SIMPLE OPTIMAL DOWNSTREAM FEEDBACK CANAL CONTROLLERS: ASCE TEST CASE RESULTS

Authors: Clemmens, Albert; Wahlin, Brian

Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2003
Publication Date: 8/1/2003
Citation: Clemmens, A.J., Wahlin, B.T. 2003. Simple optimal downstream feedback canal controllers: asce test case results. Journal of Irrigation and Drainage Engineering. 130(1):35-46.

Interpretive Summary: Demand for water in the western United States now significantly exceeds available supplies, especially when considering the water needed for environmental purposes. Agriculture's share of available water is likely to decrease in the future. Agricultural water purveyors are being pressured by other water users to improve water measurement, control, and accounting, while their water users are demanding more flexible water deliveries so they can compete in the marketplace and implement water conservation measures on farm. Operation of irrigation-water delivery systems can be improved by providing canal operators with better tools for determining control actions. One such tool is computerized automatic control of canal gates. This technology has proven to be too complex for application by irrigation district personnel and consultants. This paper presents simulation results from application of a new method for the automation of irrigation canals on a set of test cases previously established by the American Society of Civil Engineers. These results should make the application of canal automation more straightforward. Use of these methods by irrigation districts, consultants, and the Bureau of Reclamation should result in better management of irrigation water supplies, water conservation, and environment benefits.

Technical Abstract: In a companion paper, a class of downstream water-level feedback canal controllers was described. Within this class, a particular controller is chosen by selecting which controller coefficients to optimize (tune), the remaining coefficients being set to zero. These controllers range from a series of simple proportional-integral (PI) controllers to a single centralized controller that considers lag times. In this paper, several controllers within this class were tuned with the same quadratic performance criteria (i.e., identical penalty functions for optimization). The resulting controllers were then tested through unsteady-flow simulation with the ASCE canal automation test cases for canal 1. The restriction placed on minimum gate movement caused water levels to oscillate around their setpoints. Differences between canal and gate properties, as simulated and as assumed for tuning, also reduced controller performance. More centralized controllers, and those that include consideration of pool wave travel times, handle unscheduled flow changes better than a series of local PI controllers. A good compromise between controller performance and complexity are controllers that pass feedback for a given water level to the check structure at the upstream end of its pool (i.e., that which is used for downstream control of an individual pool) and one additional check structure both upstream and downstream.