Development of a conceptual hydrogeological model based on geological mapping and stable isotopes: a case study of Šmarna gora, SloveniaJanža, Mitja (Avtor) Marković, Tamara (Avtor) Jamnik, Brigita (Avtor) stable isotopesgroundwater rechargemean residence timetransit timeprecipitation pattern changedolomite aquiferdecentralized water supplySmall decentralized water supply systems are often sensitive to local pollution and require a clear understanding of recharge conditions and the hydrodynamics within the water resource catchment. This study develops a conceptual hydrogeological model for the Šmarna Gora area based on geological mapping, long-term monitoring of chemical parameters, and stable isotope analyses (δ18O, δ2H) of precipitation and groundwater. The study was initiated in response to rising pollutant concentrations in the drinking water. Estimates of transit time (TT) and mean residence time (MRT) were used to characterize recharge, mixing processes, and differences between the SG and ZAVRH wells, the existing and alternative water supply wells. Isotope data show that the aquifer is predominantly recharged during colder periods and that Mediterranean air masses have become an increasingly important source of precipitation, suggesting a shift in precipitation patterns. The results indicate that SG has longer TT (6–8 months) and MRT (up to 1–2 years). In contrast, ZAVRH shows shorter TT and MRT (4–6 months), and lower pollutant concentrations. The hydrogeological regime in the catchment of the ZAVRH well is characterized by a dynamic, fast-flowing system with limited storage and more intensive dilution of contaminants by infiltrating water, whereas the catchment of the SG well functions as a deeper and more buffered aquifer with prolonged groundwater residence and a more direct hydraulic linkage to the contaminant source. The findings distinguish two hydrogeological regimes and provide a basis for planning water supply solutions and protection measures.20262026-06-24 09:53:06Neznano30390UDK: 556.3ISSN pri članku: 2073-4441DOI: 10.3390/w18121386COBISS_ID: 281479939sl