This paper proposes a new advanced strategy to control open main irrigation canals. A methodology is developed to design fractional PI controllers for irrigation main canals, which show enhanced robustness properties over the standard PI controllers. This methodology is applied to solve the problem of effective control of water distribution in the first pool of Aragon's Imperial Irrigation Main Canal belonging to the Ebro Hydrographical Confederation (Spain). The experimental results show the effectiveness of the developed methodology. Copyright © 2007 IFAC.