The interactions between groundwater and contaminated surface water may influence on groundwater contamination. In urban environments, the aquifer located around a stream often becomes variably saturated due to variation of recharge rates, transpiration, domestic pumping and seepage into some underground facilities. The variation of aquifer saturation may change the degree of groundwater-surface water interactions. Through stream depletion, contaminants dissolved in a stream migrate into adjacent groundwater systems, mix with groundwater, and deteriorates groundwater quality. The extent of associated groundwater contamination is determined by coupled flow and transport modeling. For this study, numerical modeling is performed with a computer code for coupled flow and transport simulations in variably saturated aquifers, MODFLOW-SURFACT (HydroGeoLogic, Inc., 1996). Simulation results allow the spatial delineation of areas where groundwater-surface water interaction occurs. The extent of simulated groundwater contamination was shown to be more significant under moderately and highly saturated conditions than slightly saturated conditions. Simulations revealed that groundwater contamination under slightly saturated conditions is as significant as moderately or highly saturated conditions in a long term development of stream depletion. This study presents a preliminary base for management and assessment of water resources in the variably saturated groundwater system adjacent to an urban stream.