NCERT Folder 9th Geography Chapter 3 : Drainage

Geography

Class 9

Chapter 3

Drainage

Revision Notes

Important Terms

  • Basin : A part of the earth’s surface consisting of rock strata that slope down to a common centre.
  • Drainage Basin : The area drained by a single river system is called a drainage basin.
  • Water divide : Any elevated area, such as a mountain or an upland, separating two drainage basins. Such an upland is known as a water divide.
  • Perennial : It is a stream or river that exhibits continuous flow of water throughout the year.
  • Dendritic : The stream with its tributaries which resembles the branches of a tree- Thus, the name dendritic.
  • Trellis : A river joined by its tributaries, at approximately right angles, develops a trellis pattern.
  • Rectangular : A drainage pattern that develops on a strongly-joint rocky terrain.
  • Radial : The radial pattern develops when streams flows in different directions from a central peak or dome-like structure.
  • River System : A river system is a way of defining the larger networks of streams, lakes and rivers that are part of a larger river’s network of tributaries and distributaries.
  • Indus Water Treaty : According to the provisions of this treaty (signed in 1960), India can use only 20 per cent of the total water carried by the Indus river system.
  • Distributary : A stream or small river that splits off from a larger river and flows in a different direction.
  • Sunderban Delta : The world’s largest and fastest growing delta. It is also the home of the Royal Bengal Tiger.
  • Peninsula : A large area bounded by the sea on three sides.
  • Delta : A piece of land shaped like a triangle that is formed when a river splits into smaller rivers before it flows into an ocean.
  • Tributary : A river or stream that flows into a larger river or lake.
  • Estuary : The tidal mouth of a large river, where the tide meets the stream.
  • Ox-bow lake : It is a U shaped water body formed when a meandering river is cut off from the mainstream.
  • Lagoon : When the lake is formed by spits and bars in coastal areas, it is called a lagoon.
  • Glacial lake : A lake formed by melting of the glacier is called a glacial lake.
  • Irrigation : Supply of water for agriculture purpose from canals, wells and tanks artificially or manually.
  • Navigation : Travel or traffic by vessels, especially commercial shipping.
  • Hydro-power : Power derived from running or falling water.
  • River pollution : It is a form of water pollution which occurs due to the direct or indirect discharge of pollutants into the river.
  • Urbanisation : The process by which towns and cities are formed and become larger, as more and more people begin living and working in central areas.
  • Industrialisation : The development of industries in a country or region on a wide scale.

Summary

Drainage Patterns

  • The term drainage describes the river system of an area.
  • The area drained by a single river system is called a drainage basin.
  • Any elevated area, such as a mountain or upland, separates two drainage basins. Such upland is known as a water divide.
  • The world’s largest drainage basin is that of the Amazon River.
  • Drainage System in India
    • The drainage systems of India are mainly controlled by the broad relief features of the subcontinent.
    • The Indian rivers are divided into two major groups: the Himalayan rivers and the Peninsular rivers.
    • Most of the Himalayan rivers are perennial, therefore, they have water throughout the year.
    • The Himalayan rivers have long courses from their source to the sea.
    • A large number of Peninsular rivers are seasonal, as their flow is dependent on rainfall.

The Himalayan Rivers

  • The Himalayan rivers
    • The major Himalayan Rivers include the Indus, Ganga and the Brahmaputra. These rivers are long and are joined by many large and important tributaries.
    • A river along with its tributaries is called a river system.
  • The Indus River System
    • The river Indus rises in Tibet, near Lake Mansarowar. Flowing west, it enters India in the Ladakh district of Jammu and Kashmir.
    • The river has several tributaries such as the Zaskar, Nubra, Shyok and Hunza.
    • The Indus flows southwards, eventually reaching the Arabian Sea.
    • With a total length of 2,900 km, the Indus is one of the longest rivers of the world.
    • According to the regulations of the Indus Water Treaty (1960), India can use only 20 per cent of the total water carried by Indus river system.
  • The Ganga River System
    • The headwaters of the Ganga, called the Bhagirathi, is fed by the Gangotri Glacier and joined by the Alaknanda at Devaprayag in Uttarakhand.
    • The Ganga is joined by many tributaries from the Himalayas, such as the Yamuna, the Ghaghara, the Gandak and the Kosi.
    • The main tributaries, which come from the peninsular uplands, are the Chambal, the Betwa and the Son.
    • The river bifurcates in West Bengal and the Bhagirathi-Hooghly flows southwards through the deltaic plains into the Bay of Bengal.
    • The delta formed by the Ganga and the Brahmaputra rivers is known as the Sunderban Delta.
    • The Sunderban Delta is the world’s largest and fastest growing delta. It is also the home of Royal Bengal Tiger.
    • The length of the river Ganga is over 2,500 km.
  • The Brahmaputra River System
    • The Brahmaputra rises in Tibet, east of Mansarowar Lake, very close to the sources of the Indus and the Satluj.
    • Brahmaputra is known as Tsang Po in Tibet and Jamuna in Bangladesh.
      The Brahmaputra has a braided channel in its entire length in Assam and forms many riverine islands.
    • Every year, during the rainy season, the river overflows its banks, causing widespread devastation due to floods in Assam and Bangladesh.

