| Lake Argyle | |
|---|---|
| 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. | |
| Location | Western Australia |
| Primary inflows | Ord River, Bow River |
| Primary outflows | Ord River |
| Catchment area | 46,100 km² |
| Basin countries | Australia |
| Surface area | 703 km² |
| Water volume | 10,763,000 ML[1] |
| References | [1] |
Lake Argyle is Australia's second largest artificial lake by volume. It is part of the Ord River Irrigation Scheme and is located near the East Kimberley (Western Australia) town of Kununurra. The lake flooded large parts of the Shire of Wyndham-East Kimberley on the Kimberley Plateau about eighty kilometres inland from the Joseph Bonaparte Gulf, close to the border with the Northern Territory.
The primary inflow is the Ord River, while the Bow River and many other smaller creeks also flow into the dam. The lake is a DIWA-listed wetland.[2] as it is the largest lake in northern Australia and an excellent example of a man-made lake. Additionally Lake Argyle, along with Lake Kununurra, are recognised as a Ramsar protected wetlands and were listed in 1990 as Australian Site Number 32.[3]
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The construction of the Ord River Dam was completed in 1971 by the American Dravo Corporation.[4] The dam was officially opened the following year. The dam is 335 metres long, and 98 metres 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.[4]
In 1996, the spillway wall was raised by 6 metres, which doubled the dams capacity.[5] 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.[6]
Lake Argyle normally has a surface area of about 1,000 square kilometres. The storage capacity, to the top of the spillway is 10,763,000 megalitres. The lake filled to capacity in 1973, and the spillway flowed until 1984. Lake Argyle's usual storage volume is 5,797,000 megalitres,[7] making it the second largest reservoir in Australia (the combined Lake Gordon/Lake Pedder in Tasmania is the largest.) At maximum flood level, the lake would hold 35 million megalitres of water and cover a surface area of 2,072 square kilometres.[4]
Lake Argyle, together with Lake Kununurra, is part of the Ord River Irrigation Scheme. There are currently some 150 square kilometres of farmland under irrigation in the East Kimberly region. The original plan was for dam water to irrigate rice crop for export to China.[4] However these plans were scuttled as waterfowl, particularly magpie geese ate rice shoots quicker than they could be planted. Other crops are now grown, but Lake Argyle still remains Australia's most under-utilized lake.[4]
The damming of the Ord River has caused major changes to the environment. 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.[8]
The lake is now home to 26 species of native fish and a population of freshwater crocodiles currently estimated at some 25,000.[9] Fish species that are present in Lake Argyle include barramundi, southern saratoga, archer fish, forktail cat fish, mouth almighty, long tom, bony bream and sleepy cod.[4] While the official website states that only incidentally a saltwater crocodile is found,[10] other experts disagree.[11]
Cane toads reached the dam in late 2008, mostly via traveling along the Victoria Highway, with numbers rising significantly during the 2009 summer.[8]
The lake, with its surrounding mudflats and grasslands, has been identified by BirdLife International as an Important Bird Area (IBA) because it supports about 150,000 waterbirds. Birds for which the lake has global importance include Magpie Geese, Wandering Whistling-ducks, Green Pygmy-geese, Pacific Black Ducks, Hardheads, Black-necked Storks, Australian Bustards, White-headed Stilts, Red-capped Plovers, Oriental Plovers, Black-fronted Dotterels, Long-toed Stints and Sharp-tailed Sandpipers.[12]