---
title: "Subansiri River: Largest Brahmaputra Tributary"
description: "The Subansiri River, the largest tributary of the Brahmaputra, is vital for UPSC geography and the controversial Lower Subansiri dam project."
url: "https://modeldiplomat.com/learn/glossary/subansiri-river"
---

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Model Diplomat Research Team · Last reviewed June 22, 2026

TL;DR

- The Subansiri River is the largest tributary of the Brahmaputra, rising in Tibet and flowing through Arunachal Pradesh and Assam before joining the main river in India.
- Why is the Subansiri considered the largest tributary of the Brahmaputra?
- How does the Subansiri differ from the Siang?
- What makes the Lower Subansiri Hydroelectric Project controversial?
- What is meant by calling the Subansiri an antecedent river?

[Civil Service & Diplomatic Exams](https://modeldiplomat.com/learn/civil-services/glossary)Updated June 22, 2026

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In December 2011, the All Assam Students' Union blockaded construction of NHPC's 2,000 MW Lower Subansiri Hydroelectric Project at Gerukamukh, halting work for years over downstream flood and seismic-safety concerns.

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