Biologieal Evaluation by Benthic Fauna for Water Quality in the Rivers of Kumamoto Prefecture

Abstract

The analysis was made by using the data at 100 stations in the rivers of Kumamoto Pref., for the purpose of supporting the validity of the benthic fauna as the indicator of water quality.
The principal component analysis was made by six factors of water quality (BOD, COD, C_l-, NH4-N, T-N, T-P). In consequence, the first principal component (Z₁W) showed the pollution. Though the correlation coefficient between Z₁W and PI(N) is relatively good with γ=0.804, there is the case that the value of PI (N) is evaluated β-ms in spite that Z₁W judges it very clear. The reason is that the water areas of β-ms contains “very clear water area” and “clear waterarea”.
Accordingly, the values of new five grades of water quality (Q) and the method of biological evaluation of water quality (BE) were tested. The correlation coefficient between the values of BE using Q and Z₁W is good with γ=0.833. The difference between “very clear water area” and “clear water area” was evaluated.