The impact ofclimate change onfresh water resources 157(Figure 7.5). Two-thirds of human water use is currently for agriculture,
much of it for irrigation; about a quarter is used by industry; only ten
per cent or so is used domestically. Increasingly, water stored over hun-
dreds or thousands of years in underground aquifers is being tapped for
current use. With this rapid growth of demand comes greatly increased
vulnerability regarding water supplies.
The extent to which a country iswater stressedis related to the
proportion of the available freshwater supply that is withdrawn for use.
Withdrawal exceeding twenty per cent of renewable water supply has
been used as a threshold of water stress. Under this definition approx-
imately 1.7 billion people, one-third of the world’s population, live in
water-stressed countries. This number is projected to rise to around five
billion by 2025, dependent on the rate of population growth, this without
taking into account any effect on water supplies due to climate change.
For instance, in India about seventy-five per cent of available water is cur-
rently used for irrigation. There is therefore very little surplus for future
growth, the only river in north India with a surplus is the Brahmaputra.
Similar situations where nearly all the available water is currently used
prevail in much of central and western Asia.^22 Many other developing
countries especially in Africa face similar situations.
A further vulnerabilityarises because many of the world’s major
sources of water are shared. About half the land area of the world is
within water basins which fall between two or more countries. There are
forty-four countries for which at least eighty per cent of their land areas
falls within such international basins. The Danube, for instance, passes
through twelve countries which use its water, the Nile water through
nine, the Ganges-Bramaputra through five. Other countries where water
is scarce are critically dependent on sharing the resources of rivers such as
the Euphrates and the Jordan. The achievements of agreements to share
water often bring with them demands for more effective use of the water
and better management. Failure to agree brings increased possibility
of tension and conflict. The former United Nations Secretary General,
Boutros Boutros-Ghali, has said that ‘The nextwar in the Middle East
will be fought over water, not politics’.^23
The impact of climate change on fresh water resources
The availability of fresh water will be substantially changed in a world
affected by global warming. We saw in Chapter 6 (Figure 6.5(b)) that,
although there remains substantial uncertainty in model predictions of
precipitation change, it is possible to identify some areas where it is