Hong Kong marine water

For a land area of just 1,104 km², Hong Kong has a phenomenal amount of coastline: 456 km is the length of the coastline running round the main area of Hong Kong from one side of the New Territories to the other, while the 263 islands in Hong Kong waters between them have another 722 km of coastline. In short, Hong Kong is swathed in and surrounded by the sea, and includes 1,651 km² of marine water within its boundaries for which it is directly responsible.


Hong Kong is on the southern coast of China within the South China Sea environ and at the eastern edge of the Pearl River estuary. Its western waters are affected by the large flows from the Pearl River, particularly in the summer rainy season. By contrast, the eastern waters are more strongly influenced by oceanic currents, specifically the Hainan Current in the summer (which flows from the south-west to the north-east) and the Kuroshio Current in the winter (which flows in the opposite direction). Tropical cyclones and strong monsoon winds also play a role in mixing of the water masses.


Within marine waters covering about 1700 km², Hong Kong enjoys a remarkable range of different marine environments. The deeper waters to the east of the territory (which average between 20 and 30 metres in depth) have high clarity and salinity (salt content), and are basically oceanic. By contrast, Deep Bay to the west has strong estuarine characteristics, meaning the water there is mixed with river flow, is low in salinity, typically shallow (averaging 4 to 10 metres in depth), silty and turbid.


Between these two areas is the natural deep-water Victoria Harbour, which goes down as far as 42 metres in places. Elsewhere, there are semi-enclosed bodies of water in Tolo Harbour, Port Shelter, Mirs Bay in the east and Deep Bay in the west, and a number of smaller sheltered areas enclosed by breakwaters which include typhoon shelters, boat anchorages and marinas.


The famous Chinese white dolphins
in Hong Kong waters

Long before human settlers arrived in Hong Kong, the region's marine waters supported a huge range of sub-tropical aquatic life. In the clearer oceanic waters of the east, sponges, corals and sea grasses thrived, along with numerous species of crustaceans, molluscs and fish. Meanwhile, the western waters became home of the famous Chinese white dolphins and porpoises.


Human beings have long harvested the wealth of the seas around Hong Kong through fishing (including fish farming and oyster cultivation), but that has been only one of many roles the sea has played in Hong Kong life. As Hong Kong has developed into one of the world's largest and most important ports, navigation through Hong Kong waters has increased immensely. The sea is also widely used for recreation and sports, with hundreds of thousands of Hong Kongers visiting beaches to swim or surf in the summer, diving to see the beautiful corals or getting out on the waves in boats of every description. Further, Hong Kong's marine waters are used for a number of very practical purposes, including for cooling in power plants and air conditioning systems, for toilet flushing, and as a way of disposing of treated effluent.



Challenges to Hong Kong's marine environment

Hong Kong's population began to rise in leaps and bounds in the 1970s and 1980s, and this was accompanied by intensive industrial and urban development. Pressure began to build up on the territory's marine waters, and the marine environment started showing signs of strain. To begin with, most of Hong Kong's sewage and wastewater ended up in the sea, but the bulk of it had received little or no treatment before discharge due to the lack of a developed sewer network and treatment facilities at that time. This led to rises in organic and inorganic pollutants, a reduction in the oxygen content of the water, and increased bacteria levels.


The problem was exacerbated by the rapid explosion of Hong Kong's population: by 2005, this had risen to 6.9 million people who were generating around 2 million tonnes of wastewater every day. To house the rising population the Government began building new towns in the 1980s, and while these proved to be masterful solutions to social and demographic issues, they did not always bring equal benefits to the surrounding environment. For example, two of them (Sha Tin and Tai Po) were built in the catchment area for Tolo Harbour, which due to its enclosed nature was highly sensitive to any increases in pollutants flowing into it.


Another major problem affecting the quality of Hong Kong's marine waters was the untreated waste generated by the livestock industry twenty years ago. Young Hong Kongers may be surprised to discover that, in the early 1980s, most parts of the New Territories and some urban areas were home to thousands of pig farms and chicken farms. Most of the large volumes of effluent deriving from these farms was disposed of directly into Hong Kong's rivers, which washed the pollution out to sea.


A further challenge to Hong Kong's marine waters came in the form of mud. Prior to the 1980s, the dumping of dredged mud from reclamation work and other urban development projects was largely unregulated. Dredged mud, which in some cases was contaminated, could be removed from one area of the sea bed and dumped elsewhere without restrictions, bringing disturbance to life on the sea floor and altering key characteristics of the marine environment.


Finally, it pays to remember that in the 1980s Hong Kong was home to far more industrial enterprises that it is today, when many factory owners have moved their production facilities across the border. Twenty years ago, thousands of factories-particularly in the Kwun Tong and Tsuen Wan areas-discharged their untreated industrial waste directly into sewers that flowed into the sea. This waste was typically high in chemical and metal content, originating as it did from factories involved in the textile, electroplating, PCB, bleaching and dyeing industries amongst others.



