Valeur de préservation de la qualité de l'eau souterraine : une comparaison entre usagers et non-usagers

Preservation value for groundwater quality : a comparison between users and non-users. We report the results of a contingent valuation study on the willingness-to-pay (WTP) for preserving groundwater quality in the Alsace region (France). The resource is a large aquifer which supplies 80 % of the households of the region. The purpose of our paper is to compare the results of two separate studies, one concerning households that are supplied by ivater from the aquifer (users) and households which are currently supplied by a different source than the aquifer (non-users). Non-users are households which are located in an area close enough from the aquifer to become eventually supplied by groundwater in the future. We expected that non-users would be likely to pay an insurance premium in order to secure access to a substitute and preserved water source in the future, for the event where their current water source would be polluted. A contingent valuation questionnaire was submitted to respondents in 12 different locations spread over the aquifer region during a face-to-face interview. In 2 of the locations there were only non-users. One of the main results of the study is that non-users are willing to pay a substantial amount of money to preserve the quality of the water in the aquifer, even if they believe that it is unlikely that they will use it in the future. Moreover, their WTP relies apparently much more on bequest and existence motives than on an insurance motive. The results also show that the households' dependence on groundwater has a positive influence on their WTP. The non-users' mean WTP is about 60 % of the users' WTP, which is an interesting indication about the importance of non-users for contingent valuation studies. But both WTP have different explanatory variables. Only the bid value and the respondent's income appear as common explanatory variables in our study.Cet article présente les résultats d'une évaluation contingente de la valeur de préservation de la qualité de l'eau souterraine pour des non-usagers. Les non-usagers sont définis comme des ménages géographiquement proches et potentiellement dépendants de la nappe phréatique pour leur alimentation en eau potable. Nous proposons une comparaison de la valeur de préservation et de ses déterminants, entre les usagers et les non-usagers de l'eau de la nappe. Cette comparaison permet d'isoler la valeur de préservation pour des usages futurs de la valeur de préservation pour un usage futur hypothétique. L'objectif de notre analyse est d'estimer la part que représente la valeur de non-usage dans la valeur de préservation des usagers et de comparer les comportements des non-usagers avec ceux des usagers.Rozan Anne, Stenger Anne, Willinger Marc. Valeur de préservation de la qualité de l'eau souterraine : une comparaison entre usagers et non-usagers. In: Cahiers d'Economie et sociologie rurales, N°45, 4e trimestre 1997. pp. 61-92