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1. Hydrological Cycle
Presented By: Architect Md. Mahamudur Rahman Khan Papon
Email: ecodesignarch@gmail.com

2. Water is a transparent and nearly colorless chemical substance that is the main constituent of
Earth's streams, lakes, and oceans, and the fluids of most living organisms.
Its chemical formula is H2O, meaning that its molecule contains one oxygen and two hydrogen atoms,
that are connected by covalent bonds.
Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature
and pressure; but it often refers also to its solid state (ice) or its gaseous state (steam or water vapor).
It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, and
atmospheric humidity.
Definition of Water:
Distribution of water:
Ocean – 97%
Surface fresh water – 03%
• Glaciers – 69%
• Underground – 30%
• Lakes, Rivers &Swamps – Less then 1%
Use of Water:
• Used by human – 1%
• Unused – 99%
Water Distribution on Earth Surface

3. Definition of Hydrological Cycle:
Fig. Hydrological cycle
The water cycle, also known as the hydrological cycle describes the continuous
movement of water on, above and below the surface of the Earth.
The water moves from one reservoir to another, such as from river to ocean, or from the
ocean to the atmosphere, by the physical processes of:
• Evaporation
• Condensation
• Precipitation
• Surface runoff
• Infiltration
In doing so, the
water goes through
different phases:
 Liquid
 Solid (ice) and
 Vapor.

4. Process of Hydrological cycle:
Evaporation:
 The transformation of water from
liquid to gas phases as it moves
from the ground or bodies of water
into the overlying atmosphere.
 The source of energy for
evaporation is primarily solar
radiation.
 90% of the moisture found in the
atmosphere is supplied
by evaporation.
 Only about 10 % of the water
evaporated from the oceans is
transported over land and falls as
precipitation.
 Once evaporated, a water
molecule spends about 10 days
in the air.
Fig. Evaporation

5. Transpiration:
o It is the evaporation of water from
plants through stomata. Stomata are
small openings found on the underside
of leaves that are connected to
vascular plant tissues. In most plants,
transpiration is a passive process
largely controlled by the humidity of the
atmosphere and the moisture content
of the soil.
o 10% of the moisture found in the
atmosphere is released by plants through
transpiration.
Fig. Stomata
Fig. Transpiration

6. Condensation:
o Condensation is the process by which water vapor in the air is changed into
liquid water.
o Condensation is crucial to the water cycle because it is responsible for the
formation of clouds.
o It is the process whereby water vapour in the atmosphere is returned to its
original liquid state.
o In the atmosphere, condensation may appear as clouds, fog, moist, dew or
frost depending upon the physical condition of the atmosphere.

7. Precipitation:
 Precipitation is water released
from clouds in the form of rain,
freezing rain, sleet, snow, or hail.
 Precipitation occurs when water
vapour in the atmosphere
condenses into clouds and
falls to the earth.
 It is the primary connection in the
water cycle that provides for the
delivery of atmospheric water
to the Earth.
 Most precipitation falls as rain.

8. Run-off:
 Runoff is the movement of land water to the
oceans, chiefly in the form of rivers, lakes,
and streams.
 Only about 35% of precipitation ends up in
the sea or ocean. The other 65% is
absorbed into the soil. Some of it too will
evaporate.
 Everyday about 100 cubic km of water
flows into the seas from the world’s rivers.
 The Amazon River, the world’s largest river
provides about 15% of this water.
 Run-off is not constant. It decreases during
periods of drought or dry season and
increases during rainy season, storms
and periods of rapid melting of snow and
ice.

9. Infiltration:
 Infiltration is the process by which water on the ground surface enters the soil.
 Infiltration rate in soil science is a measure of the rate at which soil is able to
absorb rainfall or irrigation.
 The rate decreases as the soil becomes saturated. If the precipitation rate exceeds the
infiltration rate, runoff will usually occur unless there is some physical barrier. It is related to
the saturated hydraulic conductivity of the near-surface soil.
 It is measured in inches per hour or millimeters per hour.
 The rate of infiltration can be measured using an Infiltrometer.

10. Conclusion:
The Hydrologic Cycle is constantly happening all around us each and every day and is
an essential part of life. Understanding the global water cycle and how we use water is
essential to planning a sustainable source of water for the future. Water is arguably the
most important physical resource as it is the one that is essential to human survival.
It is necessary so that we have shade from clouds, to water our plants with the falling
rain, and for fish to swimming.

11. Thank you