CHANGES IN STREAM WATER QUALITY ACROSS AN URBANIZATION GRADIENT

The coastal plain of the north coast of New York is characterized by numerous small watersheds flowing into Lake Ontario. These watersheds transect a wide range of urban, suburban and rural landscapes. In this study, we investigate five watersheds across an urban-rural gradient to the west of Rochester, NY. The watersheds studied show an exponential increase in impervious surface, a proxy for urbanization, from 1.4% to 21.3% of total area. Stream water samples are analyzed for major cations, sodium, calcium, magnesium and potassium, major anions, chloride, sulfate and carbonate and nutrients, total phosphorus and nitrate. Several variations may be seen across the urbanization gradient that correspond to land uses and anthropogenic factors linked to urbanization or agriculture. The most prominent is the variation in chloride, and, to a somewhat lesser extent, sodium. These ions are found to vary exponentially across the gradient in the same way as impervious surfaces, and are likely linked to the application of road salt in a region that averages approximately 250 cm of snow each winter. Nutrients, which may be linked to agricultural runoff, varied across the urbanization gradient, but not to the degree expected based on land use. This suggests that agricultural runoff is not the only source, with suburban sources also being contributors. Results suggest that water quality issues may be linked to the degree of urbanization, but suburban factors must be considered as modifiers to the continuum.