CCME WQI ¼ 100 À
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
F
2
1 þ F
2
2 þ F
2
3
q
1:732
0
@
1
A
ð3:9Þ
2 Water Quality Module Formation
A general water quality module with diffusion transportation can be readily derived
based on the mass conservation and Fick
’ s diffusion principle (Eq. 3.10).
Table 3.12 Advantages and disadvantages of CCME WQI [11]
Advantages
Disadvantages
1.
Flexibility in the selection of input
parameters and objectives
1. Missing guidelines about the variables to be used
for the index calculation
2.
Adaptability to different legal
requirements and different water
uses
2. Missing guidelines about the objectives specific
to each location and particular water use
3.
Statistical simplification of complex multivariate data
4.
Clear and intelligible diagnostic for
managers and the general public
3. Easy to manipulate (biased)
4. The same importance is given to all variables
5.
Suitable tool for water quality
evaluation in a specific location
5. No combination with other indicators or biological data
6.
Easy to calculate
6. Only partial diagnostic of the water quality
7.
Tolerance to missing data
7. F1 not working appropriately when too few variables are considered or when too much covariance exists among them. The n factor has too
much weight in calculating the index
8.
Suitable for analysis of data coming from automated sampling
9.
Experience in implementation
10. Considers amplitude
(of difference from the objective)
Fig. 3.6 Conceptual model
for diffusion
3 Surface Water Quality and Analysis
89