5 min readNew DelhiUpdated: Feb 4, 2026 09:01 AM IST
The much-delayed 250×8 MW Subansiri Lower hydel project at Gerukamukh on the Assam-Arunachal Pradesh border took 21 years since it was granted forest clearance in 2004 to commission the first of its eight units last December.
But after over two decades and six reminders from the Environment ministry, Arunachal Pradesh is yet to comply with a key condition of Subansiri’s forest clearance: raise plantations on 31.83 sq km to compensate for the forest land lost to the project.
In its last reminder to Arunachal Pradesh on May 15, 2025, the Environment ministry said that “compensatory afforestation (CA) in lieu of the proposed diversion area is yet to be done even after more than 20 years despite repeated reminders,” and sought the state’s comment on how the project would be commissioned without complying with its clearance conditions.
Underlining that Arunachal Pradesh was yet to submit information on “the identification of compensatory afforestation sites, along with geo coordinates and KML files, justification for delay in carrying out CA, status of implementation till date and details of funds received” etc, the letter said the “matter has been been seriously noted” by the ministry.
That was the ministry’s sixth reminder to the state which had not responded to its letters on the matter in October 2022, April 2022, December 2021, August 2020 and March 2020.
“A response is still awaited (from the state),” said a senior official of the ministry’s north-eastern regional office in Guwahati. Requests for comment through email and phone calls did not elicit any response from Principal Chief Conservator of Forests and principal secretary, department of Forests and Environment, Arunachal Pradesh.
The ministry started sending out the periodic reminders to the state on its CA commitment soon after the Subansiri project resumed construction work following a prolonged stoppage between 2011 and 2019 due to local resistance in Assam and court cases over issues of dam safety and downstream ecological fallout. Clear felling of trees in the project’s submergence area began in October 2021 and was completed by September 2023.
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The commissioning process of Subansiri Lower commenced with three of its eight 250MW units going on mechanical run during October-November last year. Subsequently, these units were synchronised with the national grid on December 2, 2025, January 21 and 31. The second unit started commercial operation on February 1.
Meanwhile, in April 2023, the Standing Committee of the National Board for Wildlife (SC-NBWL) decided to commission a study by Wildlife Institute of India (WII) to “prepare a plan ensuring free passage of elephants” across the Subansiri river between Panir Reserved Forest in Arunachal Pradesh and Dulung Reserved Forest in Assam.
In its report submitted in January 2024, the WII said the project’s hydro-peaking scenario — “a rise in water level by around 2 meters with a concomitant increase in the water velocity” — would resemble flash floods hitting the elephant corridor, which is “an extremely crucial link in maintaining the continuity of elephant habitats along the Himalayan foothills” in the region.
This flash flood-like peakings, the study warned, could “trigger behavioral avoidance” of the river corridor in two ways: by sweeping away or separating young elephants and calves from herds, and also by affecting the vegetation of the river islets that act as stepping-stones or mini-habitats to help elephant movement.
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Therefore, the WII recommended that the project proponent NHPC “must restrain from hydropeaking operations until a multi-seasonal hydrological modelling study in relation to impacts on elephants and its habitat are carried out.”
Two years on, no multi-seasonal study to determine the impact of the project’s hydro-peaking on the elephant corridor has been commissioned yet.
According to the minutes of the SC-NBWL meeting held on January 30, 2024, expert member ecologist Dr Raman Sukumar underlined that the east-west corridor was the most important link between elephant populations on either side. “The report submitted by the WII… has brought out the issue of peaking which should not be allowed when the animals are crossing,” he said. Asked if the Subansiri Lower project will refrain from hydropeaking operations until a multi-season study determines its impact on elephant movements, an NHPC official declined to comment.
