PREDICTION OF QUALITATIVE CHANGE AND ITS ESTIMATION IN THE REGULATION POND AT ISAHAYA BAY

Abstract

A circulation model of nutrients has been developed in order to investigate the qualitative changes of water in the flood regulation pond that is newly appeared at Isahaya Bay through constructing the sea dyke. In this model, the mass balance of phosphorus is designed regarding to the interaction between aquatic system and sedimentary system, and temporal changes of pollutant load from rivers are considered. Calculated results show that phosphorus increases due to the pollutant loads through river after the enclosure of the bay. Furthermore, concentration of phosphorus rapidly varies with the increment of desorption caused by inflow of flood. Annual average of the concentration of phosphorus almost reaches constant value in two years, and the both the mean concentration and the amount of phosphorus accumulated in the pond are strongly affected by an annual rainfall.