abstract:For carrying on the study of rainfall coeff. (rainfall collection efficiency coeff., C) and rainwater quality, four different roof-types of rooftop rainwater cistern system have been set up in National Taiwan Ocean University. From March to December in the year of 1997, approximately 100 storm events have been collected. The results show that C value increases slightly as rainfall intensity increases and varies more highly at low rainfall intensity than that of high situation. For water quality aspect, both runoff during rainfall period and water in storage tank after the rainfall stops will be collected and analyzed for eight variables (DO, pH, conductivity, turbidity, NH/sub 3/-N, NO/sub 3//sup -/-N, hardness and coliform bacillus). Results show that water quality from the roof are good and material of roof has some effects on those of water quality. Therefore, longer observation period and more detailed studies on roof water quantity and quality are required.