This project resulted in the development of a hydrological model for storm runoff events for small (20 km ) agricultural watersheds. The model attributes surface runoff amounts to specific land surfaces within the watershed. The model was developed for and applied to the watersheds of Canagagigue Creek (AG-4), Holiday Creek (AG-5) and East Canagagigue Creek. The name GAWSER (Guelph Agricultural Watershed Storm Event Runoff) was given to the model. A users manual has been published (Ghate and Whiteley, 1977). The storm-by-storm areal distribution of surface runoff as determined from the model provides information about the frequency of runoff and the location of areas most subject to erosion. Combining this information with the results of related projects at the University of Guelph which deal with erosion amounts, the nutrient content of sediment and the fate of suspended sediment in the stream it is possible to specify which watershed areas are most productive of sediment and under what storm conditions sediment will be produced. The reasons for seasonal variation in the distribution of sediment production is revealed through analysis of storms from different seasons. From this information the seriousness of surface runoff as a source of pollution can be assessed. Potential remedial measures can be evaluated to establish their appropriateness in relation to the source areas producing the largest and most frequent surface runoff amounts.