Water Quality Index

The water quality index (WQI) is a measurement used as a basis for assessing the level of pollution and categorizing it into classes as stipulated in the National Water Quality Standards for Malaysia (NWQS).

CLASS	WQI	DESCRIPTION OF CLASSES

I	> 92.7	Natural condition Water Supply - no treatment required Aqua-culture - supports very sensitive river species

II	76.5 - 92.7	Water supply - basic treatment required Aqua-culture - supports most sensitive river species Recreation - used for recreational purposes

III	51.9 - 76.5	Water supply - extensive treatment required Aqua-culture - supports hardened river species Source of drinking for animals

IV	31.0 - 51.9	Irrigation only (For paddy fields and farming purposes)

V	< 31.0	The condition of water is untreatable

SAMPLES OF RIVER CLASSIFIED BY WATER QUALITY INDEX


Upstream of Sg Langat Water Quality Index Class II		Sg Merbau Water Quality Index Class III


Sg Rinching Water Quality Index Class III		Sg Cheras Water Quality Index Class IV