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| Ranking and Grading Hong Kong's Beaches |
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[Photo of Publicity leaflets on the beach ranking
and grading systems]
The EPD uses two separate systems to help beach
users get a wider picture about beach water quality. The first is
the annual ranking system, which is designed to give a
general summary of the water quality at every beach across the bathing
season, from March to October. Beaches were ranked using an annual
ranking system when the EPD first took over the monitoring programme
in 1986. On the other hand, the grading system, which came
into operation in 1987, is designed to present recent, short-term
information about beach water quality, based on sampling over the
past few weeks. Both systems have undergone changes and improvements
over the years and gradually developed into the forms that are used
today. |
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The annual beach ranking system |
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Each year, the EPD sorts Hong
Kong's beaches into rankings to reflect the overall quality of beach
water across the bathing season (March to October). The most important
distinction is whether or not individual beaches met the WQO. The
key figure here is 180 per 100 mL, the upper limit for E. coli bacteria
in 100 mL of sea water. Beaches whose geometric mean across the
swimming season is more than 180 do not meet the WQO. |
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Those beaches that do meet the
WQO (and most of Hong Kong's beaches are in this category) are then
further ranked to reflect the quality of their beach water. The
best beaches are ranked as 'Good', while those beaches with a higher
geometric mean are ranked 'Fair'. In the same way, beaches that
have not met the WQO are also further categorized into two rankings:
'Poor' and 'Very Poor'. This fourfold ranking system is designed
to help beach users know which beaches have consistently high or
low water quality. It also provides the public and the Government
with helpful information on trends of improvement or deterioration
over the longer term. |
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| Hong Kong's annual beach ranking system |
Rank |
E.
coli count per 100 mL* |
Minor
illness rate**
(Cases per 1,000 swimmers) |
WQO
Compliance |
Good |
<=24 |
Undetectable |
Compliant |
Fair |
25-180 |
<=10 |
Poor |
181-610 |
11-15 |
Non-compliant |
Very
Poor |
>610 |
>15 |
* Geometric
mean E. coli count calculated based
on all data collected between March and October.
** Skin and gastrointestinal illnesses |
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The beach ranking system has
been developed into its current form over time. In the early days,
beaches were ranked into four categories: 'Good', 'Acceptable',
'Marginally acceptable', and 'Unacceptable', based on their percentage
of compliance with the Hong Kong water quality standards of the
day. Once the EPD's own studies were completed in the late 1980s,
however, the system was revised and linked to health risks. This
involved a change in the category labels, which between 1990 and
1992 evolved into those used today. |
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The beach grading system |
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The beach grading system was
designed to complement the beach annual ranking system, and give
beach users up-to-date information about the water quality of Hong
Kong's beaches at any given time of the year. The beach grading
score for any individual beach is worked out by taking the geometric
mean E. coli levels of the five most recent samples taken from that
beach. Because most gazetted beaches are sampled three times per
month or more, a beach grading score provides a good snapshot of
beach water quality over the current month. |
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When the beach grading system
was first introduced in July 1987, it divided beaches into three
categories: 'A' (Good), 'B' (Acceptable) and 'C' (Poor). The early
criteria for grading were based on 1977 WHO criteria which, as mentioned
earlier, were not based on epidemiological studies and were not
specifically linked with health risks to swimmers. Following the
EPD's own studies in the late 1980s and its development of health-risk
based water quality objectives, a revised four-tier grading system
was introduced in 1990, numbered from 1 to 4 and labelled 'Good',
'Fair', 'Acceptable', and 'Poor'. |
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In 1992, the classification
system was further refined into what is the current system. On the
basis of their scores, beaches now fall into one of four grades:
Grade 1 (Good), Grade 2 (Fair), Grade 3 (Poor), and Grade 4 (Very
Poor). These labels should not be confused with those of the beach
annual ranking system, which measures water quality across an entire
season. For example, a beach may have some periods when it is graded
'Good', while still being ranked 'Fair' for the bathing
season as a whole. |
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A further significant change
was made in 1999. Since then, whenever a single beach water sample
shows an E. coli level exceeding 1,600 per 100 mL, this reading
overrides the geometric mean figure for the beach and instead triggers
an immediate Grade 4 rating. Sudden high levels of E. coli indicate
a potential health risk, and this system is designed to make sure
they are not disguised by a low geometric mean. Such a level probably
suggests a period of exceptionally heavy rainfall or an isolated
pollution incident, for which immediate action needs to be taken. |
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| Hong Kong's beach grading system |
Grade |
Beach
water quality |
E.
coli count per 100 mL* |
Minor
illness rate **
(Cases per 1,000 swimmers) |
1 |
Good |
<=24 |
Undetectable
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2 |
Fair |
25-180 |
<=10 |
3 |
Poor |
181-610 |
11-15 |
4 |
Very Poor |
>610
or last reading >1,600 |
>15 |
* Unless otherwise indicated, the
E. coli count represents the geometric mean
of the 5 most recent sampling occasions.
** Skin and gastrointestinal illnesses |
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