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 |

Northwestern New Territories

Rivers monitored

The Northwestern New Territories includes a total of 13 monitored rivers that flow either into the Shenzhen River or directly into Deep Bay. All 13 rivers are part of the Deep Bay Water Control Zone. Three of these—the Rivers Indus, Beas and Ganges—are major rivers situated in North District. Four of them, namely the Yuen Long Creek, Kam Tin River, Tin Shui Wai Nullah and Fairview Park Nullah, are major rivers around Yuen Long. The other six watercourses in this area are minor streams in the vicinity of Lau Fau Shan.

[Photo of Map of rivers monitored in the Northwestern New Territories, showing their Water Quality Index gradings in 2005]


General survey

Apart from the recently developed towns of Sheung Shui, Fan Ling, Yuen Long and Tin Shui Wai, most of the Northwestern New Territories is rural and unsewered. This area contains some of the flattest and most fertile land in Hong Kong, and so has historically been used for farming, pond fishing and the raising of livestock. Some of the major rivers run through flood plains and there is a history of flooding problems in the area, especially in the summer rainy season. As part of the Government’s flood prevention measures over the past decade, many of the rivers have been straightened, widened, deepened, and channellised, and these alterations have changed their characteristics considerably.

[Photo of The Kam Tin River was originally a natural watercourse]

[Photo of The Kam Tin River was channellised after river training in the mid 1990s]

The major pollution sources in the 1980s were agricultural waste and runoff or discharge from unsewered domestic, commercial and industrial premises. This area of Hong Kong was particularly badly affected due to the high concentration of livestock farms it contained. These pollution sources had a devastating effect on water quality and the health of the rivers, such that in 1986 WQO compliance for the area barely registered at 21%, and the nine river stations monitored in that year all had WQI grades of ‘Very Bad’. Subsequently, a number of measures to improve water quality were initiated in the 1980s.

[Photo of Compliance with the Water Quality Objectives in the major rivers of North District and Yuen Long in the 1980s and in 2005]

[Photo of Compliance with the Water Quality Objectives in the minor streams of Lau Fau Shan in the 1980s and in 2005]


The rivers of the Northwestern New Territories benefited greatly from the introduction of the Livestock Waste Control Scheme in June 1988, which banned livestock farming in new towns and urban areas and required livestock farms outside those areas to treat their waste to a certain standard before discharge. The provision of an ex-gratia allowance for farmers who ceased farming activities helped reduce the number of livestock farms in the area significantly, while a free waste collection service brought down the pollution load from those that remained. From 1988 and into the 1990s, major improvements in water quality were recorded.


The declaration of the Deep Bay Water Control Zone on 1 December 1990 also allowed the EPD to begin enforcing the Water Pollution Control Ordinance for the area. It mounted a campaign for industrial and commercial premises and unsewered villages to treat the waste water they generated.

[Photo of Water Quality Index gradings for rivers in the Northwestern New Territories, 1986 and 2005]


Despite the work done over the past two decades to improve river water quality in this area, there remains room for further improvement. The six minor streams have been transformed, with WQO compliance from 93% to 100% in 2005, and WQI grades of 83% ‘Excellent’ and 17% ‘Good’. The seven major rivers, however, have been slower to improve. WQO compliance in 2005 was still only between 37% and 85% which, though it marks an improvement over the 1980s, falls short of what is needed. The WQI was graded ‘Bad’ or ‘Very Bad’ for 56% of the monitoring stations in 2005.


One of the reasons for the persistence of pollution in these rivers is that hundreds of livestock farms still remain across this area, and there are also more than 100 unsewered villages housing large populations. It should be borne in mind too that improvements in this area are relative. Although there have been significant leaps forward, the fact is that all these rivers were extremely polluted in the 1980s, some of them with greater than 100 mg/L BOD5 and 10,000,000 cfu/100 mL E. coli (comparable to raw sewage!). That means that even where more than 90% of the pollution load has been removed, what remains is still high compared with rivers in other parts of Hong Kong.


