DRAINAGE SYSTEM
The flow of water through well-defined channels is known as drainage and the network of such channels is called a ‘drainage system‘.
(i). Perennial (always with water)
(ii). Ephemeral (water during rainy season, and dry, otherwise)
A river drains the water collected from a specific area, which is called its catchment area‘. An area drained by a river and its tributaries is called a drainage basin. The boundary line separating one drainage basin from the other is known as the watershed.
The catchments of large rivers are called river basins, while those of small rivulets and rills are referred to as watersheds. Watersheds are small in area while the basins cover larger areas.
The drainage pattern resembling the branches of a tree is known as 'dendritic'. The examples of which are the rivers of the northern plain.
When the rivers originate from a hill and flow in all directions, the drainage pattern is known as ‘radial’. The rivers originating from the Amarkantak range present a good example of it.
When the primary tributaries of rivers flow parallel to each other and secondary tributaries join them at right angles, the pattern is known as ‘trellis’.
When the rivers discharge their waters from all directions in a lake or depression, the pattern is known as ‘centripetal’.
On the basis of discharge of water (orientations to the sea), it may be grouped into:
(i). The Arabian Sea drainage.
(ii). The Bay of Bengal drainage.
They are separated from each other through the Delhi ridge, the Aravallis and the Sahyadris.
Nearly 77 percent of the drainage area consisting of the Ganga, the Brahmaputra, the Mahanadi, the Krishna, etc. is oriented towards the Bay of Bengal, while 23 percent comprising the Indus, the Narmada, the Tapi, the Mahi and the Periyar systems discharge their waters in the Arabian Sea.
On the basis of the size of the watershed, the drainage basins of India are grouped into three categories:
Major river basins with more than 20,000 sq. km of catchment area. It includes 14 drainage basins such as the Ganga, the Brahmaputra, the Krishna, the Tapi, the Narmada, the Mahi, the Pennar, the Sabarmati, the Barak, etc.
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.
Minor river basins with catchment areas of less than 2,000 sq. km include a fairly good number of rivers flowing in the area of low rainfall.
Drainage Systems Of India
On the basis of the mode of origin, nature and characteristics, the Indian drainage may also be classified into:
(i). The Himalayan drainage
(ii). The Peninsular drainage.
The Himalayan Drainage
The Himalayan drainage system has evolved through a long geological history. Rivers form giant gorges, V-shaped valleys, rapids and waterfalls in their mountainous course. While entering the plains, they form depositional features like flat valleys, ox-bow lakes, flood plains, braided channels and deltas near the river mouth.
The important rivers are Ganga, the Indus and the Brahmaputra rivers. Since these are fed both by melting of snow and precipitation, rivers of this system are perennial.
River Kosi, also known as the sorrow of Bihar‘, has been notorious for frequently changing its course.
1. Evolution of the Himalayan Drainage
Geologists believe that a mighty river called Shiwalik or Indo-Brahma traversed the entire longitudinal extent of the Himalaya from Assam to Punjab and onwards to Sind, and finally discharged into the Gulf of Sind near lower Punjab during the Miocene period some 5-24 million years ago.
The remarkable continuity of the Shiwalik and its lacustrine origin and alluvial deposits consisting of sands, silt, clay, boulders and conglomerates support this viewpoint. In due course of time Indo-Brahma river was dismembered into three main drainage systems.
(i). The stretch of the Brahmaputra in Assam and its Himalayan tributaries in the eastern part, (ii). The Ganga and its Himalayan tributaries in the central part; and (iii). The Indus and its five tributaries in the western part.
The dismemberment was probably due to the Pleistocene upheaval in the western Himalayas, including the uplift of the Potwar Plateau (Delhi Ridge), which acted as the water divide between the Indus and Ganga drainage systems.
Likewise, the down- thrusting of the Malda gap area between the Rajmahal hills and the Meghalaya plateau during the mid-Pleistocene period diverted the Ganga and the Brahmaputra systems to flow towards the Bay of Bengal.
