What is the hydrological cycle?

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22 Φεβ 2014 (πριν από 3 χρόνια και 3 μήνες)

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What is the hydrological cycle?

Topic 4: Water World


The hydrological
cycle or water
cycle is the
movement of
water between
its different
forms; gas (water
vapour), liquid
and solid (ice)
forms.

Topic 4: Water World

Processes in the hydrological cycle:

Inputs

Outputs

Stores

Flows/transfers


Topic 4: Water World


Topic 4: Water World

Water scarcity

Topic 4: Water World

So far, freshwater is not scarce on a global scale.
However, many parts of the word are now
experiencing water
stress.


Write down what you understand the term
“water stress” to mean



Water scarcity comes in two types
:


Physical scarcity


shortages occur when demand exceeds
supply. I.e. There is not enough good quality water
available for everyone to have the amount they need


Economic Scarcity


when people cannot afford the water
even if it is readily available.


Topic 4: Water World

Water stress

Topic 4: Water World

So far, freshwater is not scarce on a global scale.
However, many parts of the word are now
experiencing water
stress.




Water stress
occurs when the demand for water exceeds
the amount available during a certain period, or when it is
not good enough quality to use.



Topic 4: Water World

Causes of decline in water
availability and water quality

Topic 4: Water World

Industrial
development


The growth of
manufacturing
industries is based
on water supply
especially steel and
paper. They also
rely on rivers and
oceans to dump
waste.

Decline in water
availability and
quality

Population growth

World population
grew from 2.5 to
6.2 billion between
1950 and 2000. 7
billion people are
estimated to have
insufficient water
by 2050

Agriculture Demands


Rising population increases the
demand for food and water
needed for farming. The area
of irrigated land doubled
during the 20
th

century.
Water shortages may
threaten future food supplies.

Urbanisation

By 2025 nearly
60% of the
worlds population
will live in urban
areas. The water
and sanitation
supply won’t be
able to cope.

Energy

Developing countries
have vast untapped
HEP resources. But
storing water in
reservoirs increases
the amount of water
lost through
evaporation and
water related
diseases.

Climate Change

Global warming and climate
change will affect rainfall
and water availability .
Areas already experiencing
shortages are likely to
experience lower rainfalls.
Dry areas will be hardest
hit.

Topic 4: Water World

Living with water shortage

What case study did we use?

Topic 4: Water World

Sahel: Case study of an area with a
poor supply of water


The Sahel is a part of Africa
which has a poor supply of
water. There is also an
Economic Scarcity of water as
the area is very poor and so
cannot afford to store or
transfer the water to the most
needed places.



The area suffers from
Desertification (the spreading
of deserts) due to the lack of
rainfall and human activities
such as overgrazing, which
leaves the soil open to
erosion.


Causes of desertification

Topic 4: Water World


Topic 4: Water World

How humans affect water quality

Topic 4: Water World

Topic 4: Water World

Topic 4: Water World

Topic 4: Water World

Minamata

disease in Japan
-

caused by
mercury poisoning. In the late 1950s
tonnes of
toxic mercury
was released
into
Minamata

Bay in Japan which
affected fish and shellfish. These were
then consumed by humans which lead
to severe mercury poisoning and, in
many cases, death.

Human excrement
-


Cholera bacteria spread easily in
river water when contaminated
with human waste.

Plastic Bags

Block waterways and sewers
which worsens flooding
problems particularly in
Bangladesh during monsoon
season. Plastic bags also get
trapped by vegetation along
river banks, providing pools of
still warm water where malaria
carrying mosquitoes will breed.

Human interference to the
hydrological cycle

Topic 4: Water World

Human interference with the Water
Cycle

Humans can have a negative impact on the water cycle through

deforestation
and
overabstraction
.


Overabstractio
n
-

means too much water is being taken from the river, lake
or other water source.


Deforestation

has three impacts on the water cycle:


1.Interception is reduced as there are fewer trees to “catch”

the water. This means that the water will travel more quickly into

the river= increases chance of the river flooding.


2.The tree roots no longer hold the soil together, so it is more

easily eroded by the rainfall and washed into the river. This

leads to sedimentation (the river filling with silt/soil) and

therefore flooding.


3.Less evapotranspiration will take place and this can lead to

less rainfall and desertification.



Topic 4: Water World

Large Scale solution to water
management

Topic 4: Water World

Costs (problems)


Benefits


Loss of land as it is flooded by the reservoir


Less flood risk as flood peaks are smoothed out.

Shrinking

sandbanks mean some animals lose habitat.


Create

reservoirs which provides

regular

all
-
year water supplied for cities like Las Vegas

Rates of silt transportation

has reduced and made the
water cooler downstream as silt heats up in sunlight. This
has lead to 4 species of fish being lost.

Very

expensive! Local people have little input or say on
how it is managed.

Large
-
scale water management
-

The
Colorado River and the Hoover Dam


The Colorado River feeds the need of 7
US states and Mexico. Water
management techniques have mean that
US cities and farms have access to
reliable water supplies all year round.


The Hoover Dam holds an enormous
amount of water for desert cities like Las
Vegas. Water is piped along man
-
made
constructions called aqueducts.

Topic 4: Water World

Small
-
scale solutions to water
management

Topic 4: Water World

Small
-
scale water management: Rainwater harvesting
(pumpkin tanks) and
Afridev

hand pump

Afridev

Hand pump
-

Tanzania, East Africa.

Facts:


Life expectancy is 46


70% rural population
and 30% of urban
population have no
access to safe, clean
water


Diarrhoea accounts for
at least 20% of infant
deaths

Topic 4: Water World

WaterAid

brings intermediate technology to communities that
need clean water by helping villages construct wells to access
safe, clean underground water. The pumps are dug 24 metres
deep and are fitted with an
Afridev

handpump
. Local people
are trained to manage the pump in case it breaks down giving
them ownership of the scheme.

Rainwater
harvesting
(Pumpkin tank)

Appropriate or intermediate
Technology

Topic 4: Water World


Development schemes that meet the needs of
local people and the environment in which
they live.

Topic 4: Water World