This study presents a model-based analysis of hydrodynamic flow and heat transport in the Budapest Thermal Karst System, including future production scenarios and the impact of newly planned facilities. It emphasizes the need for sustainable management of the region due to overlapping exploration requests—many of which are geographically close to vulnerable karst spring areas—following regulatory changes. In response, the Geological Survey of Supervisory Authority for Regulatory Affairs initiated the Budapest Geothermal Research Programme.
Numerical modelling was conducted using extensive geological and geophysical data, improving the reliability of the geological model for the covered karst aquifer and tectonic features, mainly on the Pest side. A high-resolution 55 km 2D seismic network, gravity data, data from more than 300 deep and approx. 30,000 shallow boreholes, and 2D/3D seismic interpretations contributed to a new 3D geological model. This includes six geological time-horizon models, six geologic formation maps, seven geological-geophysical sections, and a Pre-Cenozoic basement geologic and tectonic map.
The region contains cold and hydrothermal karst systems, including hypogene caves and springs that supply Budapest’s thermal baths. To prevent significant changes in hydraulic heads, temperatures, and water composition due to new geothermal facilities, protective zones must be delineated. A harmonized water chemistry and isotope hydrology database was developed, interpreting main chemical components, discharge temperatures, and isotope data.
Both convective and conductive heat transport were simulated using FEFLOW® software with density-dependent heat transport. A regional (approx. 4477 km²) model with refined mesh around spring areas identified critical karst water supply zones and vulnerable regions through visualized maps, supporting decision-making processes.