In this section:
Full Report
Introduction
Australia is the driest continent on earth, and as a result, water is vital to the survival and prosperity of the nation. As the title of this conference indicates, in Australia "Water Is Gold". Water resources for human consumption, agricultural production and environmental needs are very limited. Current calls for efficient use of those resources recognise the need to manage Australia’s water resources carefully to ensure their continued availability and high quality.
In relation to water used for irrigation, there is a lot of talk on the subject of irrigation efficiency and the need to improve efficiency within the irrigation industry. In spite of this interest in the subject, it is often difficult to identify exactly what different people mean when they use the term irrigation efficiency. Many of those involved in the debate appear to have only a general idea of what it is that they are referring to and trying to improve.
It is not surprising, then, that irrigators are confused by the various calls they hear to "improve your irrigation efficiency". How can they identify their level of efficiency when those calling for improvement use different measuring sticks. What is needed is a clear understanding and a consistent methodology for measuring efficiency of irrigation.
Just as important, however, is the provision of information about how to improve efficiency. Knowing that efficiency should be improved is of little use if there is poor information available to help irrigators to institute improvements.
Finally, simply informing someone of how they can become more efficient is not the best way to motivate them to do so. Somehow, improving efficiency of irrigation must be made attractive.
An irrigation benchmarking study was undertaken in the Riverland and Sunraysia regions. The study used the benchmarking approach to compare the efficiency of irrigation of a sample of irrigators, identify the best performers across a range of efficiency indicators, and identified a suite of best management practices for irrigation which will assist other irrigators to improve their efficiency. In addition, techniques are discussed for improving the level of uptake of more efficient irrigation practices.
Defining irrigation efficiency
We must first deal with the problem of defining efficiency of irrigation. The first problem encountered is the level or scale at which it is measured. Efficiency can be measured at the scale of a whole catchment, at the individual plant scale, and at almost any level in between. The scale of measurement depends on the focus of the person doing the measuring.
The scale of measurement is of critical importance in tackling the issue of improving efficiency, and must be matched to the target audience. For example, when measuring on-farm efficiency, too broad a scale makes it difficult to determine what the causes of low efficiency are and what can be done to improve the situation. Going to a smaller scale excludes the consideration of wider issues, such as delivery system losses and inefficiencies, but is necessary to clearly identify real opportunities for improvement at the individual property/manager scale.
This raises a second problem with defining efficiency of irrigation, any definition will depend to a large degree on the outlook of the person producing the definition. Those managing the supply of water tend to see efficiency simply in terms of losses in the delivery system, or the gross amount of water consumed by each of their customers as compared to some average or ideal figure. Irrigators are more interested in how much product, or perhaps how much profit, they can produce with a given amount of water. Finally, those involved in resource management are more interested in reducing wastage of the resource, especially where such wastage has negative off-site impacts on the environment.
As all of these factors are important in the larger picture, no one definition of efficiency is completely appropriate. If a realistic attempt is to be made to quantify and compare efficiency of irrigation, a range of measures or indicators is required, in order to capture all of the important factors involved.
Benchmarking on-farm irrigation performance
As discussed above, it is important to clearly identify the scale and focus of measurement. This study deliberately focussed on irrigation performance on-farm, ignoring sources of inefficiency that are beyond the immediate control of irrigators.
The study utilised a benchmarking approach to data collection, manipulation and comparison. This embodies a number of variations from a traditional experimental study or a simple industry survey. Benchmarking methodology focuses on comparisons with the aim of identifying the best performers within a sample and, importantly, identifying the reasons for their superior performance. Benchmarking is not concerned with where the sample as a whole lies, rather it is interested in where the top end of the sample lies, and how other members of the sample can move toward that level of performance. The identification of best management practices is an integral part of this process.
The crops included in this initial study were oranges, winegrapes and potatoes. Full results for the three crops are published in three reports (Skewes and Meissner, 1997a; Skewes and Meissner, 1997b; Skewes and Meissner, 1998) Data was collected from a series of sites across the Riverland (SA) and Sunraysia (NSW & Vic), by a combination of interview and field evaluation. The interview was used to collect information about site location, planting details, irrigation system setup, irrigation supply, irrigation management, general crop management and production. The field evaluation allowed an assessment of the operation of the irrigation system, as well as field checking of soils and general management information.
A number of indicators of irrigation performance were developed. All indicators were quantitative, with clearly defined units. The value for each indicator was calculated at each site from the data collected in the interview and field evaluation. The performance indicators used allow comparison of the performance at each site for each indicator.
