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Environmental Protection Interactive Centre

Recent River Water Quality (Dissolved Oxygen and 5-day Biochemical Oxygen Demand in river waters)

What are Dissolved Oxygen and 5-day Biochemical Oxygen Demand?

Dissolved Oxygen (DO) and 5-day Biochemical Oxygen Demand (BOD5) are two important parameters indicating the general conditions of water.

Dissolved Oxygen indicates the total amount of oxygen dissolved in the river and stream water. Most aquatic organisms need oxygen for respiration and maintenance of life. Dissolved oxygen content in water can also be affected by natural factors including weather, temperature, water turbulence, hydrological conditions, algal blooms, etc.

5-day Biochemical Oxygen Demand measures the amount of oxygen consumed by microorganisms in decomposing organic matters in water. It is generally used to reflect the level of organic pollution of environmental water.

The recent DO and BOD5 data at selected stations in 13 major rivers and streams are available on this web page.

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Display data under following condition
Map of Water Control Zone
TR19ITR12ITR13MW1PR1IN1RB3GR1YL3KT1TN6TW3KN3Shing Mun Main Channel (TR19I)Lam Tsuen River (TR12I)Tai Po River (TR13)Mui Wo River (MW1)Ho Chung River (PR1)River Indus (IN1)River Beas (RB3)River Ganges (GR1)Yuen Long Nullah (YL3)Kam Tin River (KT1)Tuen Mun River (TN6)Sam Dip Tam Stream (TW3)Kai Tak River (KN3)