抄録
In urban areas, heavy rains of only a few hours' duration can cause flood, whereas people living there are likely to be faced with water shortage crisis when rains are few. Further, organic, nitric and phosphate pollution of the river is a problem in these areas. This largely depends on the land use on the basin. In the present study, a water recycling model using Geographic Information Systems (GIS) including land use data was constructed to estimate the run-off system and the water pollution on the basin. This GIS model was applied to assess the present and future water environment in Hachioji City, Tokyo, Japan, focusing on Asakawa River and its branches.
The basin area was determined automatically by calculation of the land slant, and then the outflow consisting of three kinds of flows, i.e. surface flow upon raining, intermediate ground-permeated flow and the last base flow, was estimated. The evapotranspiration parameter was set up for every land use, and water pollution load calculation was made by unit method. Finally, the basin area was determined with sufficient accuracy as compared to the actual data with 4 % error, and the study was extended to predict the water quality (BOD, SS, T-N, T-P) and river flow as applicable when sewage system was completed in these areas. The GIS model enables the prediction of the water flow and quality as well as the assessment of the water utilization effects.
