The recharge of karst aquifers is significant for the effective management of groundwater resources, and its estimation should be tailored to accommodate their specific hydrogeological characteristics. This study provides a two-step methodological approach for the determination of karst aquifer recharge. Initially, mean annual recharge rates were estimated in the karst system of Ziria (Southern Greece) utilizing the APLIS and modified APLIS methods in order to decipher which was the most suitable version for recharge assessments. The results indicated similar mean recharge rate values at 42.7% and 41.4%, respectively, but significant differences in the spatial distribution. The modified methodology emerged as a more accurate and realistic approach, mainly due to the incorporation of permeability assessments. The final phase of the methodological approach involved the application of modified APLIS in two additional karst hydrosystems, Planitero and Xiromero, while a quantitative cross-comparison of the recharge rates was obtained for a deeper understanding of the factors controlling the groundwater recharge process. In Ziria, recharge rates exhibit a relatively uniform distribution throughout the area, with a median value of 46.7%. Conversely, in Planitero, High recharge rates (60–80%) occupy 56.8% of the surface, while in Xiromero, Moderate recharge rates (40–60%) dominate, representing 53.4% of the land coverage. These variations underscore the spatial heterogeneity of recharge within the karst systems, highlighting the importance of considering local geological and hydrological conditions in its assessments. The methodological approach of this study is flexible and can be adapted to different karst sites for the determination of recharge regimes, contributing to the alleviation of the groundwater depletion issue.

Aquifer structure plays a critical role in controlling groundwater flow through both saturated and unsaturated zones. In remote and rugged terrains, GIS and remote sensing tools are essential for delineating geological structures. This study integrates stereoscopic aerial photograph analysis and GIS-based hill-shading techniques to enhance lineament detection within the Ziria karst system in northern Peloponnese, Greece. By combining these techniques, 1,214 lineaments were identified, revealing structural and erosional features that were not detected using a single approach. Field validation confirmed that lineaments identified by aerial photography corresponded to faults or fracture systems, with a predominant NNW–SSE orientation. Fracture network analysis was subsequently applied to assess structural feature connectivity. The results indicated a low degree of connectivity within the lineament dataset, with isolated (I) features being more prevalent than branching (Y) and intersection (X) nodes. Additionally, detailed karst landform mapping identified 325 karst depressions, where approximately 62.5% of the depressions were in direct association with the identified lineaments. The majority of the remaining karst depressions, while not in direct contact, were predominantly located within zones characterized by high lineament density. The mapped lineaments were ultimately used to refine the boundaries of the karst aquifer, defined by crystalline metamorphic bedrock, and to update the area’s groundwater vulnerability and recharge regimes. The findings emphasize the role of structural control in shaping hydrological systems, offering a robust framework for assessing various hydrogeological aspects and guiding effective groundwater management in tectonically active karst regions.

In Greece, the geodynamics of karst hypothermal–mineral springs, in which often shallow fresh groundwater is intermixed, is not well known. This study aims to investigate the monthly hydrochemical variability of three karst hypothermal mineral springs in Greece named Kyllini (southern Greece), Agiasma (northern Greece), and Voskina (northern Greece). Hence, monthly samples were collected and an analysis of major and trace elements, ion ratios, and saturation indices was performed, as well as statistical analysis and cross correlation. Elevated concentrations of Ca²⁺, Mg²⁺, and HCO₃⁻ are present in all springs, indicating that the dissolution of calcite and dolomite constitutes the main water–rock interaction process. Additionally, the mobilization and transport of Mn, Fe, and As are favored by the negative ORP values. However, there are also differences between the three springs. The Kyllini spring is characterized by high salinity and dominated by Na–Cl–HCO₃ water, while the Agiasma spring exhibits a mixed water type with moderate salinity. The Voskina spring reflects a fresher, bicarbonate-dominated aquifer system with modest trace element mobilization. This study provides the first comprehensive monthly assessment of the hydrochemical response of karst hypothermal–mineral springs in Greece, offering new insights into seasonal geochemical dynamics.