New modelling approach to optimize rainwater harvesting system for non-potable uses and groundwater recharge: A case study from Israel

Countries with dry climates must optimize the use of natural water sources. Rainwater Harvesting (RWH) is a viable water source for non-potable uses. Besides, rainwater can also be used for managed aquifer recharge (MAR). This work discusses the combined use of RWH for toilet flushing and MAR. A mass-balance simulation was used to estimate efficiency of the combined system in a building in Israel equipped with a RWH system used for MAR only. This enabled the use of actual water consumption patterns and the development of a runoff function using rainfall and runoff measurements. By the novel use and the integration of measured dynamic data into the model, the results are stochastic and the variability and uncertainty of the performance of the RWH system could be assessed. Non-potable water savings were-20% for the expected cost-effective tank size, and in this case-40% of the rainwater was used for MAR. The stochastic approach of the combined system proved the importance of the non-potable consumption value as well as precipitation series. Finally, it is shown that the potable water savings from using rainwater for toilet flushing would represent an annual CO2 emissions reduction of 267 kg.