2. The River System of the Himalayan Drainage
(i). The Indus System
One of the largest river basins of the world. Originates from a glacier near Bokhar Chu (31°15' N latitude and 81°40' E longitude) in the Tibetan region at an altitude of 4,164 m in the Kailash Mountain range. In Tibet, it is known as Singi Khamban; or Lion‘s mouth. Enters into Pakistan near Chillar in the Dardistan region.
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. It flows through Srinagar and the Wular Lake before entering Pakistan through a deep narrow gorge. It joins the Chenab near Jhang in Pakistan.
The Chenab is the largest tributary of the Indus, 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 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. Before entering Pakistan and joining the Chenab near Sarai Sidhu, it drains the area lying between the southeastern part of the Pir Panjal and the Dhauladhar ranges.
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. The river flows through the Kullu valley and forms gorges at Kati and Largi in the Dhauladhar range. It enters the Punjab plains where it meets the Satluj near Harike.
The Satluj originates in the Rakas Lake near Mansarovar at an altitude of 4,555 m in Tibet where it is known as Langchen Khambab. It flows almost parallel to the Indus for about 400 km before entering India, and comes out of a gorge at Ropar. It passes through the Shipki La on the Himalayan ranges and enters the Punjab plains. It is an antecedent river. It is a very important tributary as it feeds the canal system of the Bhakra Nangal project
(ii). The Ganga System
Rises in the Gangotri glacier near Gaumukh (3,900 m) in the Uttar kashi district of Uttarakhand. Here, it is known as the Bhagirathi. At Devprayag, the Bhagirathi meets the Alaknanda; here after, it is known as the Ganga. The Alaknanda has its source in the Satopanth glacier above Badrinath.
The Ganga enters the plains at Haridwar. From here, it flows first to the south, then to the south-east and east before splitting into two distributaries, namely the Bhagirathi and the Hugli.
The Son is its major right bank tributary. The important left bank tributaries are the Ramganga, the Gomati, the Ghaghara, the Gandak, the Kosi and the Mahananda. The river finally discharges itself into the Bay of Bengal near the Sagar Island.
The Yamuna , the western most and the longest tributary of the Ganga, has its source in the Yamunotri glacier on the western slopes of Bandarpunch range (6,316 km). It joins the Ganga at Prayag (Allahabad).
The Chambal rises near Mhow in the Malwa plateau of Madhya Pradesh and flows northwards through a gorge upwards of Kota in Rajasthan, where the Gandhisagar dam has been constructed, and finally joins the Yamuna. The Chambal is famous for its badland topography called the Chambal ravines.
The Gandak comprises two streams, namely Kaligandak and Trishulganga. It rises in the Nepal Himalayas between the Dhaulagiri and Mount Everest and drains the central part of Nepal. It enters the Ganga plain in Champaran district of Bihar and joins the Ganga at Sonpur near Patna.
The Ghaghara originates in the glaciers of Mapchachungo. After collecting the waters of its tributaries – Tila, Seti and Beri, it comes out of the mountain, cutting a deep gorge at Shishapani. The river Sarda (Kali or Kali Ganga) joins it in the plain before it finally meets the Ganga at Chhapra.
The Kosi is an antecedent river with its source to the north of Mount Everest in Tibet, where its main stream Arun rises. After crossing the Central Himalayas in Nepal, it is joined by the Son Kosi from the West and the Tamur Kosi from the east. It forms Sapt Kosi after uniting with the river Arun.
The Ramganga is comparatively a small river rising in the Garhwal hills near Gairsain. It changes its course to the southwest direction after crossing the Shiwalik and enters into the plains of Uttar Pradesh near Najibabad. Finally, it joins the Ganga near Kannauj.
The Damodar occupies the eastern margins of the Chotanagpur Plateau where it flows through a rift valley and finally joins the Hugli. The Barakar is its main tributary. Once known as the ‘sorrow of Bengal’, the Damodar has been now tamed by the Damodar Valley corporation, a multipurpose project.
The Sarda or Saryu river rises in the Milan glacier in the Nepal Himalayas where it is known as the Goriganga. Along the Indo-Nepal border, it is called Kali or Chauk, where it joins the Ghaghara.
The Mahananda is another important tributary of the Ganga rising in the Darjeeling hills. It joins the Ganga as its last left bank tributary in West Bengal.
