1.1 Introduction Groundwater is in contact with surface water. However, traditionally, groundwater and surface water have been considered separate water resources (Winter, 1998). For this reason, managing groundwater and surface water resources carries the risk of allocating the same water twice in the water balance (Geosciences Australia, 2013). Not only are two resources in close contact, but they interact. Therefore, Winter (1998) considered groundwater and surface water as a single resource. Surface water is commonly connected hydraulically to groundwater, but the interactions are difficult to observe and measure (Winter, 1998). The interaction depends on understanding the effects of the topography, geology, and climate of the groundwater flow system (Toth, 1970). In addition to this, biotic factors are also responsible for the interaction (Sophocleous, 2002). Due to the complexity, the study of the interaction of groundwater and surface water has been studied for more than a century. The study was initiated using the analytical method developed by Boussinesq (1877). Even today, the study of groundwater-surface water interaction is the most common research topic studying stream-aquifer interaction (Winter, 1995). Despite the difficulties in directly observing and measuring interactions, several techniques have been developed to understand interaction. For example, measuring hydraulic head, water temperature in the aquifer, etc. The study of groundwater-surface water interaction is not limited to methods relating to the physical properties of the aquifer but is rather extended to chemical and numerical methods and some have even considered a statistical approach to quantify the interaction. Statistical methods such as principal component analysis (...... half of the paper ...... and additional numerical methods are obtained for the numerical model which improves the model result compared to the one built with non-specific parameters of the site (Unthank, 2013). Numerical groundwater model is constructed, calibrated and verified with field data, then model simulation is conducted for different scenarios. Finally, a sensitivity analysis is performed to identify the field parameters that most influence these systems The region's water utilities gain information about well-aquifer interaction, so they could defend themselves with scientific information about flow directions and recharge sources to be able to respond to public demands and react to incidents of suspected contamination. The results of the study will be useful in identifying potential threats to water security and in planning future expansion of wells.