Searching a compromise between ecological quality targets, social and ecosystem costs for Heavily Modified Water Bodies (HMWBs): the Lambro-Seveso-Olona system case study

The Lambro-Seveso-Olona system is one of the most densely populated watershed in Europe The average population density in this area is higher than 1000 inhabitants/km2. These population densities are among the highest in Italy and Europe. Industry is also highly developed in this basin, chemical, textile, paper, pulp and food industries being the most important ones. Although at present the Lambro-Seveso-Olona system does not receive any more the untreated wastewaters of the Milan urban area, treated wastewaters constitute about half of the streamflow. Biotic communities in this river have a long history of poor quality status, having suffered great damage due to domestic and industrial discharges. The Lambro-Seveso-Olona system constitutes also the most polluted tributary of the Po river, the largest Italian river. Aim of this study is to analyse through a modeling exercise the restoration possibilities of the Lambro-Seveso-Olona system, investigating both the source apportionment of the macropollutants and the discharge limits that should be set to achieve the good quality status. Following modeling response, the technical and economic feasibility of the requested discharge limits will be evaluated.