Definition of groundwater genesis and circulation conditions of the complex hydrogeological karst system Mlava–Belosavac–Belosavac-2 (eastern Serbia)

The complex karst system named Mlava–Belosavac–Belosavac 2 is one of the five systems isolated according to detailed research conducted within the Beljanica karst massif which belongs to the Carpatho-Balkanides. In order to define the genesis of groundwaters from these three springs, the deepening of the main karst channel, as well as their underground connection, a multiparameter approach has been applied consisting not only of hydrological, hydrochemical and detailed isotope research methods (stable isotopes 18 O, 2 H and 13 C, as well as radioactive 3 H and 3 H + 3 He isotopes), but also of cave diving exploration of the Mlava Spring. This method was performed in order to define the morphology of the main karst channels and its spatial position. The obtained results have shown that these three springs belong to the same karst system (they have the same recharge zone and relatively similar hydrochemical and isotopic characteristics, and any deviation is a consequence of a different mean residence time that water spent underground), that emerge to the surface along the contact line with hydrologic barriers through karst channels that have different depths. Also, the research has confirmed that the karst channels have well-developed systems of channels in the vertical profile, with a dominant development of deep syphonal circulation.