Geology Reference
In-Depth Information
CHAPTER 3
Chemistry of Freshwaters
MARGARET C. GRAHAM AND JOHN G. FARMER
School of GeoSciences, University of Edinburgh, Crew Building, King's
Buildings, West Mains Road, Edinburgh EH9 3JN
3.1 INTRODUCTION
Water is essential for all life on Earth. As the Earth's population
continues to increase rapidly, the growing human need for freshwater
(e.g. for drinking, cooking, washing, carrying wastes, cooling machines,
irrigating crops, receiving sewage and agricultural runoff, recreation, and
industrial purposes) is leading to a global water resources crisis. Rees
1
has
commented that 'there is a growing consensus that if current trends
continue, water scarcity and deteriorating water quality will become the
critical factors limiting future economic development, the expansion of
food production, and the provision of basic health and hygiene services to
millions of disadvantaged people in developing countries'. In 2003, the
UN International Year of Freshwater, 20% of the world's people lacked
good drinking water and 40% lacked adequate sanitation facilities.
2
The inventory of water at the Earth's surface (Table 1)
3
shows that the
oceans, ice caps, and glaciers contain 98.93% of the total, with ground-
water (1.05%) accounting for most of the rest, and lakes and rivers
amounting to only 0.009% and 0.0001%, respectively.
3
The average
annual water withdrawal for use by humans is currently about 4000
km
3
, of which 69% is used by agriculture, 21% by industry/power, and
10% for domestic purposes.
2
Figures vary widely between continents and
countries. On a per capita basis, North America withdraws seven times as
much freshwater as Africa. The USA (41% agriculture, 46% industry/
power, 13% domestic) withdraws almost 20% of its renewable freshwater
resources each year, in comparison with 7% for the UK (3%, 75%, 22%),
22% for China (68%, 26%, 7%), 33% for Poland (8%, 79%, 13%), 51%
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