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Chapter 3 Drainage Questions NCERT Solutions for class 9 SST Geography

What is meant by the water divide? Give an example.
Any elevated area, such as a mountain or upland, separates two drainage basins. Such upland is known as the water divide. Ambala is located on the water divide between the Indus and the Ganga river systems.

Which is the largest river basin in India?
The Ganga basin is the largest basin in India.

Where do the rivers Indus and Ganga have their origin?
The headwaters of the Ganga called the ‘Bhagirathi’ is fed by the Gangotri Glacier and joined by the Alaknanda at Devaprayag in Uttaranchal. At Haridwar, the Ganga emerges from the mountains on to the plains. The Indus flows through Baltistan and Gilgit and emerges from the mountains at Attock.

Name the two headstreams of the Ganga. Where do they meet to form the Ganga?
Alakananda and Bhagirathi are the two headstreams of the Ganga. They meet at Devaprayag.

Why does the Brahmaputra in its Tibetan part have less silt, despite a longer course?
The Brahmaputra river, which is known as Tsangpo in Tibet, receives a very little volume of water in Tibet so it has less silt there. On the other hand, this very river when enters India it passes through such a region which receives heavy rainfall. As such in India, it carries a large volume of water and a larger amount of silt.

Which two Peninsular rivers flow through trough?
Narmada and Tapi are the two Peninsular rivers, which flow through the trough.

Discuss the significant difference between the Himalayan and the Peninsular rivers.
The Himalayan Rivers The Peninsular or Deccan Rivers
1. The Himalayan rivers rise in the snow-covered mountains as such they flow throughout the year. The mountains in which the Deccan rivers rise are not snow-covered. Hence they dry up in summer.

2. The Himalayan rivers flow in leveled Northern Plains. Therefore, they are quite useful for navigation and irrigation. The Peninsular rivers flow on the uneven rocky surface. Therefore they are neither navigable nor useful for irrigation.

3. The Himalayan rivers bring with them fertile alluvium which they deposit in the Indo-Gangetic Plains. The Peninsular rivers do not bring with them enough alluvium. As the current is swift so the deposition activity is negligible.

4. Canals have been dug to use the water of these rivers for irrigation. As the terrain is rocky and the banks of these rivers are high, canals cannot be dug. However, dams are built to store the floodwater for irrigation with the help of small channels.

5. Many important towns and centres of trade are situated on the banks of these rivers. Very few important towns and centres of trade are situated on the banks of these rivers.

6. The porous soil absorbs a lot of water, which is later on used as groundwater by digging wells and tube wells for domestic and irrigation purposes. The rocky soil does not absorb any water. Hence no wells can be dug. All the water flows down the sea at one and the same time.

Compare the east-flowing and the west-flowing rivers of the Peninsular plateau.
East Flowing Rivers
The Mahanadi, the Godavari, the Krishna, and the Kaveri are the main east flowing rivers of Peninsular India. These rivers drain in the Bay of Bengal. These rivers make deltas at their mouth

West Flowing Rivers.
These rivers have a developed tributary system. Their tributaries are comparatively large in size. These rivers flow through not very deep channels.

The Narmada and the Tapi are the main west-flowing rivers of Peninsular India. These rivers drain in the Arabian Sea. These rivers enter the sea through estuaries. These rivers are devoid of developed tributary system. Their tributaries are quite small in size. These rivers flow in a trough or a funnel-like narrow but deep channel.

Why are rivers important for the country’s economy?
Rivers have been of fundamental importance throughout human history. Water from the rivers is a basic natural resource, essential for various human activities. Therefore, the riverbanks have attracted settlers from ancient times. These settlements have now become big cities. Make a list of cities in your state, which is located on the bank of a river. Using rivers for irrigation, navigation, hydropower 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.

Drainage Class 9 Important Questions Very Short Answer Type Questions

Question 1.
What is a drainage?
A system of flowing water from the higher level to the lower level.

