This research project demonstrates the interest of applying a spatial downscaling technique to ensemble rainfall forecasts from Environment Canada's Global Environmental Multiscale model (2009 version), and proposes innovative and effective real-time control strategies (sometimes relying on the downscaled forecasts) of an urban stormwater detention pond. Ensemble rainfall forecasts are indeed valuable in the field of water management for their explicit and dynamic assessment of the associated uncertainty. However, for hydrological forecasting, their low resolution currently limits their use to large watersheds. Therefore, this research project explores rendering the forecasts more appropriate for small catchments by bringing them from a 100 by 70-km resolution down to 6 by 4 km, using the method of Perica and Foufoula-Georgiou (1996). The downscaled forecasts are evaluated in three ways: comparing the rainfall amounts to observations, evaluating Hydrologic forecasts resulting from their use, and by assessing their interest when used for decision making, in this case by demonstrating that a stormwater detention pond's efficiency is improved when using the forecast information.