Irrigation in Australia

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Irrigation in Australia is a widespread practice to supplement low rainfall levels in Australia with water from other sources to assist in the production of crops or pasture. As the driest inhabited continent, irrigation is required in many areas for production of crops for domestic and export use.^[1] However, overuse or poor management of irrigation is held responsible by some for environmental problems such as soil salinity and loss of habitat for native flora and fauna.^[2]

Irrigation differs from dryland farming (farming relying on rainfall) in Australia in its level of intensity and production.

Contents 1 Water sources 2 History 3 Production 3.1 Cotton 3.2 Rice 3.3 Grapes 4 Water trading 5 Methods 6 Environment 7 References

[edit] Water sources

In general, water for irrigation comes from two main sources, river systems and underground aquifers. Major river systems used for irrigation in Australia include the Murray-Darling system, the Ord River in the Kimberley region of Western Australia and many rivers along the east coast of Australia. A major source of ground water in Australia is the Great Artesian Basin.

Although the Murray-Darling Basin receives only 6% of Australia's annual rainfall, over 70% of Australia's irrigation resources are concentrated there. It contains 42% of the nation's farmland and produces 40% of the nation's food.

[edit] History

The first schemes for irrigation commenced in the latter half of the nineteenth century. Goulburn Weir, constructed from 1887 to 1891, was the first major diversion structure built for irrigation development in Australia.^[3]

A major drought in Victoria from 1877 to 1884 prompted Alfred Deakin, then a minister in the State Government and chairman of a Royal Commission on water supply to visit the irrigation areas of California. There he met George and William Chaffey. In 1886 George Chaffey came to Australia and selected a derelict sheep station at Mildura as the site for his first irrigation settlement signing an agreement with the Victorian government to spend at least £300,000 on permanent improvements at Mildura in the next twenty years. Also in 1886/87, the Chaffey brothers were invited by John Downer, the Premier of South Australia, to commence a settlement at Renmark, South Australia.^[4]

The Dethridge wheel, used for measuring flow of water delivered to individual farms was developed in 1910.^[5]

Irrigation in the Murrumbidgee valley began in with the irrigation experiments of agricultural pioneer, Samuel McCaughey at North Yanco station in 1900. This private scheme involved the construction of around 320 kilometres of channels to irrigate about 162 square kilometres of land.^[6] McCaughey's success appeared to have encouraged the New South Wales government to commence large scale irrigation. This process began in 1906 with the proclamation of the of the Barren Jack and Murrumbidgee Canals Construction Act 1906. Burrinjuck Dam on the Murrumbidgee River near Tumut was commenced in 1907, work commenced on the channels and the first farms were established soon after.^[7]

In Western Australia the state's first controlled irrigation scheme, the Harvey Irrigation Scheme, was officially started in 1916. It was further developed during the latter part of the 1930s depression to take unemployed workers to dig and build the extensive irrigation channels in the district.^[8]

[edit] Production

Water consumption by the agriculture industry was 12,191 gigalitres (GL) in 2004-05, accounting for 65% of total water consumption in Australia during that period. Irrigation/rural water providers were the main suppliers of distributed water in 2004-05 accounting for 6,637 GL or 59% of Australia's total distributed water supply.^[9]

The total gross value of irrigated agricultural production in 2004-05 was $AUD 9,076 million compared to $AUD 9,618 million in 2000-01.^[9] The gross value of irrigated agricultural production represents around a quarter (23%) of the gross value of agricultural commodities produced in Australia in 2004-05, on less than 1% of agricultural land.^[10]

Common crops produced using irrigation include rice, cotton, canola, sugar, various fruits and other tree crops and pasture, hay and grain for use in beef and dairy production.

Gross value of irrigated agricultural production in $AUDM [9]	2000-01	2004-05
Dairy farming	1 499	1 632
Vegetables	1 817	1 761
Sugar	284	477
Fruit	1 590	1 777
Grapes	1 355	1 314
Cotton	1 222	908
Rice	350	102
Nurseries, cut flowers & turf	763	737
Livestock, pasture, grains & other	737	367
Total	9 618	9 076

[edit] Cotton

Major cotton growing areas in Australia are:

• New South Wales - Mungindi, Gwydir River, Walgett, Bourke, the Lower and Upper Namoi River, Macquarie River, Menindee, Lachlan River and Murrumbidgee River
• Queensland - Central Highlands, Dawson Valley, Biloela, Darling Downs, Dirranbandi, St George, Macintyre Valley^[11]

In 2001/02 crop size was 420,170 hectares producing 3,041,000 bales . Estimates for 2006/07 were for 142,032 hectares producing cotton, a 66% reduction, producing a forecast crop of 1,171,765 bales, a 61% reduction.^[11] The total gross value of irrigated agricultural production in the cotton industry in 2004-05 was $AUD 908 million compared to $AUD 1,222 million in 2000-01. While demand skyrocketed, actual water use by the cotton industry fell by 37% between 2000/01 and 2004/05, due mainly to drought.^[9][12] The cotton industry used 2,896 GL in 2000/01 and 1,822 GL in 2004/05.^[10]