Most parts of the Northwestern New Territories remain Livestock Waste Control Areas, meaning that livestock farming is still allowed. At the end of 2005 there remained hundreds of such farms across the area, and the sheer numbers doubtless have contributed to poor river water quality. Although discharge standards have been imposed at these farms, pollution easily arises when large numbers of farms discharge their effluent into rivers or streams with relatively small flows. In addition, some farmers still illegally discharge their effluent into nearby rivers. Enforcement remains an uphill battle given the difficult terrain in the New Territories, the large number of farms, and the complex (and sometimes concealed) networks of drains that lead to the waterways. The EPD remains very active in tracking pollution and responding to pollution incidents in the area.


As mentioned earlier, most parts of the Northwestern New Territories do not yet have access to the public sewer, so most domestic sewage is treated only by septic tanks, which may not always function optimally. As the public sewerage network is extended across the area over the next decade, water quality should see further improvements.



Case study: The River Indus and the River Beas

The Rivers Indus and Beas provide good case studies that show both the advances that have been made since the 1980s, and the problems that remain to be overcome. The River Indus is one of the largest river systems in the New Territories, with a total catchment area (including that of the River Beas and other tributaries) of around 65 square kilometres. Its main stream flows westward through Man Uk Pin, Kwan Tei and Sheung Shui, until it joins the Shenzhen River at Lo Wu.


[Photo of The River Indus, with reinforced banks]

The River Beas, though a tributary of the River Indus, is also a major river in its own right. Its catchment area covers 15 square kilometers, and it flows northward from Lin Tong Mei through Hang Tau Tai Po and Kwu Tung to join the River Indus at Ho Sheung Heung.


In the 1980s, there were thousands of livestock farms scattered around the catchment areas of these two rivers. All six monitoring stations for the rivers were graded ‘Very Bad’, and overall WQO compliance for the River Indus was just 21%. The River Beas, meanwhile, was even worse with just a 19% WQO compliance rate.


Once the Livestock Waste Control Scheme was introduced in phases from 1988, however, the number of livestock farms in the region of the Rivers Indus and Beas dropped dramatically. The Scheme required farms in the River Indus catchment to comply with a set of effluent standards by 1997, and those in the River Beas catchment to meet the same standards by 1999. As a result, the majority of farmers opted to stop farming and instead receive Government compensation. By 2005, there remained just 12 licensed livestock farms in the River Indus catchment, and 18 in the River Beas catchment. All of these farms were required to provide treatment to their waste.


[Photo of Biochemical Oxygen Demand (BOD5) in the River Beas (RB3)]

Evidence of the improvements brought about by the control of livestock waste can be seen in the accompanying chart, which shows a significant reduction in BOD in the 1990s as recorded by one of the River Beas monitoring stations (RB3). By 2005, the River Indus had achieved 69% compliance with the WQO, and its two upstream stations were graded ‘Good’. The WQO compliance level of the River Beas, meanwhile, stood at 72% in 2005, with the station furthest upstream graded as ‘Good’.


Downstream, however, things still have some way to go. The station of the River Indus furthest downstream was graded ‘Bad’ in 2005, the two downstream stations of the River Beas only managed ‘Fair’ gradings, and E. coli levels remained high at 320,000 cfu / 100 mL. This indicates that livestock waste was not the only major problem facing the rivers. The other was, and remains, the thousands of unsewered village houses in the two catchments. Even those with septic tanks were often polluters, when the tanks were badly designed or poorly-maintained. Further improvements will be made when the Government extends its public sewers to these villages over the next decade, as provided for under the North District Sewerage Master Plan and its review.



