Abstract
The simulation model of water quality in a river is prepared for the purpose of analyzing the pollution load to the receiving water body such as a lake. Sedimentation of suspended solid, growth and respiration of attached biomass on the river bed and denitrification by attached biofilm are taken into account in the model. It describes the change of SS, DOC, NH4 and NO3 concentration in the flowing water.
The capacity of selfpurification is expressed using pollution load ratio of output to that of input in the river. The model also includes accumulation and degradation of pollutant on the river bed and its wash out by flash flood.
When the flow rate, river width, gradient and pollution load are given, the model can give the pollution load ratio of output to input.
By using the proposed model, the pollution load analysis to the lake Kasumi was performed. Regarding thirteen rivers flowing into the lake Kasumi, about 20% of organic carbon, and 5% of nitrogen to total amount of inflow are considered to be removed during the flow in the rivers.
