ABSTRACT: There has been increasing recent use of heat pump technology to heat and cool buildings in Bratislava and its surrounds. Groundwater is the heat source most often used in this technology and important aquifer hydraulic and thermal parameters must be known for effective use of this source. Combined data from numerical groundwater flow modelling and aquifer heat transfer enables prediction of the temporal development of the pumped groundwater temperature. The calculation results allow optimisation of the following well technology; the number of wells, their spatial distribution and pumped and recharge quantities. The TOUGH2 program was used here to model temperature development in pumped and recharge water in the town Ivanka pri Dunaji. Numerical modelling identified the physical processes required for the appropriate calculations, so that the numerical simulation results are sufficiently accurate to approximate the actual observed situation. Our paper confirms that TOUGH2 is a suitable tool for calculating study area changes in groundwater temperature resulting from heat pump operation.