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Watershed modeling in the digital world is a valuable environmental management tool. Environmental models play a critical role in our society and in protecting our environment. It brings science and policy makers together. Resolution of dataset plays a critical role in model prediction. This study addresses the effects of varying resolutions in the SWAT (Soil and Water Assessment Tool) model when integrated with a GIS package, ArcView, for a given sub-basin. SWAT is a physically based model capable of predicting long-term impacts of land management practices on water, sediment and agricultural chemicals in a complex watershed with diverse soils and landuses. SWAT utilizes actual data from the national weather service in its modeling process. Objectives of this study were three fold i) to determine the effects of varying resolutions of spatial data viz. 30 m and 250m on the model output, ii) to determine effects of varying spatial resolution on a temporal scale and iii) to conduct identical experiments within two different watersheds to analyze the spatial trends. Data layers used with GIS were soils (NRCS- STATSGO and NRCS - SSURGO), Landuse (USGS-DLG and Landsat TM5) and Hydrologic Unit Catalogs (USGS-HUCs). Climatic data used in the study was obtained from daily National Weather Stations provided by a BASINS Database. This allowed for us to add a temporal element into the study. Results are reflective of the internal parameters of the SWAT model and are reported through ASCII outputs. In general 250m and 30m resolution data sets consistently showed different results. The nature of spatial representation e.g. the nature of rich files also impacts the effects of resolution. This study demonstrates that attention needs to be given to the selection of the resolutions of data while modeling with SWAT.