Question 2.
What is the area drained by a single river system called?
Drainage basin.

Question 3.
What are the different patterns formed by the streams?

  • Dendritic,
  • Trellis,
  • Radial.

Question 4.
Name the two main drainage basins.

  • The Indus Basin,
  • The Ganga-Brahmaputra Basin.

Question 5.
Which type of drainage pattern does an area have where hard and soft rocks exist parallel to each other?
Trellis pattern.

Question 6.
What is a drainage river basin?
The area drained by a single river system is called a river basin or a drainage basin.

Question 7.
What is meant by watershed or a water divide?
The upland or a mountain which separates two adjoining drainage basins is known as a watershed or a water divide, e.g., Ambala.

Question 8.
On what does the stream within a drainage basin depend?

  • Relief,
  • Geological structure,
  • Climatic conditions of the area.

Question 9.
Which is the main water divide in southern India?
Western Ghats.

Question 10.
Zaskar and Nubra are important tributaries of which river?
Indus river.

Question 11.
Name the three main Himalayan river systems.

  • The Indus River System ,
  • The Ganga River System,
  • The Brahmaputra River System.

Question 12.
What is a gorge? HOTS
A deep narrow opening formed by the river in the upper course, e.g., the gorge formed by the river Indus.

Question 13.
Name three depositional features formed by the Himalayan rivers.

  • Flood plains,
  • River cliffs,
  • Levee.

Question 14.
Name any four depositional features of the Himalayan rivers in their middle and lower course.

  • Meanders,
  • Oxbow lakes,
  • Delta,
  • Flood plains.

Question 15.
Where does the river Indus rise?
In Tibet, near the Mansarovar lake.

Question 16.
Name the tributaries of river Indus.
The Zaskar, the Shyok, the Nubra and the Hunza.

Question 17.
Name the two main groups into which the river systems of India are classified.

  • The Himalayan rivers,
  • The Peninsular rivers.

Question 18.
Why are the Himalayan rivers perennial?

  • Most of the Himalayan rivers originate from the glaciers.
  • They get water from the rainfall as well as from the glaciers.

Question 19.
Name the city located on the water divide between the Indus and the Ganga river systems.

Question 20.
Which states are benefited by the Indus system?
Punjab, Haryana and western parts of Rajasthan.

Question 21.
What is the Indus water treaty?
It is a treaty signed between India and Pakistan. According to this treaty, India can use only 20% of the total water carried by the Indus river system.

Question 22.
Name the plan which was launched to reduce pollution in the river Ganga.
The Ganga Action Plan.

Question 23.
Name any two tributaries of Ganga which rise in the Nepal Himalayas.
The Ghaghara and Kosi.

Question 24.
Which is the northernmost point of the Ganga Delta?
The Ganga flows eastwards til Farakka in West Bengal. This is the northernmost point of the Ganga delta.

Question 25.
Which is the largest river basin in India?
The Ganga Basin.

Question 26.
What is the length of the Ganga?
About 2500 km.

Question 27.
Name two headstreams of the Ganga. Where do they unite?

  • Bhagirathi,
  • Alaknanda.

They meet at Devprayag.

Question 28.
Name the city at which the Ganga enters the plains from the Himalayas.

Question 29.
Name the tributaries of river Ganga which enter the northern plains from Nepal.
Ghaghara, Gandak and Kosi.

Question 30.
Name the two main right bank tributaries of the Ganga.
The Yamuna and the Son.

Question 31.
What is the major concern of the Ganga Action Plan?
Rising pollution in the Ganga is the major concern of the Ganga Action Plan.

Question 32.
What is the name of the Brahmaputra river in Tibet?

Question 33.
From where does the river Brahmaputra arise?
In Tibet east of Mansarover lake.

Question 34.
What are perennial rivers?
The rivers which have water throughout the year are called the perennial rivers.

Question 35.
Which is the largest Peninsular river? Where does it originate from?
Godavari, it arises from the Nasik district of Maharashtra.