The Son is a large south bank tributary of the Ganga, originating in the Amarkantak plateau. After forming a series of waterfalls at the edge of the plateau, it reaches Arrah, west of Patna, to join the Ganga.
(iii). The Brahmaputra Systems
Origin in the Chemayungdung glacier of the Kailash range near the Mansarovar lake. Tibet, where it is known as the Tsangpo, which means the purifier.‘ The Rango Tsangpo is the major right bank tributary of this river in Tibet. Enters India west of Sadiya town in Arunachal Pradesh. Flowing southwest, it receives its main left bank tributaries, viz., Dibang or Sikang and Lohit; there after, it is known as the Brahmaputra. The Brahmaputra receives numerous tributaries in its 750 km long journey through the Assam valley.
Its major left bank tributaries are the Burhi Dihing and Dhansari (South) whereas the important right bank tributaries are the Subansiri, Kameng, Manas and Sankosh. The Subansiri which has its origin in Tibet, is an antecedent river.
The Brahmaputra enters into Bangladesh near Dhubri and flows southward. In Bangladesh, the Tista joins it on its right bank from where the river is known as the Yamuna, and finally merges with the river Padma, which falls in the Bay of Bengal.
The Peninsular Drainage System
The Peninsular drainage system is older than the Himalayas. The largely-graded shallow valleys, and the maturity of the rivers.
The Western Ghats running close to the western coast act as the water divide between the major Peninsular Rivers, discharging their water in the Bay of Bengal and as small rivulets joining the Arabian Sea.
Most of the major Peninsular rivers except Narmada and Tapi flow from west to east.
The Chambal, the Sind, the Betwa, the Ken, the Son, originating in the northern part of the Peninsula belong to the Ganga river system. The other major river systems of the Peninsular drainage are – the Mahanadi, the Godavari, the Krishna and the Kaveri.
Peninsular rivers are characterised by fixed course, absence of meanders and non- perennial flow of water. The Narmada and the Tapi which flow through the rift valley.
The Evolution of Peninsular Drainage System
Three major geological events in the distant past have shaped the present drainage systems of Peninsular India:
(i). Subsidence of the western flank of the Peninsula leading to its submergence below the sea during the early tertiary period. Generally, it has disturbed the symmetrical plan of the river on either side of the original watershed.
(ii). Upheaval of the Himalayas when the northern flank of the Peninsular block was subjected to subsidence and the consequent trough faulting. The Narmada and The Tapi flow in trough faults and fill the original cracks with their detritus materials. Hence, there is a lack of alluvial and deltaic deposits in these rivers.
(iii). Slight tilting of the Peninsular block from northwest to the south-eastern direction gave orientation to the entire drainage system towards the Bay of Bengal during the same period.
River Systems of the Peninsular Drainage
The Mahanadi rises near Sihawa in Raipur district of Chhattisgarh and runs through Odisha to discharge its water into the Bay of Bengal. Some navigation is carried on in the lower course of this river. Fifty three percent of the drainage basin of this river lies in Madhya Pradesh and Chhattisgarh, while 47 percent lies in Odisha.
The Godavari is the largest peninsular river system. It is also called the Dakshin Ganga. It rises in the Nasik district of Maharashtra and discharges its water into the Bay of Bengal. Its tributaries run through the states of Maharashtra, Madhya Pradesh, Chhattisgarh, Odisha and AndhraPradesh. Tributaries- Penganga, the Indravati, the Pranhita, and the Manjra. The river after Rajamundri splits into several branches forming a large delta.
The Krishna is the second largest east- flowing Peninsular river which rises near Mahabaleshwar in Sahyadri. The Koyna, the Tungabhadra and the Bhima- major tributaries. Of the total catchment area of the Krishna, 27 percent lies in Maharashtra, 44 percent in Karnataka and 29 percent in Andhra Pradesh.
The Kaveri rises in Brahmagiri hills of Kogadu district in Karnataka. Since the upper catchment area receives rainfall during the southwest monsoon season (summer) and the lower part during the northeast monsoon season (winter), the river carries water throughout the year with comparatively less fluctuation than the other Peninsular Rivers. Kaveri basin- Kerala, Karnataka and Tamil Nadu. Tributaries- Kabini, the Bhavani and Amravati.