Minor streams in Lau Fan Shan

[Photo of Tai Shui Hang Stream has maintained ‘Excellent’ water quality over the past decade ]

The EPD has monitored six minor streams in Lau Fau Shan since 1989. They are Ngau Hom Sha Stream, Sheung Pak Nai Stream, Pak Nai Stream, Tsang Kok Stream, Tai Shui Hang Stream and Ha Pak Nai Stream. The first four of these were polluted by livestock waste from farms in the area in the 1980s, and water quality was graded between ‘Fair’ and ‘Very Bad’ in the period. Following the implementation of the Livestock Waste Control Scheme, the streams improved significantly. In 2005, all six streams had WQI grades of either ‘Good’ or ‘Excellent’, and enjoyed WQO compliance of between 93% and 100%.



Other major rivers in North District and Yuen Long

The other major rivers in these areas are Yuen Long Creek, the Kam Tin River, the River Ganges, Tin Shui Wai Nullah and Fairview Park Nullah. All of them suffered similar problems to the Rivers Indus and Beas discussed in the ‘Case Study’ above. Yuen Long Creek and the Kam Tin River were the first to be monitored, in 1986, when their WQO compliance rates were assessed as 24% and 20% respectively. All six monitoring stations were graded ‘Very Bad’.


In 1987, the River Ganges began to be monitored, when its WQO compliance rate was recorded as 43%. Two of its three monitoring stations were graded ‘Very Bad’, although the third station, situated upstream of the numerous livestock farms, was graded ‘Excellent’.


[Photo of Tin Shui Wai Nullah, running alongside housing estates ]

Monitoring of Tin Shui Wai Nullah and Fairview Park Nullah followed in 1993. In that year, their WQO compliance rates were 63% and 27% respectively, while the WQI gradings at the individual monitoring stations ranged from ‘Fair’ to ‘Very Bad’.


These rivers have not shown such positive gains over the past two decades as those achieved by the Rivers Indus and Beas. The pollution load of the rivers has certainly been significantly reduced as a result of the Livestock Waste Control Scheme and implementation of WPCO controls after December 1990. However, large numbers of farms remain in the catchments of the River Ganges, Yuen Long Creek, the Kam Tin River and Tin Shui Wai Nullah. Unsewered village houses continue to add to the problem.


The Fairview Park Nullah was graded ‘Bad’ in 2005, mainly because its catchment area has been reduced after water from Ngau Tam Mei began to be diverted into the Kam Tin River in 2002. After the diversion, the nullah no longer received discharges from livestock farms, but the diversion did lead to significantly reduced flow, lowering the nullah’s ability to dilute or disperse pollutants.


For these five rivers, WQO compliance rates ranged from 37% to 85% in 2005. Overall, 75% of the monitoring stations were graded as ‘Bad’ or ‘Very Bad’. More than two thirds of the monitoring stations had E. coli levels of above 100,000 cfu / 100 mL. These figures are far from satisfactory, and work remains to be done in the area.


Future actions

Two major Government initiatives are expected to help improve river water quality in the Northwestern New Territories over the coming few years. One is the extension of the sewerage network under the Sewerage Master Plans drawn up for North District, Yuen Long and Kam Tin, which are being implemented in phases. Some of the existing sewerage facilities in the Northwestern New Territories are being upgraded, and public sewers will be provided for 72 unsewered villages in North District and 44 in Yuen Long and Kam Tin over the next decade. More details on the schedules for implementing the sewerage projects for the area can be found in the tables below.

[Photo of Schedule for implementing village sewerage projects under the North District Sewerage Master Plan and its Review]

[Photo of Schedule for implementing village sewerage projects under the Yuen Long & Kam Tin Sewerage Master Plan and its Review]

To reduce public health risks and improve environmental hygiene in the New Territories, the Government introduced the Voluntary Surrender of Poultry and Pig Farm Licence Schemes in 2005 and 2006 respectively. These provide incentives for livestock farmers to give up their farming licences, for which they will receive financial compensation. Poultry farms which join the scheme must close down their farming activities by February 2007, and pig farms by late 2007. River water quality in the area is expected to improve further as more livestock farms close down.



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