.
While the hydropower potential of the Subansiri River Basin is aggregated to a massive 10,968 MW, the aggregate capacity of the Dibang River Basin is pegged at 9,973 MW followed by an aggregate capacity of 8,217.90 MW in the Lohit River Basin.
"The nature and number of glaciers in eastern Himalaya are different than the western counterpart. Typically, the glaciers in the eastern Himalayan region are in four sub-regions -- Sikkim, Bhutan, West Arunachal and East Arunachal. There are a number of not properly mapped small glaciers which have less than a five square kilometre area and possibly they are more susceptible to climate change-related fluctuations," said professor and head in the Civil Engineering Department, IIT Guwahati, Dr Chandan Mahanta.
"With the continuous enhanced glacial melting and increased precipitation intensity due to climate change in very active Himalayan seismic zone having the potential to trigger many glacial landslides, such glacial lakes pose danger to turn into GLOF events and any downstream reservoir adds to the risk and vulnerability. So, we have to be extremely cautious about planning hydro projects in the eastern Himalayan region especially where the distance between glaciers and planned dams in less. In addition, there are already established hydro power plants at Teesta and Kameng downstream of glaciers which require continuous monitoring," Mahanta said.
In a studied warning, the professor said that currently there are a lot of unknowns to successfully predict and quantify future catastrophic events.
"The need of the hour is to prepare the baseline data to understand the hydrology and geology of these glaciers. Most of these glaciers in eastern Himalaya share the administrative boundaries of China, India and Bhutan but they all come under the same hydrological boundary. It becomes extremely important and challenging to work collaboratively on these glaciers. Also, the Himalayan alpine glaciers being situated at higher elevation adds to the accessibility difficulties to carry out field-based studies," Mahanta said.
Dam break analysis
For any hydroelectric project, the dam break analysis is critical to analyse possible situations if any catastrophic damage occurs to a dam and figure out what steps can be taken to mitigate the crisis.
"This analysis is extremely important because it will assess the extent of devastation in downstream areas depending upon the height of the water wall and its reach vis-a-vis different measurements of time. Say in two hours what is the height of the water wave and how much geographical area it can cover during that period. A dam has to be planned keeping these things in mind. But no structure can prevent what we saw in Uttarakhand," said Uma Baruah, former additional chief engineer, water resource department in Assam.
According to the Union Ministry of Power, a Dam Break Analysis and Disaster Management Plan for downstream areas vulnerable to flooding in case of dam breach are mandatory when a greenfield project is undertaken or a brownfield project has been chosen for expansion.
It is however not known how much of this data is available in the public domain for each project and what kind of mitigation plans the government has in place in case there is a catastrophic event.
"What happened in Uttarakhand on Sunday is unprecedented. When a dam is being designed normally the process is that flood data say for the last 30 or 50 years is being considered to find out the PMF (Probable Maximum Flood). So when a dam is designed on the basis of that data the structure will be safe for that volume of water. But what happened in Uttarakhand no human assessment can calculate the volume of water that may be discharged in such a scenario. The discharge that the Tapovan Vishnugad Hydroelectric Project might not have occurred in the last 100 years. Had the flow of water been at the estimated level, the project would have been safe. Beyond a certain point, the supernatural power takes over unleashing a calamity," said water resources engineer Pradip Pujari.
Run of river dams aren't foolproof
Ironic though it may sound, the Government of India often gives assurances to its people living in downstream areas of various hydroelectric projects that it is using the run of river technology and would therefore not affect the lives of the people concerned. However, when China gave a similar logic behind its plans to develop a large-scale dam on the lower Yarlung Tsangpo which becomes the Brahmaputra river in India, the Centre expressed its apprehensions forthwith.
"The mega dam is proposed inside the Grand Canyon of the Yarlung Tsangpo, where the river drops by 2,000 metres in a short span, making it an ideal place to harness hydropower. This could be the world’s largest dam, providing some 300 billion kilowatt hour of power every year. There is a fear that such large-scale damming of the river would affect the water flow downstream in India and Bangladesh. Yarlung Tsangpo is called the Siang as it enters Arunachal Pradesh from China," a Down To Earth report said.
Although it is claimed that run of river dams do not drastically affect downstream areas by not depriving them of water, the technology is however not infallible. No dam can guarantee full protection from floods and if something like the scale of Tapovan Vishnugad Hydroelectric Project happens, the devastation is nothing but certain. Whether the structure is run of river or not simply does not matter in such a scenario.
"If this volume of water is released at one go no matter what the structure of the dam is, it will give away. Run of river system is fine when the reservoir operation goes on as per plan. What happened in Uttarakhand is an accident and so far as I know the project is not complete yet. Moreover, the structure was not designed to handle this enormous volume of water," said Uma Baruah, former additional chief engineer, water resource department in Assam.
According to Climate Technology Centre and Network, the "Run-of-river hydro projects use the natural downward flow of rivers and micro turbine generators to capture the kinetic energy carried by water. Typically water is taken from the river at a high point and diverted to a channel, pipeline, or pressurised pipeline (or penstock). The technology is applied best where there is a considerably fast moving river with steady seasonal water. How much electrical energy can be generated by a hydroelectric turbine depends on the flow/quantity of water, and the height from which it has fallen (the head). The higher the head, and the larger the flow, the more electricity can be generated."
In other words,"'Run-of-River Plant' means a hydro-electric plant that develops power without Live Storage as an integral part of the plant, except for Pondage and Surcharge Storage."
While it has become apparent that if nature strikes with such a massive force, the fate of the people in and around the dam site and the downstream areas will decide their destiny, there are other situations where human greed may lead to disasters.
"How much water will accumulate in the reservoir or in the catchment area can be calculated by measuring the precipitation in the area. It can be pre-determined up to what level the water will rise in the reservoir in how much time and the sluice gate can be operated accordingly. But in many cases, it so happens that the sluice gates are not opened until the last moment to produce maximum power. This ends up causing mayhem downstream. What I want to say is that the run of the river system is fine when the precipitation is normal," said Baruah.
Although the run of river scheme tends to give a sense of security to the people downstream that the river won't dry up when the rainy season is not around, floods are a totally different ball game. The Kurichu Dam in Bhutan, which is operated by India's Central Water Commission and is a run of river installation, has repeatedly devasted villages downstream in Lower Assam by suddenly releasing water in large quantities. Similar occurrences have happened in 2004, 2007, 2008, 2009 and 2016. Worse the upstream areas often experience cloud bursts during monsoon.
Similar accusations have been often levelled against public power sector firm NEEPCO which manages the 405 MW-Ranganadi Hydro Electric Plant at Yazali in Lower Subansiri district of Arunachal Pradesh. Water discharged from the plant often floods huge areas in the Lakhimpur district in Assam which falls downstream causing a massive loss to livestock and property.
There is one benefit of a run of river scheme as the project will have relatively less impact than a storage project because the submergence area will be limited. However, there is a downside to it as well.
"Since the holding capacity of a run of river project is not much it is still bound to affect some areas downstream," Pujari said.
Nature is boss
What Percy Bysshe Shelley wrote in his poem Ode to the West Wind is perhaps the perfect metaphor to describe nature as 'destroyer and preserver'. No matter what dams will be built in a classic contest between God and science where humans will excel until God decides otherwise. The tragedy at the Tapovan Vishnugad Hydroelectric Project will remain a long-lasting misfortune for the affected families but will soon turn into mere statistics with facts, fiction and foibles hidden and apparent.
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