Green façades irrigated with greywater in Perth’s Mediterranean climate: The use of greywater-irrigated façades could prove that green walls can survive in Mediterranean climates

Green walls are gaining popularity in urban areas for offering aesthetic, shade and thermal benefits. However, with climate change and reduced rainfall, shortages of potable water makes it a restricted irrigation source. This paper investigates the viability of using locally-produced greywater as an alternative source for green wall irrigation. Pilot-scale green façades (a selective configuration of green walls)were established at Bentley Primary School, with plants rooted in stand-alone planters (2500 x 700 x 750 mm) in Perth, Australia, and irrigated with greywater. Inflow and outflow volumes from the planters were monitored from June2019 to December 2020; water balances were established across season, plant type (non-deciduous and deciduous)and orientation (east, west and north facing). The analysis demonstrated that in cooler months (May – September) the irrigation volumes required for plant health was on average 5mm/day Monday ‒ Friday, which increased to 7 mm/day in warmer months. The outflow was highly variable and a function of season, plant type and orientation; in cooler and warmer months it ranged from 0.5 – 4 mm/day, and 0 – 0.2mm/day, respectively. This work illustrates that green façades irrigated by greywater are viable under Perth’s Mediterranean climate, and shows opportunities for reuse of the outflows.