Lička Jesenica is a sinking river situated in the Dinaric karst environment of the Lika region of Croatia. The two main karst springs, Veliko Vrelo and Malo Vrelo, provide the majority of Lička Jesenica's water. Because of the quality and abundance of the water they contain, these springs are strategically important to the public water supply. Previous knowledge regarding the springs` karst system has been negligible. Therefore, a bulk hydrogeological research program was conducted with the purposes of establishing protection zones and assessing the springs' water-supply potential. The research work comprised the following methods: hydrogeological mapping, setting up of monitoring stations for evaluating discharge and water quality, time series analyses (hydrograph–chemograph), hydrochemical analyses, and geophysical surveys. The main results and conclusions of the research include the following: (i) confirmation that both springs drain a common aquifer; (ii) determination of the highly vulnerable nature of the karst systems; (iii) identification of the Veliko Vrelo Spring's more direct connection to the aquifer-drainage system in comparison to the Malo Vrelo; (iv) estimation of the positions and depths of the springs` main feeding conduits; (v) confirmation of the extent of the geologically presumed catchment area; and (vi) finally, establishment of sanitary protection zones. Copyright © 2012 John Wiley & Sons, Ltd.