The residence time of the water in Lago Maggiore (N. Italy): first results from an Eulerian-Lagrangian approach

The paper describes a numerical study for estimating the spatial distribution of the hydraulic residence time in Lago Maggiore. A 3D eulerian time-dependent CFD code has been applied under real conditions, taking into account the effects of the monthly mean values of the mass flow rates and temperatures of all the tributaries, mass flow rate of the Ticino effluent and meteorological, hydrogeological and limnological parameters available from the rich data-base of CNR-ISE (Pallanza). The velocity distributions from these simulations were used to compute the paths of a number of massless markers with different initial positions and so evaluate their residence times within the lake. The results presented here follow a two-year simulation and show encouraging agreement with the mechanisms of mixing and of deep water oxygenation revealed by recent limnological studies carried out at CNR-ISE. Further studies are in progress to improve the results and extend the research over a time period of at least four years.