Blog Details

INTRODUCTION

• A river is a large stream of fresh water flowing downhill within a channel to enter another river or a lake or sea.
• All rivers ultimately receive their water from precipitation, though this relation is not a very simple one.
• The flow of a river depends upon three main factors: the amount and intensity of rainfall, governed by climatic factors
• the permeability of the surface on which it is flowing; and the morphological properties of the drainage basin. The nature of the vegetation cover also plays an important role.
• When water flows in a stream, it is subject to two basic forces: gravity, aimed downstream  and causing the flow; and frictional resistance between the water and the river bed.
• The effect of friction ensures an uneven velocity of water flow in the river. Thus, water near the centre moves the fastest while it is slow near the banks.

PARTS OF RIVER

• The place at which the river begins to flow is called its source. It may be in the melt waters of a glacier, e.g., the Rhone (France), or in a lake.
• The place where the river ends is called a river’s mouth. It is usually in the sea, e.g., the Indus (Arabian Sea) and the Amazon (Atlantic).

(a)    Three sections of a river:

• The upper course representing the stage of youth of a river, called the torrent stage;
• The middle course, representing the state of maturing called the valley, and 
• The lower course, representing the stage of old age and called the plain stage.

(i)    The Torrent stage:

• In the stage of youth, the river flows turbulently in a narrow steep-sided valley whose floor is broken by
• (a) ‘patholes’ or circular depressions in the river bed, caused by pebbles, (b) waterfalls, occurring where the bed of the river becomes suddenly steepened.
• Some deep and narrow valley having very steep sides are called gorges. These are formed where a waterfall retreats upstream. 
• Canyons are large gorges, formed in dry regions where large rivers are actively eroding vertically. A canyon is a deep valley with steep, near vertical sides. 

(ii)    The Valley stage:

• As the valley widens, meanders are formed. A meander is a loop in the course of a river channel.
• Water flows in corkscrew manner, causing erosion on the concave bank and deposition on the convex  bank.

(iii)     The Plain stage: 

• Reaching old age, the river deposits its load into the sea or lake into which it flows.
• The deposited load sometimes collects in the river mouth,
• where it builds up into a low-lying swampy plain called a delta.
• The river divides into several channels due to the depositions at its mouth, called distributaries.

(b)    Work of a River:

• A river does three types of work:
• It erodes, and most erosion takes place in the upper course;
• It transports: a process dominant in the middle course;
• It deposits: depositional process is dominant in the lower course of the river.

(a)    Nile (Africa):

• The longest river, 6690 km;
• White Nile originates from Lake Albert in Uganda and Blue Nile from Ethiopia;
• the two join together at Khartoum in Sudan to form River Nile.
• After flowing through Egypt (the river’s longest course), it falls into the Mediterranean Sea near Alexandria.

(b)    Amazon (South America):

• Originates from the Andes Mountain in Peru; tributaries come from Bolivia, Ecuador and Venezuela.
• The river flows mainly through Brazil and falls into the Atlantic Ocean.

(c)    Yangtze Kiang (Asia);
    Rise in north-east Tibet; and flows mainly through China, draining into the East China Sea.
(d)    Mississippi-Missouri (North America):

• Mississippi rises in Lake Itasca in Minnesota state of USA; 
• Missouri joins it at Saint Louis; together, they flow into the Gulf of Mexico at New Orleans.

(e)    Mackenzie (North America):
    Rising in Great Slave Lake, it flows through Canada to Mackenzine Bay in the Arctic Ocean.
(f)    Mekong (Asia):

• Rises in Tibet, enters China through which it flows and later forms, for some distance, the borders between Thailand and Laos.
• Falls into the South China Sea.

(g)    Niger (Africa):

• Rising near Sierra Leone, it crosses Niger and flows mainly through Nigeria
• Enters the Atlantic Ocean at the Gulf of Guinea.

(h)    Murray-Darling (Australia):

• Murray rises in the Australian Alps; Darling, its biggest tributary, joins it in the state of New South Wales.
• Both empty into the Indian Ocean at Encounter Bay.

(i)    Volga (Europe):

• Rises in Valdai Plateau north-west of Moscow, Russia
• Enters the Caspian Sea at Astrakhan.

(j)    Danube (Europe):

• Rises near Baden in Germany, flows through Austria, Hungary, Czechoslovakia and Yugoslavia, crosses Romania.
• Enters the Black Sea.

RIVER SYSTEM OF INDIA    

      The Himalayan Rivers:

• The major Himalayan Rivers are the Indus, the Ganga and the Brahmaputra. 
• These rivers are long, and are joined by many large and important tributaries.

(a)    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.
• Several tributaries, the Zaskar, the Nubra, the Shyok and the Hunza, join it in the Kashmir region
• The Indus flows through Baltistan and Gilgit and emerges from the mountains at Attock.
• The Indus plain has a very gentle slope. With a total length of 2900 km, the Indus is one of the longest rivers of the world.
• Main tributaries of Indus are:

(i)    The Jhelum:
    The Jhelum, an important tributary of the Indus, rises from a spring at

    Verinag situated at the foot of the Pir Panjal in the south-eastern part of the valley of Kashmir.
(ii)    The Chenab:

• The Chenab is the largest tributary of the Indus. It is formed by two streams, the Chandra and the Bhaga,
• which join at Tandi near Keylong in Himachal Pradesh. Hence, it is also known as Chandrabhaga.
• The river flows for 1,180 km before entering into Pakistan.

