Future performance of rainwater tanks and impacts on weather variability under climate change scenarios

Abstract

Numerous studies have been conducted regarding the financial and environmental benefits of adopting a rainwater harvesting system (RWHS). However, studies related to the impacts of climate change on RWHS are still limited. Climate change is likely to alter the rainfall pattern, which will affect the performance of RWHS. This paper presents an assessment of the future performance of rainwater tanks for the city of Brisbane (Australia) under different climate change scenarios; RCP4.5 (optimistic scenario) and RCP8.5 (pessimistic scenario). The future daily dynamically downscaled rainfall data was downloaded from a data portal set up by the Australian government. Future rainfall data predicted by two coupled climate models (ACCESS1.0 & ACCESS1.3) for 3 distinct future periods (near future, intermediate future and distant future) along with historical rainfall data were fed into a previously developed daily water balance model (eTank) to simulate the rainwater tank outcomes. Three weather conditions, dry, average and wet years were considered in each future period. The future outcomes were compared with the present outcomes derived from historical rainfall data. It is found that the performance of the rainwater tanks will deteriorate in most cases. Although, in a few cases, the water savings are expected to increase, however, that is mostly with the RCP4.5 scenario. Regarding the variability in annual water savings, the variations are anticipated to be both increasing and decreasing depending on the station and the climate model used.