Brahmaputra river

Also called: Jamuna, Brahmaputra, Siang · Topic: Drainage System of India: Rivers, Basins and Patterns · NCERT: Class 7, Ch 1 "Geographical Diversity of India"; Class 8, Ch 1 "Natural Resources and Their Use"; Class 11, Ch 2 "Structure and Physiography"; Class 11, Ch 3 "Drainage System"; Class 11, Ch 6 "Natural Hazards and Disasters: Causes, Consequences and Management"

Meaning

The Brahmaputra ("son of Brahma") is one of the world's largest rivers. It is about 2,900 km long and flows through Tibet (China), India and Bangladesh [2]. It rises in the Chemayungdung glacier of the Kailash range near Lake Mansarovar. It is called the Yarlung Tsangpo in Tibet, the Siang/Dihang in Arunachal Pradesh, the Brahmaputra in Assam and the Jamuna in Bangladesh. It then joins the Padma and reaches the Bay of Bengal.

It matters because it holds a large share of India's hydropower. It also brings yearly floods and bank erosion to Assam. China's dam on its upper course makes it a live India–China water issue.

Explanation

Origin: one of three Himalayan systems

• Indo-Brahma hypothesis: the idea that one huge river once flowed along the whole Himalaya.
• It was called the Indo-Brahma or Shiwalik river. It ran from Assam in the east to Punjab in the west.
• The western Himalaya and the Potwar Plateau (Delhi Ridge region) were pushed up. This split the river into separate systems.

• The result was today's Indus, Ganga and Brahmaputra.

• The Brahmaputra is perennial, which means it flows all year round.

• In summer, snow and glaciers in Tibet and the Himalaya melt.
• In June–September, the south-west monsoon brings very heavy rain over Arunachal, Assam and Meghalaya.
• The melt peak and the rain peak come at the same time, so the river swells hugely in summer.

The course and its changing names

• Source: the Chemayungdung glacier, at about 5,150 m [2], in south-west Tibet (about 30–31°N).
• Tibet (Yarlung Tsangpo):
• "Tsangpo" means "the purifier".
• It flows east for about 1,200 km, parallel to the Himalaya.
• It crosses dry, flat southern Tibet. This is a rain-shadow area: the Himalaya block the monsoon winds, so little rain falls there.

• Its main right-bank tributary here is the Rango Tsangpo.

• The Great Bend:

• Near Namcha Barwa (7,755 m), the eastern anchor of the Himalaya, the calm river becomes turbulent (fast and rough).
• It makes a sharp U-turn around the peak, close to Medog, and cuts a very deep gorge.

• Why it can cut the gorge: the river is older than the rising ranges and keeps its old path. It also drops steeply from the Tibetan Plateau, so it has great power to cut down into the rock.

• Arunachal Pradesh (Siang/Dihang):

• The river flows south through the gorge and comes out of the foothills into the plains near Sadiya.
• Two left-bank tributaries join it here: the Dibang (Sikang) and the Lohit.

• From this meeting point onwards, the river is called the Brahmaputra.

• Assam (about 750 km):

• It flows south-west and then west through a long, narrow valley.

• The Himalaya lie to the north and the Meghalaya plateau to the south.

• Bangladesh:

• It enters Bangladesh near Dhubri (Assam) and turns south.
• The Tista joins it on the right bank. After this it is called the Jamuna.
• The Jamuna merges with the Padma (the Ganga's name in Bangladesh), and the joined river flows into the Bay of Bengal.

Stretch	Name	Direction
Tibet, from the source to the Great Bend	Tsangpo / Yarlung Tsangpo	East
Arunachal foothills	Siang / Dihang	South, through the gorge
After the Dibang and Lohit join, through Assam	Brahmaputra	South-west, then west
Bangladesh, after the Tista joins	Jamuna	South
After meeting the Padma	Padma	To the Bay of Bengal

Tributaries

Bank	Tributaries	Where they come from
Left (south) bank	Dibang, Lohit (Arunachal); Burhi Dihing, Dhansari (South) (Assam)	Arunachal hills; Patkai–Naga hills
Right (north) bank	Rango Tsangpo (Tibet); Subansiri, Kameng, Manas, Sankosh; Tista (in Bangladesh)	Himalaya (Tibet, Arunachal, Bhutan, Sikkim)

• The CWC (Central Water Commission) names the Dibang, Lohit, Subansiri, Manas, Tista, Dhansiri and Champamati as the main tributaries inside India [2].
• Subansiri is an antecedent river: a river that was there before the mountains rose.
• As the land was slowly pushed up, the river kept cutting down, so it kept its old path.
• It rises in Tibet and joins the Brahmaputra from the right bank.

Floods, braiding and bank erosion

• Why it floods:
• It has many large tributaries.
• Its catchment is very wet, among the rainiest places on Earth.

• The young Himalayan slopes are steep and loose, so the river carries a very heavy load of silt.

• What happens on the Assam plain:

• The slope becomes gentle, so the river slows down and drops its silt on its own bed. The bed rises.
• The river splits into many channels around sandbars. This is a braided channel.

• The channels keep moving. This is channel shifting.

• Result:

• The raised bed holds less water, so the river spills over its banks and floods.
• The moving channels eat into the banks. This bank erosion destroys farmland and villages in Assam.
• Riverine islands such as Majuli form in this setting.

