Submitted to: North American Water and Environment Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/22/1996
Publication Date: N/A
Interpretive Summary: Improving the operation of canal networks that deliver water to farms can improve the flexibility and reliability of water deliveries and reduce water losses by spillage. Without a flexible and reliable water supply, it is difficult for farmers to apply irrigation water in a timely manner and in an amount that meets crop needs. Developing standard canal operating techniques is difficult because of wide differences in physical characteristics and hydraulic behavior of canals. This paper describes the initial results of a study that examines how canal physical characteristics influence operators' ability to control water flows. The study is limited to the case where water demands are known in advance and flow changes are made in anticipation of those demands. The study involves numerous simulations with a mathematical model. Initial results show that certain canal properties greatly increase the difficulty of controlling flows. Developing a better understanding of these issues is particularly important when considering upgrades to older water distribution systems. Results of this research will help engineers and canal system managers identify general conditions under which flow control with known water demands is difficult and will also guide future development of practical control alternatives.
Technical Abstract: Gate stroking is a technique for computing a schedule of canal inflow variation that will deliver a specified downstream demand. The gate-stroking method solves differential equations of unsteady open-channel flow beginning at the downstream boundary, where demand is specified, and then moving upstream, eventually computing the inflow hydrograph. Gate stroking has not been adopted as a practical tool for canal control, partly because solutions are often difficult to implement. However, the method can still be used to examine the feasibility of anticipatory control measures in open-channel delivery systems. Thus, a study is being conducted to characterize the behavior of gate-stroking solutions as a function of canal physical properties and changes in water demand. Solutions are being generated with a nondimensional formulation of a nonlinear finite-difference gate-stroking model. Use of nondimensional variables reduces the number of free parameters in the governing equations and the number of simulations needed to study a wide range of canal control scenarios. Solution hydrograph features of interest include peak flow and depth and duration of the computed transient. Initial results show that computed hydrographs can change substantially within certain ranges of the governing parameters but are less sensitive in other ranges. Research results will help identify conditions under which our ability to control canal flows would felimited and, guide future development of practical control systems.