Abstract
The Ariake Sea is a typical semi-closed water body surrounded by lowlands. The area of tidal flat accounts for 40% of all those in Japan and both the tidal flat and the sea has high fishery production. In recent decades, there are progressive developments such as new harbor, land reclamation and enclosure of a bay. Recent fishery production is abruptly decreasing, and thus it is necessary to investigate the environmental status. In this study, after developing a two-dimensional water quality model in the Ariake Sea, the characteristics of water quality through the observed data and simulation results were examined. As a result, it was indicated that the tidal flat plays an important role especially in nutrients. The discharged pollutant loads affect the concentrations of COD in summer. However, these high concentrations occur for a short period before being flushed out to the open sea.
