Although environmental benefits of green roofs are well understood and formulated in some countries, the scientific knowledge of this WSUD technology is still in the earliest stages in Australia. In this paper, water quality and quantity of sixteen green roof beds were investigated and discussed. This experimental design was split plot with slope and depth of substrate as main plots (both two levels), and sub-plots of substrate and plant types (three levels). This consisted of twelve vegetated beds including four non-vegetated beds as controls. Stormwater runoff was collected from drainage points which were installed in each sub-plot mesocosm. In this study, stormwater run-off of five rainfall events was analysed for water quality parameters of No2, No3, NH4, PO4, pH, EC, TDS, Turbidity and K. The results showed significant differences between outflow of both vegetated and non-vegetated systems, and rainwater. Comparing the quality of rainwater as inflow, and the quality of runoff from the systems indicates that green roofs acted as a source of pollutants in this study. Furthermore, intensive green roofs performed better than extensive with regard to quality of outflow. The growing media water retention was between %30 to %100 and the range attributed to the slope and vegetation cover. In addition, the growing media with less organic matter had better water quality performance. Comparison of these results with the available standards for feasibility of green roof outflow reuse, in respect of water usage in buildings, confirmed possible re-use of the outflow for nonpotable usage such as urban irrigation.

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