Brahmaputra River

The Brahmaputra (/ˌbrɑːməˈpuːtrə/) is one of the major rivers of Asia, a trans-boundary river which flows through China, India and Bangladesh. As such, it is known by various names in the region: Assamese: লুইত luit [luɪt], ব্ৰহ্মপুত্ৰ নৈ Brohmoputro noi, ব্ৰহ্মপুত্ৰ নদ (the tatsama ‘নদ’ nod, masculine form of the tatsama ‘নদী’ nodi “river”) Brohmoputro [bɹɔɦmɔputɹɔ]; Sanskrit: ब्रह्मपुत्र, IAST: Brahmaputra; Tibetan: ཡར་ཀླུངས་གཙང་པོ་, Wylie: yar klung gtsang po Yarlung Tsangpo; simplified Chinese: 布拉马普特拉河; traditional Chinese: 布拉馬普特拉河; pinyin: Bùlāmǎpǔtèlā Hé. It is also called Tsangpo-Brahmaputra and red river of India (when referring to the whole river including the stretch within Tibet). The Manas River, which runs through Bhutan, joins it at Jogighopa, in India. It is the ninth largest river in the world by discharge, and the 15th longest.

With its origin in the Manasarovar Lake region, near the Mount Kailash, located on the northern side of the Himalayas in Burang County of Tibet as the Yarlung Tsangpo River, it flows along southern Tibet to break through the Himalayas in great gorges (including the Yarlung Tsangpo Grand Canyon) and into Arunachal Pradesh (India). It flows southwest through the Assam Valley as Brahmaputra and south through Bangladesh as the Jamuna (not to be mistaken with Yamuna of India). In the vast Ganges Delta, it merges with the Padma, the popular name of the river Ganges in Bangladesh, and finally, after merging with Padma, it becomes the Meghna and from here, it flows as Meghna river before emptying into the Bay of Bengal.

About 2,899.9 km (1,801.9 mi) long, the Brahmaputra is an important river for irrigation and transportation in the region. The average depth of the river is 38 m (124 ft) and maximum depth is 120 m (380 ft). The river is prone to catastrophic flooding in the Spring when the Himalayan snow melts. The average discharge of the river is about 19,800 m3/s (700,000 cu ft/s), and floods can reach over 100,000 m3/s (3,500,000 cu ft/s). It is a classic example of a braided river and is highly susceptible to channel migration and avulsion. It is also one of the few rivers in the world that exhibits a tidal bore. It is navigable for most of its length.

The river drains the Himalayan east of the Indo-Nepal border, south-central portion of the Tibetan plateau above the Ganga basin, south-eastern portion of Tibet, the Patkai-Bum hills, the northern slopes of the Meghalaya hills, the Assam plains, and the northern portion of Bangladesh. The basin, especially south of Tibet, is characterized by high levels of rainfall. Kangchenjunga (8,586 m) is the only peak above 8,000 m, hence is the highest point within the Brahmaputra basin.

The Brahmaputra’s upper course was long unknown, and its identity with the Yarlung Tsangpo was only established by exploration in 1884–86. This river is often called the Tsangpo-Brahmaputra river.

The lower reaches are sacred to Hindus. While most rivers on the Indian subcontinent have female names, this river has a rare male name. Brahmaputra means “son of Brahma” in Sanskrit (putra means “son”).

Course

Yarlung Tsangpo River in Tibet.
Yarlung Tsangpo River in Tibet.

The Brahmaputra River, also called the Yarlung Tsangpo in Tibetan language, originates on the Angsi Glacier located on the northern side of the Himalayas in Burang County of Tibet. The source of the river was earlier thought to be on the Chemayungdung glacier, which covers the slopes of the Himalayas about 97 km (60 mi) southeast of Lake Manasarovar in southwestern Tibet. The river is 3,848 km (2,391 mi) long, and its drainage area is 712,035 km2 (274,918 sq mi) according to the new findings, while previous documents showed its length varied from 2,900 to 3,350 km and its drainage area between 520,000 and 1.73 million km2. This finding has been given by Liu Shaochuang, a researcher with the Institute of Remote Sensing Applications under the analysis using expeditions and satellite imagery from the Chinese Academy of Sciences (CAS).

