This research considers the effects of climate change projected by global climate models (GCMs) on irrigated agriculture and water supply in Saskatchewan using 27 different combinations of GCMs, special reports on emissions scenarios (SRES), and time periods (2020s, 2050s, 2080s). Future drought events are extracted from the scenarios using the Standardized Precipitation-Evapotranspiration Index (SPEI) to identify extremely dry conditions, and downscaled to create a daily time-series of temperature and precipitation. The CROPWAT agroclimatic model is used to calculate irrigation water requirements (IWR) under given conditions for two crops commonly grown in rotation, canola and dry beans. This process allows for analysis of current and future water demands for irrigated agriculture. Under future drought conditions, IWR changes are found to be from -10% to 20% relative to the 2001-02 drought event. The resulting water requirement from Lake Diefenbaker, including irrigation expansion to 200 000 ha, is up to 12% of annual supply volume for irrigation.