NHPC commenced commercial operations of the second unit (250 MW) of the 2,000 megawatt (MW) Subansiri Lower Hydroelectric Project (SLHEP) on Tuesday.
NHPC said that with the commissioning of Unit 2, the project is moving swiftly towards the commissioning of three more units of 250 MW each, followed by the phased commissioning of the remaining four units during 2026-27.
The SLHEP comprises eight units of 250 MW each and is designed as a run-of-the-river project with small pondage, diverting water through eight headrace tunnels to generate 7,422 million units of renewable electricity annually.
Apart from supplying electricity to 16 beneficiary states across India, the project will provide free power allocations to Arunachal Pradesh and Assam, while the Northeast region will receive 1,000 MW from the project.
The project features the largest dam in Northeast India, a 116-metre-high concrete gravity dam. It provides a dedicated flood cushion of 442 million cubic metres for safer management during the monsoon season, with a gross reservoir storage of 1,365 million cubic metres at full reservoir level.
Given its location in the seismically active and ecologically fragile Himalayan region, the Subansiri Lower Hydroelectric Project underscores the critical need for robust structural management, continuous surveillance, and advanced monitoring systems. Large dams in the Himalayas must be supported by real-time instrumentation and regular safety audits to track structural health, slope stability, and hydrological behaviour.
Equally important is comprehensive flood preparedness, as Himalayan rivers are prone to sudden surges, landslides, and extreme weather events. Past disasters in the region-triggered by dam failures, flash floods, and inadequate early warning systems-serve as ample warning and underscore the need to integrate disaster-risk reduction into project operations, strengthen downstream alert mechanisms, and ensure coordinated response plans with state authorities. In a region where seismic activity and changing climate patterns intersect, proactive risk management is the core of safety measures.