Although the biotic indices and physicochemical
variables generally support each other, the deviation
between indices might be explained in light of the quality
classes, since the quality class levels and the systems of
categorization have been limited by different values. For
example, Klee’s (1990) 7-level quality classes have been
applied in this research, while the ASPT’s 4-level quality
classes and the BMWP’s 5-level quality classes have also
been applied to the data.