Water and hydrologic cycle
Elective 5 – Freshwater Biology
Prepared by: Carolyn T. Ringor
Content Outline

Definition of Water

Importance of water in living thing

Common usage of water

Definition of Hydrology

The Hydrologic cycle

Evaporation (Evapotranspiration)

Precipitation

Infiltration


Runoff
Subsurface flow
Water

Water is a colorless, odorless and tasteless liquid

It is made up of 1 oxygen molecule and 2 hydrogen molecules bonded by a
covalent bond
Importance of water in living things

60% of water is found in the human body

70% is found in the brain

90% is found in the lungs

83% is found in the blood which helps digest foods, transports waste and
control body temperature
Usage of water

Water is very vital to life, among the usage of water in our daily lives
includes:

Drinking

Cooking

Irrigations in Agricultural lands

Used to generate electricity (Hydropowers)
Hydrology

Hydrology is the study of movement and distribution of water through out the
earth.
Hydrologic cycle

Water cycle or hydrologic cycle is one among the cycles which makes up the
biogeochemical cycles.

it is the circulation of the water in the earth’s hydrosphere

It involves changes in the physical state of water between solid, liquid and
gas phase.

It also refers to the continuous exchange of water between the atmosphere,
land, surface and subsurface waters and organisms.
Insert water cycle here
Component of Hydrologic cycle:
Evaporation

Evaporation occurs when radiant energy from the sun heats water which
causes the water molecules to become active.

When the water molecules becomes active some of these molecules goes up
in the form of vapour

The transformation of liquid water becoming gas requires energy
Component of Hydrologic cycle:
Evaporation

About 90% of the atmospheric water comes from evaporation, while the
remaining 10% is transpiration.

Transpiration occurs when plant takes in water through the roots and release
it through the leaves

The transpiration is one of the natural processes where water is cleaned by
removing contaminants and pollution from the environment
Component of Hydrologic cycle:
Precipitation

Raising warm air carries water vapor high into the sky where it cools, forming
water droplets around tiny bits of dust in the air.

Some vapor freezes into tiny crystals which attracts cooled water drops. The
drops freezes into ice crystals, forming larger crystals known as snowflakes.


When snowflakes becomes heavy, they starts to fall. When the snowflakes
meets warmer air on their way down, they melt and forms raindrops.


Atmospheric temperature below 32°C
Atmospheric temperature above 32°C
Snowflakes partially melt in the layer of warmer air, then freezes again when
it meets the cold air the ground. This kind of precipitation is called sleet.
Component of Hydrologic cycle:
Infiltration

At some circumstances precipitation actually evaporates before it reaches the
surface.

Infiltration is the transition from surface water to ground water.

The infiltration rate is dependent on the soil and rock permeability.
I
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f
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t
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Surface water
Soil
Rock
Groundwater
Aquifer
Component of Hydrologic cycle: Infiltration


The amount of water that infiltrates the soil varies with the:

Degree of land slope

Soil type and rock type

Amount and type of vegetation

Amount of water in the soil
The more openings in the surface (Cracks, pores and joints) the more
infiltration occurs.
Component of Hydrologic cycle: Run off

Precipitation that reaches the surface of the earth but does not infiltrate the
soil is called run-off.

Run-off comes from melted snow and ice.

Run-off includes variety of ways by which land surface and water moves down
the slope to the ocean.

Not all precipitated water returns to the sea as runoff. Much of it evaporates
before reaching the aquifer or the sea.
Component of Hydrologic cycle:
Subsurface flow

Surface flow incorporates movement of water within the earth, either within
the recharge zone or aquifer. After infiltrating subsurface water may return to
the surface or eventually seep into the ocean