Buffer zone versus whole catchment approaches to studying land use impact on river water quality.

Secondary databases, GIS and multivariate analysis tools were used to determine whether there was a correlation between water quality and landscape characteristics within three local southern Ontario watersheds. Whole catchment and 100 m buffer zone influences on water quality over three seasons were compared. Chemical fluxes were also calculated and used to compare the loading of pollutants to downstream environments. Urban land use had the greatest influence on water quality. The influence of agricultural land use was variable and did not agree with the results of other studies. The only natural landscape variables that appeared to have an influence on water quality were slope and silt-clay surficial geology deposit. There was a clear trend of increased chemical fluxes with increasing urban land use intensity within a watershed. Forested land use appeared important in mitigating water quality degradation. The catchment landscape characteristics appeared to have slightly greater influence on water quality than the 100 m buffer. The results of this study may have been influenced by the scale and accuracy of databases used. The secondary data were useful in determining major trends in water quality and possible non-point origins of surface water pollution, and in identifying areas that are in need of further investigation.