The Great Bend: Upper Siang

Upper Siang is designed around a 296m-high concrete gravity dam — set to be the tallest in India — creating a 1,000 sq km reservoir at 11,000 MW (11 GW) of capacity, nearly four times the size of India's current largest hydro project, Dibang.

At an estimated annual generation of 53 billion units, the project would contribute 7.1% of India's total generation as of 2026.

Sited at the entry point of the Brahmaputra — known as the Siang as it crosses into India — the dam is central to maintaining historical water-flow rights under international law.

Its design prioritizes a large live-storage capacity specifically to neutralize flood risk and potential water scarcity created by upstream cascading dams, and it is integrated with the expanded Vibrant Villages Programme.

The project is estimated to reduce power costs in Arunachal Pradesh by 20%, and is integrated with a ₹2,205 crore Vibrant Villages Programme–linked roads network turning the Siang region into a logistics and eco-tourism corridor.

It is expected to stabilize population in three border districts, expanding the state's economic base in the process.

Upper Siang contributes 8.2% toward India's 2035 target of 350 GW of hydro capacity. Project expenditure is expected to contribute as much as 1.8% annually to Arunachal Pradesh's GSDP during peak construction, from 2029 to 2032.

A ₹1,200 crore compensatory afforestation and catch-basin management plan is being executed in parallel with construction.