Impact of river discharge on surface water variability in Amagasaki port, Japan

Amagasaki port is located closed-off section of the Osaka bay, Japan. On the side of the vertical seawalls in the port, a large amount of mussel attached to the objects and drop off to the sea bottom every summer and the mussel drop-off is a pollution load for sea bottom environment. The mussel drop-off is often occurred at the time of sudden water quality change, especially temperature and salinity. Therefore, this study focuses on the period characteristic of surfer salinity in Amagasaki port, wavelet analysis attempt for observed salinity to clarify the occurrence time of the sudden water quality change. Hydrodynamics at the time of river runoff are analyzed by a three-dimensional baroclinic flow model. This study clarified that the occurrence of river runoff was indicated by wavelet analysis at Amagasaki port and the river discharge from Yodo River mainly affected to the sudden change of surface salinity at the sea area, which is a semi-enclosed area and surrounded by reclaimed land.