Topic: Drainage System
A river drains the water collected from a specific area,
which is called its ‘catchment area’.
The flow of water through well-defined channels is known as
‘drainage’ and the network of such channels is called a ‘drainage system’. The
drainage pattern of an area is the outcome of the geological time period, nature
and structure of rocks, topography, slope, amount of water flowing and the
periodically of the flow.
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 often referred to as
watersheds. There is however, a slight difference between a river basin and a
watershed. Watersheds are small in area while the basins cover larger areas.
Indian drainage system may be divided on various 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 of Bengal drainage. They
are separated from each other through the Delhi ridge, the Aravalis and the
Sahyadris (water divide is shown by a line in Figure. Nearly 77 per cent of the
drainage area consisting of the Ganga, the Brahmaputra, the Mahanadi, the
Krishna, etc. is oriented towards the Bay of Bengal while 23 per cent 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: (i) 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. (ii) 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.
The Narmada and Tapi are two large rivers which are
exceptions. They along with many small rivers discharge their waters in the
On the basis of the mode of origin, nature and
characteristics, the Indian drainage may also be classified into the Himalayan
drainage and the peninsular drainage. Although it has the problem of including
the Chambal, the Betwa, the Son, etc. which are much older in age and origin
than other rivers that have their origin in the Himalayas, it is the most
accepted basis of classification.
Drainage systems of India
Indian drainage system consists of a large number of small
and big rivers. It is the outcome of the evolutionary process of the three major
physiographic units and the nature and characteristics of precipitation.
Important Drainage Patterns
The drainage pattern resembling the branches of a tree is
known as “dendritic” the examples of which are the rivers of 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 know as ‘centripetal’.
The Himalayan Drainage
The Himalayan drainage system has evolved through a long
geological history. It mainly includes the Ganga, the Indus and the Brahmaputra
rivers basins. Since these are fed both by melting of snow and precipitation,
rivers of this system are perennial. These rivers pass though the giant gorges
carved out by the erosional activity carried on simultaneously with the uplift
of the Himalayas. Besides deep gorges, these rivers also form 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. In the Himalayan reaches, the
course of these rivers is highly tortuous, but over the plains they display a
strong meandering tendency and shift their courses frequently. River Kosi, also
know as the ‘sorrow of Bihar’, has been notorious for frequently changing its
course. The Kosi brngs huge quantity of sediments from its upper reaches and
deposits in the plains. The course gets blocked, and consequently the river
changes its course.
Evolution of the Himalayan Drainage
There are difference of opinion about the evolution of the
Himalayan rivers. However, 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 discharge 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
It is opined that in due course of time Indo-Brahma river was
dismembered into three main drainage systems: (i) the Indus and its five
tributaries in the western part; (ii) the Ganga and its Himalayan tributaries in
the central part: and (iii) the stretch of the Brahmaputra in Assam and its
Himalayan tributaries in the eastern part. The dismemberment was probably due to
the Pleistocene upheaval in the western Himalayan, 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, period, diverted the Ganga and the Brahmaputra systems to flow towards
the Bay of Bengal.
The river systems of the Himalayan Drainage
The Himalayan drainage consists of several river systems but
the following are the major river systems:
The Indus system
It is one of the largest river basins of the world, covering
an area of 11,65,000 sq. km (in India it is 321, 289 sq. km and a total length
of 2,880 km (in India 1,114 km). The Indus also known as the Sindhu, is the
westernmost of the Himalayan rivers in India. It originates from a glacier near
Bokhar Chu (31º 15’ N latitude and 81º40’ 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. After flowing in the northwest direction
between the Ladakh and Zaskar ranges, it passes through Ladakh and Baltistan. It
cuts across the ladakh range, forming a spectacular gorge near Gilgit in Jammu
and Kashmir. It enters into Pakistan near Chillar in the Dardistan region.
The Indus receives a number of Himalayan tributaries such as
the Shyok, the Gilgit, the Zaskar, the Hunza, the Nubra, the Shigar, the Gasting
and the Dras. It finally emerges out of the hills near Attock where it receives
the Kabul river on its right bank. The other important tributaries joining the
right bank of the Indus are the Khurram, the Tochi, the Gomal. The Viboa and the
Sangar. They all originate in the Sulaiman ranges. The river flows southward and
receives Panjnad’ a little above Mithankot. The Panjnad is the name given to the
five rivers of Punjab, namely the Satluj, the Beas, the Ravi, the Chenab and the
Jhelum. It finally discharges into the Arabian Sea, east of Karachi. The Indus
flows in India only through the Leh district in Jammu and Kashmir.
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. 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.
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 Dhaoladhar 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 Rupar. 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.
