📌 Topic 04 of 6 · Chapter 02 · Drainage Systems
Brahmaputra River System
Tsangpo (Tibet) → Dihang (Arunachal) → Brahmaputra (Assam); deepest gorge, Majuli island, floods — complete notes for UPSC & PSC exams.
🌊 Brahmaputra River — Key Facts
| Parameter | Details |
|---|---|
| Origin | Chemayungdung glacier (Tibet, China); near Mansarovar Lake |
| Name in Tibet | Tsangpo (flows eastward across Tibet) |
| Name in Arunachal Pradesh | Dihang (after crossing the Himalayas) |
| Name in Assam | Brahmaputra |
| Name in Bangladesh | Jamuna |
| Total Length | ~2,900 km (916 km in India) |
| Drains into | Bay of Bengal (joins Ganga in Bangladesh → Meghna → Bay of Bengal) |
| Direction | Flows east in Tibet → sharp U-turn → flows west in Assam |
⭐ The Dihang Gorge — World’s Deepest Gorge:
When the Tsangpo makes its sharp U-turn around Namcha Barwa peak (7,782m), it cuts through the Himalayas forming the Dihang gorge — approximately 5,500 metres deep — the deepest gorge in the world. The river drops about 3,000 metres in just 160 km.
When the Tsangpo makes its sharp U-turn around Namcha Barwa peak (7,782m), it cuts through the Himalayas forming the Dihang gorge — approximately 5,500 metres deep — the deepest gorge in the world. The river drops about 3,000 metres in just 160 km.
🌊 Tributaries of the Brahmaputra
| Tributary | Bank | Key Facts |
|---|---|---|
| Dibang | Left bank | Arunachal Pradesh; joins near Sadiya |
| Lohit | Left bank | Arunachal Pradesh; joins near Sadiya; forms the Brahmaputra proper |
| Subansiri | Left bank | Tibet/Arunachal; “Gold River”; largest tributary |
| Manas | Right bank | Bhutan; Manas Tiger Reserve; joins near Barpeta |
| Teesta | Right bank | Sikkim/WB; Teesta water dispute (India-Bangladesh) |
| Sankosh | Right bank | Bhutan; forms boundary between Assam and WB |
🏝️ Majuli Island
- World’s largest river island — located in the Brahmaputra river, Assam
- Area: ~875 sq km (shrinking due to erosion)
- Famous for Vaishnavite monasteries (Satras) — cultural heritage
- Became India’s first island district in 2016
- Threatened by annual floods and erosion — area has reduced significantly
🌊 Brahmaputra Floods
- Brahmaputra causes annual devastating floods in Assam
- Reasons: heavy rainfall in catchment area, flat valley, high sediment load, narrow valley
- The river is braided (multiple channels) in Assam — very wide and shallow
- Kaziranga National Park (one-horned rhino) is flooded annually
- China’s dam construction on Tsangpo is a concern for India
🌊 Mahanadi River System
| Parameter | Details |
|---|---|
| Origin | Sihawa hills, Raipur district, Chhattisgarh |
| Length | 858 km |
| Drains into | Bay of Bengal (Odisha) |
| Major dam | Hirakud dam (Sambalpur, Odisha) = longest dam in India (~4.8 km) |
| States | Chhattisgarh, Odisha |
| Tributaries | Seonath, Jonk, Hasdeo, Ib, Ong, Tel |
📌 Hirakud Dam Facts:
• Longest dam in India = ~4.8 km (main dam) + 21 km (earthen dykes) = total ~56 km
• Built on Mahanadi river at Sambalpur, Odisha
• Completed in 1957 — one of India’s first major multipurpose projects
• Creates Hirakud reservoir — one of the largest artificial lakes in Asia
• Longest dam in India = ~4.8 km (main dam) + 21 km (earthen dykes) = total ~56 km
• Built on Mahanadi river at Sambalpur, Odisha
• Completed in 1957 — one of India’s first major multipurpose projects
• Creates Hirakud reservoir — one of the largest artificial lakes in Asia