The Peninsular Rivers

  • The Peninsular Rivers
    • The main water divide in Peninsular India is formed by the Western Ghats, which runs from north to south, close to the western coast.
    • Major rivers of the peninsula are the Narmada and the Tapi, Mahanadi, Godavari, Krishna and Kaveri. They flow eastwards and drain into the Bay of Bengal. These rivers make deltas at their mouths.
    • The Narmada and the Tapi are the only long rivers, which flow westward and make estuaries.
  • The Narmada Basin
    • The Narmada rises in the Amarkantak hills in Madhya Pradesh.
    • The Marble Rocks, near Jabalpur, where the Narmada flows through a deep gorge, and the Dhuadhar Falls, where the river plunges over steep rocks, are some of the notable locations along the Narmada River.
    • The Narmada basin covers parts of Madhya Pradesh and Gujarat.
  • The Tapi Basin
    • The Tapi rises in the Satpura ranges, in the Betul district of Madhya Pradesh.
    • Its basin covers parts of Madhya Pradesh, Gujarat and Maharashtra.
  • The Godavari Basin
    • The Godavari is the largest Peninsular River.
    • It rises from the slopes of the Western Ghats in the Nashik district of Maharashtra. Its length is about 1,500 km.
    • The drainage basin of the Godavari River is the largest among the Peninsular rivers.
    • Important tributaries of the Godavari are the Purna, Wardha, Pranhita, Manjra, Wainganga and Penganga.
    • The Godavari River is also known as the ‘Dakshin Ganga’ because of its length and the area it covers.
  • The Mahanadi Basin
    • The Mahanadi rises in the highlands of Chhattisgarh.
    • It flows through Odisha to reach the Bay of Bengal.
  • The Krishna Basin
    • Rising from a spring near Mahabaleshwar, the Krishna flows for about 1,400 km and reaches the Bay of Bengal.
    • Tungabhadra, Koyana, Ghatprabha, Musi and Bhima are some of its tributaries.
  • The Kaveri Basin
    • The Kaveri rises in the Brahmagri range of the Western Ghats and it reaches the Bay of Bengal.
    • The main tributaries are the Amravati, the Bhavani, the Hemavati and the Kabini.
    • Its basin drains parts of Karnataka, Kerala and Tamil Nadu.
    • The River Kaveri makes the second biggest waterfall in India, known as Sivasamudram.

Lakes

  • Lakes
    • Lake is a large area of water surrounded by land. Lakes of large extent are called the seas, like the Caspian, the Dead and the Aral Sea.
    • India has many lakes. These differ from each other in the size and other characteristics. Most lakes are permanent, while others contain water only during the rainy season.
    • Lakes are formed by the following processes: the action of glaciers and ice sheets, by wind, river action and human activities.
    • Most of the freshwater lakes are in the Himalayan region. They are of glacial origin.
    • The Wular Lake in Jammu and Kashmir is the largest freshwater lake in India.
    • Apart from natural lakes, the damming of the rivers for the generation of hydel power has also led to the formation of lakes such as Guru Gobind Sagar Lake (Bhakra Nangal Project).
  • Importance of lakes :
    • A lake helps to regulate the flow of a river.
    • During heavy rainfall, it prevents flooding, and during the dry season, it helps to maintain an even flow of water.
    • Lakes can also be used for developing hydel power.
    • They moderate the climate of the surroundings; maintain the aquatic ecosystem, enhance natural beauty, help develop tourism and provide recreation.

