This chapter introduces the EPD's marine water monitoring programme by outlining some key Government initiatives of the 1980s that provided the foundation upon which the monitoring programme was built: the Water Pollution Control Ordinance, the Waste Disposal Ordinance, the declaration of Water Control Zones, and the laying out of Water Quality Objectives for each of the Water Control Zones.

The Water Pollution Control Ordinance (1980)

Faced with significant water pollution issues in the late 1970s and early 1980s, the Hong Kong Government declared its commitment to protecting the water and marine environments of the territory and safeguarding their huge diversity of aquatic life. In 1980, it enacted the Water Pollution Control Ordinance, which laid the legal basis for introducing a range of measures designed to control water pollution in Hong Kong. As a first step, it provided for Hong Kong waters to be divided into ten Water Control Zones (WCZs), each of which was to be provided with scientific Water Quality Objectives appropriate to their characteristics and use.

The Waste Disposal Ordinance (1980)

Chemical Waste Treatment Centre in Tsing Yi

In the 1980s, discharges from factories and industrial sectors often contained high concentrations of harmful chemicals which ended up in the sea as sediment. For example, the electroplating industry discharged significant amounts of copper and nickel. The Waste Disposal Ordinance which controls disposal of chemical wastes was enacted in 1980. In 1992, the Government enacted regulations under the WDO that strengthened controls over the discharge of chemical waste into sewers. (Apart from controlling the disposal of chemical waste, this ordinance also regulated the disposal of waste from livestock.) In 1993, the Government commissioned the first comprehensive Chemical Waste Treatment Centre in South-East Asia. Located in Tsing Yi, it provided a much-needed solution for the problem of disposing of chemical waste.

The Water Control Zones (1987-1996)

Based on specific catchment areas, the aim of creating Water Control Zones was to control pollution, improve water quality, protect ecosystems and maintain the beneficial uses of different bodies of water for activities such as swimming, surfing, sailing, fish culture and navigation. The map shows the location of each WCZ and the year in which they were first declared, after which discharges began to be controlled under the Water Pollution Control Ordinance.

Declaration of the ten Water Control Zones

The ten Water Control Zones declared under the Water Pollution Control Ordinance

Tolo Harbour WCZ - declared in 1987

Southern WCZ -declared in 1988

and Port Shelter and Junk Bay WCZs -declared in 1989

and Deep Bay and Mirs Bay WCZs -declared in 1990

North Western WCZ -declared in 1992

and Western and Eastern Buffer WCZs -declared in 1993

Victoria Harbour (Phase 1) WCZ -declared in 1994

Victoria Harbour (Phase 2) WCZ -declared in 1995

Victoria Harbour (Phase 3) WCZ -declared in 1996

In this report, the marine waters of the ten Water Control Zones have been grouped for ease of discussion into four larger areas, roughly corresponding with the eastern, southern, central and western bodies of water surrounding Hong Kong. They are as follows:

• Eastern Waters: made up of the Tolo Harbour and Channel, Port Shelter and Mirs Bay Water Control Zones. Details of the Eastern Waters can be found in Chapter Five.
• Southern Waters: made up of the Southern WCZ, mainly the waters south of Hong Kong island and east of Lantau. Details of the Southern Waters can be found in Chapter Six.
• Central Waters: made up of the Victoria Harbour, Junk Bay, Eastern Buffer and Western Buffer WCZs. Details of the Central Waters can be found in Chapter Seven.
• Western Waters: made up of the Deep Bay and North Western WCZs. Details of the Western Waters can be found in Chapter Eight.

The four marine water bodies of Hong Kong

The Water Quality Objectives

Repulse Bay, one of Hong Kong's most beautiful beaches

As each Water Control Zone was declared, it was allocated a set of Water Quality Objectives (WQOs). These WQOs represent qualitative and quantitative characteristics that have been developed for Hong Kong conditions, based on scientific research, overseas experience and available local data. The WQOs for each Water Control Zone can be different depending on each Zone's location and typical uses, but for each Zone they are designed "to promote the conservation and best uses of Hong Kong's waters in the public interest". For example, some Water Control Zones are primarily used for navigation while others are widely used for swimming and recreation, and the WQOs for such different Zones would reflect that difference.

To assess water quality in Hong Kong, the EPD's monitoring programme tests many different parameters including those in the WQOs. Five of the tested parameters are related to the physical and aggregate properties of marine water: they are temperature, salinity, pH, suspended solids (SS) and dissolved oxygen (DO) (bottom and depth-averaged). These parameters are highly important ones, because most marine life is especially sensitive to changes in temperature, salinity (i.e. salt content), and pH (i.e. acidity).

As for suspended solids, as they increase sea water becomes more turbid, and comes to look brownish. At the same time, photosynthesis decreases because less light can penetrate the water. That in turn leads to reduced growth of plants and algae that form the food of many fish and shellfish. In addition, high levels of SS can harm fish by blocking their gills, reducing their growth rates, and lowering their resistance to disease.

Finally, dissolved oxygen is essential for the survival and growth of aquatic organisms. When DO in water falls below a certain level, many species of marine life are not able to survive. What is more, low levels of DO encourage the formation of hydrogen sulphide gas (H2S), which not only smells very bad but is also toxic to living organisms.

Another group of important parameters of the WQOs are those relating to nutrients and inorganic constituents of marine water. While some nutrients are essential for the growth of aquatic plants and phytoplankton, high levels (for example, from sewage or stormwater run-off) can cause major problems to marine life. When there are high levels of inorganic nutrients in water, algal growth can spiral out of control, reducing dissolved oxygen and forcing out other forms of aquatic life. Within this category, the WQO parameters cover total inorganic nitrogen (TIN) including ammonia, nitrate and nitrite, and unionised ammonia. Unionised ammonia is a form of ammonia which is toxic to marine organisms.

Red tide encroaching Middle Bay in November 1998

Finally, the WQOs include certain biological and microbiological parameters. These include E.coli bacteria, which indicate pollution caused by sewage or other faecal waste, and chlorophyll-a, a plant pigment which when it occurs at high levels indicates the active production of algae in the form of algal bloom. The latter is important because red tides and harmful algal blooms can be harmful both to fish culture and even human health.

The table on Appendix page A-11 summarises the overall WQOs for marine waters in Hong Kong. It lists the individual parameters making up the WQOs on the left, and the specific objective for each parameter alongside. On the right, the table shows to which Water Control Zones that particular WQO applies.