Context:
Leathorn Dairies in Newry, West Gippsland, demonstrated just how important basic maintenance can be in improving irrigation efficiency. Over a two-year period, Agriculture Victoria performed two irrigation efficiency assessments on one of their centre pivot irrigation systems.
One assessment was conducted before and one after machine maintenance was carried out. This helped evaluate how routine upkeep can influence water application accuracy and distribution uniformity.
Pre maintenance:
During the first assessment, catch cans were placed every three metres along a transect of the pivot, beginning at the central tower. Pressure gauges were also installed on the sprinkler outlets of the first and last spans to monitor system pressure. The pivot was set to apply 13mm of water, and the volume collected in each catch can was recorded and compared to the target.
Results revealed significant variation in application rates – ranging from 7mm to 21mm – and pressure levels were found to fluctuate. Consistent pressure across the pivot is crucial for maintaining optimal droplet size, spray pattern, and application rate, which directly impacts water distribution uniformity.
Several sprinklers were malfunctioning or blocked, and an incorrectly installed end-gun pump was contributing to unstable pressure readings. Overall, the pivot delivered water with only 75% accuracy relative to the target application rate (Figure 1), highlighting a need for system maintenance.
Figure 1, First system assessment
Post maintenance:
After cleaning or replacing the affected sprinklers and correcting the end gun installation, a second assessment was carried out.
This showed a marked improvement: application rates ranged from 10mm to 15mm, with an average accuracy of 93% (Figure 2). These results reflect a 13% improvement in application accuracy, demonstrating the value of regular system assessment and maintenance alongside VRI technology.
Figure 2, Second system assessment, post maintenance
These irrigation assessments were conducted as part of a centre pivot variable rate irrigation (VRI) demonstration trial. Leathorn Dairies hosted this demonstration on their property between June 2022 and December 2024, with the support of the Sustainable Irrigation Program. For more information about Leathorn Dairies’ learnings in integrating VRI, check out the YouTube video or the full report.
This funding is available through the Victorian Government’s Sustainable Irrigation Program, and delivered in partnership between Agriculture Victoria and the West Gippsland Catchment Management Authority.
