Class 9 Geography Chapter 1 Question Answers - Contemporary India - I

Q1. What are perennial and non-perennial rivers? Give reasons why the Himalayan region consists of perennial rivers. (Important)

The rivers that flow throughout the year are termed as perennial rivers. They have more or less even flow throughout the year, e.g., the Ganga.

The rivers that do not flow throughout the year are termed as non-perennial rivers. They are seasonal rivers that flow mainly during the rainy season and dwindle during the dry period, e.g., the Subarnarekha.

The rivers of the Himalayan region are perennial in nature. They have their sources in the snow fields and glaciers of the Himalayas which supply water to these rivers throughout the year. During monsoons the Himalayas receive very heavy rainfall and rivers discharge heavy flow of water. During dry periods the rivers are fed by the melting snow and glaciers of the lofty great Himalayan range. Hence, the Himalayan rivers flow throughout the year.Perennial vs Non-perennial Rivers

Q2. Why is the Godavari often referred to as the 'Dakshin Ganga'? Write a note on the river Godavari and its tributaries. (Important)

The Godavari is the largest Peninsular river. It has a length of 1500 km. It has the largest drainage basin amongst the Peninsular rivers. Its drainage basin covers parts of Maharashtra, Madhya Pradesh, Orissa and Andhra Pradesh. On account of its dominating length and the extent of area it covers, the Godavari is known as the ‘Dakshin Ganga’. The Godavari rises from the slopes of the Western Ghats in the Nasik district of Maharashtra. It flows eastwards and drains into the Bay of Bengal. Nearly half of its drainage basin lies in Maharashtra. 

The Godavari is joined by large tributaries–the Wainganga, the Penganga and the Manjra. The Purna, the Wardha and the Pranhita are its other tributaries.

Godavari River

Q3. How are salt lakes formed? Give examples of salt lakes in India.

Lakes which have water with high salt content are called salt lakes. They are usually found in the basins of inland drainage in regions of arid and semi-arid climates. Such lakes are seasonal in nature.

Hollows may be created in the deserts due to the deflation action of the winds. These may reach the groundwater level which seeps out into these depressions. Small shallow lakes are formed which become salt lakes due to excessive evaporation.

Sometimes short, intermittent streams drain into a low depression or a desert basin and form temporary lakes. Such short-lived lakes also contain a high percentage of salts on account of the high rate of evaporation.

An example of such a saltwater lake is the Sambhar lake of Rajasthan. The water of this salt lake is used for producing salt.

Q4. What is a lagoon? How does it differ from a lake?

Lagoon is a stretch of brackish or salt water separated from the sea by a sandbank, bars, reefs, etc. The action of wind and waves along coasts builds spits and bars in the inlets of seas isolating lagoons from the sea. They are commonly found off the deltas of large rivers like the Ganges, the Mahanadi, etc.

The Chilika lake of Orissa, the Pulicat lake of Tamil Nadu and the Kolleru lake of Andhra  Pradesh are lagoons.

• Strong onshore winds are also capable of pushing the coastal sand dunes along beaches landwards. They may enclose marshy lagoons.
  Lagoons are found only in coastal areas, usually near the mouths of rivers, while lakes may be formed in any geographical location, in highlands or in an inland basis.
• Lagoons have brackish water while a lake may have freshwater or salty water.
• Lagoons are formed due to wind and wave action in the coasts. Lakes may be of the tectonic origin or may be formed due to river action, glacial action, wind. They may also be human-made artificial lakes.

Q5. What is a gorge? In what type of terrain does a gorge form?

A gorge is a very steep-sided, narrow river valley. It is found in the mountains in the upper courses of the rivers. They are nearly I-shaped in appearance. In the upper course, the river is very swift as it descends down the steep slopes of the mountains. Vertical corrosion or down cutting is the predominant action of the river here. In areas where the rocks are very hard or resistant, the valley that develops is narrow and the sides are steeply rising almost vertically. Such narrow river valleys are called gorges. Thus, gorges are found in mountainous terrain with resistant rocks. They are usually found in the upper reaches of the river in high mountains, e.g. the Indus Gorge, the Brahmaputra Gorge. Gorges are features of youthful topography. In the Himalayas where the land has been uplifted in the recent geological periods, gorges are common.

