This paper presents a real time Operation Model for the Alto Tiete water supply System for the São Paulo Metropolitan Region. The Operation Model consists of a data base, a mathematical model and a user interface that indicates the system operating rules. Data is acquired in real time through a telemetric network. The optimization model runs linear programming software based on the Interior Point Method using Linear Objective Function and channel damping. The main objective of the Model is to optimize the water resources of the upper Tiete river by inflow storage and pumping maximization, through Biritiba pumping station, during floods and to rationalize operation in order to provide the minimum environmental flow and demands throughout the basin, as well as to reduce the risk of a deficit in the Taiaçupeba Water Treatment Station. The Operation Model is integrated to the planning models that establish the monthly operational requirements.