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Top1. Introduction
Demand for water is the sum total of all uses in all sectors (domestic, industrial, and tourism) and all losses recorded. Thus, the demand management is the set of interventions and organizational systems that companies and governments implement to increase the technical, social, economic, institutional and environmental efficiencies in the management of water (Point 1993). Water demand management, therefore, aims to reduce physical and economic losses and wastes, to better meet the demand in terms of quantity and quality of the current and future generations. Its implementation is based on a set of tools that must be adapted to each situation of the demand management policies. It aims to identify uses of water, optimize its consumption, and provide more products or services that provide more value and more sustainable development for each m3 of water received or levied (Howe 1982).
Despite the importance of water, many countries around the world are in disadvantaged areas. Indeed, available resources are constantly decreasing as a result of climate change and increased demand resulting from the consequences of population growth and economic development. In this vein, Tunisia is located in this geographical context and hence, it is one of several countries suffering from a serious lack of water resource. In Tunisia, the need, the scarcity and the cost of water are major challenges to be dealt with by the strategy-developers for demand management and water saving. These natural and economic constraints have incited the Tunisian government to participate actively in the development of water resources management.
In fact, to monitor the management of the drinking water resource, Tunisia has a long history of making the most of its water resources gathered in years when precipitation is high. But these resources are often limited, random and unequally distributed among the regions (Bouchrika et al., (2018)). Consequently, the scarcity of this resource has generated a differentiated behaviour of water consumption implying a differentiation in the preference of households (Bouchrika et al (2017)).
According to Pearce, Moran and Fripp (1992), the economic value of drinking water is calculated on the basis of two concepts: the benefits derived from the use and those derived from the conservation of water. Total economic value is composed of direct and indirect use values as well as non-use values such as the values of biodiversity and genetic diversity. Nevertheless, it should be noted that in this paper, we are only interested in the value of the direct use of water measured by household consumption.
Indeed, the purpose of this paper is to study the behaviour of the consumers regarding their consumption of drinking water as well as their own self-conception of the nature of the physical quality of this good. To do this, we will determine the most important explanatory variables in the estimation of the demand function and the WTP through the technique of contingent valuation survey.
By and large, in the absence of the market, it would be very difficult to know the exact value of the natural resource. Thus, to provide an acceptable means of measuring the economic value of the resources mentioned above, hypothetical or simulated markets are conceived. Contingent valuation is the most appropriate method resourcing to consumer surveys. The theoretical basis of the contingent valuation method is based on the theory of economic utility and well-being. It involves asking individuals directly to reveal their preferences in terms of willingness to pay according to different scenarios presented to them.