DRAINAGE T D S I - NCERT

1 DRAINAGEThe term DRAINAGE describes the riversystem of an area. Look at the physicalmap. You will notice that small streamsflowing from different directions come togetherto form the main river, which ultimately drainsinto a large water body such as a lake or a seaor an ocean. The area drained by a single riversystem is called a DRAINAGE basin. A closerobservation on a map will indicate that anyelevated area, such as a mountain or an upland,separates two DRAINAGE basins. Such an uplandis known as a water divide (Figure ).Figure : A GorgeDRAINAGE SYSTEMS IN INDIAThe DRAINAGE systems of India are mainlycontrolled by the broad relief features of thesubcontinent. Accordingly, the Indian riversare divided into two major groups: the Himalayan rivers; and the Peninsular from originating from the two majorphysiographic regions of India, the Himalayanand the Peninsular rivers are different fromeach other in many ways.

2 Most of theHimalayan rivers are perennial. It meansthat they have water throughout the rivers receive water from rain as wellas from melted snow from the loftymountains. The two major Himalayan rivers,the Indus and the Brahmaputra originatefrom the north of the mountain ranges. Theyhave cut through the mountains makinggorges. The Himalayan rivers have longcourses from their source to the DivideSream ASream BFigure : Water DivideThe world s largest drainagebasin is of the Amazon river Which river has the largest basin in India?Stream AStream B2021 2218 CONTEMPORARY INDIA-IThey perform intensive erosional activity intheir upper courses and carry huge loads ofsilt and sand. In the middle and the lowercourses, these rivers form meanders, oxbowlakes, and many other depositional featuresin their floodplains.

3 They also have well-developed deltas (Figure ).A large number of the Peninsular rivers areseasonal, as their flow is dependent on the dry season, even the large rivershave reduced flow of water in their Peninsular rivers have shorter andshallower courses as compared to theirHimalayan counterparts. However, some ofthem originate in the central highlands and flowtowards the west. Can you identify two suchlarge rivers? Most of the rivers of peninsularIndia originate in the Western Ghats and flowtowards the Bay of of RiverUpper CourseMiddle CourseOx-Bow LakeLowerCourseMeanderDeltaFigure : Some Features Made by RiversThe Himalayan RiversThe major Himalayan rivers are the Indus, theGanga and the Brahmaputra. These rivers arelong, and are joined by many large andimportant tributaries.

4 A river alongwith itstributaries may be called a river Indus River SystemThe river Indus rises in Tibet, near LakeMansarowar. Flowing west, it enters India in theLadakh. It forms a picturesque gorge in thispart. Several tributaries, the Zaskar, the Nubra,the Shyok and the Hunza, join it in the Kashmirregion. The Indus flows through Baltistan andGilgit and emerges from the mountains at Satluj, the Beas, the Ravi, the Chenab andthe Jhelum join together to enter the Indus nearMithankot in Pakistan. Beyond this, the Indusflows southwards eventually reaching theArabian Sea, east of Karachi. The Indus plainhas a very gentle slope. With a total length of2900 km, the Indus is one of the longest riversof the world. A little over a third of the Indusbasin is located in India Ladakh, Jammu andKashmir, Himachal Pradesh and Punjab and therest is in Pakistan.

5 According to the regulationsof the Indus Water Treaty (1960), India canuse only 20 per cent of the total water carried bythe Indus river system. This water is used forirrigation in Punjab, Haryana and the southernand the western parts of Ganga River SystemThe headwaters of the Ganga, called the Bhagirathi is fed by the Gangotri Glacier andjoined by the Alaknanda at Devaprayag inUttarakhand. At Haridwar, the Ganga emergesfrom the mountains on to the 22 DRAINAGE19 Figure : Major Rivers and Lakes2021 2220 CONTEMPORARY INDIA-IThe Ganga is joined by many tributariesfrom the Himalayas, a few of them being majorrivers, such as the Yamuna, the Ghaghara, theGandak and the Kosi. The river Yamuna risesfrom the Yamunotri Glacier in the flows parallel to the Ganga and as a rightbank tributary meets the Ganga at Ghaghara, the Gandak and the Kosi risein the Nepal Himalaya.

