The Central Government has granted environmental clearance to the Oju hydroelectric project in Arunachal Pradesh's Upper Subansiri district, paving the way for the construction of one of India's largest hydropowerventures in a geologically sensitive and strategically important region bordering China.
The project, to be developed by Oju Subansiri Hydro Power Corporation Pvt. Ltd., envisages generating 2,220 megawatts of electricity 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.
With an estimated cost of over `24,942 crore, the dam is expected to produce 8,402 million units of electricity annually, according to the minutes of the meeting of the environment ministry's Expert Appraisal Committee held on September 12.
The Oju project is the largest in a series of dams proposed on the Subansiri River, often described as the lifeline of Assam, and has been in the pipeline for nearly two decades.
It has stirred concerns over its social and environmental consequences.
The entire 750 hectares required for the project is forest land, and though only nine families are listed for displacement, the impact on local tribal communities, who constitute nearly 98 per cent of the population in the area, is expected to be significant.
The public hearing held in September 2024 saw residents flag issues ranging from inadequate compensation to risks for fisheries, ecology, and sacred sites.
Many demanded that a fair share of the electricity generated be provided to the local population, according to the minutes of the meeting.
The public hearing also reflected mistrust over whether corporate social responsibility funds would actually reach local schools and health facilities.
Ecologists have warned that large dams in the fragile Himalayan ecosystem could destabilise slopes, alter riverine ecology and endanger biodiversity.
The Subansiri basin falls in seismic zone V, the most vulnerable category.
Studies by the South Asia Network on Dams, Rivers and People (SANDRP) have in the past highlighted repeated monsoon damages at hydropower projects in the region, including the Subansiri Lower project downstream, calling them "ticking water bombs" for Assam.
The EAC itself deliberated extensively on the risks of glacial lake outburst floods (GLOFs), noting that potential peak discharges from upstream glacial lakes could overwhelm dam structures.
It directed the developer to include GLOF scenarios in the design flood estimates, establish a real-time early warning system and conduct community preparedness drills.
The committee has also mandated a post-commissioning environmental impact study after five years.
While there are no national parks or wildlife sanctuaries within 10 km of the project site, the dam will submerge 43.66 hectares of riverine forest and alter flows over an 18.6 km stretch.
Nearly 17 lakh cubic metres of muck will be generated during construction, for which disposal sites covering 93 hectares have been identified.
The project proponent claimed that mitigation measures such as compensatory afforestation on 1,500 hectares and e-flow releases higher than those recommended in cumulative impact studies will protect river ecology.
About 1,500 jobs are expected during construction, with 300 permanent posts. The project proponent says the influx of workers and development of townships will stimulate trade and allied activities in the remote district.
Environmental groups and student bodies in Assam and Arunachal Pradesh have consistently campaigned against large dams on the Subansiri, warning of downstream flooding and ecological collapse.
