NCERT Textbook - Drainage System | Geography (Prelims) by Valor Academy - UPSC PDF Download

 Page 1


Y
ou have observed water flowing through
the rivers, nalas and even channels
during rainy season which drain the
excess water. Had these channels not been
there, large-scale flooding would have
occurred. Wherever channels are ill-defined or
choked, flooding is a common phenomenon.
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 periodicity of
the 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 same
direction? You have studied about slopes in the
other two textbooks of geography (NCERT,
2006) in this class . Can you, then, explain the
reason for water flowing from one direction to
the other? Why do the rivers originating from the
Himalayas in the northern India and the W estern
Ghat in the southern India flow towards the east
and discharge their waters in the Bay of Bengal?
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
DRAINAGE SYSTEM
CHAPTER
Figure 3.1 : A River in the Mountainous Region
Important Drainage Patterns
(i) The drainage pattern resembling the branches of a tree is known as “dendritic” the examples
of which are the rivers of northern plain.
(ii) 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.
(iii) 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’.
(iv) When the rivers discharge their waters from all directions in a lake or depression, the
pattern is know as ‘centripetal’.
Find out some of the patterns in the topo sheet given in Chapter 5 of Practical Work in
Geography– Part I (NCERT, 2006).
2024-25
Page 2


Y
ou have observed water flowing through
the rivers, nalas and even channels
during rainy season which drain the
excess water. Had these channels not been
there, large-scale flooding would have
occurred. Wherever channels are ill-defined or
choked, flooding is a common phenomenon.
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 periodicity of
the 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 same
direction? You have studied about slopes in the
other two textbooks of geography (NCERT,
2006) in this class . Can you, then, explain the
reason for water flowing from one direction to
the other? Why do the rivers originating from the
Himalayas in the northern India and the W estern
Ghat in the southern India flow towards the east
and discharge their waters in the Bay of Bengal?
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
DRAINAGE SYSTEM
CHAPTER
Figure 3.1 : A River in the Mountainous Region
Important Drainage Patterns
(i) The drainage pattern resembling the branches of a tree is known as “dendritic” the examples
of which are the rivers of northern plain.
(ii) 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.
(iii) 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’.
(iv) When the rivers discharge their waters from all directions in a lake or depression, the
pattern is know as ‘centripetal’.
Find out some of the patterns in the topo sheet given in Chapter 5 of Practical Work in
Geography– Part I (NCERT, 2006).
2024-25
18 INDIA : PHYSICAL ENVIRONMENT
Figure 3.2 : Major Rivers of India
AFGHANISTAN
2024-25
Page 3


Y
ou have observed water flowing through
the rivers, nalas and even channels
during rainy season which drain the
excess water. Had these channels not been
there, large-scale flooding would have
occurred. Wherever channels are ill-defined or
choked, flooding is a common phenomenon.
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 periodicity of
the 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 same
direction? You have studied about slopes in the
other two textbooks of geography (NCERT,
2006) in this class . Can you, then, explain the
reason for water flowing from one direction to
the other? Why do the rivers originating from the
Himalayas in the northern India and the W estern
Ghat in the southern India flow towards the east
and discharge their waters in the Bay of Bengal?
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
DRAINAGE SYSTEM
CHAPTER
Figure 3.1 : A River in the Mountainous Region
Important Drainage Patterns
(i) The drainage pattern resembling the branches of a tree is known as “dendritic” the examples
of which are the rivers of northern plain.
(ii) 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.
(iii) 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’.
(iv) When the rivers discharge their waters from all directions in a lake or depression, the
pattern is know as ‘centripetal’.
Find out some of the patterns in the topo sheet given in Chapter 5 of Practical Work in
Geography– Part I (NCERT, 2006).
2024-25
18 INDIA : PHYSICAL ENVIRONMENT
Figure 3.2 : Major Rivers of India
AFGHANISTAN
2024-25
19 DRAINAGE SYSTEM
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.
River basins and watersheds are marked
by unity. What happens in one part of the
basin or watershed directly affects the other
parts and the unit as a whole. That is why, they
are accepted as the most appropriate micro,
meso or macro planning regions.
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 3.1). 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. (Appendix III). (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.
If you look at the Figure 3.1 you can see
that many rivers have their sources in the
Himalayas and discharge their waters either in
the Bay of Bengal or  in the Arabian Sea. Identify
these rivers of North India. Large rivers flowing
on the Peninsular plateau have their origin in
the Western Ghats and discharge their waters
in the Bay of Bengal. Identify these rivers of the
South India.
The Narmada and Tapi are two large rivers
which are exceptions. They along with many
small rivers discharge their waters in the
Arabian Sea.
Name these rivers of the western coastal
region from the Konkan to the Malabar coast.
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. Hence, this scheme has
been followed in this book.
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.
THE HIMALAYAN DRAINAGE
The Himalayan drainage system has evolved
through a long geological history. It mainly
includes the Ganga, the Indus and the
Brahmaputra river basins. Since these are fed
both by melting of snow and precipitation,
rivers of this system are perennial. These rivers
pass through 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
Figure 3.3 : Rapids
2024-25
Page 4


