Page 1 - LN- Sub Topic-5

SAI International School
Grade-IX Sub: Geography

Ch 3- Drainage
Sub Topic5- Lakes, Map Work
Sub-topics Lesson Notes

Lakes- page
no- 22 Lakes
• Lakes are large bodies of water surrounded by land almost on all sides.

• They differ from each other in size and other characteristics.
• Most lakes are permanent or perennial while other contains water only during the
rainy season and are seasonal.

• The lakes in the semi arid region of Rajasthan are seasonal. Lakes in the semi
arid region of Rajasthan i.e. a region of inland drainage are seasonal. For
example, the Sambhar Lake in Rajasthan is a seasonal salt water lake which is
used for producing salt.

• Most of the freshwater lakes are in the Himalayan region. They are of glacial
origin. The Wular Lake in Jammu and Kashmir is the result of tectonic activity
which is the largest freshwater lake in India. Some other important freshwater
lakes are Dal Lake, Bhimtal, Nainital, Loktak and Barapani.

• Some may have been formed by wind, river action and human activities. A river
meandering across a floodplain forms cut-offs that later develop into ox-bow
lakes.

• Spits and bars form lagoons in the coastal areas. Eg: the Chilika lake, the Pulicat
lake and the Kolleru lake.

• Apart from natural lakes, the damming of the rivers for the generation of hydel
power has also led to the formation of lakes. For example Guru Govind Sagar,
Barapani etc.

Importance of Lakes

Lakes are useful to human beings in many ways:

1. Lakes help to regulate the flow of a river and prevent flooding in the rainy season.
2. During the dry season, these lakes help to maintain an even flow of water and
also support agriculture.
3. Lakes can also be used for developing hydel power.
4. Lakes moderate the surrounding climate
5. Lakes maintain the aquatic ecosystem and help in ecological balance.