Rainwater harvesting: revealing the detail

The Probabilistic Urban Rainfall and wastewater Reuse Simulator (PURRS v7.2,the Model for Urban Stormwater Improvement Conceptualisation (MUSIC v3) and Spreadsheet modelling tools were compared for evaluating rainwater harvesting strategies. Input data included climate files, suggested water demands and time-steps. Models were run with climate data of unequal duration and time-step,which highlighted significant differences between modelled outcomes. Using climate data of equal duration still resulted in major differences. The reasons for these differences are explained as a function of the duration and time-step of climate data, the time-step and diurnal patterns of indoor/outdoor water demand and tank configuration. Results imply that the length and time-step of climate inputs, the distribution and time-step of daily water demand and rainwater tank configuration are significant factors in robustly evaluating mains water savings for a range of Australian climates.