Water resource represents an important stake for human development. Studies show that under the currently growing demand this resource can become scarce, therefore, leading to the necessity of reducing unnecessary demand. Household needs often represent an important proportion of the overall demand, while individual costs are not high enough to lead the consumer to restrict his demand to the essential. Therefore, besides pricing policies, evaluating the impact of various incentives and information policies in reducing household demand represents a current stake in modelling for water management support. One of the major difficulties for this is to account for local information ignoring spatial inter-dependence of the resource and heterogeneity in the population. In this paper, we tackle the possibility of simulating a composite population of water consumers and/or more than one water resource by a linear approximation derived from simple configurations (a single consumer population linked to a single resource). We model a reversible diffusion of careful consumption behaviours in a population influenced by public information on the resource. Our results show that the adequacy of linear approximation depends on the choice of information provided to the consumers, and more particularly on the definition of a state of crisis. We discuss implications of this result from various points of view.