1984 Volume 10 Issue 4 Pages 475-482
Because of attached algae respiration at the river bed, deterioration of water qualities at nighttime occurs in shallow and eutrophic rivers.
A mathematical model is presented to describe the water qualities, such as SS, DOC, DO, total inorganic nitrogen (TIN) and phosphate in such rivers. The model incorporates growth respiration of the attached microbes and accumulation of sediment with the water qualities. After a rainfall, the sediment and the attached microbes are washed out, and they start accumulation or growing in the following days.
The model is compared with observation at the Nogawa River, a tributary of the Tama River, and is found reasonable in simulation of TIN, phosphate and DO concentrations in the river.
Alternative plans to recover water qualities are assessed through simulation by means of the proposed model and it is found that decreasing nutrient inflow is effective in restoring the DO level at night, even 10 days after a rain.