Water management activities are currently predicated on the assumption of a stationary climate, despite the reality of climate change. Hydrologic impacts of climate change for three sub-watersheds north of Toronto for 2041-70 were investigated using the Precipitation-Runoff Modeling System to model six GCM projections from each of RCP 2.6, RCP 4.5, and RCP 8.5. Annual groundwater recharge, evapotranspiration, and the 7Q20 low streamflow statistic were projected to change from 1976-2005 conditions by -2.2% to +20.5%, +0.9% to +14.4%, and -25.5% to +9.8%, respectively. Seasonal shifts included an earlier date of peak streamflow for the majority of simulations and a +14.0% to +103.9% increase in winter recharge. A steady-state MODFLOW model was employed as a preliminary assessment into the effects of climate change on Source Water Protection outputs. The results of this research further the understanding of climate change impacts on human and ecological systems in southern Ontario.