25 August 2015

Class 9th Chapter : Drainage (NCERT Solution)

CBSE NCERT Class IX (9th) | Social Studies | Geography

Chapter  : Drainage


Q.1.What    are    perennial    and    non-perennial    rivers?    Give    reasons    why    the    Himalayan    region consists of perennial rivers.
Ans.1. The rivers that flow throughout the year are termed as perennial rivers. They have more or lesseven flow throughout the year, e.g., the Ganga.
1.    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.
2.    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.
4. 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.

Q.2. Why  is  the  Godavari  often  referred  to  as  the  'Dakshin  Ganga'?  Write  a  note  on   the   river Godavari and its tributaries.
Ans. 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 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.

Q.3. ow are salt lakes formed? Give examples of salt lakes in India.
Ans. Lakes which have water with high salt content are called salt lakes. They are usually found in the basins of inland drainage in the regions of arid and semi-arid climate. 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 low depression or a desert basin and form temporary lakes. Such short lived lakes also contain high percentage of salts on account of high rate of evaporation.
An example of such saltwater lake is the Sambhar lake of Rajasthan. The water of this salt lake is used for producing salt.

Q.4. What is a lagoon? How does it differ from a lake?
Ans.  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 rivess 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 on shore winds are also capable of pushing the coastal sand dunes along beaches landwards. They may enclose marshy lagoons.
(i)    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 inland basis.
(ii)   Lagoons have brackish water while a lake may have fresh water or salty water.
(iii) Lagoons are formed due to wind and wave action in the coasts. Lakes may be of tectonic origin or may be formed due to river action, glacial action, and wind. They may also be human-made artificial lakes.

Q.5. What is a gorge? In what type of terrain does a gorge form?
Ans. 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 near 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 in narrow and the sides are steep 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  recent geological period, gorges are common.

Q.6.    What type of channel does the river Brahmaputra have? Write a short note on the formation of this type of channel.
Ans.  The river Brahmaputra has a braided channel in its entire length in Assam.
The north-eastern 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 river- bed 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.

Q.7.    Where are India’s most of the fresh water lakes located and why?
Ans.  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 lip in the mountains. They are known as Cirques. The melting of the glacial snow in later period forms  cirque lakes.
As the lakes have water from snow melt 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.

Q.8.    What is a river basin? Explain briefly.
Ans.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.

Q.9.    Write a note on the river Krishna and its tributaries.
Ans. 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.

Q.10.Name the three Himalayan river system. Give two tributaries of each
Ans. Three Himalayan river systems are :
(I)   The Indus river system          (ii) The Ganga river system          (iii) The Brahamaputra river system. Tributaries  :
(i)Indus  river system  – Satluj,  Beas, Ravi           (ii) Ganga  river system  – Yamuna,Ghaghara, Gandak
(iii) Brahmaputra river system – Dibang,  Lohit, Kenula.

Q.11.What are the  differences  between  east-flowing  and  west-flowing  rivers  of  the  peninsular plateau?
Ans. 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
East-flowing Rivers
1. The east-flowing rivers have deltas at their mouth.
2. All rivers east-flowing drain into the Bay of Bengal.
3. All three rivers passed through a varied topography, i.e. hills, plains, plateaus etc.
4. Most r ivers are fed by many east-west-flowing long tributaries.                                                                    
West-flowing Rivers
1. The west-flowing rivers do not have deltas at their mouth. They form estuaries.
2. All west-flowing rivers merges into the Arabian Sea.
3. These rivers are flowed through the riftvalley.
4. A few small tributaries joining at right angles are only found.

Q-12.What is the difference between tributary and the distributary? Write any three points.
Ans.  A smaller stream joining with the main stream is known as tributary. A tributary is generally carried water and silt to the main river. River Jamuna is an example of tributary of the river Ganga.
A Distributary is formed at the lower course of the river when the main channel of the river gets blocked with silt which forced 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 :
1.    Tributaries can be found in three stages of the river – upper, middle and lower.
2.    It is useful for irrigation and transportation all through.
3.    It brings water and silt from its catchment area.
4.    Tributaries are fast-flowing.
1. It is only found in lower coarses of the river.         2. It only provides a network of transport in the lower course.
3. It deposits silt in its course.                                       4. Distributaries are slow-flowing.


Q.1. What are the differences between the Himalayan rivers and the Peninsular rivers? 
Ans.  The differences between the two main groups of rivers of India are as follows :
The Himalayan 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.
2.     The Himalayan rivers have long course from their sources in the mountains to the sea.
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.
4.     The Himalayan rivers flow through geologically unstable areas and are of uncertain nature.
5.     They perform intensive erosional activity in upper course. In middle and lower course they form meanders, oxbow lakes, extensive flood- plains and well developed deltas.
The Peninsular Rivers
1.   The Peninsular rivers are non-perennial in nature. They are fed by monsoon rains and              have         heavy flow during rainy season fol        lowed by reduced flow during dry season. So they are seasonal rivers.
2.   The Peninsular rivers have shorter and shallower courses as compared to their Himalayan counterparts.
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.   Peninsular rivers originate at much lower altitudes and flow through geologically stable areas.
5.   The Narmada and Tapi are fault-guided rivers. The east-flowing rivers from large deltas. Meanders are not notable in these rivers.

