Water Quality Simulation Study of a Natural Harbor

Abstract

The modification and application of a hydrodynamic water quality model to predict the water elevations, the depth average velocity components, and the depth mean nitrogen concentrations in Poole Harbor and Holes Bay, in Dorset, England, are described. The main objectives of the study are to ascertain the influence of the nitrogen discharge from Poole Sewage Treatment Works on the corresponding concentrations across the harbor. Comparisons were undertaken, both with and without nitrogen inputs from Poole Sewage Treatment Works, of the concentration distributions of total oxidized nitrogen and ammoniacal nitrogen across the harbor, for inflows from two rivers and three sewage treatment works. Limited field measurements were available of velocities and nitrogen concentrations, allowing a check on the accuracy of the model predictions. A number of difficulties had to be overcome in the hydrodynamic modeling, including treatment of the open boundary conditions, representation of the advective terms, with particular reference to the narrow harbor entrance, and simulation of extensive flooding and drying of shallow regions throughout the tidal cycle.