The dynamic model Seemod applied to the Southern Basin of Lake Lugano

The dynamic model Seemod developed at the EAWAG (Imboden and Gächter, 1978) and modified by Bührer (Ambühl and Bührer, 1984), was adapted to the South Basin of the Lake of Lugano (Lago di Lugano). The model can predict the evolution of the state of the lake, described by the concentrations of dissolved phosphorus, dissolved oxygen particulate phosphorus and organic particulate carbon, in function of phosphorus load and taking into account physical and biochemical initial- and boundary conditions. The model parameters were chosen through measurements and calibrations by short runs. A 10-year-long simulation was done, starting from the data of 1980, and its results agree quite well with the measurements. Then some 15-year-long simulations were done, which corresponded to different scenarios related to a progressive linking up of sewage systems to water treatment plants. The model predicts that a satisfactory water quality level can only be reached by reducing the total phosphorus input to less than 25 t/a.