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CHAPTERDRAINAGE SYSTEMYou have observed water flowing throughthe rivers, nalas and even channelsduring rainy season which drain theexcess water. Had these channels not beenthere, large-scale flooding would haveoccurred. Wherever channels are ill-defined orchoked, flooding is a common phenomenon.2006) in this class . Can you, then, explain thereason for water flowing from one direction tothe other? Why do the rivers originating from theHimalayas in the northern India and the WesternGhat in the southern India flow towards the eastand discharge their waters in the Bay of Bengal?The flow of water through well-definedchannels is known as ‘drainage’ and thenetwork of such channels is called a‘drainage system’. The drainage patternof an area is the outcome of the geologicaltime period, nature and structure ofrocks, topography, slope, amount ofwater flowing and the periodicity ofthe flow.Do you have a river near your village or city?Have you ever been there for boating or bathing?Is it perennial (always with water) or ephemeral(water during rainy season, and dry, otherwise)?Do you know that rivers flow in the samedirection? You have studied about slopes in theother two textbooks of geography (NCERT,Figure 3.1 : A River in the Mountainous RegionA river drains the water collected from aspecific area, which is called its ‘catchment area’.An area drained by a river and its tributariesis called a drainage basin. The boundary lineImportant Drainage Patterns(i) The drainage pattern resembling the branches of a tree is known as “dendritic” the examplesof which are the rivers of northern plain.(ii) When the rivers originate from a hill and flow in all directions, the drainage pattern is knownas ‘radial’. The rivers originating from the Amarkantak range present a good example of it.(iii) When the primary tributaries of rivers flow parallel to each other and secondary tributariesjoin them at right angles, the pattern is known as ‘trellis’.(iv) When the rivers discharge their waters from all directions in a lake or depression, thepattern is know as ‘centripetal’.Find out some of the patterns in the topo sheet given in Chapter 5 of Practical Work inGeography– Part I (NCERT, 2006).2020-21
INDIA : PHYSICAL ENVIRONMENT22Figure 3.2 : Major Rivers of India2020-21
DRAINAGE SYSTEM23separating one drainage basin from the otheris known as the watershed. The catchments oflarge rivers are called river basins while thoseof small rivulets and rills are often referred toas watersheds. There is, however, a slightdifference between a river basin and awatershed. Watersheds are small in area whilethe basins cover larger areas.River basins and watersheds are markedby unity. What happens in one part of thebasin or watershed directly affects the otherparts and the unit as a whole. That is why, theyare accepted as the most appropriate micro,meso or macro planning regions.Indian drainage system may be divided onvarious bases. On the basis of discharge of water(orientations to the sea), it may be grouped into:(i) the Arabian Sea drainage; and (ii) the Bay ofBengal drainage. They are separated from eachother through the Delhi ridge, the Aravalis andthe Sahyadris (water divide is shown by a linein Figure 3.1). Nearly 77 per cent of the drainagearea consisting of the Ganga, the Brahmaputra,the Mahanadi, the Krishna, etc. is orientedtowards the Bay of Bengal while 23 per centcomprising the Indus, the Narmada, the Tapi,the Mahi and the Periyar systems dischargetheir waters in the Arabian Sea.On the basis of the size of the watershed,the drainage basins of India are grouped intothree categories: (i) Major river basins withmore than 20,000 sq. km of catchment area.It includes 14 drainage basins such as theGanga, the Brahmaputra, the Krishna, theTapi, the Narmada, the Mahi, the Pennar, theSabarmati, the Barak, etc. (Appendix III). (ii)Medium river basins with catchment areabetween 2,000-20,000 sq. km incorporating44 river basins such as the Kalindi, the Periyar,the Meghna, etc. (iii) Minor river basins withcatchment area of less than 2,000 sq. kminclude fairly good number of rivers flowing inthe area of low rainfall.If you look at the Figure 3.1 you can seethat many rivers have their sources in theHimalayas and discharge their waters either