Brahmaputra river: origin, course, tributaries and floods

Origin: Yarlung Tsangpo in Tibet

The river rises on the northern side of the Himalayas near Mount Kailash and Lake Manasarovar in Tibet, where it is called the Yarlung Tsangpo. Older sources name the Chemayungdung glacier as its source, while more recent accounts point to the Angsi Glacier; both lie in the same high region near Kailash, and exam answers usually accept the Manasarovar-Kailash region as the source area.

From there it runs east for roughly 1,100 km along southern Tibet, between the main Himalayan range and the Kailas Range, picking up tributaries such as the Lhasa river, which flows past the Tibetan capital. Its total length is commonly given as about 2,900 km, though some sources give 2,880 km and others over 3,000 km, since the measured length depends on where the source and the end of the channel are placed.

The great bend and entry into India

Near the eastern end of the Himalayas the river swings sharply around the Namcha Barwa massif, cutting the Yarlung Tsangpo Grand Canyon, whose walls rise more than 5,000 metres on either side. This great bend turns the river south, and it enters India near Gelling in Arunachal Pradesh, where it is known as the Siang or Dihang.

Flowing south for a short distance, it is joined by the Dibang and Lohit at the head of the Assam valley, and from that meeting point it is conventionally called the Brahmaputra, a Sanskrit name meaning 'son of Brahma'. The river is unusual among major Indian rivers in carrying a masculine name.

Through Assam: a wide, braided river

Across its roughly 700 km course through the Assam valley, the Brahmaputra spreads into many shifting channels separated by sandbars, the classic braided pattern. In places it is up to 20 km wide, while at Guwahati, where it cuts through the Shillong Plateau, it narrows to about 1 km, the site of the historic Battle of Saraighat in 1671.

Between Dibrugarh and Lakhimpur districts the river splits into two channels that rejoin downstream, forming Majuli island, the world's largest river island. Its Assam tributaries include the Subansiri, Kameng, Manas and Sankosh from the north, and the Burhi Dihing, Dhansiri and Kopili from the south.

Bangladesh, the delta and floods

The river enters Bangladesh near Dhubri and, after being joined by the Teesta, is called the Jamuna, not to be confused with India's Yamuna. Near Goalundo Ghat it merges with the Padma, the Ganga's name in Bangladesh, and the combined waters join the Meghna before reaching the Bay of Bengal, building the vast Ganga-Brahmaputra delta.

The Brahmaputra is prone to severe flooding and bank erosion because its Himalayan tributaries bring enormous sediment loads during the monsoon, and its channels shift course frequently. At the same time it is a lifeline for irrigation, transport and fisheries, and its basin holds a large share of India's water and hydropower potential, which is why upstream dam projects in Tibet are closely watched in India.

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