Lake Argyle

The construction of the Ord River Dam was completed in 1971 by Dravo Corporation. In 1996, the spillway wall was raised by , which doubled the dam's capacity. 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. The dam received a Historic Engineering Marker from Engineers Australia as part of its Engineering Heritage Recognition Program. ==Geography==

Lake Argyle normally has a surface area of about . The storage capacity, to the top of the spillway is . The lake filled to capacity in 1973, and the spillway flowed until 1984. Lake Argyle's usual storage volume is , 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 of water and cover a surface area of . Higher areas have become permanent islands within the lake's area. ==Irrigation==

Lake Argyle, together with Lake Kununurra, is part of the Ord River Irrigation Scheme. There are currently some of farmland under irrigation in the East Kimberly region. The original plan was for dam water to irrigate rice crop for export to China. 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. ==Flora and fauna==

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. The lake is now home to 26 species of native fish and a population of freshwater crocodiles currently estimated at some 25,000. 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. other experts disagree. Cane toads reached the dam in late 2008, mostly via traveling along the Victoria Highway, with numbers rising significantly during the 2009 summer. Common larger-bodied bird species found at the lake include the Australian pelican, black swan, eastern great egret, royal spoonbill, osprey and wedge-tailed eagle. Common smaller-bodied bird species include the spinifex pigeon, peaceful dove, common sandpiper, white-winged tern and budgerigar, while mid-sized bird species include the red-winged parrot, blue-winged kookaburra and barking owl. 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 feral ungulates 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. ==See also==