Numerical benchmark goals for each indicator were not set, for two reasons. First, if numerical goals are set, once an irrigator reaches the goal, there will be no incentive left to continue to improve. Benchmarking is the process of continual measurement and improvement, and the "industry best" level of performance should continue to rise over time.
The second reason for not setting numerical goals is that the purpose of the project is not to grade irrigators as "acceptable" and "unacceptable", by comparison to some goal, but to compare a number of sites in order to identify the top performers, and then to analyse their management in order to identify best management practices.
The problem which arises in identifying top performers by the benchmarking method is that each site performs differently for different indicators, relatively better for some and not so well for others. Some people may argue for the precedence of one indicator over others, and this usually reflects their particular outlook on the irrigation industry. This study took the approach that all indicators are equally valid, and what makes for a good irrigator is someone balancing all aspects of the irrigation complex, ie. water use, production and wastage/off-site impact.
These irrigators were interviewed to elicit further information about their management practices and philosophies. A good degree of overlap in approach to irrigation occurred across the whole group, and this assisted in the identification of a suite of best management practices for irrigation.
Indicators of irrigation performance
The indicators used are outlined below. Figures 1 to 3 present data for three of the indicators outlined below, for the sample of citrus sites (from Skewes and Meissner, 1997a). Note the wide variation in performance between sites for each indicator.
The lighter shaded, numbered bars in Figures 1 to 3 designate the 5 case study sites identified from this sample. Note that the case study sites are not always the top performers for each indicator, but are consistently near the top across all indicators.
Yield (t/ha): Yield per hectare is the traditional way of representing the performance of an agricultural enterprise. While it is of immediate interest to irrigators, it can sometimes give a false impression of efficiency, when other inputs are not being used efficiently.
Figure 1: Water Use Efficiency (t/ML)
Water Use Efficiency (t/ML): Water use efficiency (Fig. 1) is defined as tonnes of produce per megalitre of irrigation used in the production cycle. Even if yield per hectare is high, using excessive amounts of irrigation water to achieve that high yield is not an efficient use of a limited resource. In many areas of Australia, and in particular in the Murray-Darling River Basin, availability of water is the major limitation to new horticultural development. In most areas, there is sufficient land available in reasonable proximity to the river, but there is no new water available to apply to that land for growing crops due to the cap placed on further diversions of water from the Murray-Darling system. It could be argued, on this basis, that water use efficiency, or yield per megalitre of irrigation, is far more important than yield per hectare in making the most efficient use of the limited resources available to irrigated horticulture.
The range of values recorded for water use efficiency is quite wide, reflecting a large variation in both tonnes of fruit produced and depth of irrigation applied across the course of the season. The case study irrigators generally scored well, but ranged down toward the middle of the sample.
Tonnes of Fruit Packed per Megalitre (t/ML): Tonnes of fruit packed measures the relative quality of the product of irrigation. The use of this indicator is obviously limited to crops which are packed for fresh fruit markets. Producing large tonnages of poor quality fruit is not necessarily a good use of a limited resource. Packable fruit is the clear focus of the Australian citrus industry, and therefore the production of packed fruit per unit of water is a much better indicator of productive use of water than gross tonnes produced per unit of water.
Return per Megalitre ($/ML): Return per megalitre (Fig. 2) assesses not only the amount of produce, but also the quality of the produce, measured by its value. A standardised structure of returns was applied to the tonnages of produce in each of a range of quality classes (specific to each crop), to compare the overall return on irrigation water.
Figure 2: Gross Return per Megalitre ($/ML)
The range of values recorded is even greater for this indicator than for water use efficiency. Much of the difference has to do with the quality of fruit produced, and there are some irrigators in the sample who are producing a high percentage of quality fruit. The case study irrigators all scored very well for this indicator.
Cost of Water per Tonne of Fruit ($/t): Cost of water per tonne of fruit measures the monetary value of irrigation water used to grow a tonne of fruit at each site. It reflects not only how much water was used per tonne of fruit, but also the cost structure of the site, and the likely sensitivity of the site to increases in the cost of water.
Return per Dollar Water Input ($/$): Return per dollar water input takes return per megalitre another step, by making a direct comparison of dollars spent on water with dollars returned from the use of that water. Obviously a low return per dollar water input is of concern, as it impacts directly on the profitability of the enterprise.
Irrigation Efficiency (%): Irrigation efficiency (equivalent to application efficiency as defined by the On-Farm Irrigation Committee of the Irrigation and Drainage Division, 1978) assesses the relative percentage of irrigation water applied to the crop that was directly used by the plants for evapotranspiration. High values for irrigation efficiency reflect low volumes of drainage produced throughout the irrigation season.
