This study aims at decomposing the collective regulation mechanisms of irrigation in a context of public intervention. In a diachronic view, the compared approach of two irrigating communities anciently organized brings to light the dynamic feature of the water management rules. In a context of the inequation of the supply and the demand, the community rules organize a fair distribution of water shortage. But, although constantly renewed, these rules fail to satisfy the irrigators' rising need in water and are no longer respected. The public authorities are demanded to make these communal rules applied. The states suggest technichal solutions conditionned by the application of the national rules. The pair ‘ leading citizens/ administrative ...