Question 36.
Name any two Peninsular rivers which flow through the rift valley.
The Narmada and the Tapti.

Question 37.
Which is the main watershed in Peninsular India?
The main watershed in Peninsular India is formed by the Western Ghats.

Question 38.
Name the major rivers of the Peninsular India.
The Mahanadi, the Godavari, the Krishna and the Kaveri.

Question 39.
Name any two small river basins of the peninsular region.

  • The Pennar, and
  • The Mahi.

Question 40.
Name two large rivers of India which flow into the Arabian Sea.
The Narmada apd the Tapti.

Question 41.
Which type of drainage pattern is made by Narmada river?

Question 42.
What is the msyor reason for the nonperennial nature of the peninsular rivers?
Rainfall is the only source of water for these rivers.

Question 43.
From where does the Narmada river rise?
Near Amarkantak, in Madhya Pradesh.

Question 44.
In which hills does the Tapi river rise?
Satpura ranges.

Question 45.
From where does the Tapti river arise?
In the Betul district of Madhya Pradesh.

Question 46.
Name the states through which the Tapti river flows.
Madhya Pradesh, Gujarat and Maharashtra.

Question 47.
In which state does the largest part of the Godavari basin lie?

Question 48.
Which river is known as Dakshin Ganga?

Question 49.
Name the tributaries of Godavari river.
The Purna, the Wardha, the Pranhita, the Manjra, the Wainganga and the Pehganga.

Question 50.
Why is the Godavari river called the Vridha Ganga or the Dakshin Ganga?
It is because of its large size and the huge extent.

Question 51.
Name the tributaries of Krishna.
The Tungabhadra, the Koyna, the Ghatprabha, the Musi and the Bhima.

Question 52.
What is the source of river Yamuna?
Yamunotri glacier in the Himalayas.

Question 53.
Which city is located at the confluence of the Yamuna and the Ganga?

Question 54.
Name the five rivers of Punjab from which the water falls into the Indus.
The Sutlej, the Beas, the Ravi, the Chenab and the Jhelum.

Question 55.
What is a canyon?
It is a deep gorge with steep sides containing many streams, e.g., the Grand Canyon of the Colorado river.

Question 56.
Where are most of the fresh water lakes located?
In the Himalayan region.

Question 57.
Which is the largest natural freshwater lake of India? HOTS
The Wular lake in Jammu and Kashmir.

Question 58.
Name a lake which has been formed due to tectonic activities.
The Wular lake.

Question 59.
Name two salt water lakes on the eastern coast of India.

  • The Chilika Lake,
  • The Pulicat Lake.

Question 60.
Write two causes responsible for the increase in demand of water.

  • Growing population,
  • Urbanisation.

Question 61.
Write any two uses of the river water.
River water is used for farming, drinking, domestic and industrial uses.

Question 62.
Write any two causes of pollution of water of the Ganga river.

  • Disposal of raw sewage and industrial wastes from towns and cities.
  • Reduction in water flow due to abstraction of water for irrigation from the Ganga through canals.

Drainage Class 9 Important Questions Short Answer Type Questions

Question 1.
Describe any three features of Himalayan rivers.
Features of the Himalayan Rivers:

  • They are perennial in nature.
  • They have large basins.
  • They perform intensive erosion activity in their upper course and carry huge load of silt and sand.

Question 2.
Define a river system and describe two characteristics of river Indus.
A river along with its tributaries is called a river system.
Characteristics of River Indus:

  • River Indus rises in Tibet near Mansarovar lake.
  • Its total length is 2,900 km and is one of the longest rivers of the world.
  • Majority flows through Pakistan and help in agricultural activities.
  • The main tributaries of Indus are Nubra, Hunza, Sulley, Beas, Ravi, Chenab, Jhelum. (any two)

Question 3.
Write a short note on the Brahmaputra river system.
Describe the three main features of river Brahmaputra.

