Geography Reference
In-Depth Information
11
Water quality and pollution
Bruce Webb
thirteenth century to prohibit washing the
products of charcoal burning in the River Thames
(ibid.)
. Water pollution, and its deleterious
consequences for human and ecosystem health,
has accelerated since the nineteenth century with
the increasing urbanisation and industrialisation of
human society and intensification of agriculture
to support an ever-growing population (UNEP/
WHO 1988). One of the first documented
examples of the inimical effects of bad water
quality concerned the outbreaks of cholera in
London, which were traced by John Snow in 1854
to the gross pollution of the River Thames by raw
sewage. Problems of faecal contamination of rivers
used for public water supply in developed
economies were subsequently largely solved by the
invention of sand filtration and the use of
chlorination.The sequence of problem occurrence
and perception followed by the application of
control measures is one that has been repeated,
especially during the last fifty years (Figure 11.1).
Over this period, increases in public awareness of
pollution, in the ability to develop remedial
measures and in the political will to implement
strategies to control water contamination have to
a certain extent paralleled the rapid emergence of
a succession of water quality problems.
A conceptual model of water pollution
occurrence and control has been proposed by
Meybeck
et al
. (1989) using the example of the
history of domestic sewage contamination in
Western Europe over the last two centuries (Box
11.1). This model can also be applied to other types
of pollution and to countries that have different
INTRODUCTION
Water in every phase of the hydrological cycle,
from precipitation through terrestrial surface and
groundwater systems to the marine environment,
has a quality dimension that can be described by
reference to numerous physical, chemical and
biological properties, and is controlled by a myriad
of natural factors and human influences. Water
quality is of fundamental importance in the
provision of potable supplies to sustain human life
and in the health of aquatic ecosystems. It also
significantly affects a wide range of human uses of
water in industry, agriculture, transport and
recreation. At the same time, these uses and other
human activities, directly or indirectly, provide
manifold sources of water contamination. Where
the consequences or side-effects of human
scientific, industrial and social habits result in
conditions within the water environment that are
harmful or unpleasant to life, the term 'water
pollution' is used (Sweeting 1994). Acute water
quality problems, however, may also arise from
natural climatic or geological conditions.
Problems of freshwater pollution, on which the
present chapter focuses, have a long history and
have changed in character as world population has
grown and human technological capability has
increased and become more complex. Local
contamination of the aquatic environment has
been recognised for at least two millennia, and in
some countries legal means were taken to prevent
water pollution as early as medieval times. In the
UK, for example, laws were passed in the
