Comparison between a detailed and a simplified integrated model for the assessment of urban drainage environmental impact on a ephemeral river.

The benefit of integrated analysis has been demonstrated in technical literature and it is also required by the EU Water Framework Directive 60/2000, which proposes a water-quality-orientated view of the whole urban drainage system and oversees new ways of assessing its performance. Integrated models, such as any complex modelling approach, often have prohibitive data availability requirements that reduce their applicability. Moreover, widely different approaches can be applied, ranging from simple conceptual models to complex physically based ones. In the present paper, two approaches have been compared using data from an experimental catchment in Bologna ( Italy), which consists of a part of the Bologna sewer network and a reach of the Savena River. The paper shows how river modelling has the most relevant role in conditioning the overall response of the integrated approach. This behaviour is mainly attributable to the ephemeral characteristics of the river determining quality model parameter values much higher than those presented in literature for permanent rivers