Two-layered, 2D unsteady eutrophication model in boundary-fitted coordinate system

The decline of water quality in Tolo Harbour in recent years is an example of eutrophication. This paper delineates a robust unsteady two-layered, 2D finite difference numerical model for eutrophication in coastal waters. The modelling is based upon the numerically generated boundary-fitted orthogonal curvilinear grid system and integrated with a hydrodynamic model. It simulates the transport and transformation of nine water quality constituents associated with eutrophication in the waters, i.e. three organic parameters (carbon, nitrogen and phosphorus), four inorganic parameters (dissolved oxygen, ammonia, nitrite+nitrate and orthophosphate), and two biological constituents (phytoplankton and zooplankton). Key kinetic coefficients are calibrated with the field data. The hydrodynamic, pollution source and solar radiation data in the model are real-time simulated. The computational results show that the present model mimic the stratification tendency for eutrophication phenomena during summer time in the Tolo Harbour successfully. The model running time for the long-term simulation is not excessive and it can be run on a microcomputer.