The study was sponsored by the Energy Efficiency and Conservation Authority (EECA) and lines companies of Canterbury and North Otago, and carried out by Irrigation New Zealand (INZ).
It aimed to determine if opportunities existed to improve energy use efficiency of farm systems and operation and looked at dairy, arable and sheep-beef operations.
INZ projects manager Paul Reese said an earlier proposal to work with EECA in 2012 was to complete an industry wide study of irrigation energy efficiency.
“However we soon realised there was not enough information around, so this pilot study has been completed so we can get a larger project going.”
Funding from South Island lines companies means the 14-farm study project has been completed mainly in the Canterbury region, including three Network Waitaki clients in North Otago.
Six of the systems were surface water supplied, and the remaining eight were split between single and multiple-sourced ground water systems.
Determining farms had been a relatively random process, eight dairy farms were included in the survey, and the efficiency assessment was significantly subsidised.
“We were careful that the selection was not biased towards top end irrigators who may have been performing at the top end for efficiency as well. The results also reveal that, out of the 14 farms assessed, there were only two that we found where no improvement could be made.”
In the past a lack of water metering equipment to measure water demand had limited the industry’s ability to audit systems and develop reliable data sets, but this was rapidly changing and helping benchmarks be developed.
The project sponsors aimed to have the findings provide tangible examples of benefits irrigators could gain from investment in capital improvements in systems.
‘The results also reveal that, out of the 14 farms assessed, there were only two that we found where no improvement could be made.’
Reese said the survey evaluated two key areas – the motor, pump and delivery system performance, or the system’s design, and the scheduling of application in terms of pumps being turned on and off at correct times and the depth of water being applied.
Splitting the two areas up helped evaluators determine how much of a system’s inefficiencies stemmed from design, versus management. Four consultancies were contracted to carry out evaluations: Aqualinc Research, Demand Response, Hydroservices and Irricon.
At the beginning of the process irrigators were asked how well they thought their system was running. Responses were mixed, and very few could state how much their water cost a unit.
“When you asked most farmers they would not have put the electricity price and the water use together to work it out.”
Quality data was essential for calculations, and of the 14 properties, five did not have complete water meter data because they were on schemes measuring water take on a scheme basis and not requiring individual metering.
Reese was hopeful that as water meters were now more prevalent, more farmers would use them as much for an efficiency indicator as a “must have” compliance tool, and that use even at an individual scheme member’s property level would become more common.
Farm turnover and time had also meant that some base information had been lost and generally irrigators were not aware of their system’s design operating specifications.
Reese said the pilot study process had been invaluable in identifying some areas for the industry to start addressing, but also in establishing a core of consultancies capable of conducting the complex and time consuming assessments.
“Assessment is an exercise in engineering skills and also in water management, the two are not always shared by the same people, or that widespread.”
INZ is intending to propose a “two level” audit for the wider study.
“It would start with a “first look” to determine if it is a farm that requires a full audit, and if it will benefit in efficiency gains by having that done.”
The average cost of the evaluations was $6193, but varied between systems depending upon how much quality information was available, and the complexity of the farm’s system.
Evaluation identifies key cost issues
The evaluation of irrigation systems in the pilot study identified nine key actions irrigators could take to improve their system’s efficiency.
But for many cases installation of monitoring equipment was recommended, not as a direct means of reducing energy use or increasing efficiency, but to provide better information to track the system’s performance and determine just how efficient it was.
‘Assessment is an exercise in engineering skills and also in water management, the two are not always shared by the same people, or that widespread.’
The study also developed some simple benchmark indicators to provide farmers a guide on evaluating irrigator performance, to help with decisions on capital expenditure to improve systems.
Irrigation New Zealand projects manager Paul Reese said over time changes made to systems can negatively affect their original purpose.
“A big issue with systems is not that the design has been done poorly to start with, but that the system has been changed over time. It has been added to or altered from its original — for example an extra water source or pump added in, only to now have two pumps ‘fighting’ each other to supply water. As things grow organically on properties those original efficiencies get lost or diluted.”
A typical example could be where a RotoRainer was used in the 1970s, and later replaced with a centre pivot to the original main line.
“So that core infrastructure has not changed with the technology, reducing the efficiency that did come with the centre pivot installation.”
The main finding from the project was that soil moisture monitoring was the most common action that would deliver efficiency gains through better scheduling, and was suggested on nine of the properties.
For a relatively low-cost addition, coming in at about $6000-$10,000, soil moisture monitoring delivered a payback within six years with its direct impact on irrigation scheduling efficiency.
For suggested improvements costing less than $20,000, there was an average payback period of 3.8 years, against an average payback of 5.5 years for projects costing more than $20,000.
Reese said the evaluations had shown scheduling, timing and amount of application was an area demanding greater attention.
“There did seem to be more over-watering than under-watering occurring, but it has been hard to put numbers around that.”
Key areas of irrigation efficiency gains
The study revealed some key areas where gains could be made. Of the farms reviewed only one didn’t need to take any of these actions to improve its efficiency. The number of farms requiring action in the pilot study is also listed.
- Headworks alteration (4). These included removing restrictions, resizing and right sizing pipes, installing monitoring points for better tracking of consumption.
- Alter distribution network (5). More direct feed pipes, resize to reduce friction, use higher pressure rated pipes.
- Install Variable Speed Drivers (4). To ensure more efficient matching of motor capacity to demand.
- Reconfigure supply to demand (4). Particularly on multiple interconnected irrigators and pumps, requiring redirecting of supply to match demand where possible.
- Intake improvements (3). Improve existing or replacing substandard intakes.
- Soil moisture monitoring (9). For improved scheduling and precision application.
- Change pumps (3). From replacement to resizing, to removing.
- Change irrigator (5). Combining small improvements to existing irrigators, or changing irrigator type.
- Irrigator evaluation (6). Perform a “bucket test” on regular basis to measure performance and identify weaknesses or inefficiencies in the system.
