A-41 
Increasing the spatial variance results in a family of curves that is complementary to 
those that follow an increase in temporal variance. Increasing spatial variance results 
in a higher frequency of small proportions being out of compliance. It is not so much 
an all-or-nothing phenomenon. 
Example 4. Example 4 considers the effect of changing both temporal and spatial 
variance on the shape of the CFD. 
Table 5.4. Parameter values and key for the family of curves shown in Figure 5.4. 
CTt 
c 
color 
curve 
number 
3 
1 
1 
5 
Red 
1 
3 
2 
2 
5 
Orange 
2 
3 
3 
3 
5 
Brown 
3 
3 
4 
4 
5 
Green 
4 
3 
5 
5 
5 
Blue 
5 
Figure 5.4. A family of curves illustrating the behavior of the CFD as both temporal and 
spatial variance increases. The parameter values for each curve and the corresponding 
curve number are given in Table 5.4. 
appendix a 
The Cumulative Frequency Diagram Method for Determining Water Quality Attainment 
