Lake Argyle seen from space, August 1985. The main channel of the Ord River (dark, meandering feature) north of the lake is visible as it drains northward, eventually emptying into the Joseph Bonaparte Gulf. Low, folded mountains can be identified east and west of this river valley.
The primary inflow is the Ord River, while the Bow River and many other smaller creeks also flow into the dam.[4] The lake is a DIWA-listed wetland.[5] Lake Argyle and Lake Kununurra were listed in 1990 as Ramsar Convention protected wetlands.[6] Argyle mine was previously situated here from 1985 until November 2020 following several years of discoveries and yielded 865 million carats of diamonds.
History and construction
The construction of the Ord River Dam was completed in 1971 by Dravo Corporation.[7] The dam was officially opened the following year. The dam wall is 335 metres (1,099 ft) long, and 98 metres (322 ft) high. The earth-fill only dam wall at Lake Argyle is the most efficient dam in Australia in terms of the ratio of the size of the dam wall to the amount of water stored. The lake was named after the property it partly submerged, Argyle Downs.[7]
Ord River Dam post office opened on 1 March 1969 and closed on 15 November 1971 demonstrating the approximate duration of the construction camp.[8]
In 1996, the spillway wall was raised by 6 metres (20 ft), which doubled the dam's capacity.[9]Sediment flowing into the dam caused concerns in the mid-1990s that the dam's capacity could be dramatically reduced. By 2006 continual regeneration of the upper Ord catchment appeared to have reduced the amount of sediment inflow.[10]
Lake Argyle normally has a surface area of about 1,000 square kilometres (390 sq mi). The storage capacity, to the top of the spillway is 10,763 gigalitres (3.801×1011 cu ft). The lake filled to capacity in 1973, and the spillway flowed until 1984.[citation needed] Lake Argyle's usual storage volume is 5,797 gigalitres (2.047×1011 cu ft),[12] making it the largest reservoir in Australia. The combined Lake Gordon/Lake Pedder system in Tasmania is larger but is two dams connected by a canal. At maximum flood level, Lake Argyle would hold 35,000 gigalitres (1.2×1012 cu ft) of water and cover a surface area of 2,072 square kilometres (800 sq mi).[7]
Lake Argyle, together with Lake Kununurra, is part of the Ord River Irrigation Scheme. There are currently some 150 square kilometres (58 sq mi) of farmland under irrigation in the East Kimberly region. The original plan was for dam water to irrigate rice crop for export to China.[7] However these plans were scuppered as waterfowl, particularly magpie geese ate rice shoots more quickly than they could be planted. Other crops are now grown, but Lake Argyle still remains Australia's most under-utilised lake.[7]
Flora and fauna
View from downstream viewing the Ord River after it leaves Lake Argyle
The damming of the Ord River has caused major changes to the environment.[citation needed] Flows to the Ord River have been severely reduced. Within Lake Argyle itself a thriving new eco-system has developed. The lake is recognised as an important wetland area under the Ramsar Convention; with Lake Kununurra it forms the Lakes Argyle and Kununurra Ramsar Site.[13]
Cane toads reached the dam in late 2008, mostly via traveling along the Victoria Highway, with numbers rising significantly during the 2009 summer.[13]
Some threats identified by the IBA include invasive weed and animal species, such as the cane toad, as well as agricultural uses, free range cattle and feralungulates that may be over-grazing in the shallow areas around the lake. The IBA recommends that a fence be installed in the important shallows in the south and east to prevent all ungulates from entering those lake areas.[17]
^Public Works Department (1982). Lake Argyle(PDF) (Map). 1:30,000. Department of Transport, Government of Western Australia. Archived(PDF) from the original on 26 March 2022. Retrieved 16 October 2022.
^ abcdefHarrison, Rod; Ernie James; Chris Sully; Bill Classon; Joy Eckermann (2008). Queensland Dams. Bayswater, Victoria: Australian Fishing Network. pp. 60–61. ISBN978-1-86513-134-4.
^Premier Postal History, Post Office List, retrieved 21 January 2016