  • The Brahmaputra originates in Tibet where it is known as Tsangpo.
  • It flows eastwards parallel to the Himalayas, but it takes a U-tum around the Namcha Barwa and enters India in Arunachal Pradesh.
  • It is responsible for creating a havoc of floods in Assam and Bangladesh.
  • This river receives less volume of water and has less silt in Tibetan part, but it carries a large volume of water and silt in India.
  • It has a braided channel in most of its length in Assam with a few large islands within the channel.

Question 4.
Describe any three features of Ganga-Brahmaputra delta.
Describe the features of the Ganga plain.

  • The Sundarban Delta derived its name from the Sundari tree which grows well in marshland.
  • It is formed by the rivers Ganga and the Brahmaputra.
  • It is the world’s largest and fastest growing delta.
  • It is also the home of Royal Bengal Tiger.

Question 5.
Why do the Himalayan rivers get flooded every year? What are its advantages?

  • The Himalayan rivers receive water from the melted snow from the lofty mountains as well as from rain.
  • During monsoons, due to heavy rainfall, these rivers get flooded every year.


  • The Himalayan rivers flood parts of the northern plains enfiching the soil for the extensive agricultural lands.
  • Various food crops and cash crops are grown in these fertile lands.

Question 6.
What progress has been made in the Ganga Action Plan?

  • Sixty-nine schemes have been completed with positive results.
  • Trees have been planted in badly eroded portions.
  • Check dams have been repaired in the upper reaches of the river.
  • Interception and diversion of several major drains carrying sewage and industrial wastes to the river in some cities like Varanasi, Kanpur, Patna have reduced the pollution level.
  • Turtles and the Gangetic dolphins which had disappeared for several years have now reappeared in Varanasi and other places.

Question 7.
Why are most of the Peninsular rivers draining into the Bay of Bengal? Give reasons. Name the two rivers draining into the Arabian Sea.
(a) The main water divide in Peninsular India is formed by the Western Ghats, which runs from north to south close to the western coast..
(b) The Deccan Plateau is higher in the west and slopes gently eastwards.
Thus, most of the peninsular rivers such as Mahanadi, the Godavari, the Krishna and the Kaveri flow eastwards and drain into the Bay of Bengal.
(ii) The river Narmada and river Tapi drain into the Arabian Sea.

Question 8.
Which two rivers of Peninsular India form estuaries? Name the states in which these rivers drain the water.

  • The river Narmada and the Tapi form estuaries.
  • The Narmada basin covers parts of Madhya Pradesh and Gujarat.
  • The Tapi basin covers parts of Madhya Pradesh, Gujarat and Maharashtra.

Question 9.
Why are Peninsular rivers seasonal in nature? Give any three reasons.

  • The flow of Peninsular rivers is dependent on rainfall.
  • The Peninsular rivers have shorter and shallower courses as compared to their Himalayan counterparts.
  • The tributaries are very short and less in number and bring quite less amount of water which hardly increases the amount of water of the main river. Therefore, during the dry season, even the large rivers have reduced flow of water in their channels.

Question 10.
Which two peninsular rivers flow westward? Mention one similarity and one difference between these two rivers.
Narmada and Tapi.

  • These rivers flow through rift valley. .
  • The tributaries of these rivers are small in size.


  • Tapi is the second largest river of Peninsular India and Narmada is the fifth largest river.
  • Narmada river forms an estuary before entering into the Gulf of Khambhat. On the other hand Tapi does not form an estuary.

Question 11.
Describe the main features of Narmada Basin.

  • All the tributaries of the Narmada are very short and most of these join the mainstreams at right angle.
  • The river forms an estuary before entering into the Gulf of Khambhat.
  • The river Narmada rises in the Amarkantak hills and flows towards the west in a rift valley formed due to faulting.

Question 12.
Describe the main features of Tapi Basin.

  • It is the second largest river of the peninsular, rises in the Satpura ranges, in the Betul district of Madhya Pradesh.
  • It also flows in a rift valley parallel to the Narmada but it is much shorter in length.
  •  Its basin covers parts of Madhya Pradesh, Gujarat and Maharashtra.