Role Of Rivers In The Economy

  • Role of Rivers in the Economy
    • Rivers are of great value to human beings :
      • Rivers have been of fundamental importance throughout the human history.
      • Water from the rivers is a basic natural resource, essential for various human activities.
      • The river banks have attracted settlers from ancient times. These settlements have now become big cities.
      • Using rivers for irrigation, navigation, hydro-power generation is of special significance – particularly to a country like India, where agriculture is the major source of livelihood of the majority of its population.

River Pollution

  • River Pollution
    • The growing domestic, municipal, industrial and agricultural demand for water from rivers naturally affects the quality of water.
    • The increasing urbanisation and industrialisation are responsible for the rising pollution level of many rivers.
    • Concern over rising pollution in our rivers led to the launching of various action plans to clean the rivers.

Intext Questions

Find Out

(Page No. 17)

Question.1. Find out which river has the largest basin in India.
Answer. The Ganga river.

Find Out

(Page No. 22)

Question.1. The name of the biggest waterfall in India.
Answer. Kunchikal falls in Karnataka.

Question.2. Find out why lakes of large extent are called seas like the Caspian, the Dead and the Aral seas.
Answer. Because when they were not landlocked, they were seas.

Activity

(Page No. 23)

Question.1. Make a list of natural and artificial lakes with the help of the atlas.
Answer.
Natural Lake

  1. Wular lake
  2. Dal lake
  3. Nainital lake
  4. Bhimtal lake
  5. Loktok lake
  6. Barapani lake
  7. Chilka lake
  8. Sambhar lake
  9. Pulicat lake
  10. Kolleru lake
  11. Vembanad lake

Artificial Lake

  1. Gobind sagar
  2. Rana Pratap
  3. Rana Pratap sagar
  4. Nagarjuna sagar
  5. Hirakud

NCERT Solution

(Page No. 15)

Question.1. Choose the right answer from the four alternatives given below:

(i) In which of the following States is the Wular Lake located?
(a) Rajasthan
(b) Uttar Pradesh
(c) Punjab
(d) Jammu and Kashmir
Answer. Jammu and Kashmir

(ii) The river Narmada has its source at:
(a) Satpura
(b) Brahmagir
(c) Amarkantak
(d) Slopes of the Western Ghats
Answer. Amarkantak

(iii) Which one of the following lakes is a salt water lake?
(a) Sambhar
(b) Dal
(c) Wular
(d) Gobind Sagar
Answer. Sambhar

(iv) Which one of the following is the longest river of the Peninsular India?
(a) Narmada
(b) Krishna
(c) Godavari
(d) Mahanadi
Answer. Godavari

(v) Which among the following rivers flows through a rift valley?
(a) Damodar
(b) Tungabhadra
(c) Krishna
(d) Tapi
Answer. Tapi

Question.2. Answer the following questions briefly.
(i) What is meant by a water divide? Give an example.
Answer. Any elevated area such as a mountain or an upland that separates two drainage basins is called a water divide. An example of water divide is the Western Ghats.

(ii) Which is the largest river basin in India?
Answer. The Ganga river basin is the largest river basin in India.

(iii) Where do the rivers Indus and Ganga have their origin?
Answer. Indus rises in Tibet near Lake Mansarovar.
Ganga has Bhagirathi as the head water which is fed by the Gangotri glacier.

(iv) Name two headstreams of the Ganga. Where do they to form the Ganga?
Answer. The two headstreams of the Ganga are the Alaknanda and the Bhagirathi and they both meet to form the Ganga at Devprayag.

(v) Why does Brahmaputra in the Tibetan part have less silt despite a longer course?
Answer. Called river Tsangpo in Tibet, Brahmaputra has very little volume of water. So it obviously carries little silt. But once it enters India, Brahmaputra is fed by heavy rains, and it carries lot of water and silt.

(vi) Which two peninsular rivers flow through troughs? What features do they form while entering the sea?
Answer. The two rivers that flow through troughs are Narmada and Tapi. They form estuaries while entering the sea.

(vii) Give five economic benefits of rivers and lakes.
Answer. Role of rivers in the economy :
(a) Rivers create alluvial soils.
(b) River irrigation is the backbone of agriculture in areas that have insufficient rainfall.
(c) Many industrial processes depend on river water as a coolant and for generation of hydroelectricity.
(d) Rivers provide inland channels for transport.
(e) Rivers provide fisheries, scope for developing adventure sports like rafting and entertainment joints.
Lakes like the Sambhar Lake provide edible salt. They also help develop tourism and provide recreation.

