Assessing Quantity and Quality of Water in Urban Rivers for a Sustainable Interaction between Natural and Built Environment

In this work we present the first results of an ongoing project started in 2020 that aims at assessing the impact of anthropic activities on river water quality through both monitoring activities and modeling. The city of Treviso (Italy) and the Sile River are considered as case study. A model has been developed integrating the natural river system (Sile River and tributaries) crossing the historical centre of Treviso and the combined sewer system (CSS) that collect urban water. In the model, both quantity and quality aspects can be considered. Between 2022 and 2023, monitoring stations have been installed in six positions along the Sile River and tributaries, upstream and downstream the downtown to quantify the urban contributes. All stations are equipped with two radar sensors that continuously measure water level and surface velocity to obtain discharge values calibrated by acoustic doppler current profiler surveys. Three out of six stations are also equipped with a multiparametric water probe (Manta 35+ by Eureka®) and an automated refrigerated water sampler (AS950 by HACH®) to characterize the quality of water in the rivers. In two positions, probes are inserted into monitoring buoys (CB40 of NexSens®) anchored to a properly designed concrete block that sustains the filter at the end of the intake tubing connected with the water sampler. The probes continuously monitor seven parameters: temperature, pH, oxidation reduction potential, depth, conductivity, dissolved oxygen, turbidity, ammonium, and nitrate. The water collected by the samplers is analysed in the lab to check and eventually correct drifts of probe values. After a first phase useful to check probe values and define water quality variability, samples will be collected during intense rainfall events to assess the impact of stormwater on river water quality. Data obtained from the monitoring stations are analyzed through the coupled hydrodynamic and quality model to obtain a first assessment of the current status of the Sile River, and to identify the main sources of pollution with the aim of suggesting mitigation strategies.