Question 13.
Describe any three important features of the Krishna Basin.

  • The river Krishna rises from a spring near Mahabaleshwar. It flows for about 1400 kms.
  • The Tungabhadra, the Koyana, the Ghatprabha, the Musi and the Bhima are some of its tributaries.
  • Its drainage basin is shared by Maharashtra, Karnataka and Andhra Pradesh.

Question 14.
Why is the Godavari river also known as ‘Dakshin Ganga’? HOTS

  • The Godavari is the largest peninsular river.
  • Its drainage basin is also the largest among the peninsular rivers. The basin covers parts of Maharashtra, Madhya Pradesh, Odisha and Andhra Pradesh.
  • The Godavari is joined by a number of tributaries such as the Purna, the Wardha, the Pranhita, the Manjra, the Wainganga and the Penganga.
  • Because of its length and the area it covers, it is also known as the ‘Dakshin Ganga’.

Question 15.
Describe any three important features of the Mahanadi Basin.

  • The Mahanadi rises in the highlands of Chhattisgarh.
  • It flows through Odisha to reach the Bay of Bengal. The length of the river is about 860 kms.
  • Its drainage basin is shared by Maharashtra, Chhattisgarh, Jharkhand and Odisha.

Question 16.
Describe any three important features of the Kaveri Basin.

  • The Kaveri rises in the Brahmagri range of the Western Ghats and it reaches the Bay of Bengal in south of Cuddalore, in Tamil Nadu.
  • Its main tributaries are Amravati, Bhavani, Hemavati and Kabini.
  • Its basin drains parts of Karnataka, Kerala and Tamil Nadu.

Question 17.
Mention any three similarities between the Himalayan rivers and Peninsular rivers.

  • Both the river systems form delta.
  • Himalayan and Peninsular rivers both have their large drainage basins.
  • The rivers of both the regions are joined by several tributaries which increase the volume of water and silt of the main river. For example,
    Himalayan River: The tributaries of river Ganga are Yamuna, Kosi, Gandak etc.
    Peninsular River: The tributaries of river Godavari are the Purna, the Wardha, the Pranhita, the Manjra, the Wainganga and the Penganga.

Question 18.
Why rivers are regarded as the lifelines of human civilization?
Rivers are regarded as the lifelines of human civilization because:

  • Most of the civilizations have developed along the river valley. For example, Indus Valley Civilization near river Indus and Mesopotamian Civilization near river Euphrates and river Tigris.
  • River provides settled life as growth of food and crops is possible and convenient near rivers.
  • People have always used rivers to travel across places and for the transport of men and material from one place to another.

Question 19.
What do you think will happen to the human beings in the absence of scarcity of freshwater? HOTS
Water is a vital nutrient that constitutes 75% part in our body. It removes waste materials and circulates and replenishes nutrients in our body. Since sea water is salty in nature, it cannot substitute fresh water. Beside this, animals and plants are also dependent on water for their survival.

Drainage Class 9 Important Questions Long Answer Type Questions

Question 1.
Describe the four drainage patterns.
The four drainage patterns are as follows:

  • Dendritic: The dendritic patterns develop where the river channels follows the slope terrain. The stream with its tributaries 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. A Trellis drainage pattern develops where hard and soft rocks: exist parallel to each other.
  • Rectangular: A rectangular drainage pattern develops on a strongly-jointed rocky terrain.
  • Radial: The radial pattern develops when streams flows in different directions from a central peak or dome-like structure.

Question 2.
“Rivers constitute the most useful natural resources.” Support the statement with five suitable examples. HOTS
Rivers are the most important natural resources because

  • Rivers provide water for survival and growth of all organisms.
  • Rivers provided ideal conditions for the early man to lead a settled life.
  • Rivers have built flood plains, deltas and provide fertile soil for agriculture.
  • Water from rivers is used for drinking, irrigation and for generating hydro- electricity.
  • Man is able to supplement his food supply with the fish in the rivers. Rivers also serve as natural waterways.
  • World’s earliest civilization developed in the river valleys, e.g., Nile Valley civilization, Indus Valley civilization etc. River Valleys are the world’s best agricultural lands, and are densely populated regions.