inthe Bay of Bengal or in the Arabian Sea. Identifythese rivers of North India. Large rivers flowingon the Peninsular plateau have their origin inthe Western Ghats and discharge their watersin the Bay of Bengal. Identify these rivers of theSouth India.The Narmada and Tapi are two large riverswhich are exceptions. They along with manysmall rivers discharge their waters in theArabian Sea.Name these rivers of the western coastalregion from the Konkan to the Malabar coast.On the basis of the mode of origin, natureand characteristics, the Indian drainage mayalso be classified into the Himalayan drainageand the Peninsular drainage. Although it hasthe problem of including the Chambal, theBetwa, the Son, etc. which are much older inage and origin than other rivers that have theirorigin in the Himalayas, it is the most acceptedbasis of classification. Hence, this scheme hasbeen followed in this book.DRAINAGE SYSTEMSOFINDIAIndian drainage system consists of a largenumber of small and big rivers. It is the outcomeof the evolutionary process of the three majorphysiographic units and the nature andcharacteristics of precipitation.THE HIMALAYAN DRAINAGEThe Himalayan drainage system has evolvedthrough a long geological history. It mainlyincludes the Ganga, the Indus and theBrahmaputra river basins. Since these are fedboth by melting of snow and precipitation,rivers of this system are perennial. These riverspass through the giant gorges carved out bythe erosional activity carried on simultaneouslywith the uplift of the Himalayas. Besides deepgorges, these rivers also form V-shaped valleys,rapids and waterfalls in their mountainous2020-21Figure 3.3 : Rapids
INDIA : PHYSICAL ENVIRONMENT24course. While entering the plains, they formdepositional features like flat valleys, ox-bowlakes, flood plains, braided channels, anddeltas near the river mouth. In the Himalayanreaches, the course of these rivers is highlytortous, but over the plains they display astrong meandering tendency and shift theircourses frequently. River Kosi, also know asthe ‘sorrow of Bihar’, has been notorious forfrequently changing its course. The Kosi bringshuge quantity of sediments from its upperreaches and deposits it in the plains. Thecourse gets blocked, and consequently, theriver changes its course. Why does the Kosiriver bring such huge quantity of sedimentsfrom the upper reaches? Do you think thatthe discharge of the water in the rivers ingeneral and the Kosi in particular, remains thesame, or does it fluctuate? When does the rivercourse receive the maximum quantity of water?What are the positive and negative effects offlooding?EVOLUTIONOF THEHIMALAYAN DRAINAGEThere are difference of opinion about theevolution of the Himalayan rivers. However,geologists believe that a mighty river calledShiwalik or Indo-Brahma traversed the entirelongitudinal extent of the Himalaya from Assamto Punjab and onwards to Sind, and finallydischarged into the Gulf of Sind near lowerPunjab during the Miocene period some 5-24million years ago (See the table of geologicaltimes scale in Chapter 2 of Fundamentals ofPhysical Geography, NCER T, 2006). Theremarkable continuity of the Shiwalik and itslacustrine origin and alluvial depositsconsisting of sands, silt, clay, boulders andconglomerates support this viewpoint.It is opined that in due course of time Indo–Brahma river was dismembered into three maindrainage systems: (i) the Indus and its fivetributaries in the western part; (ii) the Gangaand its Himalayan tributaries in the centralpart; and (iii) the stretch of the Brahmaputrain Assam and its Himalayan tributaries in theeastern part. The dismemberment wasprobably due to the Pleistocene upheaval inthe western Himalayas, including the uplift ofthe Potwar Plateau (Delhi Ridge), which actedas the water divide between the Indus andGanga drainage systems. Likewise, the downthrusting of the Malda gap area between theRajmahal hills and the Meghalaya plateauduring the mid-pleistocene period, diverted theGanga and the Brahmaputra systems to flowtowards the Bay of Bengal.THE RIVER SYSTEMS OFHIMALAYAN DRAINAGETHEThe Himalayan drainage consists of severalriver systems but the following are the majorriver systems:The Indus SystemIt is one of the largest river basins of the world,covering an area of 11,65,000 sq. km (in