Q6. What type of channel does the river Brahmaputra have? Write a short note on the formation of this type of channel.

The river Brahmaputra has a braided channel in its entire length in Assam. The northeastern part of India is a region of high rainfall. Assam receives heavy rainfall during the monsoons. This increases the volume of water in the Brahmaputra river. On account of rapid erosion, the river carries a considerable amount of silt. The silt is deposited in the riverbed when the load becomes excessive. As a result, the river splits into several complicated channels called braided channels. The channels frequently shift position. Many big and small river islands are located in between the braided channels. The Majuli Island on the Brahmaputra is the world’s largest, riverine island. It has, however, been broken due to floods.

Q7. Where are India’s most freshwater lakes located and why?

Most of the freshwater lakes of India are located in the Himalayan region. The lofty ranges of the Himalayas are snow-covered and have many glaciers. Glacial activity results in the formation of circular hollows lips in the mountains. They are known as Cirques. The melting of the glacial snow in later periods forms cirque lakes. As the lakes have water from snowmelt they are freshwater lakes, e.g., Pangong lake in Ladakh. Tectonic activity in the Himalayan region also results in the formation of depressions. They are filled with melting snow forming lakes of tectonic origin, e.g., the Wular lake in Jammu and Kashmir, which is the largest freshwater lake in India. The Dal Lake of Srinagar, Bhimtal and Nainital of Uttarakhand, Loktak Lake of Manipur and Barapani Lake of Meghalaya are some other important freshwater lakes. All are located in the Himalayan region and the Purvanchals.

Q8. What is a river basin? Explain briefly.

The area drained by a single river system, comprising a main river and its tributaries, is called its drainage basin or river basin. The term drainage describes the river system of an area. Small streams flowing from different directions come together to form the main river. It has number of tributaries and distributaries. The river ultimately drains into a large water body such as a lake or a sea or an ocean. The area drained by the main river, its tributaries and distributaries is termed as the river basin. The river Ganga has the largest river basin in India. The river Indus has a larger river basin but most of it lies outside India.

Q9. Write a note on the river Krishna and its tributaries.

The river Krishna rises from a spring near Mahabaleshwar. It flows eastwards to the Bay of Bengal. It has a length of about 1400 km, which makes it the second longest river of Peninsular India after Godavari which has a length of 1500 km. The Tungabhadra, the Koyna, the Bhima, the Ghatprabha and the Musi are important tributaries of the river Krishna. The drainage basin of the river Krishna lies in Maharashtra, Karnataka and Andhra Pradesh.

Q10. Name the three Himalayan river systems. Give two tributaries of each. (CBSE 2010)

Three Himalayan river systems are:

• The Indus river system
• The Ganga river system
• The Brahamaputra river system.

Tributaries:

• Indus river system – Satluj, Beas, Ravi
• Ganga river system – Yamuna, Ghaghara, Gandak
• Brahmaputra river system – Dibang, Lohit, Kenula.

Q11. Which of the factors mainly controls the drainage system of the Indian subcontinent? Into which major groups are the Indian rivers divided? Write three points of difference between the two.  (CBSE 2010)

The drainage system of the Indian subcontinent are mainly controlled by the broad relief features. The Indian rivers are divided into two major groups:

• The Himalayan rivers and
• The Peninsular rivers.

Points of difference :

• The Himalayan rivers mostly originate in the Himalayan ranges whereas the Peninsular rivers mostly originate in the Western Ghats
• The Himalayan rivers are perennial whereas the Peninsular rivers are seasonal
• The Peninsular rivers have shorter and shallower courses in comparison to the Himalayan rivers.

Q12. Why are lakes of great value to human beings? Explain any three reasons. 

(CBSE 2010)

Lakes are of great value to human beings.

• A lake helps to regulate the flow of a river. During heavy rainfall, it prevents flooding. During dry season, it helps to maintain an even flow of water.
• Lakes are also used for developing hydel power.
• Lakes help develop tourism and provide recreation.

