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|Ord River Irrigation Scheme|
The Ord River in the east Kimberley of Western Australia has a catchment area of 64,000 square kilometres. The river is about 650 kilometres long draining into Cambridge Gulf near Wyndham with a mean stream flow at the river mouth of 4,500 gigalitres a year. The region has a semi-arid to arid monsoonal climate with two seasons: a warm, dry season and a hot, wet season from November to April. Most rain during the wet season comes from monsoonal depressions and tropical cyclones; rainfall can be infrequent for the rest of the year and consecutive dry months are common. Wet season rivers can be raging torrents sweeping away vegetation and scouring river bed and banks. The same river may be a series of drying waterholes in the dry season; before it was regulated the Ord River stopped flowing for two or three months each year between June and october. Average annual rainfall at Kununurra is 776 millimetres with 90% falling in the wet season. Net evaporation rates are high, approximately 2,000 millimetres a year; evaporation exceeds precipitation in most months.
The agricultural possibilities of the Ord River valley were recognised at least as early as 1920 but this potential could only be realised if the water was available in the dry season. The Ord River flowing through the fertile land was either flooding in the Wet Season or too low to provide water for agriculture in the Dry Season. The key to developing the region was to use the waters of the Ord River.
The Western Australian government established a small experimental station in 1941; this was closed in 1945 when the Kimberley Research Station, jointly operated by the CSIRO and the Western Australian Department of Agriculture, opened on the Ivanhoe Plain. The Research Station grew crops of rice, cotton, safflower, flax and sugarcane with results encouraging enough for the Western Australian government to develop an irrigation scheme on the Ord River. Commercial farming began in 1963.
Kununurra town was built near the dam as the residential and service centre for the scheme.
The next stage in the project was to build a large dam further up the Ord River where it enters the Carr-Boyd Range about 50 kilometres south of Kununurra. This Ord River Dam was completed in 1970-72 and officially opened in June 1972. The 99 metre high dam is 341 metres long and made of rock fill around a core of impervious clay.
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A 36 MW hydro electric power station was constructed in 1995/96 at the Ord River Dam. The power station is connected via 132 Kv transmission lines with Kununurra and the Argyle diamond mine.
Lake Argyle, the largest body of fresh water in mainland Australia, is about 62.5 km long and 45 km wide, its total area covering 745 km2 and containing 96 islands. It holds 10,760 million cubic metres (triple that when in flood), and its total storage capacity is 18 times that of Sydney Harbour. Such comparisons often made with the volume or surface area of Sydney Harbour seem meaningless when so few people, even Sydney residents, comprehend the surface area of the Harbour. A trip across Lake Argyle in a high-speed powerboat is quite sufficient to show that the dam retains an immense amount of fresh water.
Annual inflow into Lake Argyle from tributaries is 3,940 gigalitres and increase from rain falling on the lake surface is 640 gigalitres taking total average inflow to 4,480 gigalitres each year. Some water from the lake is taken for the Argyle Diamond Mine and for the Lake Argyle Tourist Village. Direct evaporation from the lake surface in the hot dry season is a significant factor (1,750 gigalitres) in water use planning. A further 890 gigalitres a year is lost as overflow during the wet season; 1,950 gigalitres are released from the dam of which about 300 gigalitres is used for irrigation, most of the rest flows out to sea. For planning purposes the term "net annual inflow" is used; this is inflow from stream and rainfall less evaporation and is 2730 gigalitres a year.
Water is released from the Ord River Dam to meet hydro power requirements, to meet boating demands below the Dam and to maintain the water level in Lake Kununurra within a narrow range mainly to meet the irrigation needs of the Packsaddle Plain and Ivanhoe Plains but also to maintain foreshore levels. The Lake Argyle spillway is separate from the dam; water from the spillway joins Stonewall Creek and flows into the Ord River below Carlton Gorge.
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Total area under cultivation declined after cotton growing stopped. By 1980 there were 4,800 hectares under cultivation (about ten per cent of the possible irrigated area) and the area declined further until,in 1990-91 there were 4,300 hectares being cultivated. Then expansion resumed as new crops were introduced; the area under
cultivation doubled over four years so there were 9,816 hectares under cultivation by 1994-5.
Sugar was one of the crops associated with this expansion. Sugar had been tested at the Kimberley Research Station in the early 1950s and again in the mid-1960s but did not proceed to production. In the mid-1970s further trials were conducted and a pilot farm was later established; the suitability of the area for sugar production was confirmed but commercial development was delayed until a sugar mill was established as a joint venture with CSR. Successful sugar cane harvesting resulted in the production of raw sugar late in 1995. Sugar from the Ord River is trucked to Wyndham where it is exported by sea to a Korean-owned food manufacturing plant in Surabaya, Indonesia.
