Drainage System | The Brahmaputra River System

The Brahmaputra River System

Brahmaputra river is one of the largest rivers in the world. This valley has an average width of about 80 Km. The river originates from the Kailash ranges of the Himalayas at an elevation of 5300 M. After flowing through Tibet it enters India through Arunachal Pradesh and flows through Assam and Bangladesh before it joins the Bay of Bengal. It flows eastward in Tibet and south, south-west in India and traverses a distance of about 2900 km out of which 1,700km is in Tibet, 900 km is in India and 300 km is in Bangladesh
The catchments area of Brahmaputra in Tibet is - 2, 93,000 Sq. Km, In India and Bhutan, is- 2,40,000 Sq. Km and In Bangladesh is- 47,000 Sq. Km. The Brahmaputra basin extends over an area of 5,80,000 Sq. Km up to its confluence within Bangladesh. In the region of Tibet, It is known as the name of Yarlung Tsangpo. It enters by the names of Siang and Dihang in India. And after it is joined by its two main tributaries, the Dibang and the Lohit.
The average width of Brahmaputra is 5.46 Km. The maximum discharge of Brahmaputra at Pandu near Guwahati was recorded as 72,779 cumecs on 23.08.62 and the minimum discharge was recorded as 1757 cumec on 22.02.63. The average annual discharge is about 20,000 cumec and the average dry season discharge is 4,420 cumec.

The river slope is very steep till it enters India. A drop of about 4800 M is achieved in a length at about 1700 Km in China (Tibet). This average slope of about 2.82 m/Km gets reduced to about 0.1m/Km in Assam valley. Due to this sudden flattening of river slope, the river becomes braided in nature in the Assam valley. During its course in Assam valley from Kobo to Dhubri the river is joined by about 20 (twenty) important tributaries on its North bank and 13 (thirteen) on its South bank. Joining of these tributaries bringing high sediment load activates braiding. 

Brahmaputra sub-basin extends over an area of 580,000 sq. km lying in Tibet (China), Bhutan, India and Bangladesh. The drainage area lying in India is 194413 sq.km which is nearly 5.9% of the total geographical area of the country. It is bounded on the north by the Himalayas, on the east by the Patkari range of hills running along the Assam-Burma border, on the south by the Assam range of hills and on the west by the Himalayas and the ridge .separating it from Ganga sub-basin. The sub-basin lies in the States of Arunachal Pradesh, Assam, Nagaland, Meghalaya, West Bengal and Sikkim.

Climate of River Brahmaputra
The climate of the Brahmaputra valley varies from the harsh, cold, and dry conditions found in Tibet to the generally hot and humid conditions prevailing in Assam state and in Bangladesh. Tibetan winters are severely cold, with average temperatures below 32 °F (0 °C), while summers are mild and sunny. The upper river valley lies in the rain shadow of the Himalayas, and precipitation there is relatively light: Lhasa receives about 16 inches (400 mm) annually.

Plant and Animal Life
Along the upper reaches of the Brahmaputra (Tsangpo) on the high plateau of Tibet, the vegetation is mainly xerophytic (drought-resistant) shrubs and grasses. As the river descends from Tibet, increased precipitation supports the growth of forests. . At even lower elevations, tall reed jungles grow in the swamps and depressed water-filled areas (jheels) of the immense floodplains. Around towns and villages in the Assam Valley, the many fruit trees yield plantains, papayas, mangoes, and jackfruit. Bamboo thickets abound throughout Assam and Bangladesh. 
Major Tributaries of Brahmaputra River System

Tributaries from North Bank	Tributaries from South Bank
The Jiadhal	The Krishnai
The Subansiri	The Dudhnai
The Siang	The Digaru
The Kameng (Jiabharali in Assam)	The Kopili
The Dhansiri(North)	The Dhansiri(S)
The Puthimari	The Dikhow
The Pagladiya	The Debang
The Manas	The Buridehing
The Champamati	The Noa Dehing
The Aie
The Saralbhanga
The Sankosh

It receives numerous tributaries in its 750 km long journey through the Assam valley. Its major left bank tributaries are the Burhi Dihing, Dhansari (South) and Kalang whereas the important right bank tributaries are the Subansiri, Kameng, Manas and Sankosh.


Subansiri River
Subansiri River is also called as Gold River because it is famous for its gold dust. It flows through the Lower Subansiri District in Arunachal Pradesh. Subansari, a swift river offers excellent kayaking opportunities.

Kameng River
Kameng River in the eastern Himalayan mountains originates in the Tawang district. It flows through West Kameng District, Arunachal Pradesh, and Sonitpur District of Assam. The Kameng forms the boundary between East Kameng District and West Kameng Districts. The Pakhui Wildlife Sanctuary and the Kaziranga National Park are located near the Kameng River.

Manas River
Manas River is a transboundary river in the Himalayan foothills between southern Bhutan and India. The total length of the river is 376 km, flows through Bhutan for 272 km and then through Assam for 104 km before it joins the mighty Brahmaputra River at Jogighopa. The river valley has two major reserve forest areas, namely the Royal Manas National Park in Bhutan and the contiguous Manas Wildlife Sanctuary.

Sankosh River
It rises in northern Bhutan and empties into the Brahmaputra in the state of Assam. The upper catchment of the river is glaciated, middle and the lower courses flow along V-shaped valleys that have been carved by running water. The entire catchment of the river is covered with forests.