Hydrogeochemical Changes in Thermal Waters of the Western Pannonian Basin

Due to the continuous thermal water abstractions of the last 50 years, in some sub-regions of the western part of the Pannonian Basin groundwater heads significantly decreased. New aquifer layers started to contribute to thermal wells, which in some cases leads to changes in the hydrogeochemical composition. Mixtures of different chemical types of thermal water are the results of these changes. To characterize the changing process, study of the hydrogeochemical composition of thermal waters was performed, and end-members of the mixing processes were identified. Finally, hydrogeochemical models were developed applying PHREEQC to simulate the processes and follow the ongoing changes.