Himalayan plunder: Hydroelectric plans in Arunachal will effect downstream Assam too

Arunachal Pradesh is highly susceptible to landslides; debris flowing downstream will change river behaviour, fear experts 

By Monoj Gogoi
Published: Monday 13 February 2023
About 150 hydropower projects have been proposed in the Himalayas across Arunachal Pradesh. Photo: iStock

Parts of this article were used in a special edition on the Himalayas, published in February 1-15, 2023, issue of Down To Earth magazine

A recent push by Arunachal Pradesh to realise its massive hydroelectric potential has faced criticism from activists, scientists and communities in the state as well as in the downstream Assam.

Arunachal Pradesh is often dubbed as the powerhouse of the country and is home to 34 per cent (50,328 megawatts) of the country’s 148,701 MW hydropower potential, according to estimates of the Hydro Power Policy, 2008.

About 150 hydropower projects have been proposed in the Himalayas across the state and have faced massive protests. On January 10, 2023, the state government decided to hand over five stalled hydropower projects to central public sector units “to unlock its potential”.

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The 1,000 MW Naying hydropower project and the 500 MW Hirong project will be handed over to the Northeastern Electric Power Corporation (NEEPCO), as per the government decision.

The 500 MW Emini hydropower project, 420 MW Amulin hydropower project and 400 MW Minundon hydropower project will be handed over to the Satluj Jal Vidyut Nigam Limited (SJVNL) for execution.

These projects would generate green power of 2,880 MW and provide revenue of around Rs 500 crore per year in free power and around Rs 100 crore for local area development, the government claimed.

However, analysts fear that the projects may heavily affect the downstream areas in Assam. There will be a massive change in the state’s economic and socio-cultural life, along with the river ecosystem, said Keshoba Krishna Chatradhara, an environmental activist from Assam. 

“The rivers will carry huge amounts of debris and sediments downstream due to deforestation and earth cutting for the projects upstream, which will change the behaviour of the rivers,” Chatradhara said. “The regulation will determine the flow regime, which can result in floods, droughts and erosion.”

Massive landslides have already been experienced in the project site Subansiri Lower Hydroelectric Project at Gerukamukh. Last year, in the monsoon, landslides heavily affected the diversion tunnels and the tunnel of the powerhouse collapsed. 

The regular landslides of different intensities are enough to prove that the rock structures in the hills of the project site are very fragile. Moreover, just about 10 kilometres east of the project site, near Jiadhal river, massive landslides have been occurring naturally for the past decade. 

These incidents indicate that the Eastern Himalayan part is more susceptible to landslides and the slightest tampering may cause huge devastation. 

Around three-fourths of Arunachal Pradesh is highly prone to landslides, Sushil Goswami, retired professor and head of the department of applied geology at Dibrugarh University, told Down To Earth

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He emphasised on slope stability map and urged for the demarcation of the reservoir area and vulnerable portions. “But nothing has been done by the dam builders in this context,” he said. 

Dam builders don’t have the vision to tackle reservoir-induced disasters, said Goswami. “Upcoming road projects will require blasting and earth cutting. The debris will naturally go to the rivers and will elevate the river beds downstream of Assam. Actual data on sediment loads in rivers are not available,” he said.

“We need the development in Arunachal, but a substantial amount of money should be kept for soil preservation and debris management,” he added. 

The hills’ health determines the plains’ conditions, says Rabindranath, an Ashoka Fellow and the founder of Rural Volunteers Centre (RVC), an Assam-based non-profit. Earth-cutting for road construction in Arunachal Pradesh causes massive landslides and blockades at the local level, he said. 

“Most of the projects in Arunachal Pradesh are only politically viable, not geologically or environmentally,” he said. Massive amounts of deforestation in the upper reaches of rivers have already increased sediment load and reduced the depth of the riverbeds in the plains in Assam, Rabindranath added.

“Massive sand casting has changed the topography of the floodplains and creates many sandbars while the rivers flow through shallow braided channels,” he said.  

The rainfall pattern in the region has changed a lot over the last decade, he pointed out. “The monsoon rainfall became more erratic and unpredictable. The frequency and intensity of climate events such as floods and droughts are also increasing,” he further said.  

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Conventional structural flood protection measures often fail now, said Rabindranath, who has been working for the flood-affected communities in upper Assam for the last 30 years. More scientific and new approaches must be adopted and affected communities must be strengthened to be adaptive and resilient. 

“On one hand, the government is focusing on disaster management and on the other it is funding destructive projects without proper assessment of damages,” he argued. “Flood early warning has been in discussions for the last 30 years, but there has been no implementation.”

“Construction of large hydropower projects, like Lower Subansiri, Dibang, Demwe Lower, etc, in Arunachal Pradesh is worrying for both Arunachal and Assam,” said Nani Bath, professor of political science at Rajiv Gandhi University. “I don’t think any precautionary measures have been taken to avert disasters or mitigate its impacts.”

Bath, who is also a renowned writer on the issues of Arunachal Pradesh, focused on the rapid urbanisation and haphazard construction of multi-storey buildings.

We don’t follow any town planning rules. Here in Arunachal, in the towns of Itanagar, Naharlagun or Aloo, we are permitted to build one plus three-storey buildings, but we have seen much taller buildings in every town,” he said. 

Rabindranath agreed there is no town planning; all structures are semi-permanent. In Arunachal, no towns have drinking water supply systems, drainage and sewage systems. “In such a topography, we must carefully plan structures,” he said.

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Large dams, which are in various stages of construction in the state, and the proposed roads would affect the fragile geology, biodiversity and ecosystems region, Shyama Prasad Biswas, professor of Life Science at Dibrugarh University, told DTE

“The rock structures in the hills are very weak and can be broken easily by grasping by hand. No expert needs to prove it,” he said. Tezu, a town in Arunachal Pradesh, was easily the most beautiful town in entire northeast India, Biswas claimed. But this is no longer the case. 

“Forests and lands were cleared along the bank of Lohit river to construct a road, which caused landslides and debris was allowed to fall into the river. The river became shallow near Tezu and started to flow in braided channels. Now, the town has no more charms,” Biswas said.  

Big dams in Arunachal Pradesh are being constructed without properly assessing the cumulative impacts on the downstream areas in Assam, he added.  

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