Geography Reference
In-Depth Information
In consequence, the sequence of pollution problems
is emerging over decades rather than centuries. In
many countries of Eastern Europe, industrialisation
and agricultural intensification have proceeded at a
similar pace to that of Western Europe, but
pollution has risen to the level of severe damage
because environmental regulation has been slow or
lacking. Water pollution and control is affected not
only by conditions within a particular country but
also by factors operating at an international scale,
such as the effects of long-range transfer of
pollutants in the atmosphere, climate change and
nuclear accidents (Peters
et al
. 1998).
It is increasingly being recognised that issues of
water quality and pollution are as critical as issues
of water scarcity, although freshwater vulnerability
may be most severe when problems of water
contamination are combined with water shortage.
Reference has been made recently to an emerging
global crisis of water quality. The dimensions of
this crisis include the death of five million people
annually from waterborne diseases, the loss of
biodiversity and the occurrence of ecosystem
dysfunction, the contamination of freshwater and
marine ecosystems from land-based activities, the
pollution of groundwater resources, and global
contamination by persistent organic pollutants
(Ongley 1996). Many experts now believe that
freshwater quality will become the principal
limiting factor for sustainable development in
many countries early in the twenty-first century
(Ongley 1999), and already in China the aggregate
cost of water pollution to the national economy
has been estimated as 0.5 per cent of GDP (Smil
1996).
Webb 1986; Meybeck 1996), and natural
ecological and climatic conditions may give rise
to contamination by parasites, salts and metals,
especially in groundwater reservoirs. A greater
number of water quality issues, however, are
related to human activities, which may cause
freshwater pollution at varying spatial scales from
local (less than 10
4
km
2
) and regional (10
5
- 10
6
km
2
) to global (10
7
-10
8
km
2
). The severity of
pollution is usually inversely related to the size of
the water body impacted. Temporal scale is also
significant in water quality issues, because the time
it takes for freshwater to become polluted and the
period required for remediation of the
contamination varies according to the source of
the problem and the hydrological environment
affected (see Table 11.1). Thus, accidental chemical
spillage into a river will have an almost
instantaneous effect, but the transit time of the
pollutant from headwaters to the mouth of the
system, even in major rivers, will be of the order
of weeks or months, and the system will recover
rapidly. In contrast, it may take several decades for
fertiliser pollutants to migrate from the soil profile
to an underlying aquifer (Burt and Trudgill 1993),
while retention or absorption of the pollutant by
soils and bedrock may make the clean-up period
more protracted than the contamination phase.
A number of major sources of freshwater
pollution can be identified.
Organic pollution
Domestic sewage is one of the most significant and
widespread sources of organic matter added to
freshwaters by human activity, and it causes
pollution at local, regional and continental scales
(UNEP/WHO 1988). It has been estimated that
for major European rivers, such as the Rhine,
growth in human population since pre-industrial
times has been associated with a three-fold
increase in the organic carbon burden (Zobrist
and Stumm 1981). Today, domestic sewage remains
a major cause of river pollution in developed
countries (Sweeting 1994), while lack of sanitation
and inadequate waste management amplify this
problem for a large percentage of the world's
THE NATURE OF WATER QUALITY
PROBLEMS
Table 11.1 summarises major issues of freshwater
quality and highlights the great diversity of
pollution problems that currently affect the surface
and groundwaters of the Earth. Water quality
varies naturally in space and time in response to
climatic, geological, pedogenic, biotic and
hydrological factors (e.g. Walling 1980; Walling and
