194D
DESALINATION
INTRODUCTIONOur planet, the earth or gaia, is a water place. Water occu-
pies 70% of the total earth’s area, about 360 10 12 m^2 ,
and the total water volume that covers the earth’s surface
is about 1.40 10 18 m^3. This makes the planet earth a
very large water reservoir, nevertheless practically, these
huge amounts of water are not directly usable, as 97% of
this water is the seawater of the open seas and oceans and
only 3% consist of fresh and brackish water, i.e., 0.042
10 18 m^3. From these 3.0% fresh water reserves only a por-
tion (0.014%) is in liquid form in rivers, lakes and wells
directly available to us for immediate use, the rest can be
found as glacier, icebergs and very deep water of geological
reservoirs.
Fresh water, for all of historical times has been an uncon-
trollable happening of nature wherever and however found.
In the Bible “good land” is described as one “of brooks of
water, of fountains, and depths that spring out of valleys and
hills,” for water is a precious source of development and civ-
ilization, because water and civilization are two inseparable
conceptions.
From antiquity up to our times, rivers, seas, oases, and
oceans have attracted man to their shores. As a rule, towns
and countries have grown along rivers. Egypt for example
was considered as “the gift of the river.” Egypt is a typical
historical example of the influence of water to the birth and
development of a civilization.
As a largely developed agricultural country, Egypt was
able to master the river and had most of the time such an
abundant harvest, that it became the main wheat-exporting
country in the whole Mediterranean. The Egyptians learned
to determine the seasons of the year by the behaviour of the
river. Inundation, Emergence of the fields and Drought were
their seasons. The first calendar was created in this way and
out of this was derived the modern calendar.
Unfortunately, fresh water, and even seawater has not
had our proper attention, respect and treatment. Due to the
increase of population, especially in certain regions, and
the increase of living standards, water demand increasedexponentially, and wells or other fresh water sources run dry.
The great population increase multiplies the total withdrawal.
In some areas twice or more as much water is being drawn
out of the ground as sank into it, thus the water table drops
every year a few meters and water shortage increases dra-
matically, especially in dry years.
In modern large civic centers, opening of the tap pro-
vides us with as much fresh water as we are able to waste.
The notion of lack of water is usually a matter we very
seldom think of. However, at the same time there are places
where water is so scarce that there are serious problems of
existence, as is the case these days in many places in Africa.
Generally it is not realized that fresh water represents only
3% of the total reserves in the world and that 75% of it is
immobilized as ice. Modern agriculture also requires con-
siderable amounts of good water to meet increasing food
requirements. There is a tremendous requirement of water to
run industrial plants, to produce all kinds of goods but also
all kinds of polluting effluent.
The quantity of water used varies from location to loca-
tion throughout the day and throughout the year, as many
factors influence this variation. The more important factors
include the economics of a community, its geographic loca-
tion, and the nearby availability of the water source or the
transportation distance from the source.
Climate is the most common cause of water lack or of
water insufficiency. Sparse rainfall to feed streams, wells
and the soil for agricultural production of crops exhausts
water reserves. The most arid areas are the deserts, where
no rain exists and some underground waters most of the time
are salty or brackish. About 19% of the total land surface
of the earth on all continents but Europe, is covered by des-
erts, which are surrounded by semi-arid lands where existing
water is insufficient.
Coastal deserts, where the lack of water is as high as
in the interior deserts, cover about 33,000 km^2 around the
world, the greatest part of which is found in the Middle East,
along the Persian Gulf, adjoining parts of the Arabian Sea
and the Indian Ocean. The coastal deserts are divided into
four main categories, according to their climatic conditions.C004_001_r03.indd 194C004_001_r03.indd 194 11/18/2005 10:18:47 AM11/18/2005 10:18:47 AM