02 Drainage

The river system of an area is called drainage. Drainage basin is the area drained by a single river system. Drainage basins are separated by upland areas or elevations. The world’s largest drainage basin is of the Amazon River.

Drainage Patterns:

The streams within a drainage basin form certain patterns, depending on the slope of land, underlying rock structure as well as the climatic conditions of the area. These are dendritic, trellis, rectangular, and radial patterns.

Drainage Systems in India:

  • The Indian rivers are divided into two major groups:
    • The Himalayan rivers:
      • They originate from the Himalayas and are long and merge with many large and important tributaries.
    • Peninsular rivers
      • Some originate in the central highlands or Western Ghats and flow westward towards the Bay of Bengal

The Himalayan Rivers

  • Major Himalayan rivers are: Indus, Ganga and Brahmaputra

The Indus River System

  • The Indus River system originates near Mansarovar Lake in Tibet and flows westward to enter India forming a gorge.

The Ganga River System

  • River Ganga originates at the Gangotri Galcier.

The Brahmaputra River System

  • The Brahmaputra river originates from the east of Mansarowar lake in Tibet and flows eastward parallel to the Himalayas

The Peninsular Rivers

  • The major rivers are: the Mahanadi, the Godavari, the Krishna and the Kaveri.

The Narmada Basin

  • It originates in the Amarkantak hills in Madhya Pradesh.

The Tapi Basin

  • The Tapi rises in the Satpura ranges, in Betul district of Madhya Pradesh. It covers parts of Madhya Pradesh, Gujarat and Maharashtra.

The Godavari Basin

  • Godavari originates from the slopes of the Western Ghats in the Nasik district of Maharashtra and drains into the Bay of Bengal.

The Mahanadi Basin

  • The Mahanadi River originates in the highlands of Chhattisgarh and drains into the Bay of Bengal through Odisha.

The Krishna Basin

  • The Krishna river originates from a spring near Mahabaleshwar and drains into the Bay of Bengal.

The Kaveri Basin

  • The Kaveri River originates in the Brahmagiri range of the Western Ghats and drains into the Bay of Bengal in south of Cuddalore in Tamil Nadu.


  • Some lakes in India have water throughout while others have water only during rains.
  • Some originate from glaciers and ice sheets and others are formed by wind, river action and human activities.
    • Ox-bow Lake: This is formed when a part of the river is cut-off from the original course of the mainstream in a u- shape.
    • Lagoon: This is formed by spits and bars in coastal areas.
    • Saltwater Lake: Sambhar Lake in Rajathan is used for producing salt.
    • Glacial Lake: This is formed by melting of glaciers.
    • Man Made Lakes: Guru Gobind Sagar (Bhakra Nangal Project) is a man-made reservoir in Bilaspur District of Himachal Pradesh.

Role of rivers in the Economy

  • Water is a basic natural resource and hence riverbanks have attracted settlers from ancient times. River water is essential for many human activities like irrigation, navigation and hydro power generation.

River Pollution

  • The quantity of water is affected by the increasing demand of river water for domestic, municipal, industrial and agricultural purposes.
  • The quality of water and its self-cleansing property is deteriorated by untreated sewage and industrial effluents that are drained into river bodies.
  • Some schemes are undertaken to avoid further pollution of rivers.
    • The Namami Gange Programme
    • Namami Devi Narmade
    • National River Conservation Plan (NRCP)

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