Abstract
The purpose of the paper is to develop new synthetic indexes of water qualities of rivers and to clear their significance in the evaluation of water pollution of Japanese rivers. The synthetic indexes were produced from their data of physical and chemical water qualities as well as flow-rates, including also the estimation of the Saprobic levels from those physical and chemical data. The principal component analysis (PCA) was applied to 119 rivers of class “A”in Japan whose seven years data were selected from 1975 to 1993. The first main component F1 represents the factor of loading of water pollution. The second one F2 represents the factor of its level.
Two patterns of river pollution can be found by plotting pairs of F1 and F2 values of each river on the graph of the F1, F2-axis. Correlation between the synthetic indexes and watershed factors of 33 “A”rivers in Japan was investigated. Each synthetic index, F1 as well as F2, can be expressed by multiple regression formula with some watershed factors.
It's concluded that F1 and F2 values can be used as the synthetic indexes of water qualities of rivers in Japan in evaluating their water pollution synthetically.