Indiait is 321, 289 sq. km and a total length of 2,880km (in India 1,114 km). The Indus alsoknown as the Sindhu, is the westernmost ofthe Himalayan rivers in India. It originatesfrom a glacier near Bokhar Chu (31 15' Nlatitude and 81 40' E longitude) in theTibetan region at an altitude of 4,164 m inthe Kailash Mountain range. In Tibet, it isknown as ‘Singi Khamban; or Lion’s mouth.After flowing in the northwest directionbetween the Ladakh and Zaskar ranges, itpasses through Ladakh and Baltistan. It cutsacross the Ladakh range, forming aspectacular gorge near Gilgit in Jammu andKashmir. It enters into Pakistan near Chilasin the Dardistan region. Find out the areaknown as Dardistan.The Indus receives a number of Himalayantributaries such as the Shyok, the Gilgit, theZaskar, the Hunza, the Nubra, the Shigar, theGasting and the Dras. It finally emerges out ofthe hills near Attock where it receives the Kabulriver on its right bank. The other importanttributaries joining the right bank of the Indusare the Khurram, the Tochi, the Gomal, theViboa and the Sangar. They all originate in theSulaiman ranges. The river flows southwardand receives ‘Panjnad’ a little above Mithankot.The Panjnad is the name given to the five riversof Punjab, namely the Satluj, the Beas, the Ravi,the Chenab and the Jhelum. It finally discharges2020-21
DRAINAGE SYSTEM25into the Arabian Sea, east of Karachi. TheIndus flows in India only through Jammu andKashmir.The Jhelum, an important tributary of theIndus, rises from a spring at Verinag situatedat the foot of the Pir Panjal in the south-easternpart of the valley of Kashmir. It flows throughSrinagar and the Wular lake before enteringPakistan through a deep narrow gorge. It joinsthe Chenab near Jhang in Pakistan.The Chenab is the largest tributary of theIndus. It is formed by two streams, theChandra and the Bhaga, which join atTandi near Keylong in Himachal Pradesh.Hence, it is also known as Chandrabhaga.The river flows for 1,180 km before enteringinto Pakistan.The Ravi is another important tributary ofthe Indus. It rises west of the Rohtang pass inthe Kullu hills of Himachal Pradesh and flowsthrough the Chamba valley of the state. Beforeentering Pakistan and joining the Chenab nearSarai Sidhu, it drains the area lying betweenthe southeastern part of the Pir Panjal and theDhauladhar ranges.The Beas is another important tributary ofthe Indus, originating from the Beas Kund nearthe Rohtang Pass at an elevation of 4,000 mabove the mean sea level. The river flowsthrough the Kullu valley and forms gorges atKati and Largi in the Dhaoladhar range. Itenters the Punjab plains where it meets theSatluj near Harike.The Satluj originates in the ‘Raksas tal’ nearMansarovar at an altitude of 4,555 m in Tibetwhere it is known as Langchen Khambab. Itflows almost parallel to the Indus for about 400km before entering India, and comes out of agorge at Rupar. It passes through the ShipkiLa on the Himalayan ranges and enters thePunjab plains. It is an antecedent river. It is avery important tributary as it feeds the canalsystem of the Bhakra Nangal project.The Ganga SystemThe Ganga is the most important river ofIndia both from the point of view of its basinand cultural significance. It rises in theGangotri glacier near Gaumukh (3,900 m)in the Uttarkashi district of Uttarakhand.Here, it is known as the Bhagirathi. It cutsthrough the Central and the LesserHimalayas in narrow gorges. At Devprayag,the Bhagirathi meets the Alaknanda;hereafter, it is known as the Ganga. TheAlaknanda has its source in the Satopanthglacier above Badrinath. The Alaknandaconsists of the Dhauli and the Vishnu Gangawhich meet at Joshimath or Vishnu Prayag.The other tributaries of Alaknanda such asthe Pindar joins it at Karna Prayagwhile Mandakini or Kali Ganga meets it atRudra Prayag. The Ganga enters the plainsat Haridwar. From here, it flows first tothe south, then to the south-east and east2020-21Do you Know?‘Namami Gange Programme’, is anIntegrated Conservation Mission, approvedas “Flagship Programme” by the UnionGovernment in June 2014 with the twinobjectives of effective abatement of pollution,conservation and rejuvenation of theNational River Ganga.Main pillars of the Namami GangeProgramme are: Sewerage Treatment Infrastructure River-Front Development River -Surface Cleaning Bio-Diversity Afforestation Public Awareness Industrial Effluent Monitoring Ganga GramYou may explore about this project athttp://nmcg.nic.in/NamamiGanga.aspx#
