Overview
[Photo of Physical chemical properties of river water being measured]
With the general scientific background having
been described in Chapter 2, this chapter will take a closer look at
the scope and logistics of the EPD’s monitoring programme, and the
actual sampling and laboratory procedures that are carried out.
Overall, the EPD has monitoring stations
covering 30 rivers across Hong Kong. Hong Kong has hundreds of
watercourses and streamlets, but these 30 rivers include all the
major rivers in the territory, along with a number of others
selected because they were seriously polluted during the 1980s and
were in urgent need of remedial attention.
In 1986, the EPD began its river water
quality monitoring programme by setting up 47 monitoring stations at
just 14 rivers. Over the ensuing years, it has extended its coverage
by adding new rivers and setting up further monitoring stations. By
1993, it was looking after 86 monitoring stations in 33 rivers.
Since 1993, the number of rivers monitored
has dropped by three to 30, and the number of monitoring stations by
four to 82. Stanley Stream, the only watercourse being monitored on
Hong Kong Island, was largely converted into an underground box
culvert in 1997 and so the EPD’s two monitoring stations there were
closed down. Similarly, two streams in the northwest of Hong Kong
became inaccessible in the late 1990s due to development of the West
New Territories Strategic Landfill: the monitoring station at the
Tseng Tsui Stream ceased being used in 1997, and that at the Nim Wan
Stream in 1999. The data from these three streams and four
monitoring stations has not been included in the information
presented in this report.
A few other watercourses have had their
monitoring interrupted at various points in their history. The KT1
monitoring station on the Kam Tin River was suspended temporarily in
1997 and 1998 while river training work was being carried out in the
vicinity, resuming in 1999 once the station again became accessible.
The Tsang Kok Stream in the northwest was also affected by the West
New Territories Landfill development, being suspended in 1999 but
resuming from 2000.
[Photo of Map of rivers monitored by the EPD in 2005, showing positions of monitoring stations]
Most of the monitoring stations across Hong
Kong are visited monthly. On each visit EPD personnel take with them
samplers (used for collecting water samples), and bottles in which
to store the samples. Each of the bottles is labelled with a unique
barcode to make for easy identification and tracking. Some safety
gear is also included to avoid mishaps on steep, slippery slopes or
in adverse weather conditions. Certain pieces of key technical
equipment are also essential: a multiparameter water quality
measuring probe, data logger, and flow meter, which allow detailed
on-site measurements to be taken; and a pocket PC for easily
recording on-site observations.
On arriving at the monitoring station, EPD
staff check if their equipment is working properly and then proceed
to make a range of field observations and take water samples. Once
collected, the samples are placed in the labelled bottles and stored
in a refrigerated box for transport back to the laboratory. On-site
measurements of parameters such as temperature, pH, turbidity and
dissolved oxygen are made using the multiparameter water quality
measuring probe, and recorded in the data logger. The readings
obtained are then compared against the normal ranges from that
station, and any unusual readings result in a second set of
measurements being made to check the validity of the initial
reading. These data and other field observations are recorded in a
pocket PC for downloading back at the EPD offices. Should their
on-site measurements or observations indicate that a pollution
incident has occurred, staff immediately refer the situation in the
field to the appropriate EPD Regional Office for follow-up action.
[Photo of Faecal bacteria being analysed in the EPD’s Microbiology Laboratory ]
Back at EPD offices, the collected samples are
distributed for further processing. A proportion of the samples are
sent to the EPD’s Environmental Microbiology Laboratory where they
receive same-day analyses for E. coli, faecal coliforms, and 5-day
biochemical oxygen demand. The remainder of the samples are stored in
a cold room before being delivered to the Government Laboratory, where
they are analysed according to the 39 other parameters outlined in
Chapter 2. All laboratory analysis is carried out to international
standards using advanced methods.
Meanwhile, the field information collected
on-site is downloaded, checked, and entered into the EPD’s monitoring
database. This database is specially designed to make for efficient
data storage, management and analysis, and the easy generation of a
wide range of charts and graphs. The results of the laboratory
analyses are also added into this database.
Telemetric monitoring
[Photo of Inside the telemetric monitoring base station]
All the EPD’s river water quality monitoring
operations are carried out by individuals, who visit the monitoring
stations, take samples and record data. To explore the possibility of
obtaining monitoring data automatically and on a continuous basis,
between 1996 and 2000 the EPD carried out a trial of telemetric
monitoring in the Shing Mun River.
The trial involved setting up a base station in
the lower reaches of the Shing Mun River, into which river water was
pumped continuously. The telemetric monitor measured and logged six
physical water quality parameters at short intervals, and then
transmitted this data to the EPD offices via a phone line
The trial revealed a number of problems.
Instruments and probes became easily fouled by biological growth and
had to be cleaned or replaced frequently; equipment exposed to the
sometimes harsh field conditions tended to break down easily; the
transmission of data from the base station was unreliable given the
technology then available; the probes could only measure a limited
number of parameters; and vandalism of field equipment was another
potential problem. The EPD eventually decided that telemetric
monitoring had too many constraints and was too resource-demanding to
be included as part of its long-term monitoring programme.
Publication of reports and data
The information stored in the EPD database is a vital resource for
providing the public with an accurate picture of the state of Hong
Kong’s rivers, and helping policymakers and the public evaluate the
effectiveness of water improvement measures. In addition, academics
and environmental consultants use the data for scientific research and
for assessing the environmental impact of various infrastructure
developments.
To make this information as widely available
as possible, since 1988 the EPD has published annual reports providing
summaries and analyses of the river water quality data it has collected.
Between 1988 and 2001, these reports were produced in hard copy
and copies were distributed to EPD resource centres, public and
university libraries, as well as being put on sale to the public.
From 1998 the EPD also began producing the reports as electronic
files, made available on the department’s website for a wider
audience, and eventually (in 2002) ceased production of the hard
copy versions as a ‘green’ measure to reduce use of paper.
Reports from 1998 and onwards can be downloaded from http://www.epd.gov.hk/epd/english/environmentinhk/water/river_quality/
rwq_report.html. In addition, detailed annual monitoring
data is available for free download from http://epic.epd.gov.hk/ca/uid/riverhistorical/p/1.
Besides keeping the annual reports on its website,
the EPD also uploads monthly water quality data from 12 major river
monitoring stations. This information tracks the levels of dissolved
oxygen and E. coli at the stations, and is especially useful for
those who need to know about water quality at a particular time
of year, as for example those taking part in dragonboat races on
the Shing Mun River in Sha Tin. This information is available at http://epic.epd.gov.hk/ca/uid/riverrecent/p/1