Résumé
In Europe, improvements in water-use efficiency have been encouraged in order to achieve the Water Framework Directive's environmental goals. However, it is often unclear where the saved water (if any) goes and to what extent it benefits aquatic ecosystems. While the technical aspects of this question have been widely debated, its political dimensions have seldom been addressed. In particular, few studies have examined the formulation, implementation or governance of policy tools aimed at reallocating 'saved water' to the environment. In the Durance River Basin (south-east France), a Water Saving Account (WSA) was created to facilitate the reallocation of water savings to aquatic ecosystems. Combining the political sociology of policy instruments and historical neo-institutionalist approaches, we show that, rather than fundamentally reordering water distribution, the WSA constitutes an ambiguous arrangement that favours the continuation of water savings investments - a policy that is compatible with a large array of objectives and interests - while at the same time embodying and manifesting the new environmental goals and rationale of the Agence de l'eau (Water Agency). We underline the key role of ambiguity in making 'things which hold together' and facilitating consensus among the main actors involved