Question.3. Below are given names of a few lakes of India. Group those under two categories — natural and created by human beings.
(a) Wular
(b) Dal
(c) Nainital
(d) Bhimtal
(e) Gobind Sagar
(f) Loktak
(g) Barapani
(h) Chilika
(i) Sambhar
(j) Rana Pratap Sagar
(k) Nizam Sagar
(l) Pulicat
(m) Nagarjuna Sagar
(n) Hirakud
Answer. Natural Lakes: Wular, Dal, Nainital, Bhimtal, Chilika, Pulicat, Sambhar, Barapani, Loktak
Created by human beings: Gobind Sagar, Hirakud, Rana Pratap Sagar, Nagarjuna Sagar, Nizam Sagar

Question.4. Discuss the significant differences between the Himalayan and the Peninsular rivers.
Answer.

The Himalayan RiversThe Peninsular Rivers
1. The Himalayan rivers are perennial in nature. They are fed by the melting snow and glaciers of the lofty ranges supplemented by monsoon rains. Hence, the rivers flow throughout the year.1. The Peninsular rivers are non-perennial in nature. They are fed by monsoon rains and have heavy flow during rainy season followed by reduced flow during dry season. So they are seasonal rivers.
2. The Himalayan rivers have long course from their sources in the mountains to the sea. 2. The Peninsular rivers have shorter and shallower courses as compared to their Himalayan counterparts.
3. The Himalayan rivers rise in the Himadri, Himachal or Shivalik section of the Himalayas and form the Northern Plains with their deposition of alluvium.3. Most of the rivers of Peninsular India originate in the Western Ghats and flow towards the Bay of Bengal. However, some of them originate in the Central Highlands and flow towards west.
4. The Himalayan rivers flow through geologically unstable areas and are of uncertain nature.4. Peninsular rivers originate at much lower altitudes and flow through geologically stable areas.
5. They perform intensive erosional activity in upper course. In middle and lower course they orm meanders, oxbow lakes, extensive flood plains and well developed deltas.5. The Narmada and Tapi are fault-guided rivers. The east-flowing rivers from large f deltas. Meanders are not notable in these rivers.

Question.5. Compare the east-flowing and the west-flowing rivers of the Peninsular Plateau. OR
Why are the rivers of Penisula seasonal ? Give two differences between the west-flowing and east-flowing rivers of Peninsular Plateau.
Answer.

East-flowing RiversWest-flowing Rivers
1. The east-flowing rivers have deltas at their mouth.1. The west-flowing rivers do not have deltas at their mouth. They form estuaries.
2. All rivers east-flowing drain into the Bay of Bengal.2. All west-flowing rivers merges into the Arabian Sea.
3. All there rivers passed through a varied topography, i.e. hills, plains, plateaus etc.3. These rivers are flowed through the rift valley.
4. Most rivers are fed by many east-west flowing long tributaries.4. A few small tributaries joining at right angles are only found.

Question.6. Why are rivers important for the country’s economy?
Answer.

  • Rivers are the lifelines of a nation. Rivers have been of fundamental importance in the settlement and progress of man throughout the human history.
  • The rivers form broad, fertile alluvial plains that have been the cradle of human civilisation.
  • Water from the river is a basic natural resource, essential for various human activities. They provide water for domestic use. Rivers provide water for irrigation that helps to develop agriculture in the surrounding area.
  • The fertile soil of the riverine plain, abundant supply of water and the flat land provides opportunities for the development of agriculture. In an agricultural country like India, rivers play a major role in shaping the country’s economy.
  • Rivers supply water for industrial use. Rivers provide for a cheap mode of transportation, inland navigation.
  • Hydro-electricity harnessed from river water supplies power to our industries, to our homes and to our agricultural fields. Integrated water management of rivers through River Valley Projects by building dams provide hydro-electricity, water for irrigation, inland navigation, fishing, recreation etc.

Hence, rivers are of prime importance in the flourishing of a country’s economy.

Map Skills

Question.1. (i) On an outline map of India mark and label the following rivers : Ganga, Satluj, Damodar, Krishna, Narmada, Tapi, Mahanadi, and Brahmaputra.
(ii) On an outline map of India mark and label the following lakes : Chilika, Sambhar, Wular, Pulicat, Kolleru.
Answer.map-skills-chap-3-q1

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