Abstract
The objectives of this study are to establish a runoff model and show pollutant loadings discharged into Lake Biwa by simulating the change in pollutant runoff in proportion to the progress of sewer construction. The runoff model, hereinafter referred to as “Macro Model”, consists of three main sections. The first one shows pollutant runoff from point sources taking into consideration the sedimentation of pollutants in sewers. The second and third ones show pollutant runoff from nonpoint sources in an urban and rural area taking land use into consideration.
As a result of the simulation on nutrient runoff, the distribution of pollutant loadings in Lake Biwa basin and their runoff characteristics, which were changing in response to sewer construction in the basin, were shown. And it was cleared that the ratio of nonpoint pollutants to integrated pollutant loadings discharged from all sources into Lake Biwa should be 0.8% for T-N and 3.1% for T-P after sewer system achieve 100% coverage. Therefore, it was proved to be significant to control these pollutants discharged during storm events.
In the result, some available knowledge concerned with the environmental management of water in Lake Biwa was obtained.
