Valles del Tuy adduction network presented a great lack of knowledge concerning the system operational behavior. The discontinuity of water supply, water rationing by sector, nonexistence of operational control and changing regulation during the day by means of valves opening and closing made the system unpredictable. It was a real challenge to take into account all these factors and introduce them in a mathematical model. The result was a long-extended period model that was able to reproduce the system behavior with reliability in extended-period simulations. Based on it, a diagnosis of the critical points of the system was developed, that led to an improvement proposal. The proposals were focused on designing a controlled adduction system with the optimal operational behavior and without the necessity of making day-time changes for achieving a continuous and reliable water supply.