Introduction
The behavioural model applied in the Behavioural Water Use node provides simulation of water use using the Behavioural End-use Stochastic Simulator (BESS) of Thyer et al. (2011). BESS stochastically simulates individual end-uses (outdoor, shower, washing machine, toilet, tap etc) at the household scale at sub-daily time steps using algorithms that probabilistically simulate an individual household’s use of common household water-using appliances. The conceptual framework for BESS as applied in the Urban Developer Plugin, is as follows:
Figure 1. BESS conceptual framework
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(after Thyer et al, 2009)
For indoor water uses, the water use simulations for each household are based on the type of water-using appliance and the household occupancy of that household. The difference from the average daily model is that instead of specifying an average daily volume and percentages for each end use, the user specifies the water-using appliance and household occupancy and BESS simulates the water for each individual end-use using the in-built parameters for the water use event dynamics. The types of water-using appliances for each end-use are configured in the appliance types. This enables users to simulate the effects of changes in the uptake of water efficient appliances.
The appliances and occupancy for each household can be specified in several different ways, configured under Edit>>Urban Developer Options:
- Fixed appliances and occupancy Appliances – where the type of appliances and occupancy for each house are fixed by the user
- Sampled appliances and occupancy – where the users inputs the user inputs probability distributions for the occupancy and water-using appliance. At the start of an Urban Developer Scenario run the occupancy and appliance type is randomly sampled for each house in the Behavioural Water Use nodes.
- Average appliance demand – rather than sampling from the probability distribution of water consumption for a usage event for each appliance, the average water use is selected. This mode can be used in conjunction with Fixed or Sampled appliances and occupancy.
Further details on these configurations are given below in Behavioural Model Configuration.
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BESS uses a diurnal pattern based on Roberts et al. (2005) to vary the probability of water use events occurring throughout the day. Future versions of Urban Developer will enable users to input their own diurnal pattern.
For outdoor water use, the behavioural model uses a time series or monthly varying pattern of average daily values, which can be input by the user - similar to the average daily model. For the sub-daily outdoor water use, the daily values are evenly distributed throughout the day. Future versions of the behavioural model may incorporate the behavioural impact daily weather has on outdoor water use variability (Micevski et al., 2011).
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The appliances and occupancy for each household can be specified in several different ways, configured under Edit>>Urban Developer Options.
Appliances
The behavioural water use model configuration with Appliances allows the user to set appliance types for each indoor (showers, washing machines, dishwashers, taps and toilets) and outdoor (pool) end use under the Appliances option in Urban Settings for each water use node. Household occupancy is specified on the water use node interface. The water consumption for individual water use events is still sampled from probability distributions, as described in Capturing Temporal Variability in Indoor Water Use Events.
Using the behavioural model with the Appliances option is the recommended approach when simulating a smaller number of houses (< 400), and allows the user to specify exactly the type of appliances and occupancy for each house. The indoor end-use appliance types and occupancy is set specifically for each water use node. Refer to the Node properties for details.
The Appliances model is enabled by disabling the Sampled Appliances & Occupancy menu.
Sampled appliances and occupancy
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The behavioural water use model with sampled Sampled appliances and occupancy allows you to specify random sampling of occupancy and appliance types, for each household, from statistical distributions.
Using the behavioural model with sampled Sampled appliances and occupancy is only recommended when you are simulating a larger number of households (> 400) and you do not want to set the appliance types /occupancy for each house.
When using the sampled Sampled appliances and occupancy model, the occupancy and appliance type node properties do not need to be configured. Other properties, such as the number of households, supply and discharge preferences do need to be configured. Refer to the Node Propertiesproperties for details.
The sampled Sampled appliances and occupancy model is enabled and disabled using the Sampled Appliances & Occupancy Menu menu.
Details of the sampled the Sampled appliances and occupancy algorithm are provided in Thyer et al. (2009) and references cited therein, a summary is provided below.
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For each appliance, the frequency of events per person per day, and the probability distributions of water consumption for an event, are defined in the Appliance Types Appliances menu.
Sample size requirements
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You can specify a number of houses smaller than 400, but should be aware that the sampled percentage of household occupancy and appliances appliance types may be different than the percentage you originally specified.
Random Seed
Random seeding provides a way to control randomisation of simulation outcomes. Random seeding applies to both sampled, and fixed, appliances configurations. The seed applies to both allocation of appliance types (eg Shower 0-Star or Shower 3-Star) to a house, and the actual water use, given the specified appliances. You can obtain repeatable results, or varied results, or repeatably-varied results with the random seed settings.
When using probabilistic simulations in models such as BESS, it can be difficult to reproduce results due to the random generation of water use.
The random seed is currently not editable in the Urban Developer Plugin, but this feature is planned for future versions to allow repeatable results with sampled appliances and occupancy.
Fixed appliances and occupancy
The behavioural water use model configuration with fixed appliances and occupancy allows you to set appliance types for each end use (showers, washing machines, and toilets), household occupancy and outdoor use for each water use node. The water consumption for individual water use events is still sampled from probability distributions, as described in Capturing Temporal Variability in Indoor Water Use Events.
Using the behavioural model with fixed appliances and occupancy is the recommended approach when you are simulating a smaller number of houses (< 400), and you want to specify exactly the type of appliances and occupancy for each house.
For this behavioural model configuration, you set the indoor end-use appliance types and occupancy for each water use node. Refer to the Node Properties for details.
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Average Demand
This mode can be used in conjunction with Fixed or Sampled appliances and occupancy and is activated by the 'Use Average Demand' checkbox available in the Behavioural Water Use node user interface.
References
Micevski, T., Thyer, M., Kuczera, G. (2011) A Behavioural Approach for Household Outdoor Water Use Modelling. Paper submitted to Water Resources Research (April 2011).
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