The Canal de Provence is fully user oriented. Water users can take the water freely without respecting neither rotation nor any sort of priority allocation. Its structure, consisting of main free flow canals and pressurized distribution networks, is well adapted to this strategy. The main canal must be able to face the regime variations coming from this kind of distribution. The current regulation conception first split the whole system into a series of assumed independent subsystems. The multi-variable aspect is then taken into account by a coordination of the sub-systems adjustment, carrying the discharge correction from downstream to upstream. The Aix nord branch control presents interesting characteristics such as many different hydraulic entities (free surface canals, reservoirs, pumping stations) and operating constraints (levels in reservoirs, optimization of pumping costs). A real multi-variable approach will allow managing all gate and pump operations and all constraints at the same time, leading to a global optimisation of the whole system. The MIMO (Mulit Input - Multi Output) model is established from transfer functions, the coefficients of which are deduced from the physical and geometrical characteristics of the system. A Linear Quadratic Regulator is computed and tested on a complete non-linear numerical model of the hydraulic system. The system to be controlled includes many discrete commands (pump operations) that are not managed by a classical optimal control. These commands are treated apart, leading to calculated perturbations that are introduced in the regulator.