Longest rivers

The lengths of the 10 longest rivers in Australia were re-calculated in September 2008 by Geoscience Australia using data from the National Topographic Database. The calculations confirmed that Australia's longest single river is the River Murray at 2508 kilometres. However, if the longest tributaries of the Darling River, the Culgoa, Balonne and Condamine, are taken into account its total length increases to 2740 kilometres, making it Australia's longest waterway.

The National Topographic Database is a nationally consistent dataset containing a range of topographic features, such as relief and drainage, which has been captured and maintained at a scale of 1:250 000 for the whole of Australia. Use of the database to digitally calculate the longest rivers has resulted in more precise estimates than those available previously. River names in the database are acquired from the place names authorities in each Australian State and Territory or other authoritative sources such as the Murray-Darling Basin Authority.

The use of official names only for the latest calculations has resulted in significant differences from earlier calculations. For example, the 1545 kilometre length of the Darling River is based solely on those river sections called Darling River in the database. Separately named tributaries have not been included because they are not strictly part of the officially named Darling River. As a result, the Darling River is now apparently shorter than previously stated. However, if its major tributaries, the Culgoa, Balonne and Condamine, are included, its total length increases to 2740 kilometres.

It is important to note that the new lengths are still only approximations, because they have been measured from a cartographic representation of the rivers, rather than the actual rivers.

Longest river by State and Territory

Although the River Murray forms much of the border separating New South Wales and Victoria, it is not Victoria's longest river because the New South Wales border is delineated by the river's southern bank rather than by the middle of the river. The only section of the river considered within Victoria is a stretch of approximately 11 kilometres where it separates Victoria and South Australia. At this point, the middle of the river forms the border.

Longest continuous river system

The Murray-Darling catchment also contains Australia's longest continuous river system. This is established by measuring downstream from the confluence of the River Murray and the Darling River, plus the Darling itself, together with some of the Darling's tributaries to create an overall length of 3672 kilometres. With connected flow through Queensland, New South Wales and South Australia, this system drains a major portion of the interior lowlands of eastern Australia. Its total length is just over half that of the Nile River in continental Africa, which at 6695 kilometres is considered to be the world's longest river.

From its headwaters in Queensland down to the River Murray mouth near Goolwa in South Australia, the Murray-Darling system has been measured using the following rivers to establish its approximate overall length: