Applying automatic control methods to irrigation canals is a way to improve the management of irrigation systems. The dynamic difficulties that involved this hydraulic systems such as non-linearity, varying time delay, and uncontrolled perturbations make the choice of a suitable automatic control method a challenge. To this purpose, this paper presents a methodology for design of decentralized robust adaptive predictive control system of water distribution in irrigation canals. The objective of this system is to maintain the downstream end water level of each pool at constant target value under external uncontrolled perturbation.