Monitoring And Modeling the Impact of Urban Areas on Rivers’ Water Quality: Insights from the Sile River’s (Treviso, Italy) Case Study

Diffuse urban pollution, together with plant protection products and fertilizers used in agriculture activities, is a significant factor in altering and compromising receiving water bodies quality status. Changes in the built environment (e.g. imperviousness) and climatic forces (e.g. intense rainfall events after long dry periods) contribute to the increase of combined sewer system (CSS) overflows and of stormwater directly conveyed to water bodies. These discharges are responsible for water quality deterioration, as a result of high concentrations of pathogens, BOD, suspended solids, heavy metals, hydrocarbons and nutrients. Here we present insights from an ongoing project focusing on monitoring and modeling the Sile River, one of the longest European wellspring rivers, and some of its main tributaries crossing the city of Treviso (Figure). To assess the impact of rural/urban pollution discharges on the quality of the previously mentioned water bodies, a monitoring system consisting of 6 discharge measurement stations, 5 sampling systems, together with 3 multiparametric probes, has been realized. Monitoring buoys containing water probes placed at the centre of the Sile River, upstream and downstream the city of Treviso, are used to continuously monitor and quantify rural and urban area’s drainage system outflows, and pollutants trend, during both dry conditions and rainfall events. Water samples collected from automatic samplers at the same point where the water probes are placed, are being analyzed in the lab to check water probes’ data and monitor other pollutants. A rainfall gauge is used to trigger the automatic samplers during rainfall events. Information regarding the urban drainage and sewerage system, together with topographic surveys of the river network crossing the city of Treviso, has been used to develop a 1D hydrodynamic model. This will be calibrated using the data acquired over time from monitoring activities as input to gain an overview of the current status of the Sile River conditions, identify and quantify the main sources of pollution and suggest mitigation strategies. The results from the monitoring activities and the hydrodynamic model will eventually enable to assess the effects of an ongoing project aimed at separating the CSS in the city of Treviso.