Evaluation of potential rainwater tank outcomes using generalised equations and future performance of rainwater harvesting systems

Optimisation of rainwater tank outcomes has always been a challenge for the users, as the water savings depend on several factors such as annual rainfall, rainfall distribution in a year, roof area, tank size and rainwater demand. To overcome this hurdle, this research presents the development of robust equations for calculating expected annual water savings through rainwater tanks, which consist of variables like annual rainfall, rainwater demand, tank size, and roof area. Moreover, as the development of such equations for every location is a tedious task, the usefulness of using such equations for neighbouring locations warrants attention. This research investigates the spatial sensitivity of four generalised equations developed earlier for Brisbane to be used for any random location in Brisbane. Also, due to the onslaught of climate change, the rainfall pattern is likely to get altered in future and this may affect the performance of a rainwater harvesting system (RWHS). However, studies related to the effects of climate change on RWHS are limited. This research examined the future performance of rainwater tanks in Brisbane under two different climate change scenarios: RCP4.5 (optimistic scenario) and RCP8.5 (pessimistic scenario).