Depth-averaged, two-dimensional eutrophication modelling for Tolo Harbour, Hong Kong

A depth-averaged 2-D finite-difference numerical modelling for eutrophication in coastal waters, based upon a numerically generated boundary-fitted orthogonal curvilinear grid system, is developed. The present eutrophication model is run simultaneously with a hydrodynamic model to capture advection and diffusion due to tidal flow. A grid "block" technique is employed to handle the areas submerged intermittently. The model simulates the transport and transformation of up to nine water quality constituents associated with eutrophication in the waters. Some kinetic coefficients are calibrated with the measured data in Tolo Harbour, Hong Kong. Descriptive inputs for Sediment Oxygen Demand (SOD) and nutrient releases from sediment, based on relevant in situ sampling analysis, are used. The computed results are compared with other long-term field data in Tolo Harbour. It shows that the computational results by the present model agree with the field data well, i.e., the present model could reasonably describe the depth-averaged algal growth dynamics and water quality time-variations in Tolo Harbour.