File picture of the Lower Subansiri dam site

Guwahati, Dec. 17: The Union ministry of environment and forest has asked the Central Water Commission (CWC) to point out the area for studying the downstream impact of dams coming up in Arunachal Pradesh.

Under the present norms, the study is conducted in a 10km radius but this is considered too small an area for studying the impact of big projects.

Assam has been voicing concern over the downstream impact of dams coming up in Arunachal Pradesh. Chief minister Tarun Gogoi had written to Prime Minister Manmohan Singh to facilitate a cumulative study of the impact, following which the expert appraisal committee for river valley and hydroelectric projects under the ministry of environment and forest asked the CWC to suggest the area for the study.

The ministry has asked the CWC to point out the downstream impact study area for Subansiri and Siang basins and submit its report in two phases. In the first phase, a rapid assessment based on available secondary data, which may be completed in four to six months, should be submitted, and the final report is to be a detailed one.

Jaypee Group, which is executing the 2,700MW Lower Siang hydroelectric project, had requested the ministry to drop the Dibru-Saikhowa National Park in Assam’s Tinsukia district and Jamjing and Sengajan reserve forest in Dhemaji district — both of which are located downstream of the confluence of the Siang and the Brahmaputra — from the purview of the study, saying that these were very far from the dam site.

The ministry, however, asked the Jaypee Group to include the Dibru-Saikhowa National Park for the study, saying it was only 55km from the site of the dam, located near Bodak, 23km from Pasighat, the headquarters of East Siang district of Arunachal Pradesh.

But it excluded Jamjing and Sengajan reserve forest from the study, saying they were located 100km downstream and would not have a significant impact.

“For many developers, the downstream issue is a new one and there is no unanimity on what can be the limit of downstream impact,” a source said.

The NHPC has already said this is its first experience with downstream impact and it is taking the best possible steps.

Organisations like the Krishak Mukti Sangram Samiti in Assam are demanding that the Centre withdraw the clearances granted to the 2,000MW Lower Subansiri, the 1,750MW Demwe Lower and the 1,500MW Tipaimukh projects without downstream impact assessment and public consent.

The CWC has also been asked to find out how many more hydroelectric projects may be allowed to come up so that the integrity of the rivers is not grossly undermined.

The study for Subansiri and Siang basins will look into floodplains, including wetlands, aquatic ecology, river morphology, the transport, erosion and deposition of sediment and the impact of the projects on human activities and livelihood.