A probabilistic behavioural approach for the dynamic modelling of indoor household water use

Abstract

The emergence of the Integrated Urban Water Management (IUWM) design paradigm which utilises interventions at the household scale to reduce the demand on large scale water supply infrastructure has driven the need for a greater understanding and ability to simulate urban water use dynamics at the household scale. Urban water use at the household scale is a probabilistic behavioural response by individuals to a set of drivers. This paper outlines a hierarchical urban water use modelling framework for the probabilistic behavioural modelling of urban water use. The top level consists of the main drivers of urban water use, the second level simulates the spatial variability between houses (varying number of people, and varying water use appliances) and the third level simulates the temporal variability of an individual house. The methodology for simulating household indoor water use within this framework is described in this study. This consists of probabilistically simulating water use occurrence and event volumes for different end use categories (shower, washing machine, toilet etc) at minute time steps. The results showed the simulations provided a good match to the observed statistics provided by a detailed end use measurement study (Roberts, 2005) for individual water use events. The simulated aggregated statistics (total daily water use per capita for each end use and the distribution of daily total water use per capita) also provide a good match to the observations. A generic modelling approach has been adopted by separating out the behavioural processes which govern the occurrence of the water use event and the appliance that is used for that event. This has two advantages (1) Provides the potential for the model to be transferred to other regions and utilise local information and (2) Water use scenarios with different rates of uptake of water efficient appliance can be easily simulated. This capability was demonstrated with by providing simulations of water use for two scenarios with varying rates of uptake of water efficient appliances.