By Andrew Lee and Oliver
Royle
Definition
• The Water Cycle, also know as the hydrological cycle, is the journey
that water takes through mainly evapotranspiration, condensation,
precipitation, infiltration, percolation and runoff. The water cycle is a
closed system, meaning that no water is added or taken from the
cycle, although the distribution of the water changes.
Concepts
• Evapotranspiration is the process of evaporation and transpiration
combined.
• Evaporation is the process in which the water turns into a gaseous
state from a liquid state.
• Transpiration is the discharge of water vapour into the atmosphere
through plants.
• Condensation is the process by which water changes to a liquid
state from a gaseous state.
• Infiltration is the movement of water downward into the earth’s
surface.
• Percolation is the descending movement of liquid through the solid
or rock.
• Runoff is the water that flows over the surface of the land towards
rivers, lakes, oceans etc.
• Precipitation is when the water passes through the atmosphere to
the earth’s surface. E.g. rain, snow, etc.
Mind Map
Create M ore
Dams to
Capture Water
Quality
M ore
Treatment
Plants
Quantity
Rising
Population
M ore
Waste
Water
Human
Impacts
Less
available
potable
water
Poor
Irrigation
The Water
Cycle
Evapotranspiration
Iinfiltration
and
Percolation
Precipitation
Condensation
Transpiration
Evaporation
Human Impacts
• Humans have impacted the water cycle in many ways.
Population increases, rising living standards and
industrial and economic growth have put a lot more
stress on the environment. Some activities can change
the hydrologic equation and can affect the quantity and
quality of natural water resources available to current
and future generations.
• The water used by households, industries, and farms
has increased and people demand it to be clean. The
amount of fresh water is limited and the easily accessible
sources have been developed. As the population
increases, so will our need to withdraw more water from
rivers, lakes and aquifers, threatening local resources
and future water supplies.
Human Impacts
• A larger population will not only use more water but will
discharge more wastewater from domestic, agricultural,
and industrial wastes. Poor irrigation practices also raise
soil salinity and evaporation rates. All of these factors
place far more pressure on existing water resources.
• Drainage of water through road drains and city sewer
systems alters the rates of infiltration, evaporation, and
transpiration. All of these various effects determine the
amount of water in the water system and can result in
negative consequences for river watersheds, lake levels,
aquifers, and the environment as a whole.
Water Cycle (Human Impact)
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•
•
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Evaporation is when moisture is lost directly to the atmosphere from either land or
ocean. The rate of this depends on temperature, wind velocity, humidity and hours of
sunshine.
Condensation is the process by which water changes to a liquid state from a gaseous
state. The rate of condensation depends on air temperature and the rate of
atmospheric cooling.
Evapotranspiration is the process of evaporation and transpiration combined. Both
components of this involve transpiration of water from a liquid state to a gaseous
state.
Transpiration is the discharge of water vapour into the atmosphere through the leaves
of plants. The rate of this depends on the time of the year, type of vegetation and the
length of the growing season.
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•
•
•
Precipitation is when the water passes through the atmosphere to the earth’s surface.
E.g. rain, snow, etc. This happens when large masses of moist air are cooled rapidly
below dew point. When the liquid becomes too heavy for the atmosphere to support it,
after a further condensation, precipitation occurs.
Infiltration is the movement of water downward into the earth’s surface. The water
enters the soil and passes through many different layers of the soil profile. The rate of
this depends on the amount of water already in the soil. The water continues
downward until a sild called its infiltration capacity, then it is transferred across as
ground water.
Percolation is the descending movement of liquid through the solid or rock.
Runoff is the water that flows over the surface of the land towards rivers, lakes, oceans
Management Techniques
• Distributing different quality water: This
technique involves using high quality water for
drinking water and bathing water whilst making
use of lower quality water for gardening and
washing cars etc. This conserves the amount of
fresh water which we could have a huge use for
in the future.
• Water Tanks: Water tanks can be used to
withhold as much water as possible. This lowers
the strain on main water supplies which is good
for both drought and the environment.
Management Techniques
• The water tank management technique is
similar to the technique of distributing
different quality water as they both try to
lower the amount of water coming out of
main water supplies such as dams. It is
also very different, as water tanks are
individual and it uses just fresh water. The
distribution system uses unfiltered water
for purposes such as gardening and does
not have to be individual.
Video
• http://www.youtube.com/watch?v=EHi4IU7JQ5Q
• This video is a great example to show how humans are
not conserving our precious resources. The
management techniques in this video include creating
filters and catchments underneath the streets of Los
Angeles. The people of Los Angeles have made a great
improvement in the retention of rainwater in conserving it
for the future. Before the catchments were built, the city
had lost an estimated 80 billion galleons of rainwater.
For a city who imports 85% of its rainwater it is way too
much. Efforts like this should be used all over the world.
Sydney especially receives a lot of rain, however
Warragamba Dam does not. If Sydney employed this
technique it could help the drought effort exponentially.