Water demand models for a small number of users

A better knowledge of the residential water consumption and the maximum water requirement allows for a more effective design or management of a Water Distribution System (WDS). The analysis of the behaviour of a small number of users in the request of water might be important also to understand the flow demand of numerous clusters of users supplied by a WDS. Indeed, each flow demand node can be seen as the aggregation of several consumers and, consequently, it represents the sum of several water requirements. An empirical study has been developed by monitoring a WDS in a small town, in southern Italy of about 1,200 inhabitants, in order to investigate water demand patterns and which probabilistic model could be better suitable to represent the residential water consumption. In particular, analysis on the experimental data collected from the system under consideration, has allowed to define probabilistic models which characterise the daily residential water demand. This study has highlighted that the goodness of those models depends on the number of users supplied and on the probability that a tap is opened. By means of statistical inferences on a large data sample, it has been shown that - at least for the range of users herein investigated – the Gumbel and Log-Normal distributions best represent the peak water demand; the mean water demand can be considered Normally distributed; the night flow requirement is well characterised with the Poisson model. In addition, in relation to the number of users supplied, the parameters of the probabilistic models have been estimated.