Concerns Linger Over Risks of Building Mega-Dams in India's Far Northeast
Concerns are growing in India over the environmental and seismic risks of building huge dams in the country's northeast region. Opponents have focused attention on the 2,000-MW Lower Subansiri Dam on the border of the Assam and Arunachal Pradesh states; if built as planned, the dam would be the country's largest hydroelectric project.
Opposing groups, who claim the megaproject could alter river flow or cause earthquake-inducing ground stresses, are seeking a two-year halt in construction while a new study of impacts is done. But earlier this month, government officials said work would continue despite the protests, according to published reports in India.
Officials of India's state-owned National Hydroelectric Power Corp. (NHPC) say that $2.9 billion has been spent on the project, which is now at 45% completion. It is set to begin operation in 2014.
India has announced plans for more than 160 dams, with 40,000 MW of total estimated installed capacity, along the 2,900-kilometer-long Brahmaputra River. It flows from southwestern Tibet into Arunachal Pradesh and Assam and south through neighboring Bangladesh.
When completed, the concrete-gravity Lower Subansiri Dam is designed to be 210 meters high and 284 m long, with a reservoir of 1.37 cu km in storage capacity. It is under construction for NHPC by Indian contractors, including Larsen & Toubro Ltd. and Soma.
Protesting groups claim the dam could result in severe fluctuations in water flow, a likely increase in sand deposits over presently cultivable land and destruction of aquatic life, which will affect the region's fishing industry, among other impacts.
Dr. H.R. Wason, who heads the department of earthquake engineering at the Indian Institute of Technology in Roorkee, told ENR that further study is needed of the project's seismic risks, particularly stress on existing fault lines caused by the project reservoir.
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"Reservoir water may increase the stress on the causative faults and reduce the strength of the material in the fault, thereby causing earthquakes," says Wason. "Without the reservoir, the same earthquake would have happened in a far future time."
But others disagree. "In a highly seismic region, it is almost impossible to say whether an earthquake is reservoir-induced or not," says Sarada Kanta Sarma, an engineering seismology professor at the Imperial College of London. "Even without the reservoir, such an earthquake would have happened."
India’s hurry to build dams in Arunachal Pradesh may stem from speculation the Chinese government is planning to divert the Brahmaputra River water to the parched regions of northern China, according to a recent article by one Indian think tank, the Institute for Defense Studies and Analyses.