INDIA : PHYSICAL ENVIRONMENT26before splitting into two distributaries, namelythe Bhagirathi and the Padma. The river hasa length of 2,525 km. It is shared byUttarakhand (110 km) and Uttar Pradesh(1,450 km), Bihar (445 km) and West Bengal(520 km). The Ganga basin covers about 8.6lakh sq. km area in India alone. The Gangariver system is the largest in India having anumber of perennial and non-perennial riversoriginating in the Himalayas in the north andthe Peninsula in the south, respectively. TheSon is its major right bank tributary. Theimportant left bank tributaries are theRamganga, the Gomati, the Ghaghara, theGandak, the Kosi and the Mahananda. Theriver finally discharges itself into the Bay ofBengal near the Sagar Island.The Yamuna, the western most and thelongest tributary of the Ganga, has its sourcein the Yamunotri glacier on the western slopesof Banderpunch range (6,316 km). It joins theGanga at Prayag (Allahabad). It is joined bythe Chambal, the Sind, the Betwa and the Kenon its right bank which originates from thePeninsular plateau while the Hindan, the Rind,the Sengar, the Varuna, etc. join it on its leftbank. Much of its water feeds the western andeastern Yamuna and the Agra canals forirrigation purposes.Name the states which are drained bythe river Yamuna.The Chambal rises near Mhow in theMalwa plateau of Madhya Pradesh and flowsnorthwards through a gorge up wards of Kotain Rajasthan, where the Gandhisagar dam hasbeen constructed. From Kota, it traverses downto Bundi, Sawai Madhopur and Dholpur, andfinally joins the Yamuna. The Chambal isfamous for its badland topography called theChambal ravines.The Gandak comprises two streams,namely Kaligandak and Trishulganga. It risesin the Nepal Himalayas between the Dhaulagiriand Mount Everest and drains the central partof Nepal. It enters the Ganga plain inChamparan district of Bihar and joins theGanga at Sonpur near Patna.The Ghaghara originates in the glaciers ofMapchachungo. After collecting the waters ofits tributaries – Tila, Seti and Beri, it comesout of the mountain, cutting a deep gorge atShishapani. The river Sarda (Kali or KaliGanga) joins it in the plain before it finally meetsthe Ganga at Chhapra.The Kosi is an antecedent river with itssource to the north of Mount Everest in Tibet,where its main stream Arun rises. Aftercrossing the Central Himalayas in Nepal, it isjoined by the Son Kosi from the West and theTamur Kosi from the east. It forms Sapt Kosiafter uniting with the river Arun.The Ramganga is comparatively a smallriver rising in the Garhwal hills near Gairsain.It changes its course to the southwest directionafter crossing the Shiwalik and enters into theplains of Uttar Pradesh near Najibabad. Finally,it joins the Ganga near Kannauj.The Damodar occupies the eastern marginsof the Chotanagpur Plateau where it flowsthrough a rift valley and finally joins the Hugli.The Barakar is its main tributary. Once knownas the ‘sorrow of Bengal’, the Damodar hasbeen now tamed by the Damodar Valleycorporation, a multipurpose project.The Sarda or Saryu river rises in the Milamglacier in the Nepal Himalayas where it isknown as the Goriganga. Along the Indo-Nepalborder, it is called Kali or Chauk, where it joinsthe Ghaghara.The Mahananda is another importanttributary of the Ganga rising in the Darjilinghills. It joins the Ganga as its last left banktributary in West Bengal.The Son is a large south bank tributary ofthe Ganga, originating in the Amarkantakplateau. After forming a series of waterfalls atthe edge of the plateau, it reaches Arrah, westof Patna, to join the Ganga.The Brahmaputra SystemThe Brahmaputra, one of the largest riversof the world, has its origin in theChemayungdung glacier of the Kailash rangenear the Mansarovar lake. From here, ittraverses eastward longitudinally for adistance of nearly 1,200 km in a dry andflat region of southern Tibet, where it isknown as the Tsangpo, which means ‘the2020-21
