Irrigation Evaluation

Why evaluate irrigation systems?

Water is increasingly scarce, even in New Zealand. We need to be very aware of maintaining our natural water bodies, and using the available water as wisely as we can. Irrigation uses about 80% of the fresh water extracted in New Zealand (though less than 10% of available recharge water annually). Irrigation adds around a billion dollars to farm-gate value each year, so it's worth doing. Further irrigation development will make an even larger contribution to our country's wealth. But in many cases, that will require storage and that adds cost. To provide the benefits we want from irrigation, it needs to be efficient and effective. That requires good system design and good system management. Irrigators need to know how much water their systems are applying and how efficient the system is. And they need to know why it is not working if they are to fix it.  Having worked in irrigation for many years, we knew that system performance was highly variable. There are many causes, ranging from design flaws, through poor installation, component failure and maintenance.

How to evaluate?

Each type of irrigation system, pivot, traveller or drip, functions differently. Each is affected more by different factors. So a different method of assessment is needed for each case. Fortunately, there are many performance indicators that are common, so although we may need to measure systems in different ways, the performance of systems is easily comparable. We focus evaluations on a set of key indicators:
  • is the system applyng the expected depth of water?
  • is it applying the water evenly (uniformly)?
  • is it applying the water at a rate that the soil can accept?
  • is the energy use reasonable?
  • what is causing any non-performance? 
To formalise the evaluation process, we developed the Code of Practice for Irrigation Evaluation for Irrigation New Zealand with support from the Sustainable Farming Fund. The Code sets out protocols and procedures for evaluating common types of spray irrigation. It is supported by IRRIG8, a software packeage to help process data. The procedures were tested on a wide range of New Zealand farms, with old and new irrigation systems. The results, unfortunately, confirmed the need for the Code and software! The Code of Practice for Irrigation Evaluation is backed by a New Zealand National Certificate. 

Is there a simpler process?

Yes! There's IRRIG8Quick . . . We believe irrigators should calibrate their systems at least annually. And for that we developed IRRIG8Quick, a series of do-it-yourself, in-field irrigation system checks.  With downloadable guidelines and worksheets, each check should only take a couple of hours to complete and the knowledge gained is enormously useful. IRRIG8Quick simplifies the procedures, and gets 80% of the value for 20% of the effort.  

So why get complicated?

While an IRRIG8Quick calibration will tell you IF the system is performing adequately, it won't tell you WHY. That's where the full evaluation comes in; it tells you in more detail not only how well your system (and management) is working, it also tells you which factors are causing poor performance. The New Zealand Code of Practice for Irrigation Evaluation sets out the protocols. To make data processing more efficient we prepared IRRIG8, a comprehensive Irrigation System Evaluation software package.  Once field work for an evaluation is completed, IRRIG8 crunches the numbers collected, and generates performance indicator values.  IRRIG8 does the many repetitive and detailed calculations automatically, and generates editable reports. IRRIG8 is best used by trained people. It is essential to gather, record and enter the right data in the right way, and an understanding of system management, pressure, flow and hydraulics is required. We provide training and assessment through Agribusiness Training. (Expect a week of face to face tuition, and a lot of homework.)

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