Where it occurs

• Countries: the river flows through Tibet (China), India and Bangladesh. Its basin (all the land that drains into it) covers about 5,80,000 sq km across Tibet, Bhutan, India and Bangladesh [2].
• Basin inside India: 1,94,413 sq km, about 5.9% of India's area [2].

State	Drainage area (sq km) [2]
Arunachal Pradesh	81,424 (largest)
Assam	70,634
West Bengal	12,585
Meghalaya	11,667
Nagaland	10,803
Sikkim	7,300

• Key places along the river: Chemayungdung glacier and Mansarovar (Tibet) → Namcha Barwa and Medog (the Great Bend) → Sadiya (where the Dibang and Lohit join) → the Assam valley and Majuli → Dhubri (exit to Bangladesh).
• Hydropower potential: 31,012 MW at 60% load factor, about 37% of India's total hydropower potential [2]. Load factor is how much of the year a plant actually runs at full output.
• Monitoring: the CWC runs 137 gauge-discharge sites (which measure water level and the amount of flow) and 28 flood-forecasting stations in the sub-basin [2].
• Subansiri Lower Hydroelectric Project:
• It is on the Subansiri, on the Arunachal Pradesh–Assam border. It is 2,000 MW (8 units of 250 MW each) and is built by NHPC Limited [3].
• It is described as the country's largest hydropower project [4]. Unit-2 (250 MW) started commercial operation on 23 December 2025 [4].
• 2 of the 8 units are running. The rest are planned in phases until December 2026, and it is expected to give about 7,422 million units a year [3].

• It also aims at flood moderation (lowering flood peaks by holding back water), grid stability and peaking power (extra power when demand is highest) [3].

• Trans-border dams:

• China approved a mega dam on the lower Yarlung Tsangpo, which is the upper Brahmaputra [5]. It is near the Great Bend (Medog), about 60 GW in size, and construction began in July 2025.
• India's planned counter is the Siang Upper Multipurpose Project (about 11,000 MW) in Arunachal Pradesh. "Multipurpose" means it serves power, water storage and flood control. The Upper Siang Project appears in official lists at the pre-feasibility and project-development stage [6].

Don't confuse with

• Jamuna (Bangladesh) vs Yamuna (India): the Jamuna is the Brahmaputra's name in Bangladesh, after the Tista joins. The Yamuna is a tributary of the Ganga in north India.
• Siang vs Subansiri: the Siang/Dihang is the main stream of the Brahmaputra in Arunachal. The Subansiri is a separate right-bank tributary (and an antecedent river) that joins it in Assam.
• Left-bank vs right-bank tributaries: the Dibang, Lohit, Burhi Dihing and Dhansari (South) join from the left. The Subansiri, Kameng, Manas, Sankosh and Tista join from the right.
• Padma vs Jamuna: the Padma is the Ganga in Bangladesh. The Jamuna is the Brahmaputra in Bangladesh. They merge, and the joined flow reaches the Bay of Bengal.

Prelims Hooks

• Source: Chemayungdung glacier, Kailash range, near Mansarovar, at about 5,150 m [2].
• Names from source to sea: Tsangpo/Yarlung Tsangpo → Siang/Dihang → Brahmaputra (after the Dibang and Lohit join, near Sadiya) → Jamuna (after the Tista joins) → Padma → Bay of Bengal.
• Gorge: the river cuts a deep gorge round Namcha Barwa (7,755 m) at the Great Bend, near Medog.
• Trap: the Rango Tsangpo is a right-bank tributary in Tibet. The Dibang (Sikang) and Lohit are left-bank tributaries in Arunachal.
• Subansiri Lower HEP: 2,000 MW (8 × 250 MW), built by NHPC, on the Arunachal–Assam border [3].
• Largest share of the Indian basin: Arunachal Pradesh (81,424 sq km), then Assam (70,634 sq km). The basin holds about 37% of India's hydropower potential [2].

Mains Points

• Flood–erosion cycle in Assam (GS-I/GS-III):
• A very wet catchment and heavy silt from young mountains raise the river bed.
• This causes braiding, channel shifting, yearly floods and bank erosion that wipe out farmland and villages.

• Responses include flood forecasting (28 CWC stations [2]), flood moderation by storage dams like Subansiri Lower [3], and bank protection.

• Trans-border water security (GS-II/GS-III):

• China's ~60 GW Medog dam lets an upstream country control when the water flows. It could cut dry-season flow, and a sudden release or dam failure could flood Arunachal and Assam in an earthquake-prone zone.
• India raised its concerns with China on 30 December 2024 and asked for transparency. It raised them again at the Foreign Secretary–Vice Foreign Minister meeting in Beijing on 26–27 January 2025. Both sides agreed to an early Expert Level Mechanism meeting on restarting the sharing of hydrological data [5].

• The Siang Upper reservoir would act as a buffer, but it faces local opposition, mainly from the Adi community, over flooding of land.

• Hydropower and North-East development vs people and ecology:

• The 31,012 MW potential [2] can give clean energy and peaking power.
• This has to be weighed against tribal displacement, earthquake risk and harm to river ecology.
• Downstream, the unsettled Tista water-sharing issue shows how use upstream (Sikkim, north Bengal) cuts dry-season flow in Bangladesh.

Related concepts

• Yarlung Tsangpo
• Siang river
• Subansiri river
• Tista river

Read more

• The Brahmaputra system