In the Greater Toronto Area (GTA), there have been drastic changes to local watersheds as urban areas sprawl over surrounding rural areas. It is necessary to understand the water balance of a watershed in order to develop and implement a watershed plan. In an urbanized watershed, the run-off rate and volume will increase. While Duffins Creek may be one of the healthiest watersheds in the GTA, it is also one that is producing the most concern for the Toronto and Region Conservation Authority where findings suggested that proposed urbanization will impact the water quality and quantity. This [thesis] research has three objectives: to develop a modelling methodology that integrates GIS and hydrologic models in a water balance analysis using as case study the Reesor Creek watershed; to calibrate the models by observing how differing techniques discretize both the landscape and incoming precipitation; and to observe the effects of spatially distributed rainfall measurements and their affects on the three modelling approaches.