Submitted to: US Committee on Irrigation and Drainage/Environmental and Water Resources Institute Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2002
Publication Date: 5/15/2002
Citation: Wahlin, B.T., Clemmens, A.J. 2002. Preliminary results for downstream feedback control of branching canal networks. US Committee on Irrigation and Drainage/Environmental and Water Resources Institute Conference. p.387-397. Interpretive Summary: Water is becoming a scarce resource, and agriculture¿s share of available water is likely to decrease in the future. Agricultural water suppliers are coming under increased pressure to improve water measurement, control, and accounting. In addition, the customers of agricultural water suppliers are demanding more flexible water deliveries so they compete in the marketplace and implement water conservation measures. Computerized automatic control of canal systems is one tool that can be used to improve the operation efficiency of agricultural water delivery systems. Many advances have been made in computerized automatic control of a single, in-line canal system, but there has been no progress made on computerized automatic control of a branching canal network. Automation of a branching canal network is desirable because then the entire agricultural water delivery system can be automated instead of just one portion. This paper presents preliminary simulation results of a new method for the automation of branching canal networks. These results will be of use to irrigation districts, consultants, and the U.S. Bureau of Reclamation.
Technical Abstract: Over the last 40 years researchers have made various efforts to develop automatic feedback controllers for irrigation canals. However, most of this work has concentrated on feedback controllers for single, in-line canals with no branches. In practice it would be desirable to automate an entire canal network and not just one of the branches. Because the branches in a network are hydraulically coupled with each other, a branching canal network cannot be controlled by designing separate controllers for each branch and then letting them run simultaneously. Changing the gate position in one pool on one branch can affect the water levels in pools on other branches. Because of this effect, the controllers designed for each of the in-line branches of the network will interfere with each other and potentially create instabilities in the branching canal network. Thus, the controller must be designed for the network as a whole and the branching flow dynamics must be explicitly taken into account during the controller design process. This paper presents preliminary simulation results on three different downstream feedback controllers on a branching canal network. The first controller is a series of Proportional-Integral (PI) controllers, one per pool. The second is a fully centralized PI controller. The third controller uses Model Predictive Control (MPC) to determine the appropriate control actions.