2.6 Water quality assessment based on the biotic index of macroinvertebrates
\begin{equation} \text{BI}\sum_{i1}^{S}{n_{i}a_{i}/N}\backslash n\nonumber \\ \end{equation}
where ni represent the abundance of each species in each sampling sites, ai represent the tolerance values of each species and the N represent the total abundance of each site. The key metrics of the B-IBI health assessment system include: phylogenetic diversity (PD), the number of EPT (Ephemeroptera, Plecoptera, Trichoptera) taxa, the percentage of Ephemeroptera, the percentage of tolerant groups, BI (Biotic Index) and the percentage of clingers. Based on BI values, sampling sites were classified as follows: excellent (0-2.97), good (2.98-4.72), fair (4.73-6.48) poor (6.49-8.24) and bad (>8.24), accordingly to Satiou et al. (1987).
Results