The Narmada originates on the western flank of the Amarkantak plateau. Flowing in a ri valley between the Satpura in the south and the Vindhyan range, Dhuandhar waterfall nearJabalpur. It meets the Arabian sea south of Branch forming estuary. The Sardar Sarovar Project has been constructed.
The Tapi is the other important westward flowing river. It originates from Multai in the Betul district of Madhya Pradesh. Its basin lies in Maharashtra, Madhya Pradesh and Gujarat.
The Luni is the largest river system of Rajasthan, west of Aravali. It originates near Pushkar in two branches, i.e. the Saraswati and the Sabarmati, which join with each other at Govindgarh. From here, the river comes out of Aravali and is known as Luni. It flows towards the west till Telwara and then takes a southwest direction to join the Rann of Kuch. The entire river system is ephemeral.
Smaller Rivers Flowing Towards the West
- Shetruniji - rises near Dalkahwa in Amreli district.
- Bhadra - Anjali village in Rajkot district.
- Dhadhar - Ghantar village in Panchmahal district.
- Vaitarna - Trimbak hills in Nasik district at an elevation of 670 m.
- Kalinadi - rises from Belgaum district and falls in the Karwar Bay.
- Bedti river - lies in Hubli Dharwar.
- Sharavati - originates in Shimoga district of Karnataka.
- Mandovi & juari – Goa.
- Bharathapuzha or Ponnani – longest in Kerala, rises near Anamalai.
- Periyar – 2nd largest in Kerala.
- Pamba – Kerala – falls in Vembanad lake.
- Small rivers flowing towards the east : Rivers draining towards east - Subarnarekha, the Baitarni, the Brahmani, the Vamsadhara, thePenner, the Palar and the Vaigai.
Comparison between the himalayan and the peninsular rivers are.
Aspects
- Place of origin
- Nature of flow
- Type of drainage
- Nature of river
- Catchment Area
- Age of the river
Himalayan River
- Himalayan mountain covered with glaciers.
- Perennial; receive water from glacier and rainfall.
- Antecedent and consequent leading to dendritic pattern in plains.
- Long course, flowing through the rugged mountains experiencing headward erosion and river capturing; In plains meandering and shiing of course.
- Very large basins.
- Young and youthful, active and deepening in the valleys.
Peninsular River
- Peninsular plateau and central highland
- Seasonal; dependent on monsoon rainfall
- Superimposed, rejuvenated resulting in trellis, radial and rectangular patterns
- Smaller, fixed course with well-adjusted valleys
- Relatively smaller basin
- Old rivers with graded profile, and have almost reached their base levels
River Regimes
The pattern of flow of water in a river channel over a year is known as its regime. The north Indian rivers originating from the Himalayas are perennial as they are fed by glaciers through snow melt and also receive rainfall water during the rainy season. The discharge is the volume of water flowing in a river measured over time.
The Ganga maintains a sizeable flow in the early part of summer due to snow melt before the monsoon rains begin.
The mean maximum discharge of the Ganga at Farakka is about 55,000 cusecs. while the mean minimum is only 1,300 cusecs. It is measured either in cusecs (cubic feet per second) or cumecs (cubic metres per second).
The flow increases considerably during monsoon rains. Thus, the regime of the rivers of South is controlled by rainfall which also varies from one part of the Peninsular plateau to the other.
There are striking differences in the river regimes in the eastern and the western parts of the Ganga Basin.
Extent of Usability of River Water
1. River Water can be used in the following way:
- Construction of dams
- Construction of canals parallel to the river
- Li irrigation
- Interlinking of rivers
- Construction of check dams
2. Problems Of River Water Usability:
- No availability in sufficient quantity
- Uneven seasonal flow of water
- River water disputes between states
- River water pollution
- Load of silt in the river water
- Shrinking of channels due to the extension of settlements towards the thalweg.
Pollution of Rivers : Most of the cremation grounds are on the banks of rivers and the dead bodies are sometimes thrown in the rivers. On the occasion of some festivals, the flowers and statues are immersed in the rivers. Large scale bathing and washing of clothes also pollute river waters.
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