WQOs

Water Quality Objectives (WQOs)

Our marine waters are a valuable natural asset. They support a huge variety of wildlife, from microscopic plankton, sea grasses and corals, to green turtles, horseshoe crabs, dolphins and finless porpoises. For our daily life, they also support a variety of 'beneficial uses' (BUs), including amenities, mariculture, fisheries, cooling, toilet flushing, navigation, effluent discharge, sand borrowing and mud disposal.

Various beneficial uses supported by our marine waters
Marine Parks
Mariculture
Chinese White Dolphin Bathing Beaches Marinas Windsurfing

We need to protect our marine waters to ensure that they are fit for marine life growth and different human uses in a sustainable manner. Many overseas jurisdictions establish water quality criteria or water quality guidelines or the like (in Hong Kong, the term "Water Quality Objectives" (WQOs) is used) as the benchmarks. The WQOs can be numerical or narrative, and include various parameters to describe the physical, chemical and biological properties of the marine environment, and are designed to measure the "environmental health" of a water body. In general, waters with more sensitive uses, including sanctuaries for important species such as the Chinese White Dolphin, mariculture areas and bathing beaches, require a higher level of protection (i.e. with more stringent WQOs), while water bodies with less sensitive uses such as navigation require a relatively lower level of protection (i.e. with less stringent WQOs). Sensitive water bodies are mostly found in the eastern and southern waters of Hong Kong.

The WQOs provide an objective and scientific basis for us to formulate and implement pollution control strategies, and to plan and develop infrastructure in a suitable and sustainable way, with a view to preventing unnecessary pollution and minimising the impact on the water quality.

Under the Water Pollution Control Ordinance (WPCO), Hong Kong's waters are divided into ten Water Control Zones (WCZs), and each WCZ has a set of WQOs. The first set of the WQOs was promulgated under the WPCO for application to the Tolo Harbour and Channel WCZ in 1982. The same set of WQOs, after some modification, has subsequently been applied to the other nine WCZs from 1987 to 1996.

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