From its source, the river runs for nearly 1,100 km (680 mi) in a generally easterly direction between the main range of the Himalayas to the south and the Kailas Range to the north. Throughout its upper course, the river is generally known as the Tsangpo (“Purifier”); it is also known by its Chinese name (Yarlung Zangbo) and by other local Tibetan names.

In Tibet, the Tsangpo receives a number of tributaries. The most important left-bank tributaries are the Raka Zangbo (Raka Tsangpo), which joins the river west of Xigazê (Shigatse), and the Lhasa (Kyi), which flows past the Tibetan capital of Lhasa and joins the Tsangpo at Qüxü. The Nyang Qu (Gyamda) River joins the river from the north at Zela (Tsela Dzong). On the right bank, a second river called the Nyang Qu (Nyang Chu) meets the Tsangpo at Xigazê.

After passing Pi (Pe) in Tibet, the river turns suddenly to the north and northeast and cuts a course through a succession of great narrow gorges between the mountainous massifs of Gyala Peri and Namcha Barwa in a series of rapids and cascades. Thereafter, the river turns south and southwest and flows through a deep gorge (the “Grand Canyon” of the Tsangpo) across the eastern extremity of the Himalayas with canyon walls that extend upward for 5,000 m (16,000 ft) and more on each side. During that stretch, the river enters northern Arunachal Pradesh state in northeastern India, where it is known as the Dihang (or Siang) River, and turns more southerly.

Assam and adjoining region

Brahmaputra basin in India
Brahmaputra basin in India

A view of sunset in the Brahmaputra from Dibrugarh
The Brahmaputra enters India in the state of Arunachal Pradesh, where it is called Siang. It makes a very rapid descent from its original height in Tibet and finally appears in the plains, where it is called Dihang. It flows for about 35 km (22 mi) and is joined by the Dibang River and the Lohit River at the head of the Assam Valley. Below the Lohit, the river is called Brahmaputra and Burlung-Buthur by native Bodo tribals, it then enters the state of Assam, and becomes very wide—as wide as 20 km (12 mi) in parts of Assam.

The Dihang, winding out of the mountains, turns toward the southeast and descends into a low-lying basin as it enters northeastern Assam state. Just west of the town of Sadiya, the river again turns to the southwest and is joined by two mountain streams, the Lohit, and the Dibang. Below that confluence, about 1,450 km (900 mi) from the Bay of Bengal, the river becomes known conventionally as the Brahmaputra (“Son of Brahma”). In Assam, the river is mighty, even in the dry season, and during the rains, its banks are more than 8 km (5.0 mi) apart. As the river follows its braided 700 km (430 mi) course through the valley, it receives several rapidly rushing Himalayan streams, including the Subansiri, Kameng, Bhareli, Dhansiri, Manas, Champamati, Saralbhanga, and Sankosh Rivers. The main tributaries from the hills and from the plateau to the south are the Burhi Dihing, the Disang, the Dikhu, and the Kopili.

Between Dibrugarh and Lakhimpur Districts, the river divides into two channels—the northern Kherkutia channel and the southern Brahmaputra channel. The two channels join again about 100 km (62 mi) downstream, forming the Majuli island, which is the largest river island in the world. At Guwahati, near the ancient pilgrimage center of Hajo, the Brahmaputra cuts through the rocks of the Shillong Plateau and is at its narrowest at 1 km (1,100 yd) bank-to-bank. Because of the river’s narrow width, the Battle of Saraighat was fought here in March 1671. The first combined rail/road bridge across the Brahmaputra was opened to traffic in April 1962 at Saraighat.

