Hydrodynamic and nutrient modeling in a Mediterranean coastal lagoon.

The USEPA WASP5 modeling system was applied to simulate and evaluate the relationships between external and internal nutrient loadings and water quality of Vistonis lagoon, North Greece for a 2-year time period. The hydrodynamic model DYNHYD5 was calibrated to estimate daily lagoon water level. The water quality models TOXI5 and EUTRO5 were calibrated and verified using meteorological data from a station near the lagoon, and field data (salinity, dissolved oxygen, nutrients and chlorophyll-a concentrations) from seven stations located in the lagoon, for the time period April 1998 to May 1999. Predicted by the model salinity, dissolved oxygen, total phosphorus, total inorganic nitrogen and chlorophyll-a were plotted against observed values and showed good agreement. Model performance was evaluated using scattergrams of predicted versus observed values and the Kolmogorov-Smirnov two-sample goodness-of-fit test at p < 0.05. Sediment sources of nitrogen and phosphorus were important to achieve a successful model calibration. The validated model was also used to test the effectiveness of alternative management scenarios in relation to improvement of the trophic state of the lagoon.