This presentation will provide complete knowledge on hydrologic cycle and its components.

1. Hydrologic cycle
Vijitha Vikneshwaran
Lecturer(Temporary)
Faculty of Technology
University of Jaffna

2. Introduction
• Water is the soul of our life.
• It is the most basic need for our,
• Survival
• Safety
• Progress
• Development
• Oceans are the largest reservoirs, holding about 97.5% of
the earth’s water.
• The remaining 2.5% is the freshwater, where about 79%
of it is stored in ice caps and glaciers.
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3. • About 20% of freshwater is groundwater, stored in
sediments and rocks below the surface of the earth.
• Rivers, streams and lakes together contain less than 1%
of the freshwater.
• Water can occur in 3 physical phase,
• Solid
• Liquid
• Gas
• Water can quickly change its phase according to
environmental condition and place of occurrence.
Introduction,cont….
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4. Introduction,cont….
• Functions of the earth is depend on several natural
cycles.
• Carbon cycle
• Nitrogen cycle
• Hydrologic cycle and other
• Hydrologic cycle forms the fundamental concept in
hydrology .
• The hydrologic cycle can be subdivided into three major
systems,
• The oceans : Major reservoir and source of water
• Atmosphere : Carrier and deliverer of water
• Land : User of water
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5. Hydrologic cycle
• Hydrologic cycle can be defined as,
“The pathway of water as it moves in its various
phases to the atmosphere, to the earth, over and through
the land, to the ocean and back to the atmosphere”.
• It considers the movement, loss and recharge of earth’s
water.
• The study of hydrologic cycle is important as the water is
essential for survival of life and is an important input in
many economic activities
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6. Hydrologiccycle,cont….
Figure 01: Hydrologic cycle
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7. • The water cycle is the continuous circulation of water
within the hydrosphere.
• It involves the movement of water into and out of
various reservoirs like,
• Atmosphere
• Land
• Surface water
• Ground water
• This cycle is driven by radiation from the Sun.
• The movement of water within the water cycle is the
subject of the field of hydrology.
Hydrologiccycle,cont….
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8. • The water moves from one reservoir to another by the
physical processes.
• Such processes are,
• Evaporation
• Transpiration
• Condensation
• Precipitation
• Interception
• Percolation
• Infiltration
• Runoff
• Subsurface flow.
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Hydrologiccycle,cont….

9. Evaporation
• It is the process by which liquid turns into a gas.
• Water turns into vapor when heat energy is applied to
raise its temperature to 100°C.
• Water in the liquid state is a compound, and the heat
breaks up the bonds into water molecules, which is
gaseous.
• Since water covers about 70% of the entire surface of the
earth, there is a massive surface area that helps with the
absorption of the sun’s heat.
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10. Evaporation,cont…..
• About 90% of moisture in the atmosphere comes from
the oceans, seas and lakes.
• The amount of moisture that gets into the atmosphere
via evaporation over the oceans is more than the
precipitation it receives.
• The evaporation of moisture on land is less than the
precipitation it receives.
• Rising air currents, resulting from unequal air pressure,
lift the vapor high into the atmosphere.
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11. • Sometimes ice can turn directly into vapor without first
turning into liquid.
• This phenomenon is common in arid climates.
• This happens where dry winds hitting snow sucks up the
moisture, changing the snow directly into vapor.
• This process is called sublimation.
• The entire water cycle is driven by the sun’s heat.
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Evaporation,cont…..

12. 12
Evaporation,cont…..
Figure 02: Evaporation

13. Transpiration
• It is the process by which moisture is carried through
plants from roots to small pores on the underside of
leaves.
• Then the moisture changes to vapor and is released to
the atmosphere.
• Transpiration and evaporation of water are inseparable
process in plant and called as evapotranspiration.
• About 10% of the moisture in the atmosphere is
provided by the process of evapotranspiration.
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14. • The amount of water transpired depends on the,
• Type of plant
• Humidity
• Availability and intensity of sunlight
• Precipitation
• Soil type
• Soil moisture
• Surrounding temperature
• Wind movement around the plant
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Transpiration,cont……

15. 15
Transpiration,cont……
Figure 03: Transpiration

16. Condensation
• It is the process by which water vapor in the atmosphere
turns into water.
• It is the opposite of evaporation.
• This is the cloud formation stage.
• Cooler temperatures are essential for condensation.
• As long as the temperature in the atmosphere is high, it
can hold the water vapor and delay condensation.
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17. • As water vapor rises into the atmosphere, they mix up
with particulate matter in the atmosphere.
• These are very tiny particles of dust, soot and salt and
called aerosols.
• As the surrounding temperatures fall, the water vapor
turns into very tiny particles of water and ice crystals.
• The water particles bump into the aerosols and stick
together.
• As more and more water particles and aerosols stick
together, clouds are formed.
• This process is known as coalescence.
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Condensation,cont….

18. • With time, the clouds become heavier with water.
• That develops into rain-bearing clouds.
• Cloud droplets ranges from sizes between 10 µm to 1 mm.
• Saturation is achieved when there is so much moisture in the
atmosphere far more than the air in that region can take.
• Once it happens, the water/ice crystals are ready to come
down in the form of precipitation.
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Condensation,cont….

