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3. Definition
Hydrology is the science that takes into
account the water in the world, existence, and
the distribution cycle, chemical and physical
properties, and reactions to the environment,
including relationships with living things.
Space covers the entire history of existence of
water on the earth

4. Hydrology
Hydro – Water (air)
Logy – Research about (kajian
tentang)

5. Measuring Unit of Water
a) Depth
(mm, cm, m, inch, feet)
b) Volume
(cm3, m3, liter, cube feet, meter hecta(m-ha)
c) Flow rate
(liter/sec/minutes/hours, m3/s)

7. HIDROLOGY DATA CRITERIA
• Trusted
• Continuously

8. Data can be obtained from
 Jabatan Kaji Cuaca
 Jabatan Kerja Raya
 Jabatan Bekalan Air
 Jabatan Geologi dan ukur
 Jabatan Alam Sekitar

9. Hydrological Cycle
• A transition cycle of water (water
transfer) that occur on earth consistently
and naturally

10. Hydrological Cycle


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





Precipitation (P) - Curahan
Evapotranspiration (E) – Sejat Peluhan
Evaporation - Sejatan
Transpiration (T) - Pepeluhan
Surface Run-Off (R) – Larian Permukaan
Infiltration (I) – Penyusupan
Ground Water (G) – Air Bumi
Condensation (C) – Pemeluwapan
Convection - Olakan

12. Basic Components of the hydrological
Cycle
Precipitation
The transfer from vapor form to liquid form. It is a
continuous process in which water is evaporated from
oceans, moves inland as moist air masses.
The precipitation that falls from clouds onto the land surface.
For example - rain , snow, dew, hills
Evaporation /Evapotranspiration
The transfer of water from liquid form to vapor form. Rainfall
is retained in the soil near where it falls and returns to the
atmosphere

13. Transpiration (T)
Water inside of plants is transferred from the plant to the
atmosphere as water vapor
Infiltration (I)
Infiltration is the physical process involving movement of
water
through the boundary area where the atmosphere interfaces
with the soil. Part of rain water infiltrated to the soil due to
gravitational force and pressure different.
Surface Runoff (R)
The transfer of liquid form within a catchment areas surface
runoff that flows over the land surface and through channels,
subsurface runoff that infiltrates the surface soils and moves
laterally towards the stream

14. Effect of land use to the hydrological
cycle
•
•
•
•
•
•
•
Land slide
Land erosion
Flood
Global Warming
Land Pollution
Water Pollution
Air Pollution

15. Hydrolologic Continuity Equation
(The water Balance)
A statement about water balance and water
conservation law accurring in a clearly defined
catchment area.
dS/dt = I – O
dS/dt = rate of storage change
I = amount of water input
O = amount of water output

16. Example of Calculation
• A storage allow to received inflow and outflow
respectively at rate 10 and 15 m3/s for 24
hours. Calculate the change of volume in that
storage in 24 hours.
• dS/dt = I – O
• dS = (I – O) dt
• dS = (10-15) m3/s x[ 24 x 60 x 60]s
• dS = - 4.32 x 105 m3

17. • In two month Padang Melati district predict to
received rain 240 mm. Evaporation is 80 mm and
infiltration 20 mm. The catchment are is 56 km2 .
• Estimate the volume of surface runoff.
• R=P–E–T–I
• P = 240 mm
• E = 80 mm
• T=0
• I = 20 mm

18. •
•
•
•
•
•
•
R=P–E–T–I
= 240 – 80 -20
= 140 mm @ 0.14 m
Volume of surface runoff
= R x Area
= (0.14) x ( 56 x 106)
= 7.84 x 106 m3

19. Problem Set
1. Explain the hydrological process below
– Infiltration
– Transpiration
– Base Flow
2. There are two rivers flow into the catchment
area 1500 km2. The total discharge of two rivers
are 7.5 x 1010 m3/year. Record are made showing
the loss due to the transpiration is 10% of the
monthly rainfall. Determine the average monthly
rainfall for the catchment area.

20. Problem Set
3. Sungai Kinta catchment is expected to receive 240mm
of rain. Transpiration is approximately 55 mm and the
infiltration is estimated 20 mm. The catchment area is
65 km2. Estimate the volume of runoff.
4. The stream’s storage reach at a particular time is 72 x
103 m3. At that time the inflow and outflow of the
stream are 16m3/s and 25 m3/s respectively. Two hours
later the inflow and outflow are 23 m3/s and 30 m3/s
respectively. Calculate the change and the new storage
of the reach at the end of two hours.

21. 5. The drainage area of a village is 2.59 x 1010 m 2. If the
mean annual runoff is determined to be 19.82 m3/s and the
average annual rainfall is 20 cm, estimated the evapo
transpiration losses for the area in cm/year.
6. State four characteristics of rainfall and the
measurement unit.
7. Within 6 months of the Sungai Lui catchment area is
estimated to receive rainfall of 350 mm. Evaporated in the
estimate of 100 mm and diffusion into the subsurface is
estimated to 40 mm. Estimate the volume in cubic meters
of area to be stored in the reservoir if the basin area is 85
km2.
8. Calculate the average daily evaporation rate in
(ha.cm)/day on annual evaporation from lake with a
surface area of 25 x 106 m2 is 320 cm. (1ha = 10000 m2)

22. Unit Converter Exercise
65 km2
72000 m3/year
8.5 x 103 m3/year
157 cm
82 mm
482 mm3
300 ml
57 cm3
360 mm2
250 cm3/month
–
–
–
–
–
–
–
–
–
-
m2
cm3/day
cm3/month
m
m
m3
cm3
m3
m2
m3/s