The potentially large implications on quantities and timing on river flows arising from climate change, are being assessed very carefully in Canada, due to their huge implications.As an indication,analyses of historical hydrometric data in Ontario, Canada indicate an increasing trend in winter streamflows.This effect may be due to increasing winter air temperatures over the latter half of the twentieth century which have resulted in reduced snow accumulation on the ground and accelerated snowmelt events.The consequence is that spring snowmelt is occurring several weeks earlier in February instead of March, which has significant implications to reservoir operations.Further, to examine future conditions, projected future climate data using the second generation Coupled Global Climate Model (CGCM2) downscaled using the Change Factor method for the headwaters of the Mississippi River (Ontario) watershed are assessed, and the calibration of an hydrologic model is used to assess future streamflow conditions.The results show a gradual change per decade of 1% increase in total precipitation, 2% increase in rainfall, 6.7% decrease in snowfall, 2.3% increase in potential evapotranspiration, 1.2% decrease in soil moisture, 14.4% increase in water deficit, 5% increase in streamflow during winter months and 2.5% decrease in streamflow during the summer months.These results indicate that reservoir management operations for this watershed require revision.