The answer does not really fit to the question as it is less about information missing or exlcuded but wondering how representations follow a certain logic. Especially if we consider smart metering as a next step, the question is how the average is calculated. For the presented average number of 128l per person per day, this seems like a statistic average; if smart meters are then combined with other data of a household, it is an aggregate based more in a predictive logic?
in the infographic an average individual is the unit. There are obviously several assumptions about this individual: it is probably living in a house (needs to water a garden) and owns a car. The average use seems to be based on classic statistical calculations and probably starts with household based and billed water use. all kinds of questions then arise on how to make this more complex or at least draws attention to the question of how decisions were made of the different values and calculations on the way. It is also interesting to think of alternative units of analysis/observation: water scarcity is usually a communal / regional issue and situating water usage in more specific contexts could be another logic. Looking at water conflicts and the governance of water as a scarce ressource could help to see the different logics and debates that feed into claculating water.