Reduce Subansiri dam height: panel

Will National Hydro Power Corporation heed report?

By Bharat Lal Seth
Published: Saturday 31 July 2010

imageAN EIGHT-MEMBER expert committee has recommended a thorough review and redesign of the 115-metre high dam on the Subansiri river, a tributary of the Brahmaputra.

The National Hydro Power Corporation (NHPC) is developing the 2,000 MW Lower Subansiri Hydro Power project in Dhemaji district of Assam.

In its final report submitted on June 29 to NHPC, the committee expressed reservations over the dam, saying it could adversely impact downstream areas. The report revealed inadequacies in the dam’s design. The spillway for releasing floodwaters has been designed incorrectly, it said. The spillway is designed for a maximum discharge of 12,024 cumec, whereas the maximum discharge recorded on July 11, 1971, was more than 21,230 cumec.

“Clearly the dam has not been designed for the highest discharge,” said Chandan Mahanta of IIT Guwahati, a panel member. This can spell disaster for downstream areas, he added. The panel recommended reducing dam height and power generation capacity to minimize its adverse economic and environmental impacts.

If the present design parameters are followed, the dam will impact biodiversity and lead to siltation. To deal with this, the report recommended a minimum flow of 320 cumec and a minimum depth of three metres in the dolphin habitat stretches of the river. To minimise dam-induced flash floods, the report has recommended flood cushioning in the reservoir.

The Assam government had set up the expert committee in December 2006. It comprised members from IIT Guwahati, Dibrugarh University and Gauhati University, and was asked to study the downstream impact of the dam project. The project is 40 per cent complete.

The report sparked protests. Environmentalist groups and the All Assam Students Union demanded immediate stoppage of work. They believe even after redesigning, the dam will create environmental and socioeconomic problems. They are planning protests in Dispur.

Officials at the NHPC headquarters in Faridabad, near Delhi, said they were yet to receive the report. “When it arrives we will look into all the concerns and the remedial measures suggested by the committee,” said a senior official. Earlier this year, Union Power Minister Sushil Kumar Shinde had assured activists that the Subansiri dam project would be reviewed on the basis of the final report.

“My feeling is that either the committee will compromise the report or it will simply be discarded since more than Rs 500 crore has already been spent,” said Ravindra Nath, founder member of River Basin Friends, a campaign front in Assam.

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