Question 3.
Explain the main features of the rivers originating from the Himalayas.

  • Most of the Himalayan rivers are perennial. It means that they have water throughout the year.
  • The Himalayan rivers have long courses from their source to the sea.
  • These perform intensive erosional activity in their upper courses and carry huge loads of silt and sand.
  • They have cut through the mountains making gorges.
  • They also have well-developed deltas.

Question 4.
Write the main features of the Ganga system.

  • The Ganga has two headstreams-the Alaknanda and the Bhagirathi. They join together at Devprayag.
  • From the Himalayas the Ganga enters the plains at Haridwar. It is joined together by a large number of tributaries like Ghaghara, the Gandak and the Kosi.
  • The Yamuna and the Son are the two main right bank tributaries of the Ganga.
  •  The Ganga enters Bangladesh as Padma. It flows southward through Bangladesh, and is joined by the Brahmaputra and is known as the Jamuna. After receiving Meghna, it is known as the Meghna.
  • The length of the Ganga is over 2500 km, and it has the largest basin.

Question 5.
Why does Brahmaputra become a big river on entering India?

  • In Tibet, the Brahmaputra river carries a smaller volume of water and less silt as it is a cold and dry area.
  • It enters India from Arunachal Pradesh and is joined by many tributaries such as the Dibang, the Lohit etc.
  • It passes through a region of high rainfall. Here, the river carries a large volume of water and considerable amount of silt.
  • Every year during the rainy season, the river overflows its banks.
  • Brahmaputra is marked by huge deposits of silt on its bed causing the river bed to rise.

Question 6.
Mention the main features of the Ganga Action Plan.
Main Features of the Ganga Action Plan:

  • Sewage flowing into the river is to be diverted to other locations for treatment and conversion into energy source.
  • Steps have been taken to supply safe drinking water by constructing electric crematoriums and separating bathing Ghats.
  • The diversion of several major drains carrying wastes into the river has been completed in cities like Varanasi, Patna and Kanpur and pollution level has been decreased.
  • Infrastructure capable of diverting and treatment 835 million litres per day of domestic waste or sewage has been created.
  • Ganga Action Plan has been merged with National River Conservation Plan. It now covers 152 towns located along 27 Inter-state rivers in over 16 states.

Question 7.
Distinguish between a Delta and an Estuary.

S.No. Delta Estuary
(i) The triangular deposits made by the river at its mouth form delta. The sharp edge at the mouth of the river devoid any deposits is known as estuary.
(ii) Deltas are formed in the regions of low tide and coastal plains. The regions of high tides and rift valleys witness estuaries.
(iii) Deltas are fertile lands. Estuaries do not have fertile lands.
(iv) The river Ganga, the Krishna, the Godavari, are some of the rivers which form deltas. Narmada and Tapi rivets form estuaries.

Question 8.
Distinguish between perennial and non-perennial rivers.

S.No. Perennial Non-Perennial
(i) These rivers have water throughout the year. These have water only during the rainy season.
(ii) Rainfall and melted snow are the source of water for these rivers. Rainfall is the only source of water for these rivets.
(iii) Most of the Himalayan rivers are perennial. Most of the Peninsular rivers are non-perennial.

Question 9.
Explain the ‘National River Conservation Plan’ (NRCP) in brief.
The activities of Ganga Action Plan (GAP) Phase-I, initiated in 1985, were declared closed on 31st March, 2000. The Steering Committee of the National River Conservation Authority reviewed the progress of the GAP and necessary correction on the basis of lessons learnt and experiences gained from GAP Phase-I. These have been applied to the major polluted rivers of the country under the NRCP.

