The environmental impact of agricultural activities on water quality was studied on two sub-watersheds of the L'Assomption river in Quebec, over a 3 year period. The sub-watersheds studied were the Saint Esprit (26.1 km 2) and Desrochers (17.9 km2). Development of a methodology and associated tools for targeting conservation activities and assessing the potential impacts of conservation practices was one of the study's components. A goal of this research was the development of a tool using NPS modelling capability and GIS tools. The ANSWERS 2000 model and SPANS GIS software were selected for integration. / Using the advanced SPANS operation and EASI script language, the ANSWERS 2000 model was integrated into the latest version of SPANS GIS (Explorer ver. 7). Integration of these two software packages provided assistance in creating and handling the extensive input and output data for models, evaluating of model output, and delineating of critical areas. A sensitivity analysis of the ANSWERS model was performed on thirteen parameters to determine their effects on runoff ANSWERS 2000 was found to be most sensitive to depth of soil horizon, silt and clay contents of soil texture, and solar radiation. Four years of runoff predictions by the model were analysed using observed data. Overall, the model was in good agreement with observed runoff in the Saint Esprit watershed, particularly in the years with above the average precipitation. The coefficient of (CP'A) between predicted and observed runoff values was 0.5 and 1.5 for 1994 and 1995, respectively. The model predictions of total cumulative runoff were 66.6% in 1994, 54.9% in 1995, 71.7% in 1996, and 42.4% in 1997, of measured cumulative runoff values.

A research project was undertaken to study the hydrology and water quality of a 26 km$ sp2$ intensive agricultural watershed over an 18 month period. Flow and precipitation data were used to establish hydrologic parameters for the watershed and to empirically model hydrologic processes. Water samples taken from the outlet of the watershed were analyzed for nitrate, phosphate, suspended sediment and atrazine. Water quality data were analyzed to establish temporal trends in pollutant concentration and load in the watercourse. / The measured time of concentration was found to be consistent with a mean of 6.89 hours for the 25 storms profiled. The time to peak was found to vary linearly with storm duration. The event recession constant was measured to be 0.9715. Regression analysis was performed on measured hydrologic properties. The strongest relationship was found between the percentage of rainfall appearing as runoff versus the sum of the 72 hour antecedent rainfall plus the storm rainfall. / Spring snowmelt was identified as a significant period of pollutant material export. All pollutant materials displayed seasonal variability in the export process. Temporal variability accounted for poor correlations between observed hydrologic and water quality parameters in the two seasons for which data were available. / Peak pollutant concentrations were associated with high flow events. Maximum observed concentrations for nitrate, phosphate, suspended sediment and atrazine were 8.6 mg/l, 0.478 mg/l, 0.7 g/l, and 8.06 ug/l respectively.

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