Yield per Volume of Drainage (t/ML): Yield per volume of drainage (Fig. 3) is similar to water use efficiency, except that it relates the yield produced to the volume of drainage produced, rather than to the volume of irrigation applied. The logic behind this indicator is related to the understanding that some drainage is required for leaching of salt from the rootzone, but excessive drainage is counter-productive. If drainage is necessary, we can measure the positive utility of that drainage by comparing it to the level of production associated with its generation. High yields per drainage volume indicate a high ratio of return (production) to cost (drainage). Low yield per drainage volume indicates a poor return to cost ratio, and suggests that the levels of drainage produced are excessive.
Figure 3: Yield per Volume of Drainage (t/ML)
There is a great range in values for yield per volume of drainage, from 4.99 to 136.5 t/ML. All of the case study sites scored very highly, all producing over 80 t/ML, but approximately half of the sites produced less than 30 t/ML of drainage.
Cost of Drainage per Tonne of Fruit ($/t): The final indicator further explores the relationship between drainage and production, by assessing the cost of purchasing and pumping the volume of water that is lost to drainage per tonne of fruit produced. It does not give any indication of the environmental costs associated with the drainage produced. The true costs associated with the impact of drainage water on a whole region basis would be far greater than indicated here.
This list of indicators is by no means meant to be definitive. These indicators, along with a few others, were seen to be important in this particular study, but different indicators may well be more appropriate under other circumstances. It is important to note, however, that the indicators used cover a wide range of important issues in irrigation, from the volume and value of water used, to the amount and value of crop produced, and including an assessment of the amount and value of wastage occurring in the system.
Irrigation best management practises
The case study irrigators from all crop samples were interviewed and a suite of best management practices for irrigation developed from their responses.
The best management practices outlined below are deliberately non-prescriptive, that is they do not set out to tell irrigators exactly how they should go about managing irrigation, or exactly what tools they need to use. These decisions are for individual irrigators to make, and will vary according to a whole range of site and irrigator specific factors.
Instead the best management practices provide guidance on what are the important principles that make for best practice in irrigation, as follows:
BMP 1: Rate irrigation highly within the management system.
All case study irrigators cited irrigation as either one of the most important factors in their production system, or the single most important factor. For example, for one of the case study irrigators, "Irrigation is always number one". When irrigation is seen as a low priority it is no surprise if irrigation performance is low, and likewise it is not surprising that the best irrigators all place irrigation as a high priority in their growing system.
BMP 2: Get to know the soils on the property.
Efficient irrigation is very difficult without good information about the capacity of soil to hold water, and where in the soil profile the roots of the crop are. After augering holes across the property to look at rootzone depth, one case study irrigator said, "You feel a bit more comfortable, ... the top might be drying out a bit, but you know that its down there, getting the water from down below".
BMP 3: Design And Maintain Irrigation Systems Correctly
Poor irrigation system operation can make good irrigation management almost impossible. A number of the case study irrigators cited irrigation system setup, age, and maintenance as limiting factors in their ability to manage irrigation as well as they would like. The irrigation industry in Australia operates according to a set of standard practices for irrigation system design and operation. All new irrigation system designs should adhere strictly to these guidelines. Existing irrigation systems should undergo regular checking and be maintained to these same guidelines.
BMP 4: Monitor all aspects of each irrigation event.
This is best described by a quote from one case study irrigator, "Monitoring is split into many things,....before the irrigation, ....during the irrigation, ....and after the irrigation....". The simple decision of when to irrigate is only part of the whole story. Monitoring of where water is going, both during the irrigation, by measuring system performance and uniformity of application, and after the irrigation, by assessing under- and over-irrigation, is vital to efficient irrigation.
BMP 5: Use objective monitoring tools to schedule irrigation.
All case study irrigators used at least one objective monitoring tool, usually a soil based device, in determining the timing of irrigations. The tools used varied widely, from tensiometers and hand assessment of soil water through to sophisticated tools such as the Neutron Probe and EnviroSCAN®. The important thing, however, is that they measured something, rather than relying on intuition, the calender, or when the neighbours watered. An important point about scheduling tools is that they must be appropriate, both to the crop and irrigation system they are used with, and also to the irrigators who must maintain them and interpret the data provided by the tool.
BMP 6: Use more than one tool for scheduling irrigation.
All of the case study irrigators used a range of information sources in making the decision on when to irrigate and how much to apply. Typically, much of the decision relied on one particular tool, but other factors were taken into account. The most common and simplest included digging holes to check soil water, observation of the appearance of plants, and the checking of testwells or drain flows after irrigation and subsequent adjustment in practice at the next irrigation.
