River Water - Our Invaluable Asset

In Hong Kong, there are hundreds of rivers, streams and open nullahs. They are finite resources having different beneficial uses: such as supply to reservoirs, irrigation, preservation of aquatic life, recreation and passage of storm water to the sea. Monitoring of the water quality of Hong Kong's rivers is an important part of the work of the Environmental Protection Department (EPD). It serves the following purposes:

• To indicate the state of health of rivers;
• To reveal long-term changes in the water quality of rivers;
• To assess compliance with the statutory Water Quality Objectives (WQOs);
• To provide a basis for the planning of water pollution control strategies.

River Water Quality Monitoring

EPD regularly monitors water quality at more than 80 sampling stations in over 30 rivers and streams in the territory. In situ field measurements are performed and water samples are collected for further laboratory analyses mostly on a monthly basis. The monitoring covers more than 40 parameters including physico-chemical characteristics, organics, nutrients, toxic metals and coliform bacteria. The rates of annual compliance with the statutory WQOs are assessed based on the data obtained during the year.

Water Quality Index (WQI) for Rivers

In addition to the WQOs, a Water Quality Index (WQI), based on the level of dissolved oxygen, 5-day Biochemical Oxygen Demand and ammonia-nitrogen, is used to indicate the extent of organic contamination of the rivers. The WQI classifies the river water quality into 5 categories according to the level of organic pollution. In recent years, most of the rivers in Hong Kong are within the "Fair" to "Excellent" range.

Information on River Water Quality and Hong Kong's Environment

Detailed information on Hong Kong's river water quality is published in the annual report River Water Quality in Hong Kong. This report is available in public libraries and Environmental Resource Centres,  and can be downloaded from EPD's River Water Quality Web Page.

Other information on Hong Kong's environment can be obtained from EPD's homepage (http://www.epd.gov.hk).