Abstract
The principal component analysis and cluster analysis were applied to the groundwater quality data in terms of 16 indices. These analyses showed that the wells, which the data were collected from, could be classifyed into four groups. Two of them were supplied water to from the upper one of vertically stratified groundwater reservoirs, and the others from the lower reservoir. Comparing the result with the tetrachloroethylene concetration of the well water, it was revealed that the some limited local spots were contaminated by the chemical in the upper reservoir, whereas the whole was contaminated in the lower reservoir. The classification enabled us to make a contour map of the chemical concentration to visualize the present state of the groundwater pollution in the area.