Q13. Write any three features of the rivers originating in the Himalayas. (CBSE 2010)

Three main features of the Himalayan rivers are:

• Most of them are perennial.
• They have long and deep courses from their source to the sea.
• They perform intensive erosional activity in their upper courses and carry huge loads of silt and sand.

Q14. What is a lake? How are lakes formed?   (CBSE 2010)

A lake is an area of water surrounded by land on all sides.

• There are lakes which are formed as a result of action of glaciers and ice sheets, while the others have been formed by wind, river action, and human activities.
• Some lakes are formed as a result of the tectonic activity. For example, Wular Lake in Jammu and Kashmir.
• The damming of rivers for the generation of hydel power has also led to the formation of lakes.

Q15. Which three river systems form the Himalayan river systems? [2010 (T-1)]

The Indus, Ganga and Brahmaputra have formed the three major Himalayan river systems of the country.

Q16. Describe any three important features of the river Brahmaputra. [2010 (T-1)]

The three important features of the river Brahmaputra are as follows:

• It passes through a high rainfall region and therefore carries a large volume of water and silt.
• It has braided channel in its entire length in Assam and forms many riverine islands.
• In rainy season, the river overflows it banks causing widespread floods in Assam and Bangladesh.

Q17. How does a river affect the economy of a country? [2010 (T-1)]

Water from the rivers is a basic natural resource. It is essential for various human activities. Therefore, river banks have attracted settlers of very ancient times. These settlements in course of time become cities. In India, rivers are used for irrigation, navigation and power generation besides agriculture. The agriculture is the major source of livelihood of the population and hence its role in the economy is a great.

Q18. What is the name of Brahmaputra in Tibet and Bangladesh? Give one feature of each. [2010 (T-1)]

Brahmaputra is known as the Tsangpo in Tibet and Jamuna in Bangladesh. One important feature of Brahmaputra in Tibet is that it carries a smaller volume of water and less silt as it passes through a cold and dry area in Tibat. In Bangladesh, however, in rainy season the river overflows its banks, carries much water and causeds widespread devastation by floods including siltation in the riverbed.

Q19. What are the differences between east-flowing and west-flowing rivers of the peninsular plateau? [2010 (T-1)]

The major rivers of the peninsular the the Mahanadi, the Godavari, the Krishna etc. are flowing eastward and merges into the Bay of Bengal. Only the river Narmada and Tapti are flowing towards west and merge into the Arabian Sea. The essential differences between the two rivers are as follows: 

Q21. What are the causes of river pollution? Suggest some ways to overcome them? [2010 (T-1)]

The main cause of river pollution is the dumping of untreated sewage and industrial effluents into the rivers. This affects the quality of water.

Q20. What is the difference between the tributary and the distributary? Write any three points. [2010 (T-1)]

• A smaller stream joining with the mainstream is known as a tributary. A tributary is generally carried water and silt to the main river. River Jamuna is an example of a tributary of the river Ganga.
• A Distributary is formed at the lower coarse of the river when the main channel of the river gets blocked with silt which forced the river to open branches. The Bhagirathi-Hooghly is a distributary of the river Ganga. The main function of the distributary is to distribute water through newly opened channels.

The three basic differences between tributaries and distributaries are given below:

Q21. What are the causes of river pollution? Suggest some ways to overcome them? [2010 (T-1)]

The main cause of river pollution is the dumping of untreated sewage and industrial effluents into the rivers. This affects the quality of water.

• Recycling and reuse of wastewater are to be done to check wastewater.
• Wastewater is to be released after proper treatment.
• All outlets of effluents from industrial and domestic sources should be diverted to elsewhere.

Q22. Describe the three main features of the Narmada Basin. [2010 (T-1)]

The river Narmada emerges from the Amarkantak hills in Madhya Pradesh.

• It flows towards the west in a rift valley formed due to faulting.
• It creates many picturesque places like the Marble Rocks near Jabalpur and Dhuadhar Falls.
• All the tributaries of the Narmada are very short and most of them join at right angles to the mainstream.