More water is used for irrigation in Victoria than for any other purpose. 60 to 80 percent of the water we use is for growing crops – either food we eat ourselves like fruit and vegetables, or food we grow for our animals like grass for dairy cows. In fact more water is used for dairy produce than for any other crop – around 50% of water used for irrigation in Victoria goes into food for cows, mostly for milk production.
Most irrigation takes place in northern Victoria using water from the Murray and the Goulburn Rivers. Water is stored in dams across the region and is delivered to farms through thousands of kilometres of irrigation channels. Delivering water by gravity in an almost flat landscape is an extraordinary feat of engineering, but the system is inefficient and loses billions of litres of water every year to evaporation and seepage even before water reaches its destination. For example, Kow Swamp is a small/medium size storage basin, one of hundreds in the region, yet it loses about the same volume to evaporation every year as the city of Bendigo uses. Downstream in the Sunraysia irrigation area water is delivered to properties for fruit and grape growing by pipes and pumps.
Irrigation occurs in other parts of Victoria as well. There are public irrigation districts on the Macalister River in Gippsland and at Werribee and Bacchus Marsh using water from the Werribee River. In addition many farmers pump straight from rivers or from groundwater under licence and irrigation can be seen just about anywhere in the state except the Mallee where there just isn’t enough water.
Because irrigation is such a big user of water it has a major impact on river systems, and many rivers give up half or more of their water for irrigation with serious implications for their health. All Victoria’s rivers in the Murray-Darling Basin that supply water for irrigation (the Murray, Goulburn, Broken, Loddon, Campaspe, Wimmera, Avoca, Ovens, Mitta Mitta and Kiewa) are rated in poor or very poor condition by the Sustainable Rivers Audit . We need to be asking some serious questions about our irrigation practices and if their impact on rivers is acceptable.
The development of irrigation areas has been based on the availability of water, not the suitability of the soils or any other criteria. As a result some land under irrigation is only marginally suitable and the financial return on the water use is low. The area under irrigation is actually contracting in Victoria.
The CSIRO has devised a method for determining which areas are best for irrigation. Its ‘traffic lights’ approach looks at soil, environmental and location characteristics to assign land in irrigation areas to three planning zones – green for sustainable irrigation, amber for environmental restoration including biodiversity and carbon plantings and rural amenity, and red for transition to dryland agriculture. A pilot study in the Torrumbarry Irrigation Area showed that applying the approach would increase agricultural profitability by 24%, reduce the cost of running the irrigation system and return around 20% of the water used ( 60 GL) to the environment. In addition stopping irrigation in the red zones would reduce salinity and save about $50 million in salinity mitigation costs over the next 30 years. Rational planning provides multiple benefits.
The traffic lights approach is being used in northern Victoria in connection with the irrigation modernisation program currently underway, but only in modified form. The key factor in determining which areas are to retire from irrigation is proximity to the main irrigation channels – the closer you are to a channel the more likely you are to be offered to join the modernisation program, irrespective of land suitability or environmental considerations. If these latter considerations were brought into account the benefits of modernisation in terms of river health and ecosystem services could be much greater.
Irrigation is an inefficient process as only a fraction of the water that is released from a dam actually gets used by the crops that are the ultimate recipients of the water. Water is delivered to farms by a network of channels and it can take several days for water to reach its destination. There are many ‘delivery losses’ on the way – leakage, seepage and evaporation. In old systems like the Wimmera-Mallee channel system (fortunately now replaced by pipelines) as much as 80% of the water was lost before it ever got to the farms. In the Goulburn-Murray Irrigation District about 30% of water is lost in transmission and current modernisation programs are designed to reduce that by about half.
Further losses occur once irrigation water reaches a farm. In Victoria over half of irrigation water is used for surface or flood irrigation , that is literally flooding paddocks to grow pasture and other feed for cows. The technique has become more sophisticated in terms of levelling paddocks, the timing of irrigation and volumes of water supplied, but at heart it is a technology that has been around since the time of the Pharaohs with a limit on efficiency. Spray and drip systems can deliver water much more efficiently to the root zone of the crops and are used for growing fruit and vegetables where profit margins are higher. But they have problems of their own in terms of energy demand and the need to clear paddock trees and other vegetation to accommodate booms and centre pivots. With any system over-irrigation can lead to a rise in the water table and associated salinity issues.
Governments are investing heavily in irrigation modernisation programs –their preferred method of returning water from consumptive use to the environment. Projects include rationalising and reducing channel systems, reducing leakage and replacing regulators, gates and meters. Modernisation is seen as having a positive impact on regional economies. This is undoubtedly true but it is also expensive, time consuming and uncertain in its outcomes. Water savings have to be verified and in dry years may be much less than predicted. On-farm efficiency measures are popular with farmers and can yield significant water savings that can be returned to the environment. However they also entrench irrigation practice and if not properly planned may result in public money propping up irrigation in areas and by methods which are not sustainable in the long term. They may also result in an increase in water use as farmers benefit from increased productivity.
Irrigation results in a big increase in the value of agricultural production compared to dryland enterprises without irrigation. However some crops add much more value than others.
Let’s have a look at irrigated agriculture in the Goulburn valley as an example. The dairy industry is a big contributor to the regional economy and is the biggest user of water. However it does not produce the greatest value per unit of water used. Other commodities such as fruit and nuts, grapes and vegetables create up to six times as much value per megalitre of water used and are mainstays of the economy. Nurseries create the highest value of all but are relatively niche business, and we can’t live on cut flowers and turf.
Irrigated agricultural production in the Goulburn valley, 2005-06
|Commodity||No of businesses irrigating||Volume of water used (ML)||Gross value of irrigated agricultural production ($ m)||$ produced per ML water used ($/ML)|
|Fruit and nuts||319||40,216||208||5,172|
|Vegetables for human consumption||61||9,747||46||4,719|
|Sheep and other livestock||503||34,989||14||400|
|Total (all commodity groups)||2,396||629,507||712||1,131|
Transferring water use from dairy to fruit, grapes and vegetables would greatly boost the value of production in the Goulburn valley. Obviously there are many other factors at play which are beyond individual control – historical, demographic, government policy, export markets, prices and consumer demand to name but a few. Currently fruit canneries like SPC Ardmona, owned by Coca Cola Amatil, are reducing their tonnage and cancelling grower contracts. There is also much speculation about the longer term future of the company. However the longer term differential between different products remains and in a system where water is adequately valued this differential should drive change in the crop mix and shift production towards higher value commodities.
The long years of the Millenium drought brought an important lesson for agriculture – it is possible to do more with less water. The value of irrigated agricultural production went up while the volume of water used went down.
Economists call this ‘decoupling’ where economic growth is delinked from increasing resource use. We call it doing more with less. Although in this case the irrigators have had a little help. Billions of tax-payer dollars have been pumped into modernising irrigation infrastructure, farmers have adopted innovative ways of doing business and further millions of dollars have been invested in research into crop choices, irrigation methods and schedules .
Put all this together and we should no longer have to make a choice between irrigation and river health. It should be possible to achieve the vision of the irrigation modernisers and create ‘productive and growing businesses that add value to water, by producing twice as much from half the amount of water’ . Sustainable irrigation has a vital role to play in the regional economy but it has to achieve the ‘factor four’ productivity gain to be viable in the long term. There are many ways of getting there but the basic recipe is this – highly efficient irrigation growing valuable crops in the areas that are most suited to it. Anything else and our rivers will continue to suffer as a result.