The Brahmaputra and Barak Valleys of Assam
Look at any map of Assam and one thing becomes clear at once: the state is really built around two river valleys. The broad Brahmaputra valley spreads across the north and the centre, while the smaller Barak valley sits in the south, and a belt of hills keeps the two apart. Almost everything else we study about Assam - its rainfall, its tea gardens, its towns, its floods and much of its history - can be traced back to these two rivers. For candidates preparing for ADRE, APSC, Assam Police or any other recruitment test, the Brahmaputra and the Barak are not simply two names to remember. They are the frame on which the whole of Assam's geography is fixed.
Where the Brahmaputra begins
The Brahmaputra is one of the longest rivers in the world and it has three different names before it reaches us. It starts from the Chemayungdung glacier, close to Mansarovar in the Kailash range of the Himalayas, deep inside Tibet. There it is known as the Yarlung Tsangpo, and it flows eastwards across the Tibetan plateau for a very long distance. Near the eastern end of the Himalayas the river makes a sharp turn, cuts a deep gorge and enters India through the Eastern Himalayas near Sadiya in Arunachal Pradesh. This entry point is important for exams, because it is here that the river changes both its direction and its name. In Arunachal the river is called the Siang or Dihang. A little further down, the Dibang and the Lohit join it, and from the meeting of these rivers the water body is finally called the Brahmaputra.
The course through Assam
The Brahmaputra enters Assam in the far east, flows right across the length of the state, and leaves for Bangladesh near Dhubri in the west. Its total length is about 2,900 kilometres, of which roughly 900 kilometres lie within Assam. The river is extremely wide and carries an enormous volume of water and silt. In different stretches its width ranges from about one kilometre to as much as eighteen kilometres, and near Sadiya the depth has been recorded at more than thirty-eight metres. Unlike a single, neat channel, the Brahmaputra is a braided river: it splits into many channels and shifts its bed constantly, leaving behind sandbars and small islands. The best known of these islands is Majuli, the largest river island in the world, which was formed by the Brahmaputra itself. On its way to the sea, the river crosses into Bangladesh, is known there as the Jamuna, and finally merges with the Ganga (Padma) and the Meghna before emptying into the Bay of Bengal.
The Barak valley of southern Assam
The Barak is the lifeline of southern Assam. It rises in the hills of Manipur and flows into Assam through the Barak valley, which is made up of the three districts of Cachar, Karimganj and Hailakandi. This valley is smaller and more compact than the Brahmaputra valley, and its river system is quite separate. Near the town of Badarpur the Barak splits into two branches, and after entering Bangladesh these branches are known as the Surma and the Kushiyara. They eventually join the Meghna system, which means that the water of the Barak valley also ends up in the Bay of Bengal, but by a different route from the Brahmaputra. Because the valley is surrounded by hills on almost every side, heavy rain here very quickly turns into local floods.
The two valleys compared
- Size and population: the Brahmaputra valley is by far the larger and more thickly populated of the two, and it holds most of Assam's towns, industries and tea gardens.
- Location: the Brahmaputra valley stretches across the north and centre, while the Barak valley lies in the south, cut off by the Meghalaya plateau and the Barail range.
- Direction of flow: the Brahmaputra flows roughly from east to west through Assam, whereas the Barak flows mainly from east to west and then turns south into Bangladesh.
- Exposure to floods: both valleys flood, but the Brahmaputra's floods are larger in scale and affect almost the whole valley, while the Barak's floods are shorter and more local.
- Economy: the Brahmaputra valley is associated with tea, oil and a wide range of crops, while the Barak valley is known for rice, tea and its fruit and vegetable trade.
Why this topic matters for competitive examinations
Questions on the Brahmaputra and Barak valleys appear again and again in the general knowledge and geography sections of Assam exams. The examiners usually test factual points such as the source of the river, its Tibetan name, the place where it enters India, its length, the width of its bed and the districts of the Barak valley. Because these facts are stable and do not change from year to year, they are among the easiest marks to secure, provided you revise them a few times. Assam-specific questions on Majuli, the Bhupen Hazarika Setu, the meaning of the name Brahmaputra and the rivers of southern Assam are especially common.
How to prepare this topic
- Fix the full journey of the Brahmaputra in your mind as a story: glacier, Tibet, Sadiya, Siang, Brahmaputra, Dhubri, Jamuna, Padma, Bay of Bengal.
- Learn the two names of the river before and after it enters India - Yarlung Tsangpo and Siang or Dihang.
- Remember the three districts of the Barak valley and the two names the Barak takes in Bangladesh.
- Note the figures: about 2,900 km total length, about 900 km in Assam, and a bed width of one to eighteen kilometres.
- Practise the questions on this page and read the explanations for any answer you get wrong.
Common exam traps
- The Brahmaputra does not enter India through Assam; it enters near Sadiya in Arunachal Pradesh and reaches Assam only after that.
- The Siang and the Dihang are names of the same river, not two different rivers.
- Majuli is an island formed by the Brahmaputra, not a man-made island or a hill.
- The Barak is not a tributary of the Brahmaputra - it belongs to a completely separate river system.
Frequently Asked Questions
Why is the Brahmaputra called a braided river?
A braided river carries a very heavy load of silt and sand, and instead of flowing in one deep channel it breaks up into many shifting channels separated by sandbars and islands. The Brahmaputra shows this pattern all along its course in Assam, which is why its bed keeps changing, its banks erode quickly and new chaporis and islands appear and disappear over time.
Is the Barak river a part of the Brahmaputra system?
No. The Brahmaputra and the Barak are two independent river systems. The Brahmaputra rises in Tibet and flows across northern Assam, while the Barak rises in the hills of Manipur and drains southern Assam. They meet the sea by different routes and are separated for their entire course by the hills of Meghalaya and the Barail range.
Which districts make up the Barak valley and why are they flood-prone?
The Barak valley consists of Cachar, Karimganj and Hailakandi. The valley lies in a bowl surrounded by hills, so when the monsoon is heavy the Barak and its tributaries fill up quickly and the water has nowhere to spread. This makes the valley one of the most flood-prone parts of Assam, and local floods can occur even when the rest of the state is comparatively dry.
How did Majuli come into existence?
Majuli is a river island created by the Brahmaputra and its distributaries. Over centuries the river changed its course and left behind a large landmass between its channels. Today it is regarded as the largest river island in the world and is also the centre of Assamese Vaishnavite culture, with many satras located on it.
What should a candidate remember about the Brahmaputra for Assam exams?
Focus on five things: the source at the Chemayungdung glacier, the Tibetan name Yarlung Tsangpo, the entry into India near Sadiya where it is called the Siang or Dihang, the total length of about 2,900 kilometres with about 900 kilometres in Assam, and its exit near Dhubri into Bangladesh where it becomes the Jamuna. These five facts answer the majority of questions asked on this river.