(iv)    The Ravi:
       The Ravi is another important tributary of the Indus. It rises west of the Rohtang pass in

       the Kullu hills of Himachal Pradesh and flows through the Chamba valley of the state.
(v)    The Beas:
        The Beas is another important tributary of the Indus, originating from the Beas Kund near the Rohtang Pass at an elevation of 4,000 m above the mean sea level.
(vi)   The Satluj:
        The Satluj originates in the Rakas Lake near Mansarovar at an altitude of 4,555 mt.in Tibet, where it is known as Langchen Khambab.
(b)   The Ganga system:

• The headwaters of the Ganga, called the ‘Bhagirathi’ is fed by the Gangotri Glacier and joined by
• the Alakhanda at Devprayag in Uttarnchal. At Haridwar the Ganga emerges from the mountains on to the plains.
• The main tributaries from the peninsular uplands are the Chambal, the Betwa and the Son.
• The mainstream, flows southwards into Bangladesh and is joined by the Brahmaputra. Further down stream,
• it is known as the Meghna and finally flows into the Bay of Bengal. The delta formed by these rivers is known as the Sunderban Delta.

(c)    The Brahmaputra System:

• The Brahmaputra rises in Tibet east of Mansarovar Lake. It is slightly longer than the Indus. It flow eastwards parallel to the Himalayas.
• On reaching the Namcha Barwa (7757 m), it takes a ‘U’ turn and enters India in Arunachal Pradesh through a gorge.
• Here, it is called the Dihang and it is joined by the Dibang, the Lohit, the Kenula and many other tributaries to form the Brahmaputra in Assam.

    The Peninsular Rivers:

• The Peninsular drainage system is older than the Himalayan one. 
• Peninsular rivers are characterised by fixed course, absence of meanders, small drainage basin and not-perennial flow of water.
• The main water divide in peninsular India is formed by the Western Ghats.
• Most of the major rivers of the Peninsula flow eastwards and drain into the Bay of Bengal.
• The Narmada and the Tapi which flow through the rift valley are exceptions.

(a)    The Narmada Basin:

• The Narmada originates on the western flank of the Amarkantak plateau at a height of about 1,057 m.
• It falls into the Arabian Sea south of Bharuch. The Sardar Sarovar Project has been constructed on this river.
• The ‘Marble rock’, near Jabalpur where the Narmada flows through a deep gorge, and the ‘Dhuadhar falls’
• where the river plunges over steep rock, are some of the notable ones.
• The Narmada basin covers parts of Madhya Pradesh and Gujarat.

(b)    The Tapi Basin:

• The Tapi originates from Satpura ranges in the Betul district of Madhya Pradesh.
• Nearly 79 percent of its basin lies in Maharashtra, 15 percent in Madhya Pradesh and the remaining 6 percent in Gujarat.
• The Tapi flows in a rift valley parallel to the Narmada but it is much shorter in length.

(c)    The Godavari Basin:

• The Godavari is the largest peninsular river system. It rises from the slopes of the
• Western Ghats in the Nasik district of Maharashtra. Its length is about 1500 km.
• Because of its length and the area it covers, it is also known as the Dakshin Ganga.
• Its basin cover parts of Maharashtra, Madhya Pradesh, Orissa and Andhra Pradesh.
• The Godavari is joined by a number of tributaries such as the Penganga, the Pranhita,
• the Manjra, the Wainganga and the Wardha. It finally drains into the Bay  of Bengal.

(d)    The Mahanadi:

• The Mahanadi rises near Sihawa in Rajpur district of Chhattisgarh and runs through Orissa to discharge its water into the Bay of Bengal.
• Fifty three percent of the drainage basin of this river lies in Madhya Pradesh and Chhattisgarh, while 47 percent lies in Orissa.

(e)    The Krishna:

• The Krishna is the second largest east-flowing peninsular river which rises near Mahabaleshwar in Sahyadri.
• Its total length is 1,401 km.
• The Koyna, the Tungbhadra and the Bhima are its major tributaries.

(f)    The Kaveri:

• The Kaveri rises in Brahmgiri hills (3,341 m) of Kogadu district in Karnataka.
• Its important tributaries are the Kabini, the Bhavani and the Amaravati.
• Though the Indus is a perennial river, much of its water is lost as it flows through the Thar Desert.
• The delta formed by this river is mostly wasteland, since it is usually flooded with brackish water.
• River Brahmaputra has different names in different countries: Tsang-po in Tibet (China); Brahmaputra in India;
• and Jamuna in Bangladesh. During floods, the water of the Brahmaputra looks reddish in colour after mixing
• with the red soils of Assam. This is why the Brahmaputra is also known as the ‘Red River’ of India.
• The Ganga basin forms 25 percent of the total area of India. It is the longest river in the country. 
• Gaumukh (meaning cow’s mouth), an ice cave in the Himalayas, is the source of the Ganga.
• The Yamuna is the most important tributary on the right bank of River Ganga. 
• River Damodar is known as the ‘Sorrow of Bengal’ as it causes widespread destruction of lives, cattle and crops due to frequent flooding. It joins the Ganga from the right.
• The Cauvery is known as the ‘Ganga of the South’. 
• River Sharavati in the state of Karnataka is famous for its Gersoppa (Jog Falls). These falls can be considered -as one of the world’s greatest waterfalls in the rainy season. 
• The Narmada forms the magnificent waterfall (Marble falls of Bheraghat in Madhya Pradesh). The waterfall is 15 m high.
• The Ganga, Brahmaputra, Mahanadi, Godavari, Krishna and Cauvery are the major river systems of India draining into the Bay of Bengal.
• While Godavari is the largest river system in Peninsular India, it is the second largest (next only to the Ganga System) in India as a whole.
• The Cauvery basins is one of the most developed regions of India from the point of view of power and irrigation.