As per the plate tectonics, Assam is in the Easternmost projection of the Indian plate, where the plate is thrusting underneath the Eurasian plate creating a  sub-duction zone and the Himalayas. Assam possesses a unique geomorphic environment, with plains, dissected hills of the South Indian plateau system and with the Himalayas all around its North, North-East and East. 

Rivers of Assam

In this Article we discuss about Basic information of Assam General knowledge as per Geography of Assam. You can write as a notes for your Assam Direct Recruitment Exam (ADRE) same as mentioned this article. Geomorphic studies conclude that the Brahmaputra, the lifeline of Assam is an antecedent river, older than the Himalayas. The total area of Assam is 78,438 sq km. 

Rivers of Assam

The river with steep gorges and rapids in Arunachal Pradesh entering Assam, becomes a braided river (at times 16 km wide) and with tributaries, creates a flood plain (Brahmaputra valley: 80-100 km wide, 1000 km long). The hills of Karbi Anglong, North Cachar and those in and close to Guwahati (also Khasi-Garo hills) now eroded and dissected are originally parts of the South Indian plateau system. 

In the South, the Barak originating in the Barail range (Assam- Nagaland border) flows through the Cachar district with a 40-50 km wide valley and enters Bangladesh with the name Surma. 

The evolution of the modern day topographic and physiographic architecture of 
Assam, leading to development of the mighty Brahmaputra valley, the Central Assam range comprising of the Mikir and North Cachar (Barail) hills and the Barak valley extending South-Westward into alluvial plains of Bangladesh are due to the effect of several complicated cycles of geological events of the North-East India. The state can be broadly divided into the following physiographic domains

1. The Brahmaputra River Valley 
2. The Barak Valley and 
3. The hilly Regions comprising the North Cachar Hills

1.The Brahmaputra River Valley

Brahmaputra Valley The vast alluvial plains of Brahmaputra valley occupy most of the North Assam covering Goalpara, Kokrajhar, Dhubri, Kamrup, Nalbari, Barpeta, Nagaon, Darrang, Sonitpur, Sibsagar, Jorhat, Golaghat, Lakhimpur 
and Dibrugarh districts. The Brahmaputra valley is bounded by Arunachal Himalaya in the North and North-East, Patkai- Naga-Lushai range, Nagalandand the Shillong plateau in the South and South-East. 

The Brahmaputra valley with an average elevation from 50 to 120 m above m.s.1 represents a unique landscape comprising of 800 km long and 130 km wide valley delimited by thenlow-lying valley to its South and the Karbi Anglong hills and Barail range
comprising the North Cachar hills in the central part.The Brahmaputra plain region is divided into two parts

(i) North bank plain 

Major tributaries of the Brahmaputra flowing here are Subansiri, Ranganadi, Buroi, Borgong, Jia Bharali, Gabharu, Belsiri, Dhansiri, NoaNodi, Nanoi, Barnadi, Puthimari, Pagladia, Manas-Aie-Beki, Champamati, Gaurang, Tipkai and Godadhar

Subansiri river

  • Subansiri River rises beyond the Himalayas in the Tibet region. 
  • Subansiri is formed by the culmination of various small streams that have “chu” in their names, such as Tsari chu, chayal chu. 
  • Sikung chu is the main source of the Subansiri river.
  • Subansiri River is the largest tributary of the Brahmaputra River.
  • Subansiri enters India through Arunachal Pradesh and flows through the Miri hills.
  • Subansiri joins the river Brahmaputra in Assam at Jamurighat.

Kameng river

  • Kameng River rises near the Gorichen mountains in Arunachal Pradesh, near the Indo-Tibetan border. 
  • When enters in Assam plain areas and joins the river Brahmaputra.

Manas river

  • The Manas River is a trans-Himalayan river that originates in the Tibet region.
  • Originating from Tibet, it flows for 24 km before entering Bhutan and finally into India, At Jogighopa it joins the river Brahmaputra.
  • Manas river system is the largest river system in Bhutan.
  • The Manas river flows through two crucial protected areas: the Royal Manas National Park in Bhutan and the Manas wildlife sanctuary in India. 

Sankosh river

  • The Sankosh river rises in Bhutan’s northern part. It is the right bank tributary of the Brahmaputra river.
  • It is known as Puna Tsang Chu in Bhutan and is one of the most beautiful rivers in Bhutan.
  • The Sankosh river enters India and flows, forming the border between Assam and West Bengal.
  • Finally it enters Bangladesh and joins the Brahmaputra river near the Indo- Bangladesh international boundary.

Teesta river

  • The Teesta river originates in the Himalayas of North Sikkim at the Zemu glacier in the Kanchenjunga ranges.
  • The Teesta river is the lifeline of Sikkim.
  • Originating in the Himalayan heights, it has created a deep gorge in the 
  • Darjeeling hills and divides them into the Tiger Hill Range and the Kalimpong Hill Range.
  • It enters Bangladesh and joins the mighty Brahmaputra river.

(ii) South bank plain

Major tributaries of the Brahmaputra flowing here are Siang, Burhi Dihing, Disang, Dikhow, Jhanzi, Bhogdoi, Dhansiri, Kopili, Kulsi, Krishnai and Jinari.

Siang river

  • The river Siang is known by the name of the Yarlung Tsangpo in Tibet, 
  • It originating at the height of 5300 metres near the Kailash range. 
  • When entering India, it is joined by the Lohit and the Dibang rivers, and both are meet form the mighty river Brahmaputra.

Dibang river 

  • The River Dibang originates in Arunachal Pradesh near the Indo China border in the Dibang valley. 
  • This river finally joins the Lohit river, and together they join the Siang river.

Lohit River

  • The Lohit river rises in the Tibet region where it is called the Zayu river. 
  • When it enters India through Arunachal Pradesh, flowing through Mishmi Hills where it joins the Siang river to form the Brahmaputra river. 
  • The Lohit river carries abundant amounts of lateritic soil, which gives it a reddish colour of the water of river. 

Burhi dihing river

  • It is formed by the confluence of two small rivers, Namphuk and Namchik
  • It originate in the Patkai hills, part of the Eastern Himalayan ranges in Arunachal Pradesh. 
  • It finally joins the river Brahmaputra in the Assam plains.
  • Its basin is used for the cultivation of tea.

Dhansiri river

  • Dhansiri originates from southwest Nagaland, flowing along the Intanki national park. 
  • It joins the river Brahmaputra in the Assam plains.

Kopili river

  • The Kopili river originates in the Saipong reserve forest in South East Meghalaya 
  • It forms part of the border between Assam and Meghalaya States.
  • It meet with the river Brahmaputra in the Koplimukh in the Assam plains

2. The Barak River Valley 

Barak valley is one of the major physiographic regions situated at the southern end of Assam. it is surrounded by the Meghalaya Plateau and the Barail ranges of the North Cachar hills,on the east lie the Manipur hills,on the south lie the Mizo hills and on the west lies the Kushiyara-Surma plain of the Sylhet district of Bangladesh.

  1. Barak valley consists of the Barak plain and its adjacent northern and southern foothills. 
  2. Barak plain is also known as Cachar plain. It has been formed due to the deposition of alluvial sediments carried by the river Barak and its tributaries from the hills in the north and the south. 
Barak river flows over a distance of 225 km from east to west through Cachar district towards the northern boundary districts of Hailakandi and Karimganj. Its major tributaries are 
  • North bank tributaries: Chiri, Diksa, Digli, Jiri, Madhura, Jutinga, Larang, etc. 
  • South bank tributaries: Sonai, Dhakeshwari-Katakhal, Singla, Langai, etc