Organic matter from wastewater discharges results in a transboundary impact. While the quality of groundwater had been reported as, in general, very good, and often used for water supply without or with very little treatment in the former Yugoslav Republic of Macedonia, the occurrence of nitrogen, pesticides, heavy metals, pathogens, industrial organics and hydrocarbons in the Gevgelija/Axios-Vardar (No. The salinization observed is of natural origin.