Rapid estimation of rainwater yield throughout Australia and review of Queensland rainwater harvesting operating policy

Rapid estimation of national rainwater yield for low and high performance scenarios is derived using Taylor's Hyetal Index (THI). Stochastic representations of the modes of failure of rainwater harvesting (RWH) systems is the foundation of THI. THI holds a strong regression to RWH performance for 7,000 variations in the national residential built environment (r2 = 0.96). A small subset of 34 variations is presented in this summary paper. THI is based on inspecting daily rainfall data from the Bureau ofMeteorology, which enables rapid and accurate rainwater yield estimation at potentially any location throughout Australia. A review of the Queensland RWH mandate, using THI, has demonstrated many locations can achieve or are close to achieving their water saving targets. The worst performing region is South East Queensland, which is also an area of high population and municipal water demand. This region is also able to significantly exceed their water saving target,when adopting a RWH system beyond the mandate. Therefore, with changes to the mandate, Queensland could increase their renewable natural capital and societal and environmental benefit.