DRAINAGE SYSTEM27purifier.’ The Rango Tsangpo is the majorright bank tributary of this river in Tibet. Itemerges as a turbulent and dynamic riverafter carving out a deep gorge in the CentralHimalayas near Namcha Barwa (7,755 m).The river emerges from the foothills underthe name of Siang or Dihang. It enters Indiawest of Sadiya town in Arunachal Pradesh.Flowing southwest, it receives its main leftbank tributaries, viz., Dibang or Sikang andLohit; ther eafter, it is known as theBrahmaputra.The Brahmaputra receives numeroustributaries in its 750 km long journey throughthe Assam valley. Its major left banktributaries are the Burhi Dihing and Dhansari(South) whereas the important right banktributaries are the Subansiri, Kameng, Manasand Sankosh. The Subansiri which has itsorigin in Tibet, is an antecedent river. TheBrahmaputra enters into Bangladesh nearDhubri and flows southward. In Bangladesh,the Tista joins it on its right bank from wherethe river is known as the Jamuna. It finallymerges with the river Padma, which falls in theBay of Bengal. The Brahmaputra is well-knownfor floods, channel shifting and bank erosion.This is due to the fact that most of its tributariesare large, and bring large quantity of sedimentsowing to heavy rainfall in its catchment area.THE PENINSULAR DRAINAGE SYSTEMThe Peninsular drainage system is older thanthe Himalayan one. This is evident from thebroad, largely-graded shallow valleys, and thematurity of the rivers. The Western Ghatsrunning close to the western coast act as thewater divide between the major Peninsularrivers, discharging their water in the Bay ofBengal and as small rivulets joining theArabian Sea. Most of the major Peninsularrivers except Narmada and Tapi flow from westto east. The Chambal, the Sind, the Betwa, theKen, the Son, originating in the northern partof the Peninsula belong to the Ganga riversystem. The other major river systems of thePeninsular drainage are – the Mahanadi theGodavari, the Krishna and the Kaveri.Peninsular rivers are characterised by fixedcourse, absence of meanders and nonperennial flow of water. The Narmada and theTapi which flow through the rift valley are,however, exceptions.The Evolution of Peninsular DrainageSystemThree major geological events in the distantpast have shaped the present drainagesystems of Peninsular India: (i) Subsidenceof the western flank of the Peninsula leadingto its submergence below the sea during theearly tertiary period. Generally, it hasdisturbed the symmetrical plan of the riveron either side of the original watershed.(ii) Upheaval of the Himalayas when thenorthern flank of the Peninsular block wassubjected to subsidence and the consequenttrough faulting. The Narmada and The Tapiflow in trough faults and fill the originalcracks with their detritus materials. Hence,there is a lack of alluvial and deltaic depositsin these rivers. (iii) Slight tilting of thePeninsular block from northwest to thesoutheastern direction gave orientation to theentire drainage system towards the Bay ofBengal during the same period.River Systems of the Peninsular DrainageThere are a large number of river systems inthe Peninsular drainage. A brief account of themajor Peninsular river systems is given below:The Mahanadi rises near Sihawa in Raipurdistrict of Chhattisgarh and runs throughOdisha to discharge its water into the Bay ofBengal. It is 851 km long and its catchment areaspreads over 1.42 lakh sq. km. Somenavigation is carried on in the lower course ofthis river. Fifty three per cent of the drainagebasin of this river lies in Madhya Pradesh andChhattisgarh, while 47 per cent lies in Odisha.The Godavari is the largest Peninsular riversystem. It is also called the Dakshin Ganga. Itrises in the Nasik district of Maharashtra anddischarges its water into the Bay of Bengal. Itstributaries run through the states ofMaharashtra, Madhya Pradesh, Chhattisgarh,Odisha and Andhra Pradesh. It is 1,465 kmlong with a catchment area spreading over 3.132020-21
