The model is based upon numerical integration of the flow equations which simulate the water movements caused by tides, wind and pressure differences, and upon numerical integration of the advective diffusion equation representing the movements of salt and temperature. It neglects vertical accelerations, but not vertical velocities, and includes an approximation for the subgridscale effects by introduction of mass and momentum exchange coefficients. These coefficients are dependent upon the Richardson number and vertical velocity gradients. The computation method is tested on an estuary and the results of the simulations are presented in graph form. 14 pp. Ref.