HomeInfrastructureArunachals Subansiri project awaits NDSA nod for commissioning of first 3 units

Arunachals Subansiri project awaits NDSA nod for commissioning of first 3 units

Arunachal Pradesh is witnessing a critical delay in the commissioning of the Subansiri Lower Hydroelectric Project’s first three units, each with a capacity of 250 megawatts, as the National Hydroelectric Power Corporation (NHPC) continues to await clearance from the National Dam Safety Authority. The much-anticipated launch of commercial operations for these units, originally scheduled to begin by June 2025, has been put on hold due to pending approvals mandated by India’s Dam Safety Act. Despite technical readiness, the final nod from regulators remains the only barrier standing between the project and operational reality.

The Subansiri Lower Hydroelectric Project, or SLHP, is India’s largest under-construction hydroelectric initiative and one of the most strategically significant infrastructure projects in the Northeast. Situated near the Assam-Arunachal Pradesh border close to North Lakhimpur, the massive run-of-river scheme is designed to deliver a total of 2,000 megawatts of power once completed. It is being executed by NHPC under the Union Ministry of Power. With eight units of 250 megawatts each, the project aims to generate an estimated 7,421.59 million units of electricity annually in a 90 percent dependable year, reinforcing India’s renewable energy push.

According to a stock exchange filing made by NHPC on June 30, the company confirmed that despite its earlier intention to begin the commissioning process of the three completed units by June, it is still waiting for a formal go-ahead from the National Dam Safety Authority. The NDSA clearance is mandatory under the Dam Safety Act, 2021, which governs the structural and operational safety of large dams across the country. In its statement, NHPC said that further developments will be communicated in due course but made it clear that without this approval, commercial operations cannot proceed.

The remaining five units of the SLHP are currently under various stages of construction and are expected to be completed in phases by May 2026. Once all units are operational, the project is expected to significantly boost India’s non-fossil fuel energy mix, particularly in the Northeast where power deficits and transmission constraints remain persistent challenges. The project’s role is not just limited to generation, but also extends to grid balancing and storage support, especially crucial as India scales up its solar and wind capacities.

The delay in NDSA clearance, while procedural, is tied to heightened safety requirements due to the project’s sensitive geography. The SLHP is located in a high rainfall, high seismic zone where structural integrity and environmental sustainability are paramount. The dam is built on the Subansiri River, a major tributary of the Brahmaputra, and its location has raised concerns among environmentalists and local communities over potential downstream impacts, ecological disruption, and seismic vulnerability. Over the years, protests and public litigation had stalled the project multiple times, resulting in tighter regulatory scrutiny and environmental mandates.

The National Dam Safety Authority was constituted under the Dam Safety Act to act as India’s apex body for monitoring, evaluating and approving large dam projects. It is responsible for ensuring that dam design, construction and operation meet the strictest safety norms, especially in regions like Arunachal Pradesh and Assam. The Subansiri project, given its scale and location, is among the first large hydropower plants undergoing comprehensive review under this new framework. NHPC’s delay in obtaining the clearance is not due to any reported structural deficiency but is part of the newly institutionalized dam safety protocol that prioritizes risk assessment in vulnerable zones.

Originally envisioned in the early 2000s, the SLHP has suffered from nearly two decades of delays. What began as an ambitious push to tap the Northeast’s vast hydropower potential soon became mired in environmental clearances, local resistance, inter-state disputes, and seismic safety reviews. The project saw years of suspension and redesign. However, in recent years, with renewed central and state-level political backing and enhanced dam technology, construction resumed and gained momentum. The current delay, though frustrating for NHPC and policymakers, is seen as a necessary precaution in the wake of past oversights in dam safety and disaster preparedness across the country.

Strategically, the Subansiri project plays a vital role not just in terms of electricity generation but also in strengthening India’s regional infrastructure. The project has led to the creation of roads, transmission corridors and improved logistical networks in the surrounding areas. Once operational, it could provide surplus electricity to neighbouring states and even support cross-border energy trade with countries like Bhutan and Bangladesh, aligning with India’s larger neighbourhood energy diplomacy goals.

The economic footprint of the project has also been considerable. It has generated thousands of jobs during its construction phase and brought significant investments to remote districts of Arunachal Pradesh and Assam. Moreover, the spillover effects in terms of improved transport connectivity, local business development and civic amenities are expected to intensify once the plant becomes functional. NHPC has also undertaken multiple community engagement and resettlement initiatives to address local concerns, although some sections of the population still remain skeptical about long-term environmental impacts.

According to engineers close to the project, the three completed units have undergone successful internal testing and performance trials. What remains is the NDSA’s final inspection and clearance certificate, which will likely involve a thorough check of the dam’s emergency action plans, instrumentation, seismic design resilience, and flood-handling capacity. Experts believe that while the NDSA is taking its time, the certification process is ultimately beneficial in ensuring zero-compromise safety standards in an era of climate volatility and increasing hydrological unpredictability.

Despite the temporary regulatory setback, NHPC remains confident that the first phase of the Subansiri project will commence operations shortly after receiving the NDSA green light. The phased completion of the remaining five units by mid-2026 is also on track, according to the company’s project roadmap. In the larger scheme, SLHP continues to be a flagship energy initiative that combines clean energy generation with regional upliftment, grid reliability and long-term strategic value.

Arunachal Pradesh’s hydropower future, though currently paused at a bureaucratic checkpoint, is gearing up for a powerful restart. With the NDSA’s nod expected soon, the Subansiri dam may soon begin delivering on a promise it made over two decades ago — to power the Northeast, responsibly and sustainably.

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Arunachals Subansiri project awaits NDSA nod for commissioning of first 3 units
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