Context:

• Recently, the Subansiri Lower Hydroelectric Project suffered a setback after a large part of the hill on the left side of the dam collapsed into its reservoir.

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• The deposit blocked the only working diversion tunnel, halting water flow downstream into the Subansiri River, a major Brahmaputra tributary.

About Subansiri Lower Hydroelectric Project

• It is an under-construction gravity dam located on the Arunachal Pradesh and Assam border.
  • Gravity dams are massive structure dams that are constructed of concrete or stone masonry.
• It has a total capacity of 2000 MW, consisting of 8 units, each with a capacity of 250 MW.
• This project is the largest hydroelectric venture ever undertaken in India.
• It is a run-of-river scheme.
  • Run-of-river hydro projects use the natural downward flow of rivers and microturbine generators to capture the kinetic energy carried by water. Typically water is taken from the river at a high point and diverted to a channel, pipeline, or pressurised pipeline (or penstock). 
• Implementing Agency: National Hydroelectric Power Corporation (NHPC) Limited.
• Construction History:
  • Construction commenced in 2005.
  • Multiple deadline extensions for commissioning of the project’s first two 250-MW units followed: March 2021, August 2022, March 2023, June 2023, and now March 2024.
• Beneficiary states:
  • Arunachal Pradesh has been allocated 274 MW of power from Subansiri Lower, out of which 240 MW is free power. 
  • Assam has been allocated with 533 MW power which includes 25 MW free power. 
  • All seven North-Eastern States and five northern States/UTs (Haryana, Punjab, Rajasthan, Uttar Pradesh, and Chandigarh) and five western States (Gujarat, Madhya Pradesh, Chhattisgarh, Maharashtra, and Goa) will be benefited from the power generated from this project.

Subansiri River

• Subansiri River, also known as the “Gold River,” is the largest tributary of the Upper Brahmaputra River.
• Originating from the Tibetan Himalayas, it flows into India through Arunachal Pradesh’s Miri Hills.

News Source: The Indian Express