BMP 7: Retain control of irrigation scheduling.
With modern technology, it is possible to set up irrigation systems to operate entirely automatically, based on the readings from a probe or a set of probes. Along the same lines, it is easy to allow a consultant to dictate the irrigation schedule, based on his or her measurements, or to blindly irrigate because the tool being used indicates that it is time to. The case study irrigators all firmly held onto control of irrigation scheduling, that is, they took into account the data from the scheduling tool or the recommendation of the consultant, but retained the power to vary the schedule using their own judgement and the use of other tools.
BMP 8: Remain open to new information.
The case study irrigators cited a range of different ways in which they obtained access to information about irrigation. All of them saw this process as important, and were willing to talk to anyone with something to offer, even if they later discarded it as not applicable to their situation. In the case of larger, corporate operations, employee education was seen as important, as was encouraging the employees to make a meaningful contribution toward management decisions.
One extremely interesting observation was that the top performing irrigator in the citrus sample and the top performing irrigator in the winegrape sample have both been in the horticultural industry for only a short time (around 5 years). Both came into the industry with no prior knowledge, and learnt by asking others and seeking out information from any source available.
Improving efficiency of irrigation
In the introduction to this paper, reference was made to three requirements of irrigators in regard to efficiency of irrigation, suitable definitions of efficiency so that they can measure their performance, information to allow them to improve their performance, and the motivation to tackle the subject. So far we have addressed two of these issues. We have identified some suitable and useful definitions of efficiency that irrigators can use to evaluate how efficient their irrigation is, and we have provided a suite of best management practices which provide information to help irrigators to improve their performance. The third issue of motivation is still vital, however, and so far unanswered.
Or is it? The process of benchmarking by which we have arrived at our efficiency comparisons and by which we have identified a suite of best management practices can also be a powerful tool to motivate irrigators to measure and improve their performance.
In many cases irrigators do not know how they rate in regard to crop management, including irrigation management. The benchmarking process provides a framework and methodology for benchmarking performance, which irrigators can use themselves to make their own benchmarking comparisons. This is an attractive proposition for two reasons.
Firstly, people like to look over the fence, to see how they compare with their neighbours. Irrigators are no exception. By providing simple, easily measured indicators, this methodology provides an easy and legitimate means by which meaningful comparisons between properties can be made. Such comparisons in themself can provide a strong incentive to improve, through the natural urge to "keep up with the Joneses".
Secondly, by encouraging irrigators to spend time and energy going through the benchmarking process, there is far greater likelihood that they will actually make changes as a result. The effort put into benchmarking by irrigators is a large incentive to make meaningful changes in management practices, so as not to waste the effort already expended. This principle is sometimes referred to as "sweat equity", or ownership through participation.
WHERE TO NEXT?
Current work is directed at developing a benchmarking package which will provide the tools necessary to allow irrigators to conduct their own benchmarking comparisons. One model for the use of the package is for benchmarking comparisons to be conducted as a group exercise, making use of existing groups of irrigators such as Citrus Information and Technology Transfer Groups (CITTGroups) and Property Management Planning groups, as well as bringing together groups of interested irrigators especially for benchmarking.
We cannot rely completely on benchmarking to deliver improvements in efficiency of irrigation at the property level, however. Additional strategies are needed in order to motivate irrigators to improve their practices. Irrigators should be rewarded for their efforts. Such rewards could come either as recognition (eg. certification) or in monetary incentives (eg. premium prices for produce or reductions in water rates). This strategy fits neatly with current trends in industry towards Quality Assurance (QA) programs, where irrigation management to a particular set of standards could make up one part of the QA program
References
On-Farm Irrigation Committee of the Irrigation and Drainage Division, 1978. "Describing Irrigation Efficiency and Uniformity", Journal of the Irrigation and Drainage Division 104:35-41.
Skewes, M. and T. Meissner, 1997. Irrigation Benchmarks and Best Management Practices for Citrus, Technical Report, No. 258, Primary Industries and Resources SA, Adelaide, South Australia.
Skewes, M. and T. Meissner, 1997. Irrigation Benchmarks and Best Management Practices for Winegrapes, Technical Report, No. 259, Primary Industries and Resources SA, Adelaide, South Australia.
Skewes, M. and T. Meissner, 1998. Irrigation Benchmarks and Best Management Practices for Potatoes, Technical Report, Primary Industries and Resources SA, Adelaide, South Australia.
