In Erbil city; more than 30% of the water supply is derived from wells. Since the wells are located through the city, the quality of their waters may have widely variation.
Principal components analysis technique (PCA) was used to processing the physical, chemical and biological data of several wells at different parts of Erbil city to define the components or factors that responsible to the main variance in Erbil ground water quality. The correlation matrix also adopted in data analysis to determine the relationships of each parameter with the others.
The results of PCA showed the domination of three factors that responsible of about 68% of the ground water variation these factors are: change of the rock nature with 31%, human activities impact with 20.9%, and 16.8% of variation is according to the agricultural and storm water effects.
The correlation matrix had shown that there are two strong direct correlation between TDS and TH with 0.73, and opposite correlation between pH and Coliform bacteria with 0.53 the correlation between other water quality parameters is weak and less than 0.40.
Keywords: Ground water quality, Principal component analysis, Factor analysis, Erbil.