Chapter 3 Drainage Notes Class 9th Social Science Geography


Drainage – The river system is an area.

Drainage Basin- The area drained by a single river system.

Water Divide– Any elevated area such as a mountain that separated two drainage Basin

Drainage system in India

Indian rivers are divided into two groups:-

  • Himalayan Rivers
  • Peninsular Rivers

Distinguish between a Himalayan river and Peninsular river.

Himalayan River

  • Most of the river Himalayan river is perennial because they have water throughout the year.
  • They receive water from rain as well as meeting of snow.
  • The Himalayan river has long courses.
  • They perform crosional activities and carry silt and sand.

Peninsular River

  • Peninsular River is the seasonal river because their flow is dependent on rainfall.
  • During the dry season, even the large reduce into channels.
  • They have shorter and shallower courses.
  • Most of the peninsula rivers start in the Western Ghats and flow towards Bay of Bengal.

River System

A river along with his tributaries.

Indus River System

  • The river Indus rises in Tibet, near Mansarowar lake.
  • It enters in India in the Ladakh district of Jammu and Kashmir.
  • The tributaries like Beas, Satluj, |Ravi, Chenab and Jhelum join together in the Indus at Mithankot in Pakistan.
  • Indus flows at the length of 2900 km.

Indus Water Treaty

This treaty (arguments) was signed between India and Pakistan in 1960. According to this treaty, India can use 20% of its water.

The Ganga River System

  • The headwaters of Ganga called the ‘Bhagirathi’ is joined by ‘Alaknanda’ at devoprayag in Uttarakhand.
  • The tributaries like Yamuna, Ghaghara, Gandak and Kosi join it.
  • The river Yamuna rises at Yamunotri fancier joined Ganga at Allahabad.
  • The Chambal, the beta and the son are peninsular are the peninsular tributaries join in it.
  • At Tarakka in West Bengal, the river Ganga bifurcates(branched off)
  • One branch goes to southwards and joins the Bay of Bengal and other branch goes to Bangladesh and is joined by the Brahmaputra and is known as Meghma.
  • Largest Delta – Sunderbans Delta.
  • It has the length of 2500 km.

The Brahmaputra River System

  • The Brahmaputra rises in Tibet east of Mansarovar lake.
  • Most of its course lies outside India.
  • At Namcha Barwa it takes a ‘U’ turn and enters India in Arunachal Pradesh (Dihang)
  • In Tibet, the Brahmaputra carries a smaller volume of water as it is a dry and cold region.
  • But in India, it carries a large volume of water as it passes through heavy rainfall areas.
  • Every year, the river Bhramputra causes widespread destruction due to floods in Assam and Bangladesh.

Peninsular Rivers

The Narmada and Tapi flow westwards through a rift valley.

The Narmada Basin

  • It rises in the Amarkantak hills in Madhya Pradesh.
  • It flows towards the west and creates many beautiful locations like ‘Marble rocks’ near Jabalpur and ‘Deadhar falls’.

The Tapi Basin

  • The Tapi river rises in the Satpura ranges in the Betul district of Madhya Pradesh.
  • It also flows in a rift valley.

The Godavari Basin

The Godavari is the largest peninsular river.

  • It rises in the Western Ghats in the Nasik district of Maharashtra Valley/
  • Its length is about 1500 km.
  • The tributaries like purna, Wardha etc. join in it.
  • The tributaries like Manjira, Pen Ganga, and Wain Ganga are very large. So they are known as ‘Dakshin Ganga’.

The Mahanadi Basin

  • It rises in the highlands of Chhattisgarh.
  • The length-860 km.

The Krishna Basin

  • Rises near Mahabaleshwar
  • Length-1400 km.

The Kaveri Basin

  • Rises in the Brahmagiri ranges of Western Ghats.
  • Length- 760 km.

Types of Lakes

Lakes differ from each other in shape, size and other characteristics.

  1. Permanent Lakes- Most of the lakes are permanent
  2. Seasonal Lakes- Contain water during the rainy season. Sambhar lake in Rajasthan example of the seasonal lake.
  3. Some lakes are the result of the action of glaciers or ice-sheets.
  4. Ox-bow lakes- In the floodplains. Oxbow lakes ae found.
  5. Fresh water lakes. Eg. Dal lake, Nainital.

Damming of rivers for the generation of Hydel power led to the formation of lakes.

Water lake is the result of tectonic activity.

Importance of lakes and river in the Economy

  • Lakes help to regulate (control) the flow of a river.
  • It prevents floodings during rainfall and maintains even flow of water during the dry season.
  • The river and lakes can be used for developing hydel power.
  • They moderate the climate of the surrounding and maintain aquatic eco-system.
  • They help to develop tourism and provide recreation (enjoy must fun)
  • Water from rivers is a natural resource which is essential for various human activities.
  • Kaveri joins the Bay of Bengal at Cuddalore in Tamil Nadu.

Largest Salt Lake- Chillka Lake, Orissa.

Freshwater Lake- Winlar Lake in Jammu and Kashmir.

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