Résumé
From twenty years, water conflicts have increased in France due to a sharply rise of water demand compared to new infrastructures construction. Water actors have therefore to find management instruments to reduce these conflicts. The case of Charente river is taken here. Due to the augmentation of irrigation water withdrawals, Charente river faced water shortage at the end of 80's. To solve the conflict which appeared between irrigators and actors who represent the importance of water for environmental purposes, two measures where adopted : the construction of new dams and the implementation of economic tools to incite (or to constrain) farmers to not consume this new water resource assigned to 'environment'. In order to represent farmers response (in term of water consumption) to that economic instrument implementation, a model which simulates their water consumption behaviour is designed and presented in the first part of the paper. Then different economic tools are tested under different hypothesis of the water manager informational level. It reveals that the signal chosen (an annual water consumption) is not sufficient. Therefore the last part is focussed on the study of three water management systems which can solve the problem of information asymmetric.