The story so far: A snow avalanche triggered possibly by a landslide caused a flash flood in the Rishi Ganga river, a tributary of the Alaknanda in Chamoli district of Uttarakhand, on a sunny morning on February 7, washing away a functional small hydroelectric project and destroying the under-construction 520 MW Tapovan Vishnugad project of the NTPC on the Dhauli Ganga river. The death toll from the disaster was 38 as of Friday. Rescue teams were straining to locate scores of people who remained missing. These were mostly workers in the two power projects, besides some local residents.
Why did it happen?
Union Home Minister Amit Shah told Parliament that satellite imagery from Planet Labs indicated that the landslide-avalanche event at an altitude of 5,600 metres occurred in a glacier in the Rishi Ganga catchment, and covered an area of 14 sq. km, causing the flood. In the initial rescue, 12 people trapped in a tunnel in the NTPC project and 15 from the Rishi Ganga project were saved. While a fuller picture of the loss of life and destruction will emerge only after rescue operation and inquiry is complete, the disaster that struck Chamoli has turned the spotlight on several ongoing dam-based hydroelectric projects, rampant road building, tree felling for projects, and also construction practices in the State.
Comment | Dams and damages
Why is the Chamoli incident of concern?
Uttarakhand, which gained a distinct identity in the year 2000 as a separate State carved out from Uttar Pradesh, is geologically unique. As a part of the lesser Himalaya, in the populated terrane — a region bounded by earth faults — it remains active in terms of deep movement of rock assemblages. In an article in Current Scien ce in 2014, geologist K.S. Valdiya pointed to the fragility of the entire landscape from a geological point of view: “As the northward moving peninsular India presses on, the lesser Himalaya rock assemblages are compressed and are pushed under the huge pile of the Great Himalayan rocks, the latter riding southwards onto and over the lesser Himalaya. The movement has been going on since the MCT [the Main Central Thrust] was formed 20-22 million years ago.” The MCT, running east-west along the Himalaya, is where the Indian and Eurasian plates connect. The result of these geological stresses, scientists say, is weakening of rocks, making the development of large dam projects in the region unwise.
There are several researchers who refer to other characteristics that call into question the wisdom of committing vast resources to large dam-building in Uttarakhand. A key concern is the active nature of rock fractures, known as faults, which respond to earthquakes, creating enormous instability, especially along slopes. In an assessment of the proposed 315-metre-high India-Nepal Pancheshwar dam project across the Kali river in the Kumaon region, with a drainage area of 12,000 sq. km, Shubhra Sharma and colleagues wrote in Current Science in 2019 that the chosen site could witness a strong earthquake in the Nepal area from the Rangunkhola Fault, perhaps of a magnitude of 7.4, with a potentially serious fallout.
Prof. Valdiya, who advocated small low-impact dams of less than 5 megawatts as an alternative, pointed out that investigations done along rivers Kali, Darma, Gori, Western Dhauli, Alaknanda, Mandakini and Bhagirathi, which offer the bounty of hydropower, have been found to be tectonically active in recent times across the area of the MCT. In fact, many locations in a 50-km area within the MCT zone have witnessed several earthquakes of varying intensity, including those with magnitudes of over 5. Although dam builders assert that their structures can withstand even high-intensity earthquakes, researchers say lessons from large structures, such as the Tehri dam, should also be studied, since there are concerns about induced seismic effects caused by the repeated filling and emptying of the reservoir, which may be deforming the area around the young dam.
Moreover, the geology of mountains in many parts of Uttarakhand is such that the threat of landslides is high. Rocks here have been weakened by natural processes across time and are vulnerable to intense rainfall as well as human interference, in the form of house-building and road construction. The careless disposal of enormous debris from mining and construction projects has added to the problem, blocking flow paths and providing additional debris. In fact, researchers from IIT Roorkee writing in the Indian Geotechnical Journal (2018) estimate that various tourist locations such as Gopeshwar, Joshimath, and Badrinath fall within high-hazard and very high-hazard zones for landslides, as does Chamoli town, calling for preventive and protective measures.
Should Uttarakhand worry about the effects of climate change?
The IPCC (Intergovernmental Panel on Climate Change) Special Report on the Ocean and Cryosphere in a Changing Climate found that in the Himalayan ranges, there could be variations in overall water availability, but floods, avalanches and landslides were all forecast to increase. Changes in monsoonal precipitation could also bring more frequent disasters.
In 2013, catastrophic loss of lives was seen in the floods that swept Kedarnath. They were triggered by heavy rainfall over a short period in June, first destroying a river training wall, and then triggering a landslide that led to the breaching of the Chorabari moraine-dammed lake, devastating Kedarnath town.
What this means is that aberrations in the Indian summer monsoon caused by changes to long-term climate could produce even greater damage, by bringing debris and silt down the river courses, destroying physical structures, reducing dam life, and causing enormous losses. These problems are also aggravated by the erosion of mountain slopes and the instability of glacial lakes in upper elevations. On the other hand, as the IPCC Special Report points out, the retreat of glaciers in the high mountains has produced a different kind of loss — of aesthetic and cultural values, declines in tourism and local agriculture.
Are expensive hydroelectric projects worth the investment today?
In reply to a question in the Lok Sabha in September 2020, the Power Ministry stated that in the 25 MW-plus category, there are projects with a combined capacity of 12,973.50 MW under installation. Of this, eight projects totalling 2,490 MW are in Uttarakhand, most of them by the Central government. The Ministry describes this source of power as “highly capital-intensive” but without recurring cost, renewable and cheaper compared to coal and gas plants. But a response it gave earlier this month in the Lok Sabha indicates that it has been offering incentives since March 2019 to make hydropower attractive. These include classification of large hydropower projects as Renewable Energy sources, creating a separate category for hydropower within Non-Solar Renewable Purchase Obligation, tariff rationalisation to bring down tariff, and budgetary support for putting up enabling infrastructure such as roads and bridges.
The International Renewable Energy Agency estimated that in 2019, the average levelised cost of electricity in India was $0.060 per kilowatt-hour (kWh) for small hydropower projects added over the last decade. In comparison, the global cost for solar power was $0.068 per kWh in 2019 for utility-scale projects. Though hydropower has been reliable where suitable dam capacity exists, in places such as Uttarakhand, the net benefit of big dams is controversial because of the collateral and unquantified damage in terms of loss of lives, livelihoods and destruction of ecology. Chipko movement activist Sunderlal Bahuguna argued that large dams with an expected life of about 100 years, that involve deforestation and destruction, massively and permanently alter the character and health of the hills.