• flow of water through well-defined channels is called drainage and network of such channels is known as a drainage system.
• drainage pattern of an area is outcome of geological period, nature & structure of rocks, topography, slope, amount of water flowing, and periodicity of flow.
• A river drains water collected from a specific area, which is known as its catchment area.
• An area drained by a river and its tributaries is known as a drainage basin.
• boundary line separating one drainage basin from other is called watershed.
• catchments of large rivers are known as river basins while those of small rivulets and rills are often referred to as watersheds.
• On basis of size of watershed, drainage basins of India are grouped into three categoriesMajor river basin with, Medium river basin, and Minor river basin.
• On basis of mode of origin, nature, & characteristics, Indian drainage may be classified into Himalayan drainage and Peninsular drainage.
Drainage System of India
• Indian drainage system consists of a large number of small and large rivers.
• Himalayan Drainage system mainly includes Ganga, Indus, & Brahmaputra river basin. Since these are fed both by melting of snow and precipitation, rivers of this system are perennial. These rivers pass through giant gorges carved out by erosional activity carried on simultaneously with uplift of Himalayas.
• Besides deep gorges, Himalayan rivers form V-shaped valleys, rapids, & waterfalls in their mountainous course.
• While entering plains, they form depositional features like flat valleys, ox-bow lakes, flood plains, braided channels, and deltas near river mouth.
• In Himalayan reaches, course of these rivers is highly tortuous, but over plains, they display a strong meandering tendency and shift their courses frequently.
Evolution of Himalayan Drainage
• There are differences of opinion about evolution of Himalayan rivers.
• Geologists think that a large river called Shiwalik or Indo-Brahma flowed from Assam to Punjab to Sind and then into Gulf of Sind near lower Punjab during Miocene period, about 5 million to 24 million years ago. This point of view is supported by fact that Shiwalik has stayed same for a long time, that it started as a lake, and that it has alluvial deposits of sand, silt, clay, boulders, and conglomerates. People think that Indo-Brahma river eventually split into three main drainage systems:
(1) Indus and its five tributaries in western part;
(2) Ganga and its Himalayan tributaries in central part; and
(3) stretch of Brahmaputra in Assam and its Himalayan tributaries in eastern part.
River Systems of Himalayan Drainage
• Himalayan drainage consists of following river system.
• This is one of largest river basins of world called Sindhu, it is westernmost of Himalayan rivers in India.
• river Indus originates from a glacier near Bokhar Chu in Tibetan region in Kailash Mountain Range In Tibet, it is called Singi Khamban, or Lion’s mouth.
• river cuts across Ladakh and Zaskar range, forming a spectacular gorge near Gilgit in Jammu and Kashmir and enters Pakistan near Chilas in Dardistan region.
• Indus receives many Himalayan tributaries such as Shyok, Gilgit, Zaskar, Hunza, Nubra, Shigar, Gasting & Dras.
• river Indus finally discharges into Arabian Sea, east of Karachi. Indus flows in India only through Jammu and Kashmir.
• Jhelum, an important tributary of Indus, rises from a spring at Verinag situated at foot of Pir Panjal in south-eastern part of valley of Kashmir.
• Chenab is largest tributary of Indus. This is formed by two streams, Chandra & Bhaga, which join at Tandi near Keylong in Himachal Pradesh.
• Ravi is another important tributary of Indus. It rises west of Rohtang pass in Kullu hills of Himachal Pradesh and flows through Chamba valley of state.
• Beas is another important tributary of Indus, originating from Beas Kund near Rohtang Pass.
• Satluj originates in Raksas tal near Mansarovar at an altitude of 4,555 m in Tibet where it is called Langchen Khambab.
• Brahmaputra, one of largest rivers in world, has its origin in Chemayungdung glacier of Kailash range near Mansarovar lake.
• Rango Tsangpo is major right-bank tributary of this river in Tibet.
• Brahmaputra receives numerous tributaries in its 750 km long journey through Assam valley. Its major left bank tributaries are Burhi Dihing and Dhansari [South] whereas important right bank tributaries are Subansiri, Kameng, Manas, & Sankosh.
• Subansiri which has its origin in Tibet is an antecedent river.
• Brahmaputra enters Bangladesh near Dhubri and flows southward.
• In Bangladesh, Tista joins it on its right bank from where river is called Jamuna. It finally merges with river Padma, which falls in Bay of Bengal.
• river Ganga rises in Gangotri glacier near Gaumukh [3,900 m] in Uttarkashi district of Uttarakhand and here it is called Bhagirathi.
• At Devprayag, Bhagirathi meets Alaknanda; hereafter, it is called Ganga.
• Alaknanda has its source in Satopanth glacier above Badrinath. Alaknanda consists of Dhauli and Vishnu Ganga which meet at Joshimath or Vishnu Prayag.
• Ganga enters plains at Haridwar. From here, it flows first to south, then to south-east and east before splitting into two distributaries, namely Bhagirathi and Padma.
• Ganga river system is largest in India and India has many perennial and non-perennial rivers originating in Himalayas in north and Peninsula in south, respectively.
• Son is its major right-bank tributary.
• important left bank tributaries are Ramganga, Gomati, Ghaghara, Gandak, Kosi & Mahananda.
• river finally discharges itself into Bay of Bengal near Sagar Island.
• Yamuna, westernmost and longest tributary of Ganga, has its source in Yamunotri glacier on western slopes of Banderpunch range and joins Ganga at Prayag [Prayagraj].
