The central government has cleared the Oju hydroelectric project in Arunachal Pradesh’s Upper Subansiri district, setting the stage for one of India’s largest hydropower ventures in a strategically sensitive Himalayan region bordering China.
The project, developed by Oju Subansiri Hydro Power Corporation Pvt. Ltd., aims to generate 2,220 megawatts through a run-of-the-river scheme with daily peaking capability. It involves a 100-metre-high concrete gravity dam, a 14.12 km headrace tunnel, and an underground powerhouse complex.
The estimated cost exceeds Rs 24,942 crore, with projected annual electricity generation of 8,402 million units, according to minutes of the Environment Ministry’s Expert Appraisal Committee (EAC) meeting held on September 12. The Oju project is the largest in a series of dams planned along the Subansiri River, long considered Assam’s lifeline.
Environmental and social concerns remain acute. The 750 hectares required are entirely forest land, and while only nine families are listed for displacement, nearly 98 per cent of the local tribal population may be affected. Residents at the public hearing in September 2024 raised issues over compensation, risks to fisheries, ecology, and sacred sites, and demanded a fair share of electricity for the local population.
The Oju project comes along with the Siang Multipurpose Dam, another major hydropower venture in Arunachal Pradesh. While Oju focuses on run-of-the-river power generation with a capacity of 2,220 MW, the Siang Dam is a multipurpose project designed not only for hydropower, estimated at around 10,000 MW, but also for flood control and irrigation
Also read: Arunachal villagers drop resistance, sign on to Siang dam project
Ecologists have cautioned that large Himalayan dams could destabilise slopes, alter riverine ecology, and threaten biodiversity. The Subansiri basin lies in seismic zone V, the highest risk category. The EAC deliberated on glacial lake outburst floods (GLOFs) and directed the developer to include GLOF scenarios in design estimates, establish a real-time early warning system, and conduct community preparedness drills. A post-commissioning environmental impact study after five years has also been mandated.
While no national parks or wildlife sanctuaries fall within 10 km of the site, 43.66 hectares of riverine forest will be submerged and flows altered over 18.6 km. Construction will generate 17 lakh cubic metres of muck, with 93 hectares earmarked for disposal. The proponent said compensatory afforestation over 1,500 hectares and e-flow releases above recommended levels would safeguard river ecology.
The project is expected to create 1,500 jobs during construction and 300 permanent positions, with ancillary development in townships stimulating trade in the remote district. Environmental groups and student bodies in Assam and Arunachal Pradesh have consistently opposed large Subansiri dams, citing downstream flooding and ecological risks.
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