Shallow geothermal energy has been estimated to have an excellent applicability in Korea, and its applications for space heating and cooling have steadily increased in recent years. Such application as ground source heat pump (GSHP) system can be classified into closed- and open-loop. In recent years, studies have been conducted to minimize the environmental impacts resulting from pumping/injection and to enhance the efficiency of groundwater heat pump (GWHP) system that is the open-loop system. These studies suggest that the characteristics of the aquifer have a significant role in designing efficient GWHP systems. This study considers various hydrogeological properties of Korea. An open-source numerical code called TRS was used for preliminary and sensitivity analyses of GWHP systems. In the analyses, arrival time when thermal plume arrives at pumping well and temperature change at pumping well were observed with different pumping/injection rates, hydraulic gradient, and well separation. Thus, we derived adequate well arrangement for efficient GWHP operation.