156 The impactsof climate changeWithdrawal, km3 (year
−^1 )
Figure 7.6Global water withdrawal for different purposes, 1900–1995, and
projected to the year 2025 in cubic kilometres per year. Losses from reservoirs
are also included. As some water withdrawn is reused, the total water
consumption amounts to about sixty per cent of the total water withdrawal.tropical forests, the jungle teems with life of enormous variety. In drier
regions sparse vegetation exists, of a kind which can survive for long
periods with the minimum of water; animals there are also well adapted
to dry conditions.
Water is also a key substance for humankind; we need to drink it, we
need it for the production of food, for health and hygiene, for industry and
transport. Humans have learnt that the ways of providing for livelihood
can be adapted to a wide variety of circumstances regarding water supply
except, perhaps, for the completely dry desert. Water availability for
domestic, industrial andagricultural use averaged per capita in different
countries varies from less than 100 m^3 (22 000 imperial gallons) per year
to over 100 000 m^3 (22 million imperial gallons)^21 – although quoting
average numbers of that kind hides the enormous disparity between those
in very poor areas who may walk many hours each day to fetch a few
gallons and many in the developed world who have access to virtually
unlimited supplies at the turn of a tap.
The demands of increased populations and the desire for higher stan-
dards of living have brought with them much greater requirements for
fresh water. During the last fifty years water use worldwide has grown
over threefold (Figure 7.6); it now amounts to about ten per cent of the
estimated global total of the river and groundwater flow from land to sea