The Ganga System
The Ganga is the most important river of India both from the
point of view of its basin and cultural significance. It rises in the Gangotri
glacier near Gaumukh (3,900 m) in the Uttarkashi district of Uttaranchal. Here,
it is known as the Bhagirathi. It cuts through the Central and the Lesser
Himalayas in narrow gorges. At Devprayag, the Bhagirathi meets the Alaknanda;
hereafter, it is known as the Ganga. The Alaknanda has its source in the
Satopanth glacier above Bnadrinath. The Alaknanda consists of the Dhaul and the
Vishnu Ganga which meet at Joshimath or Vishnu Prayag. The other tributaries of
Alaknanda such as the Pindar join it at Karna Prayag while Mandakini or Kali
Ganga meets it at Rudra Prayag. 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
river has a length of 2,525 km. It is shared by Uttaranchal (110 km) and Uttar
Pradesh (1,450 km), Bihar (445 km) and West Bengal (520 km). The Ganga basin
covers about 8.6 lakh sq. km area in India alone. The Ganga river system is the
largest in India having a number of perennial and non-perennial rivers
originating in the Himalayas in the north and the Peninsula in the south,
respectively. 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
Banderpunch range (6,316 km). It joins the Ganga at Prayag (Allahabad). It is
joined by the Chambal, the Sind, the Betwa and the Ken on its right bank which
originates from the Peninsular plateau while the Hindan, the Rind, the Sengar,
the Varuna, etc. join it on its left water feeds the western and eastern Yamuna
and the Agra canals for irrigation purposes.
The Chambal rises near Mhow in the Malwa plateau of Madhya
Pradesh northwards through a gorge up wards of Kota in Rajasthan, where the
Gandhisagar dam has been constructed. From Kota, it traverses down to Bundi,
Sawai Madhopur and Dholpur, 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
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, 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
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.
The Brahmaputra System
The Brahmaputra, one of the largest rivers of the world, has
its origin in the Chemayungdung glacier of the Kailash range near the Mansarovar
lake. From here, it traverses eastward longitudinally for a distance of nearly
1,200 km in a dry and flat region of southern 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. It emerges as a turbulent and dynamic river
after carving out a deep gorge in the Central Himalayas near Namcha Barwa (7,755
m). The river emerges from the foothills under the name of Siang or Dihang. It
enters India west of Sadiya town in Arunachal Pradesh. Flowing southwest, it
receives its main left bank tributaries, viz., Dibang or Sikang and Lohit;
thereafter; 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 aree the Burhi Dihing,
Dhansari (South) and Kalang 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. It finally merges with the river
Padma, which falls in the Bay of Bengal. The Brahmaputra is well-known for
floods, channel shifting and bank erosion. This is due to the fact that most of
its tributaries are large, and bring large quantity of sediments owing to heavy
rainfall in its catchment area.
The peninsular drainage system
The peninsular drainage system is older than the Himalayan
one. This is evident from the broad, 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 peninsular 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 characterized by fixed course, absence of
meanders and no perennial flow of water. The Narmada and the Tapi which flow
through the rift valley are, however, exceptions. They meet in Arabian sea.
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) Upheavel 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 southeastern direction gave orientation
to the entire drainage system towards the Bay of Bengal during the same period.
River systems of the peninsular drainage
There are a large number of river systems in the peninsular
drainage. A brief account of the major peninsular river systems is given below:
The Mahanadi rises near Sihawa in Raipur district of Chhattisgarh and runs
through Orissa to discharge its water into the Bay of Bengal. It is 851 km long
and its catchment area spreads over 1.42 lakhs sq. km. Some navigation is
carried on in the lower course of this river. Fifty three per cent of the
drainage basin of this rivers lies in Madhya Pradesh and Chhattisgarh, while 47
per cent lies in Orissa.
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, Orissa and Andhra Pradesh. It is
1,465 km long with a catchment area spreading over 3.13 lakh sq. km 49 per cent
of this, lies in Maharashtra, 20 per cent in Madhya Pradesh and Chhattisgarh,
and the rest in Andhra Pradesh. The Penganga, the Indravati, the Pranhita, and
the Manjra are its principal tributaries. The Godavari is subjected to heavy
floods in its lower reaches to the south of Polavaram, where it forms a
picturesque gorge. It is navigable only in the deltaic stretch. 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. Its total length is 1,401 km.
The Koyna, the Tungbhadra and the Bhima are its major tributaries. Of the total
catchment area of the Krishna, 27 per cent lies in Maharashyra, 44 per cent in
Karnataka and 29 per cent in Andhra Pradesh.
The Kaveri rises in Brahmagiri hills 1,341m of Kogadu
district in Karnataka. Its length is 800 km and it drains an area of 81,155 sq.
km. 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. About 3 per cent of the Kaveri
basin falls in Kerala, 41 per cent in Karnataka and 56 per cent in Tamil Nadu.
Its important tributaries are the Kabini, the Bhavani and the Amravati.
The Narmada originates on the western flank of the Amarkantak
plateau at a height of about 1,057 m. Flowing in a rift valley between the
Satpura in the south and the Vindhyan range in the north. It forms a picturesque
gorge in marble rocks and Dhuandhar waterfall near Jabalpur. After flowing a
distance of about 1,312 km, it meets the Arabian sea south of Bharuch, forming a
broad 27 km long estuary. Its catchment area is about 98,796 sq. km. The Sardar
Sarovar Project has been constructed on this river.
The Tapi is the other important westward flowing river. It
originates from Multai in the Betul district of Madhya Pradesh. It is 724 km
long and drains an area of 65,145 sq. km. Nearly 79 per cent of its basin lies
in Maharashtra, 15 per cent in Madhya Pradesh and the remaining 6 per cent in
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 Kuchchh. The entire river
system is ephemeral.
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