Abstract Reliability is the greatest concern in recent karst vulnerability assessments. Checking the validity of results and understanding the operation of karst systems are therefore the most promising areas for improvement. We report an application of the Slovene Approach to a test site in the Gömör-Torna Karst of Hungary and Slovakia. The resource vulnerability map provided an appropriate result and showed that the overlying sediments and thicker soil may effectively decrease the vulnerability of this unconfined area. The source vulnerability of the Kis-Tohonya Spring was evaluated for the purposes of protection zoning. The results of long-term hydrograph and recession curve analyses were helpful in understanding the functioning of the Kis-Tohonya Spring and the karst system. The importance of the different regimes contributing to the slow and fast flow of the spring under different hydrological conditions was shown. Ongoing research aims to feed these results back into the source vulnerability assessment of the spring.