5. Mineral and geothermal waters of the Podunajska Rovina Flat

In the Podunajska rovina Flat (Danubian Flat) there are mineral water sources on its western edge in Svaty Jur. These sources contain water of chemical type Na-Cl-HCO₃ with mineralization of 867.9 mg · l^-1 and H₂S content of 2.82 mg · l^-1, which was used in the past for spa treatment. Geothermal waters of the Danubian Flat are widespread mainly in the area of the Central Depression of the Danube Basin and the Dubnik Depression, where the sediments of the Neogene with predominant intergranular permeability above the fissure are found. In the Central Depression of the Danube Basin, the geothermal water reaches in the depth range of 1,050 - 2,500 m a temperature of 42 - 91 grad C, a mineralization of 1.5 - 8.3 g · l^-1 and a chemical type of water is Na-HCO₃ , Na-HCO₃-Cl to Na-Cl-HCO₃ . In the eastern part of the Danubian Flat, the geothermal water of the Dubnik Depression has a temperature of 50 grad C, a mineralization of 5.3 g · l^-1 and a chemical type of Na-Cl at a depth of 975 - 1,321 m. Geothermal water is found in the Mesozoic aquifers with karst-fissure permeability in the Komarno Marginal Block. In the area of Komarno the geothermal water in the depth interval of 1,140 - 1,900 m reaches a temperature of 42 - 64 grad C, a mineralization of 2.2 - 3.1 g · l^-1 and a chemical type ranges from Na-Ca-Mg-SO₄ · HCO₃ -Cl, Ca-Na-Mg-SO₄-Cl-HCO₃ to Ca-Na-Mg-SO₄-Cl. The vast majority of geothermal wells in the Danubian Flat are used for recreation and in agriculture and, to a lesser extent, for heating. (authors)