  In this paper, we apply an optimal LQ controller, which has an inherent
structure that allows for a distributed implementation, to an irrigation
network. The network consists of a water reservoir and connected water canals.
The goal is to keep the levels close to the set-points when farmers take out
water. The LQ controller is designed using a first-order approximation of the
canal dynamics, while the simulation model used for evaluation uses third-order
canal dynamics. The performance is compared to a P controller and an LQ
controller designed using the third-order canal dynamics. The structured
controller outperforms the P controller and is close to the theoretical optimum
given by the third-order LQ controller for disturbance rejection.
