The importance of drinking water around the world is getting bigger every day and so does the importance of water sources connected to it. Aquifer is one of the sources that is capable of holding enormous quantities of groundwater. The underground surface of groundwater is constantly changing due to the effect of many different conditions it is exposed to in certain period of time. The effect of three different scenarios on the groundwater surface in an aquifer in Stahovica will be studied in this Graduation Thesis. At first a hydraulic model of river Kamniška Bistrica that represents hydraulic boundary will be made with a program HEC – RAS. Model of the aquifer and the simulation of groundwater flow under the influence of river, pumping well and precipitation with surrounding waters will be made with the help of FREEWAT. The results of the simulation will be evaluated and analyzed.