Abstract
In this paper, the statistical properties of surface water quality in the Asahi River estuary are discussed based on the frequency distributions and the power spectra. The concentrations of COD(Mn), SS, chlorine ion and chlorophyll-a are mainly dealt with.
The frequency distributions of COD(Mn) and SS during several tidal cycles are in accord with normal distributions and logarithmic normal distributions, respectively.
Not only the tide but also the seiche or the secondary undulation affects the variations of the surface water quality. In the Asahi River estuary, the tide has the greatest effect on each water quality item.
The strength and periods of the variations in the water quality items are somewhat different from each other.
