Urbanization of rural watersheds in the region of Waterloo : implications for water quality

Currently, the Regional Municipality of Waterloo (RMOW), Canada, derives about 90% of its water supply from groundwater. During the last five years, the population has grown by 8% per year, with development occurring on formerly agricultural land. Over the last 10 years, geochemical sampling in production, domestic, and monitoring wells across the RMOW, focusing on nitrate and chloride, has provided a background data set to evaluate changes to groundwater quality as development encroaches rural watersheds. Samples were taken in rural, urban, and rural residential (areas with relatively dense concentrations of both individual domestic wells and septic systems) environments. Typically, chloride levels are highest in urban areas and along highways in rural areas; nitrate levels are highest in rural and rural residential areas. Results in some recently urbanized sections indicate a reduction in nitrate concentrations, with little impact yet observed from road salt but additional sampling is needed to assess long-term trends.