Drainage System of India - Assam PCS Exam Notes

Drainage: Flow of water through well-defined channels. Network of such channels is called a drainage system .
Drainage basin: An area drained by a river and its tributaries.
Watershed: Boundary line separating one drainage basin from other.
River basins are larger watersheds.
Drainage pattern of an area depends on the geological time period, nature and structure of rocks, topography, rocks, slope, amount of water and periodicity of flow.

Important drainage patterns:

Dendritic: Resembling the branches of a tree. Eg. Northern Plain rivers
Radial: Originate from a hill and flow in all directions. Eg. Rivers in Amarkantak
Trellis: Primary tributaries parallel to each other and secondary tributaries join them at right angles.
Centripetal: Rivers discharge waters from all directions in a lake or depression

A river drains the water collected from a specific area, which is called its catchment area.

Nearly 77 pc of drainage is towards the Bay of Bengal while about 23 pc is towards the Arabian Sea.

The Himalayan Drainage System

Mainly includes the Ganga, Indus and Brahmaputra river basins.

Over the plains, rivers of this system change the course often. River Kosi is also known as the ‘sorrow of Bihar’ due to flooding by its frequent change of course by deposition of sediments.

Evolution

Geologists believe that a mighty river called Shivalik or Indo-Brahma traversed the entire length of the Himalayas some 5-24 million years ago. Over time this got dismembered into the present three major river systems.

The Indus System

Indus river originates from a glacier near Bokhar Chu in Tibet in the Kailash Mountain range. Known as Singi Khamban (Lion’s mouth) in Tibet. It forms a spectacular gorge near Gilgit in J&K. Enters Pakistan near Chillar in the Dardistan region. Flows only through the Leh distt of J&K.

Smaller tributaries: Shyok, Gilgit, Zaskar, Nubra, Hunza, Shigar, Gasting, Dras. On right bank: Kabul river, Khurram, Tochi, Gomal, Viboa and hte Sangar.

Major tributaries: Satluj, Beas, Ravi, Chenab, Jhelum

Jhelum	Origin: Verinag at foot of Pir Pinjal. Flows through Srinagar and the Wular lake. Joins Chenab near Jhang in Pakistan
Chenab	Origin: Two streams (Chandra and Bhaga) which join at Tandi near Keylong in HP. Largest tributary of Indus. Aka Chandrabhaga. Flows for 1180 KM before entering Pakistan
Ravi	Origin: Kullu hills of HP near Rohtang Pass. Enters Pakistan and joins Chenab near Sarai Sidhu
Beas	Origin: Beas Kund near Rohtang pass. Forms gorges at Kati and Largi in the Dhaoladhar range. Meets Satluj near Harike.
Satluj	Origin: Rakas lake near Mansarowar in Tibet. Known as Langchen Khambab in Tibet. Enters India at Ropar. Antecedent river. Bhakra Nangal Project is on this river.

The Ganga System

It is the largest river system in India.

Ganga rises in the Gangotri glacier near Gaumukh in the Uttarkashi district. Here it is known as the Bhagirathi. At Devprayag, Bhagirathi meets Alaknanda and is known as Ganga hereafter.

Panchprayag

Vishnu Ganga

Joshimath

Dhauli and Vishnu Ganga meet to form Alaknanda

Alaknanda	Origin: Satopanth glacier above Badrinath. Consists of Dhauli and Vishnu Ganga.
Yamuna	Origin: Yamnotri glacier on Banderpunch range. Joins Ganga at Prayag (Allahabad). RBT: Chambal, Sind, Betwa, Ken LBT: Hindan, Rind, Sengar, Varuna. Agra canal
Chambal	Origin: Mhow in Malwa plateau. Gandhi Sagar dam, Rana Pratap Sagar dam and Jawahar Sagar dam. Famour for Chambal ravines.
Gandak	Origin: In Nepal between Dhaulgiri and Mt. Everest. Enters Ganga plain in Champaran and joins Ganga at Sonpur near Patna. Two streams: Kaliganfak and Trishulganga.
Ghaghra	Origin: Glaciers of Mapchachungo Tributaries: Tila, Seti and Beri Deep gorge at Shishpani Sarda (Kali) joint it and meet Ganga at Chhapra.
Kosi	Origin: North of Mt. Everest in Tibet. Tributaties: Son Kosi, Tamur Kosi, Arun Changes course often. Sorrow of Bihar.

Ganga enters the plains at Haridwar.
Left Bank tributaries (LBT): Ramganga, Gomati, Ghaghara, Gandak, Kosi and Mahananda.
Right Bank tributaries (RBT): Son
Discharges into Bay of Bengal near Sagar island.

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