6 They are the rivers,which flood parts of the northern plains everyyear, causing widespread damage to life andproperty, whereas, they enrich the soil foragricultural main tributaries, which come from thepeninsular uplands, are the Chambal, theBetwa and the Son. These rise from semi-aridareas, have shorter courses and do not carrymuch water in them. Find out where and howthey ultimately join the : Confluence of Bhagirathi and Alaknanda atDevaprayag The Namami Gange Programmeis an Integrated Conservation Mission approved asa flagship programme by the Union Governmentin June 2014 to accomplish the twin objectives ofeffective abatement of pollution, conservation andrejuvenation of the national river, Ganga.

7 You mayexplore about this project at #Enlarged with the waters from its right andleft bank tributaries, the Ganga flowseastwards till Farakka in West Bengal. This isthe northernmost point of the Ganga delta. Theriver bifurcates here; the Bhagirathi-Hooghly(a distributary) flows southwards through thedeltaic plains to the Bay of Bengal. Themainstream, flows southwards intoBangladesh and is joined by the downstream, it is known as theMeghna. This mighty river, with waters fromthe Ganga and the Brahmaputra, flows intothe Bay of Bengal. The delta formed by theserivers is known as the Sundarban Delta. The Sundarban Delta derivedits name from the Sundari tree, which grows wellin marshland. It is the world s largest and fastest growing is also the home of Royal Bengal length of the Ganga is over 2500 at Figure ; can you identify the type ofdrainage pattern formed by the Ganga riversystem?

8 Ambala is located on the water dividebetween the Indus and the Ganga river plains from Ambala to the Sunderbanstretch over nearly 1800 km, but the fall in itsslope is hardly 300 metres. In other words, thereis a fall of just one metre for every 6 , the river develops large Brahmaputra River SystemThe Brahmaputra rises in Tibet east ofMansarowar lake very close to the sources ofthe Indus and the Satluj. It is slightly longerthan the Indus, and most of its course liesoutside India. It flows eastwards parallel tothe Himalayas. On reaching the NamchaBarwa (7757 m), it takes a U turn and entersIndia in Arunachal Pradesh through a , it is called the Dihang and it is joined bythe Dibang, the Lohit, and many othertributaries to form the Brahmaputra in Assam.

9 Brahmaputra is known asthe Tsang Po in Tibet and Jamuna in 22 DRAINAGE21In Tibet, the river carries a smaller volume ofwater and less silt as it is a cold and a dry India, it passes through a region of highrainfall. Here the river carries a large volume ofwater and considerable amount of silt. TheBrahmaputra has a braided channel in its entirelength in Assam and forms many riverine you remember the name of the world s largestriverine island formed by the Brahmaputra?Every year during the rainy season, theriver overflows its banks, causing widespreaddevastation due to floods in Assam andBangladesh. Unlike other north Indian rivers,the Brahmaputra is marked by huge depositsof silt on its bed causing the riverbed to river also shifts its channel Peninsular RiversThe main water divide in Peninsular India isformed by the Western Ghats, which runs fromnorth to south close to the western coast.

10 Mostof the major rivers of the Peninsula, such asthe Mahanadi, the Godavari, the Krishna andthe Kaveri flow eastwards and drain into theBay of Bengal. These rivers make deltas attheir mouths. There are numerous smallstreams flowing west of the Western Narmada and the Tapi are the only longrivers, which flow west and make esturies. Thedrainage basins of the peninsular rivers arecomparatively smaller in Narmada BasinThe Narmada rises in the Amarkantak hillsin Madhya Pradesh. It flows towards the westin a rift valley formed due to faulting. On itsway to the sea, the Narmada creates manypicturesque locations. The Marble rocks ,near Jabalpur, where the Narmada flowsthrough a deep gorge, and the Dhuadharfalls, where the river plunges over steep rocks,are some of the notable ones.