SCIENTISTS are confident they can turn around surface irrigation's reputation as a wasteful system of water application and transform it into a highly efficient system equal to sophisticated piped and pressurised options.
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Researchers at the University of Southern Queensland, Toowoomba, are using automation and refined management techniques to squeeze new-found efficiencies out of traditional flood- irrigated row crop and permanent bed irrigation systems.
Professor of irrigation engineering at the university, Rod Smith, said the ultimate aim of the work was to have surface irrigation recognised as a precision system.
"Historically it has a reputation for being inefficient. And that is a well-deserved reputation. It has been and to some degree still is inefficient, but it shouldn't be," he said.
Prof Smith said, if surface irrigation systems could be developed that dramatically reduced current levels of water wastage, it would give the vast majority of farmers who were set up with surface irrigation the assurance of being able to continue with those systems.
"Many are having to make the decision of whether to stay with surface or move to a pressurised system, with politicians and others suggesting they move to the 'efficient' pressurised system," he said.
"Managed properly, pressurised systems will deliver water efficiency and reduce labour costs but they require more capital and commit people to huge energy costs far into the future.
"So all we have to do with the surface system is beat that."
Prof Smith said that, through automation and better management practices, surface irrigation could deliver the same labour and water savings with none of the ongoing energy costs of pressurised systems.
"The challenge is to do all that at a capital cost that beats the pressurised system," he said.
Prof Smith said work focusing on surface irrigation systems started in the 1990s, mainly in cotton and sugar in the north and the permanent bed farming systems of south-eastern Australia, where the initial objective was to evaluate system performance.
"The story back then was not a pretty one. The cotton and sugar industries had average (surface irrigation) efficiencies around 50 percent. But there was a range of efficiencies from 10 and 20pc up to incredibly high efficiencies close to 100pc, which meant there were good irrigations and bad irrigations," he said. "It became readily apparent that there were some easy gains to be picked up just by changing practices."
Prof Smith said the first significant advance was achieved by increasing flow rates and reducing irrigation times, which moved efficiencies up to an average 70pc "a 20pc gain for virtually no cost".
He said much of that was achieved through the development in about 2000 of the Irrimate system, which was an evaluation tool delivered primarily in the cotton industry through a group of consultants.
"While that service still exists, it has virtually died on the grounds that quite a number of people in the cotton industry employed it and quite a number looked over the fence and adopted the same practice. So in effect the cotton industry as a whole has benefited from it," he said.
He said that, despite the gains, achieving average efficiencies of about 70pc still fell short of the 85pc-plus target needed to match alternative systems. "So we had to get smarter. That leads us to the allied fields of automation and smart adaptive control of irrigation systems. That is where our current work is taking us," he said.
Prof Smith said the work now focused on adding 'smarts' to the commercial systems of automation that already existed.
He said a major project funded by the Cotton Research and Development Corporation had been set up to combine the real-time 'smarts' developed by researchers at USQ with one of the commercial automation systems.
"The idea is to do the Irrimate evaluation while the irrigation is happening," he said. "We have a sensor at the halfway point which senses how the flow is moving down the field early in the irrigation to give us time to do the things we need to do. We then do the appropriate simulation work, which predicts when the irrigation should be stopped to give the best outcome.
"That signal is sent to the control system which turns it off at the appropriate time."
Prof Smith said the next stage in the process would be to add seasonal management capability to the system that made the decision when to irrigate and how much to apply.
