In this paper, a methodology for the optimal management of a combined irrigation and water supply system based on model predictive control (MPC) is proposed. A controloriented modelling methodology for this type of systems is presented as well. MPC is used to generate flow control strategies from the sources to the consumer and irrigation areas to meet future demands with appropriate flows, optimizing operational goals such as network safety volumes in dams and flow control stability in actuators (valves, gates and pumps). The case study of Guadiana river is used to exemplify and verify the proposed optimal management methodology. Results have shown the effectiveness of the proposed modelling and control methodologies.