Y
ou have observed water flowing through
the rivers, nalas and even channels
during rainy season which drain the
excess water. Had these channels not been
there, large-scale flooding would have
occurred. Wherever channels are ill-defined or
choked, flooding is a common phenomenon.
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 periodicity of
the 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 same
direction? You have studied about slopes in the
other two textbooks of geography (NCERT,
2006) in this class . Can you, then, explain the
reason for water flowing from one direction to
the other? Why do the rivers originating from the
Himalayas in the northern India and the W estern
Ghat in the southern India flow towards the east
and discharge their waters in the Bay of Bengal?
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
DRAINAGE SYSTEM
CHAPTER
Figure 3.1 : A River in the Mountainous Region
Important Drainage Patterns
(i) The drainage pattern resembling the branches of a tree is known as “dendritic” the examples
of which are the rivers of northern plain.
(ii) 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.
(iii) 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’.
(iv) When the rivers discharge their waters from all directions in a lake or depression, the
pattern is know as ‘centripetal’.
Find out some of the patterns in the topo sheet given in Chapter 5 of Practical Work in
Geography– Part I (NCERT, 2006).
2024-25
18 INDIA : PHYSICAL ENVIRONMENT
Figure 3.2 : Major Rivers of India
AFGHANISTAN
2024-25
19 DRAINAGE SYSTEM
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.
River basins and watersheds are marked
by unity. What happens in one part of the
basin or watershed directly affects the other
parts and the unit as a whole. That is why, they
are accepted as the most appropriate micro,
meso or macro planning regions.
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 3.1). 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. (Appendix III). (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.
If you look at the Figure 3.1 you can see
that many rivers have their sources in the
Himalayas and discharge their waters either in
the Bay of Bengal or  in the Arabian Sea. Identify
these rivers of North India. Large rivers flowing
on the Peninsular plateau have their origin in
the Western Ghats and discharge their waters
in the Bay of Bengal. Identify these rivers of the
South India.
The Narmada and Tapi are two large rivers
which are exceptions. They along with many
small rivers discharge their waters in the
Arabian Sea.
Name these rivers of the western coastal
region from the Konkan to the Malabar coast.
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. Hence, this scheme has
been followed in this book.
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.
THE HIMALAYAN DRAINAGE
The Himalayan drainage system has evolved
through a long geological history. It mainly
includes the Ganga, the Indus and the
Brahmaputra river basins. Since these are fed
both by melting of snow and precipitation,
rivers of this system are perennial. These rivers
pass through 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
Figure 3.3 : Rapids
2024-25
20 INDIA : PHYSICAL ENVIRONMENT
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
tortous, 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 brings
huge quantity of sediments from its upper
reaches and deposits it in the plains. The
course gets blocked, and consequently, the
river changes its course. Why does the Kosi
river bring such huge quantity of sediments
from the upper reaches? Do you think that
the discharge of the water in the rivers in
general and the Kosi in particular, remains the
same, or does it fluctuate? When does the river
course receive the maximum quantity of water?
What are the positive and negative effects of
flooding?
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
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.
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 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.
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 (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.
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 Chilas
in the Dardistan region. Find out the area
known as Dardistan.
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
2024-25
Page 5


