A mass conservative 3-D numerical model for predicting solute ̄uxes in estuarine waters

A re®ned three-dimensional layer-integrated model to predict accurately salt and cohesive sediment transport in estuarine waters is described herein. A splitting algorithm has been used to split the three-dimensional transport equation into a horizontal twodimensional equation and a vertical one-dimensional equation due to the di€erent length scales. An additional source term associated with the layer average of the free-surface ̄ow is introduced in the conservative form of the layer-integrated pollutant transport equation. The one-dimensional QUICKEST scheme has been extended to two dimensions and included in the layer-integrated advective±di€usion equation. A modi®ed one-dimensional ULTIMATE algorithm has also been added to avoid unphysical numerical oscillations. Numerical tests for discontinuities have been carried out to study the performance of the ULTIMATE QUICKEST scheme used in the present model. The model has also been used to simulate solute transport in an idealized harbor. It has been found that the additional source term was crucial for the mass conservation of pollutant. Finally the re®ned model has been applied to simulate salt and cohesive sediment transport in the Humber Estuary, UK. Good agreement has been obtained with the ®eld measured data. Ó 2000 Elsevier Science Ltd. All rights reserved.