2. What you will
Learn
1. Describe the
hydrological cycle.
2. Describe the river
system.
3. The hydrological
cycle
Continuous
movement of water
is called the
hydrological cycle.
4. Rivers play an important role in the
hydrologic cycle. Study the figure
below. Rainfall
Condensation
Transpiration
Runoff
Evaporation Groundwater
What are the different
processes in the hydrologic
cycle? What role does the
7. Condensation
Warm air cools as it
rises. Water vapour
changes into water
droplets. Small water
droplets combine to
form bigger water
droplets. Million of
11. Importance of river in
the hydrological cycle
Rivers are an
important part of
the hydrological
cycle as they
contain water that is
found on the Earth’s
12. River system
River is a body of
water flowing in a
channel.
Aided by gravity,
rivers always falls
from a higher point to
13. River source
Tributaries
River mouth
Upper course Middle course Lower course
14. Characteristics Along a River —
Channel and River Valley
Upper Middle Lower
Course Course Course
Channel Narrow, Wider, Widest,
shallow deeper deepest
Gradient Steep Less steep Almost flat
Volume of
water Low Higher Highest
15.
16. Drainage Basin &
Watershed
Read the definition
of a watershed and a
drainage basin in your
textbook.
17. Now study the picture below
carefully. Where would you
find, in the picture, the:
• ‘drainage basin’?
• ‘watershed’?
18. Drainage Basin
Drainage basin is
the land area drained
by the main river and
its tributaries.
