Résumé
This paper addresses the relations between the Common Agricultural Policy and the farmers water demand for irrigation. Three case study which are representatives of French areas suffering from water use conflicts, are analysed : upstream Charente river basin (west of France), upstream Adour river basin (south west of France) and Beauce aquifer (centre of France). A stochastic linear programming model, aggregated at the basin level, has been built for each zone. They take into account the diversity of farmers behaviour regarding cropping patterns and irrigation practices, the inter annual variability of water resource and crops water requirements. These models allow to simulate different scenarios of CAP reform (market prices, fallow rates and ways of allocating subsidies). Reform alternatives are compared in terms of impact on agricultural water consumption and farmers incomes, economic valuation of irrigation and water demand sensitivity to its price. The simulation results provide guidelines for the definition of economic instruments that allow a better adjustment of farmers water demand to available water resource.