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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Water Management and Conservation Research » Research » Publications at this Location » Publication #259190
Title: Applying Water-Level Difference Control to Central Arizona Project

Author
item GUAN, G. - Wuhan University
item Clemmens, Albert
item KACEREK, T. - Central Arizona Project
item WAHLIN, B. - West Consultants

Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2011
Publication Date: 1/28/2011
Citation: Guan, G., Clemmens, A.J., Kacerek, T.F., Wahlin, B.T. 2011. Applying Water-Level Difference Control to Central Arizona Project. Journal of Irrigation and Drainage Engineering. 137(12):747-753.

Interpretive Summary: The Central Arizona Project (CAP) has been supplying Colorado River water to Central Arizona for roughly 25 years. Water is pumped up from the Colorado River into a canal where it flows by gravity, until it reaches a lift station where it is lifted again into a higher canal. The canal has 14 lift stations that pump the water up a total of 885 m. In the sections of canal in between lift stations, check gates are used to control water levels for delivery gates. Operators can adjust gates from a central location. CAP also has an automatic control system that can adjust these check gates automatically. Operators commonly turn off the automation because they do not like its performance. In an earlier paper, one of the authors developed a new control method for main canal that controls the difference in water level errors in adjacent canal pools, where water level errors are the difference between the actual and desired water levels. In this paper, the authors use a simulation model of canal flow for a segment of the CAP canal between two lift stations. Automatic control with the CAP control and the water level difference control are compared for situations commonly experienced by operators. The difference control method is shown to have better control, provided that large flow changes are properly scheduled. These results will be of use to irrigation and large water districts, the Bureau of Reclamation, and consultants.

Technical Abstract: The Central Arizona Project (CAP) has been supplying Colorado River water to Central Arizona for roughly 25 years. The CAP canal is operated remotely with a Supervisory Control and Data Acquisition (SCADA) System. Gate position changes are made either manually or through the use of automatic control with a controlled-volume approach. In this paper, we examine the potential application to the CAP canal of a new feedback canal control method: water level difference control. The main objective of this method is to keep the downstream water-level errors in all pools equal. The control model is a MIMO (multiple inputs and multiple outputs) system and the controller is solved as a Linear Quadratic Regulator (LQR). A feed-forward routine called volume compensation was also used to route the flow changes. Simulation results shows this method is stable and can deal with different kinds of changes relatively quickly. For small changes, the water level difference controller can operate well even without routing flow changes. For large flow changes, the water level difference control alone can take up to 12 hours to stabilize all water levels. Performance is greatly improved with the inclusion of the feed-forward routine. This new method provides better water level control than the current method, and it is much less sensitive to errors in gate calibration. We suggest that this water-level difference control method is quite promising, especially for large canals.