Estimation of bay-water retention time

Tokyo Bay has been selected as a study area and the bay was divided into 215 blocks in order to analyze the exchange flow between various blocks by applying a non-linear programming method and to identify the characteristics of flows in the bay in four seasons. The analytical results obtained successfully revealed the occurrence of flow patterns which cannot be expressed by existing simulation analyses, and consequently made it possible to conduct discussion on the environmental values given to each block. Based on the results of flow analysis, particles were thrown into all boxes in the bay and the tracking of these particles was carried out, in an attempt to evaluate the size of bay-water retention time.