Monitoring of hydrogen and oxygen stable isotopes changes for the purpose of water protection: the case of Rijeka town springs

Sanitary protection zones of potable water springs in karst areas represent the most widespread protection areas related to protection of the water systems. Karst aquifers are, due to the rapid reaction to the precipitation inputs and weak self-purification capacity, highly vulnerable to pollution. Determining the water origin and aquifer recharge areas is important for karst aquifer protection. Stable isotopes of hydrogen and oxygen, as natural tracers, have been proven to be useful in determination of the above mentioned parameters. We present an example of stable isotopes study for springs Zvir and Marganovo and six wells of Zvir II that are located in an underground gallery. All of them are connected to the river Rječina system. The spring Izvor Rječine is the backbone of Rijeka town’s water supply during the periods of high water and the spring Zvir during the dry months. Zvir II and Marganovo are not included in the water supply system.