Analsis on Environmental Hydraulic Dynamics depended on Mixing and Diffusion Phenomenon in Tidal River and Shallow Water

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The optimum management for water qualities within river and inland water were researched by the field observations and numerical models.(1). Daily change of water quality (DO,EC,pH,ORP,T-P,POィイD24ィエD2-P,T-N) was investigated by two kinds of measurements at two stations, which were at the up- and down-stream on the gravel river-bed in the Lower Ishite. The results of 1-week-long observations at three times revealed the daily change due to the daily life cycle. Two peaks of water discharge, occurred at around mid-day and mid-night, were observed as a day cycle. The change of water temperature, DO and pH have 24-hour cycles with one peak. Apparent change in the DO and pH of two stations were considered to be due to the effect of the gravel river-bed. The attached algae on the gravel river-bed seem to produce oxygen during the daytime and then DO increases. Moreover, it was found that the gravel bed decreases the amount of T-P. (2). Residual currents in Kii Channel and Ise Bay using a robust diagnostic numerical model were investigated. The computed currents agree well with the data measured by ADCP quantitatively. The residual currents in both Kii Channel and Ise Bay were quasi-geostrophic, which play an important role on the transport of substance in each shallow water. Another study of the distribution changes of phytoplankton and nutrient induced by a submerged structure in vertically two-dimensional steady flow field. A numerical model had the domain (2,000m × 50.5m) and an inflow velocities (0.1 - 0.5m/s). Biological and the advective diffusion domain were in the surface and the bottom layer respectively. (3). Field studies on the polluted water and the sediments under fishery nursery in the Kitanada Bay were carried out by using the water multi-qualities instrument. The deficit oxygen water in bottom circumstance were clarified. Experimental study searched the relationship between ORP-model and the measure of oxygen demand on the surface of bottom material.