Government responses to protect the marine environment

In short, by the early 1980s some of Hong Kong's waters were being severely threatened by a mixture of pollution sources, while pollution controls were mostly largely inadequate. In response, the Government created an important blueprint for improving Hong Kong's marine waters under the new Water Pollution Control Ordinance. It divided all Hong Kong's marine water into ten Water Control Zones (WCZs), each of which was given boundaries based on water catchments and geographical characteristics. Then, the Government established a set of Water Quality Objectives (WQOs) and discharge standards for each WCZ. These WQOs laid out the qualitative and quantitative characteristics of water that need to be achieved to meet conservation goals and to support the various beneficial uses of different areas of water. They were designed to act as long-term environmental goals that would safeguard Hong Kong's marine environment. Other initiatives of the time included the 1986 Dumping at Sea Ordinance, which began to control the dumping of dredged mud in territorial waters. In 1997 the Government enacted the Environmental Impact Assessment Ordinance (EIAO), which laid out a framework for controlling the environmental impact (including any impact on the marine environment) of major development projects such as coastal reclamation. Further details of the steps taken by the Government to address and control water pollution problems are given in the next few chapters of this report.


The EPD monitoring vessel,
"Dr. Catherine Lam"

In 1986, the Environmental Protection Department (EPD) was established and entrusted with the task of monitoring Hong Kong's marine water. To do this it devised a comprehensive marine water monitoring programme, first implemented in 1986 and since then revised and further expanded. The monitoring programme is crucial for measuring to what extent individual Water Control Zones comply with the WQOs, and over time a huge database of information has been built up that enables long-term water quality changes to be detected. Based on this scientific information, the Government is able to assess the effectiveness of its pollution control measures, and plan further strategies.


The programme operates according to a set of very clear aims and objectives, as follows:

  • to indicate the state of health of coastal waters;
  • to assess compliance with the statutory WQOs;
  • to reveal long-term changes in water quality;
  • to provide a basis for the planning of water pollution control strategies.

In the past twenty years, the work of the EPD in monitoring marine water quality and implementing initiatives for reducing pollution has borne fruit. Overall compliance with the key Water Quality Objectives across Hong Kong waters has improved from 76% in 1986 to 85% and above since 2002. In the 1980s, 'red tides' were a very serious problem for Tolo Harbour. Since then, the frequency of their occurrence has been greatly reduced, as have general levels of nutrients and organic and other inorganic pollutants in many areas of Hong Kong's marine waters.


Overall compliance with the marine Water Quality Objectives in Hong Kong, 1986-2005

In areas such as Port Shelter, which has historically recorded excellent water quality, the EPD's efforts have ensured that water there has remained of high quality despite a steady increase in local population. In Victoria Harbour, meanwhile, the introduction of the Harbour Area Treatment Scheme (HATS) Stage 1 has resulted in 1.4 million cubic metres of sewage a day (or approximately 75% of the sewage entering the harbour) being treated. This has had a very positive impact on water quality in many parts of the harbour, especially at the eastern end.


The achievements of the EPD and the Government in reducing marine water pollution are particularly evident in areas where Hong Kong's marine waters are relatively enclosed, near urban areas, and receive large volumes of waste water, such as Tolo Harbour and Victoria Harbour. Elsewhere, changes tend to be less dramatic, because the ocean has a huge ability to dilute and assimilate pollutants entering it. Aside from pollution, other wider phenomena may also influence Hong Kong's waters, such as the effects of the Pearl River outflow further west, rainstorms, and even global changes such as the El Nino phenomenon or global warming. In the last 20 years, the monitoring detected an overall rise of sea water temperature of 0.3 óJ in the territory.


The water quality of most parts of Hong Kong's waters is relatively stable and generally slow to respond to specific sources of pollution. In addition to assessing effects of pollution and the mitigation measures implemented, the EPD's monitoring work is also carried out to gather long-term information that can enable more gradual trends to be identified and analysed. This more general understanding of the marine environment is something the EPD aims to achieve for all the marine waters it monitors. The more data collected by the EPD that can help in understanding the condition and behaviour of Hong Kong's marine environment today, the better will the Government be able to recognise and respond to future changes and new challenges that may arise.



Comprehensive marine water information available to all

The EPD has made special efforts to make sure the information it gathers from its marine monitoring programme is widely available to everyone. It publishes comprehensive water quality reports annually, and uploads regular water quality information onto its website. This data is widely used by Government policy makers, planners and analysts for assessing the impact on water quality of various marine-related developments such as reclamation and sewage discharge projects.


This report marks the twentieth year of the EPD's marine water monitoring programme. Normally, the EPD publishes an annual report each year, but in recognition of this anniversary the EPD has this year put together a 20-year historical survey of its work over the past two decades. This report is designed to offer a detailed picture of the monitoring programme and how it has developed over time, as well as outlining some of the improvements in Hong Kong's marine water profile that have been achieved over the last twenty years.

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