The Ganga Action Plan (GAP) Phase-II, has been merged with the NRCP. The expanded NRCP now covers 152 towns located along 27 interstate rivers in 16 states. Under this action plan, pollution abatement works are being taken up in 57 towns. A total of 215 schemes of pollution abatement have been sanctioned. So far, 69 schemes have been completed under this action plan. A million litre of sewage is targetedto be intercepted, diverted and treated.

Question 10.
Differentiate between freshwater lakes and saltwater lakes giving examples of each.
Freshwater Lakes:

  • Freshwater lakes are mostly found in the Himalayan region.
  • They are of glacial origin which means that they were formed when glaciers dug out a basin which was later filled with snow melt.
  • The Wular lake in Jammu and Kashmir is the result of the tectonic activity.
  • The Dal lake, Bhimtal, Nainital, Loktak and Barapani are some other important freshwater lakes.

Saltwater Lakes:

  • Spits and bars form lagoons in the coastal areas, e.g., the Chilika lake, the Pulicat lake, the Kolleru lake are the saltwater lakes.
  • Lakes in the regions of inland drainage are the saltwater lakes, e.g., the Sambhar lake in Rajasthan. Its water is used for producing salt.

Question 11.
Why are rivers important for the country’s economy? HOTS
The rivers are important for a country’s economy for the following reasons:

  • Rivers are an integral part of our folklore and folk songs. Water from the rivers is a basic natural resource essential for human, agriculture and industrial activities. This activity in its form is uneconomic but in its long term becomes economic one. For example, Sahitya Academy, transmission of dramas, plays and stories to abroad bags hard currency to India.
  • 80% main stay of population in India on agriculture indicates itself how important the surface water is for Indian economy.
  • Tourism industry has developed by leaps and bounds in each country of the world after globalisation in twenties. This industry bags millions currency in American dollar (i.e., the hard currency).
  • Human nature never does anything without his direct or indirect purpose, objective, mission inherited or hidden therein. Mostly they prefer to earn, to live a peaceful life, to take refuge (nomads, sophisticated) etc. all selfish and not national. However, as seeds are spread on the wings of insects, the literature, culture, activities (positive or negative) sent and transmitted. Gradually, it gives birth to bilateral trade and commodity of countiy is concerned in the countries of the entire world. It is globalisation of economy hence, sprouts in economic activities.

Question 12.
What are the major factors responsible for river pollution? Explain.

  • High Demand of Water: The growing domestic, municipal, industrial and agricultural demand for water from rivers naturally affects the quality of water. As a result, more and more water is being drained out of the river reducing its volume.
  • Industralisadon: A heavy load of untreated sewage and industrial effluents are emptied into the rivers. This affects not only the quality of water but also the self-cleansing capacity of the river. For example, given the adequate streamflow, the Ganga water is able to dilute and assimilate pollution loads within 20 km of large cities. But the increasing urbanisation, and industrialisation do not allow it to happen and the pollution level of many rivers has been rising.
  • Agricultural Pollution: The extensive uses of chemicals in the form of fertilizers and pesticides in agriculture have left the water bodies contaminated with heavy metals. Such heavy metals enter human body through the food we eat, and many of them cause health problems such as cancer.

Question 13.
What are the causes of water pollution? How can it be controlled?

  • The factories discharge their effluents in the nearby rivers, which cause water pollution.
  • The disposal of sewage of urban centres into the rivers is also responsible for water pollution.
  • The overuse of fertilisers and pesticides also pollute the water.
  • Water in the oceans gets polluted by the leakage of oil from oil tankers.

Methods to Control Water Pollution:

  • The waste product from the factories should not be allowed to fall into the rivers.
  • The waste materials should be treated before it is allowed to fall into the water of rivers.
  • Sewage of urban centres should not be allowed into rivers at any cost.
  • The fertilisers and pesticides should not be overused.
  • Oil spills from tankers should not be allowed to enter any water body.
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