Natural tracers as a tool for understanding the functioning of the karst system and its vulnerability - a case study of the Manastirec spring

The Manastirec spring is the only drinking water source that supplies 200 inhabitants of the municipality Goren Manastirec in West-Central Macedonia. Natural tracers were applied in order to characterize the properties of the groundwater flow and transport of contaminants through the karst system and to study the functioning of the spring. Water level, temperature and electrical conductivity of the spring were measured with data logger in hourly intervals during several rain events in 2015 and 2016. Rain events caused rise of water level and decrease of both water temperature and electrical conductivity. Concentrations of calcium, magnesium, sulphate and nitrate present in spring water were analyzed during the end of July 2016, during three rain events. The results showed that sulphate and Ca/Mg ratio increase, whereas nitrate decrease after rain events. All results demonstrate high vulnerability of the Manastirec spring to contamination.