Springs have an important role both in groundwater flow system understanding and in maintaining groundwater-related ecosystems. The aim of the research of the lukewarm karst springs in Kistapolca is to understand the origin of the elevated temperature (22-24 °C), i.e., whether it is the result of mixing of cold and thermal waters or it represents the terminal area of intermediate flow systems. This question has also an important relevance to the evaluation of recent cave formation in the area. In case of mixing of different waters dissolution by mixing corrosion could take place. This scenario was proposed for the formation of the Beremend Cave, which is situated in the close vicinity of the springs, and which is the only known cave of the area, where the passages are partly filled by water. Therefore, several methods, including geophysical, geochemical and stable isotope measurements, evaluation of continuous-time series of water level change, temperature, and electrical conductivity data and hydraulic evaluation of vertical flow conditions by pressure-elevation profiles were combined in order to acquire information about the hydrogeological environment and flow conditions in the area. The results show that a higher order flow system derived from the Villány Hills feeds the springs in Kistapolca without significant local influence. In addition, the results related to the Beremend Cave indicate that cave formation by mixing corrosion is not an active process today in the area, the cave is rather influenced by local processes.
Lake Velence is a shallow soda lake whose water level and water quality show a severely deteriorating tendency in recent years. Until recently, the groundwater component in the lake’s water budget has not been taken into consideration. To integrate the lake into the groundwater flow system at the regional scale, methods of “basin hydraulics” were applied. In addition, 17 water samples were collected for δ2H and δ18O, and for ΣU, 226Ra and 222Rn activity measurements to use these parameters as environmental tracers of groundwater contribution. Groundwater mapping revealed that groundwater recharges in Velence Hills and the local elevations south of the lake, whereas discharge occurs by the lake’s shoreline and along surface watercourses. The results indicated that Lake Velence is the discharge point of local groundwater flow systems known to be more sensitive to climate changes and anthropogenic activities (e.g., contamination, overexploitation). Groundwater and lake water have similar uranium activity concentrations serving as another sign of groundwater inflow into the lake. Therefore, it is necessary to consider both the groundwater component in the lake’s water management and its vulnerability regarding local and short-term changes in the catchment area.
In South Transdanubia (Hungary), the remarkable geothermal and hydrocarbon resources in the Drava Basin and the hypogene caves at the margin of outcropping carbonate hills were usually investigated separately and their interactions were hitherto neglected. The aim of this study is to give all these groundwater-related resources and phenomena a common framework applying the concept of regional hydraulic continuity, and to complete the regional (i.e., basin-scale) hydraulic assessment of the area based on preproduction archival measured data. Pressure-elevation profiles, tomographic fluid-potential maps and hydraulic cross-sections were constructed to determine the vertical and horizontal fluid-flow conditions. As a result, two kinds of fluid flow systems could be identified. Within the gravitational flow systems, horizontal flow conditions are dominant and the regional flow direction tends toward the S-SE. In deeper basin regions, an overpressured flow system is prevalent, where fluids are driven laterally from the deeper sub-basins towards their margins. Based on the regional-scale evaluation of fluid flow systems, conclusions could be drawn regarding the geothermal and hydrocarbon potential of the area. Additionally, local-scale phenomena could be explained, particularly in the southern foreland of the Villány Hills. Cave formation cannot be related to the present-day flow systems here. In the Harkány area, groundwater chemistry could be explained by fluid contribution from the Drava Basin. A comparison with the marginal Buda Thermal Karst area allows for generalized conclusions regarding the connections between marginal karst reservoirs and the Pannonian Basin.
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