In our study, samples were taken from the groundwater that is used for drinking and irrigation in the Melendiz Water Basin, and the quality of water and the factors causing pollution were determined by evaluating them according to “Continental Water Sources Quality Classification Criterions” (Republic of Turkey Ministry of Environment and Forest/Regulation for Water Pollution Control). When the analysis results of samples taken between 2006 and 2009 were compared, it was determined that the amount of pollution increased in time. Moreover, the seasonal variations of ground water quality criterions were determined and the precautions that should be taken to minimize this pollution were discussed.