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 About
Water
Quality
In the UK DEFRA (the Department
for Environment, Food and Rural Affairs) is responsible for all
aspects of water policy, including water supply and resources.
These include:
The
Environment Agency (EA) monitor the water quality at over 7,000
inland sites, representing about 40,000km of rivers and canals and
2,800km of estuaries in England and Wales.
Statistical
methods are used in the General Quality Assessment (GQA)
scheme for rivers and for the classification of estuaries, taking
in:
-
Chemical quality
of rivers - dissolved oxygen, oxygen demand and
ammonia.
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Biological
quality of rivers - using macro-invertebrates.
-
Nutrient
status of rivers - phosphate and nitrate.
-
Aesthetic
quality of rivers - litter, foam, odour and
colour.
-
Estuary
quality - biological, chemical and aesthetic quality.
The quality of bathing waters in
England and Wales is monitored against standards laid down in the
bathing water regulations (SI 1991/1597), which come from the EC
Bathing Water Directive (76/160/EEC).
 Compliance with the EC Bathing
Water Directive standards is assessed annually by DEFRA on
the basis of information supplied by the the EA. The Bathing Water Directive sets out two levels of
standards, those that must be complied with - Mandatory (or
Imperative) standards - and the more stringent Guideline standards
that Member States should strive to achieve. The Government has
set the Environment Agency a Public Service Agreement (PSA)
target of 97% Mandatory compliance and 85% Guideline
compliance by 2005.
The
EA monitors the quality of 473 designated coastal and
nine inland (lakes and rivers) bathing waters throughout England
and Wales (figures for 2000). The bathing season is taken to
be from 15 May to 30 September. Water sampling begins two
weeks before the start of the season (i.e. 01 May) and 20 samples are taken
(essentially one a week) throughout the season. All sampling
is undertaken at pre-determined points on the beach, where the
daily average density of bathers has been considered to be at its
highest. Water samples are taken at a depth of approx. 30cm
below the surface; additional surface samples may be taken to test
for the presence of mineral oils.
Each sample is tested for total
coliform bacteria and for faecal coliform bacteria. Faecal
coliform bacteria are an indicator of the presence of traces of
human sewage.
Analysis of bathing waters are
also made on the basis of other standards in the EC Directive. Two
samples are analysed for the presence of enteroviruses, and two
for the presence of salmonellae, at any site which had failed the
mandatory coliform standards in the previous year.
Because the quality on a number
of bathing waters is on the borderline between compliance and
non-compliance, there is always a statistical risk that some of
them will 'pass' in one year and 'fail' in another even though
their actual quality has not significantly changed. Real
changes in quality can also occur from year to year simply as a
result of differences in the weather.
The results of the various
bathing water analyses are used to assist in giving
"awards" to bathing beaches, such as the Blue Flag.
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