Concepts

KEY CONCEPTS

  • Area drained by a single river is called a drainage basin.
  • Any elevated area , such as a mountain or an upland that separates two drainage basins is called water divide.
  • Indian Rivers are divided into two major groups:
    • Himalayan Rivers  ( Perennial : throughout the year)  :- Indus , Ganga and Brahmaputra
    • Peninsular Rivers  ( Seasonal : dependent on rainfall) :-  Originate in the western ghats  and flow towards the Bay of Bengal
  • A river alongwith its tributaries is called  a river system.
  • The Indus River System
    • Indus Water Treaty ( 1960 ) : India can use only 20%  of the total water  of Indus River System.
    • Rises in Tibet  and enters in Ladakh.
    • Several Tributaries: Zaskar , Nubra , Shyok, Hunza

  • 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.

    Lakes

    • 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)

Test your knowledge

(i) In which of the following states is the Wular lake located?

(a) Rajasthan (b) Punjab (c) Uttar Pradesh (d) Jammu and Kashmir

Answer: Jammu and Kashmir

(ii) The river Narmada has its source at

(a) Satpura (b) Amarkantak (c) Brahmagiri (d) Slopes of the Western Ghat

Answer: Amarkantak

(iii) Which one of the following lakes is a saltwater lake?

(a) Sambhar (b) Wular (c) Dal (d) Gobind Sagar

Answer: Sambhar

(iv) Which one of the following is the longest river in Peninsular India?

(a) Narmada (b) Godavari (c) Krishna (d) Mahanadi

Answer: Godavari

(v) Which one amongst the following rivers flows through a rift valley?

(a) Mahanadi (b) Krishna (c) Tungabhadra (d) Tapi

Answer: Tapi

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, which separates two drainage basins is called an upland. Such an upland is also known as a water divide. For example, the water divide between the Indus and the Ganga River Systems.

(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 River origin – Near Manasarovar Lake, Tibet

Ganga River origin – Gangotri glacier in Uttaranchal

(iv) Name the two headstreams of the Ganga. Where do they meet to form the Ganga?

Answer: The two headstreams of the Ganga are Alaknanda and Bhagirathi. They both meet to form Ganga at Devprayag.

(v) Why does the Brahmaputra in its Tibetan part have less silt, despite a longer course?

Answer:  In Tibet, the river carries a smaller volume of water and less silt, as it is a cold and dry area. In India, it passes through a region of high rainfall. Hence, the river carries a large volume of water and a considerable amount of silt.

(vi) Which two Peninsular rivers flow through a trough?

Answer: Narmada and Tapi are the two Peninsular rivers that flow through a trough.

(vii) State some economic benefits of rivers and lakes.

Answer: Rivers have been of fundamental importance throughout human history. Water from rivers is a basic natural resource, essential for various human activities. Therefore, riverbanks have attracted settlers from ancient times. Using rivers for irrigation, navigation and hydropower generation is of special significance — particularly to a country like India, where agriculture is the major source of livelihood for the majority of its population.

3. Below are given names of a few lakes of India. Group them 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) Hirakund

Answer:

Natural Lakes

  1. Wular
  2. Dal
  3. Nainital
  4. Bhimtal
  5. Loktal
  6. Chilika
  7. Pulicat
  8. Sambhar
  9. Barapani

Human-made Lakes

  1. Gobind Sagar
  2. Rana Pratap Sagar
  3. Nizam Sagar
  4. Nagarjuan Sagar
  5. Hirakud

4. Discuss the significant difference between the Himalayan and the Peninsular rivers.

Answer:

Himalayan Rivers

  1. These are perennial rivers.
  2. Receive water from Rain and Snowfall.

Peninsular Rivers

  1. These are seasonal rivers.
  2. Dependent on rainfall. During dry seasons, the rivers get dried up.

5. Compare the east-flowing and the west-flowing rivers of the Peninsular plateau.

Answer:

West flowing rivers

  1. There are only 2 long West flowing rivers – Narmada and Tapi.
  2. They flow into the Arabian Sea.
  3. They have a lesser number of tributaries.
  4. Form estuaries.
  5. Carry lesser sediments.

East flowing rivers:

  1. Many major rivers, Mahanadi, Cauvery, Godavari, Krishna, etc.
  2. They flow into the Bay of Bengal.
  3. Have many tributaries.
  4. Forms Deltas.
  5. Carry larger sediments than West flowing rivers.

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

Answer:

Rivers have been of fundamental importance throughout human history. Water from rivers is a basic natural resource, essential for various human activities. Therefore, riverbanks have attracted settlers from ancient times. These settlements have now become big cities. Using rivers for irrigation, navigation, and hydropower generation are of special significance — particularly to a country like India, where agriculture is the major source of livelihood for the majority of its population.