Prediction of Physical Effect of Seawater-Quality Enhancer Installed near Isahaya Inlet by Laboratory and Numerical Model Tests

There is a discussion on the relation between Isahaya Dyke and the recent environmental change in Ariake Bay, which may devastate the Noni crop and exterminate shellfish. On the other hand, some say that the recent tidal decay in the outer sea is the main cause of the change in tidal current in Ariake Bay. Whatever the cause is, some ways to improve water quality are urgently needed even if they are local and temporal. We proposed a local engineering solution, a kind of seawater-quality enhancer, and simulated numerically and experimentally the diffusion of nutrient-rich water emitted by the apparatus. It is shown that 1-3% of the emitted water keeps to remain on the euphotic layer in Isahaya Inlet for a couple of weeks. This may imply the possibility of improvement of water quality by this engineering countermeasure.