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 |


[Photo of Boating activities on the Shing Mun River]

Although Hong Kong is relatively small in land area, its steep terrain and high summer rainfall mean it boasts hundreds of streams, rivers and open storm channels or nullahs right across the territory. Since Hong Kong is largely surrounded by sea, none of these watercourses are very long, but they perform a vital role in draining rainfall off the slopes and efficiently channeling water into the ocean.


Streams and rivers are used for many different purposes by Hong Kong’s inhabitants. Many of the territory’s watercourses are situated in water catchment areas, and flow directly into reservoirs to provide drinking water for the city. Other rivers are tapped for irrigation, particularly in those parts of the New Territories where farming is still carried out. Thousands of urban Hong Kongers enjoy the peace and serenity that comes from walking beside rivers, and even boating on some of the larger of them. Last, but certainly not least, Hong Kong’s streams and rivers are also the home to a wide variety of fish, insects, and other water life.



Key characteristics of Hong Kong rivers

Hong Kong’s rivers tend to share various characteristics which help explain how they have been used over time and also why certain problems have developed. They are all short, with relatively small flows. The volumes of water they carry can vary quite widely depending on the season, given Hong Kong’s sometimes torrential summer rainstorms and its relatively dry winter months. None however are long enough to develop into the large, deep, slow-moving rivers found in many bigger places. In addition, the upstream areas of Hong Kong rivers tend to have been drawn on quite extensively for supplies of drinking water, a practice that over time has further reduced downstream river flows. When a river’s flow is reduced, so are its flushing and self-cleansing abilities, meaning that it becomes easier for contamination or pollution to build up.


This reduction of flow due to upstream water use represents just one of a number of key factors that have affected Hong Kong’s rivers over time. Another is the fact that rivers have for a long time been used as dumping grounds for waste generated by a range of human activities, including domestic sewage, livestock waste, industrial waste, and other types of effluent. This was especially the case before 1980, when no effective water pollution legislation or controls were in place.


[Photo of Measuring the flow rate of a river]

This report looks at the results of monitoring the water quality of a number of key Hong Kong rivers over the past twenty years, and discusses the work of the Government and the Environmental Protection Department (EPD) in improving their water quality. Before exploring this history, however, it will be useful to lay out some basic geography of Hong Kong that helps explain the different kinds of rivers in the territory, and the specific problems that have affected different parts of Hong Kong.


Geographically, Hong Kong’s rivers fall into four main areas: those of the Eastern New Territories, the Northwestern New Territories, Lantau Island, and the Southwestern New Territories & Kowloon. The rivers in each of these four areas tend to share a number of geographical and historical features. In this report, information about Hong Kong’s rivers will be divided into four chapters corresponding with these geographical divisions.


However, this report also frequently makes mention of ‘Water Control Zones’ for different areas of Hong Kong. Following the enactment of the Water Pollution Control Ordinance in 1980, the Government began gradually appointing ten Water Control Zones (WCZs), along with a few Supplementary WCZs, as a way of focusing its work of controlling water pollution. For the purposes of monitoring and assessment, Hong Kong’s rivers can also be grouped according to WCZ. The Water Control Zones are discussed in more detail in the next chapter, where a map of the WCZs within the four geographical areas used in this report can also be found.



Eastern New Territories

Within the Eastern New Territories, the EPD monitors a total of ten rivers, situated within three different Water Control Zones. Within the Tolo Harbour WCZ the most important is the Shing Mun River in Sha Tin, but five other rivers in the Tai Po District are also monitored. Also monitored are three watercourses in Sai Kung (Port Shelter WCZ), and one near Tseung Kwan O (Junk Bay WCZ).

[Photo of Ho Chung River in the 1980s]

[Photo of Ho Chung River today]


During the 1980s most of these rivers suffered pollution from a number of sources, but since improvement measures were set in motion their water quality has improved significantly. A twenty-year comparison tells the story: in 1986, water at nearly a quarter (24%) of the Eastern New Territories monitoring stations was graded either ‘Bad’ or ‘Very Bad’, but in 2005 not a single monitoring station received either of these gradings. More information about these gradings can be found in Chapter 2, and detailed information about the rivers in the Eastern New Territories area in Chapter 4.



Northwestern New Territories

In the Northwestern New Territories, the EPD currently monitors 13 rivers, all situated within the Deep Bay Water Control Zone. They include the three main rivers of North District, four major rivers around Yuen Long, and six smaller streams in the vicinity of Lau Fau Shan.

[Photo of River Indus in the 1980s]

[Photo of River Indus today]


These rivers all suffered greatly in the 1980s from being surrounded by large numbers of livestock farms, situated in some of the flattest countryside of rural Hong Kong. Discharges from numerous unsewered villages scattered across the plains exacerbated the problem. Significant improvements have occurred since the 1980s, but the public sewer network still does not extend to much of this area. The number of livestock farms has been hugely reduced since the late 1980s, but those that remain still contribute substantially to river water pollution.


‘Bad’ to ‘Very Bad’ gradings were recorded for every monitoring station in this area in 1986, and the overall WQO compliance rate was just 21%. By 2005, the percentage of monitoring stations graded ‘Bad’ or ‘Very Bad’ had fallen to 42%, and WQO compliance had risen to 69%. Further information on the gradings and WQO compliance figures can be found in Chapter 2, and detailed information on the rivers of the Northwestern New Territories in Chapter 5.



Lantau Island

On Lantau Island two rivers are monitored, Mui Wo River in the Southern Water Control Zone and Tung Chung River in the North Western Water Control Zone. The rivers are relatively remote and Lantau itself has had a low population base, so pollution has been limited. However, livestock has long been kept in the Mui Wo hinterland, creating some pollution problems for that river and silver Mine Bay Beach.

[Photo of Mui Wo River in the 1980s]

[Photo of Mui Wo River today]


In 1986, all the monitoring stations on Lantau recorded gradings of ‘Fair’, and WQO compliance stood at 72%. By 2005, all monitoring stations were graded either ‘Good’ or ‘Excellent’, and WQO compliance had risen to over 99%. Further information on the gradings and WQO compliance figures can be found in Chapter 2, and detailed information about the rivers on Lantau in Chapter 6.



Southwestern New Territories & Kowloon

The Southwestern New Territories & Kowloon area runs from Tuen Mun in the west to Lei Yue Mun at the eastern end of Victoria Harbour. Within this area, the EPD monitors four rivers and the Kai Tak Nullah. The Tuen Mun River is in the North Western Water Control Zone, while Kai Tak Nullah and two minor streams are situated in the Victoria Harbour Water Control Zone, and another minor stream near Sham Tseng is in the Western Buffer Water Control Zone.

[Photo of Tuen Mun River in the 1980s]

[Photo of Tuen Mun River today]


The pollution suffered by these rivers in the 1980s varied according to their location, and included livestock, sewage and industrial pollution. Again, significant improvements have been achieved over the past two decades. From a total of 80% of monitoring stations where water was graded ‘Bad’ or ‘Very Bad’ in 1986, in 2005 just 6% of stations received these gradings. The WQO compliance rate nearly doubled too, from 49% in 1986 to 88% in 2005. Further information on the gradings and WQO compliance figures can be found in Chapter 2, and detailed information about the rivers of the Southwestern New Territories and Kowloon area in Chapter 7.


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