An investigation of the thermal waters in the Ústí nad Labem area in the northeastern part of the Eger Rift has been carried out, with the principal objective of determining their origin. Waters from geothermal reservoirs in the aquifers of the Bohemian Cretaceous Basin (BCB) from depths of 240 to 616 m are exploited here.
For comparison, thermal waters of the adjacent Teplice Spa area were also incorporated into the study. Results based on water chemistry and isotope methods indicate mixing of groundwater from aquifers of the BCB with groundwater derived from underlying crystalline rocks of the Erzgebirge Mts.