Developing a new outdoor household water use index to identify rainwater harvesting potential

To presently manage urban stormwater more efficiently, it is necessary to provide sustainable and decentralised practices in urban areas. For that reason, Rainwater Harvesting Systems (RWHS) are becoming increasingly popular in many countries as a solution for collecting and reusing rainwater while protecting sewer systems from overloading. However, to determine the suitability of their use, it is important to know the outdoor tap water use patterns as determined from sub-metering data. To date, limited research has been conducted on actual measurements of outdoor tap water use recorded at the property level. The objective, therefore, of this work is to identify the potential for rainwater harvesting based on the newly developed Water Use Index (WUI), with criteria that can inform the appropriateness of RWHS implementation at the household level. The study was conducted on forty properties based on sub-metering data from eleven-year monitoring. The Rainwater Use calculator on the WaterFolder online platform, as well as statistical methods and machine learning techniques were employed in the analysis. The results of the study showed that 34 of the 40 properties (85 %) are recommended for RWHS installation based on the developed WUI. The structure of the decision tree confirmed the validity of extracting RWHS performance criteria based on the WUI, and its modeling results yielded a test quality of R² = 0.956. The results can provide valuable insights in developing good practices' guidelines for decision makers toward improving stormwater management at the local level in urban areas.