Behaviour analysis of deep ocean water discharged in a small port

The deep ocean water (DOW) which has low temperature and high nutrients will be effective for regenerating subpolar/temperate seaweed bed and aquaculture of those seaweeds. In the present study, a semi-enclosed small fishing port near the pumping facility of DOW in Kume Island of Okinawa in Japan is chosen for the field experiment of seaweed bed development, because it could be possible to prevent the discharged DOW from diffusing rapidly. Additionally, in order to keep low temperature and high nutrient concentration of DOW more effectively, a box-shaped pool is installed on the bottom of the port in which DOW is discharged. In order to investigate the effectiveness of the pool for retaining DOW, hydraulic model experiments are carried out with a 1/10 scale model during the planning phase of the field experiment. In the field experiment, water temperature and nutrients concentrations in and out of the pools, and current velocity just above the top of the pool have been measured to detect the behaviour of discharged DOW. The numerical simulation model was also developed to predict the behaviour of discharged DOW in the port. Through the field experiment and the numerical simulation, it is clarified that the box-shaped pool installed on the bottom of the port is quite effective to retain the discharged DOW. It is also found that DOW hardly affect surrounding environment since it will rapidly mix with ambient seawater when it goes out of the pool.