Utilization of riverbank filtrate water for heating and cooling of buildings can reduce installation costs considerably by using the existing operating facilities for water purification and supply. Changwon city, Korea, has been using riverbank filtrate water for the indoor air-conditioning at its Daesan water treatment plant since 2006. In this method, the most important factor for determining the efficiency of heating and cooling is the temperature of the filtrate water. Numerical simulation of the temperature profile of riverbank filtrate water in the Daesan plant using HydroGeoSphere shows that the primary factor in determining filtrate water temperature is the pumping rate. This is because of the proportion of the river-originated water which increases with pumping rate. It also shows that maintaining the facility operation at the current pumping rate for the next 30 years will not cause any significant change in the water temperature. However, following the new city plan to install an additional 37 wells with a 6 times greater pumping rate than the current system might cause about 2 degrees C decrease in filtrate water temperature 10 years after the extension. This temperature drop will result in a significant change from the original design in heating and cooling performance. (C) 2010 Elsevier Ltd. All rights reserved.