The environment of the Brahmaputra floodplains in Assam has been described as the Brahmaputra Valley semi-evergreen forests ecoregion.

Bangladesh

Rivers of Bangladesh, including the Brahmaputra
Rivers of Bangladesh, including the Brahmaputra

In Bangladesh, the Brahmaputra is joined by the Teesta River (or Tista), one of its largest tributaries. Below the Tista, the Brahmaputra splits into two distributary branches. The western branch, which contains the majority of the river’s flow, continues due south as the Jamuna (Jomuna) to merge with the lower Ganga, called the Padma River (Pôdda). The eastern branch, formerly the larger, but now much smaller, is called the lower or Old Brahmaputra (Brommoputro). It curves southeast to join the Meghna River near Dhaka. The Padma and Meghna converge near Chandpur and flow out into the Bay of Bengal. This final part of the river is called Meghna.

The Brahmaputra enters the plains of Bangladesh after turning south around the Garo Hills below Dhuburi, India. After flowing past Chilmari, Bangladesh, it is joined on its right bank by the Tista River and then follows a 240 km (150-mi) course due south as the Jamuna River. (South of Gaibanda, the Old Brahmaputra leaves the left bank of the mainstream and flows past Jamalpur and Mymensingh to join the Meghna River at Bhairab Bazar.) Before its confluence with the Ganga, the Jamuna receives the combined waters of the Baral, Atrai, and Hurasagar Rivers on its right bank and becomes the point of departure of the large Dhaleswari River on its left bank. A tributary of the Dhaleswari, the Buriganga (“Old Ganga”), flows past Dhaka, the capital of Bangladesh, and joins the Meghna River above Munshiganj.

The Jamuna joins with the Ganga north of Goalundo Ghat, below which, as the Padma, their combined waters flow to the southeast for a distance of about 120 km (75 mi). After several smaller channels branch off to feed the Ganga-Brahmaputra delta to the south, the main body of the Padma reaches its confluence with the Meghna River near Chandpur and then enters the Bay of Bengal through the Meghna estuary and lesser channels flowing through the delta. The growth of the Ganga-Brahmaputra Delta is dominated by tidal processes.

The Ganga Delta, fed by the waters of numerous rivers, including the Ganga and Brahmaputra, is 59,570 square kilometers (23,000 sq mi) the largest river deltas in the world.

Basin characteristics

The Brahmaputra River from Space
The Brahmaputra River from Space

The basin of the Brahmaputra river is 651 334 km2 and it is a good example of a braided river and meanders quite a bit and frequently forms temporary sand bars. A region of significant tectonic activity has developed in the Jamuna River and is associated with the Himalayan uplift and development of the Bengal foredeep. Several researchers have hypothesized that the underlying structural control on the location of the major river systems of Bangladesh. A zone of ‘structural weakness’ along the present course of the Ganga-Jamuna-Padma Rivers due to either a subsiding trough or a fault at depth has been observed by Morgan and Melntire. (1959). Scijmonsbergen (1999) contends that width changes in the Jamuna may respond to these faults and they may also cause increased sedimentation upstream of the fault. He presented a few images to argue that a fault downstream of the Bangabandhu Multipurpose Bridge has affected channel migration. Huge accumulations of sediment that have been fed from Himalayan erosion has been produced due to the deepening of the Bengal Basin, with the thickness of sediment above the Precambrian basement increasing from a few hundred meters in the shelf region to over 18 km in the Bengal foredeep to the south. The tectonic and climatic context for the large water and sediment discharges in the rivers of Bangladesh was set by the ongoing subsidence in the Bengal Basin, combined with high rates of Himalayan uplift. The control of uplift and subsidence is, however, clear. The courses of the Jamuna and Ganga Rivers are first-order controls due to the fact that they are most influenced by the uplifted Plcistoccnc terraces of the Barind and Madhupur tracts.

Source: Wikipedia

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