Numerical Simulation of water mixing and renewal in the Barcelona harbour area.

Quantification of water quality in harbours is an important issue. Harbours are typically characterized by the presence of complex coastline and anthropogenic structures and reduced circulation. Often, microbe contamination from urban sources and over-enrichment by nutrients from agricultural sources is present in the harbour. Moreover, the presence of ships, combined with the water shallowness, may produce resuspension of polluted sediments degrading even more the quality of water. The combined effects may produce biological transformations and create a source of very polluted waters, that, once moved out of the harbour may affect the water quality of the surrounding sites. On the other hand, the use of prognostic models to evaluate water renewal and quality in these sites is complicated by the geometric complexities and by the interaction between different physical processes. For example the presence of submerged jets interacting with the picnocline and geometrical features, makes standard prognostic models based on simple closure schemes for turbulent mixing of momentum temperature and scalars (pollutants) hardly applicable. In the present joint research project we intend to analyze water quality under typical external forcing in the harbour of Barcelona (ES). We use a state-of-art numerical model (LES-COAST) recently developed for the analysis of water mixing in semi-closed or closed bays (Roman et al., 2011).