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 deter mine whether there was a correlation between water quality and landscape ch aracteristics within three local southern Ontario watersheds. Whole catchme nt and 100 in buffer zone influences on water quality over three seasons we re compared. Chemical fluxes were also calculated and used to compare the l oading of pollutants to downstream environments. Urban land use had the gre atest influence on water quality. The influence of agricultural land use wa s variable and did not agree with the results of other studies. The only na tural landscape variables that appeared to have an influence on water quali ty were slope and silt-clay surficial geology deposit. There was a clear tr end of increased chemical fluxes with increasing urban land use intensity w ithin a watershed. Forested land use appeared important in mitigating water quality degradation. The catchment landscape characteristics appeared to h ave 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. (C) 2 001 Elsevier Science Ltd. All rights reserved.