Upper Siang Hydroelectric Project
The Upper Siang Hydroelectric Project, also known as the Upper Siang Multipurpose Project or Siang Upper Multipurpose Project is the biggest hydroelectric power project planned in the Upper Siang district of Arunachal Pradesh, India. Projects planning was commenced by the National Hydroelectric Power Corporation in April 2009 and various hydro dams will be constructed in phases over a span of 15–20 years.
The main dam is being constructed across the Siang river and upon completion, the dam reservoir will hold 9 billion cubic meters of water. The hydro power project at Siang will alone generate approximately 11,000 MW, making it the largest hydroelectric dam in the Indian subcontinent.
Concerns
Floods
In 2006, Indian media reported that the NHPC was planning to relocate and scale down the project due to concerns on flooding upstream by Chinese government. However, the situation has reversed due to construction of many tall dams/massive storage reservoirs in the river basin area effecting river's natural flow regime in downstream India.In 2025, NHPC is conducting pre-feasibility studies for site selection. The height of the dam is nearly 300 meters above the river bed level at dam location to store water up to 750 m MSL. The back waters of the reservoir would touch the foot of the Medog Hydropower Station being constructed on the upstream river in Tibet/China so that adequate flood buffer is maintained to safely discharge the peak floods arising out of upstream dam failures due to earthquakes, Glacial Lake Outburst Floods and massive land slides. This reservoir acts as a regulating basin to release the continuous flows downstream according to the river flow regime when the water released from the upstream mega power station in China is regulated or intermittent as per the needs of power generation on daily and weekly basis.
The state government of Arunachal Pradesh signed deals with various Indian power companies to develop hydro projects. A total of 42 schemes are planned to generate electricity in excess of 27,000 MW with the Upper Siang project being one of them.