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For outdoor water, the behavioural model uses monthly varying, 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).
Diurnal Pattern
I
The statistical distributions used by BESS to generate the sub-daily indoor water use are based on the end-use study of Roberts et al. (2005). Users are encouraged to check that the predicted water use statistics provided by BESS match their expectations. BESS uses a diurnal variation to vary the probability of water use events occurring throughout the day. It disaggregates the daily demand data to a sub-daily time-step using a non-dimensionalised diurnal pattern.
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Fixed Behavioural
Sampled Behavioural
Spatial Variability
The household size and the type of water using appliances vary from household to household. To capture this spatial variability the household size and appliance type for each type of water use event is randomly sampled for each household from a probability distribution based on the proportion of household sizes/appliance types. An example of these probability distributions based on Roberts [2005] is provided below. This information can also be obtained from Australian Bureau of Statistics (ABS) surveys
Temporal Variability
Individual end-use events are generated in a two stage process. The first stage determines whether a
given water use starts in a particular time step, and is based on the probability of occurrence, ( )
O
for a particular end-use. The second stage tracks the subsequent behaviour of that water use over the
following time steps, and is dependent on the end-use event volume, Vt W and water usage pattern,
Pt W In general the probability of occurrence for each event was a function of the frequency of events
per person per day, the household size ( t HS ) and a diurnal factor (DF). The diurnal factor converts the
frequency of events per day into the probability of an event occurrence in a given minute taking into
account the diurnal variation of the event, which is an input. The water use event volume and the
water usage pattern is dependent on the type of water use event and the appliance type. In general,
the end-use event volume is sampled from a probability distribution, and the water usage pattern is
applied to this volume to produce a water use time series. The approach used to define ( )
Ot P W , Vt W
and Pt W for each individual water use event type will be described below. This largely follows that of
D&M, although some enhancements have been made and where these occur they will be outlined.
The Behavioural End-use Stochastic simulator (BESS) stochastically simulates individual end-uses (outdoor, shower, washing machine, toilet, tap etc) at the household scale at sub-daily time steps. The indoor component simulates differences in household size, uptake rates of water efficient appliances and diurnal variation in end-uses. The behavioural water use model configuration with 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 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.
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