20 Years of Marine Water Quality Monitoring in Hong Kong

| Director's Message | Introduction | Background of the EPD’s river water quality monitoring programme | The scientific basis of the EPD’s river water quality monitoring programme | River water sampling procedures: testing, analysis, and publication of results | Eastern New Territories | Northwestern New Territories | Lantau Island | Southwestern New Territories & Kowloon | Summary | Appendices | Acknowledgements | Disclaimer |

River water sampling procedures: testing, analysis, and publication of results


[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



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