Karst spring catchment: an example from Dinaric karst

Definition of karst spring catchment or basin area and boundaries belongs to one of the greatest problems of karst hydrology and hydrogeology, not adequately solved until now. This paper tries to address main problems in defining this crucial parameter. The theoretical aspect of this issue is discussed in the first two chapters. We have presented the example of the catchment area and boundaries definition for the karst spring Žrnovnica catchment in Dinaric karst. Topographic catchment area of the Žrnovnica Spring is 8.4 km². The significant discrepancy in size of the hydrological–hydrogeological and topographical catchment is very common characteristic for the springs located in the karst areas. In the case of the Žrnovnica Spring, the hydrogeological catchment is at least seven times larger than topographic. Two following simple hydrological methods are used in order to calculate its hydrologic–hydrogeologic catchment: (1) the relationship between mean annual discharges and annual rainfall falling on the catchment, and (2) the Turc method. It is estimated that hydrogeologic catchment area of the Žrnovnica karst spring is much larger and very probably ranges between 60 and 80 km². These values represent first rough assessment, which should be confirmed by more detailed interdisciplinary investigations. According to the performed tracing tests, it seems that the catchment spreads on the north-east from the topographic catchment and that the Žrnovnica Spring karst aquifer is fed by groundwater overflow from the neighbouring more abundant karts spring Jadro.