Working alongside TRCA, Civica assisted with the updating of the Humber River Hydrologic Model. Existing watershed catchments were converted from the PCSWMM model to VO4. Initial values for key parameters were calculated using various GIS datasets, including soil and land use. A storage-discharge curve was established for Claireville Dam, Lake Wilcox, and other stormwater management facilities. Calibration and validation events were identified, and the baseflow was separated. Civica’s Distributed Rainfall Modelling Technique (DRMT) was used in the calibration, accommodating for spatial variations in precipitation over various catchments within the drainage shed. The model was calibrated using local calibration methods from upstream to downstream. The lower and upper bounds were created for parameter adjustment. The calibration criteria on peak flow and runoff volume were followed in the calibration process. The calibrated model was then used to predict the peak flow from under 2-year to 500-year design storms and the region storm for existing and future conditions.