Patterson ID in Central California has five long, along-the-contour lateral canals that flow northward from a main canal. The main canal operates on downstream control, providing excellent flexibility to heads of the laterals. The lateral canals operate with manual upstream control and have little storage. The classic tail-ender problem existed; spill from the tail end was necessary to avoid under-supplying tail-end customers. To eliminate the spill and to provide better flexibility, a system was designed and constructed to tie the ends of the five laterals together with pipes and pumps, with one central regulating reservoir. The automatic control system allows water to exit a lateral pool by gravity if that particular lateral end has too high a water level. Conversely, if the most downstream pool on a lateral canal drops, a VFD-equipped pump from a downhill lateral automatically supplies the correct flow rate to re-establish a constant water level. The same pipe is used for flow in both directions. Any excess flow from the system as a whole is automatically routed to the reservoir. Any deficit from the system as a whole is removed from the reservoir. The complete system is monitored by SCADA, so operators know where excesses or deficits occur, and can adjust flows at the heads of the laterals to compensate for mismatches at the ends of the laterals. The system has worked successfully for three irrigation seasons. The paper describes the control philosophy, design, costs, challenges, and benefits.
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