Brahmaputra River

One of the biggest and most important rivers of Asia, Brahmaputra River flows through three countries- China, India, and Bangladesh. This trans-boundary river is also known as Tsangpo-Brahmaputra River. Originating near the Mount Kailash range of the Himalayas, it travels a total of close to 2,900 km from its origin in the Himalayan folds to the Bay of Bengal, where it empties itself after merging into the Ganges delta.

Brahmaputra River is world’s fourth largest river in terms of discharge at the opening and is second only to China’s Yellow River in terms of sediment that is transported per unit area of drainage. An approximate of 5, 80,000 km is the total international area drained by the river. It is a very important means of irrigation, as well as transportation. Most of the length of the river is suitable for navigation.

The river has a gradient of 0.09 to 0.17 m/km around Dibrugarh in Assam at the head of the Valley, which is reduced to about 0.1 m/km around Guwahati in the same state. The width of the river is inconsistent, varying from one km on an individual channel to as much as 10 km in certain reaches that have multiple braided channels. It has three to six channels, divided by islands and mid-channel bars under low flow conditions, almost through all of its length in Assam.

124 feet is the average depth of the river, reaching a maximum depth of 380 feet. Flooding is a common drawback of the river that is otherwise the lifeline of Assam. Major flooding happens mostly at the time of spring when the snow caps melt in the Himalayas, causing huge losses to life, crops, property, et al. 19,300 cubic metres per second is the average discharge of the river, which can reach up to 100,000 cubic metres per second during floods. The pattern of channels too changes repeatedly under flood conditions.

Brahmaputra River has great religious significance, with its name translating to ‘son of Brahma’. Brahma is considered the creator of the universe, as per beliefs of the Hindu mythology.

Course

Brahmaputra River finds its origin from an enormous glacial mass in the northern part of the mountain range of the Himalayas, at an elevation of 5,300 m. From there, it flows through the Tibet Autonomous Region in China as the Yarlung Tsangpo River. It flows through South Tibet to split into big gorges through the Himalayas. It enters India through Arunachal Pradesh, where it is known as the Siang or Dihang River.

It is joined by other tributaries to form the Brahmaputra River in Assam, where it flows south west. It turns south near the western boundary of Assam to enter Bangladesh. It is called the Jamuna River in Bangladesh. It then merges into the Ganges delta with Padma, a major distributary of the Ganges, and finally empties into the Bay of Bengal.

The Brahmaputra valley in Assam is underlain by recent alluvium which is approximately 200-300 m thick. It consists of clay, silt, sand and gravels. The current configuration of the Brahmaputra valley in Assam is known to have evolved during 2 million years of Pleistocene and recent era.

The southern-central part of the Tibetan plateau above the Ganges basin, the south-eastern part of Tibet, the east of the Indo-Nepal border, the northern slopes of the Meghalaya hills, the Patkai-Bum hills, the northern part of Bangladesh and of course, the Assam plains are the areas drained by the Brahmaputra River.

The river’s descent from its original height in Tibet is rapid and fast, before entering India through Arunachal Pradesh and flowing through the plains. It is joined by the Dibang River and the Lohit River at the peak of the Assam valley, after flowing for close to 35 km. It becomes much wider- as much as 10 km- when it enters Assam, where it is takes the name of the Brahmaputra River. The Jia Bhoreli River becomes a part of it at Sonitpur.

The river separates into the northern Kherkutia channel and the southern Brahmaputra channel between Dibrugarh and Lakhimpur. It narrows down at Guwahati after cutting through the rocks of the Shillong Plateau, where it becomes as narrow as 1 km.

Tributaries

The tributaries of Brahmaputra River are major rivers of North East India by themselves. Lohit River, Dhanisiri River, Bibang River are its chief left tributaries while Raidak River, Kameng River, Jaldhaka River, Teesta River are its chief right tributaries.

The Raidak River is an important right bank tributary of the Brahmaputra River in the lower course. After traveling through the mountainous terrain in Bhutan, it flows through the plains of India around Jalpaiguri.

The Jia Bhoreli River originates from a glacial lake below the snow capped Gori Chen Mountains in the Tawang district of eastern Himalayas. It is known as the Kameng River in Arunachal Pradesh.

The Lohit River originates in the Zayal Chu range of eastern Tibet and flows through the Assam plains. Traveling across the Mishmi Hills, it merges into Siang River in the Brahmaputra valley.

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