In this article, a general methodology for simulation of water resources management is suggested. The research has been conducted in three different levels: a deep analysis of the historical management procedures, the development of some alternative ways to optimal management, and the establishment of planning criteria at short, middle, and long term. The main constraints, divided into three categories according to the severity of probable losses, have been defined as a function of several expected goals: hydro power, flood control, recreational activities, etc. The model was applied with excellent results to the upper region of the St. François river basin (Québec, Canada). Key words: simulation, resources management, mathematical models, optimization.