Y
ou have observed water flowing through
the rivers, nalas and even channels
during rainy season which drain the
excess water. Had these channels not been
there, large-scale flooding would have
occurred. Wherever channels are ill-defined or
choked, flooding is a common phenomenon.
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 periodicity of
the 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 same
direction? You have studied about slopes in the
other two textbooks of geography (NCERT,
2006) in this class . Can you, then, explain the
reason for water flowing from one direction to
the other? Why do the rivers originating from the
Himalayas in the northern India and the W estern
Ghat in the southern India flow towards the east
and discharge their waters in the Bay of Bengal?
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
DRAINAGE SYSTEM
CHAPTER
Figure 3.1 : A River in the Mountainous Region
Important Drainage Patterns
(i) The drainage pattern resembling the branches of a tree is known as “dendritic” the examples
of which are the rivers of northern plain.
(ii) 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.
(iii) 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’.
(iv) When the rivers discharge their waters from all directions in a lake or depression, the
pattern is know as ‘centripetal’.
Find out some of the patterns in the topo sheet given in Chapter 5 of Practical Work in
Geography– Part I (NCERT, 2006).
2024-25
18 INDIA : PHYSICAL ENVIRONMENT
Figure 3.2 : Major Rivers of India
AFGHANISTAN
2024-25
19 DRAINAGE SYSTEM
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.
River basins and watersheds are marked
by unity. What happens in one part of the
basin or watershed directly affects the other
parts and the unit as a whole. That is why, they
are accepted as the most appropriate micro,
meso or macro planning regions.
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 3.1). 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. (Appendix III). (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.
If you look at the Figure 3.1 you can see
that many rivers have their sources in the
Himalayas and discharge their waters either in
the Bay of Bengal or  in the Arabian Sea. Identify
these rivers of North India. Large rivers flowing
on the Peninsular plateau have their origin in
the Western Ghats and discharge their waters
in the Bay of Bengal. Identify these rivers of the
South India.
The Narmada and Tapi are two large rivers
which are exceptions. They along with many
small rivers discharge their waters in the
Arabian Sea.
Name these rivers of the western coastal
region from the Konkan to the Malabar coast.
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. Hence, this scheme has
been followed in this book.
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.
THE HIMALAYAN DRAINAGE
The Himalayan drainage system has evolved
through a long geological history. It mainly
includes the Ganga, the Indus and the
Brahmaputra river basins. Since these are fed
both by melting of snow and precipitation,
rivers of this system are perennial. These rivers
pass through 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
Figure 3.3 : Rapids
2024-25
20 INDIA : PHYSICAL ENVIRONMENT
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
tortous, 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 brings
huge quantity of sediments from its upper
reaches and deposits it in the plains. The
course gets blocked, and consequently, the
river changes its course. Why does the Kosi
river bring such huge quantity of sediments
from the upper reaches? Do you think that
the discharge of the water in the rivers in
general and the Kosi in particular, remains the
same, or does it fluctuate? When does the river
course receive the maximum quantity of water?
What are the positive and negative effects of
flooding?
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
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.
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 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.
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 (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.
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 Chilas
in the Dardistan region. Find out the area
known as Dardistan.
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
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21 DRAINAGE SYSTEM
discharges into the Arabian Sea, east of
Karachi. The Indus flows in India only through
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 ‘Raksas tal’ 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 Uttarakhand.
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 Badrinath. The Alaknanda
consists of the Dhauli and the Vishnu Ganga
which meet at Joshimath or Vishnu Prayag.
The other tributaries of Alaknanda such as
the Pindar joins 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 Padma. The
river has a length of 2,525 km. It is shared by
Uttarakhand (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
Do you Know?
‘Namami Gange Programme’, is an
Integrated Conservation Mission, approved
as “Flagship Programme” by the Union
Government in June 2014 with the twin
objectives of effective abatement of pollution,
conservation and rejuvenation of the
National River Ganga.
Main pillars of the Namami Gange
Programme are:
• Sewerage Treatment Infrastructure
• River-Front Development
• River-Surface Cleaning
• Bio-Diversity
• Afforestation
• Public Awareness
• Industrial Effluent Monitoring
• Ganga Gram
You may explore about this project at
http://nmcg.nic.in/NamamiGanga.aspx#
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