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A file image of Subansiri Lower Hydroelectric Project (SLHEP). (AT Photo)

Guwahati, May 9: The fourth unit (250 MW) of the NHPC’s Subansiri Lower Hydroelectric Project (SLHEP), which has a total capacity of 2,000 MW (8x250 MW), commenced commercial operations on Friday.

With this new unit operational, the project has now reached a total capacity of 1,000 MW, marking a significant achievement in its phased rollout.

Officials indicated that the remaining units are on track to be commissioned as scheduled.

According to a statement from NHPC, the unit began operations at midnight on May 8, 2026, contributing an additional 250 MW of renewable energy to the national grid.

Construction of the project began in January 2005 after obtaining forest clearance in October 2004. However, work was halted from December 2011 to October 2019 due to protests in Assam regarding safety and potential downstream effects.

After resolving all legal issues raised by the National Green Tribunal (NGT), NHPC resumed construction with some design changes starting on October 15, 2019.

The project was initially slated for completion by December 2012, but costs have surged from an estimated Rs 6,285 crore in December 2002 to approximately Rs 27,000 crore upon completion.

AN Mohammed, a consultant for SLHEP at NHPC, stated that the project has been developed in compliance with statutory regulations and government guidelines, prioritizing environmental protection, safety, and socioeconomic benefits.

Since its inception, the project has undergone extensive scientific evaluations and regulatory reviews by independent expert committees to address environmental, geological, and social issues linked to large infrastructure projects in the Subansiri-Brahmaputra river system.

Considering the region's seismic history, hydrological features, and ecological sensitivity, the project design includes strong safety measures, sediment management strategies, and year-round environmental flow releases to sustain downstream river ecology. Flood management strategies have also been incorporated to enhance safety during monsoon seasons and improve basin resilience.

Mohammed emphasized that the project's social impact has been minimized, with no habitations being submerged and limited agricultural land affected, which is being managed through rehabilitation and compensation in line with the Arunachal Pradesh Rehabilitation and Resettlement Policy.

Compensatory afforestation is being carried out over a significantly larger area of degraded forest land in Arunachal Pradesh and Assam using CAMPA funds. To protect downstream areas, riverbank stabilization works, real-time flood forecasting, and early-warning systems have been established. Advanced monitoring and control systems support project operations to ensure safe and regulated functioning.

Upon the launch of the fourth unit, NHPC CMD Bhupender Gupta expressed appreciation to the Union Ministry of Power and the state governments of Arunachal Pradesh and Assam for their support, as well as to the SLHEP team and various NHPC departments.

Gupta noted that the successful commissioning underscores NHPC’s technical expertise and project management capabilities, reinforcing its crucial role in enhancing India’s energy security in alignment with the Government of India’s vision for a sustainable and self-sufficient power sector.

Beyond power generation, significant investments have been made in community development initiatives, including livelihood support, education, healthcare, drinking water access, skill development, and other socioeconomic programs in areas affected by the project and nearby regions of Arunachal Pradesh and Assam. The power generated is shared equitably, providing free power benefits to host states and improving clean energy availability for the broader region.