19. 19
Condensation,cont….
Figure 04: Condensation

20. Precipitation
• Precipitation is defined as the liquid or solid products of
the condensation of water vapor falling from clouds or
deposited from air onto the ground.
• It includes,
Rain
Hail
Snow
Dew
Rime
Fog
Mist
Glaze
Sleet
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21. • After condensation, the size of water droplets in the
atmosphere gets bigger.
• So the water particles bump into each other.
• Then the force of gravity on water particles get increased
more than the wind or air currents holding it.
• There fore the water tends to come down.
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Precipitation,cont….

22. • Particulate matter plays an important role in the
formation of water droplets.
• They serve as a nucleus around which the water will
settle.
• This is why rainwater is not always pure.
• Rain water may contain various minerals, depending on
the particulate matter in the atmosphere.
• The amounts of water that fall from the sky vary a lot.
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Precipitation,cont….

23. Precipitation,cont….
Rain
• Most common type of precipitation
• Liquid droplets
• Two different form
• Showers : Heavy, Large drops, Last for a period of time
• Drizzles : Small droplets, Last longer
Figure 05: Rain
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24. Snow
• Second most common type of precipitation
• Forms when water vapor turns directly into ice without
ever passing through liquid sate
Figure 06: Snow
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Precipitation,cont….

25. Hail
• Created when moisture and wind are together
• Ice crystals form inside the cumulonimbus clouds
• Shapes : Spherical, Conical and Irregular
Figure 07: Hail
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Precipitation,cont….

26. Dew
• Small drops of water that appears on cool surfaces(grass)
in the morning
• Forms due to condensation of atmospheric vapor in the
colder night air
Figure 08: Dew
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Precipitation,cont….

27. Rime
• White opaque deposit of ice granule
• Forms by rapid freezing of super cooled water drops
impinging on exposed surface.
Figure 09: Rime
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Precipitation,cont….

28. Sleet
• Consists of transparent, globular, solid grains of ice
• Forms by the freezing of raindrops or largely melted ice
crystals falling through a layer of sub freezing air near the
earth surface.
Figure 10: Sleet 28
Precipitation,cont….

29. Fog
• Same as cloud
• This is a cloud forms near the earth surface
• There are 4 types:
• Radiation fog
• Advection fog
• Upslope fog
• Evaporation fog
Figure 11: Fog
29
Precipitation,cont….

30. Mist
• Bunch of small water droplets in the air
• Forms when the cold air occurred above a warm surface
• Very similar to fog and only differ in their visibility
Figure 12: Mist
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Precipitation,cont….

31. Glaze
• Clear and smooth ice coating
• Forms on exposed surfaces by the freezing of super
cooled water deposited by rain or drizzle.
Figure 13: Glaze
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Precipitation,cont….

32. Interception
• It refers to precipitation that does not reach the soil, but
is instead intercepted by the leaves, branches of plants
and the forest floor.
• It occurs in the canopy and in the forest floor or litter
layer.
• It eventually evaporates back to the atmosphere rather
than falling to the ground.
• So that it leads to loss of precipitated water that reaches
drainage basin.
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33. 33
Interception
• The amount of water that it intercepted depends on,
• Duration of the storm
• Wind speed
• Temperature
• Amount of foliage present
Figure 14: Canopy interception

34. Runoff
• It is precipitation that did not get absorbed into the soil
or did not evaporate into atmosphere.
• Runoff made its way from the ground surface into places
that water collect.
• It causes erosion and water pollution
• It carries soil particles, chemicals and other substances
on the ground to the water bodies.
• Only about 35% of precipitation ends up in the sea or
ocean.
• The other 65% is absorbed into the soil and some of it
evaporates too. 34

35. The amount of runoff depends on,
• The topography of the land
• Areas with lots of hills and valleys: Water tends to have
little time to be absorbed into the soil and reach the
water bodies quickly.
• Plain and level area: Water tends to have more time to
be absorbed into the soil and also gets evaporated.
• Nature of the soil
• Areas with soft, porous soils absorb more water.
• Areas with rocky non-porous surfaces absorb less
water.
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Runoff,cont….

36. • Amount of precipitation
• Mild showers over long periods: The ground is in unsaturated
condition. So that, the water is absorbed into the soil and some
of it will evaporate too.
• Heavy rain or snow-melts: Huge amount of water floods the area
and leads to more runoff.
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Runoff,cont….
Figure 15: Runoff

37. Infiltration
• water is absorbed into the soil in a process called
infiltration.
• Infiltration occurs in the upper layers of the ground.
• The infiltrated water may also continue further
downwards into the water table.
• It may even go deeper and replenish aquifers and other
water pockets
• This water movement deeper into the ground is called as
percolation.
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38. Infiltration,cont….
• Sometimes water in the ground moves up to the surfaces
and can evaporate or runoff again.
• If there are water bodies nearby, the infiltrated water can
also end up in the water bodies after.
• If there is vegetative cover, the infiltrated water can get
absorbed by plant roots and later transpired.
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Figure 16: Infiltration

39. • The rate of infiltration depends on factors such as,
• Amount of precipitation
• Type of soils
• Amount of vegetative cover over the area
• Pre-saturation levels
• Topography of the land
• Levels of evapotranspiration
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Infiltration,cont….

40. Subsurface flow
• It is the flow of water underground, in the vadose zone
and aquifers.
• Subsurface water may,
• Return to the surface (as a spring or by pumping)
• Eventually seep into the oceans
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41. Human impacts
• Generation of electricity
• Agricultural practices
• Industrial activity
• The mining of ground water
• Altering the nature of the vegetation
• Paving, concrete and the compacting of soil
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42. THANK YOU
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