NCERT Book Class 9 Social Science (Geography) Chapter 3 Drainage

DRAINAGE
3
T
he term drainage describes the river DRAINAGE SYSTEMS IN INDIA
system of an area. Look at the physical
The drainage systems of India are mainly
map. You will notice that small streams
controlled by the broad relief features of the
flowing from different directions come together
subcontinent. Accordingly, the Indian rivers
to form the main river, which ultimately drains
are divided into two major groups:
into a large water body such as a lake or a sea
• the Himalayan rivers; and
or an ocean. The area drained by a single river
• the Peninsular rivers.
system is called a drainage basin. A closer
Apart from originating from the two major
observation on a map will indicate that any
physiographic regions of India, the Himalayan
elevated area, such as a mountain or an upland,
and the Peninsular rivers are different from
separates two drainage basins. Such an upland
each other in many ways. Most of the
is known as a water divide (Figure 3.1).
Himalayan rivers are perennial. It means
that they have water throughout the year.
am
m
BB These rivers receive water from rain as well
treea
Sr
S
as from melted snow from the lofty
ammA W
at
treea mountains. The two major Himalayan rivers,
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S er
Di
vi
de
the Indus and the Brahmaputra originate
from the north of the mountain ranges. They
have cut through the mountains making
gorges. The Himalayan rivers have long
courses from their source to the sea.

Figure 3.1 : Water Divide

The world’s largest drainage
basin is of the Amazon river

• Which river has the largest basin in India?
Figure 3.2 : A Gorge