3
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3. Water on the Earth
5. RISKS AND PROBLEMS RELATED TO WATER
Water scarcity and extreme excess of water are both dangerous. A long absence of
water can cause people and animals to die and the disappearance of vegetation.
However, a sudden excess of water can cause damage to people and crops.
5.1. Flood disasters
Serious floods are often caused by summer or autumn storms, or when heavy rain
falls in the mountains, or there is a rapid melting of snow. These rains last a very short
period of time in mountain areas, but fall very quickly because of the steep incline, and
they can destroy homes, infrastructure and crops.
Flood disasters also occur because of extreme weather phenomena such as
hurricanes
or
tornadoes
. In the summer months in Southeast Asia,
monsoons
occur. The summer rains last for months and cause slow, continuous flooding that
covers crops and cities.
5.2. Water scarcity
Water scarcity occurs when there is very little precipitation or when humans extract
more rainwater than the amount that has fallen, which seriously alters the level of
water in rivers and lakes.
Today, there are extreme cases, such the Aral Sea, in Asia, which was one of the
largest lakes in the world and is now almost completely dry. Lake Chad In Africa, on
the edge of the Sahara Desert, is a similar case: in the 1960s it was 25 000 km
2
and
today it is less than 1 000 km
2
.
In the coastal areas of the Spanish Mediterranean, the enormous demand for water
used for intensive agriculture, tourism and golf courses has caused the depletion of
underground aquifers that feed rivers and wells. This has serious consequences for the
population.
Important
Water scarcity now affects
all the continents. Nearly 1.2
billionpeople (almostone fifth
of the world’s population),
live in areas where there is
a physical scarcity of water,
while 500 million are nearing
this situation...
There is enough drinking
water on the planet to
provide for the seven billion
people who live on it, but the
water is distributed unequally,
wasted, polluted and not
managed sustainably.
Water, the source of life 2005-2015
Department of Economic
and Social Affairs, United Nations
Understand
19.
Look at the image of the flood on the right and
answer the following questions
a)
Where does this type of disaster occur?
b)
Why do they occur?
Create
20.
Write an essay explaining the consequences of an
extended drought on the economy, on people and
animals in an agricultural region.
21.
Find out about major floods that have occurred in
Spain. Explain their causes and consequences. Write
the results of your research in your notebook.
Add
your personal evaluation of these events.
Flooding due to the overflowing of the river Ebro (Navarra)
