Applying Water-Level Difference Control to Central Arizona Project

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 controls with a controlled-volume approach. In this paper, the writers examine the potential application to the CAP canal of water-level difference control, a new feedback canal-control method. The main objective of this method is to keep the downstream water-level errors in equal pools. The control model is a multiple input and multiple output (MIMO) 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 show that 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 h 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. The writers suggest that this water-level difference-control method is quite promising, especially for large canals.