• Chambal rises near Mhow in Malwa plateau of Madhya Pradesh and flows northwards through a gorge upwards of Kota in Rajasthan, where Gandhisagar dam has been constructed.
• Gandak comprises two streams, namely Kaligandak and Trishulganga. It rises in Nepal Himalayas between Dhaulagiri and Mount Everest and drains central part of Nepal.
• river Gandak enters Ganga plain in Champaran district of Bihar and joins Ganga at Sonpur near Patna.
• Ghaghara originates in glaciers of Mapchachungo. After collecting waters of its tributaries – Tila, Seti & Beri, it comes out of mountain, cutting a deep gorge at Shishapani.
• river Sarda [Kali or Kali Ganga] joins Ghaghara in plain before it finally meets Ganga at Chhapra.
• Kosi is an antecedent river with its source to north of Mount Everest in Tibet, where its mainstream Arun rises.
• Ramganga is comparatively a small river rising in Garhwal hills near Gairsain.
• Damodar, once called Sorrow of Bengal occupies eastern margins of Chotanagpur Plateau where it flows through a rift valley and finally joins Hugli river.
• Sarda or Saryu river rises in Milam glacier in Nepal Himalayas where it is called Goriganga. Along Indo-Nepal border, it is known as Kali or Chauk, where it joins Ghaghara.
• Mahananda is another important tributary of Ganga rising in Darjeeling hills. It joins Ganga as its last left bank tributary in West Bengal.
Peninsular Drainage System
• Peninsular drainage system is older than Himalayan one.
• Most of major Peninsular rivers except Narmada and Tapi flow from west to east.
• Chambal, Sind, Betwa, Ken, & Son, originating in northern part of Peninsula belong to Ganga river system.
• other major river systems of Peninsular drainage are – Mahanadi Godavari, Krishna, & Kaveri.
• Peninsular rivers are characterized by fixed course, absence of meanders, and non-perennial flow of water.
• Narmada and Tapi which flow through rift valley are, however, exceptions.
evolution of Peninsular Drainage System
• Three major geological events in distant past have shaped present drainage systems of Peninsular India.
(1) Subsidence of western flank of Peninsula leading to its submergence below sea during early tertiary period.
(2) Upheaval of Himalayas when northern flank of Peninsular block was subjected to subsidence and consequent trough faulting.
(3) Slight tilting of Peninsular block from northwest to southeastern direction gave orientation to entire drainage system towards Bay of Bengal during same period.
River Systems of Peninsular Drainage
• There are a large number of river systems in Peninsular drainage.
• Mahanadi rises near Sihawa in Raipur district of Chhattisgarh and runs through Odisha to discharge its water into Bay of Bengal.
• Godavari is largest Peninsular river system. This is known as Dakshin Ganga. It rises in Nasik district of Maharashtra and discharges its water into Bay of Bengal.
• Penganga, Indravati, Pranhita, & Manjra are principal tributaries of Godavari.
• Krishna is second-largest east-flowing Peninsular river which rises near Mahabaleshwar in Sahyadri.
• Kabini, Bhavani & Amravati are important tributaries of Krishna.
• Narmada originates on western flank of Amarkantak plateau at a height of about 1, 057 m.
• Flowing in a rift valley between Satpura in south and Vindhyan range in north, Narmada forms a picturesque gorge in marble rocks and Dhuandhar waterfall near Jabalpur.
• Tapi is other important westward flowing river. It originates from Multai in Betul district of Madhya Pradesh.
• Luni is largest river system of Rajasthan, west of Aravali. It originates near Pushkar in two branches, i.e. Saraswati and Sabarmati, which join with each other at Govindgarh.
Smaller Rivers Flowing Towards West and East
• rivers flowing toward Arabian sea have short courses.
• Shetruniji is one such river that rises near Dalkahwa in Amreli district.
• Bhadra originates near Aniali village in Rajkot district.
• Dhadhar rises near Ghantar village in Panchmahal district.
• Sabarmati and Mahi are two famous rivers of Gujarat.
• Vaitarna rises from Trimbak hills in Nasik district at an elevation of 670 m.
• Kalindi rises from Belgaum district and falls in Karwar Bay.
• source of Bedti river lies in Hubli Dharwar and traverses a course of 161 km.
• Sharavati is another important river in Karnataka flowing towards west. River originates in Shimoga district of Karnataka and drains a catchment area of 2, 209 sq. km.
• Goa has two important rivers -Mandovi and other is Juari.
• longest river of Kerala, Bharathapuzha rises near Annamalai hills. This is called Ponnani.
• Periyar is second largest river in Kerala.
• There are a large number of rivers flowing towards east along with their tributaries.
• Subarnrekha, Baitarni, Brahmani, Vamsadhara, Penner, Palar, & Vaigai are important east-flowing rivers.
• quantity of water flowing in a river channel is not same throughout year and it varies from season to season.
• pattern of flow of water in a river channel over a year is called its regime.
• north Indian rivers originating from Himalayas are perennial as they are fed by glaciers through snowmelt and receive rainfall water during rainy season.
• rivers of South India do not originate from glaciers and their flow pattern witnesses fluctuations.
Extent of Usability of River Water
• rivers of India carry huge volumes of water per year but it is unevenly distributed both in time and space.
• There are perennial rivers carrying water throughout year while non-perennial rivers have very little water during dry season.
• During rainy season, much of water is wasted in floods and flows down to sea.
• Similarly, when there is a flood in one part of country, other area suffers from drought.
• Pollution of rivers is another concern.