Global sensitivity analysis in integrated water quality modelling: an application to a real case study

The increasing sensitivity towards water quality environmental issues led to the setting up of water quality integrated modelling approaches and the definition of water quality criteria that better represent the receiving water body quality status. More specifically, compared to the past, the tendency today is to design and manage the whole integrated urban drainage system, i.e. , wastewater treatment plant and receiving water body (RWB) considering each component not separately but jointly. Despite the advantages of a holistic approach for the assessment of the RWB quality state there are some limits that may prevent a straightforward application. Indeed, integrated models are generally characterized by a high level of model complexity which increases rapidly involving tenth of parameters and requiring large measurements databases for calibration. In this context sensitivity analysis represents a very powerful tool, as it is able to provide information about how the variation in the output of the model can be apportioned to the variation of the input factors and may help in reducing model complexity. The paper presents a study on an integrated urban water quality system applying the global sensitivity analysis (GSA). Specifically, a home-made integrated model previously developed has been employed to a real case study. GSA allowed to identify the most influential model parameters thus reducing model complexity and enabling a better assessment of the RWB quality state.