Drinking water supply is nowadays quite a matter of course. The nature with its natural features enables it for us. Diploma work deals with the protection of water resources, which are used for drinking water supply in the municipality of Črnomelj. Legislation in the field of water resources protection, which is one of the most important factors of water resources protection, is presented. The aim of this work is to determine the potential contaminants, identify pollutants and to demonstrate trends of these pollutants in water resources used for drinking water supply in the municipality of Črnomelj. Based on the results, reasons for occurence of certain pollutants on the water source are given.