|
Beach
Water Quality Report 2002
Chapter Two
Beach
Water Quality Monitoring
|
|
|
|
|
| |
| 2.3 |
 |
| One
of the non-gazetted beaches
monitored by the EPD - Lung
Kwu Lower Beach |
Hong Kong has many non-gazetted
beaches. Among them, the EPD
monitors nine selected ones
(Figure 2.1). They are monitored
because of their popularity
(e.g. Discovery Bay Beach) or
their potential to be gazetted
in the longer term (e.g. Lung
Mei Beach). Monitoring results
of these nine beaches are shown
in Appendix 2.
|
| |
|
|
| Water
Quality Objective |
| |
|
| 2.4 |
To
safeguard the health of bathers,
the Water Quality Objective (WQO)
for bathing water has been established
under the Water Pollution Control
Ordinance in 1992. The WQO is
established on the basis of the
results of the local epidemiological
studies conducted in the late
1980s by the EPD and local academics.
The relationships between the
level of faecal indicators in
water and the swimming-associated
illness rates were established
in these studies. The faecal indicator,
E. coli, had been found to
have the best correlation with
the swimming-associated illness
rates and is the best faecal indicator
to estimate the health risk of
swimming at beaches of Hong Kong. |
| |
| 2.5 |
The
WQO states that the level of E.
coli should not exceed 180
per 100mL calculated as the geometric
mean of all samples collected
during the bathing season from
March to end October. Samples
should be taken at least three
times a month at intervals of
between 3 and 14 days. This WQO
applies to the bathing beach subzones
of all Water Control Zones in
Hong Kong. |
| |
|
|
Functions of the programme
|
2.6
|
Besides assessment of
compliance with the WQO,
the beach monitoring programme
has been designed to achieve
the following functions:
- To detect any change
in beach water quality:
Monitoring results can
provide early warning
of beach water pollution
so that any potential
pollution problem can
be resolved more easily
at an early stage.
- To identify polluted
beaches that need remedial
actions: Based on
the monitoring results,
the Authority can identify
polluted beaches and
set priorities to take
remedial actions to
improve the beach water
quality.
|
|
 |
| Counting
of E.coli colonies |
|
| |
|
|
 |
- To evaluate pollution
abatement programmes:
Monitoring provides
the information needed
to determine the efficacy
of beach-related improvement
measures such as provision
of sewerage or enforcement
of relevant legislation.
- To decide on the
opening of beaches:
Monitoring provides
the information on water
quality trends so that
LCSD can decide on the
opening of beaches.
- To advise the public
on the beach water quality
status:
Based on the monitoring
results, the public
will be able to make
an informed decision
on whether to swim at
a particular beach.
|
| E.coli
colonies(greenish blue colonies) |
| |
|
|
Sampling
protocol |
| |
| 2.7 |
| |
 |
| |
Some
physical parameters were
measured on site with portable
analyzer |
| |
 |
| |
Beach
water sampling |
In order to fulfil
these functions, the water quality
of all gazetted beaches is monitored
by the EPD at least once per
week during the bathing season
and at least once per month
during the non-bathing season
(Table 2.1). Those gazetted
beaches that are opened during
winter months are still monitored
weekly. Water samples are collected
on random days including weekends
and public holidays so that
non-biased information on water
quality is collected.
|
| |
|
| |
Table
2.1 Beach monitoring fequencies |
| |
 |
| |
* Deep Water
Bay, Golden, Clear Water Bay
Second and Silverstrand Beaches
|
| 2.8 |
Water
samples are collected from each
beach at thigh to waist water
depth for E. coli analysis
and measurement of pH, salinity
and turbidity. Water temperature
and the dissolved oxygen content
are measured on site using portable
analyzer. Weather information
and on site observations are also
recorded. In addition to sampling
within the bathing area, samples
are also collected from streams
and storm drains in the vicinity
to monitor their impact on beach
water quality, if any. The operational
procedures of the monitoring programme
are depicted in Figure 2.2. |
| |
|
| |
 |
| |
Beach Rating Systems
|
 |
|
|
Figure
2.3 Relationship
between E. coli count
in beach water and swimming-associated
illness rate |
|
|
| 2.9 |
The E. coli levels of
water samples collected within
the bathing area are used for
rating a beach according to
our beach grading and ranking
systems. The grade of a beach
indicates the latest water quality
of the beach while the rank
of a beach denotes its average
water quality through the whole
bathing season. Both systems
are health risk related and
beaches are classified into
four categories according to
their E. coli levels.
|
Annual Ranking System |
| 2.10 |
The
rank of a beach reflects its long-term
water quality. It is determined
by calculating the geometric mean
E. coli level of all samples
collected within the bathing area
during the bathing season from
March to October. The annual ranking
system is summarized in Table
2.2. The four annual ranks correspond
to the respective swimming-associated
illness rates established in the
epidemiological studies (Figure
2.3). Both 'Good'and 'Fair' ranks
meet the WQO for bathing water.
|
| |
|
| |
Table
2.2 Annual ranking system |
 |
| |
* |
Geometric
mean E. coli count
calculated based on all
data collected during the
bathing season. |
| |
** |
Skin
and gastrointestinal illnesses |
| |
UD |
Undetectable |
|
| |
| Beach
Grading System |
| |
|
| 2.11 |
The grading system
is summarized in Table 2.3. Only
opened beaches are graded to inform
the public of its latest water
quality status. A beach grade
is calculated on the basis of
the geometric mean E. coli
level of the 5 most recent sampling
occasions. To further safeguard
bathers' health, the worst grade,
i.e. Grade 4, is also given to
a beach when a high E. coli
level exceeding 1600 per 100mL
is detected on the last sampling
occasion, regardless of the geometric
mean. Hence the grade of a beach
reflects the short-term water
quality in the past few weeks,
and provides the information on
recent deterioration of water
quality. |
| |
|
| |
Table
2.3 Beach grading system |
 |
| |
* |
Except
otherwise indicated, the
E coli level is the
geometric mean of the 5
most recent sampling occasions. |
| |
** |
Skin
and gastrointestinal illnesses |
| |
UD |
Undetectable |
|
| |
|
| Dissemination
of beach information |
|
| |
|
|
| 2.12 |
 |
| Bathers
could check the beach grades
at the notice boards before
entering the water
|
In order to provide the public
with the most updated information
on beach water quality, the beach
grades are disseminated through
various channels. A summary of
beach grades is released through
the press media before weekend
so as to facilitate the weekend
beach goers to decide on where
to swim. During the week, beach
grades are also updated on the
beach water quality webpage at
EPD's website (http://www.epd.gov.hk)
and at the grading notice boards
of the beach offices whenever
new information is available.
The public can also access such
updated information through the
beach water quality hotline (2511
6666). |
| |
|
| 2.13 |
Bathers
could check the beach grades at
the notice boards of the beach
offices before deciding to enter
the water. Nevertheless, as the
water quality may fluctuate after
heavy rain and may be worse than
the grades suggest, rainfall warning
signs have been erected at those
beaches particularly susceptible
to the effect of rain to alert
bathers of the possible transient
deterioration in water quality
(Appendix 3). |
| |
|