INDIA : PHYSICAL ENVIRONMENT28lakh sq. km 49 per cent of this, lies inMaharashtra, 20 per cent in Madhya Pradeshand Chhattisgarh, and the rest in AndhraPradesh. The Penganga, the Indravati, thePranhita, and the Manjra are its principaltributaries. The Godavari is subjected to heavyfloods in its lower reaches to the south ofPolavaram, where it forms a picturesque gorge.It is navigable only in the deltaic stretch. Theriver after Rajamundri splits into severalbranches forming a large delta.The Krishna is the second largest eastflowing Peninsular river which rises nearMahabaleshwar in Sahyadri. Its total length is1,401 km. The Koyna, the Tungbhadra andthe Bhima are its major tributaries. Of the totalcatchment area of the Krishna, 27 per cent liesin Maharashtra, 44 per cent in Karnataka and29 per cent in Andhra Pradesh and Telangana.The Kaveri rises in Brahmagiri hills(1,341m) of Kogadu district in Karnataka. Itslength is 800 km and it drains an area of81,155 sq. km. Since the upper catchmentarea receives rainfall during the southwestmonsoon season (summer) and the lower partduring the northeast monsoon season (winter),the river carries water throughout the year withcomparatively less fluctuation than the otherPeninsular rivers. About 3 per cent of the Kaveribasin falls in Kerala, 41 per cent in Karnatakaand 56 per cent in Tamil Nadu. Its importanttributaries are the Kabini, the Bhavani and theAmravati.The Narmada originates on the western flankof the Amarkantak plateau at a height of about1,057 m. Flowing in a rift valley between theSatpura in the south and the Vindhyan rangein the north, it forms a picturesque gorge inmarble rocks and Dhuandhar waterfall nearJabalpur. After flowing a distance of about1,312 km, it meets the Arabian sea south ofBharuch, forming a broad 27 km long estuary.Its catchment area is about 98,796 sq. km. TheSardar Sarovar Project has been constructedon this river.Collect information about Narmadariver conservation mission named“Namami Devi Narmade” and discusswith your peers.The Tapi is the other important westwardflowing river. It originates from Multai in the Betuldistrict of Madhya Pradesh. It is 724 km longand drains an area of 65,145 sq. km. Nearly 79per cent of its basin lies in Maharashtra, 15 percent in Madhya Pradesh and the remaining6 per cent in Gujarat.Luni is the largest river system ofRajasthan, west of Aravali. It originates nearPushkar in two branches, i.e. the Saraswatiand the Sabarmati, which join with each otherat Govindgarh. From here, the river comes outof Aravali and is known as Luni. It flowstowards the west till Telwara and then takes asouthwest direction to join the Rann ofKuchchh. The entire river system is ephemeral.Smaller Rivers Flowing Towards the WestThe rivers flowing towards the Arabian seahave short courses. Why do they have shortcourses? Find out the smaller rivers ofGujarat. The Shetruniji is one such riverwhich rises near Dalkahwa in Amreli district.The Bhadra originates near Aniali village inRajkot district. The Dhadhar rises nearGhantar village in Panchmahal district.Sabarmati and Mahi are the two famous riversof Gujarat.Find out the places of confluence of theserivers. Find out some important westflowing rivers of Maharashtra.The Vaitarna rises from the Trimbak hillsin Nasik district at an elevation of 670 m. TheKalinadi rises from Belgaum district and fallsin the Karwar Bay. The source of Bedti riverlies in Hubli Dharwar and traverses a courseof 161 km. The Sharavati is another importantriver in Karnataka flowing towards the west.The Sharavati originates in Shimoga districtof Karnataka and drains a catchment area of2,209 sq. km.Find out the name of the river on whichthe Gersoppa (Jog) fall is found.Goa has two important rivers which can bementioned here. One is Mandovi and the otheris Juari. You can locate them on the map.2020-21
DRAINAGE SYSTEM29Kerala has a narrow coastline. The longestriver of Kerala, Bharathapuzha rises nearAnnamalai hills. It is also known as Ponnani.It drains an area of 5,397 sq. km. Compare itscatchment area with that of the Sharavati riverof Karnataka.The Periyar is the second largest river ofKerala. Its catchment area is 5,243 sq. km.You can see that there is a marginal differencein the catchment area of the Bhartapuzha andthe Periyar rivers.Another river of Kerala worth mentioning isthe Pamba river which falls in the Vemobanadlake after traversing a course of 177 km.Catchment areasq. zhaPeriyarTeachers may explain the comparativeimportance of east flowing small riversRiverCatchment areasq. 