Résumé
In this paper we pose the question of the impact of strategic interactions on the efficiency of group performance based instruments for the management of the environment. We focus on irrigation-induced salinity that encompasses three notions at the core of environmental issues : non-point source pollution, common pool resource and stock pollution. Recourse to group performance as a basis for policy instrument has been proposed for each of these contexts. We identify and analyse different strategic interactions, between the agents and the policy maker, and between the agents, arising from the implementation of group performance based instruments. The former constitute the main reason for applying group performance based instruments. The latter have both positive and negative consequences on their efficiency. As a result, we advocate mixing group and individual incentives in the design of policy instruments.