Developed in 1962 with the construction of the Diversion Dam which led to the formation of Lake Kununurra, the Ord River Irrigation Area (ORIA) comprises approximately 13,000ha of irrigable soils. The first stage of the project was completed in 1973 with the building of the Ord Dam that created Lake Argyle and ensured water supply for an irrigation project of more than 50,000 hectares. See Map “Location of the Ord River Scheme" (1.3Mb)
Designed in the late 1950s, the irrigation system was constructed to take advantage of what, at the time, was thought to be abundant supplies of water to flush the system, ensuring no build up of farming residues within the irrigation area. A network of channels fed, by a single main channel, deliver water to farms and an extensive drainage system, including some very large trunk drains, removes excess irrigation and wet season flood water from the farms. Hillside drains are located to protect the internal channels and drains from large wet season overland flows. (See MAP “Irrigation Infrastructure of Ivanhoe and Packsaddle Plains.”).
Stage 1 of the ORIA consists of a little more than 10,000 hectares of land on the Ivanhoe Plain, being mainly cracking clay soils of the Cununurra series. Areas between the main plain and river are sandier soils of the river levee bank and the Pago and Cockatoo sands between the plain and nearby hill systems. Some areas of very heavy Aquitane clay soils are located on the flatter margins of the main Ivanhoe Plain. A further 2,000 hectares of land on the Packsaddle Plain includes most of the soil types found on Ivanhoe Plain as well as significant areas of medium textured red clay soils of the Packsaddle type. For details of the soils of the ORIA see MAP “ Soils and Cadastre of the Ivanhoe and Packsaddle Plains.”
More than 60% of the ORIA is underlain with sand and gravel beds of the old (Palaeochannel) bed of the Ord River. These sand and gravel beds conduct water well and form extensive interconnected aquifers beneath the irrigated areas of both Ivanhoe and Packsaddle plains. The water in these aquifers is generally low in electrical conductivity (indicating low levels of dissolved salts), with a few localised exceptions. (See map 3).
History
Following extensive cropping trials throughout the 1940s and 1950s, the initial irrigation farming system was based on cropping cotton over the wet season. Farms of about 240 hectares were released in the early 1960s. Most farms were made up of three irrigation bays of approximately 80 hectares. Farms were serviced with irrigation supply points and drainage outlets as required and conditions were placed on the development of the farms to encourage rapid development of the irrigation land.
From 1962 to 1974 cotton was the mainstay of the irrigation area, although many crops were tried both experimentally and on farm. The area under crop during this period peaked at a little more than 7,000 hectares. With the closure of the cotton industry in 1974 a period of restructuring continued throughout the 1970s to mid 1980s. During these years the area under crop declined to less than 3,500 hectares and a wide range of crops was tested experimentally and on farm for their suitability. Many of the crops that showed early promise (rice, grain sorghum, peanuts, hay, millet, etc) later failed because of poor yields, poor quality or poor prices.
Towards the end of the 1980s horticulture was introduced and crops that could generate large profits became the norm. Cucurbit crops grown for the domestic market out of season with the southern temperate supplies, and bananas that were grown for the Perth market enabled a new breed of farmers to become established. Profits from these high value crops enabled other crops such as sugarcane to be grown and resulted in all the available irrigation land being brought into production. By 1998 more than 12,000 hectares of land were harvested and the range of crops included: -
sugarcane, leucaena pastures for cattle, sandalwood, hybrid seed, culinary grains such as chickpea and berlotti beans, maize, sunflowers, horticulture crops such as rockmelon, watermelon, pumpkin, bananas, mangoes and a wide range of small crops including zucchini, squash, onions, tomatoes, beans. Significant areas of trial cotton (up to 900 ha) were grown as part of a program to develop counter-cyclical production based on integrated pest management strategies.
The shortage of new farming land led to proposals to develop the second stage of the ORIA including more than 30,000 hectares on the Weber, Knox Creek and Keep River plains to the north and east of Stage 1. This M2 area is currently subject to extensive study by a consortium made up of Wesfarmers, Marubeni Corporation and the WA Water Corporation with the aim of establishing a large-scale sugar industry. Additional areas north-west of Stage 1 planned for development include more than 10,000 hectares of the Carlton Plain and Mantinea areas of the lower Ord River.
There are more than 100 active farms in the ORIA, however more than half of these rely on off-farm income and are small. Approximately 40 are large-scale irrigation farms on which a range of crops is grown. Of these farms most are used to grow a diversity of crops in any one cropping year. The large farms are irrigated using surface flow irrigation in furrows, while more intensive tree crops, small crops and bananas are grown on the sandier soils and are irrigated using a range of sprinkler and tape systems. There has been some limited testing of trickle tape on broad-acre crops grown on the cracking