Conference Agenda

Green roofs are an important and versatile type of blue-green infrastructure with multiple application potentials and several benefits. Irrigation of green roofs can enhance these benefits and greywater provides a sustainable source of irrigation water. This paper describes a water balance model for the evaluation of green roof irrigation strategies and storage tank size optimization. The model accounts for different water sources, irrigation strategies and green roof types. The model operates with openaccess data, provides site-specific results for Germany and can be easily adapted for other regions. The model was calibrated with experimental data for green roofs with different irrigation intensities from Dresden green roof research facility. It obtained satisfactory to good performance, with Nash-Sutcliffe efficiencies of 0.59 - 0.71 for daily runoff, 0.66 - 0.82 for substrate moisture and 0.69 - 0.79 for actual evapotranspiration. Long-term simulation for the same site revealed that irrigation significantly reduces drought periods for green roofs and increases evaporation by up to 65 %. Irrigation with greywater provided higher supply reliability than rainwater for the same storage tank size. A combined supply with both water sources enabled complete supply reliability during the simulation period with a minimum relative storage level of 35%.