EVALUATION OF OPTIMAL CONSTANT-VOLUME CONTROL FOR IRRIGATION CANALS

A lumped-parameter model was used for stimulating the dynamics of an irrigation canal using the concepts of optimal control theory. Using the state-space approach presented by Corriga, the problem was formulated as a discrete optimal control problem, and the solutions for gate opening in the presence of known variations in water withdrawal rates were obtained by solving the algebraic Riccati equation. An example problem was considered, and the variations in the depth of flow obtained by using the optimal control theory were compared with the results obtained from an unsteady open-channel flow model. For small and slow changes in the flow rates, the difference between the two models in predicting the changes in water surface elevation was not significant. However, as the variations in withdrawal rates increased, the accuracy of the optimal control model (which is based upon small perturbations around the uniform flow) in predicting the water surface elevations decreased. © 1990.