78939,03355,21317,870RIVER REGIMESTeachers may explain the comparativeimportance of west flowing small riversRiverright. The Subarnrekha, the Baitarni, theBrahmani, the Vamsadhara, the Penner, thePalar and the Vaigai are important rivers. Findout these rivers from the atlas.21,67434,8422,7705,1792,0295,3975,243Small Rivers Flowing towards the EastThere are a large number of rivers flowingtowards the east along with their tributaries.Can you name some of these rivers? There aresmall rivers which join the Bay of Bengal,though small, these are important in their ownDo you know that the quantity of waterflowing in a river channel is not the samethroughout the year? It varies from seasonto season. In which season do you expect themaximum flow in Ganga and Kaveri? Thepattern of flow of water in a river channel overa year is known as its regime. The north Indianrivers originating from the Himalayas areperennial as they are fed by glaciers throughsnow melt and also receive rainfall water duringrainy season. The rivers of South India do notoriginate from glaciers and their flow patternwitnesses fluctuations. The flow increasesconsiderably during monsoon rains. Thus, theregime of the rivers of South India is controlledby rainfall which also varies from one part ofTable 3.1 : Comparison between the Himalayan and the Peninsular RiverSl. No.AspectsHimalayan RiverPeninsular River1.Place of originHimalayan mountain covered withglaciersPeninsular plateau and central highland2.Nature of flowPerennial; receive water from glacierand rainfallSeasonal; dependent on monsoonrainfall3.Type of drainageAntecedent and consequent leading todendritic pattern in plainsSuper imposed, rejuvenated resultingin trellis, radial and rectangularpatterns4.Nature of riverLong course, flowing through therugged mountains experiencingheadward erosion and river capturing;In plains meandering and shifting ofcourseSmaller, fixed course with well-adjustedvalleys5.Catchment areaVery large basinsRelatively smaller basin6.Age of the riverYoung and youthful, active anddeepening in the valleysOld rivers with graded profile, and havealmost reached their base levels2020-21
INDIA : PHYSICAL ENVIRONMENT30the Peninsular plateau to the other.The discharge is the volume of water flowingin a river measured over time. It is measuredeither in cusecs (cubic feet per second) orcumecs (cubic metres per second).The Ganga has its minimum flow duringthe January-June period. The maximum flowis attained either in August or in September.After September, there is a steady fall in theflow. The river, thus, has a monsoon regimeduring the rainy season.There are striking differences in the riverregimes in the eastern and the western partsof the Ganga Basin. The Ganga maintains asizeable flow in the early part of summer dueto snow melt before the monsoon rains begin.The mean maximum discharge of the Gangaat Farakka is about 55,000 cusecs while themean minimum is only 1,300 cusecs. Whatfactors are responsible for such a largedifference?The two Peninsular rivers displayinteresting differences in their regimescompared to the Himalayan rivers. TheNarmada has a very low volume of dischargefrom January to July but it suddenly rises inAugust when the maximum flow is attained.The fall in October is as spectacular as the risein August. The flow of water in the Narmada,as recorded at Garudeshwar, shows that themaximum flow is of the order of 2,300 cusecs,while the minimum flow is only 15 cusecs. TheGodavari has the minimum discharge in May,and the maximum in July-August. AfterAugust, there is a sharp fall in water flowalthough the volume of flow in October andNovember is higher than that in any of themonths from January to May. The meanmaximum discharge of the Godavari atPolavaram is 3,200 cusecs while the meanminimum flow is only 50 cusecs. These figuresgive an idea of the regime of the river.EXTENTOFUSABILITYOFRIVER WATERThe rivers of India carry huge volumes of waterper year but it is unevenly distributed both intime and space. There are perennial riverscarrying water throughout the year while thenon-perennial rivers have very little water duringthe dry season. During the rainy season, muchof the water is wasted in floods and flows downto the sea. Similarly, when there is a flood in on
Medium river basins with catchment area between 2,000-20,000 sq. km incorporating 44 river basins such as the Kalindi, the Periyar , the Meghna, etc. (iii) Minor river basins with catchment area of less than 2,000 sq. km include fairly good number of rivers flowing in the area of low rainfall. If you look at the Figure 3.1 you can see