The range of crops harvested includes chickpeas, sorghum seed, melons, pumpkins, mangoes, bananas, citrus, irrigated pasture, tropical forests and sugar cane. Sugar production accounts for approximately one third, by area, of the cultivated land in the Ord River Irrigation Area. In 2004/05 the gross value of production was estimated at $53.6 million. The highest value crops in 2004/05 were melons ($12.2 million), sugar ($16.1 million), mangoes ($1.9 million), hybrid seeds ($3.6 million), pumpkins ($3.6 million) and bananas ($0.5 million). Fruit and vegetables are sold to domestic markets and are trucked to all capital cities. The practice of sending produce by truck to markets in the south of Western Australia and to the eastern seaboard has emphasised the need for all-weather roads (and bridges) capable of handling the large trucks carrying this freight.
A couple of unusual crops, boab trees and sandalwood trees, are being developed. Sandalwood is a crop increasingly being grown in the Ord Scheme. The first crops were planted in 1997-98. Indian Sandalwood is usually supplied from India but availability of the Indian product is in long-term decline for a variety of reasons so there is a growing shortage of this valuable timber. A price in excess of A$100,000 per tonne has been quoted. The Ord River scheme contains the largest commercial Indian Sandalwood plantations in the world. Another novel crop is boab trees; boab seedlings are harvested after growing for only a short time and while they are still little more than seedlings and sold for eating raw or in a stir fry.
Cotton growing ceased in the 1970s mainly because the cotton bollworm could not be controlled but the region was regarded as otherwise suitable for cotton and a newly available genetically modified version was grown on 250 hectares in 1996-97. These trials were so successful that a pilot cotton gin was commissioned in 1998 to process the output. During 2004 and 2005 further trials were carried out with genetically modified cotton grown to investigate the feasibility of reintroducing cotton into the Ord River Irrigation Area. The trial cotton was grown during the dry season (March to October) to avoid the main insect pests.
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Using genetically modified varieties and careful pest management, insecticide usage was reduced to less than five sprays per season with acceptable fibre quality and yields similar to the Australian average. The new growing season is very tight and has to fit between the ground drying out enough to permit farm machinery to move (in March) and the onset of the rains in October which make harvesting difficult.
Genetically modified crops are prohibited in Western Australia except for research crops in the Ord River Irrigation Area with specific approval required before the crop is planted. Unless Western Australia changes this policy, cotton is unlikely to be re-introduced into the Western Australian part of the Ord River Irrigation Area. But Stage Two of the scheme includes more irrigated land in Western Australia and in adjacent parts of the Northern Territory. Trials of genetically modified cotton have been held in the Northern Territory near Katherine.
Stage Two includes some extension of land in Stage One but mainly involves development of new irrigated land at the Weaber, Knox Creek and Keep River Plains east of the river to be supplied with water from Lake Kununurra. Additional irrigated land downstream of Lake Kununurra will be developed at Mantinea Flats, Carlton Plain and the West Bank of the Ord River downstream of the Dunham River. The timetable for Stage Two is unclear but a positive step was the signing of a Memorandum of Understanding between the Western Australian government and the Miriuwung Gajerrong traditional owners on 12 November 2004. This document will serve as the basis for further negotiation concerning 65,000 hectares of land in Stage Two including land in Kununurra township. Six new conservation parks have been included in Stage Two. If and when it is developed Stage Two will represent a substantial expansion of activity in the Ord Scheme and will be another step in the sometimes erratic development of the Scheme.
Despite the development and sometimes optimism, the Ord River Irrigation Scheme remains something of an enigma. There is a vast volume of fresh water available but finding the best way to use this fresh water in a tropical location far from Australian population centres remains a problem.
¶ "Ord River Allocation Planning - Environmental Valuations, Past, Present and Future" by Kerry Trayler and Russell King at the conference on Globalisation and Water Resources Management: The Changing Value of Water at University of Dundee, 6 to 8 August 2001.
¶ "16. Developer profile: Jim Hughes, Ord River Irrigation Area, Western Australia" in The Australian New Crops Newsletter, Issue No 6, July 1996.
¶ Application for Approval of GM Cotton Trials Ord River Irrigation Area.
¶ "Assessing the feasibility of GM cotton in the Ord River Irrigation Area: tillage systems for late wet season sowing." by Stephen Yeates, John Moulden, Gae Plunkett, and Geoff Strickland. from Proceedings of the Australian Agronomy Conference, 2006.
¶ "Major Land Agreement for East Kimberly". Press Release by WA Government and Kimberley Land Council, 16 November 2004.
¶ "TB313. Insect Dynamics of the Cotton Ecosystem in the Northern Territory" at Katherine Research Station (2003 season)
¶ "The Role of IPM in Sustainable Cotton Farming Systems in the NT" at Katherine Research Station (2000 to 2005 seasons) - part of Technical Annual Report 2005-06, TB325.
¶ "Ord River Irrigation Scheme" on the Kimberley Development Commission website at http://www.kdc.wa.gov.au/kimberley/tk_ord.asp