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: 7/13/2002
Citation: Bautista, E., Clemmens, A.J., Strelkoff, T. 2002. Routing demand changes with volume compensation: an update. US Committee on Irrigation and Drainage/Environmental and Water Resources Institute Conference. p. 367-376. Interpretive Summary: In many irrigated areas of the world, farmers receive water through networks of canals. Controlling deliveries through such networks is difficult and most of these systems are operated based on experience rather than on hydraulic principles, often resulting in inaccurate deliveries to users and operational spills. Development and application of canal control techniques can help improve agricultural water management. A simple yet hydraulically-based control scheme has been under development at the U.S. Water Conservation Laboratory. The method develops a schedule of canal inflows for a known schedule of water demands. This paper analyzes one of the underlying assumptions of the method, namely that a complex control problem consisting of multiple water demand changes in a canal with multiple pools, can be analyzed as a sequence of individual canal control problems. Results suggest that the method is valid under a wide range of conditions, typical of canal operations. The proposed methodology should be of great value to operators of large water delivery systems.
Technical Abstract: In using the gate-stroking method, this paper shows that a complex open-channel flow feedforward control problem can be treated as a series of linearly additive single flow-change control problems. A key element of this approach is determining the initial conditions for each single flow-change problem. An inadequate choice of initial conditions will result in an under- or over-estimation of the canal storage volume change needed for the new steady-state conditions. These findings provide support to a simple feedforward control scheme based on volume compensation and time delay. An example is used to demonstrate that the simple scheduling approach is nearly as effective in controlling water levels as the complex gate-stroking approach.