Continuous simulation of rainwater tank, wastewater storage and stormwater runoff: the influence of climatic regimes, water demand and diurnal flow patterns

Using the Probabilistic Urban Rainfall and wastewater Reuse Simulator (PURRS), this study investigates the variability produced in mains water savings, wastewater flows and stormwater runoff at the allotment scale. Continuous simulation of rainwater harvesting and wastewater systems was performed with different water demands and roof areas on 600 m² allotments in Auckland, Adelaide, Brisbane, Melbourne and Sydney. Results indicate that there is plenty of water available at the allotment scale. For a variety of integrated water cycle management options (IWCM) options, a range of solutions can be obtained for an array of water demands (persons per household) and roof areas. Climatic regimes governing rainfall depth/distribution and water demand distribution are also shown to influence the magnitude of the IWCM options evaluated. This study highlights the benefits of a range of allotment scale IWCM options that result from different climate regimes, water demands and roof areas. The significance of results is that when rainwater tanks and/or wastewater systems are introduced at the allotment scale, there is plenty of water available for all uses. However, the extents of benefits are dependent on climate regime and water demand. In addition, the implications for catchment water resource management are highlighted in the context of perceived water shortages in the future.