Development of Quick Reference Tables of Flowing Prediction of Substances in River Systems in Japan－An Example of Chloroform in the Tama, Yodo, and Nikko River Systems－

Abstract

For use in countermeasures to chemical spill accidents in river basins for national and local governments, we developed quick reference tables for flowing prediction of chemical concentrations. Accident points were set up to reflect the differences in catchment area and gradient in three river systems of various basin sizes, and simulations were conducted for sunny, rainy, and severe rainfall conditions using the AIST–SHANEL model with a 1-minute time resolution. Using these simulation results, we made quick reference tables of the concentrations of substances relative to the distance and time from the accident. All the tables were summarized in terms of catchment area and gradient and indicated that the chemical flow downstream time tends to be shorter when the gradient is larger and the peak concentration of a chemical substance tends to be lower when the catchment area is larger owing to dilution effects. We will develop quick reference tables of chemical concentrations for more river systems and chemical substances with different physical properties, which will enable us to devise more efficient countermeasures to chemical spill accidents occurring in any river system in Japan.