NHPC’s Subansiri Dam’s May-End target triggers concerns about downstream impact in Assam

File photos of NHPC’s 2,000 MW Subansiri project are being built in Arunachal Pradesh. |Photo source: Ritu Raj Konwar

The NHPC plan to start power from the 2000 MW lower Subansiri Hydropower Project (LSHP) has raised concerns about the downstream impact of Assam, especially since there has not been a set up independent reservoir management mandate recommended by the Ministry of Environment’s composition panel.

NHPC Chairman Management Director RK Chaudhary said in an interview on March 28 that LSHP’s reservoir will be filled by April, while three or four units (750 or 1,000 MW) of the hydroelectric plant will be commissioned by the end of May.

On the Subansiri River, the dam of the highly declared project spans the border between Arunachal Pradesh and Assam. Its reservoir has a surface area of ​​33.5 square kilometers. At normal levels, the total storage capacity is 1.37 cubic kilometers.

The goal may inspire all organizations such as the Assam Student Union (AASU) to take action. A few days ago, in a memorandum to Chief Minister Himanta Biswa Sarma, the alliance criticized the Centre for failing to meet its previous commitments and demanded a scientific and permanent solution to the downstream impact of large dams such as LSHP.

AASU is not specific, but hydrologists and environmentalists in Assam and beyond said these concerns are in line with the recommendations of the three-person expert committee on reservoir management in 2019 and a report (WII) submitted to the National Wildlife Research Institute (NBWL) about the possibility of elephants in the “panic pashir wall of pan pan ress of pan ress of pan ress of pan ress of pan ress of pan ress of pan ress” to the National Wildlife Commission (NBWL).

The committee said the centre should form the Subansiri independent Integrated Reservoir Authority (Siirma) or Subansiri River Basin Authority to monitor reservoir levels regularly and minimize downstream “hazards” during panic releases, especially during flooding. Other recommendations include running at least one unit continuously to ensure a minimum release of 240 cumec underwater and to ensure peak discharge release does not exacerbate the erosion of the Majuli Island of the downstream Brahmaputra River.

“The NHPC, the Centre, and the governments of Assam and Arunachal Pradesh accepted the 2019 recommendation from the panel that requires Siirma to be set up before filling the reservoir and debugging the LSHP,” said an ecologist.

“When all eight unit plans for the mega project are commissioned, Sirma cannot be postponed until 2026 because the reservoir needs to be managed by independent authorities regardless of how much power is generated,” he said.

The Expert Committee was formed by the Ministry of Environment by the 2017 order of the National Green Tribunal (NGT), which cleared the LSHP in 2019. This fast tracking work for the project began in 2005, but was suspended from 2011 to 2019 due to local protests.