Siphon-less irrigation systems continue to be installed on co􀆩on farms replacing manual siphon irrigation. However, there has been limited measurement of irrigation performance for bankless irrigation systems in all their various forms. Growers utilising these systems tend to be  comfortable with their new siphon-less systems with their comparisons in water use and yields being maintained, or improved, following the change. A CRDC supported project CSD2201 was completed in 2021-22 with the broad aim to op􀆟mise application of water in a particular tailwater backup system. Informa􀆟on from CSD2201 and the GVIA Keytah System Comparison trial RRDP2004, indicate that the GPWUI from these systems is comparable to other irrigation application systems in use. Research indicates that the water use efficiency from them is influenced more by season than by system type, and that optimising individual irrigation event management of each system is most important.

This CSD2201 trial demonstrated that irrigation performance could be optimised in the first half of the field where the tailwater was not backing up. The existing SISCO evaluation process cannot use data from sensors where water is flowing in two directions simultaneously in an irrigation event, and as such the opportunity 􀆟me in the area where tailwater is backed up, cannot be simulated. Work is being done to understand this and inform future developments of the SISCO model.

The challenge all surface irrigators have when managing individual irrigation events is knowing when to turn-off (cut-off) supply water. That is, what dura􀆟on of inflow should be managed to op􀆟mise the uniformity and reduce excess application, by shutting-off the in-flow with the supply gates on a bay, and shift supply to the next bay. This is important because if the water is stopped too early or too late, it can result in poor irrigation performance with under or over irrigating of the bay or parts of the bay. Increased deep drainage (lower application efficiency) and runoff will occur if over watered. If under-watered the tail drain end or downstream sections of the field may not have its deficit met (lowering requirement efficiency), adversely impacting crop production. The additional challenge when managing tailwater backup bankless systems, is to know when to also open the initially closed tailwater gates to maximise infiltration of tailwater in the bottom part of the field, and minimise excess tailwater pumping. This project is proposing to investigate options to inform gate shut-off with the ai