A STUDY ON CHARACTERISTICS OF RATER QUALITY AND POLLUTANT LOADS IN THE ASAH I RIVER

Abstract

To clarify the characteristics of water quality and pollutant loads in the Asahi River, Okayama Prefecture, we observed SS (suspended solids), turbidity, COD (chemical oxygen demand), TP (total phosphate), TN (total nitrogen) for over five years and identified hydrologic simulation models of pollutant loads based on the observations.
In the year of lower discharges, the concentrations of TP and TN became higher but the COD values and SS scarcely changed. Therefore, the pollutant loads of COD and SS decreased but TP and TN scarcely changed. The probability distributions of the water quality and pollutant loads observed for a year can be regarded as a log-normal distribution. Identified hydrologic simulation models of pollutant loads estimate well the daily pollutant loads if a yearly average discharge is similar to the year of estimating the model parameters.