Much of Australia's irrigation occurs in the Murray–Darling Basin where over two-thirds of Australia's irrigation water is used to grow food and fibre. Irrigation is used to provide water to farms to supplement natural rainfall.
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Differences in irrigation across the Basin
Most irrigation water use occurs in the 3 large southern catchments of the Murray, Murrumbidgee, and Goulburn–Broken Rivers, where most of the water falls in the Basin and there are major dams to store the water. The Snowy Mountains Hydro-electric Scheme supplements these irrigation storages by releasing water downstream. This water may then be diverted into large canals to deliver water to irrigation areas through thousands of kilometres of gravity-fed channels, or pumped via pipes to farms to provide sprinkler and drip irrigation for crops.
Irrigation also occurs in the rivers of the northern Murray–Darling Basin and elsewhere, but not at the same scale. This is because there is less rainfall and fewer large dams to store water. Irrigators use water in different ways. This includes pumping groundwater, pumping river water into farm dams, or capturing and storing floodwaters behind levees.
Did you know…
- The Basin supports 7,300 irrigated agriculture businesses.
- Water powers $22 billion of primary production across the Murray–Darling Basin each year.
- Across the Murray–Darling Basin, overuse and poor management of irrigation is responsible for some environmental problems such as soil salinity and loss of habitat for native flora and fauna.
- The Basin Plan and the MDB Agreement aim to limit the amount of use and make sure available water is distributed fairly.
- Irrigated horticulture is significant throughout the Basin with a continually evolving footprint – crop types have changed and continue to change based on market forces.
- It is the responsiblity of Basin state governments to determine how water can be used through licencing and allocation frameworks. The amount of water used is monitored.
Annual crops, permanent plantings and water used for livestock
It is up to individual irrigators to determine what they grow. Irrigators must determine what the water requirements are for their selected crops and how much water is required for different growth stages and the regions climatic conditions.
Permanent plantings are mostly grown in the southern Basin as they require access to a consistent supply of water. Lack of water affects the plants ability to produce higher quality produce and high yield. Some examples of permanent planting include:
- grapes
- almonds
- citrus trees.
In the northern Basin, irrigation still occurs but not on the same scale as in the southern Basin. Smaller-scale river systems tend to have less reliable year-to-year supply of water compared to major rivers like in the southern Basin, which impacts what can be grown and produced.
Mainly annual crops are grown in the northern Basin as they are grown on a yearly basis when water is available. These include crops such as:
- wheat
- cotton
- soybeans
- corn.
Considerable volumes of annual crops are also grown in the southern Basin, such as rice. Dairy farms in the Basin use irrigation water to supplement rainfall to produce pasture and fodder crops for livestock. Irrigation allows farmers to have a more stable and productive supply of pasture than possible when relying on highly variable seasonal rainfall.
Case study: Demand for irrigation water in the southern Basin
There have been significant changes in the demand for irrigation water in the Basin since the early 2000s. In the southern Basin genetic advances and movements in commodity prices have led to an increase in the demand for water for cotton and almonds and a decrease in demand for rice, dairy pastures and grapevines.
Water use of selected industries in the southern MDB, 2011–12 to 2017–18. ABARES
Almonds are highly suitable for production in the southern Basin because they:
- deliver high returns
- are not affected by fruit fly
- are durable
- have a long shelf-life compared to fruit and vegetables
- are permanent plantings.
Planted almonds increased from 3,500 hectares in 2000 to around 45,000 hectares in 2018, resulting in higher water demand in the southern Basin with:
- 53% of plantings in the Victorian Sunraysia (located in the Victorian Murray below the Barmah Choke)
- 24% in the New South Wales Riverina
- 20% in the South Australia Riverland.
The increase in almond production has also resulted in changes to the way that water has been delivered downstream.
Supply factors
Water prices and a variety of irrigated activities in the Basin are interconnected with the supply and demand for irrigation water. The main factors that have altered the supply of irrigation water in recent years include:
- water allocations – the total amount of water available for use in a particular year (determined by water in storage, rainfall and state water sharing plans)
- water for the environment – water rights purchased by or gifted to environmental agencies effectively reduce the supply of water allocations available for irrigation
- user carryover decisions – water holders can hold water in storage between years (rather than using or selling their allocation)
- trade rules – rules exist to limit the trading of water from one part of the system to another to ensure that water which is traded can be delivered. Examples include from upstream to downstream of the Barmah Choke, and from one valley to another (Inter-valley trade or IVT).
Changes in demand
The demand for irrigation water in the Basin has changed significantly over the past 20 years. The main factors influencing the demand for irrigation water in the Basin include:
- the profitability of irrigated activities – changes in water demand often arise from price shifts in the global market (for example demand for milk, cotton, rice)
- seasonal conditions – on-farm rainfall is a substitute for irrigation water, so when rainfall in irrigation areas is higher or lower than expected, the demand for irrigation water also changes
- investments in on-farm infrastructure (public or private) – including expansion or improving practices of irrigation areas, changes in the mix of irrigation activities or investments in on-farm water use efficiency all influence the demand for water allocations.
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