Modelling and assessment of water quality indicators in a semi-enclosed shallow bay

Bohai Bay is a large, semi-enclosed shallow water basin located along the western region of e Bohai Sea in the north-eastern part of China. As a result of rapid economic development in the surrounding coastal hinterland, the water quality characteristics within Bohai Bay have been of growing concern in recent years. Details are given herein of an aquatic environmental assessment study undertaken to investigate the hydrodynamic and transport processes within the Bay using an integrated numerical modelling approach and field measurements. 3-D numerical model was used to simulate the tide flow and 2-D model was deployed with moving boundary to simulate the water quality. In order to improve on the water quality characteristics in the near-shore coastal zone, an ocean disposal plan was also considered, with various scenarios being simulated using the 2-D model. From an analysis of data collected from the field measurements, it was found that both chemical and phytoplankton indicators were important in the assessment of the overall water quality of the Bay. The occurrence of red tides was also found to be closely linked to the composition of phytoplankton community.