Guwahati, Dec 23: India’s largest hydropower project took a major step forward on Tuesday as NHPC declared the commercial operation of Unit–2 (250 MW) of the 2,000 MW Subansiri Lower Hydroelectric Project, marking the first power generation milestone of the long-awaited mega project in the Northeast.

The commercial operation was inaugurated virtually by Manohar Lal, Union Minister for Power and Housing & Urban Affairs, who described the commissioning as “not just a technical achievement, but a testament to years of hard work, dedication and teamwork.”

“This project symbolises India’s commitment to clean and sustainable energy. It will support the growth of the Northeast, strengthen the national grid and help advance India’s Net Zero goals,” the minister said.

The event was attended by Pankaj Agarwal, Secretary (Power), Bhupender Gupta, Chairman and Managing Director of NHPC, along with senior officials from the Ministry of Power and NHPC.

Agarwal said the Subansiri Lower project would significantly improve energy availability in the Northeast and stands as an example of India’s push towards modern, sustainable power systems. He stressed the importance of timely commissioning of the remaining units, noting that the project would play a critical role in India’s transition to a Net Zero energy future while delivering socio-economic benefits to local communities.

Gupta expressed gratitude to the Centre, the governments of Arunachal Pradesh and Assam, former NHPC leadership and project teams, saying the project would strengthen the national grid, support sustainable development in the Northeast and provide reliable renewable power to meet rising demand.

With Unit–2 now operational, NHPC said three more 250 MW units are expected to be commissioned shortly, followed by phased commissioning of the remaining four units during 2026–27. Once fully operational, the 2,000 MW Subansiri Lower project is expected to generate about 7,422 million units of renewable electricity annually.

Located on the Subansiri River along the Assam–Arunachal Pradesh border, the project is designed as a run-of-the-river scheme with small pondage and comprises eight units of 250 MW each. It features the largest dam in Northeast India—a 116-metre-high concrete gravity dam—which also provides flood moderation and improved water management in the Subansiri basin.

As the first cascaded dam on the river, the project offers a flood cushion of 442 million cubic metres. Of the gross reservoir storage of 1,365 million cubic metres at full reservoir level, around one-third is kept empty during floods to absorb excess water and protect downstream areas.

The Subansiri Lower project incorporates several engineering milestones, including India’s heaviest hydro generator rotors, largest stators and main inlet valves, and the country’s first use of Rotec’s Tower Belt system for dam concreting.

NHPC has also invested around ₹522 crore in riverbank protection and erosion control works along the Subansiri River, covering stretches up to 60 km downstream. These measures have stabilised riverbanks for over five years, the company said.

Beyond power generation, the project is expected to deliver wide-ranging benefits. The Northeast will receive 1,000 MW from the project, while Arunachal Pradesh and Assam will get free power allocations. Electricity will be supplied to 16 beneficiary states across the country.

During construction, around 7,000 local people were engaged daily, generating significant employment. With steady power supply, NHPC expects new small-scale industries to emerge, reducing outmigration and boosting local economies. The project is also expected to support tourism and river navigation over the long term.

NHPC has spent about ₹155 crore on CSR initiatives in Arunachal Pradesh and Assam, including school toilets under Swachh Vidyalaya Abhiyaan, a Vivekananda Kendra Vidyalaya in Dollungmukh, drinking water facilities, sanitation projects and rural infrastructure works.

Also Read: Guwahati prepares for a quieter Christmas as Assam mourns Zubeen Garg

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