The relative importance of s
ix water quality
variables
was
considered in
a
Water Quality Index (WQI) calculation by the Malaysian
Department of Environment (DOE).
This comprised:
Dissolved Oxygen (DO), Biochemical Ox
ygen Demand (BOD), Chemical
Oxygen Demand (COD), Suspended Solid (SS), potential of Hydrogen (pH) and Ammonia (AN). The relative importance established
in the formula
was
based on expert opinions, very subjective in nature
,
and do not consider the interrel
ationships among the variables.
The relationships of the variables are important due to the nature of multidimensionality
and
complex characteristics
found
in river
water. In the study, water quality
indices
were clustered into three natural groupings iden
tified by high-pollution sources (HPS),
moderate-pollution sources and low-pollution sources. The prior information of natural groupings based on cluster analysis, CA
,
was
then used in discriminant analysis, DA
. This
obtained
the related linear combinations of the six main variables in WQI formula, i.e.
discriminant functions that best separate the three identified groups.
Apart from that, the summary index based on the
interrelationships among the variables from DA indicates the difference
in
ranking of the relative impor
tance for each variable
compared
to the classical approaches used in WQI-DOE. We firmly believe that the results obtained can be used as a guide
to
investigate other influential available variables in
the water quality of
Langat River
