Water management activities are currently predicated on the assumption of a stationary climate. This research investigated the range of hydrologic impacts resulting from the most recent climate change projections for an area within the Lake Simcoe watershed for 2041-70. Eighteen general circulation models (GCMs) were selected to represent the mean and extreme projections of three greenhouse gas emission scenarios (RCP 2.6, RCP 4.5, and RCP 8.5). Changes in average annual temperature and precipitation ranged from +1 to +5 °C and -2% to +19%, respectively. Hydrologic modelling found that annual recharge rates deviated from the historical record by -2.2% to +20.5%, evapotranspiration increases ranged from +0.9% to +14.4% and the 7Q20 decreased for most scenarios. The results of this research further understanding of projected climate change impacts in southern Ontario, which include higher winter recharge rates, higher evapotranspiration rates, earlier peak streamflow, and a decrease in the 7Q20.