Design of Control Algorithm for Operation of Irrigation Canals

Using a linearized finite-difference model of open-channel flow, the canal operation problem was formulated as an optimal-control problem, and an algorithm for gate opening in the presence of arbitrary external disturbances (changes in flow rates) was derived. An observer was designed to estimate the values for depths of flow and flow rates at the intermediate nodes based upon measured values of depth at two points in the pool. Control algorithms were derived for both a constant-level control and a constant-volume control. For the purpose of evaluation, the equations of the controller and the observer, derived with the linearized model, were included as modules in a nonlinear open-channel flow model. In an example problem with an external disturbance of 20% of the initial flow rate in the pool, the performance of the control algorithm and the observer in maintaining a constant level at the downstream end of the pool was found to be acceptable.