River Water Quality Index (WQI)
The water quality of a water body may be defined by numerous physico-chemical, biological and ecological parameters. A Water Quality Index (WQI) is a widely practiced management tool to provide a useful way of summarizing data representing large numbers of water quality parameters, while at the same time facilitating the understading of water quality information to the general public in a more systematic and consistent manner.
A WQI also aids in establishing priorities for protection/ management by providing quantitative data on overall water quality status. In fact, the United Nation Global Environmental Monitoring System (UN-GEMS), in line with its Sustainable Development Goals (SDGs) #6 (Ensure availability and sustainable management of water and Sanitation for all) has implicitly address the importance of water quality index as one of the tools to ensure sustainable management of water resource.
A WQI is a single value that aggregates numerous water quality parameters considered most relevant into one concise and objective value, representing the state of water quality in any given water body. Normally, WQI is developed to associate with specific beneficial uses of the water body.
The parameters chosen are generally based on the following criteria:
The WQI as applied in Malaysia is formulated based on an opinion poll approach whereby the selected water quality parameters are derived from the professional opinions of numerous water quality experts. As the chosen parameters differ in their respective degree of effects on the beneficial uses and protection needs of aquatic ecosystems, a weightage factor is associated with each parameter. Assignment of weight is based on a severity rating for the designated protection needs.
The water quality parameters chosen to represent the WQI in Malaysia are BOD, COD, TSS, pH, DO and ammoniacal-N.
National Water Quality Standards For Malaysia
DOE Water Quality Index Classification
Water Classes and Uses
DOE Water Quality Classification Based On Water Quality Index
WQI=(0.22*SIDO) + (0.19*SIDOD) + (0.16*SIDOD) + (0.15*SIAN) + (0.16*SISS) +(0.12*SipH)
SIDO = SubIndex DO (%saturation)
SIBOD = SubIndex BOD
SICOD = SubIndex COD
SIAN = SubIndex NH3-N
SISS = SubIndex SS
SipH = SubIndex pH
0 ≤ WQI ≤ 100
Best Fit Equations For The Estimation Of Various Sub-index Values
*means multiply with