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Lower Subansiri HEP Project Landslide Causes Environmental Concern, Raises Questions About Safety and Accountability

Lower Subansiri HEP Project Landslide Causes Environmental Concern, Raises Questions About Safety and Accountability

Our concern about the Lower Subansiri HEP project before we die.

To the project authority and to the district administration.

The river has been drying up.

Landslide above the diversion tunnel of the 2000 MW Lower Subansiri Project is more than just a problem with landslides, e-flow, and river health. There are also issues regarding the level of trust between the construction company and the local populace. The NHPC is demonstrating that they hold excessive control over others, limiting the views of those who affected.

The maximum flow of River Subansiri is 18000 cum/s. Also, the minimum is about 131 cum/s. The authorities say its flowing with 997 cum/s at the moment. What would the health of the river be like if it dropped to zero? Even if it is only for an hour. NHPC has consented to operate a turbine continuously for a flow of 240 cubic meters per second of water following a lengthy discussion with the downstream community to ensure the preservation of river health. This time, due to the landslide the river water stopped flowing for almost 18 hours (from 11am on October 26th to 7am on October 27th, 2023). People can cross the river by running from one bank to another.

What damage has been done to the environment during this period? Could NHPC provide any information? They must undergo a damage assessment.

Why are they not concerned about the environmental flow in accordance with their agreement if it was a pre-planned activity? The incident took place at 10:30 in the morning. However, NHPC statements come out around 11:30am. And, surprisingly, the advisory note circulated by the Lakhimpur and Dhemaji district authority was circulated around 5:30 PM. It is clear that they are irresponsible towards the security of downstream living communities, regardless of the ecological damage they caused by paralysing the river for almost 18 hours. The district administration, on the other hand, is utterly misrepresenting the information regarding the landslide, claiming it is related to the reservoir operation. The authority mentioned clearly in a press statement that it was due to the landslide.

The issue is not related to human security, but also to the flora and fauna. Are you the DM who only works for humans? Where are the forest, social forestry, and fishery departments of Assam? In this crucial time whereas you live on it.  Are you people going to take responsibility for the injustice done to those river-based floral and faunal species, including your state animal Gangatic river dolphin?

The issue doesn't end with these responsibilities alone. This is a question of faith. We believe that the day you intend to completely shut down the river is significant for those who depend on it and live nearby.

Therefore, it is essential that they gather to witness the incident with their own eyes. But you aren't in a position to do that, means you don't feel confident about your design. Then, why people of downstream will believe in you if you don't have that much confidence in the initial phase of operation? If we look at the landslide history from the last three years, there have been many more.

From May 2020, there were accidents and landslides in Lower Subansiri.

May 27, 2020:  landslides around 200 meters away on the right side from dam site.  Cracks were also developed on the hills near the construction site following week long rains.

June 19, 2020:  breached the coffer dyke at project site. Landslides in the area close to the dam site damaged the cladding of the diversion tunnels of the river.

May 27, 2020: landslides and damages to claddings of the diversion tunnel.

July 2020: two guard walls of the dam collapsed at the dam site due to landslides.

August 26, 2021: The flood water toppled over the main dam for three consecutive days wreaking havoc in the downstream area. breaching the guard wall

April 3, 2022:  A large part of the hill, made of soft, sedimentary rock, located at the left bank of the river Subansiri, slid down heavily and violently in the river basin by producing a robust sound and affecting the Diversion Tunnels of the project adversely.

August 22, 2022: Rajen Saikia (38), dead on the spot at the Block No. 2 of the main dam on due to electrocution

September 16, 2022: torrential rains a major cave-in (sink hole) occurred at the dam site resulting in breaking off a part of tunnel number 2

September 23, 2022:  diversion tunnel of the project was damaged due to landslides

September 25, 2022: “partial” flooding of the powerhouse.

October 12, 2022: delaying the repair works which were being carried to recover damages caused by the flash floods.

April 3, 2023:  landslide during pre-monsoon rain in the region. The National Hydro-Electric Power Corporation (NHPC), however, said it is “on target” to begin operations in the project by June this year. Damage unknown. CEA sought safety audits. Target for commission delayed. Set new target on Jan 2024

May 1, 2023: landslide in left bank of the damsite create havoc. Flooded the powerhouse too.

June 15, 2023: Dead body shown flowing down the damsite. No investigation taken.

June 2023: The trail practice from the spillways, release water shown fluctuation of 2 meter above fluctuation in Bhimpara.

Two important points are clearly coming out here; first, is about the failure of technology to predict the landslide. Secondly, you are not accountable for the community in the downstream.

Furthermore, you are accountable for adhering to the guidelines provided by the downstream impact assessment expert group. Not only the expert team the three-member committee also said that "maintaining constant flow for the survival of flora and fauna, flood control and flood forecasting mechanism, sediment management, protection of Subansiri banks, provision of social security for the riparian population, dam break analysis, etc. have to be taken care of as per the recommendations of different committees."

Nevertheless, before fulfilling the conditions accepted by yourself, why you are in a rush to complete the project is unknown to the people like us living in just below the project.

(K.K. Chatradhara has initiated a series of writings pertaining to the Lower Subansiri Project. This is the beginning of what he wrote. 28th of October 2023, Gogamukh, Assam, India)

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Keshoba Krishna Chatradhara's picture

Keshoba Krishna Chatradhara is an eminent river activist and social researchers looks after the rivers and dams in northeast from last seventeen years. He can be reached at

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