[edit] Rice

Irrigated areas in the Riverina produces the vast majority of rice grown in Australia, particularly in the Murrumbidgee Irrigation Area (MIA), but also the Murray Irrigation Area around Finley, Coleambally and Deniliquin areas.^[13]

Today, more than one million tonnes of Australian rice is produced each year and exported to over 70 countries, generating $ AUD 500 million in export income and supporting 63 towns in the Riverina and northern Victoria.^[14] Major rice mills are located in Leeton, Coleambally and the largest rice mill in the southern hemisphere in Deniliquin.^[15]

The total gross value of irrigated agricultural production in the rice industry in 2004-05 was $AUD 102 million compared to $AUD 350 million in 2000-01. Water use by the rice industry fell between 2000/01 and 2004/05, due mainly to smaller planted areas during the drought; the rice industry used 2,223 GL in 2000/01 and 631 GL in 2004/05.^{[10] [9]}

[edit] Grapes

Wine, raisin and table grapes are grown commercially in all States and Territories and in most cases through irrigation processes that pump water directly to individual vines. Grape production is the fifth largest fruit industry in Australia. Of that production wine grape production at over 1 million tonnes per annum is almost 9 times the production of dried grapes and 14 times the production of table grapes.

A comparison with other grape producing countries throughout the world shows that Australia was the fourteenth largest producer of grapes in 1997.

Towards sustaining that production much of Australia’s viticulture is located in irrigable areas where water supply is reliable and well managed, with many new vineyards relying upon the availability of water pumped from rivers and streams.

Major grape growing areas of Australia are:

• Western Australia – Carnarvon, Swan Valley, and Margaret River, Western Australia
• Northern Territory – Ti Tree
• South Australia – Clare Valley, Barossa Valley, the Riverland, the Adelaide Hills and the South East area of the State
• Queensland – Mareeba, Mareeba, Charters Towers, Mundubbera, Stanthorpe, Emerald, and St George
• New South Wales – Hunter Valley, New South Wales and Riverina
• Victoria – Sunraysia, Swan Hill and Yarra Valley
• Tasmania – Launceston and Hobart ^[16]

[edit] Water trading

In Australia, all rights to use and control water are vested in the state. Users are then issued various conditional entitlements to use water and some of these entitlements can, in limited circumstances, be traded.

Entitlements vary state by state and according to the use, source, legal form, level of devolution, security and transferability among others. There has been a move across all states in recent years to move from older forms of water entitlement to more secure and transferable entitlements. Key parts of this move has been the separation of water entitlements from ties to particular parcels of land and the specification of entitlements with specific volumes and reliability.

Where an entitlement is able to be traded, the transaction may take several forms including temporary transfer of a seasonal water assignment, a permanent transfer of all or part of a water entitlement or a lease over a set period of years. All transfers require approval from the various regulatory bodies to ensure it complies with trading rules designed to meet environmental and in some cases socio-economic objectives. Such rules may include approving trades only within a set zone or the exchange rate of trades between zones to reflect water losses in delivery or differences in reliability.^[17]

[edit] Methods

Irrigation methods in Australia have improved over many years allowing for more efficient production per megalitre of water used. Current methods include systems such as centre pivot irrigation, impact (knocker) sprinklers, butterfly sprinklers, drip and flood irrigation.

Centre pivot irrigation is often used for grass and fodder crops where the water can be distributed over a considerable period of time. In other crops where moisture stress is a complex concern, for example during the growing of cauliflower, water is required to be distributed quickly two or three specific times per day at a rate of about 140% the evaporation replacement rate and for this impact sprinklers set every 12 square metres or butterfly sprinklers set every 6 square metres are required.^[18] Drip sprinklers can be used on many spaced planting locations but typically will be found as gravity fed systems on vineyards.

Earthworks such as laser levelling are often employed to improve water use efficiency and even distribution of water.

[edit] Environment

Overuse and poor irrigation practices have led to increased salt content in the soil, reducing the productivity of the land. Irrigation salinity is caused by water soaking through the soil level adding to the ground water below. This causes the water table to rise, bringing dissolved salts to the surface. As the irrigated area dries, the salt remains.^[2] At Wakool in the Riverina region of New South Wales, irrigation salinity is mitigated through a salt interception scheme that pumps saline ground water into evaporation basins, protecting approximately 50,000 hectares of farmland in the area from high water tables and salinity. The subsequent salt has various uses including as an animal feed supplement. The program has returned to production over 2,000 hectares of previously barren farmland and encouraged the regeneration of native eucalypts.^[19]

[edit] References