Karst aquifers are heterogeneous terrains, where it is hard to assess any hydraulic parameter. Therefore, a multidisciplinary approach is necessary for research on karst aquifers. The catchment area of the Gacka river springs is typical Dinaric karst terrain formed of karstifi ed carbonates. Groundwater fl ow is mostly directed by preferential fl ow paths usually connected with main faults and fracture zones. In the presented case study, structural, geological, and tectonic characteristics were defi ned. A recession diagram was created, and the water balance was calculated. Tracertest data were also used for analysis. All data were compared with the bulk hydrogeochemical and isotopic analyses of spring and surface waters. For this purpose, samples were obtained every month for one hydrological year at 17 sampling locations. Processing of all these data allowed a tenable defi nition of the Gacka spring catchment area.