Q.2. Write a note on the Indus Drainage System.
Ans.  The Indus  is one of the longest rivers of the world.
The river Indus rises in Tibet, near lake Mansarovar. Flowing west, it enters India in the Ladakh district of Jammu and Kashmir. A spectacular gorge formed by the Indus marks this part. Several tributaries – the Zaskar, the Nabra, the Shyok and the Hunza – join the Indus in the Kashmir region. The Indus flows through Baltistan and Gilgit and emerges from the mountains at Attock. The tributaries of the Indus – the Jhelum, the Chenab, the Ravi, the Beas and the Satluj – flow partly through Kashmir and Himachal Pradesh and mainly through Punjab.
They join together to enter the Indus near Mithankot in Pakistan. The Indus then flows southwards and eventually reaches the Arabian Sea, east of Karachi. The Indus has a total length of 2900 km. The Indus plain has a very gentle slope. A little over one third of the Indus basin lies in India in the states of Jammu and Kashmir, Himachal Pradesh and Punjab. Major part of its basin lies in Pakistan.

Q.3. Write a note on the Brahmaputra Drainage System.
Ans. The Brahmaputra is one of the longest rivers of the world, but most of its course lies outside India. The river Brahmaputra rises in Tibet east of the Mansarovar lake. The river flows eastwards parallel  to  the Himalayas in its upper course. It is known as Tsangpo in Tibet. Here it carries smaller volume of water and less silt as it is a cold and dry area.
The river takes a ‘U’-turn bend at Namcha Barwa (7757 m) and enters India in Arunachal Pradesh through a gorge. In Arunachal Pradesh, it is known as Dihang. Here it is joined by the Dibang, the Lohit, the Kenula and many other tributaries.
The volume of the river increases and it is known as the Brahmaputra in Assam. The region receives heavy rainfall during the monsoon which increases the volume of water and silt content of the river.  Devastating floods are caused by the river in Assam and Bangladesh every year during the rainy season. The deposition of the silt in the riverbed due to the heavy load, leads to the formation of braided channels intervened by riverine islands.
The Brahmaputra has a braided channel in its entire length in Assam. Many riverine islands like the Majuli, the
world’s largest riverine island, are formed in between the channels.
The Brahmaputra is known as Jamuna in Bangladesh. Here it is joined by the Ganga, known here as Padma. Together they form the Ganga-Brahmaputra Delta known as Sunderbans, and discharge into the Bay of Bengal. 

Q.4.Write a note on the Ganga Drainage System.
Ans.  The Ganga is the longest and the most important river system of India. It  has a total length of over 2500 km. Nearly the entire river basin of the Ganga lies in India with a part of its lowerCourse and delta  in Bangladesh.
The headwaters of the Ganga are called the ‘Bhagirathi’. It is fed by the Gangotri Glacier. It is joined by the Alaknanda at Devaprayag in Uttarakhand. At Haridwar, the Ganga emerges from the mountains and enters the plains. The Ganga is joined by a large number of tributaries.
The Yamuna, a right-bank tributary of the Ganga, rises from the Yamunotri Glacier, flows parallel to the Ganga and joins it at Allahabad. The Ghaghra, the Gandak, the Kosi and the Sarda are the left-bank tributaries of the Ganga.
The other right bank tributaries of the Ganga – the Chambal, the Betwa and the Son come from the peninsular uplands. The Ganga and its tributaries form a major portion of the northernplains.
On account of water availability and fertile soil, it is the most important agricultural region of India. The Ganga develops large meanders in the plains.
The Ganga flows eastwards with the increased volume up to Farakka in West Bengal. The river bifurcates here. Its distributary, the Bhagirathi-Hooghly, flows through the deltaic plains to the Bay of Bengal.
The mainstream flows southwards into Bangladesh. Here it is known as Padma. It is joined by the Brahmaputra. Further downstream it is known as Meghna. Together they form the Ganga- Brahmaputra Delta, also known as Sunderbans delta. It is the world’s largest and fastest growing delta.

Q.5.Write a note on the east-flowing and the west-flowing rivers of Peninsular India.
Ans. The Peninsular Plateau of India is marked by a large number of east-flowing rivers and a few west-flowing rivers.  Most of the major rivers of Peninsular India such as the Mahanadi, the Godavari, the Krishna and the Kaveri and their tributaries flow eastwards.  They rise from the Western Ghats, the highlands of the Deccan Plateau, flow towards east and drain into the Bay of Bengal.
Only two big rivers, the Narmada and the Tapi, with long courses flow westwards in Peninsular Plateau region. They rise from the Satpura range and Amarkantak hills, flow westwards through faults and drain into the Arabian Sea.
The coastal plains between Western Ghats and the Arabian Sea are very narrow. Hence, the west-flowing coastal rivers are short and swift flowing. The Sabarmati, Mahi, Bharathpuzha and Periyar are the west-flowing rivers. The Sabarmati and the Mahi originate in the Central highlands and flow into the Arabian Sea.
The Western Ghats form the main water divide in Peninsular India. The east-flowing rivers have wide basins. They have dendritic drainage pattern with  many tributaries joining them.  They form large deltas at their mouths.
The west-flowing rivers flow between highlands and have elongated courses. They have trellis and rectangular drainage pattern. They flow through rift valleys and are fault guided rivers. They form estuaries at their mouths. The west-flowing rivers do not form deltas